FA152485ISSN 0335-3931
NF P 94-262
July 2012
Classification index: P 94-262
ICS: 91.010.30; 93.020
Justification of geotechnical structures
National Enforcement Standards Eurocode 7 deep foundations E: Justification of geotechnical work - National standards applied for the implementation of Eurocode 7 - Deep Foundations D: Rechtfertigung von geotechnischen Bauwerken - Normen für die Anwendung von national Eurocode 7 - Tiefgründungen
F rench renc h s tanda tandard rd approved approved vr
e
d e
by decision of the Director General of AFNOR June 20, 2012 to take effect on 20 July 2012. s e R ts h gi R ll A
Correspondence At the date of publication of this document, there is no European work 2
International or on the same subject.
1 0 2 R O
©
A
F
N
This document defines the terminology and notations used. It describes the behavior of deep foundations and provides the justification rules for the calculation of deep foundation ultimate limit state and serviceability limit states.
s
nalysi
descriptors
Technical International Thesaurus: geotechnical,
foundation depth, soil foundation pile, definition, property, ground, material calculation, material strength, compressive stress, allowable stress, limit, maximum load, tensile strength, stability, movement, deformation verification.
modifications corrections Published and distributed by the French Association of Normalization (AFNOR) - 11, St. Francis Pressensé - 93571 La Plaine Saint-Denis Cedex Such. : + 33 (0) 1 41 62 80 00 - Fax: + 33 (0) 1 49 17 90 00 -www.afnor.org
© AFNORAFNOR 20121
st drawing 2012-07-P
Jusitifcations Geotechnical Works
BNSR CNJOG
Members of the Standards Committee Chairman: Mr Vezole
Secretariat: M BURLON - IFSTTAR M
BAGUELIN
Fondasol
M M
Berthelot BUSTAMANTE
BUREAU VERITAS / COPREC MB FOUNDATIONS
M
Carpinteiro
SOCOTEC / COPREC
M
DAUBILLY
FNTP
M
DELAHOUSSE
ARCELOR
M
Delmas
CNAM
M
DURAND
FUGRO / CNREG
M
FRANK
IFSTTAR ENPC CERMES / TC 250
M M
GAUTHEY Glandy
SPIE FOUNDATIONS Soletanche-Bachy-PILES
M
GRATIER
THYSSENKRUPP
M
GUERPILLON
SCETAUROUTE
MRS
GUIZIOU
CETMEF
M
HABERT
CETE NORD-PICARDIE - AML Lille
MRS M
GREAT THE Delliou
CETE NORD-PICARDIE - AML Lille Ischebeck FRANCE
M
Legendre
Soletanche Bachy / CNETG
M
MAGNAN
IFSTTAR / NSCC
MRS
MAUREL
CETEs Ile de France
M
MIRAILLET
EDF TEGG
M
MOUSSARD
SNCF
MRS
OSMANI
Eiffage
M M
PILLARD PINÇON
UMGO BNTEC
MRS
Pineau
AFNOR
M
Plumelle
CONSULTANT
M
RAYNAUD
PARIS AIRPORTS
M
ROCK-LACOSTE
IFSTTAR
M
Saliba
SETRA
M
SCHMITT
Soletanche Bachy
M M
SIMON THONIER
TERRASOL / USG EGF-BTP
M
VALEM
FFB
M
VETROFF
FRANKI FOUNDATION
M
VOLCKE
FRANKI FOUNDATION / SOFFONS
Participants as experts: The list of persons who participated in the various working groups to establish the V1 version of the document is indicated in the foreword.
Jusitifcations Geotechnical Works
BNSR CNJOG
Members of the Standards Committee Chairman: Mr Vezole
Secretariat: M BURLON - IFSTTAR M
BAGUELIN
Fondasol
M M
Berthelot BUSTAMANTE
BUREAU VERITAS / COPREC MB FOUNDATIONS
M
Carpinteiro
SOCOTEC / COPREC
M
DAUBILLY
FNTP
M
DELAHOUSSE
ARCELOR
M
Delmas
CNAM
M
DURAND
FUGRO / CNREG
M
FRANK
IFSTTAR ENPC CERMES / TC 250
M M
GAUTHEY Glandy
SPIE FOUNDATIONS Soletanche-Bachy-PILES
M
GRATIER
THYSSENKRUPP
M
GUERPILLON
SCETAUROUTE
MRS
GUIZIOU
CETMEF
M
HABERT
CETE NORD-PICARDIE - AML Lille
MRS M
GREAT THE Delliou
CETE NORD-PICARDIE - AML Lille Ischebeck FRANCE
M
Legendre
Soletanche Bachy / CNETG
M
MAGNAN
IFSTTAR / NSCC
MRS
MAUREL
CETEs Ile de France
M
MIRAILLET
EDF TEGG
M
MOUSSARD
SNCF
MRS
OSMANI
Eiffage
M M
PILLARD PINÇON
UMGO BNTEC
MRS
Pineau
AFNOR
M
Plumelle
CONSULTANT
M
RAYNAUD
PARIS AIRPORTS
M
ROCK-LACOSTE
IFSTTAR
M
Saliba
SETRA
M
SCHMITT
Soletanche Bachy
M M
SIMON THONIER
TERRASOL / USG EGF-BTP
M
VALEM
FFB
M
VETROFF
FRANKI FOUNDATION
M
VOLCKE
FRANKI FOUNDATION / SOFFONS
Participants as experts: The list of persons who participated in the various working groups to establish the V1 version of the document is indicated in the foreword.
NF P 94-262
Summary
Page
Preliminary propos7 ........................................................................................................................ ........................................................................................................................ 1
Field of application9 ............................................................................... .............................................................................................................. ...............................
2
normatives15 references ...................................................................................................... ......................................................................................................
3 Terms, definitions and symboles17 .................................................................................... .................................................................................... 3.1 Terms and définitions17 ........................................................................... ....................................................................................................... ............................ 3.2 Symbols and indices18 ............................................................................. ......................................................................................................... ............................ 4 Behavior profondes24 foundations ..................................................................... ..................................................................................... ................ 4.1 Généralités24 ............................................................................. ......................................................................................................................... ............................................ 4.2 Behavior under load axiale24 ............................................................................... ............................................................................................... ................ 4.3 Transversales26 behavior under stress .......................................................................... ............................................................................. ... 4.4 Mechanisms ruin or disorders inacceptables27 ................................................................ ................................................................ 5 Actions and data géométriques30 ....................................................................... ....................................................................................... ................ 5.1 Actions30 ...................................................................... ............................................................................................................................... ......................................................... 5.2 geometric data 35 ...................................................................... .................................................................................................................. ............................................ 6 Properties land and matériaux38 ......................................................................... ......................................................................................... ................ 6.1 General principles 38 ............................................................................................................ 6.2 up land 38 ...................................................................... ............................................................................................................................... ......................................................... 6.3 Materials reported 39 ................................................................................ ............................................................................................................ ............................ 6.4 Constituent materials of profondes40 foundations ........................................................... 7 Situations of calculation, loads and combinations of actions44 ..................................... 7.1 Situations calcul44 .................................................................... ................................................................................................................ ............................................ 7.2 Combination of actions45 ........................................................................ .................................................................................................... ............................ 7.3 Provisions for determining deep foundations 47 .............................................................. 8 General rules for justification of profondes52 foundations.............................................. foundations.............................................. 8.1 Généralités52 ............................................................................. ......................................................................................................................... ............................................ 8.2 ultimes54 limit states ................................................................................ ............................................................................................................ ............................ 8.3 States limits service55 .............................................................................. .......................................................................................................... ............................ 8.4 Models calcul56 ..................................................................................................................... ..................................................................................................................... 8.5 Deep foundation isolated subjected to stress axial57 ...................................................... 8.6 Deep foundation isolated in an attempt transversal60 ..................................................... 8.7 Behavior of a group of foundations profondes61.............................................................. 8.8 Consideration of overall displacements of the ground 63 ................................................ 8.9 stakes tests réaliser65 .............................................................................. .......................................................................................................... ............................ 9 State-limit portance68 ........................................................................................................... ........................................................................................................... 9.1 General principle 68 .............................................................................................................. 9.2 Bearing a deep foundation isolée68 .................................................................... .................................................................................... ................ 9.3 Bearing a group of profondes72 foundations .................................................................... 10 State-limit traction74 ............................................................................................................. ............................................................................................................. 10.1 General principle 74 .............................................................................................................. 10.2 tensile strength of a deep foundation isolated 74 ............................................................. 10.3 tensile strength of a group of deep foundations 77 .......................................................... 11 Resistance to transverse loads 82 ...................................................................................... 11.1 General principles 82 ............................................................................................................ 11.2 isolated deep foundation 82 ................................................................................. ................................................................................................. ................ 11.3 deep foundations Group 83 ...................................................................... .................................................................................................. ............................ 12 Structural Strength 85 ............................................................................... ........................................................................................................... ............................ 12.1 General principles 85 ............................................................................................................ 12.2 Piles or concrete foundation elements armé85 .................................................................. 12.3 Metal piles in construction88 steel....................................................................................... 13 stability générale90 ................................................................................................................ ................................................................................................................ 13.1 Généralités90 ...................................................................... .......................................................................................................................... .................................................... 13.2 Principle calcul91 ............................................................................ ................................................................................................................... ....................................... 13.3 Models calcul91 ............................................................................... ...................................................................................................................... ....................................... 13.4 Mechanisms rupture92 ................................................................... .......................................................................................................... ....................................... 13.5 Partial factor yR model d ................................................................................ ................................................................................................... ................... 92 14 Justifications to limit state stat e service93 .................................................................................. 3
NF P 94-262 14.1 14.2 14.3
Généralités93 .......................................................................................................................... Land Mobilization by a deep foundation subjected to an axial load .... 93 Displacement and deformation of a fondationprofonde94 ................................................
15 Supporting documents of calculs96 .................................................................................... Annex A (informative) The different types of piles and special provisions conception99.......................................................................................................................... A. 1The different types of pieux99 ............................................................................................ A.
2Pieux drilled (Class 1) 100 ...................................................................................................
A.3Pieux drilled auger (Class 2) 100 ................................................................................................. A.4Les screw piles (Class 3) 101 ...................................................................................................... A.5Pieux beaten closed (Class 4) 103 .............................................................................................. A.6Pieux open beaten steel (Class 5 [BAO, No. 13]) 103 ............................................................... A.7Profilés beaten H (Class 6) 103.................................................................................................... A.8Palplanches battered (Class 7 [PP, No. 16]) 104........................................................................ A.9Micropieu (Classes 1a and 8) 104 ............................................................................................... A. 10Surfaces and perimeters fondation107 elements ................................................................ Annex B (informative) Determination of the conventional categories of terrain108 ............ B. Conventional 1Catégories of terrain108 ................................................................................... B. 2Eléments ranking of sols108 .................................................................................................... Annex C (normative) Partial factors for ultimes114 limit states ............................................. C. 1Préambule114 ............................................................................................................................ C.
2 partial factors for verification of limit states for structures (STR) and geotechnical (GEO) 114 ........................................................................................................ C. Partial 3Facteurs for verification of the ultimate limit state global uprising (UPL) 119 ................................................................................................................................ Annex D (informative) Determination lahauteur equivalent embedding D ............................ e 121 D. 1Préambule121 ............................................................................................................................ D. 2Détermination the height of encastrementéquivalente D ...................................................... e 121 Annex E (informative) Calculation of the bearing value and / or the tensile strength a deep foundation - Overview etexemples122 .................................................................. E. 1Synoptique - Diagram of calculating the valeurde lift and / or resistance of towing a foundation profonde122 ........................................................................................ E. 2Calcul coefficients 122% ........................................................................................................... Annex E (normative) Lift limit and tensile yield strength from the method pressiométrique127 ................................................................................................................................................. F. 1Préambule127 ............................................................................................................................. F.
2Coefficients of modèle127...................................................................................................
F.
3Résistance limite128 ............................................................................................................
F.
4Résistance of pointe129 ......................................................................................................
F. axial131 friction 5Résistance ......................................................................................................
4
NF P 94-262 Annex G (normative) Lift limit and tensile yield strength from the method pénétrométrique137 ................................................................................................................................................. G. 1Préambule137 ............................................................................................................................ G.
2Coefficient of modèle137.....................................................................................................
G.
3Résistance limite138 ............................................................................................................
G.
4Résistance of pointe139 ...................................................................................................... G. 5Résistancede axial141 friction ................................................................................................. Appendix H (Informative) negative friction rating on profonde147 foundation ..................... H. 1Domaine of application147 ....................................................................................................... H.
Maximum 2Frottementnégatif on deep isolée147 unefondation .......................................
H.
3Frottementnégatif on fondationprofonde withinthe a groupe151 ...................................
H. 4Cas personal culées155 ............................................................................................................ Appendix I (Informative) Modeling the transverse behavior of a deep foundation from pressuremeter tests and pénétromètre156 ................................................................. I. 1Pieu isolé156 .............................................................................................................................. 1.2 Groups profondes164 foundations ...................................................................................... 1.3 laws of interaction vis-a-vis loads sismiques166 ............................................................... 1.4 Other model calcul166 ........................................................................................................... Appendix J (Informative) Group effects vis-à-vis a axial168 loading ............................................. J. 1Domaine application - Définition168 .................................................................................. group linked J.2Effet the approximation piles - Efficiency Coefficient C..............................e 168 group J.3Effet related behavior bloc169 .......................................................................................... J.4Estimation the compaction group profondes169 foundations ................................................. J.5Interaction tip between two deep foundations voisines170 ..................................................... Appendix K (Informative) horizontal displacement of a layer terrain171 ................................ K. 1Domaine of application171 ....................................................................................................... K.2Principe of méthode171 ............................................................................................................... K.3Détermination of G (Z) 172 ........................................................................................................... K.4Détermination of gmax (t) 172 ..................................................................................................... K.5Détermination of g (z) in the layer compressible175 ................................................................ K.6Détermination of g (z) in the remblai175 .................................................................................... Appendix L (Informative) axial stiffness of a foundation profonde177 ................................... L. 1Domaine of application177 ....................................................................................................... L.
2Évaluation from charge177 parameters.............................................................................
L. 3Évaluation from mobilization laws of axial friction and advanced effort ........................................................................................................................................... 178 Annex M (Informative) geotechnical characteristics and values properties terrains180 ........................................................................................................... M. 1Reconnaissance of terrains180 ............................................................................................... 5
NF P 94-262 M.2Terrains in place184 ..................................................................................................................... M.3Matériaux rapportés188 ............................................................................................................... Appendix N (informative) Deformations of the structures and movements fondations189 . N. 1Préambule189 ............................................................................................................................ N.2Déformation structures and movements fondations189 .......................................................... N.3Flèches in concrete buildings armé189...................................................................................... Appendix O (Informative) Checklist for construction supervision and monitoring behavior ouvrages191........................................................................................................... O. 1Généralités191 ........................................................................................................................... 0.
2Surveillance of exécution191 ..............................................................................................
0.
3Suivi of comportement192 ..................................................................................................
O.4Mise implement the method observationnelle192 .................................................................... Appendix P (Informative) Geotechnical categories and duration of use of projet194 .......... P. 1Généralités194 ........................................................................................................................... P.2Classes of conséquence194 ........................................................................................................ P.3Catégorie géotechnique194 ......................................................................................................... P.4Durée usage projet195.................................................................................................................. Appendix Q (Informative) design Dispositionsgénérales for ponts196 ......................................... Q. 1Matériaux constituent of pieux196 .......................................................................................... structural Q.2Résistance of pieux196 .............................................................................................. Q.3Dispositions constructives197 .................................................................................................... Appendix R (Informative) Consideration of geometric imperfections related tolerances of exécution201 .............................................................................................................. R. 1Préambule201....................................................................................................................... R.2Règles to specify in the draft conception201 ............................................................................ particular R.3Cas isolated piles subjected Aune "compression centered" 202 .......................... Appendix S (Informative) Items related to static load tests in compression 203 ................... S. 1Préambule 203 ............................................................................................................................ 5.2 5.3 5.4 5.5 5.6
6
Site Recognition 203 .............................................................................................................. Location of essai203 .............................................................................................................. Piles of essai204 .................................................................................................................... Maximum load essai204 ........................................................................................................ Interpretation of results of essai205 ....................................................................................
NF P 94-262
Foreword This document is for the geotechnical design of deep foundations. It has been developed to complement Eurocode 7 (EN 1997-1) which he is the national application standard for these types of structures. This document is consistent with the principles of limit states with partial factors defined in the standard EN 1990 and its National Annex EN 1990 / NA. It meets the requirements of DIN EN 1997-1 and its national annex NF EN 1997-1 / NA applicable to the calculation of geotechnical structures. The provisions of this document are based on the assumptions listed in section 1.3 of the standard EN 1997-1, which assume in particular a good knowledge of field conditions, the quality control of the execution of works and the choice of a plausible model for the foundation of conduct to the limit state considered. It is important to remember the following: a) The knowledge of ground conditions depends on the size and quality of the geotechnical investigations. This knowledge and the quality control of the execution of works are more important to meet the basic requirements that the accuracy of calculation models and partial factors. b) ruin mechanisms must be plausible to consider and be identified based on actual books or failing behavior data on the results of appropriate modeling. c) Verification of ultimate limit state assumes the study of the critical failure mechanism vis-à-vis the latter with a reliable calculation model used properly. d) Where there is no reliable calculation model for a particular limit state, it may be preferable to the analysis of another limit state, using factors that make it unlikely exceeding the limit state considered . Otherwise, and as appropriate, it is possible to justify the design: —
either by prescriptive measures, when a similar experiment makes unnecessary sizing calculations;
—
or on the basis of load test results or tests on models;
—
either by the observational method, which allows to see the construction design.
Warning This document contains the common procedures used in France for the calculation of deep foundations (those contained in the repositories as Issue 62 - Title V of the GTCC and the NF P 11-212-2 - ex DTU 13.2) as well as those recommended in NF EN 1997-1.
7
NF P 94-262
Lis t of people as s oci ated with the development of the document Editors M BAGUELIN
Fondasol
M BERTHELOT
BUREAU VERITAS / COPREC
M BUSTAMANTE
MB FOUNDATIONS
M BURLON
IFSTTAR / Secretary CNJOG
M CANEPA
DREIF-LREP
FRANK M
IFSTTAR ENPC CERMES / TC 250
M Glandy
Soletanche-Bachy-PILES
M Durand
FUGRO / CNREG
M Vezole
Eiffage / President CNJOG
E xperts r epres enting the players in the profes s ion MMe MAURELCETE IDF / SETRA M Legendre Soletanche Bachy / CNETG M Magnan
IFSTTAR / NSCC
M SIMON
TERRASOL / USG
M VOLCKE
FRANKI FOUNDATION / SOFFONS
A s s ociate experts M CARPINTERO
SOCOTEC
M GAUTHEY
SPIE FOUNDATIONS
M-ROCK LACOSTE
IFSTTAR
M. MIRAILLET
EDF
M Plumelle
CONSULTANT
M SCHMITT
Soletanche Bachy
M VETROFF
FRANKI FOUNDATION
Members of the s ecr etariat of the CN J OG M HABERT MS LEGRAND
CETE Nord-Picardie / AML Lille CETE Nord-Picardie / AML Lille
1 Application domain (1) This paper discusses the design and calculation of deep foundations, rigid inclusions and composite foundations (Section 1 Clauses (3), (7) and (8)) the right of buildings, bridges, towers, masts and chimneys, silos and tanks as well as structures carrying cranes and machinery (NF EN 1990). (2) One can define several types of foundations by their slenderness (shallow foundations, deep or deep
8
NF P 94-262
semi-), their embodiment and mode of operation (shallow foundations on existing soil or ground improved or reinforced by rigid or flexible inclusions, mixed, deep foundations foundations) (Note 1). NOTE 1 - So deep foundation within the meaning of the slenderness can perfectly be used as part of a project providing an intermediate mode between that of a shallow foundation, where all the load is taken up by the soil in place under the sole, and that of a deep foundation i n the traditional sense, which repeats itself the entire load.
(3) The different types of foundations typically are subject to the following definitions: —
Deep foundation (NF P 94-262 - this document): The term "deep foundation" refers to pile foundations, micro-piles, barrettes or wells whose slenderness is high (typically foundations whose length is more than 5 times the diameter or width).
—
Shallow foundation or semi-deep (NF P 94-261): The term "shallow foundation" "or" semi-deep foundation "means the foundation whose slenderness is low (typically less than 5.0). The distinction between a foundation surface and a semi-deep foundation is usually based on the value of the equivalent embedding / B (Appendix D): if the value of this ratio is less than 1.5, it is a shallow foundation; if the value of this ratio is between 1.5 and 5.0 there is a semi-deep foundation.
—
Composite Foundation: type of foundation system mixed foundation or foundation rigid or flexible inclusions: —
Mixed Foundation: the term "joint foundation" applies to the entire sole and pious designed and calculated with direct contact between the two and taking into account the real possibilities of simultaneous mobilization reactions in the soil by the pious and the sole .
—
Foundations rigid inclusions: the term "foundations on rigid inclusions" refers to a soil-building process instead of performing a regular pattern of deep foundations (piles, rigid inclusions) with the primary aim to reduce compaction and optionally d increase lift. Direct contact between the surface foundation and inclusions is avoided by the implementation of a distribution of mattresses (which can be granular material treated or not, ballast, etc.) to maintain a stress distribution Contact compatible with the resistance of the shallow foundation, the slabs or the slab.
—
Foundations soft inclusions: The term "flexible foundations inclusions" refers to a method of reinforcing and soil conditioners in place of providing a regular grid of soft inclusions (stone columns, dynamic replacement, etc.) with the primary aim reduce settlement and if necessary increase lift. Direct contact between the surface foundation and stone columns, in case of incompatibility between contact stresses and the strength of the shallow foundation, the slabs or the slab can be avoided through the implementation of a mattress-up distribution (which may be of the granular material treated or not, ballast, etc.).
(4) Herein applies to the calculation of deep foundations biased axially in compression or in traction or loaded transversely, these geotechnical structures are installed by driving, by vibrating, by jacking, by screwing or drilling with or without injection. The detailed list of these foundations, as their specific implementing rules are specified in Annex A. The main types of deep foundations are: —
bored piles cast in situ (Figures 1.1 a and b) of concrete or reinforced concrete;
—
Concrete or reinforced concrete bars of different forms cast in place (Figure 1.1 c);
—
refoulants piles cast in situ (Figure 1.2 a) or prefabricated (Figure 1.2 b) of concrete or reinforced concrete;
—
metal piles of different shapes (sheet piles, tubes, profiles H, piling boxes) implemented by threshing, jacking or vibratory driving (Figures 1.2 c and d);
—
micropiles (Figure 1.3);
—
screw piles of concrete or reinforced concrete (Figure 1.4).
(5) The verification of the structural strength of deep foundations falls computing standards for the material that constitutes the (eg NF EN 1992-1-1 with the national annex NF EN 1992-1-1 / NA for deep foundations
9
NF P 94-262
reinforced concrete or EN 1993-1-1 and EN 1993-5 standards with their national annex NF EN 1993-1-1 / NA and NF EN 1993-5 / NA for metal pipe piles, sheet piles, etc. ). (6) This document should be used in conjunction with the NF P 94-282 standard when deep foundations are used to build a retaining wall. (7) When deep foundations are used as part of a project of composite foundation necessary to distinguish two cases (Note 1): —
one where deep foundations (piles, rigid inclusions) make a significant contribution to the justification GEO type of ultimate limit states (lift of the work vis-à-vis the axial stresses and / or transverse, general stability, ... ). This type of use fully covered by the provisions laid down in this document.
—
one where deep foundations (piles, rigid inclusions) make only a small or negligible contribution to the justification of the ultimate limit states. These are projects for which the realization of deep foundations is essentially justified by the state of compaction barring service limit. This type of use is not part of this document.
NOTE 1 - The foundation on soft inclusions (stone columns) are not the subject of this document whether the justification for the ultimate limit state or serviceability limit states. The justification of such structures relies now on professional recommendations or calculation methods available in the literature.
(8) Regarding the application areas of deep foundations defined in Clause 7 of this Section, the provisions of this document still apply in full, on one hand, as regards the determination of the characteristic values of the properties and resistances materials constituting the deep foundation and the soil in place, and secondly, to the characteristic values of the properties and friction resistance and the tip. (9) deep foundations of processes not described in this document or in terms of performance, in terms of constituent materials, may be used provided they have been the subject of a particular specification including specifications 'specific performance and the appropriate parameter values of bearing capacity and strength of materials. These values should be based on experimental justification. In particular, with regard to the bearing capacity, the parameter values must be derived from a set of pile load tests in comparable geotechnical contexts covering those prevailing for the project. (10) This document is fully applicable to projects under the Geotechnical Category 2 (Notes 1 to 3, Appendix P, NF EN 1997-1), that is to say to the current structures that do not show exceptional risk and are not exposed to exceptionally difficult ground or loading conditions. NOTE 1 - In general, the geotechnical category of a work is fixed by the owner or his representative before the start of the study of the project, and, if necessary, specified in the As of progress of studies. NOTE 2 - deep foundations established in lands whose behavior falls rock mechanics are classified mostly in geotechnical category 3. It is the same for deep foundations made on slopes or hillsides whose stability initial does not meet the minimum safety conditions normally required for deep foundations and supporting structures whose geometry is complex or with displacement criteria and / or severe rotation. NOTE 3 - The specifications of this document can be applied to works of Geotechnical Category 3, but it is important in this case to verify their relevance and if necessary to adapt or supplement, taking into account, where appropriate, indications of this document.
(11) This document applies fully as deep foundations subject to static loads or can be considered as such in the supporting calculations. In particular, the calculation of deep foundation subjected to seismic loading responsibility of NF EN 1998-1 and EN 1998-5. In the absence of partial coefficient values related to the lift and the tensile strength of deep foundations for combinations with seismic ELU in EN 1998-1 and EN 1998-5 standards, should be considered a yt partial factor equal to 1.1 for AN relating to the bearing capacity and equal to 1.15 for AN relative to the tensile strength. Guidance on the transverse behavior of deep foundations under seismic load are provided in Annex I (Article I.3).
10
NF P 94-262
(A) and (b) Legend: 1 - precast concrete element; 2 - Injection; 3 - Provisional Tubing (Extraction); 4 - uncased drilling; 5 - reinforced concrete or unreinforced or grout; B: Diameter of the barrel
11
NF P 94-262
(C) Legend: W: Thickness; L: Length
Figure 1.1 - Examples of piles drilled circular and concrete bars
Legend: a - Stake beaten concrete executed in place; b - Stake beat precast concrete; c - pile beaten metal profile; d - Sample piles beaten steel sections
Figure 1.2 - Examples of piles beaten concrete and steel
12
NF P 94-262
Legend: a - Gravity Filling a drill with grout; b - Injection in a single pass by a temporary casing; c Injection in a single pass by a carrier member; d - Injection in a single pass by a tube with sleeves; d repeating Injection by a tube with sleeves
Figure 1.3 - Examples of micro piles drilled with injection of a sealing grout
Figure 1.4 - Pile technical examples made by screwing
13
NF P 94-262
2 references The documents referenced below are indispensable for the application of this standard. For dated references, only the edition cited applies. For undated references the latest edition of the publication to which it is referred to applies (including amendments). This list is not exhaustive and should refer as appropriate to all standards issued by AFNOR. NF P 94-270, Geotechnical design - Retaining structures - Remblais strengthened and nailed in solid ground. AC P 94-281, Justification of geotechnical structures - supporting Screens - Retaining Walls 1. NF P 94-282, Geotechnical design - Retaining structures - Screens. NF P 94-500, Missions geotechnical engineering - Classifications and specifications. NF EN 1990 Structural Eurocode - Basis of structures with its national annex (EN 1990 / NA). NF EN 1538 Execution of special geotechnical works - Diaphragm walls. NF EN 1991 Eurocode 1: Actions on structures with its National Annex (NF EN 1991 / NA). EN 1992-2, Eurocode 2 - Design of concrete structures - Part 2: Concrete bridges - Design of constructive arrangements with its National Annex (NF EN 1992-2 / NA).
EN 1992-1-1 Eurocode 2 - Design of concrete structures - Part 1-1: General rules and rules for buildings) with its National Annex (NF EN 1992-1-1 / NA).
EN 1993-1-1, Eurocode 3 - Design of steel structures - Part 1-1: General rules and rules for buildings with its National Annex (NF EN 1993-1-1 / NA).
EN 1993-5, Eurocode 3 - Design of steel structures - Part 5: Piles and piles with its National Annex (NF EN 1993-1-5 / NA).
EN 1997-1, Eurocode 7 - Geotechnical design - Part 1: General requirements with its National Annex (NF EN 1997-1 / NA).
EN 1997-2, Eurocode 7 - Geotechnical design - Part 2: Recognition of courses and tests. EN 1998-1, Eurocode 8 - Design of structures for earthquake resistance - Part 1: General rules, seismic actions and rules for buildings with its National Annex (NF EN 1998 / NA).
EN 1 998-5, Eurocode 8 - Design of structures for earthquake resistance - Part 5: Foundations, retaining structures and geotechnical aspects with its National Annex (NF EN 1998-5 / NA).
NF EN 1536, Execution of special geotechnical works - drilled Piles. NF EN 12699, Execution of special geotechnical works - Piles with discharge from the ground. NF EN 14199, Execution of special geotechnical works - Micropiles. NF EN 12501-1, Protection of metallic materials against corrosion - Contact corrosion in soil - Part 1: General.
NF EN 12501-2, Protection of metallic materials against corrosion - Contact corrosion in soil - Part 2: Low alloyed ferrous materials or non-alloy.
EN ISO 14688-1, Geotechnical investigation and testing - Identification and classification of soil - Part 1: Identification and description.
EN ISO 14688-2, Geotechnical investigation and testing - Identification and classification of soil - Part 2: 1 In preparation for.
14
NF P 94-262
pri ncipes for classification.
EN ISO 22476-3, Geotechnical investigation and testing - up testing - Part 3 - penetration test sampler. EN ISO 22476-12, Geotechnical investigation and testing - up testing - Part 1 - Test the static penetrometer mechanical edge.
ISO 4356, Bases for design of buildings. Deformations of buildings to limit states.
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NF P 94-262
3 Terms, definitions and symbols (1) The main terms used herein are defined in this section and shown in Figure 3.1. For the purposes of this document, the terms and definitions given in the NF EN 1990 apply to all Eurocodes and those given in the NF EN 19971 specific to the calculation of geotechnical structures also apply. Finally, the different types of deep foundation elements under this document are described in Annex A. Diameter of the barrel 11 12 13 14 15 16 17 18 9 - tip Enlargement
diameter at the base height of the shell length Drilling depth layer (s) greater than (s) Foundation layer Longitudinal axis reinforcement cage retractor plunger tube
19
10 - Diameter of the 13 cage
Figure 3.1 - Terms and definitions on an example of bored pile of
3.1
21
reinforced concrete
Terms and definitions
3.1.1 Geotechnical share (NF EN 1990) Action transmitted to the structure by the ground, an embankment, a body of water or groundwater.
3.1.2 comparable experience Information documented or clearly established by other means, on the ground considered in the calculation, involving the same types of soil and rock, which can be expected to have similar geotechnical behavior, and similar structures. Information obtained locally are considered particularly relevant.
3.1.3 foundation Lower part of a structure intended to ensure its stability. This term refers as the case of shallow foundations (insole, rafts), semi-deep (wells, wells) or deep.
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NF P 94-262
3.1.4
stake
slender structural member placed in the soil, to transfer thereto the actions that are transmitted by the scope structure him or by the surrounding terrain. It can be prefabricated or produced in place and be implemented by drilling, boring, by vibration, by hammering, screwing or jacking.
3.1.5 bar diaphragm wall element or set of elements interconnected molded wall (for example L-shaped, T or cruciform) and concreted simultaneously.
3.1.6 well deep foundation or semi-deep, of metric order diameter dug shovel or clamshell.
3.1.7 micropieu Pile of small diameter (less than or equal to 300 mm), generally made with special techniques.
3.1.8 drilled pile deep foundation made by drilling or by manual excavation (for example a pile or a drilled micropile, a bar, a shaft, etc.).
3.1.9 pile in soil discharge deep foundation formed by threshing, or jacking or vibration, or screwing of a prefabricated element of reinforced concrete or metal. This term also includes deep foundations implemented by introduction of concrete, grout or mortar in a recess formed by bores, threshing or screwing a tube closed at its base.
3.1.10 Integrity Test Test performed on a finite stake, to check its geometry and condition of the materials in place.
3.1.11 loading test Test consisting in applying a force at the head of a test pile and measuring at least the displacement of the latter under the applied force. There are different types of tests depending on the nature of the force applied (low static loading bearings, single or multiple dynamic impact variable effort jacking speed constant depression), depending on the orientation of force applied (axial or transverse loading head) and in function of measurements (measurements in only head or a pile instrumented allowing access to the distribution of forces along the long pile).
3.1.12 downdrag Geotechnical action where the surrounding land transfer to the deep foundation a downward load when compared to the cup was of deep foundation.
3.2
Symbols and indices
3.2.1 Soils and books (1) The main symbols used in this document relating to land and deep foundations are in 3.2.1.1 and 3.2.I.2. NOTE 1 - The other symbols are defined in the appropriate places in the text.
3.2.1.1 Latin letters ab
surface of the base of a deep foundation
ace
area of the cross section of the shank of a deep foundation
adistance nude naked entredeux élémentsde fondationprofonde bdistance nude naked entredeux élémentsde fondationprofonde 17
NF P 94-262
B smaller width or diameter of the section of a deep foundation effective c'cohésion Ce coefficient of efficiency of a group of deep foundations taken into account to determine its resistance Cmax
maximum value of the compressive strength of the concrete
cu undrained cohesion dentraxe between two deep foundation elements D length of the deep foundation within the field Of
height equivalent Recessed
def
effective installation height
eCM
concrete modulus
Edif
Delayed modulus of the concrete
EM Ménard pressuremeter modulus fck* Characteristic compressive strength to be considered for checks compressive stress of the concrete structure of deep foundation fck
Ala resistance characteristic 28-day compressive
fck(T) characteristic resistance to compression Ala t days; t <28 days k1
empirical coefficient tenantcompte of the delivery mode Inthe soil as well as possible variations in section according to the technique used
k2
empirical coefficient taking into account the difficulties concreting related to the geometry of the foundation
k3
empirical coefficient taking into account the integrity checks
Lplus great length of a deep foundation section (B = L for a deep foundation circular) nNumber piles or test profiles P perimeter of a deep foundation or group of deep foundations Pi pressure pressiometric Ménard mp limit
flow
pressure pressiometric Ménard qc resistance to penetration (measured Static penetrometer according to EN 22476-12) vertical zdistance 3.2.1.2 Greek letters access a coefficient taking into account the long-term effects on the concrete strength (EN 1992-1 1) Y
specific weight
Y 'Half-gauge unit weight incl
18
partial factor for concrete (EN 1992-1-1)
NF P 94-262
9'angle internal friction effective stress 3.2.2 Actions and resistances (1) The main symbols used in this document relating to the actions and resistances are shown in articles 3.2.2.1 and 3.2.2.2. NOTE 1 - The other symbols are defined in the appropriate places in the text. NOTE 2 - For the geotechnical resistance of a deep foundation, indices "c" and "cr" respectively refer to the ultimate strength and creep load of a single deep foundation, "cal" indices "m "respectively refer to a value calculated from test results on the ground and to a value measured during a load test, finally indices" ug "and" MAF "refer to the limit and resistance respectively the pile group creep load. NOTE 3 - "str" index is own actions f rom possible superstructure or resistance of the structure. NOTE 4 - The indices "dst" and "stb" clean respectively destabilizing and stabilizing effect of an action. The indices "inf" and "sup" are respectively related to the favorable and unfavorable nature of the effect of a permanent action for audits of ultimate limit states STR and GEO and UPL. NOTE 5 - The index "k" and "d" respectively refer to the characteristic value and the calculation value of a share or its purpose, or a resistor, or a property of a material .
3.2.2.1 Latin letters "+" Means "should be combined with" A surface of a deep foundation ab surface of a deep foundation to take into account for the calculation of the limit resistance point ad
design value of the accidental action
AEd
value for calculating a seismic action
CD
value calculating limit the effect of an action
Ed
value for calculating the effect of stock
Fd design value of an action Fk characteristic value of an action Fnot negative friction on a deep foundation ft value of the axial tensile load on a deep foundation tensile or a group of deep foundations tensile ftr
value of the transverse load over a deep deep foundation or a group of deep foundation
permanent Gaction Gdst
permanent action for destabilizing vis-à-vis the uprising verification
GSTB stabilizing permanent vertical action vis-à-vis the uprising audit Ginf
actionpermanente destabilizing
GSUP unfavorable actionpermanente Gsnactionde downdrag
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NF P 94-262
Gspactionde transverse thrusts horizontal Hforce kf
linear demobilisationdela pressionfrontale module A widget of fondationprofonde
Ksmodule linear demobilisationdela réactiontangentiellepourunélément defondation deep Side friction engagement Lslongueur for a deep foundation member Mmoment flexing QAction variable Qk1
combination value of the prevailing unfavorable variable action
Qki
combination of value from another unfavorable variable action
qb
resistant pressure limit on the basis of a deep foundation
qs i
stress limit axial friction in the i layer
Ppérimètre a foundation profondecirculaire Rb
Miter limit resistance of a deep foundation
rc
limit resistance to compression of the field of deep foundation
Rc cr
creep load compression of the field of deep foundation
Rc; cacalculated ivaleur R Rc; m
20
c inferred
from test results on the ground
measured value of Rc in one or more load tests of a deep foundation
NF P 94-262 Rc;
pr
Rs calculated value of Rc following the recommendations of the Annex to the NF EN 1990 Rs; limit axial friction resistance of a deep foundation calculated value of Rs cal tensile yield strength of a deep foundation tensile rt Rt
creep load of deep foundation cr
Rt; m rtr T YG
Rt value measured in one or more loading tests a profound resistance foundation of a deep foundation with transverse loads shear 3.2.2.2 Greek letters Y
partial factor for the peak strength of a deep foundation partial factor for a permanent action
YG, sup Partial /TG.inffacteurs for unfavorable / favorable permanent actions YG, sn / YG, sp partial factors for negative friction shares / transverse thrusts YM
partial factor for a parameter of soil (a material property), taking into account also uncertainties in the model
YQ
partial factor for a variable action
YQ, I / Y Q
partial factors for the dominant variable actions / support i
TRdfacteur part to uncertainty in a model of resistance Ys
partial factor for the axial frictional resistance of a deep foundation
Ysdfacteur part to uncertainties in modeling the actions effect Ys; t
partial factor for the tensile strength of a deep foundation
Y Ç
partial factor for the total resistance of a deep foundation correlation factor based on the number of piles tested or test profiles
G; C2
correlation factors to assess the results of static load tests depieux
C3; C4 C5; C6
correlation factors to derive the strength of a deep foundation of résultatsde field reconnaissance at the pile load tests exclusion correlation factors to derive the strength of a deep foundation testing dynamic impact factor for converting the characteristic value representative value of an action
21
NF P 94-262
VojQkî
combination of value to the unfavorable variable action Accompanying i
Vl, LQK, 1
frequent value of the prevailing unfavorable variable action
VQ
frequent value of the unfavorable variable action Accompanying i
V2 IQK i
almost permanent value of the prevailing unfavorable variable action
V2 iQki
almost permanent value to the unfavorable variable action Accompanying i
I
means "the combined effect"
NOTE 1 - The indices of ^ for the combination of values of variable actions Q have the following meanings: —
the first index (0) indicates that it is a combination of value (1) indicates that it is a frequent value, (2) an almost constant value.
—
the second index refers to the action of the variable number.
3.2.3 Abbreviations (1) The main abbreviations used in this document are: ultimate limit state ELECTED - LIVE serviceability limit state - EQU
equilibrium (ultimate limit state)
- GEO
Geotechnical (ultimate limit state)
- STR
structure (ultimate limit state)
- UPL
uprising (ultimate limit state)
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NF P 94-262
4 Behavior of deep foundations 4.1
Overview
(1) The purpose of the section 4 is to describe the behavior under axial load (Section 4.2) and under transverse load (Section 4.3) of a single deep foundation (Notes 1 to 3). NOTE 1 - The behavior of deep foundations under axial load, described in Section 4.2, based on many static load tests in real compression piles conducted until failure (characterized by agreement by pressing the deep foundation over 10% of its width), and usually instrumented throughout the pile length. The behavior of deep foundations under transverse load, described in section 4.3 is also based on full-scale load tests, but limited in number, and of testing of scale models. NOTE 2 - The behavior of deep foundations under cyclic loading is not described in this document. Refer if necessary to specialized articles describing experiments performed on these topics. In the current state of knowledge, only specific tests such as those used for offshore projects help to identify the behavior of deep foundations under cyclic efforts. When the cyclical part of the effort is significant, it is necessary to consider the possibility of a gradual decrease in soil resistance fatigue. NOTE 3 - Schematic behavior patterns recommended for confirmation of stability of deep foundations are presented in Sections 9 and 10 of this document.
4.2
under axial load behavior
(1) When gradually applies an axial load stepwise compression of the head of a single deep foundation, there is a progressive sinking thereof depending on the applied load. Is obtained, usually, a load curve (Figure 4.2.1 a) with a first portion where the depression of the head of the deep foundation remains moderate when the load increases and stabilizes rapidly when held constant and a second part, where the depression of the head of the deep foundation is growing rapidly with each load increment, and stabilizes for a significant period of time (Figures 4.2.1 and 4.2.1 b and c Rating 1). NOTE 1 - The loading curve allows to highlight the limit resistance to compression or limit the lift of the deep foundation Rc and observation of the deep foundation behavior under each loading bearing its creep load Rc cr ( Figure 4.2.1 a).
(2) When applying an axial compression load of the head of a deep foundation, there is a decrease of the axial compressive stress in the deep foundation with depth due to the mobilization of unitary axial friction (Figure 4.2.2). (3) The unit mobilized axial friction force at a given level of deep foundation increases progressively with the vertical movement of it at this level and limit value is most often reached for a very small displacement (or less than one two centimeters). 2
2 The peak strength of a deep foundation (Rb) (Figure 4.2.2) gradually increases with the driving of its tip, but in general, the maximum resistance peak is usually mobilized for a major depression the tip of the deep foundation (over 10% of its width).
23
NF P 94-262
a - load-deflection curve of the head b stabilization of straight legend: a - X: load applied [kN) - Y: Settling of the pile [m] b - X: Time [min] - Y: Settling of the pile [mm / h] c - X: load applied [kN) Y: speed driving [m]
Figure 4.2.1 - Examples of curves obtained in a static loading test of pile APARTIR only measures the movement of the head of the pile
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NF P 94-262
Legend: X: pile head load [kN] - Y: Depth [m] Figure 4.2.2 - Evolution of efforts with depth in a post subjected to a load static progressive stepwise 4.3
Behavior under transverse stresses
(1) When gradually applied stepwise transverse load (horizontal) at the head of a single deep foundation, there is a progressive horizontal movement thereof depending on the applied load. Is obtained, usually, a load curve with the first part, where the horizontal movement of the head of the deep foundation remains moderate when the load increases and stabilizes quickly when held constant, and a second part, where the horizontal movement of the head of the deep foundation is growing rapidly with each load increment, and stabilizes for a significant period of time. (2) When applying a transverse load the head of a deep foundation, the cross reaction of the mobilized ground at a given level increases progressively with the horizontal movement of the deep foundation at this level (Figure 4.3.1 and Note 1) and, generally, the maximum mobilized effort is achieved for a horizontal displacement of deep foundation rather large (several centimeters). NOTE 1 - curve P (y) is usually called ground reaction curve (Figure 4.3.1).
Legend: P: reaction pressure (Pa) - y: displacement relative horizontal (m) - P: distributed force on the pile (N / m) (P = Pb) (cross-reaction) - Es: Reaction Module (Pa)
Figure 4.3.1 - mobilization curves of the cross-reaction on a stake (3) When a deep foundation is subjected to transverse stresses in head (horizontal force and / or moment), the distribution with the depth of the mobilized cross-reaction is shown diagrammatically in Figure 4.3.2.
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NF P 94-262
Legend: Fc: against stop - Fp stop Figure 4.3.2 - Mobilization of the cross reaction of the field depending on the depth in the case of a short pile (4) When a deep foundation is subjected to lateral force due to an overall horizontal displacement of the soil (Figure 4.3.3 a), the cross-reaction of the mobilized ground at a given level gradually increases with the difference between the horizontal movement of the deep and the free movement of foundation soil at this level (Figure 4.3.3 b).
a - stress on the pieub - Reaction Curve Legend: g (z): free movement of the floor - y (z) displacement with the pile - Ay = y (z) - g (z)
Figure 4.3.3 - Mobilization of the cross reaction of the field in the case of a displacement Overall thereof 4.4
failure mechanisms or unacceptable disorders
4.4.1 Overview
26
NF P 94-262
(1) Deep foundations and structures they support may perish or suffer unacceptable disorders mainly due to the failure or excessive deformation of the structure, the field in which the foundation is completed or the site where the structure is built . (2) It follows the behaviors and mechanisms described in sections 4.2 and 4.3 that different limit states to be considered for the deep foundations (Note 1): — ultimate limit states of the ground fault resistance by lift failure, tensile strength or cross reaction
(Section 4.4.2); — the ultimate limit states fault structural strength of deep foundations compressive, tensile, bending,
buckling or shear (Section 4.4.3); — the ultimate limit state general stability of the site (Article 4.4.4); — the ultimate limit states and ground deformation service and the foundation (Article 4.4.5).
NOTE 1 - The detailed list of limit states to be considered for a project is given in section 7.2 of EN 1997-1 standard. It is specified in section 8 of this document borderlines usually to check for current projects.
(3) It is necessary to check, where appropriate, that no such limit states can not be achieved during the construction of the scope and structure during its expected useful life.
4.4.2
Lot Resistance
(1) The ruin of the scope structure or the foundation itself, can occur when the forces transmitted to the ground by a single pile or all of the foundation exceed a critical threshold or are too close to the limit resistance mobilized by the ground. (2) As appropriate (axial or lateral force), different failure mechanisms terrain may occur (punching, tearing or rupture stop modes).
4.4.3
structural strength
(1) The ruin of a deep foundation may occur when the structural strength is insufficient vis-à-vis the impact of the worst action (bending moment, shear, axial force of compression or tension) it will have to undergo, under construction or in use. (2) The elements of a deep foundation structure must be verified vis-à-vis the breakdown according to the specifications of 2.4.6.4 items (Notes 1 and 2) and 7.8 of EN 1997-1 standard. NOTE 1 - Design values of material strengths and resistances of structural elements are to be determined in accordance with instructions on the appropriate calculation standards constituent material of deep foundations (eg DIN EN 1992 for concrete piles and NF EN 1993 for metal piles structural steel). NOTE 2 - Additional provisions to DIN EN 1992 are provided in Sections 6.4 and 12 of this document. They concern the factors to be applied to the characteristic values of concrete resistance to reflect the embodiment of deep concrete foundations, integrity checks and design specifics of deep foundations vis-à-vis the effort edged.
4.4.4
general site stability
(1) In each relevant case-specific analysis of the stability of the site which is located pile foundation and a study of the risk of instability of the site linked to the achievement of the work must be performed (Note 1). NOTE 1 - the overall stability verification procedures are subject to Section 13 of this document.
(2) When the general stability of the site before work begins or under construction is not required level of security, it should take appropriate structural arrangements to make steady work zone (Notes 1 and 2). NOTE 1 - There is therefore no need to consider the actions caused by a movement of all the land linked to a site of general instability phenomenon as vis-à-vis actions of deep foundations. NOTE 2 - The realization of deep foundations can be to stabilize an unstable site, but in this case, their justification is
27
NF P 94-262
5 Actions and geometric data not part of this document. 4.4.5
Disorders related to travel deep foundations
(1) The displacement of deep foundation is likely to be unacceptable for the structure of deep foundations themselves or for the construction of current scope structure and / or during operation (Notes 1 and 2). NOTE 1 - Depending on their size and as applicable, the vertical displacement and the horizontal displacement of deep foundations, can cause disorders and impair the function of buildings they support or even lead to their ruin. NOTE 2 - structures carried for which a horizontal displacement of the foundation may be excessive for example: — a foot bridge abutment of an embankment built on a compressible layer; — of dolphins or very slender structures (wind or the like);
(2) In all cases, it is appropriate to adopt constructive measures that are appropriate to field conditions and take account of predictable moves, while aiming, whenever possible, to limit the importance (Note 1). NOTE 1 - In general, displacement calculations give only an approximate indication of their real value and is useful where possible to refer to comparable experience.
28
NF P 94-262
5.1
stock
5.1.1 General calculation principle (1) The shares shall be classified in accordance with Article 4.1.1 of the NF EN 1990, distinguishing: — permanent actions (G); — variable actions (Q); — accidental actions (A).
(2) The representative values of the shares shall be determined in accordance with sections 4.1.2 and 4.1.3 of NF EN 1990 and Article 2.4.5 of the standard EN 1997-1 (Notes 1 and 2). NOTE 1 - The shares have more representative values. The characteristic value of an action (subscripted k) is its main representative value. It is determined in accordance with section 4.1.2 of EN 1990 standard completed for geotechnical actions by section 2.4.5.1 of EN 1997-1 standard. NOTE 2 - The values of the variables representative actions other than the characteristic value Qk is determined according to the principles set out in section 4.1.3 of the standard NF EN 1990. These are derived from the Qk value by multiplying it by a coefficient Ÿ The coefficients T0, Ti, and corresponding T are given for normal loads (building, road traffic, track, etc.) in the appropriate places of the NF EN 1990.
(3) share calculation values and their effects must be determined in accordance with sections 6.3.1 and 6.3.2 of the standard NF EN 1990, supplemented, for geotechnical actions by Article 2.4.6.1 of the NF EN 1997-1 (Note 1). NOTE 1 - The actions to take into account the different combinations of actions are determined by the NF EN 1990 section 6.4 for calculations for ultimate limit states and section 6.5 for calculations limit state on duty.
(4) The ranking of actions and the determination of their value must also consider the provisions of this standard (Note 1). NOTE 1 - Details are provided in this section or in the appropriate places in this document, firstly for the classification of actions depending on their origin, their spatial variation and nature, and secondly to determining values of geotechnical actions and the consideration of the effects due to water.
5.1.2 direct drive Shares (1) The actions applied to the foundation, other than those due to water, the origin of which is not related to the presence of ground and are not passed through it, should be determined in accordance with NF EN 1991 or otherwise set by the market (Note 1). NOTE 1 - Attention is drawn to the fact that the intensity of direct drive action may depend on the soil-structure interaction. For example, the distribution of shares between the different piles may depend on the rigidity of the structure and scope of that of each pile.3
3 The weight of the foundation is to be introduced in the calculations with the most likely value, evaluated from the volumes defined by the dimensions provided on the execution plans. 29
NF P 94-262
5.1.3 Actions due to ground 5.1.3.1 weight original stock (1) Actions underweight origin (weight, thrust, thrust) must be treated as permanent actions in the combinations of actions. (2) The characteristic value of an original weight action must be determined: — from volumes, taking into account the adopted operating model (Note 1) and a possible adverse
change in geometry when it is foreseeable; — from the volume weight land measured at the geotechnical and / or representative of bibliographic
data in the case of ground up (Note 2) — from representative volumetric weight into account the nature of the soil, its implementation mode and
compactness in the case of reported soil (Note 2). NOTE 1 - In the case of a structure providing a supporting function, the volume of land causing a weight effect on the foundation depends on the calculation model adopted for the mobilization of the thrust. NOTE 2 - Indications are given in Section 6 and Annex M for determining the specific gravity of the land in place (Articles 6.2 and M.2) and reported materials (items 6.3 and M.3).
5.1.3.2
thrust or thrust actions
(1) Shares of thrust or passive earth that act on a screen or wall must be determined in accordance with the NF EN 1997-1, Section 9.5 and NF P 94-281 and NF P 94-282 standard (Notes 1 and 2). NOTE 1 - The intensity and distribution of thrust or thrust actions depend on the considered type of structure, mechanical characteristics of the soil and the amplitude of the displacements may affect the screen on which carry these pressures. NOTE 2 - The recommended procedures for the calculation of these actions are indicated in the Complementary Standards NF P 94-281 and NF P 94-282 dealing with retaining structures, respectively walls and screens.
(2) Soil pressure acting on deep foundations due to a displacement of the foundation should be treated as the reactions of support and be evaluated from suitable calculation models (Notes 1 and 2). NOTE 1 - It is for example the case of the reaction of the ground around a deep foundation solicited by a horizontal force in the lead. NOTE 2 - The recommended models for the calculation of these pressures are indicated in Annexes I and K.
(3) The actions of pushing or soil abutment must be treated as permanent actions in the combinations of actions (Note 1). NOTE 1 - Depending on the case, are attributed to these shares, a maximum characteristic value alone or a couple of characteristic values, maximum and minimum, respectively, considering the worst of both to limit state studied.
5.1.3.3
Actions due to an overall displacement of the soil
(1) Actions due to an overall displacement of soil (Notes 1 to 3) shall be determined in accordance with the NF EN 1997-1 and this document. NOTE 1 - These actions may be due to: —
is a phenomenon of instability of the book's website,
—
either a slowdown or a soil creep under the lasting effect of a load or a lowering of the water table.
NOTE 2 - The shares resulting from site instability phenomenon beyond the scope of this standard. This type of problem occurs especially when the book is set in the mountains and foundations across scree stability limit. Similarly, this standard does not apply to the case of mining sites, underground quarries, karst sites or sites where loess (or fill) effondrables are present. Such conditions are likely to motivate a project classification in geotechnical category 3.
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NF P 94-262
5.1.5 Actions due to water NOTE 3 - considered actions are: —
the actions caused by a soil compaction, called negative friction;
—
actions generated by a horizontal displacement of the soil, called transverse thrusts.
(2) The forces due to the negative friction on a pile foundation or part of backfilled structure should be evaluated according to an appropriate model (Annex H) and be introduced into the calculations as a representative characteristic value of the corresponding action. (3) The transverse forces acting on a pile foundation or part of backfilled structure must be evaluated from a representative function of the soil displacement by considering it as an action (Appendix K). (4) The forces due to friction and negative transverse forces should be treated as permanent actions in equity combinations (Note 1). NOTE 1 - The shares due to overall ground displacements have an inte nsity that varies generally in the same direction by moving towards a limit, so it should place them in the category of permanent actions. These actions, however, were isolated from other permanent actions because they may not be the same weights, difficulty circumvented by applying a coefficient model to determine.
5.1.4 Shares soilborne (1) Shares soilborne, other than those due to water and the origin of which is not related to the presence of the ground, but seeking the foundation through it must be determined in accordance with NF EN 1997-1 section 9.5 and NF P 94-281 and NF P 94-282 standard (Notes 1 to 3). NOTE 1 - In the usual case, this is mainly the effect of pressure on a retaining wall (abutment for example) supporting an operating expense or storage. NOTE 2 - The intensity and distribution of these pressures depend on the considered type of structure, mechanical properties of the soil and the amplitude movements may affect the screen that exert such pressures. For example, the distribution of a variable load through an embankment can be studied according to different models whose validity depends on the type of the load, its duration of application, and the nature of the structure. NOTE 3 - The recommended procedures for the calculation of pressure on a screen are shown in complementary standards NF P 94-281 and NF P 94-282 dealing with retaining structures, respectively walls and screens. 4
5.1.5.1
Overview
(1) Targeted actions are of two types: — the water in the field is in equilibrium or near hydrostatic equilibrium, ie the effect of hydraulic gradients is negligible and actions due to water can be represented in the form of static pressures (Note 1 ); — Water generates hydrodynamic actions. NOTE 1 - This is the water pressure field in contact with the structure. This action is similar to a direct drive action. In most cases, it results in pushing "Archimedes" on the structure. The presence of water also has the effect of changing the actions due to field by the effect of "planing" of it. If water flows into the ground, the hydraulic gradient also changes the actions due to ground by the effect commonly called "stream of pressure."
(2) The choice of the positions of the free water surface and the piezometric levels of groundwater must (Notes 1 to 4): — be done based on the recognition of hydraulic and hydrogeological conditions of the site; — be appropriate to limit state considered taking into account the positive or negative nature of the effect of resulting actions.
4 Shares soilborne, other than those due to water and the origin of which is not related to the presence of the soil, should be treated as variable or permanent actions in combinations of actions according to their duration application in relation to the project situation examined. 31
NF P 94-262
NOTE 1 - Changes in water conditions (soaking, drying) can alter underground water status of soil and thus their mechanical characteristics. The imbibing of some soils (loess embankment or have experienced only low saturation degrees) can cause a phenomenon of land subsidence. The floors immediately below the base of a deep foundation may lose because of imbibing some of their lift which can lead to more or less consequential damages for the scope structure. NOTE 2 - It is important to note that the values of the mechanical parameters of soils vary according to their state of saturation and should therefore be attentive to the time of year during which awards were performed. NOTE 3 - It is recalled that the water levels fall geometric data (Article 5.2) and that their values are, as the case of excess or by default measured levels, nominal or estimated (Clause 5.2.2 ( 2)). NOTE 4 - The values of water levels are determined during the project studies. Indications are given in sections 7.1 and 5.2 of this document for establishing the reference levels.
5.1.5.2
static pressures
(1) The intensity and pressure distribution must be evaluated from the reference levels for the design situation considered (Note 1). NOTE 1 - The situations and reference levels to consider during construction and during operation respectively in clauses 7.1.2 and 7.1.3 of this standard. Article 5.2 reminds definitions usually considered baselines.
(2) Action due to water, the effect can be likened to that of static pressures must be processed for a given project situation as a permanent action in the combinations of shares (Note 1). NOTE 1 - It is through the different design situations s tudied its variability is taken into account.
32
NF P 94-262
hydrodynamic 5.1.5.3Actions (1) The current hydrodynamic actions should be evaluated from the reference levels for the design situation considered (Notes 1 and 2). NOTE 1 - In the case of structures operating in coastal location, attention is drawn to the fact that the intensity of wave effect becomes significant when the wave amplitude reaches about two meters or more. A specific study (dynamic) is required in each case because the effects of the swell highly dependent on geometrical and mechanical characteristics of the structure. NOTE 2 - In usual cases, the forces generated by an average speed of water vein v and height h a width B fixed obstacle can be assimilated to a triangular pressure pattern with maximum pressure is located at the free surface and the resultant is (Figure 5.1.5): F = kpwhBv 2
(5.1.5)
h and B are expressed in m; v is the speed in m / s; F is the resultant force in N; pw is the density of water that is allowed to take equal to
1000
kg / m3 in all cases; k takes the following values:
— 0.72 if the planar section of the obstacle is rectangular or square, — 0.35 if the planar section of the obstacle is circular. The height h takes into account the possible general scour considered equal to the water level, but does not include the height of local scour.
Figure 5.1.5 - hydrodynamic effects of the current (2) The hydrodynamic effects other than current action should be specific and the corresponding action will study, according to its nature and intensity, be classified as variable or accidental actions (Notes 1 to 3). NOTE 1 - hydrodynamic actions referred mainly those due to swell, the tidal current, wave action or to those caused by an earthquake.
33
NF P 94-262
NOTE 2 - The choice of model of action to be adopted to assess the pseudo-static value of a share hydrodynamics for a project given situation is based on project requirements and limit state considered.
2
It is most often specialists and is to be defined before the project studies. NOTE 3 - In the case of structures operating in coastal location, a specific study (dynamic) is usually necessary to set the intensity of the effects of the swell.
5.1.6 seismic actions (1) The calculation of deep foundation under seismic conditions not directly from this standard. Seismic actions are transmitted through the ground to calculate and take into account according to the specifications of DIN EN 1998. (2) This standard deals, regarding the consideration of seismic conditions, only partial factors to be applied to the lift or the tensile strength of a deep foundation (Section 1 Clause (11)) (Note 1). NOTE 1 - In the context of the use of models with local laws of soil-structure interaction to evaluate the behavior of a deep foundation under seismic loading, indications concerning the estimation of the reaction module and the plastic bearing are given in Annex I.
5.2
geometric data
5.2.1 General principles (1) The rating and slope of the land surface, water levels, the levels of the interfaces between the layers, levels of geotechnical excavations and the dimensions must be treated as geometric data and ratings should reflect the variation of the actual values in situ. (2) When uncertainty AThas relative to a geometric data is significant and likely to have a significant impact on the reliability of the project, the design value of this data, ad, be deduced from the anom nominal value by applying the relationship: d
at
5.2.2
=A "
± Aa
(5.2.1)
marker levels and layer interfaces
(1) It must be based on actual values (Note 1) in situ ground level, and if any of the planned excavations and the potential scour the terrain (Clause 7.1.2 (3)). NOTE 1 - These important data are normally set during project development and validation stage of implementation studies.
(2) When the values of the levels of the ground surface and layer interfaces are determined conservatively, uncertainty AThas to consider is zero.
5.2.3
Water levels
(1) The choice of the values of groundwater levels in waters outside the ground and groundwater (Note 1) must be performed based on the recognition of hydraulic and hydrogeological conditions of the site. 5
in the Recommendations can be found for the limit states of Water Site Works (ROSA 2000) released by CETMEF guidance for the calculation of hydrodynamic loads of river or ocean current and the effects of the swell and wave action. 5
34
NF P 94-262
NOTE 1 - Groundwater can be free or captive (charge sheet). External waters are open water (river or other). The water levels may be different from those found during the site reconnaissance. They may also change during the life of the structure (for example when the screen is dam to the flow of a sheet or in the case of a confined aquifer).
(2) For a given design situation (Article 7.1), the value of a groundwater level should be a conservative estimate (Note 1) the worst level vis-à-vis the limit state considered (Note 2), may occur during the project situation examined. NOTE 1 - The characteristic value is, as appropriate, by a plus or minus value of measured levels, nominal or estimated. NOTE 2 - This is to say, taking i nto account the positive or negative nature of the effect of resulting actions.
(3) He agreed that the groundwater level of the waters outside the ground and underground, in situations of persistent and transient design or set priority by referring, at EB (almost permanent level) at EF (common) and in EH (characteristic) (Notes 1 and 2), when the values of these levels are easily accessible (Note 3) (Figure 5.2.3). NOTE 1 - adopted notations and definitions that follow refer to the National Annex to standard EN 1990 and adapted to the case of piles based on books. EB level can be defined as that corresponding to the level likely to be exceeded for 50% of the reference time, the level EF for 1% of the reference time and the level EH present in principle a return period of 50 years. NOTE 2 - The reference time is normally the life of the book and, failing that, it should be considered the equal to 50 years. NOTE 3 - The levels to be considered may be different EH and EB levels as defined in this clause, especially during the construction phase.
(4) Where appropriate, it should set the maximum EE level attainable during the lifetime of the structure for accident situations (Note 1 and Figure 5.2.3). NOTE 1 - EE level corresponds to a dimension in the structure in which a capping device limits the pressure of the water.
(5) Unless otherwise specified, the design value of a water level must be taken equal to its characteristic value (Note 1). NOTE 1 - A water level is normally treated as a geometrical data and calculation value deduced from its nominal value characteristic or from the relationship 5.2.1. To the extent that the characteristic value of the position of a water level is set by the market, or when it was given the fluctuations of a layer to define its characteristic level, uncertainty Aa to consider is zero.
35
NF P 94-262
Figure 5.2.3 - Representation of water levels EB, EF, EH and EE
36
NF P 94-262
6
Properties of land and materials
6.1 General principles (1) The properties of the land and the characteristic values values of geotechnical parameters shall be determined in accordance with standards NF EN 1997-1 (Articles 2.4.3 and 2.4.5.2) and EN 1997-2, taking into account the provisions of Articles 6.2 for land in place and 6.3 for the reported materials. (2) The materials properties characteristic values values of deep foundations must be determined in accordance with the relevant design standards (Notes 1 and 2) and where necessary the appropriate product standards. NOTE 1 - For example, according to the specifications of DIN EN 1992-1-1 for concrete piles and those of the standard NF EN 1993-1-1 for steel piles of structural steel. NOTE 2 - Additional rules applicable to conventional products (reinforced concrete, structural steel) for the calculation of deep foundations, however, are listed in section 6.4 of this document.
6.2 Land up (1) It is necessary to conduct a geotechnical site (Notes 1 to 3), to a sufficient depth, to identify fields in place as well as hydraulic and hydrogeologic conditions, establish geotechnical model of the site and set the representative values properties the land necessary for the verification of limit states and execution of the work. NOTE 1 - For deep foundations, it is not possible to ensure that the minimum requirements will be met with negligible risk only on the basis of experience and qualitative geotechnical. Surveys including a characterization of the mechanical properties of land are needed. NOTE 2 - The importance and content of recognitions are based on the type of structure, ground conditions and successful role models and should adjust the consistency and volume of recognitions and studies Geotechnical Category project (Appendix P). A geological and hydrogeological site investigation completed by recognition with tests on the soil in place or laboratory testing is usually required. NOTE 3 - The essential requirements and important points regarding the objective of the geotechnical investigations and their contents are listed in the NF EN 1997-1 and EN 1997-2. Recall in Annex M (Article M.1) important points to consider.
(2) A geotechnical terrain model must be established (Note 1) in the pre-project studies and projects within the meaning of the NF P 94-500 standard. For each of the project areas within which the thicknesses of the different layers of soil can be regarded as uniform and homogeneous properties, should be defined: — the mean values and the representative values or characteristics of the parameters of the different soil layers (Note 2); — conditions to the geometric limits (ground layers, ...), mechanical (overload, ...) and water (water flow conditions, ...). NOTE 1 - A geotechnical model is essential to design, study and design a pile foundation and also to monitor and control its execution. NOTE 2 - These parameters incl ude the specific weight, drained s hear parameters and undrained, parameters derived from pressuremeter and penetrometer testing and other relevant parameters.
(3) The properties of the land and the characteristic values of geotechnical parameters to be determined, including the construction phases, in accordance with sections 2.4.3 and 2.4.5.2 of standard NF EN 1997 (Notes 1 and 2), supplemented by indications of articles and M.2.1 M.2.2. NOTE 1 - It is particularly important that the properties of the land is deducted directly or correlations, testing up or standardized laboratory tests, and that the characteristic parameter value is based on the data that can be if necessary
37
NF P 94-262
supplemented by the teachings of the experiment (Clause 6.2 (4)). When using correlations for the property values of land, it is appropriate that the correlations used are appropriate to field conditions and the test equipment used and documented (M.2 Clause (3)). NOTE 2 - It is also important that the chosen characteristic value for a geotechnical parameter is a conservative estimate of the value that influences the limit state considered (Article M.2.2).
(4) The representativeness and coherence of different characteristic values of geotechnical parameters used in justification of calculations must be controlled (Note 1). NOTE 1 - geotechnical parameters characteristic values are for example compared to previous information obtained locally. These comparisons were intended to eliminate manifestly irrelevant or inconsistent values.
6.3 materials reported (1) It should specify the nature of a reported material and its property values before the project studies distinguishing if the source material is not prescribed, from where it is imposed (Notes 1-3 ). NOTE 1 - When the source of the reported land is not prescribed, they are not subject to prior geotechnical studies and the procedure is:
— before the start of studies: to define the properties of the fill (Note 2 and Clause M.3 (3)) and to set criteria to be met in order to obtain (eg: Field class and creation condition);
— before beginning work: searching borrow areas or possible sources corresponding to the defined criteria, based on a geotechnical or on documented existing data;
— during the work: to control the convenience of the stocked material and its implementation. NOTE 2 - in Annex M.3 It shows the volume weight values usually taken into account in the calculations for the reported ground currents. NOTE 3 - When the source of the insert material is imposed (material from the site or near the site borrowing), the procedure comprises:
— before the start of study: performing a geotechnical for securing at least the specific gravity and to identify the reported properties of the soil;
— during the work: to control the convenience of the stocked material and its implementation.
(2) Should be defined during the the project studies the following geotechnical properties: — the volume and weight when it takes place, the shearing parameters (angle of internal friction and cohesion) and strain as well as other relevant parameters; — the requirements for the particle size distribution (class of material, uniformity coefficient) and, when appropriate, those relating to the implementation of the material (water content, optimal density, etc.).
38
NF P 94-262
6.4 Constituent materials of deep foundations 6.4.1 Concrete, grout or mortar (1) For checking the structural strength of a deep foundation in concrete, grout or mortar, the provisions of EN 1992-1-1 standard with its national annex NF EN 1992-1-1 / NA apply, supplemented by the following specifications. (2) Pursuant to the standard EN 1992-1-1, for the establishment of projects, concrete, grout or mortar must be defined: —
by its characteristic compressive strength fck *;
—
by its characteristic resistance to traction fctk005;
— Ecm by its modulus of elasticity. (3) The characteristic value of the compressive strength of concrete, grout or mortar in a deep foundation is to be determined from the following formula (Notes 1 to 3 and Table 6.4.1.1).
V
fl = Inf (((0; C_, f) t
(8.4.1.1) k
1k2 NOTE 1 - Cmax reflects the constraints of implementation of concrete, grout or mortar costs following the technology used. NOTE 2 - Verification of concrete, grout or mortar SLE is sufficient provision dispensation to take into account the standard abatement on the nominal dimensions as envisaged in Article 2.3.4.2 NF EN 1992-1. NOTE 3 - coefficients ki and k 2Which reflect the implementation conditions are for them to replace the coefficient kf equal to 1.1 of section 2.4.2.5 of EN 1992-1-1 standard.
(4) The design value of the resistance to simple compression of the concrete, grout or mortar in a deep foundation is to be determined from the following formula and Table 6.4.1.2: f
ak ^ ck ■
fcd = Min has \
cc ^ 3 " c
incl
(6.4.1.2) inc l
acc with a coefficient whose value is equal to 1.0 of the height where the pile is armed and 0.8 on the height at which the pile is not armed. (5) The coefficient k1 shown in Table 6.4.1.1 can be decreased by 0.1, only for bored piles and the webs (class 1), where the nature of the terrain to be traversed ensures stable borehole wall or when the pile is cased and concrete to dryness. (6) The value of the coefficient k2 is equal to 1.0 except in the cases described below: — k2 = 1.05 for bored piles and the bars whose ratio of the smallest dimension B to the length is less than 1/20; — k2 = 1,3-B / 2 for bored piles and the webs of which the smallest dimension B is less than 0.6 m; — k2 = 1.35-B / 2 for bored piles and the webs connecting the two above conditions.
39
NF P 94-262
(7) The values of Cmax parameter and the coefficient k3 are generally respectively equal to 35 MPa 1.0. Particular specifications for foundations supporting bridges are listed in Appendix Q. (8) The value of the coefficient k3 may be taken equal to 1.2 in the case of enhanced control of the quality and continuity of the drum (Table 6.4.1.2). (9) The average values (acmoy) and maximum (ACmax) (Note 1) compressive stress of the concrete to the characteristic serviceability limit state should not exceed, regardless of the exposure class, the following value: and Low (0M3fC,
k; 6FC °, k )
(6413)
NOTE 1 - acmoy and ACmax are respectively the average and maximum stress calculated on the pressed surface of the most stressed section of the element.
(10) The grip limit constraint fbd high adhesion reinforcements must be determined according to standard NF EN 1992-1-1 (Section 8.4.2) with a coefficient n equal to 1.0 (Note 1). NOTE 1 - To determine the limit of adhesion stress fbd high adhesion reinforcement is referred to fck fck, not * that is only used for verification of limit states of compressive concrete.
(11) The Ecm modulus of elasticity of concrete forming deep foundations must be determined in accordance with Article 3.1.3 of the NF EN 1992-1-1 (Table 3.1). (12) For checking the long term stability of deep foundation concrete, grout or mortar, it should take into account a deferred unit Edif equal to (Notes 1 and 2): E Edlf = -y
(6.4.1.4)
NOTE 1 - When checking a deep foundation, composed especially for bending forces, it is customary to enjoy its deformations assimilating its section to that of a homogeneous material and bending resistant. For this purpose, it is appropriate to adopt a medium longitudinal deformation modulus concrete equal to 20 000 MPa for the construction phases of the structure and equal to 10 000 MPa to characterize the long-term behavior. It is also necessary to determine the inertia of a deep foundation without deduction of any metallic core or reservations for auscultation, ie that corresponding to the uncracked structural element gross inertia. NOTE 2 - The effects of concrete shrinkage of the foundation are not taken into account.
40
NF P 94-262
Table 6.4.1.1 - Coefficients for the determination of the resistance characteristic decompression of concrete, grout or mortar piles Cmax
Class
MPa
ki
1
bored piles and strips
35
1.3
2
Flight auger piles with recording parameters (Notes 1,3 and 4)
30
1.35
3
screwed cast piles (Note 2)
35
1.3
4
molded driven piles
35
1.3
Notes: (1) For the purposes of the NF EN 1536, a continuous record of the excavation and concreting parameters graphically must be provided for each pile and be subject to a report in paper form. The values of these variables can be displayed in real time in the machine performing the piles. (2) When the concrete is not done through a hopper but directly to the concrete pump, it is advisable to carry out a specific record of execution parameters. These variables can be displayed in real time by the operator of the machine as a graph. (3) The stakes, for which continuous recording system of excavation and concreting parameters will not work, will be tested by an integrity test. An identical number of integrity tests is to perform on stakes for which registration of the parameters has been completed correctly to serve calibration when interpreting tests. (4) For greater than or equal fck values at 25 MPa, the value of fck * is taken to be 18.33 MPa when the relationship 6.4.1.1 leads to a lesser value.
Table 6.4.1.2 - Minimum number of piles or strips to listen to controls enhanced integrity auscultatory methods (Notes 1 to 4) AT Number of pious concerned
B
C
1/8 by transparency (Note 2) 1/6 by transparency (Note 1/4 impedance (Note + 2) 3) 1/6 impedance (Note 3)
Notes: (1) Procedures A, B or C are allowed but either A and B procedures are possible only if the stakes are armed to their full height. (2) According to NF P 94-160-1 (Sonic through method). In this case, the tubes used, 40 mm minimum inside diameter, are placed so as not to ha rm the coating of the main reinforcement cages. (3) According to the NF P 94-160-4 and NF P 94-160-2 (vibratory method impedance or reflection). When this method is not applicable or when the geometry and geotechnical context are likely to compromise the relevance, it should use the method B. When the default representation of the impedance method is found retrospectively, it appropriate to perform auscultation through the parallel seismic method according to NF P 94-160-3 standard. (4)
EN kind of standards will replace the type of standards NF P 94-160 when they are applicable.
6.4.2 Steel
(1) The behavior of the steel must be set to the appropriate standard for verification of this document applies to:
41
NF P 94-262
—
the structural steels as defined in the NF EN 1993-1-1 (Note 1);
—
to steel reinforced concrete, as defined in the NF EN 1992-1-1 (Note 2);
— prestressing steels, as defined in the NF EN 1992-1-1 (Note 3); — steels for "supporting elements" as defined in the EN 14199 standard. NOTE 1 - NF EN 1993-1-5 standard applies to steel piles structural steel whose elastic limit fy (Reh in the product standard) is usually between 235 and 460 MPa. The other properties (ductility, elongation, etc.) are specified in Section 3.2 of the standard EN 1993-1-1. NOTE 2 - The standard NF EN 1992-1-1 applies to high adhesion and weldable reinforcing materials for a range of yield strength fyk between 400 and 600 MPa. The other properties (ductility, elongation, etc.) are specified in Section 3.2 of the standard EN 1992-1-1. NOTE 3 - EN 1992-1-1 standard applies to son, bars and strands used as prestressing steel in concrete structures and with a sufficiently low susceptibility to stress corrosion in accordance with the criteria specified in standard PR NF EN 10138 or given in a European Technical Approval.
(2) For checking the resistance of the metal structures of structural steel (e.g. the tubular bearing piles or caissons piles), the calculations should be carried out according to standard NF EN 1993-1 and EN 19935 with national schedule, supplemented where appropriate by the provisions specified in this document. (3) It should be verified that the spacing of the reinforcement is less than 5 times (c + © / 2) (with c the thickness of coating and the diameter of the reinforcement ©) and the stress at the almost permanent ELS in steels liabilities do not exceed the following values in the combination of action considered: —
CTS < 1000
wmax for elements or parts of bent elements (that is to say having a tight surface and a compression face);
— CTS <600 wmax for elements or parts of elements fully tensioned.
with CTS (MPa) absolute value of the maximum allowable stress in the frame immediately after the formation of the crack and wmax (mm) opening calculated cracks.
42
NF P 94-262
7 Situations of calculation, loads and combinations of actions 7.1
Situations calculation
7.1.1 General rules (1) The design situations to be considered in defining the design situations should be selected and classified according to the principles defined in Article 3.2 of the NF EN 1990, distinguishing: — sustainable design situations; — transient design situations; — the accidental design situations; — seismic design situations. (2) The choice of design situations should be done before the project studies, taking into account the provisions of Article 2.2 of the NF EN 1997-1.
(3) travel criteria (Note 1) a pile foundation must be fixed before the justification for its stability and the sizing. NOTE 1 - The travel criteria can condition some constructive options and be important to the choice of calculation models.
(4) In the case of structures subjected to the action of water from a table, consider the situations must be analyzed specifically, especially when the level of the table is linked to a water plan submitted to rapid height variation (floods, scoured, tides, etc.). (5) The various cases of operating expenses should be considered to define the most unfavorable transitional situation vis-à-vis each ultimate limit state. (6) The accidental design situations that may be related to site conditions or the execution of the work must be considered.
7.1.2 under construction situations (1) One must check the conditions set by the regulations, by the market, and the worst case for each relevant limit state. (2) For structures established aquatic site, one must always consider the situation defined by the maximum water level for the work of the implementation period (Notes 1 and 2). NOTE 1 - Attention is drawn to the fact that the definition of a maximum level should be compatible with certain enforcement provisions, including those relating to temporary structures. NOTE 2 - This level is set by the market or failing is defined before the project studies. Indications are given in 5.1.5 and 5.2 sections of this document for determining the different water levels.
(3) For structures established affouillable website, one must always consider the level of scouring (Note 1). NOTE 1 - This level is set by the market or failing is defined in the p roject studies.
7.1.3 Situations in operation
(1) One must check the design situations fixed by the regulations, by the market, and the worst situation for each project ultimate limit state and limit state of each relevant service. (2) For a book set in an aquatic site, one should always consider two or three design situations to define the most unfavorable current situation vis-à-vis operating an ultimate limit given Staff (Notes 1 and 2). NOTE 1 - These situations are normally set by the market or in default are defined before the project studies.
43
NF P 94-262
NOTE 2 - In general, the consideration of a minimum and not an average level for assessing the maximum intensity of vertical loads.
(3) When the structure is located on a navigable waterway and is likely to be subjected to a boat shock, transient situation defined according to the considerations of section 5.2.3 should be considered. (4) For structures established affouillable website, one must systematically consider a level determined scour from a bed bottom level taking into account its expected development (development or mining operations) (Note 1). NOTE 1 - These scour levels are set b y the market or failing is defined in the project studies.
7.2
Combination of actions
(1) The effects of actions should be determined by combining the actions in accordance with Article 6.4.3 of the standard NF EN 1990 (Note 1). NOTE 1 - The different combinations of actions to consider are summarized in this section. Additional provisions applicable to the calculation of deep foundation are given in section 7.3.
7.2.1 General principle (1) For each project situation, under construction or in operation, it is necessary to consider the case load and the combination of the worst actions vis-à-vis the target limit state. (2) In a given combination, the different terms should designate original shares and different kind, which excludes share the same action between two terms of the same suit (principle of consistency) (Note 1). NOTE 1 - For example, one can not separate the vertical component of the earth pressure (stabilizing effect) of the horizontal component (destabilizing action).
(3) Geotechnical share the same origin must be calculated in a given combination, from the same representative values of basic properties (Note 1). NOTE 1 - This excludes be assigned to a field two different densities depending on whether one evaluates a thrust action or stop action of this field.
7.2.2 General Expressions combinations vis-à-vis the ultimate limit state action (1) The different combinations of actions to be considered for the ultimate limit states are: — combinations of actions for persistent and transient design situations (fundamental combinations); — combinations of actions for accidental design situations (accidental combinations);
44
NF P 94-262
- combinations of actions for seismic design situations (seismic combinations). (2) In situations of persistent or transient project, it should determine the design value of the effect of actions from the following general expression (fundamental combination for ultimate limit-states STR and GEO) applied in accordance with the provisions of Article 7.3.1 (Notes 1 and 2): = EjZYo ".fGt, ip" + "ZYo.", G "M" + "reiQk.t" + " 'LrOitnA I j> 1d> 1¿> 1 E d
(7.2.2.1)
NOTE 1 - The values of partial factors ^ d epend on the chosen calculation approach and the favorable character or unfavorable vis-à-vis action considered borderline. They can be found in the national annex NF EN 1990. NOTE 2 - The values of Yo coefficients are less than or equal to one to account for the probability of combination of variable actions. They are given for usual loads the appropriate places of the NF EN 1990 (Clause 5.1.1 (2) Note 2 of this document).
(3) For accidental design situations, it should determine the design value of the equity effect from the following general expression (accidental combination for ultimate limit states STR and GEO) (Note 1): NOTE 1 - The values of coefficients Y1 and Y2are less than 1 to account for the probability of combination of variable Ed = E -¡I, "" + "! Gkj, Nfl "+" Ad "+ > 1
"(Y / ifiUVdd ') Oi," + "IY2, Qi., f
ij.2.2.2)
>1
actions. They are given for usual loads the appropriate places of the NF EN 1990 (5.1.1 (2) Note 2 of this document).
(4) For seismic design situations, it should determine the value of calculating the effect of actions on the deep foundation of the structure studied from the relationship (3.17) presented in the article 3.2.4 of the NF EN 1998-1.
7.2.3
general expressions of combinations of actions vis-à-vis the serviceability limit states
(1) The different combinations of actions to be considered for serviceability limit states are as follows (Note 1): — the characteristic combinations; — frequent combinations; — the quasi-permanent combinations. NOTE 1 - Normally, characteristics combinations are used for irreversible limit states, frequent combinations for reversible limit states and quasi-permanent combinations for long-term effects and the appearance of the structure.
(2) For the characteristics combinations, it should determine the design value of the effect of actions Ed from the following general expression: Ed
E \ I Gj " "+" I G "M "+" OK ,, "+" Iy. "Q"
(7.2.3.1) ¿> 1
45
NF P 94-262
d = E {Z Gj sup "+" Z gkh Inf "+" ¥. i Qk i "+" Z ¥ 2. t Qk ljdi jdi
E
(7.2.3.2) i> 1
(4) For the quasi-permanent combinations, it should determine the design value of the effect of actions from the following general expression: Ed
7.3
{ZG jdi
K J. sup
Z G- K J. j di
+ "Z ¥2. Q ii
(7.2.3.3)
inf
Provisions for determining deep foundations
7.3.1 Determination of the effect of actions ULS (1) For the verification of ultimate limit states GEO and STR in situations of persistent or transient project, it should determine the calculation solicitations from the following expression (Notes 1 to 4) E = E {Zj Zj GjsupV Gkjf '+ "\r "G"] '+ " r" G r'+ "Y Q.Qk . l jdi jdi
ZYQ.i ¥ o ,, Qk.ij i> 1J
(7.3.1.1) NOTE 1 - This expression is the combination of actions 7.2.2.1 expression, isolating actions Gsn negative friction (because they do not stack fully with those due to variable actions) and the transverse pushing action of Gsp land given their particular nature (Clause 5.1.3.3 (3)). The cumulation rules of the negative friction and variable actions are specified in Article 7.3.3. NOTE 2 - The values of partial factors to be applied are given in the NF EN 1990. For computational approach 2and actions other than shares due to an overall movement of the ground, it is recommended to apply the values specified in Annex C (Table C.2.1) herein (1.35 and 1.0 respectively to adverse and favorable permanent actions, 1,5 and 0 respectively to adverse and favorable variable actions). For any action of negative and friction transverse thrusts, the values of the partial factors to be applied are indicated in clause 7.3.1 (2). NOTE 3 - It is recalled that, in a given combination, gkj, sup and Gkj.int designate original shares and of different natures, which excludes share the same action between the two parties. For example, it can not affect to the same soil two different masses depending on whether one evaluates a thrust action or weight action. NOTE 4 - It is recalled that the levels of water, selected through situations defined in Article 7.1 should correspond to a low probability of occurrence, and the actions of water (5.1.5) falls permanent actions.
(2) For the verification of ultimate limit states GEO and STR in situations of persistent or transient project, where appropriate taking into account the shares of negative friction or transverse forces, it is appropriate to adopt the values following partial factors: —
ysn is 1.35 or 1.125, the value being selected so as to obtain the most unfavorable effect (Sections
7.3.3 and 8.8); —
Ysp is 1.35 or 0.675, the value being selected so as to obtain the most unfavorable effect (Sections
7.3.3 and 8.8). (3) For the verification of ultimate limit states UPL in situations of persistent or transient project, it should determine the calculation solicitations from the following expression (Notes 1 to 4)
46
E d
=% r E ° '
G
dst ^ kj, dst
NF P 94-262 (7.3.1.2)
"+ 'ZRG,." BG ,,, tt "+" 7q, ¡Q k' + " '^ LrQj, JQK
>1
j> 1i
NOTE 1 - This expression is the combination of actions 7.2.2.1 expression, taking into account the special nature of this failure mode by global hydraulic lift. NOTE 2 - The values of partial factors to be applied are set out in Annex C (Table C.3.1) of this document (1.0 and 0.9 respectively to adverse and favorable permanent actions, 1.5 and 0, respectively to unfavorable and favorable variable actions). NOTE 3 - The values of Yo coefficients are less than or equal to one to account for the probability of combination of variable actions. They are given for usual loads the appropriate places of the NF EN 1990 (5.1.1 (2) Note 2 of this document). NOTE 4 - Unless otherwise specified, it is permissible to assign globally to all unfavorable variable actions transmitted by the field, a product YQ, YJ 1, 1 equal to 1.35.
(4) For the verification of ultimate limit states GEO and STR in accidental design situations, it should determine the calculation solicitations from the following expression (Notes 1 to 3): NOTE 1 - This expression is the combination of actions 7.2.2.2 expression, isolating actions Gsn negative friction Ed =EG, J
Gj, sup "the "^
>1
"+" \ 1 g "+" A "+" [G "}" + "G" "+" (uor ¥ x¡) 1 "+" Y V'-Qk \ (7 3.1.3) Gj, inf "l" ^ d j> 1
i> 1
(because they do not stack fully with those due to variable actions) and the transverse pushing action of Gsp field given its particular character (Clause 5.1.3.3 (3)). The cumulation rules of the negative friction and variable actions are specified in Article 7.3.3. NOTE 2 - In most cases, there is no reason to consider concomitant variable actions with the accidental action, their effects are generally low compared to the portion of accidental solicitations. NOTE 3 - The values of coefficients Ÿ1 and Ÿ2are less than 1 to account for the probability of combination of variable actions. They are given for usual loads the appropriate places of the NF EN 1990 (5.1.1 (2) Note 2). 6 NOTE 1 - The effect of negative friction action Gsn and transverse thrust Gsp due to an overall movement of the ground are not considered. NOTE 2 - Section 13 spécificiquement deals with the study of the overall stability of a site.
(6) For seismic design situations, it should determine the value of calculating the effect of actions on the ^ QQ, 1 G "+" 1 ^. E= (7.3.1.4) VoQki G" '+ "ZYQ, , sup kj, sup j> 1
inf ^ k /> inf
deep foundation of the structure studied from the relationship (3.17) presented in the article 3.2.4 of the NF EN 1998-1.
7.3.2 Determination of the effect of actions to LIVE (1) For checking the serviceability limit states, it is necessary to determine the calculation demands from the following expressions (notes 1,2 and 4): - Combinations characteristics (Note 3)
6 For the verification of ultimate limit states of general stability of the site, it should determine the calculation solicitations from the following expression (Notes 1 and 2): 47
NF P 94-262
Ed = ffc Ge "" + "I G "J: n, V [G " ] '+ "G" "+" Q ,,, "+" I VdjQ ,,,
(7.3.2.1)
I j> 1d> 1i> 1
frequent combinations (Note 3) Ed = E JI Odds, "+" I Gjdf "+" [G ']' + "G" "+" r., Q f, i "+" IV, dQ, there j> 1d> 1i> 1
(7.3.2.2)
quasi-permanent combinations
NOTE 1 - These terms correspond to the combinations of actions 7.2.3.1 to 7.2.3.3 expressions, Ed = EJI Gj, C "+" I gkj, Inf "+" [Gsn \ + "G p" + "IwuQtj i> 1
(7.3.2.3)
>1
>1
isolating actions Gsn negative friction (because they do not stack fully with those due to variable actions) and the transverse pushing action Gsp ground given its particular character (Clause 5.1.3.3 (3)). The cumulation rules of the negative friction and variable actions are specified in 7.3.3. NOTE 2 - It is recalled that, in a given combination, gkj, sup and Gkj.int designate original shares and of different natures, which excludes share the same action between the two parties. For example, one can assign the same soil two different masses depending on whether one evaluates a thrust action or weight action. NOTE 3 - The values of coefficients Yo, Y 1 and Y2are less than or equal to one to account for the probability of combination of variable actions. They are given for usual loads the appropriate sections of the NF EN 1990 (Clause 5.1.1 (2) Note 2). NOTE 4 - The combinations incorporating consideration of negative friction Gsn are specifically described in Section 7.3.3.
7.3.3 Accumulated negative friction and loads due to variable actions (1) Unless more representative model for justifications in which the normal force has a negative character vis-à-vis the compression, retains the following value Fd (Notes 1 to 4) F
d = max {f j snd ; Qd } + Gd
(7.3.3.1)
fd is the design value of the force to be considered;
Gsn; d is the design value of the negative friction; G'd is the normal force calculation value due to permanent actions (except the negative friction) to which
can be added the values of the quasi-permanent units of variable actions; Q'd is the normal force calculation value due to the variable part of variable actions on the same element (the almost permanent part of variable actions is included in the value of G'd). NOTE 1 - In case ^ 2 is nonzero, the value for calculating the effects of Ed shares must be defined using the following specific combinations: - For the quasi-permanent combinations (Note 3), it should determine the calculation s olicitations from the following expression: Ed = E \ IGkjsu ,, "+" IGC inf "+" [G "]" + "G" + "I ^ JQD., >1
48
>1
(7.3.3.2)
NF P 94-262
where Q are the operating costs (without combination with other variable loads) (7.3.3.2) - For the verification of ultimate limit sta tes, it should determine the calculation of loads from the following expression (Note 1): E
z
G "+"{Y ouy , X) max (Gs "; Q , X) '+ " Z
d = Z r oj,SUPGk,SUp "+" Z jGk, Mi ' ' + ' r sp yj> j> ii> ij
sp
sn
e
k
\
(7.3.3.3)
where Q is the operating expenses (without overlapping with other variable loads) (7.3.3.3) and where yo, i is given in the National Annex to the relevant Annex (building, bridge, etc.), the NF EN 1990 or, failing that, in the parts market. NOTE 2 - The need for such rules is because the breakdown of the normal force along the shaft of the elements is different in the case of negative friction and in the case of variable loads. There is no cumulative maximum. The diagram of Figure 7.3.3 shows the behavior for a single element. NOTE 3 - The possible negative friction exerted on the bonding pad and the land or structure of the parts are considered fully overcoming deferred head of the elements. Their design value is therefore added directly to Gd. This provision is justified by the fact that the travel required to reverse the negative friction are more important in the case of an abutment in the case of a deep foundation. NOTE 4 - negative friction should be considered in the type of justifications GEO onl y in combinations on LIVE. Indeed, in theory, increased negative friction on a deep foundation induced depression of the latter which then allows it to mobilize more positive axial friction than before the increase of the same negative friction. For STR type of justification, always involved in negative friction combinations for ULS.
(2) If more representative model for vis-à-vis justifications which the normal force has a favorable character, it is assumed that the normal force generated by the negative friction on the foundation members is zero.
7.3.4
Consideration of variable actions for the calculation of travel
(1) For the verification of travel limit states, unless the contract provides otherwise, it should not accumulate as almost permanent actions with permanent actions in combinations of shares (Notes 1 to 3). NOTE 1 - displacement limit states concern mainly the verification of serviceability limit states for deep foundations (Section 8.3). NOTE 2 - Where appropriate determine the displacement of deep foundation (Clause 8.3 (5)), the values are most often derived from empirical rules, which should if necessary be associated with controls course work, given the approximate nature of the forward estimates. NOTE 3 - The calculation methods available does not allow to consider simply the effect of varying loads, cyclic or dynamic.
49
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NF P 94-262
8
General rules for justification of deep foundations
8.1 Overview (1) The rules in this section apply only to fully current structures under Geotechnical Category 2 (Note 1). NOTE 1 - For projects in geotechnical category 3 (eg for complex structure works or structures on areas requiring justifications seismic conditions or deep foundations used to stabilize unstable slopes) or when conditions ground are unusual, specific tests may be needed.
(2) The supporting calculations of deep foundation must be conducted (Notes 1 and 2): — selecting for each relevant the limit state (or) position (s) the (or the) worst (s) under construction and in operation (Figure 8.1) in accordance with section 7.1; — by determining the stress and the resistors taking into account the provisions of Section 5 for evaluation of actions and geometric data and the section 6 for evaluation of material properties; — selecting combinations of shares pursuant to Article 7.2. NOTE 1 - All behaviors and the mechanisms described in Section 4, which may cause the ruin of a book are to be considered when selecting the relevant limit states and the choice of (or) location (s ) of (the) worst (s). NOTE 2 - In particular, the accidental design situations that may occur in connection with the site conditions (boat bumpers for example), or related to the execution of the work are to be considered.
(3) For each work based on deep foundations, it must justify, when applicable (Note 1) vis-vis the ultimate limit states: — the stability of each pile and complete foundation vis-à-vis a local failure of the land (Note 2); — the breaking strength of deep foundations (Note 3); —
the stability of the work carried vis-à-vis the displacement of pile foundation (Note 1);
—
the overall stability of the complete foundation vis-à-vis a general breakdown of the site (Note 4).
NOTE 1 - The checks to depend on project requirements (Table 8.1) and the justification for ultimate limit state is not necessarily to be done by calculation (eg, that of the general stability of the site or that the destruction or severe damage of the book focused because of a displacement of the foundation). NOTE 2 - The limit states covered are those concerning the lift of the land or the tensile strength of a deep foundation in response to axial displacement of the foundation elements (single pile and pile group in compression or tension) . The audit of a deep foundation the material is also to perform. Under the effect of a transverse displacement of deep foundations, limitations are imposed in terms of constraints in the field. For this type of movement, security concerns compliance with the limit states for the constituent materials of the foundation structure and scope. However, it is permitted for certain projects (eg for dolphins) to set a level of stress not to exceed under transverse stress. NOTE 3 - checks the structural strength of a deep foundation are to do according to the appropriate standard calculation to the material thereof, complemented by the recommendations in this document. The effects of actions to consider are to be determined taking into account the specifications of this document.
NF P 94-262
NOTE 4 - Verification of general stability of the site is cited for memory and is not detailed in this document. It is assumed stable site once the realized work platform and the assumption is that the performance of work does not have a destabilizing effect on the site. If necessary, however, should be checked in the same conditions as for studies of the initial general site stability, and for the most unfavorable final situation, each potential failure surface that includes deep foundation level sufficient security. Section 13, however, provides some elements related to the analysis of the overall stability of a site.
(4) Each deep foundation, it must justify, where appropriate, vis-à-vis the serviceability limit states: — the function of focused work is ensured during its expected life vis-à-vis the displacement of pile foundation (ie the axial and transverse displacements of the pile foundation are compatible with the requirements of the scope structure in service condition) — that the axial load calculation transmitted to the deep foundation is less than a certain proportion of the creep load (Note 1 and Section 14) — the axial and transverse loads of deep foundation are compatible with the requirements of the appropriate standard to the justification provided in its service structure. NOTE 1 - The creep load of a deep foundation is derived from a static loading test or failing to directly lift its limit (Section 14).
(5) Vis-à-vis the bearing service limits or traction state, it is therefore necessary to achieve either a calculation by limiting the load exerted to the deep foundations in a proportion of the creep load (lift or pull) is a calculation to justify the move. If the work requires, a calculation justification movements must however always be achieved.
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Figure 8.1 - Codification of checks in the Eurocodes
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NF P 94-262
Table 8.1 - Checks to make the ultimate limit states for the worst durablesou transient design situations during construction and operation ELECTED kind
deep foundations under axial load Bearing (Note 1) tensile strength (Notes 1 and 2) Structural Strength (Note 3) deep foundations under transverse load Structural Strength (Note 4) head displacement (Note 5) Work site General stability (Note 6)
Computation al approach
GEO GEO / UPL STR
2 2 2
STR GEO
2 2
GEO
2 (or 3)
Notes : (1)
(3)
Verification may cover several failure mechanisms (isolated deep foundation and group of deep foundations). Verification of deep foundations Group considered a block is done according to a type of ELU GEO / STR and UPL. According to the appropriate calculation to standard material of deep foundation.
(4) (5)
The audit focuses only on compliance with limit states for the materials of the foundation. The audit focuses only on compliance with limit states regarding the scope structure
(6)
See clause (3) Note 4 of Article 8.1.
(2)
8.2
ultimate limit states
(1) We should at least check for situations of the worst persistent and transient design under construction or in operation, as the ultimate limit states listed in Table 8.1 are not met (Notes 1 and 2). NOTE 1 - ultimate limit states to be considered fall within the limit state of rupture or excessive deformation of a structural member or ground (STR and GEO) and state limits overall uplift of the structure or the land (UPL) caused by the water pressure (buoyancy) or other vertical actions. NOTE 2 - The ultimate equilibrium limit state (EQU) do not apply to the justification of deep foundations.
(2) In certain draft conditions (work established Aquatic site land subject to flow forces of groundwater or a charge sheet) however it is important to adopt appropriate structural arrangements, regardless of STR and GEO checks (Note 1 ). NOTE 1 - In general, the design of a geotechnical structure is to prevent the occurrence of a brittle fracture, such as efforts redistribution possibilities can be considered to alleviate the accidental failure of support.
(3) Where appropriate, the worst accidental and seismic design situations must be considered. (4) Each ultimate limit state GEO or STR, one should check under the approach of calculation shown in Table 8.1 and in accordance with the specifications in this document, Ed
8.3 Serviceability limit states 7 The effects of actions (Note 1) must be determined by considering the combination of appropriate actions to the design situation (lasting or transient, accidental, seismic).
NF P 94-262
(1) All phenomena that can be detrimental to the function of the worn book and pile foundation should be considered (Notes 1 and 2). NOTE 1 - vis-à-vis justification of serviceability limit states is essentially to ensure that the movements of the pile foundation and the efforts it supports remain low enough to allow the focused work and the foundation deep itself, to perform their intended functions. NOTE 2 - Usually the rationale for deep foundations vis-à-vis the serviceability limit states is to check:
— that the loads transmitted to the deep foundation are eligible for this structure (for example to avoid an unacceptable cracking or corrosion problems);
— the mobilization of the land is low enough under axial load to avoid unacceptable trips to the scope structure.
(2) We must check for all situations of the worst persistent or transient project under construction or in operation (Figure 8.1) that the relevant serviceability limit states are not met (Note 1). NOTE 1 - It must be ensured that Ed
(3) We must check for the construction phases that the serviceability limit states are not achieved visà-vis the characteristics combinations and operating phases they are not achieved vis-à-vis the characteristics and combinations quasi-permanent (Section 7.3.2). (4) Eligible travel limits of the complete foundation must be established before the start of the project study (Note 1). NOTE 1 - The travel limits are based on project requirements (sensitivity range structure). If necessary, they are to be established by experts in structure.
(5) Where appropriate to proceed with supporting calculations for the study of movement (Notes 1 and 2), they must be led from an appropriate calculation model to the complexity of the geometry of the structure and field conditions. In any case, one should consider that the displacement calculation results give only an approximate indication of their real value (Note 3). NOTE 1 - For current projects, it is permissible to determine the movements of a deep foundation from empirical rules or comparable experience or verifying that the transmitted axial load is less than a certain proportion of the creep load deep foundation (Article 14.3). NOTE 2 - Where appropriate (transverse stresses, complex geometry, mixed foundations) should be used digital soil interaction methods - structure (Article 8.6). NOTE 3 - Where possible, the results of displacement calculations are to confront the values observed at a comparable experience.
(6) Where appropriate, it should provide deep foundations movement controls running and, if appropriate, to adopt the observational method (Notes 1 and 2). NOTE 1 - When a criterion of lower displacement calculation precision is imposed, the observational method is to be adopted to ensure that the travel limit states are not achieved. NOTE 2 - This article covers cases where the allowable displacement of a pile foundation is weak and / or result classes are medium or high (Appendix P) and / or you do not have a comparable experience.
8.4
Calculation models
8.4.1 General principles (1) The choice of calculation models must be adapted to the intended limit state (Note 1) and the complexity of the problems from the point of view of the operation of the structure as a geotechnical standpoint (Notes 2 and 3). NOTE 1 - It should generally use a limit equilibrium model to study default ruin of risk bearing capacity of deep foundation or to study the stability of a deep foundation "rigid" subjected to a horizontal solicitation head. A soilstructure interaction model (MISS) is most often appropriate to study a slender deep foundation subjected to transverse stresses (calculation of efforts in the deep foundation and its displacement). The general principles to be respected are given in Section 8.4.2 below, supplemented by information in different sections dedicated to different limit states.
NF P 94-262
NOTE 2 - Care should be taken to use the laws of behavior of materials simple enough not to detract from the clarity and justifications that are based on field properties "measurable." NOTE 3 - Similarly, for lack of a more elaborate calculation model, it is worth checking the stability of a deep foundation from simplified models to link the movement of the head of each element constituting the foundation's efforts exerted on it.
(2) In a computational model of soil-structure interaction, the foot and the head of a deep foundation must be considered free by default (Notes 1 and 2). NOTE 1 - A partial installation Length can be considered if justified in some cases (anchoring in rocky terrain). NOTE 2 - Other head binding conditions with the superstructure can be taken into consideration, with justifications.
(3) Assuming continuity of stress is taken into account between the deep foundation and superstructure, should be taken into account in modeling the interaction between deep foundation and superstructure, stiffness induced by the presence of superstructure and effort (normal force, shear, bending moment) it brings.
8.4.2 Calculation models and limit states (1) The study of ultimate limit states of lift and pull of a deep foundation subjected to a purely axial loading must be conducted from equilibrium calculation models limit under the provisions of sections 9 and 10 (Note 1). NOTE 1 - The justification based on the results of physical models, scale experimentation, observation running is permitted by the NF EN 1997-1 standard. These procedures are beyond the scope of this document.
(2) The study of a deep foundation subjected to a transverse stress (stress in the deep foundation and deformation thereof) must be conducted from a soil-structure interaction calculation model in accordance with sections 11 ( ultimate limit state resistance to transverse loads), 12 (structural strength) and 14 (service limit state) (Notes 1 to 4). NOTE 1 - Guidance for determining the calculation parameters to be used for a model reaction coefficient are given in Annex I and Annex K. NOTE 2 - These methods generally give an approximate indication of the real value of travel deep foundations, except in the case of comparable experience. NOTE 3 - The use of finite element models or finite difference can be useful to estimate travel to serviceability limit states of certain works in the case of complex geometry, interaction between works or to analyze the behavior of some geotechnical category of works 3. however, it is necessary to verify that the mobilized stresses in the numerical model used does not exceed the physical limitations usually considered (for example, by comparing the numerical results in terms of the axial stress and friction values tip resistance deducted pressuremeter or penetrometer methods). NOTE 4 - For the use of finite element methods or finite difference, the use of a parametric study is usually the rule to assess the sensitivity of the movements of the deep foundation and soil mass, and associated stress.
8.5
Deep foundation isolated subjected to an axial force
8.5.1 Model behavior (1) To characterize the behavior of a deep foundation isolated under axial compressive load, it is necessary to define two resistance or load parameters (Note 1 and Figure 8.5.1): — a compressive yield strength or a lift limit Rc; — a compression creep load Rc; cr. NOTE 1 - The values of Rc and Rc cr respectively are determined according to the provisions of Section 9 and Section 14.2.
(2) To characterize the behavior of a deep foundation isolated under axial traction load, it is necessary to define two resistance or load parameters (Note 1 and Figure 8.5.1):
NF P 94-262
— a tensile limit resistance Rt, — Rt a tensile creep load; cr. NOTE 1 - The values of Rt and RTCR are determined respectively according to the provisions of Section 10 and Article 14.2.
(3) Deep foundations can be subjected to compressive and tensile strength vis-à-vis all load combinations (ULS and SLS). However, a number of tests are carried out during the phases of studies and execution depending on the type of stresses applied to the deep foundations (compression or tension) and the consequence of class and the geotechnical category of 'supported book (Article 8.9). (4) Vis-a-vis normal force, it must be accepted for the calculation of the stresses that the deep foundation behaves linearly elastic, and that without a more elaborate model (Note 1) the axial stiffness of the element can be calculated assuming the free element on its lateral surface and simply supported at its tip. NOTE 1 - Appendix L presents two models that are also free to use.
(5) It must be given the load application time (Note 1) when determining the axial stiffness of a deep foundation for calculating vis-à-vis the normal force loads. NOTE 1 - should be identified vis-à-vis the duration of application of a load behavior of the material of the deep foundation (short or long-term module) and the ground according to its conditions drainage and its possible ability to creep.
Figure 8.5.1 - Role Models to consider for a deep foundation under axial load compression and under axial tensile load 8.5.2
Calculation methods
(1) The characteristic value of the lift Rc; k and / or the tensile strength Rt; k must be determined from one of the following methods (Note 1): — static loading test results obtained and interpreted in accordance with DIN EN 1997-1, Section 7.5.2 (Note 2 and Schedule S); — the results of soil tests made profiles and construed in accordance with the appropriate standards with model calculations whose validity has been demonstrated (Note 3 and Appendices F and G) and using the procedure known as the "model pile," either the form described in clauses 7.6.2.3 (5) and (6) of the standard EN 1997-1 or by application of Annex D of the standard NF EN 1990 (Note 4); — the results of soil tests made profiles and construed in accordance with the appropriate standards of computational models whose validity has been demonstrated (Note 3 and Appendices F and G) and using the so-called "alternative" that is presented to the 7.6.2.3 clause (8) of the standard NF EN 1997-1. This method is called by the following procedure "terrain model" (Notes 5 and 6);
NF P 94-262
— of dynamic impact test results (Articles 7.5.3 and 7.6.2.4 of standard NF EN 1997-1) performed on deep foundations in accordance with an agreed procedure and a calculation procedure whose validity has been demonstrated ( Note 7). NOTE 1 - Other possible approaches (e.g., from the behavior observed for a comparable foundation piles, under threshing formulas or lift derived from the wave propagation tests) fall outside the scope of this standard . NOTE 2 - Until the publication of the standard EN ISO 22477-1, the provisions of the NF P 94-150-1 standard apply. Recall that pile load tests are required as specified in clause 7.5.1 (1) of the EN 1997-1 standard. deep foundation load tests must be performed in the following situations:
— when using a type of deep foundation or an installation method for which there are no comparable experiences; — when deep foundations have not been tested u nder similar conditions of soil and loading; — when deep foundations will be subject to loading for which theory and experience do not provide sufficient confidence in the design made. During the load test, then it should be applied to deep foundation similar load to the planned shipment;
— when the observations made during installation indicate a behavior of deep foundations that deviates strongly and unfavorably the expected behavior based on the recognition of the site or experience and when additional recognitions do not explain the reasons for this gap. NOTE 3 - The evaluation methods of the lift from the results of tests performed on soil must be established from deep foundation load testing and comparable experiences. Empirical methods described in Appendices F and G respectively based Ménard pressuremeter tests and static penetration tests are examples of calculation methods that can be considered validated. NOTE 4 - The procedure, known as the "model pile" is to calculate in a homogeneous area lift or the tensile strength of a deep foundation, type and geometry (diameter, length) attached to the right of each survey recognition deemed representative of the site and to implement the choice two methods:
—
is applied by means of the correlation factors £ 3 and £ 4 the general formula of (9.2.3.1) to determine the lift characteristic of the deep foundation or the general formula (10.2.3.1) to determine the characteristic resistance of the tensile deep foundation ;
— either apply to the N values of lift Rc corresponding to the N polls the study area the procedure in Article D.7.2 of DIN EN 1990. It is recommended to assume that the distribution of values Rc is lognormal. Attention is drawn to the need for both methods to work on a homogeneous area of statistical standpoint. It is then necessary to have identified the polls surveys or groups of individuals or by small values or by high values, and have had an appropriate geotechnical zoning for working separately on homogeneous areas so determined. If an area has an insufficient number of surveys (1 or 2) not allowing the application of the method described in Annex D of the standard EN 1990 can be applied in this area procedure factors correlation £ 3 and £4. NOTE 5 - The procedure called "terrain model" consists in deducing a geotechnical model of the site, optionally divided into homogeneous zones, qb characteristic values k and qs k of the resistance peak and the unit axial friction in the different layers and then applying the general formulas (9.2.4.1) and (9.2.4.2) to determine the characteristic lift the deep foundation or the general formula (10.2.4) to determine the characteristic resistance of the traction deep foundation . NOTE 6- For the procedure known as the "terrain model" when applying a statistical analysis is possible, it is nevertheless difficult. The difficulties are related to the determination of the dispersion plane and the dispersion in the vertical geotechnical strength parameter. Statistical analysis, if conducted, but must at least be based on the principles described in Annex D of the standard NF EN 1990. NOTE 7 - Until the publication of a standard for this type of test, the provisions of the NF P 94-151 standard apply. Recall that in order to use a stake by dynamic impact testing in accordance with clause 7.6.2.4 (1) of the NF EN 1997-1, it must be shown prior the validity of the calculation model by static load tests carried out in the same field conditions for comparable posts.
(2) Methods based on soil tests favor the use of data obtained from pressuremeter and penetrometer surveys (Appendices F and G). It is however possible to use other types of data (number of blows to the SPT, friction angle and cohesion). In this case, the calculation method and the associated model coefficient, which may be used, must be validated by a set of static loading tests of deep foundations made in circumstances reflecting a comparable experience in terms of terrain and type of deep foundation. The calculation method must be of type "direct", that is to say, it directly correlates the results of soil tests
NF P 94-262
to the parameters of the bearing capacity. Furthermore, 8Later during the project phase. The preliminary project phases and project are defined in the NF P 94-500 standard. This choice can be challenged in later phases if the new geotechnical information required (Notes 1 and 2). NOTE 1 - This choice is guided by considerations relating to knowledge of the site and the dispersion and changes in its characteristics (NF Standards EN 1990 and EN 1997). It should not be guided by the more or less conservative level of both methods. NOTE 2 - When a survey was conducted in line with a support, respecting the usual practice, especially regarding the vertical spacing of the tests, we can apply the procedure of the "terrain model" taking as values characteristic values from the survey directly, provided that the site's stratigraphy is regular, that soils are relatively homogeneous and that the bearing surface is limited. In general, we can consider that the survey values apply as such within less than 5 m.
8.6
Deep foundation isolated as a transverse force
8.6.1 Interaction soil-pile in common part of the barrel (1) It should characterize the transverse behavior of a deep foundation isolated by the relationships between the movement and rotation of the head of the element to the shear forces and bending moments applied thereto. (2) It should define two types of reaction laws, one vis-a-vis the demands of long-term application of the force, the other vis-à-vis short-term application of stress (Notes 1 and 2). NOTE 1 - At a given depth, these laws give locally the relationship defined by the function O between the transverse movement 8and the linear density of r forces resulting from this displacement. They are noted:
- r. =O. (8) for the long period of application of stress; - rt = O t (8) for short-term application of stress. NOTE 2 - The recommended procedure for construction of these laws from pressuremeter and penetrometer data is given in Annex I. The proposed laws do not allow a priori to treat the case of cyclic loading.
8.6.2 Act force-displacement for a given type of stress 8.6.2.1 principles (1) In the usual case (Note 1), it is accepted to consider only the first linear portion ( "elastic pseudo") laws, provided (Note 2) to verify, for the shares of combinations, the range of validity the law is not exceeded in the layers that have been taken into account (Note 3). NOTE 1 - In general, the effect of the shock of vehicles or boats on support can not be analyzed from a simplified law and requires considering a nonlinear law efforts - traverse. NOTE 2 - These simplifications assume t hat the allocation of minimum requirements for s oil behavior laws leads to the most severe stresses in any point of the structure. It is therefore appropriate to assess in which cases these simplifications are eligible. NOTE 3 - An intersecting linear law can be substituted for a non-linear law, provided to ensure that the plastic bearing is never exceeded.
8.6.2.2
flexural rigidity
(1) In calculating the stress, the deep foundation bending stiffness is determined with the simplifications allowed by the justification rules reinforced concrete limit state considering for deep concrete foundation provided with a thick sheath of this last by giving it a thickness that must be initially at least 2 mm less the thickness of steel sacrificed corrosion (Notes 1 to 3 and Articles 12.2.6 and 12.3.2). NOTE 1 - These simplifications return to consider what is commonly called sections "raw". NOTE 2 - Remember that this approximation is permissible only insofar reports deformability of the various parts are
8 For one, it is recommended that the choice of the procedure of "model pile" and procedure of the "terrain model" to determine the bearing capacity Rc, k and Rt tensile strength k from soil test results done from the draft. On the other hand, it is imperative that this choice is done
NF P 94-262
not fundamentally changed. NOTE 3 - In the cases covered by section 8.8.4 of this document, for which assesses the effects of lateral movement of the surrounding soil on a deep foundation, we can take into account the adjustments resulting from an elastomeric behavior plastic deep foundation if: — it is not fragile;
— adaptations are compatible with resistance to other stresses.
8.6.2.3
Modeling of ground-based interaction
(1) Generally, it is assumed that the transverse displacements and rotations of the base of a deep foundation will mobilize any reaction from the ground, that is to say, shear and bending moment are zero at level thereof (Notes 1 to 3). NOTE 1 - This model called "free edge" is to overlook friction that can develop between the ground and the base of the deep foundation and the eccentricity of the normal force. NOTE 2 - In the case of a deep foundation anchored in bedrock calculated with conditions called "articulated tip" or "embedded", following the anchorage length, it retains the hypothesis of the "free edge" by mapping bedrock by a high stiffness of soil. NOTE 3 - When the interaction between the field and the base intervenes significantly (bars, well large transverse dimensions, short piles), it is permissible to retain more elaborate behavior laws.
8.7
Behavior of a group of deep foundations
8.7.1 Application domain (1) The requirements of section 8.7 apply only to cases of deep foundations composed of one or more vertical elements of the same section (Note 1). NOTE 1 - If adaptations are necessary to best represent the behavior of the foundation.
8.7.2 axial behavior (1) The axial behavior of a group of deep foundations significantly different from a single deep foundation both as regards on one hand the bearing or its resistance to traction and secondly its axial rigidity. (2) The analysis of the behavior of a group of deep foundation requires taking into account two factors: — the first is related to the effects of the implementation of deep foundations on the ground because of their close spacing; - the second is linked to the loading interaction between the various deep foundation by the geometry of the group considered.
(3) Lift value or traction resistance of a group of n deep foundations differs from n times the lift or the tensile strength of an insulated element. The methods for determining the lift of value or tensile strength of a group of deep foundations are presented in sections 9.3 and 10.3 and in Appendix J. (4) The analysis of the behavior of a group of deep foundations, in terms of travel, based on complex methods (Article 14.3 and Appendix L) based on matching the movements of different piles up the group of deep foundations and soil surrounding. (5) The stakes of a group of deep foundations generally have different stiffness depending on their location within the group. The efforts they experience can then be significantly increased or minus compared to a value corresponding to the case where they would present all the same stiffness.
8.7.3 cross behavior (1) It can be considered that the laws of transverse behavior of n foundation elements placed in the direction of travel does not interfere if the distance was bare naked between them satisfies the following condition (Figures 8.7.3.1 and 8.7.3.2):
NF P 94-262
at > 2max {B; L} (8.7.3.1)
B is the largest width of the elements measured perpendicular to the direction of travel; L is the length of the elements measured in the direction of travel. (2) It can be considered that the laws of transverse behavior of n foundation elements located perpendicular to the direction of travel does not interfere if the distance b naked naked between them satisfies the following condition (Figure 8.7.3.2): b> 2max {B; L}
(8.7.3.2)
B is the largest width of the elements measured perpendicular to the direction of travel; L is the length of the elements measured in the direction of travel. (3) When the bare away bare foundation elements does not meet one of the inequalities (8.7.3.1) or (8.7.3.2), it must define the stress-strain laws taking account of their mutual interaction.
Figure 8.7.3.1 - non-interference condition laws transverse behavior of foundation elements placed in the direction of travel
NF P 94-262
2.5
Figure 8.7.3.2 - non-interference condition laws of transverse behavior of foundation elements located perpendicularly to the direction of travel 8.7.4 Behavior of the bonding pad (1) In calculating the stress, it is acceptable to consider the bonding pad as an infinitely rigid body if it satisfies the following condition: (8.7.4) h is the height of the sole; d is the greatest distance between two founding members of the group.
8.8
Consideration of overall displacements of the ground
8.8.1 principles (1) The overall movement of the ground surrounding a deep foundation generates thereon the stresses which must be given in the justifications (Note 1). NOTE 1 - Given the difficulty fully understand the intensity of these stresses, it should as far as possible to reduce by an appropriate choice of the design of the foundation and the phasing of the work.
(2) The behavior models defined below should be considered when the following conditions are true: —
the foundation is composed solely of identical vertical members connected at the top by a rigid sole,
—
ground displacements are caused by loading up land.
NF P 94-262
In other cases, the foundation must be justified from the most appropriate models, possibly obtained by adapting the principles set out in Articles 8.8.2 and 8.8.3. (3)
8.8.2 Negative friction on a secluded deep foundation (1) A relative soil compaction compared to a deep foundation leads on the perimeter of the latter friction forces directed downward (note 1) which must be considered in the justification. NOTE 1 - The intensity of these constraints called negative friction increases with time, reaching a maximum value at the end of soil consolidation. In some cases it is necessary to consider in addition the creep phenomena.
(2) Failing other models (Note 1), the intensity of the negative friction constraint must be assessed following the directions given in Appendix H. NOTE 1 - simpler but more pessimistic models than those specified in Annex H may be sufficient in some cases.
(3) The sum of the negative friction stresses on the entire side surface of the deep foundation located above the neutral point (Note 1) is the total negative friction on the isolated element. NOTE 1 - The neutral point is the point of the axis of the deep foundation over which the side faces thereof are subject to negative friction. This is theoretically the point of the deep foundation where compaction of the latter is equal to soil compaction.
8.8.3 negative friction on a set of deep foundation elements (1) At other prescribed models default, negative friction Gsn suffered by the foundation element must be assessed following the directions in Appendix H. (2) Generally, the limit resistance Rc; k is estimated by assuming that the axial friction is zero over the entire height of compressible soil, including those located below the determined neutral point for an isolated assumed member (Note 1). NOTE 1 - When the negative friction is low, it is possible to consider the value of negative friction on a group of n deep foundations as the sum of n negative friction values calculated over the deep foundation of the group.
8.8.4 Accumulated negative friction and loads due to variable actions (1) Without more representative model, we must adopt the cumulation rules of negative friction and loads due to variable actions specified in Article 7.3.3. 8.8.5 Behavior of a single element vis-à-vis horizontal displacements of the ground (1) For justification foundations, any horizontal movement of the ground must be characterized by a marked function g (z) that the amplitude of this displacement depending on the depth (Note 1). NOTE 1 - In the absence of representative measurements, the choice of the function g (z) can be carried out following the instructions given in Appendix K.
(2) The behavior of the element must also be modeled on the principles set out in Article 8.6.2 relative to the transverse behavior of a single element by considering, for the study of long-term equity of application, the relative movements between the deep foundation and soil, which is to take as an expression of rv: ° = v {Sv - g )
r v
(8.8.5)
NF P 94-262
(3) When a foundation must be justified vis-à-vis a horizontal displacement of the soil, the amplitude of this displacement is usually large enough to require a non-linear analysis of the behavior. (4) The effect of the actions induced by a horizontal displacement g (z) must be estimated from a MISS method (11.2). The ysp partial factor applies for this type of calculation to equity effects (Notes 1 to 3). NOTE 1 - It is also recalled that in the presence of ground displacements, it is usually the soil-structure interaction laws with maximum features that create the most adverse stress. It is therefore appropriate to choose accordingly Oi and Ov defined in Clause 8.6. 1 (2). NOTE 2 - In the absence of more representative model, the maximum characteristics of the interaction laws are evaluated following the directions given in Appendix K. NOTE 3 - The modeling of a deep foundation may consider the elastic-plastic behavior of the material constituting the (clauses 8.6.2.1 (1) Note 3 and 12.1 (2) Note 1).
(5) Provided the foundation elements are sufficiently distant from each other so that we can consider that their transverse behavior laws do not interfere, the behavior of all of the foundation must be deducted from the principles set out in Annexes I and K (Notes 1 and 2). NOTE 1 - In the current state of knowledge, it is impossible to give general indications of when this condition is not met. NOTE 2 - It is not advisable to in clude elements close together perpendicularly to the ground displacement.
(6) Unless otherwise prescribed, one should adopt the same function g (z) for all elements of the same foundation.
8.9
stakes tests to be performed
(1) Depending on one hand the loading mode of deep foundations (compression or tension) and partly the consequence of class work and geotechnical category stakes tests are to perform to confirm the design parameters considered (Sections 9 and 10). (2) The different types of piles or micropiles tests are defined below (Note 1): — preliminary test: this trial rule until the breaking of the deep foundation must be made when the study phase of the project in order to confirm the feasibility of the proposed work; — compliance test: this trial rule until the breaking of the deep foundation must be done at the beginning of construction before carrying piles so as to control the selected design parameters; — Control test: This test must be performed on the deep foundation of the structure after its completion to a load not exceeding 1.4 times the resistance to almost permanent LIVE deep foundation. NOTE 1 - It is necessary to refer to the appropriate load testing standards for particular define the various load levels and their duration. 9
—
deep foundations are under tension and the design value of the load corresponding to the combination in quasi permanent ELS remains less than 15% of the tensile yield strength of deep foundations (Ft d <0,15Rs);
- to Table 8.9.2: —
deep foundations are under tension and the design value of the load corresponding to the combination in quasi permanent ELS is greater than 15% of the tensile yield strength of deep foundations (Ft d> 0,15Rs).
9 The 8.9.1 and 8.9.2 tables present the tests to be performed according to the stresses being applied to deep foundations. Their use depends on the different cases described below: —
to Table 8.9.1: - irrespective of the load cases, deep foundations are stressed only in compression;
NF P 94-262
(4) When performing tests of conformity or control tests, it should in general to carry out a test 200 for deep foundations made in the case where they are subjected to compressive and a test for 50 deep foundations made in if they are under tension (Note 1). NOTE 1 - The number of tests is to be adapted to soil reconnaissance performed.
(5) For micropiles, it must be accepted equivalence between the results of a compression test and a tensile test.
Table 8.9.1 - Tests to be conducted for deep foundations subjected to compressive and traction (Ft d <0,15Rs) Category Class result Geotech 1
Piles of Class 1 to 7 except the pious category 10 and 15 (Annex A) -
Micropiles or piles and piles class 8 category 10 and 15 (Annex A) Control test
1 2
Conformity test or -
2
Control test
2 3 Preliminary test in clay soils (PI> 20) 3
3
Conformity test
and Control test
Table 8.9.2 - Tests to be conducted for deep foundations under tension (F td > 0,15Rs)
NF P 94-262
Class result
1
Category Geotech 1 2 2
2
Piles of Class 1 to 7 except the Micropiles or piles and piles class pious category 10 and 15 8 category 10 and 15 (Annex A) (Annex A) Conformity test
Conformity test
or
or
Control test
Control test
3 Preliminary test in soils clay (Ip> 20)
3
Control test
3
Preliminary test in soils clay (Ip> 20)
Conformity test
Conformity test
and
and
Control test
Control test
NF P 94-262
9
State-limit lift
9.1 general principle (1)
The lift (Note 1) a deep foundation under axial load should be checked both during the construction phases once the completed facility.
NOTE 1 - It is intended here that resistance vis-à-vis field of compressive stress. The compressive strength of a deep foundation structure is also verifiable in accordance with the appropriate standard to the material that constitutes (Sections 6.4 and 12). It may, in certain project conditions (eg deep foundations embedded in the rock) be lower than the geotechnical bearing capacity. (2)
The checks should be performed in accordance with:
—
of the standard NF EN 1997-1, in particular section 7.6 (Deep foundations under axial load),
—
of this document and particularly sections 8.2, 8.5, 9.2 and 9.3 and chosen according to the calculation model (Appendices F and G).
NOTE 1 - The check is performed according to two calculation approach using the sets of partial factors A1, M1 and R2 defined in Annex C of this document C.2.1 and C.2.2 respectively items for shares and the properties of the land and items C.2.3 and C.2.4 for lift resistance.
9.2 Bearing an isolated deep foundation 9.2.1 principles (1) To demonstrate that isolated deep foundation will support the design load with adequate safety vis-à-vis a break default lift of the ground, the following inequality must be satisfied (Notes 1 to 3) all load cases and load combinations for the ultimate limit state:
Fcd
(9 2 . 1 1 )
Fc; d is the design value of the axial compressive load on the deep foundation; Rc; d is the design value of the bearing capacity of deep foundation.
NOTE 1 - In principle, should be included in Fc, of the weight of the deep foundation and R c d vertical earth pressure at the base of the deep foundation. However, these two terms can be omitted if they cancel approximately. They can not be omitted if - the negative friction is important; - the floor is very light;
—
deep foundation projects above the surface of the ground.
NOTE 2 - For the calculation of loads, we can consider that the laws of axial behavior of foundation elements are not influenced by the presence of neighboring elements. This assumption does not exclude the resistance limits of a foundation composed of n elements can be less than n times the limit load of a single element (group effect) and that the bearing capacity of deep foundations Group is also checking (Section 9.3). The audit focused in this case on two failure mechanisms:
—
the lift fault deep foundations individually;
—
failure to lift deep foundations and soil contained between them, while acting as a block.
NF P 94-262
The lowest values corresponding to these failure mechanisms will b e chosen as the lift calculation. NOTE 3 - When the negative friction is taken into account, the combinations of actions to consider in determining Fc d are specified in sections 7.3.1, 7.3.2 and 7.3.3. It should be recalled that the stresses due to the negative friction were isolated because they do not stack fully with those due to variable actions.
(2) The design value of the RCD bearing must be determined using one of the following formulas (Note 1): R
(9.2.1.2)
cd = Yt Rckl
or R
c d = Rb k / Yb + Rs; k / Y s = Rb; d + R d
(9.2.1.3)
Rc; d is the design value of the lift of the ground in a deep foundation; Rc; k is the characteristic value of the lift of the ground in a deep foundation; Rb; k is the characteristic value of the peak strength of a deep foundation; Rs; k is the characteristic value of the axial friction resistance of a deep foundation; Yt; Yb; YS are respectively partial factors for resistance Rc; k, Rb; k and R k. NOTE 1 - The values of partial factors for pe rmanent and temporary situations and accidental situations are presented in section C.2.3. 10
where Emoy and Emin are correlation factors that depend on the area of investigation, the number of deep foundations tested representative used and draft conditions and are applied respectively (Notes 1 and 2): the average values (R c)
means = (Rs + Rb) = medium (Rb) medium + (Rs) Average
- and minimum values (Rc) min = (Rs + Rb) min NOTE 1 - The values of the correlation factors E are determined from the investigation of surface and correlation factors E 'are given in the tables C.2.4.1 and C.2.4.3, in relation respectively static pile loading tests (E 1 summer 2) And dynamic impact tests (E5and ^ 6). Appendix E explains the calculation of the correlation factor values ENOTE 2 - For structures that have sufficient stiffness and strength to transfer loads deep foundations "weak" deep foundations R + R .. = Mini -
c k = Rb k + Rs; k = '
R
t
(9.2.2)
"resistant", the values of E AVG and Emin may be divided by 1.1 (provided that not Emoy is never less than 1.0), when the drift characteristic values from static loading tests of piles or from tests on soils (NF EN 1997-1).
10 For combinations to seismic AN, the value of the coefficient yt is specified in clause 11 of Section 1 of this document. 9.2.2 Method of calculating from piles tests (1) In the case of the method based on static load tests or method based on dynamic impact testing, the characteristic value of the lift Rc; k must be determined by the following general formula:
NF P 94-262
9.2.3 Procedure "model pile" (1) To calculate the characteristic value R c k of the lift of a deep foundation from the N Rc lift values on N polls a homogeneous area, it is possible to conduct two types of analysis: the one based on the application of correlation factors £, the other based on the application of Annex D of the standard NF EN 1990. (2) The implementation of the method based on the application of the correlation factors £ leads to determining the characteristic value of the lift Rc; k by the following general formula: -min \ ^ c "> Average (Rc
1
c k = Rb k
R
+ R = Rs + Rb + Rs; k = ■
(9.2.3.1) Yr a t 1 E
Y R
d1
£ £ moy and min are correlation factors that depend on the investigation surface of the number of representative soil tests profiles used and the draft conditions and are applied respectively (Notes 1 to 3): the average values (R c)
Average ~ (Rs + Rb) Average ~ (Rb) medium + (Rs) Average
- and minimum values (Rc) min = (Rs + Rb) min- yR; d1 is the value of the partial coefficient model related to the dispersion of the calculation model (Section 9.2.5); its value is presented in Appendices F and G (Note 3). NOTE 1 - The values of the correlation factors £ are determined from the investigation area and correlation factors £ which are given in Table C.2.4.2 (£ 3 and £ 4). Appendix E explains the calculation of the correlation factor values £. NOTE 2 - For structures that have sufficient stiffness and strength to transfer loads deep foundations "weak" deep foundations "resistant", the Avg £ £ values and min may be divided by 1.1 (provided that £ avg is never less than 1.0), when the drift characteristic values from static l oading tests of piles or from tests on s oils (NF EN 1997-1). NOTE 3 - In general, models Calculation fitted on the lift values or tensile strength of the most likely deep foundation and model factor YR d 1is greater than 1 to take into account their dispersion. When not specified, it should ensure that it is included in the calculation method which must then be sufficiently prudent and that we can consider a value equal to 1YR ; d1. 11
Rc; pr is calculated from N Rc lift values following the recommendations of the Appendix D of the standard NF EN 1990 holding a log-normal distribution (4)
For the method called "model pile", the tip of the resistance values Rb and the axial frictional R c, k
R c; pr
(9.2.3.2)
R; d1
Y
resistance Rs are determined from the following relationships: Rb = ABQB and r s = £
(
9
.
2
.
3
.
3
)
and (9.2.3.4)
i
qb means the resistant pressure limit value based on a deep foundation;
11 The implementation of the method based on Annex D of EN 1990 standard is to determine with at least 3 test profiles the characteristic value R c, k from the value Rc; pr according to the following relation (Note 1):
NF P 94-262
qs; i designates the unit axial friction limit value of the deep foundation for the ith field layer. (5)
In order to determine the value of the creep load according to section 14.2.2, it is necessary to determine the peak strength characteristics and axial friction values according
to
the following R
b, k
R k R k
relationships:
R ~ B; moy
R
C; Avg
(9.2.3.5)
R
s; moy
s k
R
C k
R C moy
(9.2.3.6)
9.2.4 Procedure "terrain model" (1) In the case of the procedure of "terrain model", the characteristic value of the lift Rc; k must be determined using the following equations (Note 1):
Rbk = ABQB, k and Rsk = £ (9.2.4.1) and (9.2.4.2) i
qb qs-i qb-k and = ---------- ----------- qsik = -------- ------------- ---- ^ (9.2.4.3) and (9.2.4.4) R; dlYR ; d 2
Y
YR; dlYR; of 2
qb means the resistant pressure limit value based on a deep foundation; qs; i designates the unit axial friction limit value of the deep foundation for the ith field layer; qb; k denotes the characteristic value of the resistive pressure limit at the base of a deep foundation; qs; i; k denotes the characteristic value of unitary axial friction limit of the deep foundation for the ith field layer. YR; d1 is the value of the partial coefficient model related to the dispersion of the calculation model (Section 9.2.5); its value is presented in Appendices F and G; YR; d2 is the value of the partial coefficient related to the timing of the calculation methods described in Appendices F and G of the prior practice (Section 9.2.5).
NOTE 1 - In general, the calculation models fitted on the lift values and tensile strength of the most likely deep foundation and model factor YR d 1is greater than 1 to take into account their dispersion. When not specified, it should ensure that it is included in the calculation method which must then be sufficiently prudent and that we can consider a value equal to 1YR d1. 12
12
The values q b qsi and must be determined from representative values or pressure characteristics pl boundary and penetration resistance qc, in accordance with section
2.4.5.2 of the standard NF EN 1997-1 (Notes 5 and 6 of section 8.5 .2 of this document).
9.2.5 Determination of partial factors yR; yR and d1; d2 (1) The value of YR model coefficient; d1 is related to the dispersion of the calculation model and is therefore different for pressiometric method (Annex F) and the penetrometer method (Appendix G). It depends on whether the deep foundation is stressed in compression or tension (Note 1).
NF P 94-262
NOTE 1 - It allows an average guarantee regarding the characteristic value of the compressive yield strength a default setting of 15% which corresponds substantially the same r ate as the old regulations (Issue 62 Title V and DTU 13.2 ).
The value of yR model coefficient; d2, which applies only to the procedure of "terrain model" is intended to compensate for the deviation related to a qualitative determination of the elementary characteristic values (pl either k or qc k ) (Note 1). (2)
NOTE 1 - The qualitative determination in the implementation process of the "terrain model" results in a dispersion between operators, but on average it seems more optimistic than the statistical determination. As it corresponds roughly to the previous practice, the value of the coefficient y R d2 was rigged so as to find, in conjunction with other factors YR d1 and yt, less the global coefficients security the old rules (Note 2). NOTE 2 - The product of all partial factors, a yR hand; d1, y R, d2 and yt for the procedure of the "terrain model and secondly £, y R, d1 and yt for the procedure "stake model" can significantly meet global safety factors of the old regulations (Issue 62 Title V and DTU 13.2).
9.3
Bearing a group of deep foundations
(1) The lift of a group of deep foundations may be less than the sum of the bearing capacities of deep foundations in isolation. Two reasons are usually cited: — approximation of deep foundations modifies mobilized reactions. This phenomenon mainly affects the axial friction. He speaks with an efficiency this; — the overall behavior of the block formed by the group of deep foundations and enclosed land which may have a lower strength because of its interaction with the surrounding ground.
(2) Vis-à-vis reduction in lift caused by the combination of deep foundations, verification is to check the following inequality (Notes 1 and 2) for all load combinations required: F CGA
e
sd
Fcg d is the design value of the axial compressive load on the group of deep foundations; Rb; d is the design value of the peak strength of a single deep foundation; R d is the design value of axial friction resistance of a single deep foundation; Is the coefficient of efficiency of the group of deep foundations which has only an effect on the terms of axial friction; NOTE 1 - In the absence of more representative method, the coefficient This is determined as shown in Appendix J. NOTE 2 - This check is normally to do that in the case of a group of friction piles. A stake may be considered when floating creep under his charge, the resisting force mobilized fric tion is greater than the force mobilized under its tip.13
Rcg; d is the design value of the overall resistance to compression (lift) of the field for the group of deep foundations.
NOTE 1 - This modeling leads to consider the foundation, following his installation as a shallow foundation, semi-deep or (more often) a single deep foundation of large diameter. The foundation is then justified in accordance with relevant provisions, including when the foundation is subject to negative friction. A method of calculating Rcg d is presented in Appendix J.
13 Vis-à-vis the overall behavior of deep foundation group, it should consider all of the foundation elements and soil they enclose as a monolithic bloc whose cross-section is defined by the smallest perimeter circumscribed and treat block as a single foundation (Note 1). The relationship check is as follows (Notes 1 and 2): Fcg d Z Rcg;d
Fcg d is the design value of the axial compressive load on the group of deep foundations;
(9.3.2)
NF P 94-262
NOTE 2 - This audit verification for the purpose of the overall behavior of pile foundation. It is normally only do that in the following cases:
— group of friction piles; — pile group mobilizing a leading force in a layer of good mechanical strength but above a layer of least resistance. This check does not dispense, where appropriate, to justify vis-à-vis foundation of a displacement limit state required by the scope of structure (calculation of a compaction pile group).
(3) partial factors to be used are those defined to determine the bearing capacity of a single deep foundation (Article 9.2).
NF P 94-262
10 traction state limit 10.1
general principle
(1) The tensile yield strength (Note 1) a deep foundation under axial load should be checked both during the construction phases once the completed facility. NOTE 1 - It is intended here that resistance vis-à-vis field of tensile stress. The tensile strength of a deep foundation structure is also verifiable in accordance with the appropriate standard to the material that constitutes (Sections 6.4 and 12).
(2) The checks should be performed in accordance with: — of the NF EN 1997-1, and in particular Article 7.6.3 (Tensile strength of the field); — of this document and in particular Articles 8.2 (Note 1), 10.2 and 10.3. NOTE 1 - For GEO / STR type checks, verification is performed following the 2 calculation approach using the sets of partial factors A1, M1 and R2 defined in Annex C of this document C.2.1 Articles and C.2.1 respectively for equities and properties of land and sections C.2.3 and C.2.4 for the tensile strength of the field.
(3) The calculation of deep foundations in tension must be compatible with the rules given in section 9, when they apply (Article 10.2).
10.2
tensile strength of a single deep foundation
10.2.1 principles (1) demonstrate that isolated deep foundation will support the traction calculation with adequate security vis-à-vis a break default tensile strength of the field, the following inequality must be satisfied (Notes 1 4) for all load cases and load combinations for the ultimate limit state (10.2.1): FTA
(10.2.1.1)
Ft d is the design value of the axial tensile load on a deep foundation; Rt; d is the design value of the tensile strength of a deep foundation.
NOTE 1 - In some cases, breaking the ground can occur by tearing a ground cone (for example in the case of a deep foundation for broad-based). failure mechanisms to consider are relatively complex. It may nevertheless be considered applying the principles of limit analysis considering logarithmic spirals as fracture surfaces. NOTE 2 - This document does not address the worst case of deep foundations subject to cyclic loading or load reversals. This type of stress can have a detrimental effect on the mobilized tensile yield strength, but is to consider that when the loading conditions can have a severe adverse effect. It is then recommended to perform long piles (that is to say whose length is sufficient to engage the axial friction resistance limit headless mobilize a significant portion of the axial friction near the foot). For such posts, the change in their behavior is much more progressive than the pious behavior "short" (whose length is sufficiently small that are mobilized friction simultaneously top and bottom). After characterization of the initial axial stiffness, the observation of the evolution of this rigidity provides guarantees that can not usually expect from a predicting. This practice is particularly relevant for piles supports a massive rest of a tower crane. NOTE 3 - Where appropriate, tensile strength of deep foundations Group is to check as recommended in Section 10.3. NOTE 4 - For a given method, the model coefficient YR ; Vis-à-vis of the tensile strength can be different from that given to the lift, the dispersion is generally stronger in the case of the tensile strength.
(2)
The design value of the Rtd tensile strength should be determined from the following formula (Note 1): Rtj Rt = k / ys, t
Rt; d is the design value of the tensile strength of the deep foundation;
(10.2.1.2)
NF P 94-262
Rt; k is the characteristic value of the tensile strength of the deep foundation;
Ys t is the partial factor for the resistor Rt; k.
NOTE 1 - The values of partial factors for permanent and temporary situations and accidental situations are mentioned in Article C.2.3.
(3)
For combinations to seismic AN, the value of coefficient ys; t is specified in clause 11 of section 1 of this standard.
10.2.2 Methods for calculating from piles tests (1) In the case of the method based on static load tests or the method based on test dynamic impacts, the characteristic value of the tensile st rength of the deep foundation Rt; k must be determined by the following general formula:
^ ^ Rs means; R) min Rt k = k = Rs MIJ
(10.2.2.1)
1
way
1 E
E
min J
where Emoy and Emin are correlation factors that depend on the area of investigation, the number of deep foundations tested representative used and draft conditions and are applied respectively (Notes 1 and 2):
—
the average value (Rs) means;
—
and the minimum value (Rs) min.
NOTE 1 - The values of the correlation factors E are determined from the investigation of surface and correlation factors E 'are given in the tables C.2.4.1 and C.2.4.3, in relation respectively static pile loading tests (E 1 summer 2) And dynamic impact tests (E5has been). Appendix E explicit calculation of E. correlation factor values NOTE 2 - For structures that have sufficient stiffness and strength to transfer loads deep foundations "weak" deep foundations "resistant", the values of E AVG and Emin may be divided by 1.1 (provided that not Emoy is never less than 1.0), when the drift characteristic values from static loading tests of piles or from tests on soils (NF EN 1997-1).
10.2.3 Method "model pile" (1)
To calculate the characteristic value Rt; k of the tensile strength of a deep foundation from the N tensile strength values obtained on Rt N polls a homogeneous area, it is
possible to conduct two types of analysis: one based on the application of correlation factors E, the other based on the application of Annex D of the standard NF EN 1990.
14
14
The implementation of the method based on the application of correlation factors E leads to determine the characteristic value of the tensile strength of the deep foundation
Rt k by means of the following general formula:
t; k = R k = '
R
Y R
_ Min \ -R (R) mmIE E
^ ■ means
means I
di
NF (10.2.3.1) P 94-262
m
where Emoy and Emin are correlation factors that depend on the area of investigation, the number of deep foundations tested representative used and draft conditions and are applied respectively (Notes 1 to 3):
—
the average value (Rs) means;
—
and the minimum value (Rs) min.
yR; d1 is the value of the partial coefficient model related to the dispersion of the calculation model (Section 9.2.5); its value is presented in Appendices F and G (Note 3).
NOTE 1 - The values of the correlation factors are given in Table C.2.4.2 (E3 summer 4). NOTE 2 - For structures that have sufficient stiffness and strength to transfer loads deep foundations "weak" deep foundations "resistant", the values of E AVG and Emin may be divided by 1.1 (provided that not Emoy is never less than 1.0), when the drift characteristic values from static loading tests of piles or from tests on soils (NF EN 1997-1). NOTE 3 - In general, models Calculation fitted on the lift values or tensile strength of the most likely deep foundation and model factor YR d1is greater than 1 to take into account their dispersion. When not specified, it should ensure that it is included in the calculation method which must then be sufficiently prudent and that we can consider a value equal to 1YR d1. (3)
The implementation of the method based on Annex D of the standard EN 1990 in the case of determining the characteri stic value of the tensile strength Rt k is based on
the same principles as those presented in the Article 9.2.3.
(4)
The value of the axial frictional frictional resistance resistance Rs is determined determined from the following following relationships: relationships:
R
Z
(10.2.3.2)
s=
i
qs; i designates the unit axial friction limit value of the deep foundation for the ith field layer.
10.2.4 Procedure "terrain model" (1) In the case of the procedure of "terrain model", the characteristic value of the axial frictional resistance Rs; k must be determined using the following equations (Note 1): Rs; k = z As.qs, k i
q
g ,,,
s; i; k
Rd; ïYRd; 2
Y
qs; i designates the unit axial friction limit value of the deep foundation for the ith field layer; qs; i; k denotes the characteristic characteristic value of unitary axial friction limit of the deep foundation for the ith field layer.
(10.2.4.1)
(10.2.4.2)
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YR; d1 is the value of the partial coefficient model related to the dispersion of the calculation model (Section 9.2.5); its value is presented in Appendices F and G; YR; d2 is the value of the partial coefficient related to the timing of the calculation methods described in Appendices F and G of the prior practice (Section 10.2.5). NOTE 1 - In general, the calculation models fitted on the lift values or tensile strength of the most likely deep foundation and model factor YR; Di is greater than 1 to take into account their dispersion. When not specified, it should ensure that it is included in the calculation method which must then be sufficiently prudent and that we can consider a value equal to 1YR ; d1.
(2) The values qsi must be determined from representative values or pressure characteristics pl boundary and penetration resistance qc, in accordance with section 2.4.5.2 of the standard NF EN 1997-1 (Notes 5 and 6 section 8.5.2 of this document). 10.2.5 Determination of partial factors yR; yR and d1; d2 (1) The value of YR model coefficient; d1 is related to the dispersion of the calculation model and is therefore different for pressiometric method (Annex F) and the penetrometer method (Appendix G). It depends on whether the deep foundation is stressed in compression or tension (Note 1). NOTE 1 - It allows an average guarantee regarding the characteristic value of axial friction resistance a cut-out rate of 15% which corresponds substantially the same rate as the old regulations (Issue 62 Title V and DTU 13.2 ).
(2) The value of YR model coefficient; d2, which applies only to the procedure of "terrain model" is intended to compensate for the deviation related to a qualitative determination of the elementary characteristic values (pl either k or qc k ) (Note 1). NOTE 1 - The qualitative determination in the implementation process of the "terrain model" results in a dispersion between operators, but on average it seems more optimistic than the statistical determination. As it corresponds roughly to the previous practice, the value of YR coefficient d2 was rigged so as to find, in conjunction with other factors YR d1 and Y t, essentially global safety factors of the old regulations.
10.3
tensile strength of a group of deep foundations
10.3.1 principles (1) The tensile stress on a group of deep foundation causing it to tear can find different origins. It may be due to actions transmitted by a superstructure (in the case for example of a cantilever) or interstitial pressures in rafts (Figure 10.3.1).15
15 In all cases, the verification of a group of deep foundations vis-à-vis tearing of the ULS is to perform as part of the type of checks GEO / STR and UPL. The checks SUCH only concern GEO / STR type checks.
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Ftg d is the design value of the destabilizing force including permanent and variable forces, GSTB d is the design value of the force from the stabilizing permanent loads, VDST; d is the design value of the force induced by the interstitial pressures, Rs; t; d is the mobilizable strength, by the group of deep foundations (Rs; d; g), by the contact between the trimmer and the ground (Rs; d; c) and the contact between the soil block located on the trimmer and the surrounding ground (Rs d; mas). Figure 10.3.1 - deep foundations Group to tearing - type Textual GEO / STR (3) UPL type checking only concerns the failure mechanism corresponding to one block by uprising. GEO / STR type checking is conducted by identifying the most unfavorable failure mechanism for the group of deep foundations (Note 1). NOTE 1 - It is possible that the failure mechanisms type UPL and GEO / STR coincide in some configurations.
(4) To justifications type GEO / STR, if the traction force comes only from pore pressure and to avoid avoid glaring discrepancies design compared to the usual mistakes, actions induced by the stabilizing permanent loads and those induced by pore pressures are grouped. The sum of the two actions is assimilated to a destabilizing action to balance the structure. (5) Conveniently, to check the resistance to tearing of a group of deep foundations, in addition to the UPL type checks (10.3.3), it was agreed to choose between two types of GEO / STR type checks: - type checks "GEO / STR - General case": the destabilizing actions come from forces transmitted by a superstructure (in the case for example of a cantilever) (10.3.1). Referring to FIG 10.3.1, in the case where the calculation value of the action VDST d is negligible Ftg d.
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- type checks "GEO / STR - Case pore pressure" from the destabilizing actions of pore pressures. It is then possible to define a destabilizing actions including actions from under interstitial and actions from dead load stabilizer pressure (10.3.2). Referring to FIG 10.3.1, in the case where the calculation value of the action VDST d is not zero and greater than GSTB d and where the design value of the action Ftg d is negligible before VDST d.
10.3.2 type checks GEO / STR - General case (1)
For this cause, by reference to FIG 10.3.1, the design value of the action VDST d is marginal.
(2)
The type checks GEO / STR in the general case are to verify the following inequality (Notes 1 to 5):
F
G
tg d + Vdst d
stb d ~ Rs; t d
(10.3.2.1)
Ftg d is the value for calculating the axial pulling action on the group of deep foundations, it is dependent on variable actions characteristic values Ft k and permanent Gdst k: * Fg = 1,5Ft.k + l 35Gdst.k
V
(10.3.2.2)
= 1.35V dst k
(10.3.2.3)
dst d
G
bd = 1.0 GSTB k
(10.3.2.4)
Rs; t d is the value of the resistance of the field including the resistance of the group of deep foundations Rs d, g, resistance to soil-trimmer interface Rs d; ch and resistance at the interface between the soil block located above the trimmer and the surrounding soil Rs d; mas Rs; t d = R d, g + R d; ch + R d; mas
NOTE 1 - R s d; gr can be assessed as follows: Rs d; gr N = R network pile d with n the number of deep foundations of the group and Rstake network d the tensile strength of a deep foundation located within the group of deep foundations supposed network (Figure 10.3.2). NOTE 2 - The calculation of Rnetwork pile d R is based on the estimategrid stake which takes into account the interactions between the various deep foundations constituting the group. This is to highlight the most unfavorable failure mechanism: break default axial friction along the deep foundation or ground breaking cone associated with the deep foundation (Figure 10.3.2). For more details, it may be helpful to refer to scientific articles dealing specifically with this subject. Remember that: NOTE 3 - Design values of Rs d; ch and R d; mas can be evaluated in the case of a floor rubbing from the following 1 R
R pieur seau d
AlYRdY.d + v)
R s d; ch
pieur seau
\ P ° V dz
(10.3.2.5) (10.3.2.6)
YY
) V gr gr!
2 (L + 1 R s d; mas
relationship:
YY
J Pavdz
(10.3.2.7)
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(2O ^ \
and P = (l - sin (o) tan - or P = (l - sin (o)) tan (o)
(10.3.1.8)
V3J
depending on whether the contact is of sol -concrete (or steel) or Lgr sol-sol is band width deep foundation; LGR is band length deep foundation; O is the angle of internal friction of the surrounding soil to a critical state; 'AV is effective vertical stress; YO is a partial factor equal 1.25.
NOTE 5 - In the case of a cohesive soil, should be amended accordingly relationships and replace the partial factor THERE0'By the partial factor Yc' equal or à1,25 YCU equal to 1.4.
NOTE 4 - Partial factors Ys; t (YCR or Ys cr) are those used in section 10.2 and 14.2.
Legend: x: length over which the axial friction of the deep foundation can be considered - c: length of the mesh network of deep foundations
Figure 10.3.2 - breaking mechanism of a single deep foundation and a foundation deep network 10.3.3 type checks GEO / STR - Case pore pressure (1) For this justification, by reference to Figure 10.3.1, the design value of the action VDST d is not zero and greater than GSTB d and the design value of the action Ftg d is negligible VDST; d. 16
16 The type of checks GEO / STR in the case of sub pore pressures are to satisfy the following inequality (Notes 1 and 2 and Notes 1 to 6 of clause 10.3.1 (2)): (10.3.3.1) 1
, 35 (V dst k
G
stb k ) + tg d - Rs ; t d F
(10.3.3.2) tan d = 1'5 F t k + 1 , 35Gdst k
F
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Rs; t d is the value of the resistance of the field including the resistance of the group of deep foundations Rs d, g, resistance to soil-trimmer interface Rs d; ch and resistance at the interface between the soil block located above the trimmer and the surrounding soil Rs d; mas Rs; t d = R d, g + R d; ch + R d; mas NOTE 1 - VDST terms k and GSTB k are grouped in accordance with the clause 10.3.1 (4). NOTE 2 - The values of Ft k Gdst and k are almost nil in this configuration.
10.3.4 UPL type checks (1) For this justification, by reference to Figure 10.3.1, the design value of the action VDST d is not zero and greater than GSTB d and the design value of the action Ftg d is néglieagble before VDST; d. (2) UPL type of checks are to verify the following inequality: Vdstd Ftg + d - Gstb.d
(10.3.4.1)
VDST d = 1.0 ^ (10.3.4.2)
fg d = 1,5Ftk + 1,0GdSkk G
tbd = 0,9Gbk
(10.3.4.3)
(10.3.4.4)
(3) The design value of the resistance Rs Action; t d is evaluated based on the recommendations of the clause 10.3.2 (2) Notes 1 to 5. (4) The values of partial factors ys; t are defined as follows: —
A ULS for persistent and transient situations, the values are defined in Table C.3.2.1.
—
A ULS for accident situations, consider the following value: ys; t = 1.15.
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11 Resistance to transverse loads 11.1
General principles
(1) The resistance of a deep foundation subjected to a transverse load (Note 1) should be checked both during the construction phases once the completed facility. NOTE 1 - Security concerns compliance of borderline for the constituent materials of the deep foundation and scope structure and possibly on displacement of deep foundation. However, it is permitted for certain projects (eg for dolphins) to set a ground level of stress not to exceed under transverse stress.
(2) The checks should be performed in accordance with: — of the standard NF EN 1997-1, and in particular section 7.7 (deep foundations under transverse loads) —
of this document and in particular Articles 8.2, 8.3, 11.2 and 11.3 and Annexes I and K.
(3) The effect of the actions in the deep foundation is to be determined by the two calculation approach using the sets of partial factors A1, A2 and M1, M2 as defined in Annex C of this document (Sections C.2.1 and C. 2.2 respectively for equities and properties of land). The structural strength of the deep foundation is verifiable in accordance with the appropriate standard in the material of it. (4) Determination of efforts in the deep foundation and displacement of the latter must be consistent with the checks made to verify the stability of the foundation under axial load (Note 1). NOTE 1 - For example, the same survey profiles and the same properties of a deep foundation structure as those used for verification under axial load are to be taken to determine the forces in the structure and movements as a result of transverse stresses.
(5) The verification of an isolated deep foundation or group of deep foundations must be carried out at ULS and SLS. A ULS, it is necessary to verify that the load case considered (Nd Vd, Md) is the worst (Notes 1 and 2). NOTE 1 - combinations of the worst burdens vis-à-vis the justifications concerning the bending forces are not necessarily the most unfavorable vis-à-vis the justifications shear forces. NOTE 2 - At ELS, it should pay attention to the concrete stress control and crack width especially in cases of quasipermanent load.
(6) The justification under transverse load micropiles must be particularly accurate because of the low ability of these to take this type of loading. In particular, it should be paid to defects eccentricity (Note 1) (Section 12 and Appendix R). NOTE 1 - Different devices as common mountains over three micropiles o r strap beams can be implemented.
11.2
isolated deep foundation
(1) As part of a calculation type MISS on a deep foundation subjected to transverse stresses, it is necessary to define a local interaction law for modeling the interaction between the deep foundation and the ground. The recommended procedures to set these effort-moving type of laws are those based on pressuremeter and penetrometer land properties. They are described in Annex I. Where appropriate (11.3), the force-displacement laws are to be determined taking into account all the piles forming the foundation (group of deep foundations). (2) The local interaction models must take into account the provisions listed in Articles 8.5 and 8.6 (Notes 1 and 2) and degrees of rotational freedom of deep foundations to their connection with the structure (Note 3). NOTE 1 - cyclic loadings are likely to cause an increase transverse displacements and bending forces to which the deep foundation which can not be simply estimated by the current calculation methods. Consideration of the possibility of these movements determines the overall design of structures and motivates periodic observation of actual behavior (with the appropriate use of the observational method - Appendix O).
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NOTE 2 - typically sensitive structures in this are the deep foundations of pylons and monopods deep foundations of cranes or wind turbines when they are not connected by stringers or a trimmer. NOTE 3 - For the calculation of the characteristic value of the effect of actions, links conditions (installation, joint, kneecap) between deep foundation structure and scope must be justified under real conditions deformability of these. It is also allowed to consider the bonding pad as an infinitely rigid body when h> d / 2.5, where h denotes the height of the sole and the greatest distance between two adjacent foundation members.
(3) To demonstrate that an element isolated deep foundation can support a cross computational load at ULS (Notes 1 and 2), it is necessary to simultaneously verify the combinations of the following: — combination with the basic AN for persistent and transient phases; —
Combination accidental ELECTED;
—
combination seismic AN.
NOTE 1 - ELU are covered both those type STR and GEO. NOTE 2 - The justifications for the SLE are pr esented in Section 14.3.2.
(4) For combinations with ELU fundamental for sustainable and transitional phases, the maximum values of local interaction laws used are limited to values corresponding to the level r1 (r1 + rs or if the tangential reaction of deep foundation is regarded) (Annex I). (5) For combinations accidental or seismic ULS, the maximum values of local interaction laws used are limited to values corresponding to the R2 level (or r2 + rs if the tangential reaction of deep foundation is considered) (Annex I) . (6) If the deep foundation or group of deep foundations is subject to an imposed displacement (type g (z), Section 8.8.4 and Appendix K), the partial factors used for justifications at ULS are applied to effects of actions.
11.3
deep foundations Group
(1) The requirements of Article 11.3 apply to deep foundations groups composed of one or more vertical members of the same cross section. NOTE 1 - Where this is not the case, adjustments are necessary to best represent the behavior of the complete foundation.
(2) When the behavior of deep foundations do not interfere (Article 8.7.3), we must define the stress-strain laws according to the principles applicable to individual foundation elements (Notes 1 and 2). NOTE 1 - In the absence of an overall horizontal movement of the ground, if other provisions set by the market, the interaction is evaluated according to the provisions specified in Article I.1 (Annex I). NOTE 2 - In the presence of a horizontal displacement of all the land, if other provisions set by the market, the interaction is assessed according to the principles defined in Article 8.8.5 and the provisions listed in Annexes I and K.
(3) In the absence of an overall horizontal displacement of land (Note 1), when the distance bare bare the foundation elements does not meet one of the inequalities of Article 8.7.3, you must define the stressstrain laws taking into account their mutual interaction (Notes 2 and 3). NOTE 1 - In the presence of horizontal movements of the ground, it is appropriate that the foundation elements are sufficiently distant from each other so that we can consider that there is no interaction. Indeed, in the current state of knowledge, it is impossible to give general indications of when there is interaction. It is particularly advisable to include elements close together perpendicularly to the moving direction of the field. NOTE 2 - The interaction is assessed according to the provisions listed in Annex I.2. NOTE 3 - Numerical methods of finite element or finite difference can be effectively used in the case of rows of closely spaced deep foundation methods where the reaction coefficient prove irrelevant. For modeling in two dimensions,
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special attention should be paid to deep foundations ends where stresses are increased.
(4) In all cases, it is necessary to ensure for all limit states referred to in Section 11.2, the resistance of the surface is sufficient to check the stability of block enclosing all deep foundations.
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12 structural strength 12.1 General principles (1) The structural strength of a deep foundation must be checked both during the construction phases once the completed facility (Section 4.4.3). (2) To demonstrate that the structural strength of a deep foundation is provided with adequate security, you should check that the resistance of the constituent of the deep foundation material is sufficient to withstand the effects of actions (maximum shear, maximum bending moment, normal force maximum) applied to it (Note 1). NOTE 1 - Actions such as the imposed transverse movements are not taken into account in the same way as shares imposing efforts. The rules for building materials generally provide for the consideration of the adaptability of these.
(3) The checks should be performed in accordance with the following provisions (Notes 1 to 3): — the appropriate calculation to standard material of deep foundation (Note 1) and NF EN 1997-1, section 7.8; — of this document and particularly sections 6.4 and 8. NOTE 1 - The design value of the resistance of the material of the deep foundation is to determine, for example, according to DIN EN 1992 for reinforced concrete piles and according to DIN EN 1993-5 for metal stakes. NOTE 2 - The values of cutting times and efforts must be deducted from the combination of the worst actions and in accordance with clause 8.2 (1), the following calculation approach 2 (Table 8.1). NOTE 3 - In accordance with section 8.4, efforts in a deep foundation are to be determined from appropriate calculation model thereof to loading conditions (e.g. from a soil structure interaction model in the presence of lateral force).
(4) Schedule R to define how piles and micropiles design must take into account the effects of implementing tolerances and come and explicit complement to this imposed for this, the execution of pious standards drilled piles and micropiles to discharge.
12.2
Piles or foundation of reinforced concrete
12.2.1 principles (1) The provisions of standard NF EN 1992 apply supplemented by section 6.4.1 of this document. 17 18 (4) If leveled upper bass coppicing to 2 m below the level of the working platform, stakes should be armed. (5) When frames are required, they must be long enough to reach at least the level corresponding to 4 m below the level of cut-off. (6) If rigid reinforcement cages are lowered into the fresh concrete, it must be shown that the desired depth can be achieved without compromising the integrity of the reinforcement cage (eg, from a pile feasibility ) and that the minimum coating fulfilled. (7) The stakes may not be armed in the following cases: 17 The piles or concrete foundation elements must be armed along their length in the following cases: —
they are subjected to tensile forces;
—
they are inclined;
— they support structures such bridges. 18 Sections deep foundation piles and elements subjected to bending and shear forces will not be armed as long as it can be justified by calculation.
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— they remain fully compressed under all combinations of actions; — they do not suffer any damaging stress during the work phases. (8) We can not arm themselves vis-à-vis the shear piles sections that meet all the following conditions (Notes 1 to 3): — the effect of dynamic actions SLE can be ignored; — the effect of cyclical stocks can be ignored; — their diameter is greater than or equal to 400 mm; — shear is checked in accordance with Article 12.6.3 of the NF EN 1992-1-1. However, when at ULS NEd / Ac> 0.3 / ck *, it should be checked: RCP
12.2.2 under normal wear resistance (1) The computational demands to be considered are defined in section 7.3.1 (Note 1). NOTE 1 - If the deep foundation elements are not recognized require vis-à-vis the Main form of stability limit justification (Article 12.3.1), the second order effects are neglected.
(2) The effects of geometrical tolerances are to be integrated in the calculations at ULS (Notes 1 and 2). NOTE 1 - The theoretical consideration eccentricity is the sum of the tolerance of eccentricity by plane at the execution platform and the eccentricity resulting from the tolerance of inclination to the depth of leveling course of coppicing vis-a-vis this platform. NOTE 2 - Annex A deals with the case of c ompression called "centered".
(3) The effects of geometrical tolerances are distributed between the structure and foundations (Notes 1 to 6) (Annex R). NOTE 1 - The distribution of final efforts may be disproportionate rigidities (adaptability). NOTE 2 - favors a local balancing of the forces associated with tolerances without considering a global report on the entire structure. NOTE 3 - The structure is designed and sized to take its share of the effort. NOTE 4 - The load down on the foundations includes the result of this distribution. NOTE 5 - In case of non compliance with tolerances, structure and foundations need to be checked and, if necessary reinforcements are defined. NOTE 6 - Different structural arrangements can limit the consequences of the execution of tolerances:
— Stringers network; — at least three non aligned foundation members below each isolated bearing member; — foundation members staggered in a linear structural member. (4) Taking into account tolerances less than those specified in the implementing standards (EN 1536, EN 1538, EN 12699 and EN 14199) must be specific enforcement procedures, enabling compliance, approved before the start of work.
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12.2.3 Justification vis-à-vis the tangential stresses (1) Should apply the EN 1992-1-1 standard in the case of wishful armed and 12.2.1 clause (8) of this document in the case of wishful unarmed or lightly armed (Note 1). NOTE 1 - In the case of circular elements, for calculating bw (Article 6.2 of the Standard EN 1992), one may consider the square inscribed in the circle where bw = B / 1.4. It should ensure that the longitudinal tension reinforcement are able to withstand the additional pulling force generated by the shear force.
(2) It should firstly maintain shear reinforcement required to right the support and anchorage of longitudinal reinforcement beyond this section and also check that the shear force on support does not exceed VRd, max. 12.2.4 ultimate limit state shape stability (1) The computational demands to be considered are defined in section 7.3.1 (Notes 1 to 3). NOTE 1 - The rationale for a deep foundation vis-à-vis shape stability of the borderline is to consider that in special cases (Clauses 7.8 (4) and (5) of the NF EN 1997- 1). It Examples:
— pile foundation with high clearance, this may result from the design of the foundation or be li nked to scour; — pile foundation low inertia through great heights of land for loose sands or clays for little consistent. NOTE 2 - In general, this is not the only stability piles is analyzed but the overall stability of the foundation and possibly all or part of the structure that it carries. NOTE 3 - The justifications are made in accordance with DIN EN 1992. Without more representative model, interaction laws to consider between the element and the ground are defined in section 8.6.1 for long-term application of stress. 19
12.2.6 Gaines
(1) Taking into account the strength of the eventual metal sheath is allowed for circular piles under the following conditions: — the initial thickness thereof is greater than 2 millimeters, — account is taken of corrosion under the provisions of Article 12.3.2, — unless otherwise required by the market, the welds on site are considered a total interruption of continuity.
(2) When no special connection device is provided to ensure the adhesion between the sheath and the concrete, it is considered that it is perfectly obtained only from a regularization distance equal to 2 x B, counted from the end of the sheath. The rationale for a section located in this adjustment region at a distance x from the end of the sheath, is carried out taking into account a sheath thickness equal to: x
---- e
2B
(12.2.6)
e is the thickness in retaining current section.
19 Including the rationale for micro piles, more realistic models but with a greater degree of complexity can be used if necessary. One can for example refer to the recommendations of the Forever project. 12.2.5 Reservation Tubes (1) Reservation tubes for quality control execution stakes are not included in the resistance of the section. As a simplification, the voids created by these tubes are not deducted from the resistant section of concrete.
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12.3
Piles structural steel metal
12.3.1 ultimate limit state shape stability (1) Without more representative model, the critical Euler Ncr * is calculated taking into account the laws of interaction between the element and the ground set out in Article 8.5.1 for long term application loads ( Notes 1 and 2). NOTE 1 - The rationale for a deep foundation vis-à-vis shape stability of the borderline is to consider that in particular cases. It Examples:
— pile foundation with high clearance, this may result from the design of the foundation or be linked to scour; — pile foundation low inertia through great heights of inconsistent grounds. NOTE 2 - In general, this is not the only stability piles is analyzed but the overall stability of the foundation and possibly all or part of the structure that it carries.
(2) Including the rationale for micro piles, more realistic models but with a greater degree of complexity can be used if necessary. One can for example refer to the recommendations of the Forever project. 12.3.2 steel thickness sacrificed to corrosion (1) When the foundation elements are not provided with a recognized effective protection against corrosion (Note 1), supporting calculations are conducted by neutralizing, over the entire outer perimeter, a thickness sacrificed to corrosion except for falsework. For non completely filled hollow profiles of concrete or mortar, this thickness is also offset on the entire inner perimeter (Note 2). NOTE 1 - In the case of rolled steels for compressive stressed metal construction, it is possible to admit a mortar coating or suitable cement grout may be an effective protection provided if arrangements guarantee a minimum cover 5 cm the slurry used is metered in over 500 kg of cement per cubic meter, with a water cement ratio less than 0.5. NOTE 2 - This applies in particular to all beaten tubular piles, their base is closed or not.
(2) The steel thicknesses sacrificed to corrosion are determined based on the life of the structure (NF EN 1990 and its National Annex) and aggressiveness of the surrounding environment (Section 4 of the NF EN 1993- 5 completed its national annex). (3) In the case of the use of tendons (eg for micro-piles), the establishment of protection against corrosion is required.
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13 General stability 13.1 Overview (1) The general stability of the foundation must be ensured both during the construction phases, once the completed facility. It is also necessary to ascertain, where relevant, the failure mode by general instability of the site during the performance of work and during the life of the worn book (ultimate limit state GEO type - Notes 1-3 ) NOTE 1 - The general stability of the site before work starts, during the construction phase and once the work is completed to demonstrate systematically. The demonstration can not be made by calculation in some cases (Clause 13.1 (2) Note 3). NOTE 2 - The case of deep foundations on steep natural terrain must, in most cases, be subject to a specific study. This document assumes that the structure is built on a site whose initial stability level normally required. Where this is not the case, it is generally appropriate to improve by massive soil reinforcement techniques. NOTE 3 - It is recalled that the calculation of deep foundations in a slope whose initial stability is not normally required level falls Geotechnical Category 3 and the case of deep foundations which aim, in addition to their function bearing, improving the overall stability of the site beyond the scope of this document.
(2) Verification of general stability of the site must be done in accordance with the NF EN 1997-1 and in particular section 7.6.1.1 and section 11 (general stability), supplemented by Article 8.2 of this Document (Notes 1 to 3). NOTE 1 - The overall stability can be checked according to two computational techniques using the sets of partial factors A1, M1 and R2 defined in Annex C, C.2.1 articles, C.2.2 and C.2.5, respectively actions for the properties of the land and their resistance. The value of YRD model coefficient is specified in clause 13.5 (1). NOTE 2 - The overall stability may also be verified according to calculation approach using three sets of partial factors A1 or A2, M2 and R3 defined in Annex C, C.2.1 articles, C.2.2 and C.2.5 respectively for the shares, for the properties of the land and their resistance. The value o f YRD model coefficient is specified in clause 13.5 (2). NOTE 3 - Verification of the initial stability of the site is not always to be done by calculating where deep foundations are established on a substantially horizontal site in geological formations with low dip.
(3) Given the stabilizing character brought by deep foundations, the minimum check (Notes 1 and 2) is to ensure that in the final situation, all the failure mechanisms (Article 13.3) not cutting these are stable ( Figure 13.1). NOTE 1 - It may be necessary, in addition, depending on the stability of the single slope, conduct a specific study of the stability of the assembly consisting of the slope and deep foundations. Given the diversity of cases that can be met, the terms of this study beyond the scope of application of this document. NOTE 2 - It may be necessary also to consider intercepting deep foundations mechanisms. Again, these analyzes are beyond the scope of application of this document.
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Figure 13.1 - Breakthrough Methods for analysis to check the overall stability of a system deep foundation
13.2 (1)
Calculation principle
We should at least check that for any potential failure surface which encompasses the entire foundation, all actions that tend to drag the massive limited by this
surface is balanced by soil shear strength along it . (2)
We must ensure that the following inequality is satisfied for all load cases and load combinations and any potential sliding surfaces (Notes 1 and 2) (13.2):
T ;d R ^st ;d / YR ;d dst
(13.2)
YR d is a partial factor mobilization shear land (Article 13.5); Tdst, d is the design value of the destabilizing effect of actions along the sliding surface studied; Rst d is the design value of the ultimate stabilizing resistor mobilized along the sliding surface studied. NOTE 1 - As part of the approach 2, the Rst value d takes into account the partial factor relating to the strength YR e (= 1.1) and tdst value d takes into account the partial factor on the effect of actions YE(= 1.35). The partial factor YR d intervenes to obtain an overall level of security of the order of 1.5 (YEYR; EYR d). NOTE 2 - Under Approach 3, the Rst value d takes into account the part of the YR resistance factor e (= 1.0) and partial factors relating to the angle of friction(Y9), Cohesion (Yc) and the undrained shear strength (YCu). The partial factor YR d intervenes to obtain an overall level of security of the order of 1.5 (Y ^ YR; EYR d). (3)
It should provide great care in the selection of model calculations (Article 13.3) as well as research in the most unfavorable geometry of the potential slip
mechanisms (Article 13.4).
13.3
Calculation models
(1) Different calculation models, mainly the slices by method called "Bishop" or the so-called "disturbance" may be used. In the case of the method of slices, it should at least check the equilibrium equations moments and vertical forces (Note 1).
NOTE 1 - In a model in installments, if the balance of vertical forces is not subject to verification, inter-slices forces should be taken horizontally.
(2) More complex models based for example on the finite element method or finite difference or the cinematic approach to theory of computation at break can be used, for example to study the cases that fall under the Geotechnical Category 3 (Appendix P) or to identify failure mechanisms in complex terrain conditions, requiring appropriate three-dimensional modeling.
13.4
Failure mechanisms
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(1) It should provide great care to the choice of breaking patterns and looking for their most unfavorable geometry. (2) In the case of a sol of a cohesive soil can generally consider only circular surfaces. (3) When the soil contains layers of very different geotechnical characteristics, it should ensure that the fracture surfaces considered include these features.
13.5
Partial factor yR model d
(1) The yR model coefficient d should be taken equal to 1.0 when using the slices by method associated with circular fracture surfaces as part of the approach 2 (Note 1). NOTE 1 - It is possible to adopt a value less than 1.0 for example 0.9 when the destination of the book just makes it sensitive to deformation.
(2) The yR model coefficient d should be taken equal to 1.2 when using the slices by method associated with circular fracture surfaces as part of the approach 3 (Note 1). NOTE 1 - possibly should be taken to a value less than 1.2 for example 1.1 when the destination of the work makes it insensitive to deformations.
(3) When a calculation model other than the method of slices associated with circular failure surfaces is used, a value adopted for the coefficient y R d, optionally less than 1.0, must be a justification. NOTE 1 - It is appropriate that this justification watch on simple and representative examples, the model used leads to a level of safety comparable to that of the slices per method with circular surfaces.
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14 Justifications to limit state service 14.1
Overview
(1) The dimensioning of pile foundations should be checked vis-à-vis the serviceability limit states (Article 8.3) using the appropriate design situations (Article 7.3 of the standard EN 1997-1 and Section 7 of this document) taking into account the following provisions. (2) It normally be given to the partial factors for serviceability limit states a value of 1.0 to determine the design value of the effect of actions and resistances.
14.2
Land Mobilization by a deep foundation subjected to an axial load
14.2.1 General principle (1) The ground level of stress by deep foundation in service shall be compatible with the axial movement of the requirements of the deep foundation subjected to under axial load. (2) Unless other specifications (clause 14.3 (1)), it is simply necessary to check that the mobilization of ground remains lower, as appropriate, to the design value of the compressive creep load Rc cr d or Rt traction; cr d. The following inequality must be satisfied: (14.2.1.1) d - Rc cr d F
with:
(14.2.1.2)
d - Rt, QC, of
(14.2.1.3)
(14.2.1.4)
c cr d = Rc; cr; k / YCR
R
F
with:
t cr d = Rt; crk / Ys cr
R
Fd is the design value of the ELS of the axial load transmitted by the pile to the ground; Rc; cr; d is the design value of the compression creep load; Rc; cr; k is the characteristic value of the compressive creep load; Rt cr d is the design value of the tensile creep load; Rt cr k is the characteristic value of the tensile creep load; YCR ys and cr are the values of the partial factor respectively on the compression creep load and traction (14.2.1.1 and 14.2.1.2 Tables). (3) The Fd design value of the vertical load transmitted to LIVE by deep foundation ground shall be determined for the case of the most unfavorable load during construction and during operation (Clauses 8.3 (2) and (3 )).20
20 The value of the compression creep load or pulling Rcr k a deep foundation must be determined in accordance with Article 14.2.2. 14.2.2
Creep Charging a deep foundation
(1) It is necessary (Note 1) the compression creep load characteristics values Rc cr k and Rt traction cr k of deep foundation are evaluated from the characteristic values of Rb peak strengths; k and axial friction Rs k by the following relationships:
NF P 94-262
- for the foundation elements implemented without discharge from the floor (Note 2) - for the foundation elements implemented with discharge from the floor (Note 3) (14.2.2.1) (14.2.2.3)
Rccrk = 0.5R + 0.7 Rsk Rccrk = 0.7 Rbk Rsk + 0.7
(14.2.2.2) (14.2.2.4)
R = 0.7 R 's \ k
R crk = 0.7 R
s; k
NOTE 1 - When the static load tests are carried out, it is acceptable to use directly critical characteristics of resistance values measured when relations in this article give conflicting results with the TCR values; m measured during the test. NOTE 2 - Apply the foundation elements whose realization requires the execution of a drilling or excavation whose cross-section corresponds to the nominal section of the element, particularly bored piles, barrettes and the wells. NOTE 3 - Apply the foundation elements set up in the ground by driving or driven, in particular precast piles beaten reinforced concrete or metal, and some pious fully or partially executed in place, including concrete , mortar or grout which enters into its constitution is implemented in a recess made in the ground by pile driving or drilling.
Table 14.2.1.1 - Partial resistance factors ( thereR) For deep foundations - LIVE combinations features Resistance Symbol Values Compression was Was in micropiles)
tension
(including
YCR
0.9
Ys cr
1.1
Table 14.2.1.2 - Partial resistance factors ( thereR) For deep foundations - LIVE quasi-permanent combinations Resistance Symbol Values Compression was Was in tension (including micropiles)
14.3
YCR
1.1
Ys cr
1.5
Movement and deformation of deep foundation
14.3.1 axial load (1) When the travel restrictions imposed by the scope structure, displacement of deep foundation must be assessed (Note 1 and Clause 8.3 (5)). NOTE 1 - This article applies only to projects where worn book is sensitive to movements in an unusual way and where admissible deformations are very low. 21
21 To make this check, it is necessary:
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— First to make an estimate of eligible displacement of deep foundation, imposed by the scope structure (Note 1); — then make a conservative initial estimate of displacement (Notes 2 and 3); — finally justify that movements do not exceed the limit values. NOTE 1 - Eligible travel limits for a pile foundation are to be set for each project prior to the start of the studies. These values are normally set by the client and / or the designer of the scope structure. Indications of admissible deformations of structures are given in Annex N. NOTE 2 - The estimate is not necessarily to be done by calculation, for example in the case of comparable experience (Clause 14.3.1 (3)). NOTE 3 - A conservative estimate can be made according to the recommendations of Schedule L (Article L.2). NOTE 4 - More complex methods, especially in the case of pile groups can be implemented. They can be based on matching the stakes displacement values and ground up.
(3) The design of deep foundation must be justified by a more detailed study with displacement calculations (Note 1) if: — the initial cautious estimate of displacement exceeds the limit values; — we can not prove conclusive comparable experiences. NOTE 1 - An example calculation method is given in Annex L (Article L.3).
(4) Calculations of travel must in this case be made from an appropriate calculation model as specified in clause 8.3 (5) (Note 1)). NOTE 1 - It is recalled that estimation of absolute displacement of a pile centimeter is a reasonable goal and a higher accuracy is generally illusory.
(5) When eligible movements of the deep foundation are incompatible with the precision of displacement calculations should be considered a use of the observational method. 14.3.2 transverse load (1) For combinations with almost permanent LIVE or characteristic, the maximum values of local interaction laws (Note 1) used are limited to values corresponding to r1 level (Annex I). This audit aims to check the suitability of the movement of the deep foundation and scope structure (Note 2) and to limit the creep phenomena. NOTE 1 - It should refer to Sections 8.6, 8.8 and 11.2 and Annex I for the selection of local interaction laws. NOTE 2 - It is important to pay attention to the concrete stress control and opening cracks.
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15 (1)
supporting documents calculations A summary record of supporting calculations and monitoring of work to be done during the construction work must be establishe d in accordance with the NF EN 1997-1
and those of this section.
(2)
The briefing shall provide all necessary information to a third party to monitor, by simple means, the validity of the data used and the assumptions made for the justification
of the different limit states considered. Table 15.1 lists the i nformation should normally be included in the briefing.
Table 15.1 - Project information normally to be supplied in the briefing Object observations Project identification name / number of the file / project status life of the structure to be built
Note 1
class result / Geotechnical Category
Note 1
geotechnical data geotechnical models
Note 2
- the nature and properties of land
Note 3
- hydraulic conditions - reference file of the site reconnaissance
Note 4 Note 5
to the book data and its construction Geometry
Note 6
properties of deep foundations constituents
Note 7
loading conditions Conditions of works (construction phases)
Note 8 Note 9
Notes : (1) The elements on which is based the life of the book, its class result and geotechnical category are recalled. If applicable, the travel criteria to be met are to give. This information normally fall within the specifications of the client. (2) The geotechnical model used for the justification of each completed foundation, including the characteristics values of properties of land and water levels shall be provided. The elements from which it was established are to be indicated (land record recognition, specifications, pumping tests, constructive provisions). (3) Targeted properties are the mechanical properties of the different layers courses (and optionally sealing) and, where appropriate, their physical and chemical properties. (4) The hydraulic conditions affect groundwater and outdoor or open water. (5) The reference, including the type of geotechnical mission (or) file (s) recognition site that has (have) provided the basis for the development of geotechnical models is to provide and possibly the documents supporting the hydraulic assumptions and assumptions used for backfill. (6) Reference (s) level (s) of the work to b uild (plan view type sections, elevation). (7) The properties of the constituent materials of subject piles are those necessary for the justification for their strength and their deformations. (8) The characteristic values of permanent and variable loads applied to the pious book are worn to indicate. These values are normally the subject of the contract specifications and set by the prime contractor for the project. (9) Where appropriate, the construction phases are indicate d.
(3) The briefing must provide the calculations and results that demonstrate the stability and proper functioning of the pile foundation. Table 15.2 lists the information should normally be included in this summary.
Table 15.2 - Information on calculations and results of andoperating stability analyzes to provide normally
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in the briefing 22
Object
observations
calculations Situations / combinations of actions / State-limits Calculation models
Note 1 Note 2
checks ELECTED
Note 3
General stability Lift / Traction transverse stresses structural strength
checks LIVE
Note 4
Mobilization of the subgrade Displacement and deformation of the pile / pile group
Note 5 Note 6
Notes (1) A table is provided, giving, for example, for each pile foundation study, situations, and actions considered combinations and examined limit states. (2) A table is provided, indicating, for example, for each considered borderline: - the method and / or reference software has been used for its verification (eg pressuremeter method with the "zz" software for the verification of the lift, method MISS "in reaction module" with "xx" software for verification of the resistance to transverse loads, method "Bishop" with "yy" software for checking the overall stability of the site; - the calculation principles implemented by the program when appropriate. (3) A summary table is provided giving, for example, for each considered borderline, shares design values or their effects, material properties and resistances. (4) Where applicable, the results of checks carried out at serviceability limit states (see section 14) are also provided. (5) creep load. (6) Depending on the case, it may be horizontal or vertical displacement values (compaction).
22 The summary dossier must include a monitoring plan and monitoring the work, whose importance is based on the complexity of the work to achieve, but the points that require control or measures during construction must be clearly identified . Table 15.3 lists the general principles to be followed depending on the geotechnical category of the project (Appendix P). Appendix O recalls the most important points to be taken into account in the monitoring of works and monitoring the behavior of the structure.
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Table 15.3 - General Principles for the supervision, monitoring and control of work and monitoring of works of behavior geotechnical category Object 3 1a 2 surveillance
ditto 1 + control the properties of embankments and visual inspection, simple control, qualitative
the behavior of the structure
behavior of the structure of the milestones
estimate of the behavior of the structure
Checking the status of the land Control of execution of works
ditto 2 + measurements of ground properties and
site inspection and survey of terrain types in the excavations on the site
OK, no monitoring and control plan
ditto 1 + verification of l and properties with
ditto + 2 additional recognition and study of ground
recognition and additional tests if necessary
conditions affecting sizing
monitoring plan may indicate the work phases
monitoring plan may indicate the work phases
Same 2+ behavioral assessment of the work, based on displacement measurements and analysis taking into account the phases of the work, and if necessary on the basis of measurements of overall
Instrumentation and monitoring work
Ideml + evaluation if any of the behavior of the
displacements of the ground if the observational
simple and qualitative assessment of the behavior
structure, based on a few trips to measures
method is used (observational method)
of the structure, based on visual inspection
selected points and if necessary on measures of all field trips
cited for memory, the provisions of this standard does not apply to Category 1 geotechnical work s.
NF P 94-262
Annex A (informative) The different types of piles and special provisions design
A. (1)
1 The different types of piles Piles are classified according to their following implementation of technical Table A.1 (Note 1).
Table A.1 - Classes and pious categories Class Category
1
2
implementation of technical
Abbreviation
1
single drilled (piles and strips)
FS
2
Drilled mud (piles and strips)
FB
3
Cased drilled (lost ferrule)
FTP
4
Cased drilled (recovered ring)
FTR
5
simply drilled or mud with grooving or wells
FSR, FBR, PU
6
auger drilled hollow simple rotation or double rotation FTC FTCD
7
molded screwed
NF EN 1536 NF EN 12699
8
screwed cased
VT
9
Precast prestressed concrete beaten or
GMP BPR
10
Beat mix (concrete - mortar - grout)
BE
4
NF EN 12699 11
molded beaten
BM
12
Beaten closed steel
BAF
13
Beaten open steel
BAO
14
Profiled beaten H
HB
6 7
NF EN 1536
VM
3
5
Reference Standard
NF EN 12699 NF EN 12699
15
Profiled beaten H injected
HBi
16
Sheet piling beaten
PP
17
Micropieu Type I
M1
18
Micropieu type II
M2
19
Pile or micropile injected IGU guide (type III)
PIGU, MIGU
20
Pile or micropile injected IRS guide (type IV)
SAIP, MIRS
NF EN 12699
1a
8 NOTE 1 - Class 1a Complete Class 1.
EN 1536/14199/12699
NF P 94-262
(2)
This comprehensive schedule performance standards presented in Table A.1, stating in their justification in the context of this document, certain points of the execution
of deep foundations in particular for the four categories of micro piles. (3)
In the absence of comparable experience, should be carried out in early work on a feasibility pile (EN 1536, EN 12699, EN 14199) for evaluating the following technical
implementation Table A.1.
A. 2 drilled piles (Class 1) (1)
The nominal calculating section of the pile is that the drilling tool (Note 1).
Note 1 - It does not include off-profi les in the lift calculations.
A.2.1 simple drilled piles [FS, No. 1] (1)
These piles or these strips are made by implementation of the concrete using a concrete column in a drilling run without retaining walls.
A.2.2 Pius, webs or walls drilled mud [FB # 2] (1) These foundation elements are stakes, webs or walls made by implementation of the concrete using a concrete column in a borehole whose continuation of the walls is provided by a stabilizer fluid.
A.2.3 cased drilled piles, lost ferrule [FTP, # 3] (1) These piles are realized by implementation of concrete using a concrete column in a borehole whose continuation of the walls is provided by a temporary casing dark vibration, threshing or jacking, optionally with sway. The tube is left in place after concreting over all or part of the height of the pile.
A.2.4 cased drilled piles, recovered ferrule [FTR, No. 4] (1) These piles are realized by implementation of concrete using a concrete column in a borehole whose continuation of the walls is provided by a temporary casing dark vibration, threshing or jacking, optionally with sway. This tube is recovered after concreting.
Single piles drilled with grooving A.2.5 [FSR, # 5], with mud with grooving [FBR, # 5] or wells [PU, # 5] (1) The piles of FS or FB family are simply drilled piles or drilled mud realized with grooving (Note 1) before concreting.
NOTE 1 - This fundamental purpose of stripping the optional layer of disturbed soil or clay which adheres to the wall. It does not increase the value of the diameter of the pile considered justification for calculations of the lift or the tensile strength of deep foundations by Appendices F and G.
A.3 Pious drilled auger (Class 2) (1) The nominal section of the pile is that the drilling tool (Note 1 and Section A.10).
NOTE 1 - out profiles are not included in the c alculations.
A.3.1 piles bored Hollow simple rotation [FTC, No. 6]
(1) These piles are made by means of a hollow shaft auger screwed into the soil without significant terrain extraction. The auger is then extracted from the ground without unscrewing while, simultaneously, concrete is injected through the hollow shaft of the auger. The lower part of the auger is provided with a closure system (lost point or pivoting flap) (Note 1).
NOTE 1 - draws attention to the controls to lead in the implementation of this deep foundation technology (6.4.1.1 Tables, F.5.2.1 and G.5.2.1).
A.3.2 piles bored Hollow Double rotation [FTCD, No. 6] (1) The double rotation drill system consists of two superimposed drilling tables. The upper table rotates the auger while th e lower table rotates the tube in opposite direction. Thanks to the relative change, the auger can drill 300 mm in fr ont of the tube. The length of the tube and auger must match for optimal use of the relative change. The tube should be drilled ahead of the auger into granular soils or when drilling foundations remains, piles primary or when Fox phenomena. In contrast, in compact soil auger can drill before the tube.
NF P 94-262
Cuttings back by the turns of the auger and are discharged through the openings on the top of the tube. Reverse rotation of the tube and the auger accelerates the discharge of cuttings. The thus obtained space is filled with concrete flowed through the hollow core of the auger. The auger and tube are removed simultaneously during c oncreting. The result leads to better contact with the adjacent ground.
A.4 screw piles (Class 3) A.4.1 molded Screw piles [VM 7] (1)
The method comprises to penetrate into the ground by rotation and sinking a helical tool, lost or not in the form of a screw topped hollow core column. The feature of the
method is to suppress almost all of the soil which results in a very small volume of c uttings, less than 10% of the theoretical volume made pile (Notes 1 to 3).
NOTE 1 - The finding of very low extraction volume after concreting is proof that drilling was performed correctly and classifies the stake in this category. NOTE 2 - According to the methods, the helical tool is split into two or three parts (Figure A.4.1): —
a more or less smooth central portion whose diameter is the nominal diameter B c pile;
—
a lower truncated cone fitted with a pale outer diameter equal to the nominal diameter of the pile;
—
where appropriate, an upper part equipped as a pale same diameter but with a pitch opposite to that of the lower part.
NOTE 3 - According to the methods, it is possible to perform or not a groove diameter B larger than the nominal diameter Bc and the thickness df may be more or less important with respect to its passage A. This groove can be made for example by a shrink pin or an isolated pale. This step R is calculated from the equation: R = [(v ascent / vratation)] With fever climb in m / min and vrotation in (t / min)]. The thickness df depends on the size of the pin or the thickness of the light. (2)
There are different techniques related to general process (Note 1):
—
with tip-shaped twin-screw partially lost or entirely (left tool in FIG A.4.1) (Notes 2 and 3);
with displacing tool with double screw recovered (right tools in Figure A.4.1); — - with repressing tool provided with a retractable pin.
NOTE 1 - Certain types of screw piles may have once made a constriction or narrowing in diameter. This effect is quantified in the feasibility testing earlier site. NOTE 2 - For some types of piles, concrete work is not done through a hopper but directly to the concrete pump. NOTE 3 - This technique is avoided in the sands without cohesion under table. Feasibility tests are highly recommended to validate the feasibility of the process in these field conditions and to apply the rules for estimating the unit axial friction of Annexes F and G. (3)
A premature refusal with respect to the planned depth when sizing requires justification.
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(A): Barrel with ordinary propeller (b): Barrel with thick propeller Figure A.4.1 - Geometric characteristics of a screw pile A.4.2 Screw
piles cased [VT, No. 8] (1)
It is a screw pile consisting of a lost tip and a lost metal tube which serves barrel.
(2)
The diameter of the pile for the calculation of the tip is the largest diameter of the lost tool. The diameter of the drum for friction or resistance of the concrete is that of the tube.
(1)
This is a stake or precast concrete or steel tube or caisson piles closed at its base beat, vibrated or Verina.
(2)
A premature refusal with respect to the planned depth when sizing requires justification.
A.5 Driven piles closed (Class 4)
A.5.1 Driven piles prefabricated reinforced concrete [GMP No. 9] or prestressed [OPI No. 9] A.5.1.1 Stake beaten prefabricated [GMP] (1) This is a driven pile precast concrete is vibrated or Verina.
A.5.1.2 pile prestressed concrete [OSR] (1) This is a pile consisting of tubular elements slightly reinforced concrete assembled by prestressing prior to beating or vibrating.
A.5.2 metal coated Driven piles [BE, No. 10] (1)
This is a steel metal pile in which the tip comprises a projecting shoe. To progressively sinking by pile driving, vibrating or jacking, a concrete or a mortar, or grout, is sent by one or
more openings opening in the vicinity of the hoof. This low pressure operation is carried out the coating of the steel by vacuum filling the overhang created by the hoof.
(2)
The metal portion of the pile may be a tube, a profile type H or a sheet pile casing. A.5.3 molded beaten Pious [BM 11]
(1) This is a pile achieved by means of a tube closed at i ts base by a discarding-sabot and dark by driving, vibrating or jacking. This tube is then concreted before its extraction. The piles can be armed or not.
NF P 94-262
A.5.4 Piles closed steel box [BAF, No. 12] (1) This steel tube is a pile or a sheet pile casing closed at its base by a plate beat, vibrated or Verine until its stop side. Where appropriate, it may be concrete with or without reinforcement cage.
A.6 Driven piles open steel (Class 5 [BAO, No. 13]) (1)
The steel pile is a tube or sheet pile enclosure open at its base beat, vibrate or light tower until his arrest coast. If necessary, it can be excavated and concrete with or without
reinforcement cages. (2)
A premature refusal with respect to the planned depth when sizing requires justification.
A.7 profiles beaten H (Class 6) (1)
This steel pile is a beat section H optionally equipped cuffs tubes to perform an injection.
23
A.7.1 H beaten [HB, No. 14]
(1) This steel pile is a beat section H, vibrated or Verine until its stop side.
A.7.2 H beaten injected [HBi, No. 15] (1) It is driven piles or vibrated whose barrel is steel. They are equipped with headlines tubes to be injected in GUI mode, or 1RS according to the technologies described in section A.9.
A.8 battered sheet piling (Class 7 [PP, No. 16]) (1)
This foundation is a pile vibrated then beaten, or simply vibrated vérinée until his arrest coast.
(2)
A premature refusal with respect to the planned depth when sizing requires justification.
A.9 micropile (Classes 1a and 8) A.9.1 General (1)
It is known micropile injected a metal frame consisting of tubes, rods, strands or profiles introduced into a drill diameter less than or equal to 300 mm and sealed to the soil by
injection of grout or mortar under pressure more or less high.
NOTE 1 - By extension, it is also referred to as micropile (type 1) a bored pile cased, small diameter less than 300 mm. Drilling is equipped with or without reinforcement and filled with cement mortar by means of a dip tube. The tubing is recovered in the closing head and by keeping under pressure above the mortar. (2)
There are 4 types of micro-piles:
—
Type 1 (Class 17): Type I micropieu is a bored pile cased, small diameter of 300 mm. Drilling is equipped with or without reinforcement and filled with cement mortar by means of a dip tube. The tubing is recovered in the closing head and by keeping under pressure above the mortar.
—
Type 2 (Class 18): Type II is a drilled micropile pile (more rarely beaten) of less than 300 mm diameter. The drill is provided with a reinforcement and filled with a grout or sealing mortar by gravity or under a very low pressure by means of a plunger tube (Note 1).
NOTE 1 - The difference between the type of micropile I and type II is that the latter is always equipped with a frame, which gives it the much greater compressive strength. —
Type 3 (Class 19): The micropile [MIGU] Type III is a drilled pile (more rarely beaten) of less than 300 mm diameter. The drill is provided with reinforcements and an injection system is a tube with sleeves placed in a sheath of grout. If the armature is a metal tube, this tube can be equipped with sleeves and take the place of the injection system. After setting of the grout sheath and breakdown of the sheath slurry, the injection is made in a comprehensive and unitarily (GUI) at a higher injection pressure or equal to the limit of the soil pressure. This technique can be applied to piles with diameters of 300 mm (PIGU). The pile equipped cuffs tubes, is drilled or battered. The drill is provided with a steel profile with an injection system or a tube. In that case, the tube made according to the injection tube. The assembly is installed in a borehole.
23
A premature refusal with respect to the planned depth when sizing requires justification.
NF P 94-262
—
Type 4 (Class 20): The micropile [SIR] Type IV is a drilled pile (more rarely beaten) of less than 300 mm diameter. The drill is provided with reinforcements and an injection system is a tube with sleeves placed in a sheath of grout. If the armature is a metal tube, this tube can be equipped with sleeves and take the place of the injection system. After taking the sheath grout injection is carried out in single or double shutter of a grout or mortar sealing cuff by cuff at a higher injection pressure or equal to the limit of the soil pressure. The injection is repeated and selective (1RS). This technique can be applied to piles with diameters of 300 mm ( SAIP). The pile equipped cuffs tubes, is drilled; The drill is provided with a steel profile with an injection system or a tube. In this case, the tube serves as the injection tube. The assembly is i nstalled in a borehole.
(3)
Other techniques such as gravity bonded spin and settling compensation or self-boring can be used (these techniques are described in Forever). micropile techniques do not
correspond exactly to the 4 types of the above described techniques are considered by default as class 1a micropiles. (4)
The recommended values of grout injected volumes for micropiles IGU 1RS type and are presented in Table A.9.1.
NF P 94-262
A.9.2 Provisions specific to micro piles and piles of category 19 and 20 (1)
The realization of micro piles and piles of class 19 and 20 require:
—
suitable equipment (headlines tubes, valves, injection pumps, etc.) having been subject to controls leading to the development of reports;
—
records continuously different drilling and injection parameters.
(2)
The proper functioning of different devices and continuously recording the various drilling parameters are essential to meet the requirements specified in section A.9.1
particularly in terms of injection pressure. (3)
Improper operation of different devices requires justifications if they are not produced, can lead to reconsider the category of micropieu or stake.
Table A.9.1 - The amount of grout recommended for sealing micropiles
Indicative Terms of application
soils
Vs is the volume of sealing calculated from the drill diameter usual amount of grout injected Vi
Graves
1,5Vs
sandy gravel
1,5Vs
gravelly sands
1,5Vs
coarse sand
1,5Vs
medium sands
1,5Vs
fine sands
1,5Vs
silty sands
1.5 to 2 Vs for 1RS - 1,5Vs for IGU
stringers
2 Vs for 1RS - 1.5 Vs to IGU
clays
2.5 to 3 Vs for 1RS - 1.5 to 2 Vs for IGU
marl
1.5 to 2 Vs for compact layer
Calcareous marl
2-6 Vs or more if fractured layer
Chalk corrupted or fragmented
1.1 to 1.5 if Vs layer finely fissured
altered or fragmented rock
2 Vs or more if fractured layer
Dosage Grout C / E
1.7 to 2.4
1.7 to 2.4
1.7 to 2.4
1.7 to 2.4
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A.10 surfaces and perimeters of the foundation elements (1)
With the exception of cases mentioned in the following clauses, the Ab area and perimeter P to take into account for the calculation of piles limits resistances are determined
from the nominal values of drilling tools for their realization. (2)
For molded screw piles, the calculation of the bearing and strength of the material constituting the pile, the following values of the diameters are considered (Figure A.4.1)
(Note 1): For friction:
—
—
max (Bc; 0,9Bf) if df <5 cm or if R / df> 6
—
Bf if df> 5 cm and if R / df <6
To the point:
—
—
max (Bc; 0,9Bf) if df <5 cm or if R / df> 6
—
max (Bc; Bf) if df> 5 cm and if R / df <6
For the strength of materials: Bc.
—
The nominal diameter of Bc stake is the largest diameter of the tool, regardless of the possible propeller diameter Bf.
NOTE 1 - The size of the rib performed and taken into account in the calculations is checked by release of a pile on the first meter during the feasibility test. (3)
For piles H, beaten metal pile tubes open, and the sheet piles, the section A to consider peak and the friction perimeter P is defined in FIG A.10.1.
(4)
For piles coated (BE), there is necessary to take into account the area and perimeter of the lost platinum.
Figure A.10.1 - Area A cross-sections and perimeter P of tubular piles, piles H, casing and SSP
Appendix B (Informative)
Determination of conventional categories of land
B.
1 conventional categories of land
NF P 94-262
(1)
field classes are defined from the soil identification and their classification according to their nature and their physicochemical properties in accordance with the criteria defined
in Section B.2. We then distinguish the following land classes:
—
clay, silt;
—
intermediate soils (silty sand, sandy, clayey sand loam, sandy clay);
—
sand, severe;
—
chalk;
—
marl and marly limestone;
—
corrupted or fragmented rock.
NOTE 1 - The name of weathered rock or fragmented can group calcareous materials, slate or granite origin. If it is difficult sometimes to set specific limits with loose soil that constitute their final development phase, however this classification to reserve materials with pressuremeter moduli greater than 50 to 80 MPa. NOTE 2 - The following recommendations do not address some soils as carbonated sands, calcareous marl alternations or shales that are difficult to classify and requiring special analysis of their specific behavior that can result in very low resistances. (2)
The aim of this Annex is to classify the surrounding ground following categories defined above, to provide tools to qualitatively assess the behavior of soil and comment on the
results obtained by different methods of calculation presented in the following annexes .
B.
2 Soil classification Elements
(1)
Floors should be identified and ranked based on criteria defined in the figures and tables in this Appendix and NF EN ISO 14688-1, EN ISO 14688-2 and EN ISO 14689-1
(Note 1). This ranking is not only necessary to the design of deep foundation but also the choice of the pious type and adaptation of the technique of execution.
NOTE 1 - The identification and classification of soils and rocks normally fall for a share of NF EN ISO 14688-1 and EN ISO 14688-2 and also the 14689-1 standard. Field classes defined in these standards are not strictly equivalent to those laid in the Table B.2.1 which served to validate calculation models derived from pressuremeter and penetrometer. It is recalled that the problem is not in the differences between the two classifications, but rather to have the information to classify land.24 (3)
The "middle ground" includes a set of fields whose behavior is complex to understand. These soils are made of a mixture of fine and powdery materials which gives
them according to the nature and duration of the stresses to which they are subject, the near soil behavior is consistent or powder.
Table B.2.1 - soil classification according to various criteria
24
The distinction between clay and marl is mainly based on the content of CaCO 3 (Table B.2.2).
NF P 94-262
Classes ground
C lays and s ilts
Ic
Pl * (MPa)
qc (MPa)
(NI, 60)
Very soft to soft
0.0 to 0.50
<0.4
<1.0
<75
farms
0.50 to 0.75
0.4 to 1.2
1.0 to 2.5
Straight very steep
0.75 to 1.00 > 1.00
1.2 to 2 >2
2.5 to 4.0 > 4.0
75
very loose
<0.2
<1.5
<3
cowards
0.2 to 0.5
1.5 to 4
3-8
0.5 to 1
4-10
8 to 25
dense very dense
1 to 2 >2
10-20 > 20
25-42 42-58
Molles altered
<0.7 0.7 to 3
<5 5 to 15
healthy
>3
> 15
tender
<1
<5
Straight
1-4
5 to 15
very steep
>4
> 15
thirsty
2.5 to 4
fragmented
>4
intermediate floors
Ranking realize as indicated figures B.2.1 to (S andy loam, s andy clay, B.2.4 s andy clay)
Moderately dense
S and and g ravel
chalk Marl and limestone marl
Rock
cu (kPa)
Table B.2.2 - Nature cohesive soils - Content of calcium carbonate CaCO3 CONTENT CaCÜ3a 0 - 10%
CLASS FLOOR Clay or silt
10-30%
marl marl clay or silt
30-70%
Marl
70-90%
limestone marl
90 - 100%
Limestone (or chalk b)
CO3 content determined in accordance with NF P 94-048 lk name refers to sedimentary formations of light color, usually white to yellowish, porous and light on which specific laboratory tests, such as, for example, Atterberg limits, can be performed.
NF P 94-262
Figure B.2.1 - soil classification ternary diagram (based on the work of Demolon, 1948)
NF P 94-262
Legend: Y: in MPa Qc peak resistance - X: frottemet Report Rf value% = Figure B.2.2 - Abacus Schmertmann (1978) (Cone skirt) (after Philipponnat and Hubert, 2008) 3
3 P.Philipponnat
Eyrolles.
and H.Bertrand, 2008, Foundations and Structures Land,
NF P 94-262
Zone 1
Clayey soils or sensitive silts purposes
Zone 2
Organic soils and peats
Zone 3
Clay silty clays
Zone 4
clayey silt to silty clays
Zone 5
silty sands to sandy silts
Zone 6
clean sands to silty sands
Zone 7
gravelly sands Sands
Zone 8
cemented sands or dilatant
Zone 9 Soils steep intermediate ends QT : Normalized resistance: QT = (qc-AV0) / o'v0 FR : Normalized friction ratio: FR = fs / (qc-ov0) .100 The solid curves are circles equation: IR = [(3.47-log (QT)) 25 + (1.22 + log (FR))26] 05 Figure B.2.3 - Abacus Robertson (2009) (electric Cone and cone without skirt) 4
4 Robertson
and Cabal, 2009, Guide to Cone Penetration Testing for Geotechnical Engineering, GREGG 26th Edition).
NF P 94-262
Figure B.2.4 - Abacus Baud (2011) 5
5JPBaud,
50 pressuremeters. Flight. 1. Gambin, Magnan and Mestat (ed.) 2005, Presses ENPC / LCPC, Paris.
NF P 94-262
Appendix C (Normative) partial factors for ultimate limit states
C.
1. Preamble
(1) This annex defines the partial factors there for ultimate limit states in persistent or transient situations, to be used for verification of deep foundations under the approach advocated by the two national annex NF P 94-251-1 Eurocode 7 (EN 1997-1 ) (Note 1). NOTE 1 - Some cases may take a justification according to the approach 3 especially in terms of overall stability.
C. 2 partial factors for verification of limit states for structures (STR) and geotechnical (GEO) C.2.1 partial factors for actions (yF) or the effects of actions (yE) (1) For checking the limit states for structures (STR) and geotechnical (GEO) to be applied to shares (thereF) Or the effects of actions (YOU) The following partial factors: —
thereG
—
YQ
for favorable and unfavorable permanent actions;
for favorable or unfavorable variable actions.
(2) The value to give these partial factors is given in Table C.2.1. Table C.2.1 - Partial factors for actions (YF) or the effects of actions (YE) together13 Action
Permed
Variable at the
b A1
Symbol
Unfavorable
YGsup
Favorable
YGinf
Unfavorable
Yusup
Favorable
YQinf
A1at 1.35
A2 1.0
1.0
1.0
1.5
1.3
0
0
value of 1.5 for negative charges is usually reduced to 1.35 for bridges.
relates game approaches 2 or 3 and the game A2 only Approach 3.
C.2.2 Partial factors for soil parameters (uM) (1) For checking the limit states of the structure (STR) and geotechnical (GEO) to be applied to the resistances of the partial factors soils (uM) Include: —
for latangente of frottementinterne angle,
there9'
NF P 94-262
lacohésion for effective,
—
incl'
—
YCU
—
YQU
—
YY for the specific weight
for undrained lacohésion, for laresistance in compressionsimple.
Table C.2.2 - Partial factors for soil parameters ( uM) Ensembleb Soil parameters
Symbol M1
M2
V
1.0
1.25
effective cohesion
incl
1.0
1.25
undrained cohesion
YCU
1.0
1.4
compression
YQU
1.0
1.4
specific weight
YTHERE
1.0
1.0
internal friction angle
(2) The value to give these partial factors is given in Table C.2.2.
C.2.3 Partial resistance factors (y R) to lift and pious tensile strength27 28 Table C.2.3.1 - Partial resistance factors (y R) for piles - sustainable situations and transient
a This factor is applied to tan 9. t 27 For pile foundations and verifications of limit states of the structure (STR) and geotechnical (GEO) to b M1 game concerns the (including approachesR)2Include: and 3 M2 game be applied to soils resistance Partial factors approach.
—
Y for larésistancede tip;
—
Ys for larésistancede frottementaxialsur compression piles;
—
Y for larésistancetotale / combined compression piles;
Ys; tfor larésistancede frottementaxialsur the barrel piles traction. — 28 The values to give these partial factors according to the pious type are shown in Table C.2.3.1.
NF P 94-262
Piles in the continuous flight auger (CFA) Resistance
Symbol
driven piles
bored piles
1.1
1.1
1.1
Ys
1.1
1.1
1.1
yt
1.1
1.1
1.1
Ys; t
1.15
1.15
1.15
Point Yb Was (compression) has
Total / combines (compression) has
Was tension has
at comply
with A.6 tables A.8 of Annex A of EN 1997 -1 - Game R2.
Table C.2.3.2 - Partial resistance factors (y R) for piles - accidental situations Piles in the continuous flight auger (CFA) Resistance
Symbol
Point
driven piles
bored piles
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.05
1.05
1.05
Yb
Was (compression) Ys Total / combines (compression)
Was in traction
yt
Ys; t
C.2.4 correlation factors for determining the characteristic lift resistance and the pile tensile strength (1)
For checking the limit states of the structure (STR) and geotechnical (GEO) is to be applied
correlation lesfacteurs E 'shown in tableauC.2.4.1pour determine laresistance characteristic piles axially loaded from static pile load tests: —
£ i 'for the average values of resistors mesuréeslors desessais chargementstatique,
—
E2'For minimum resistance values of mesuréeslors desessais chargementstatique.
NOTE 1 - These coefficients (E1 and E2 ') are needed to calculate the E correlation factors which include the surface of geotechnical investigations. (2)
For checking the limit states of the structure (STR) and geotechnical (GEO) is to be applied
correlation lesfacteurs E 'shown in tableauC.2.4.2pour determine laresistance feature loaded piles axially from tests on soil: —
E3 'to the average values derived resistances of test results on soil,
—
E4 'for minimum values derived resistances of test results on soil.
NOTE 1 - These coefficients (y and E4') Are needed to calculate the E correlation factors which include the surface of geotechnical investigations. An example is given in Appendix E. (3)
For checking the limit states of the structure (STR) and geotechnical (GEO), the correlation factors to be applied E 'shown in Table C.2.4.3 to determine the characteristic
resistance of axially loaded piles, starting from dynamic impact on the piles tests;
NF P 94-262
—
E5 'to the average values derived resistances results of dynamic load tests,
—
E6 'for minimum values derived resistances results of dynamic load tests.
NOTE 1 - These coefficients (E5', And E6') are needed to calculate the E correlation factors which include the surface of geotechnical investigations.
Table C.2.4.1 - Correlation Factors E 'to derive characteristic values partird'essais static loading piles (n number of piles tested) E 'for n =
3 1
E1 '
E2 '
at
at
1.40
at
1.40
4
>5
1.10
1.00
1.00
1.00
2 1.30 1.20 1.05 1.20
conform to the table A.9 of Annex A of the NF EN 1997-1.
Table C.2.4.2 - Correlation Factors E 'to derive characteristic values from derésultats testing on soils (n number of test profiles) E 'for n =
es'
E4 '
at
3 1
2
at
1.40
1.35
1.33
at
1.40
1.27
1.23
4
5
7 10
1.31
1.29
1.27
1.25
1.12
1.08
1.15 1.20
conform to Table A.10 in Appendix A of EN 1997-1 standard.
a G
values in this table are applicable for dynamic impact testing.
b The
values of G may be multiplied by a model factor of 0.85 when using the dynamic impact tests with calibration signal (EN 1997-1).
c should
NF P 94-262
be multiplied by the values of C a 1.10 factor model when using a threshing formula with measurement of quasi-elastic displacement of the pile head on impact (DIN EN 1997-1).
d the
values of C must be multiplied by a model factor of 1.20 when u sing a pile driving formula without measuring the quasi-elastic displacement of the pile head during impact S 'for(NF n EN 1997-1) .> 2 >5 > 10 > 15 > 20
e if
there are different stakes in the foundation, it is necessary to consider separately the i, aowhen selecting 1.50 the number 1.45 1.40 U similar pile groups n of piles to be 1.42 tested (EN 1997-1). It'
1.50
1.35
1.30
1.25
1.25
Table C.2.4.3 - Correlation Factors Ç 'to derive characteristic values impact partird'essais dynamiquea' b 'c' d 'e' (n - number of piles tested)
C.2.5 partial resistance factors of land (y R) for overall stability (1) For the analyzes of the overall stability of piles structures based on (GEO) to be applied to the resistors land, partial factor (y R e) shown in Table C.2.5.1.
Table C.2.5.1 - Partial factors for the resistance of the land (y R) for overall stability Together
Resistance
Symbol
R2
R3
1.1
1.0
overall shear strength on a fracture surface YR e
NF P 94-262
C.3 partial factors for the verification of the ultimate limit state overall uplift (UPL) C.3.1 Partial factors (yF) for actions (1) For the verification of the overall uplift limit state (UPL), to be applied to the actions Partial factors (yF) Include: —
YG; dstunfavorable permanent pourlesactions destabilizing,
—
YG; stbstabilizing favorable permanent pourlesactions,
—
Yo; dst pourlesactions destabilizing unfavorable variables.
(2) The value to give these partial factors is shown in Table C.3.1.1. Table C.3.1.1 - Partial factors for actions (yF) Action Symbol Value Unfavorable ermanent at Favorable b
YG; dst
1.0
YG; stb
0.9
YQ; dst
1.5
Unfavorable variable at
at b
destabilizing
stabilizer
C.3.2 Partial factors for soil parameters and resistances (1) For the verification of the overall uplift limit state (UPL), when considering resistance Rd uprising, should be applied to soil parameters and resistances to the following partial factors: —
Y 'to the tangent of the angle of internal friction,
—
Y'pour effective cohesion
—
YCU to the undrained shear strength,
—
Ys; t
—
ago for the resistance of the anchor.
for piles tensile strength,
(2) The value to give these partial factors is shown in Table C.3.2.1. Table C.3.2.1 - Partial factors for soil parameters and resistances
NF P 94-262
Soil parameters
internal friction angle effective cohesion
Symbol
V
at
Value
1.25
including '
1.25
undrained cohesion
YCU
1.40
tensile strength of a stake
Ys; t
1.40
Ya
1.40
tensile strength of an anchor at This
factor is applied to tan ^.
NF P 94-262
Appendix D (Informative)
e
Determination of the height equivalent embedding D,
D.
1. Preamble
(1)
This annex defines the calculation of the equivalent installation height by using data from semi-empirical pressiometric type or penetrometer.
(2)
From Greatness is information for distinguishing different types of foundations: shallow foundation on the one hand and semi-deep on the other foundation. In general, we
define the equivalent embedding From / B (with B the smallest width of the foundation) and retained values are: —
De / B <1.5: the foundation is called superficial and in general the side reactions (friction on the side faces, stop) are neglected in evaluating the lift;
—
1.5
D.
2 Determination of equivalent installation height From
(1) The equivalent installation height requires the prior calculation of the equivalent pressure sharp boundary pie * or resistance equivalent qce smoothed penetration. The following relationship s can then be applied:
(D.2.1)
(D.2.2) d is usually set equal to 0 unless there are l ots of very poor surface characteristics which it i s desired to ignore.
118
NF P 94-262
Calculating the value of the lift and / or resistance of tractiond'une deep foundation - Overview and Examples
E. Overview 1 - Diagram of calculating the value of the lift and / or tensile strength of a deep foundation (1) For estimation of the value of calculation of the bearing Rc d and / or Rt tensile strength d of a pile from the method based on the piles test or procedure of the " model pile, "the block" diagram calculation of the deep foundation bearing capacity value "may hereinafter be used to properly i mplement the various partial factors.
E. (1)
2 Calculation of coefficients £ To calculate the value of the lift and / or tensile strength of a deep foundation piles from tests it is necessary to use correlation factors C1 or C2. Next the surface S the
value comprising the points where the stake tests were performed and where the projected deep foundations must be implemented, correlation factors C1 or C2 vary. Formula (E.2.1) can be used. a is the coefficient corresponding part for i varying from 1 to 4; S is the area of geotechnical investigations for the study site and should be included in a homogeneous geotechnical zone (Clause 6.2 (2)); N is the number of test piles or soil test profiles on the surface under consideration;
Sref corresponds to a decision reference surface equal to 2500 m
29
a, {N, S) = 1 + [£ '(N) -1]
S
(E.2.1) S ref
(3)
The use of correlation factors requires some rules of "good" implementation:
—
the S value used in the calculations should not be less than 625 m for the determination of the coefficients a and a2 and 100 m2 for determining the coefficients a3 and a4;
—
the maximum area of geotechnical investigations is equal to 2500 m;
—
the smallest length of the surface geotechnical investigations should not be more than two times less than the greatest length L of the surface. In other words, for a rectangular area investigation, the ratio L / W between the length L and the width should not be greater than 2.
29
To calculate the value of the lift and / or tensile strength of a deep foundation
from soil testing profiles, it i s necessary to use factors corrélationou Ç
4.
Next the
S surface value comprising the points where the soil profiles tests were performed and where the projected deep foundations must be implemented, correlation factors C3 or C4 vary. Formula (E.2.1) can be used.
NF P 94-262
NOTE 1 - The (4)
Appendix E
coefficients 4 'are shown in the tables in Appendix C (Table C.2.4.1 and C.2.4.2). (Informative)
Various application examples (Notes 1 to 6) of this relationship are presented below for the coefficients 43 or 44.
NOTE 1 - Example 1: 1 support (L = 10 m, L = 3 m) - 1 poll The l
real lmini
S
S NOT 43 44
10 m 3m 30m2 5m 50 m2 1 1.08 1.08
NOTE 2 - Example 2: 5 supports (L = 10 m, the m = 3) distributed over 50 m - 3 surveys the right of center supports 3 The 50 m l 10 m
real lmini
43
500m2 25 m 1250 m2 3 1.23
44
1.16
S
S NOT
120
NF P 94-262
The l
25 m 8m
real mini
200 m2 12.5 m 312.50 m2
S l
S
NOT 1 2 1.14 1.12 ^3 1.14 1.10 ^4 NOTE 3 - Example 3: 1 support river viaduct (L = 25 m, l = 8 m) NOTE 4 - Example 4: Construction (30 mx 20 m) The l
real lmini
600 m2 15 m 600 m2
S NOT
1
2
1.20 1.17 1.20 1.13
3
5
1.16 1.11
1.14 1.07
NOTE 5 - Example 5: Construction (50 mx 30 m) The l
real lmini
S
^4
NOTE 6 - Example 6: Construction (100 x 30m)
7 1.13 1.06
10 1.13 1.06
50 m 30m 1500 m2 25 m 1500 m2
S NOT
1.12 1.08
30m 20 m
S
^3 ^4
3
1 2 1.31 1.27 1.31 1.21
3
5
1.26 1.22 1.18 1.12
7 1.21 1.09
10 1.21 1.09
NF P 94-262
The l S ist
100 m 30m 3000 m2
|mini
50 m 5000 m2
S NOT ^3 ^4
122
1 1.57 1.57
2 1.49 1.38
3 1.47 1.33
5 1.41 1.21
7 1.38 1.17
10 1.38 1.17
NF P 94-262
Figure E.1 - Diagram of calculation of the bearing of a deep foundation
NF P 94-262
Appendix F (Normative)
Lift limit and tensile yield strength from the method pressiometric
F. (1)
1. Preamble This annex gives the rules to determine determine the limit bearing bearing and the tensile tensile yield strength strength of a deep deep foundation isolated under under axial loading from the tests tests in place
pressuremeter "Ménard" and in particular the pressure limit pressiometric pi. (2)
This method method is fully fully applicable applicable for soils (Note 1) and field classes classes specified specified in Annex B.
NOTE 1 - specific aspects of behavior of rocks outside the scope of this document. It should be appreciated in what cases a foundation called "the rock" can be justified by the proposed methods and in what circumstances the use of specific methods of rock mechanics is required. (3)
This comprehensive comprehensive method Sections Sections 9, 10 and and 14 of this document document dealing dealing with justifications to to respectively the the ultimate limit states and serviceability serviceability limit states for for
deep foundation under axial loading in compression and tension.
F.
2 Model Coefficients
NF P 94-262
Appendix F (Normative)
Lift limit and tensile yield strength from the method pressiometric
F. (1)
1. Preamble This annex gives the rules to determine determine the limit bearing bearing and the tensile tensile yield strength strength of a deep deep foundation isolated under under axial loading from the tests tests in place
pressuremeter "Ménard" and in particular the pressure limit pressiometric pi. (2)
This method method is fully fully applicable applicable for soils (Note 1) and field classes classes specified specified in Annex B.
NOTE 1 - specific aspects of behavior of rocks outside the scope of this document. It should be appreciated in what cases a foundation called "the rock" can be justified by the proposed methods and in what circumstances the use of specific methods of rock mechanics is required. (3)
This comprehensive comprehensive method Sections Sections 9, 10 and and 14 of this document document dealing dealing with justifications to to respectively the the ultimate limit states and serviceability serviceability limit states for for
deep foundation under axial loading in compression and tension.
F. (1)
2 Model Coefficients Values yR model model coefficients; yR d1 and d2 are shown in the the table F.2.1. The value of yRd1 yRd1 model coefficient varies varies depending on whether whether the pile is under under compression
or tension (Notes 1 to 3).
NOTE 1 - YR model coefficient d 2 does not apply to the procedure of "model pile." NOTE 2 - The model coefficient YR d1 for piles anchored mainly in chalk is equal to 1.4 because of the difficulty in properly understanding the mechanical behavior of geological chalk that can present certain specific rheological on the plane (thixotropy). NOTE 3 - The piles of Class 10, 17, 18, 19 and 20 require the use of injection techniques whose mastery is complex. The performance in terms of compressive strength and tensile strength of these pious categories are very variable. The model coefficient to quantify the dispersion calculation model related to these techniques has been increased and brought to a value equal to 2.0.
124
NF P 94-262
Table F.2.1 - Value of model coefficients for the pressuremeter method Procedure "model pile" (use \ coefficients or Annex D of the standard EN 1990) Procedure "terrain model" Procedure "terrain model"
Y
YR; d1
R; d1
Compression
Traction
1.15
1.4
Y
Y
R; d2
R; d2
Compression
Traction
Piles unanchored in Class 1 to 7 out of chalk piles category 10 and 15
1. 1
Stakes anchored in the class of chalk 1 to 7 out of piles category 10, 15, 17, 18, 19 and 20 1.4
1.7
2. 0
2. 0
Pile category 10, 15, 17, 18, 19 and 20
F.
3 limits Resistance
(1)
This article defines the procedures for determining the limit Rc Rt lift and traction resistance limit of a single deep foundation made in line with a survey pressiometric.
(2)
The lift limit compression Rc of a single deep foundation must be determined from the following general expression (Notes 1 and 2):
Rc = Rs Rb +
(F.3.1)
Rc is the value of the lift of the deep foundation; Rb is the value of the peak strength of the deep foundation; Rs is the value of axial friction resistance of the deep foundation (Note 2);
NOTE 1 - The methodologies for calculating Rb and Rs are specified in Articles F.4 to F.5. NOTE 2 - The friction engagement height does not necessarily correspond to the full height of the element in the soil. This is particularly the case for deep foundations having a double lining or deep foundations subject to negative friction.30
30
The Rt tensile yield strength of a single deep foundation must be determined from the following general expression (Note 1):
rt = RS
Rt is the value of the land tensile strength; Rs is the value of axial friction resistance of the deep foundation;
(F.3.2)
NF P 94-262
NOTE 1 - The calculation methodology of Rs is specified in Section F.5.
4 advanced Resistance
F. F. (1)
4.1 General Principle The limit force had mobilized after tip of a deep foundation must be calculated from the following general expression:
Rb = Mb
(F.4.1)
Rb is the value of the peak strength of a deep foundation; Ab is the area of the base of the deep foundation (Section A.10); qb is the value of the burst pressure of the ground under the pile base (F.4.2).
F.
4.2 break ground pressure
(1) Except in special cases (Note 1), breaking the pressure value of the land under the base of the deep foundation must be calculated from the following general expression:
(F421)
qb = kpPle
kp is the pressiometric lift factor taking into account the provisions of Article A.10; * ple is the net equivalent limit pressure.
NOTE 1 - Where appropriate (Clauses 9.2 (1) Note 1 and F.3 (1) Note 1), it should consider the total vertical qo existing stress in the ground at the base of the pile at work (Note 2) and apply in this case the following general expression: *
qb = qo + k PPU
(F.4.2.2)
NOTE 2 - The total vertical stress qo is to consider the situation in which the foundation is justified disregarding it. (2)
The value of kp lift pressiometric factor must be determined from the values F.4.2.1 table depending on the nature of the training in which is the base of the deep foundation,
its implementation mode (Note 1) and its recess.
NOTE 1 - The experimental results currently available do not allow to identify a possible influence of the shape of the cross section of the pile. 31 32 33 p * (z) is the profile of net pressure limits considered representative (Note 3); *
ple is the "net equivalent limit pressure" (Note 3);
-i D + 3a - {P * (z ¥ z Pie = b + 3a db
31
In the case of a homogeneous formation carrier (Notes 1 and 2), the pressure value sharp boundary * equivalent pe must be determined from the following general expression:
(F.4.2.3)
NF P 94-262
D is the depth of the foundation;
B is the width of the pile;
h is the height of the pile contained in the carrier formation;
a = max-j ^ O ^ I (F.4.2.4)
b = min {a; h } (F.4.2.5)
NOTE 1 - an indication, a formation can be considered uniform if it is composed of a unique nature of soil and if the maximum pressure measured in this training does not exceed twice the minimum limit pressure. NOTE 2 - If not, it should make a careful choice of the representative value of the net equivalent limit pressure, remembering that if there is a strong bedrock near the tip of the piles, it is still possible to deepen the level of the tip to reach it. NOTE 3 - The net pressuremeter limit pressure has to be according to the standard ISO 22477-5 prNF IN 34 Until its release provisions of the NF P 94-110-1 standard apply. (4)
The bearing capacity factor depends on the Def effective installation height defined by the following rules:
J p * (z) dz
1
D ef
*
dh
D
(F.4.2.6)
Pe
hD denotes a length of 10B.
(5)
The actual installation is equal to Def / B where B is the smallest dimension of the foundation (Note 1):
—
where the number underrun Def / B is greater than 5: kp (Def / B) = kpmax;
—
where the number underrun Def / B is less than 5 kp (Def / B) = 1.0 + (kpmax-1.0) (Def / B) / 5.
NOTE 1 - At least the effective embedding in the support layer is taken equal to 3 diameters or 1.50 m for pile diameters larger than 0.5 m. If the company special foundations can ensure the proper execution of the installation of advanced stakes in the carrier layer or by taking samples or by bit employment, or by the use of sampler then this anchoring can be reduced to a minimum value of 0.50 m. (6)
The intermediate soils (Appendix B) can be considered as either clay or silt or as sand or serious. In principle, intermediate floors are designated by the following terms: silty
sand, clay, sandy loam sand, sandy clay. This is the first term of these expressions that defines soil behavior. Thus, the in termediate floors can be classified as follows:
—
a silty sand and loamy sand or sand belong to the serious category;
—
a sandy loam and sandy clay belong to the category clay or silt.
34 In preparation for.
NF P 94-262
Table F.4.2.1 - bearing factor value pressiometric kpmax for installation actual Def / B> 5 Ground
Clay soils % CaCO3 <30% intermediate Limon intermediate Stake class (c) Sand Grave floors
Chalk
Marl and calcaire-
weathered rock marl and fragmented (at)
1
1.15 (b)
1.1 (b)
1.45 (b)
1.45 (b)
1.45 (b)
2 3
1.3
1.65
1.55
3.2
1.6 2.35
1.6 2.10
2.0 2.10
4
1.35
3.1
2.30
2.30
2.30
5#
1.0
1.9
1.4
1.4
1.2
6#
1.20
3.10
1.7
2.2
1.5
7#
1.0 1.15 (b)
1.0 1.1 (b)
1.0 1.45 (b)
1.0 1.45 (b)
1.2 1.45 (b)
8
(#) To the type of pious BAO, HB and PP, implemented by vibrodriving Instead of driving, it is necessary to make a at 50% rebate on the kp factor. (A) kp value for the altered and fragmented rock must be taken equal to that of the unconsolidated formation of the table at which the material concerned is most closely related. If healthy rocks, it should (F.1 (2) Note 1) to assess whether a justification based on the methods of this Annex F and pessimistic evidence is sufficient, or whether to use the specific methods of the rock mechanics. (B) For micropiles, advanced resistance is not normally taken into account. (C) It is appropriate to refer to Article A.10 for the selection of areas and piles of areas to be considered in the calculations. (D) Other kpmax values may be used provided they meet the conditions of clause 9 of the section 1.
5 axial friction resistance
F.
F.
5.1 General principle
(1) The mobilisable limit force by axial friction on the respective height of the shank of the deep foundation must be calculated from the following general expression:
ps = fq (z ') Dz
Rs
(F51)
Rs is the value of the axial friction resistance of a deep foundation; Ps is the perimeter of the pile was (Section A.10); D is the length of the foundation contained in the ground (Note 1); qs (z) is the value of the unit axial friction limit in the z -dimension (Article F.5.2);
NOTE 1 - The height Ls when the axial friction is mobilized does not necessarily correspond to the full height of the element in the soil. This is particularly the case of piles with a double lining or to the piles subjected to negative friction. In the latter case, it should if necessary to define two values of Rs, one for compression and one for traction.
F.
5.2 Friction unit axial limit qs
NF P 94-262
(1)
The value of the unit axial fricti on qs limit at depth z must be determined depending on the nature of the terrain, the implementatio n mode of the pile and net limit pressure
value measured at the same depth, from the F tables .5.2.1 and F.5.2.2 and F.5.2.1 figure. (2)
The value of the unit axial boundary friction at depth z is determined from the following relationship:
qs(Z) = at p, had solf-ground [p * I (Z ) j
(F
.5.2.1)
(F
.5.2.2)
pl * (z) is the limiting pressure at depth z; a pile, soil is a dimensionless parameter which depends both on the type of pile and soil type defined in the table F.5.2.2; fsol is a function that depends only on the soil type and values of p ^ (3)
The fsol functions are defined for different types of soil by the following equations (Figure F.5.2.1)
) fsol (pl) = (APL + b X1 - e - Cl
The parameter values are defined in Table F.5.2.2 for limiting pressure pl * values in MPa. (4)
For low pressure limits (less than 0.2 MPa for clays and silts and less than 0.3 MPa for sands), it must be ensured that the friction is considered unitary axial perennial. It is
therefore necessary to conduct a special study to justify this hypothesis (eg, demonstrating the absence of negative friction induced by overload or changes in groundwater level). (5)
Independently of the curves of FIG F.5.2.1 and F.5.2.2 general relationship of the equation defined on the basis of experimental measurement s, it must be ensured that the
unit axial friction values determined are not superior to those defined in table F.5.2.3. (6)
For deep foundations of large length listed in Table F.5.2.1 (sign ##), with the corresponding soil is used an 50% reduction on the friction value derived from the application of
the various tables and figures on pile sections located at 25 m or more above the tip.
NF P 94-262
Table F.5.2.1 - Choice of apieu.soi values - Method pressiometric Clay Marne and corrupted or soils N Abbreviatio implementation % CaCO3 <30% Calcairefragmented O n Chalk Marly intermediate Limon rock of technical T intermediate Sand Grave floors FS ## 1 1.1 1 1.8 1.5 1.6 single drilled (piles and strips) 2
FB ##
3
FTP
4
FTR
5
6
Drilled mud (piles and strips) Cased drilled (lost ferrule) Cased drilled (recovered ring)
1.25
1.4
1.8
1.5
1.6
0.7
0.6
0.5
0.9
-
1.25
1.4
1.7
1.4
-
FSR, FBR, simply drilled or PU ## mud with grooving or wells Continuous flight FTC, CRF auger drilled simple rotation or (c) double rotation
1.3
-
-
-
-
1.5
1.8
2.1
1.6
1.6
7
VM
molded screwed
1.9
2.1
1.7
1.7
-
8
VT
screwed cased
0.6
0.6
1
0.7
-
9
** GMP OPI **
1.1
1.4
1
0.9
-
10
** BE
Precast prestressed concrete beaten Beat mix (concrete mortar - grout)
2
2.1
1.9
1.6
-
2.1
1
BM **
molded beaten
12
BAF **
13
BAO ** #
14
HB ** #
15
HBi **
16
PP ** #
17
M1
18
M2
Beaten closed steel Beaten open steel H beat H beaten injected IGU or Sheet piling battered Micropieu Type I Micropieu type II
19
PIGU, MIGU
Pile or micropile injected (type III)
11
1.2
1.4
0.8
1.2
0.4
0.9
-
1.2
0.7
0.5
1
1
1.1
1
0.4
1
0.9
2.7
2.9
2.4
2.4
2.4
0.9
0.8
0.4
1.2
1.2
-
-
-
-
-
-
-
-
-
-
2.7
2.9
2.4
2.4
2.4
3.1
3.1
3.1
SAIP 3.4 3.8 Pile or micropile MIRS injected (type IV) ** It should refer to Section A.10 to calculate the perimeter. 20
-
NF P 94-262
# For Type pious BAO, HB and PP, implemented by vibrodriving, not by hype, necessary to make a 30% reduction on the values of qs. For piles ## of great length, it is appropriate to apply the clause (6) of this section. (a) For micropiles BE, HBi, MIGU, PIGU, SAIP and MIRS, the proposed values correspond to a strict and careful execution of the corresponding injection. Compliance testing (Section 8.9) will precisely define the unit axial friction values to consider. It is then necessary to apply the values £ 1 'and £ 2' of table C.2.3.1. It draws attention that this recommendation is particularly important in clays and marl that performance in these fields are very sensitive to any deficiency in the implementation. (b) For micro piles and piles of class 17 and 18, should be considered the unit axial friction values of the nearest technical piles or micro piles in terms of technology. (c) The values given for deep foundation Category 6 are given for piles realized with a continuous record of drilling parameters and concrete (Table 6.4.1.1 Note (1)). Otherwise, we run the risk of discontinuities and damage the pile during its production. (d) The values stated for the deep foundations of category 7 implemented with technical concreting directly to the concrete pump are given for piles realized with a continuous record of achievement pile parameters. Otherwise, we run the risk of discontinuities and damage the pile during its production. (e) It should refer to Section A.10 for the selection of areas and piles of areas to be considered in the calculations. (f) Other values may be used provided they meet the conditions of clause 9 of the section 1.
Table F.5.2.2 - Numerical values of the parameters a, b and c of the curves fsoi - Method pressiometric
Soil type
Clay soils CaCO3% <30% intermediate Limon Sand Grave intermediate
Choice of the curve at
0,003
b
0.04
c
3.5
Q1
Q2 0.01 0.06 1.2
Chalk Q3 0,007 0.07 1.3
corrupted Marne and or Calcairefragmented Marly rock Q4
Q5
0,008
0.01
0.08
0.08
3
3
NF P 94-262
Legend: Y: Figure F.5.2.1 - fsol Curves for pressuremeter method
NF P 94-262
Table F.5.2.3 - Maximum values of unitary axial friction limit qs Values in kPa Clay NO Abbreviati implementation of soils Marne and corrupted or CaCO3% T on technical <30% Chalk intermediate Calcairefragmented Limon Sand Grave Marly rock intermediate FS ## single drilled (piles and 1 90 90 200 170 200 strips) 2 FB ## Drilled mud (piles and 90 90 200 170 200 3 4 5 6
FTP
Cased drilled (lost ferrule)
50
50
50
90
-
Cased drilled (recovered ring) FSR, FBR, simply drilled or mud with PU ## grooving or wells Continuous flight auger FTC FTCD drilled simple rotation or
90
90
170
170
-
-
-
-
200
200
200
FTR
90
__
90
170
7
VM
molded screwed
130
200
170
170
-
8
VT
screwed cased
50
90
90
90
-
9
** GMP OPI **
130
130
90
90
-
10
** BE
Precast prestressed concrete beaten or Beat mix (concrete mortar - grout)
170
260
200
200
-
11
BM **
molded beaten
90
130
260
200
-
12
BAF **
Beaten closed steel
90
90
50
90
-
13 14 15 16 17
BAO ** # HB ** # HBi ** PP ** # M1
Beaten open steel H beat H beaten injected IGU or Sheet piling beaten Micropieu Type I
90 90 200 90
50 130 380 50
50 50 320 50
90 90 320 90
90 90 320 90
18
M2 PIGU, MIGU SAIP, MIRS
Micropieu type II Pile or micropile injected (type III) Pile or micropile injected (type IV)
200
380
320
320
320
200
440
440
440
500
19 20
NF P 94-262
Appendix G (Normative) Lift limit and tensile yield strength from the method penetrometer
G. (1)
1. Preamble This annex gives the rules to determine the limit bearing and the tensile yield strength of a deep foundation isolated as axial stress from tests up static penetrometer
mechanical or electrical point (Notes 1 and 2).
NOTE 1 - The proposed method is based on the value of the penetration resistance qc that it is measured by means of a penetrometer to mechanical or electrical point. The definition of the various parameters of the method takes into account differences between the penetrometer advanced mechanical and electrical tip penetrometer. NOTE 2 - This Schedule does not apply to deep foundations sized from data measured using a dynamic penetrometer. (2)
The exposed method assumes that the penetration resist ance qc was measured by means of a skirt without cone. In the opposite case, the value of resista nce to
mechanical penetration will be corrected by dividing it by a correction coefficient whose value is of the order of 1.3 (Note 1). The value of this correction coefficient may possibly be higher and therefore it should ensure its value before making the correction (Note 1).
NOTE 1 - Ignoring this correction can lead to under-dimensioning of the foundation and cause more or less severe damage on the scope structure. (3)
This method is fully applicable for soils (Note 1) and field classes specified in Annex B (Note 1).
NOTE 1 - specific aspects of behavior of rocks outside the scope of this document. It should be appreciated in what cases a foundation called "the rock" can be justified by the proposed methods and in what circumstances the use of specific methods of rock mechanics is required. (4)
This comprehensive method Sections 9, 10 and 14 of this document dealing with justifications to respectively the ultimate limit states and serviceability limit states for
deep foundation under axial loading in compression and tension.
G. (1)
2 model Coefficient Values yR model coeffici ents; yR d1 and d2 are shown in the table G.2.1. The value of yRd1 model coefficient varies depending on wheth er the pile is under
compression or tension (Notes 1 to 3).
NOTE 1 - YR model coefficient; d2 is not about procedure "model pile." NOTE 2 - The model coefficient YR ; D1 for piles anchored mainly in chalk is equal to 1.4 because of the difficulty in properly understanding the mechanical behavior of geological chalk that can present certain specific rheological on the plane (thixotropy). NOTE 3 - The piles of Class 10, 17, 18, 19 and 20 require the use of injection techniques whose mastery is complex. The performance in terms of compressive strength and tensile strength of these
NF P 94-262
piles categories are very variable. The model coefficient to quantify the dispersion calculation model related to these techniques has been increased and brought to a value equal to 2.0. Table G.2.1 - Value of model coefficients for the penetrometer method Procedure "model pile" (use \ coefficients or Annex D of the standard EN 1990) Procedure "terrain model" Procedure "terrain model"
Y
YR; d1
R; d1
Compression
Traction
1.18
1.45
Y
Y
R; d2
R; d2
Compression
Traction
Piles unanchored in Class 1 to 7 out of chalk piles category 10 and 15
1. 1
Stakes anchored in the class of chalk 1 to 7 out of piles category 10, 15, 17, 18, 19 and 20 1.45
1.75
2. 0
2. 0
Pile category 10, 15, 17, 18, 19 and 20
G. (1)
3Résistance limit This article defines the procedures to determine the compressive limit lift Rc and Rt tensile yield strength of a single deep foundation made in line with a penetrometer
survey. (2)
The lift limit compression Rc of a single deep foundation must be determined from the following general expression (G.3.1) (Notes 1 and 2): Rc = Rs Rb +
(G.3.1)
Rc is the value of the lift of the deep foundation; Rb is the value of the peak strength of the deep foundation; Rs is the value of axial friction resistance of the deep foundation (Note 2);
NOTE 1 - The methodologies for calculating Rb and Rs are specified in the articles and G.4 G.5 below. NOTE 2 - The friction engagement height does not necessarily correspond to the full height of the element in the soil. This is the case particularly for piles having a double lining or to the piles subjected to negative friction. (3)
Rt tensile yield strength of a single pile is to be determined from the following
general expression (G.3.2) (Note 1): (G.3.2)
= R S
R t
Rt is the resistance value of the field strength limit
NF P 94-262
Rs is the value of axial friction resistance of the deep foundation (Note 1);
NOTE 1 - The calculation methodology of Rs is specified in section G.5. G.
G. (1)
4 advanced Resistance 4.1 General Principle The limit force had mobilized after tip of a stake must be calculated from the following general expression:
R = ABQB
(G.4.1)
Rb is the value of resistance to compression of the ground under the pile base; Ab is the area of the base of the foundation (Section A.10); qb is the value of the burst pressure of the ground under the pile base (G.4.2).
G.
4.2 break ground pressure
(1) Except in special cases (Note 1), the value of the burst pressure of the ground under the base of a deep foundation must be calculated from the following general expression:
qb = kcqce
(G.4.2.1)
qb is the value of the burst pressure of the ground under the pile base; kc is the Penetrometer lift factor; qce the resistance equivalent penetration.
NOTE 1 - Where appropriate (clause 9.2 (1) Note 1), it should consider the total vertical qo existing stress in the ground at the base of the pile at work (Note 2) applying in this case the following general expression: qb = qo + kcqce
(G422)
NOTE 2 - The total vertical stress qo is to consider the situation in which the foundation is justified disregarding it. (2)
The value of the penetrometer kc bearing factor must be determined from the table G.4.2.1 depending on the nature of the formation in which the base of the deep
foundation is, the work of the pile-up mode (Note 1 ) and installation.
NOTE 1 - The experimental results currently available do not allow to identify a possible influence of the shape of the cross section of the pile. (3)
The penetrometer profile corrected qcc (z) is obtained:
—
by calculating the average value of the qcm penetration resistance smoothed over the height (b + 3a) (G.1 Clause (2));
—
by clipping if the location qc diagram (z) to the value 1.3 mcq.
(4)
In the case of a homogeneous formation carrier (Notes 1 and 2), the value of the resistance equivalent qce penetration must be determined from the following general
expression:
NF P 94-262
1
q the T-- = j Vac (ZZ) dz 3a + b J
D + 3a
(G.4.2.3)
db
qce is the resistance equivalent penetration; b is the value of the thickness of the slice field considered above the base of the pile; qcc (z) is the Penetrometer corrected profile; B is the width of the deep foundation; h is the height of the deep foundation contained in the carrier formation;
B_ a = max
(G.4.2.4)
2
b = min {a; h}
(G.4.2.5)
NOTE 1 - an indication, a formation can be considered uniform if it is composed of a unique nature of soil and if the resistance to the maximum penetration measured in this formation does not exceed twice the minimum resistance to penetration. NOTE 2 - If not, it should make a careful choice of the representative value of the resistance equivalent penetration, noting that if there is a strong bedrock near the tip of the piles, it is always possible deepen the stakes until this one. (5) The bearing capacity factor depends on the Def effective installation height defined by the following rules: hD denotes a length of 10B. D D
(6)
---- j Va (z Z) dz q
(G.4.2.6)
this D-hn
The actual installation is equal to Def / B where B is the smallest dimension of the foundation:
when underrun Def / B is greater than 5.0: kc (Def / B) = kcmax;
—
—
e f
when underrun Def / B is less than 5.0:
—
kc (Def/ B) = 0.3 + (k
cmax-0.3)
(Def/ B) / 5to lesargiles / stringers;
—
kc (Def/ B) = 0.2 + (k
cmax-0.2) (Def/ B)
/ 5to intermediate lessols;
—
kc (Def/ B) = 0.1 + (k
cmax-0.1) (Def/ B)
/ 5to lessables and serious;
—
kc (Def/ B) = 0.15 + (k
cmax-0.15)
(Def / B) / 5 for chalk, marl and altered rocks or
fragmented.
NOTE 1 - At least the effective embedding in the support layer is taken equal to 3 diameters or 1.50 m for pile diameters larger than 0.5 m. If the company special foundations can ensure the proper execution of the installation of advanced stakes in the carrier layer or by taking samples or by bit employment, or by the use of sampler then this anchor can be reduced to a minimum value of 0.5 m.
NF P 94-262
Table G.4.2.1 - bearing factor value penetrometer kcmax for installation actual Def / B> 5 Clay Ground Marne Ground Sand Chalk LimestoneCaCO3% <30% intermediate Serious Stake Marly class (c) Limon 0.4 (b) 0.3 (b) 0.2 (b) 0.3 (b) 0.3 (b) 1 2 3 4 5# 6# 7# 8
Roche impaired or fragmented (a) 0.3 (b)
0.45
0.3
0.25
0.3
0.3
0.3
0.5
0.5
0.5
0.4
0.35
0.35
0.45
0.4
0.4
0.4
0.4
0.4
0.35
0.3
0.25
0.15
0.15
0.15
0.4
0.4
0.4
0.35
0.2
0.2
0.35
0.25
0.15
0.15
0.15
0.15
0.45 (b)
0.3 (b)
0.2 (b)
0.3 (b)
0.3 (b)
0.25 (b)
(#) To the type of pious BAO, HB and PP, implemented by instead of hype, it should be vibrodriving make a 50% reduction on the KC factor. (A) The kc value for the altered and fragmented rock must be taken equal to that of the unconsolidated formation of the table at which the material concerned is most closely related. In the case of sound rock, it is (G. 1. (3) Note l) to assess whether a justification based on the methods of this Annex G and pessimistic evidence is sufficient, or whether to use the specific methods of rock mechanics. (B) For micropiles, advanced resistance is not normally taken into account. (C) It is appropriate to refer to Article A.10 for the selection of areas and piles of areas to be considered in the calculations. (D) Other kcmax values may be used provided they meet the conditions of clause 9 of the section 1.
G.
5 axial friction resistance
G.
5.1 General principle
(1) The mobilisable limit force by axial friction on the respective height of the shank of the deep foundation must be calcul ated from the following general expression:
ps = fq (z ') Dz
Rs
(F51)
Rs is the value of the axial friction resistance of a deep foundation; PS is the perimeter of the pile shaft (Section A.10); D is the length of the foundation contained in the ground (Note 1); qs (z) is the value of the unit axial friction limit in the z-dimension (Article G.5.2).
NOTE 1 - The height Ls when the axial friction is mobilized does not necessarily correspond to the full height of the element in the soil. This is particularly the case of piles with a double lining or to the piles
NF P 94-262
subjected to negative friction. In the latter case, it should if necessary to define two values of Rs, one for compression and one for traction.
G. (1)
5.2 Friction unit axial limit qs The value of the unit axial friction qs limit at depth z must be determined depending on the nature of the terrain, the implementation mode of the pile and the resistance
value to the smoothed penetration measured at the same depth, from tables G.5.2.1 and G.5.2.2 and G.5.2.1 figure. (2)
The value of the unit axial boundary friction at depth z is determined from the following relationship:
hs (z) = aP, got thirsty ground hc (z )] (G.5.2.1)
qc (z) is the resistance to penetration smoothed at depth z; has pieus0 | is a dimensionless parameter which depends both on the type of pile and soil type defined in the table G.5.2.2; fsol is a function that depends only on the type of soil and qc values. (3)
The fsol functions are defined for different types of soil by the following equations (Figure G.5.2.1)
fsoi (hc) = (AQC + ¿X1 - e Cq ')
(G522)
The parameter values are defined in Table G.5.2.2 for resistance values penetration qc in MPa. (4)
At low peak strengths (less than 1 MPa for clays and silts and less than 1.5 MPa for sands), it must be ensured that the friction is considered unitary axial perennial. It is
therefore necessary to conduct a special study to justify this hypothesis (eg, demonstrating the absence of negative friction induced by overload or changes in the water table or by checking that the charges raids were properly calculated) . (5)
Independently of FIG G.5.2.1 and G.5.2.2 general relationship of equation defined on the basis of experimental measurements, i t must be ensured that the unit axial
friction values determined are not greater than those defined in table G.5.2.3. (6)
For piles of great length listed in Table G.5.2.1 (sign ##), with corresponding soils, apply a 50% reduction on the friction value derived from the application of different
tables and figures on the sections stake located 25 m or more above the tip.
NF P 94-262
Table G.5.2.1 - Choice of apieu.soi values - Method penetrometer
N O Abbreviation implementatio n of technical T FS ##
7
VM
single drilled (piles and strips) Drilled mud (piles and strips) Cased drilled (lost ferrule) Cased drilled (recovered ring) simply drilled or mud with grooving or wells Continuous flight auger drilled simple rotation or molded screwed
8
VT
screwed cased
9
GMP ** ** OPI
10
** BE
1 2
FB ##
3
FTP
4
FTR
5
FSR, FBR, PU ##
6
FTC FTCD
Precast prestressed concrete Beat mix (concrete mortar - grout)
Clay% CaCO3 <30% Limon
soils intermediate
Sand Serio us
Marne and corrupted or Chal Calcaire- fragmented Marly k rock
0.55
0.65
0.70
0.80
1.40
1.50
0.65
0.80
1.00
0.80
1.40
1.50
0.35
0.40
0.40
0.25
0.85
0.65
0.80
1.00
0.75
0.13
-
-
-
-
-
1.50
1.50
1.60
-
0.70
0.85
0.75 0.95
0.90 1.15
1.25 1.45
0.95 0.75
0.30
0.35
0.40
0.45
0.65
0.55
0.65
1.00
0.45
0.85
-
1.00
1.20
1.45
0.85
1.50
-
0.95
0.95
BM **
molded beaten
0.60
12
BAF **
0.40
13
BAO ** #
Beaten closed steel Beaten open steel
14
HB ** #
15
HBi **
16
PP ** #
17
M1
11
18
M2
19 PIGU, MIGU 20
SAIP, MIRS
H beat H beaten injected IGU or Sheet piling battered Micropieu Type I Micropieu type II Pile or micropile injected (type Pile or micropile injected (type
-
0.70
1.00
0.50
0.85
0.70
0.50
0.65
0.70
1.60
2.00
0.45
0.55
0.55
-
-
-
-
-
1.35 1.70
0.60 0.55 1.35
0.20 0.25
0.85
-
-
0.95
0.95
0.95
0.85
2.25
2.25
1.25
1.15
-
-
-
-
-
-
-
1.60
2.00
1.10
2.25
2.25
2.05
2.65
1.40
2.90
2.90
0.20 1.10 0.20
NF P 94-262
** It should refer to Section A.10 to calculate the perimeter. # For Type pious BAO, HB and PP, implemented by vibrodriving, not by hype, necessary to make a 30% reduction on the values of qs. For piles ## of great length, it is appropriate to apply the clause (6) of this section. (a) For micropiles BE, HBi, MIGU, PIGU, SAIP and MIRS, the proposed values correspond to a strict and careful execution of the corresponding injection. Compliance testing (Section 8.9) will precisely define the unit axial friction values to consider. It is then necessary to apply the values £ 1 'and £ 2' of table C.2.3.1. It draws attention that this recommendation is particularly important in clays and marl that performance in these fields are very sensitive to any deficiency in the implementation. (b) For piles of category 17 and 18, should be considered the unit axial friction values of the nearest technical piles or micro piles in terms of technology. (c) The values quoted for deep foundations Category 6 are given for piles made with a continuous recording of drilling parameters and concreting (Table 6.4.1.1 Note (1)). Otherwise, we run the risk of discontinuities and damage the pile during its production. (d) The values stated for the deep foundations of category 7 implemented with technical concreting directly to the concrete pump are given for piles realized with a continuous record of achievement pile parameters. Otherwise, we run the risk of discontinuities and damage the pile during its production. (e) It should refer to Section A.10 for the selection of areas and piles of areas to be considered in the calculations. (f) Other values may be used provided they meet the conditions of clause 9 of the section 1.
Table G.5.2.2 - Numerical values of the parameters a, b and c of the curves fso - Method penetrometer Soil type
clays
soils intermediate
Choice of the curve at
Q1
Q2
Q3
Q2
Q2
Q2
0.1
0.1
0.1
0.1
0.1
0.1
0.0015
0.0015
0.0015
0.25
0.25
0.25
b c
0.0018 0.4
0.0015 0.25
sands
Chalk
0.0012 0.15
corrupted Marne and or Calcairefragmented Marly
NF P 94-262
Figure G.5.2.1 - fsol curves for the penetrometer method
NF P 94-262
Table G.5.2.3 - Maximum values of unitary axial friction limit qs Values in kPa Clay% Marne and N Abbreviati implementation Sand CaCO3 <30% soils Calcaire- corrupted or O on of technical fragmented Seriou Chalk Marly T Limon intermediate s rock 1 2 3 4 5
6 7
single drilled (piles and strips) Drilled mud FB ## (piles and strips) Cased drilled FTP (lost ferrule) Cased drilled FTR (recovered simply drilled FSR, FBR, or mud with PU ## grooving or wells Continuous flight auger FTC FTCD drilled simple rotation or molded VM screwed FS ##
8
VT
screwed cased
9
** GMP OPI **
10
** BE
Precast prestressed concrete Beat mix (concrete mortar - grout)
11 12 13 14 15 16 17 18 19 20
BM **
molded beaten
Beaten closed steel BAO ** # Beaten open steel HB ** # H beat H beaten HBi ** injected IGU or Sheet piling PP ** # battered Micropieu M1 T eI Micropieu type M2 II _ Pile or PIGU, micropile 200 MIGU injected (type Pile or SAIP, micropile 200 MIRS injected (type BAF **
90
90
90
200
170
200
90
90
90
200
170
200
50
50
50
90
-
90
90
90
170
170
-
90
90
-
-
-
-
90
90
170
200
200
200
130
130
200
170
170
-
50
50
90
90
90
-
130
130
130
90
90
-
170
170
260
200
200
-
90
90
130
260
200
90
90
90
50
90
90
90
50
50
90
90
90
90
130
50
90
90
200
200
380
90
90
50
_
_
__
__
__
200
380
320
320
320
200
440
440
440
500
Appendix H (Informative)
50
320 50
320
-
320
90
90
NF P 94-262
negative friction assessment on deep foundation
H. (1)
1 Scope This Annex applies to the calculation of the negative friction on a deep foundation through a compressible soil subject to underweight action of an embankment (Note 1).
NOTE 1 - It does not normally apply to other cases, for example when the negative friction phenomenon is induced by: —
the folding of a sheet;
—
natural land (subsidence) or reported (land reclamation) that tamp;
—
loose soils tamp saturation or densification under seismic effects.
(2)
The rules apply only indicated a foundation system consists of identical and vertical elements.
(3)
They should be used with the rules defined in Section 8 (Note 1).
NOTE 1 - It is noted that the negative friction is zero below the neutral point for a single deep foundation and the limit field strength and the creep load is estimated by assuming that friction is zero axial auabove this point.
H.
2 maximum negative friction on a secluded deep foundation
H.
General 2.1Expression
(1)
The negative friction on a deep foundation must be calculated from the following general expression (Note 1): j
h
Gsn = P J K (z ) tan 5 (z) 'AV (z) dz
(H.2.1.1)
pm -
P is the perimeter of the pile;
rv (z) is the effective vertical stress in the long term at depth z, in contact with the deep foundation, taking into account the disturbance caused by the attachment of the gr ound around thereof;
K (z) is the ratio of the effective horizontal stress and the effective vertical stress;
tan? (z) is a friction coefficient the value of which depends on the nature of the ground-contacting wall;
5 is the friction angle of the contact subgrade element;
NF P 94-262
h is the height of the foundation element on which acts the negative friction.
NOTE 1 - The method used to evaluate the forces due to negative friction does not explicitly introduced legislation to mobilize these efforts based on the relative displacement subgrade element. This is a method proposed by breaking O.Combarieu and based on the assumption of an adequate relative movement to mobilize the maximum unit negative friction over the height where it is supposed to act.
H.
2.2 Evaluation term Ktanô
(1)
In practice, one should consider the product KtanS as a term which the two factors are inseparable.
(2)
Its value is given in table H.2.2.1, depending on the nature of the relevant training and the type of pile (Notes 1 to 3).
(3)
For the categories of deep foundations not described in the table H.2.2.1, it should refer to the show the closest in terms of technology (Annex A).
H.
2.3 Assessment of the effective vertical stress O'V (z)
Table H.2.2.1 - Terme KtanS
Pious Pious
soils Cased bored piles
peats
organic soils
Pious drilled
Pious beaten
0.10
0.15
0.20
0.10
0.15
0.20
0.15
0.20
0.30
very loose
0.35
0.35
0.35
cowardly
0.45
0.45
0.45
other
1.00
1.00
1.00
soft Clays, silts
jacketed bitumen <0.05 <0.05
<0.05 farms hard
<0.05
<0.05 Sands serious
<0.05
NOTE 1 - The choice of the type of soil will be guided by the conventional categories given in Annex B. NOTE 2 - When the soil type can not be identified precisely, the Ktanô term is determined by interpolation from the various values presented in table H.2.2.1.
H. (1)
NOTE 3 - Of course, the design value of Ktanô may be deducted from measurements taken when, for various reasons, especially when the project economy justifies, it is necessary to proceed on the same site at trials true greatness. 2.3.1Expression of a ' v(Z, r) It is assumed that the 'AV value (z, r) is given by the following general expression (Figure H.2.3.1):
at; (Z, r) -av (z) = (crj (z) ov (z)) | 1 -e
(H.2.3.1)
NF P 94-262
av (z, r) is t he effective vertical stress in the z-dimension and the distance r from the longitudinal axis of the foundation element after occurrence of negative friction;
a \ (z) is the actual vertical load "undisturbed" corresponding to that which would prevail in the soil in the absence of the foundation element;
X is a coefficient characterizing the amplitude of the hooking of the soil around the foundation element;
R is the radius of a circular pole or when the section is not circular, the radius of the circular element of the same perimeter; r is the distance to the longitudinal axis of the foundation element.
Figure H.2.3.1 - Evolution CV s r (2)
The term c1 (z) must be calculated in the axis of the foundation element taking into account the
different loads (generally constituted by embankments) disposed in the vicinity of the element (Notes 1 and 2). NOTE 1 - The additional constraint of overload is to be assessed by the usual methods of distribution of stresses in an elastic soil.
NOTE 2 - In the case where the negative friction is generated by an indefinite uniform overload po, c1 (z) is expressed p0 + yz (yétant the volume weight of soil, possibly halfgauge).
(3) H.
X is gi ve n ( No te 1) by th e fo ll ow ing eq ua ti on s de pen di ng on th e va lu e of K ta n S (F ig ur e
2.3.2):
1------------ --- if : K
X = --------------------
0, X =
tan S <
0,150
(H.2.3.2)
5 + 25 tan S
0,385 - K tan S if: 0,150
NOTE 1 - The value of X is the result of a correlation with the term Ktan 8 established from experimental results.
(H.2.3.3)
(H.2.3.4)
NF P 94-262
0.5
0.4
0.6 blR b = 2.5 / R
0.2
= 3.0 / R = 3.4 Bir blR = 4.0 b = 5.0 / R = oo January 1
0 0 .2
0,40,5
0.8
1
1.2
1.4
1.6 X
Figure H.2.3.2 - Relationship At = f (Ktanô) H.2.3.2 Expression Jv (z)in a layer (1) The value of Jv (z) results from the balance of the vertical forces applied to the soil and the foundation element at depth z, calculated in accordance with the variation law adopted jv (z, r) (Notes 1-3).
NOTE 1 - successive soil layers were cut into thin slices enough so that we may consider that {DJ1 (z ) / dz ) Has a constant value along the axis of the foundation element in each of the slices. NOTE 2 - The calculation 7v (z) along the foundation element is carried out step by step the borders between slices from the top downwards, starting from the head value of the first layer (usually constituted by an embankment), this value being known and generally zero. NOTE 3 - Knowing the value 7V (zj ) of
(_Az
j \
1 _ e Lo
if: / u (X) ^ 0
(H.2.3.5)
J (zj + i) _J (zj) = AzjddJJ if: ^ (X) = 0 (H.2.3.6)
AZJ is the thickness of the slice j, is: AZJ = zj + zj 1 _
u.(X) is a characteristic parameter of the equation given by: /u.(X)
At A2 1 +
R L0 is a characteristic parameter of the equation, given by L0 [¿(X) K tan?
NF P 94-262
R is the radius of a circular post, or when the section is not circular, the radius of the element P
circular for a given perimeter: R = -
2n
H.
2.4 negative friction action Height
(1) The negative friction action height is generally taken as the l ower of the two values h1 and h2, as defined below:
h1 is the depth where the strain calculation cr'v (z) becomes equal to the constraint
—
existing in the field prior to execution of the foundation and establishment of the overload (Note 1); —
h2 is the level where the settlement still to be acquired by the ground after completing the foundation, calculated without regard to the latter, becomes equal to B / 100 (Note 2).
NOTE 1 - The definition of hi translated as, due to the attachment of the material around the foundation element, there is a level along one where the effect of overload causing the appearance of negative friction disappears. In the case of a group of piles, h is strictly speaking the depth where the average calculation constraint between the piles is equal to the pre-existing stress in the field. NOTE 2 - The definition recognizes h2 own pile settlement and free soil compaction, the value may be low (or very compressible soil compaction upcoming small scale because, for example, a preloading soil ). This "free" settlement is calculated according to the usual mistakes, usually from the consolidation theory.
H.
2.5 Expression of the total negative friction
(1) The total negative friction acting on a deep single pile foundation is the sum of the height of action thereof, the elementary terms calculated in each interval where KtanS is constant, by the following expressions (Note 1): J
)dz if u ( X ) GNJ = P (K Tano ) ) C. (z PR
= 0
{[Ci (h) -c. (H)] - [hereinafter (- i) -c. (H, -i)]} if u (P * 0
(H.2.5.2) (H.2.5.1)
G= U
(X) h, -.
G, is the negative friction in layer j; hj and hj-1 are the dimensions of the layer
j.
NOTE 1 - These expressions are valid without restriction on the constancy of (DC. (Z) / dz ). each term above which can be calculated based on each set of slices where K tanO is constant. the second expression is also a maximum level of negative friction on a single pile, regardless of the value of X. (2)
Next the ground and pile technique used, the negative friction value must be confined to the unit axial friction value in the tables F.5.2.3 and G.5.2.3.
H.3 negative friction on a deep foundation within a group (1) The negative friction on a foundation element in a group can be calculated using the methods described in this article (Note 1).
NF P 94-262
NOTE 1 - No theoretical method does at present to deal fully and satisfactorily the case of peripheral foundation elements of a group. The estimated values therefore remain empirical, they nevertheless lead to reasonable values for common spaces between foundation elements.
H.3.1 foundation elements on one or more lines (1)
To evaluate the negative friction on any one of a complete foundation element, one must distingui sh the case of a single file that of several files and determine the following
parameters (Note 1):
—
Gsn (œ) which represents the value of the negative friction on th e element, isolated assumed, calculated as shown in section H.2.
—
Gsn (b) which represents the value of th e negative friction on the element, assumed in an unlimited group of identical elements, and in which the calculation is indicated in section H.3.2.
NOTE 1 - In the usual case, to calculate Gsn (œ)and of Gsn (b)It is permissible to calculate the stress
in the
(Z)
axis of the foundation and to assume that it keeps the same value in any the influence thereof. In this way,Gsn (œ)and Gsn (b)are the same for all elements of the foundation. H.3.1.1 Single File (1)
With the notation of FIG H.3.1.1, the amount of negative friction on each element type is given by (Note 1): G, a = 1 G. (b) + | G. (Oe)
(H.3.1.1) Gne 3 = G "(b) + g 3 (œ)
(H.3.1.2)
NOTE 1 - The corner elements are identified by the index, the other elements are the index e.
Figure H.3.1.1 - Single File - Ratings H.3.1.2 Several files (1)
With the notation of FIG H.3.1.2, the amount of negative friction on each element type is given by (Note 1):
Gna = ¡7 G ,, (b) 12 Gn ( ") (H.3.1.3)
NF P 94-262
G "= jgs, W + 7G, (00 ) (H.3.1.4)
66
, I = G ((b) (
G
Figure H.3.1.2 - Several files - Ratings
H
.3.1.5)
NOTE 1 - The corner elements are identified by the index, those of the boundary of the group by the index e and the internal elements of the group by the index i.
H.3.2 Gsn Calculate (b) (1)
Gsn (b) must be calculated on the same principle as that of an isolated element (H.3.2 Clause (3)), the analysis is made on a ground cylindrical volume surrounding the
spoke foundation element b. 35 d is the distance between the foundation elements of the same file; d is the distance between adjacent rows of foundation elements.
b
dd b=
35
not
(H.3.2.2)
The radius b of the cylindrical volume of soil around the foundation element is defined, in the notation of FIG H.3.2.1, as follows:
- single file:
(H.3.2.1)
- several rows:
NF P 94-262
(3)
Values Gsn (b) and
the isolated element data section H.2 by replacing in the expressions for the isolated element, p ( A) p (A, B), determined as indicated below (Notes 1 and 2):
2
(H.3.2.4)
A2
M (A, B )
if A ^ 0
(H.3.2.3)
^ Ab -a-
A- 1+ / U (A , b )
1+
R
e
= --------------------2 --------if : A = 0
CR J -1
NOTE 1 - The graph of FIG H.3.2.2 gives ^ values (A, b) a function of b / R and A. NOTE 2 - It is noted that for a pile located in an unlimited band and at a uniform qo overload the surface, the value of Gsn (b) is bounded above by nb2q0.
0 .0.5 6
0.4 0 .2 FIG H.3.2.2 - Pile Group Abacus for calculating Gsn (b) 00,20,40,50,811,21,41,6 AT
blR =2.5 b / R = 3.0 b / R = 3.4 B ir = 4.0 blR = 5.0 b /
NF P 94-262
H.4 Special cases abutments (1)
When the soil situated above the level of the bonding pad of the elements of a foundation may pack relative thereto, the account of negative frictional engagement must be
performed as follows (Figure H. 4.1): —
efforts that develop on planes passing through the edge of the sole have a value equal to the vertical component of the thrust force of the supposed land inclined at an angle equal to the angle of internal friction of the soil;
—
cr1 the constraint (z) is computed in the axis of the foundation without considering the weight of land applied directly to the sole.
NOTE 1 - These arrangements are illustrated in Figure 2 H.4.1 case of bridge abutments.
Figure H.4.1 - Examples of works abutments
NF P 94-262
Appendix I (Informative) Modeling the transverse behavior of a foundation profondeà from tests pressuremeter and penetrometer
1.1 single pile 1.1.1
Application domain
(1) Annex I.1 defines for an element isolated deep foundation (Notes 1 and 2), construction of foundation soil-element interaction laws describing the transverse behavior, from the results of pressuremeter tests Ménard. It addresses the case of pile groups in Annex I.2. In Annex I.3 are presented the principles for determining the laws of soil-interaction element for seismic l oading. Annex I.4 contains the principles for determining the soil-element interaction laws from penetrometer data.
NOTE 1 - I.1.3 I.1.6 annexes to define the laws of probable characteristics applicable in most cases. Annex I.1.7 defines the laws of maximum characteristics, particularly suited to the study of elements subject to transverse forces from the ground. More elaborate models representing more correctly the real phenomena are also available, for cases where the project's complexity justifies to use such models. NOTE 2 - It may be necessary to make changes to the isolated element behavior model for dealing with cases of deep foundations composed of several elements. Indications are given in this regard to paragraph I.2 below.
1.1.2
General principle
(1) It is assumed that the soil exerts in each section of the reaction member perpendicular to the axis thereof, which is a function of the transverse relative movement of the section, and that this r eaction consists of: —
frontal pressure, which is modeled by a uniform pressure on the greater width of the element perpendicular to the direction of movement, denoted B (Note 1);
—
transverse friction forces exerted on the parts of the perimeter parallel to the direction of travel; however, a part of this friction being already incorporated into the front pressure mentioned above is subtracted the value B to each part for the evaluation of friction (Note 2).
NOTE 1 - For example, in the case of a circular pile, this pressure is exerted uniformly over a width equal to the diameter of the pile. NOTE 2 - lateral friction are efforts that oppose the movement of the element. In the case of rectangular sections tending to move in the direction of their larger size, these efforts appear on the faces parallel to the direction of travel. In the case of composite sections, it is accepted to consider that they grow on the surfaces parallel to the direction of travel, the smallest perimeter circumscribed to the real section. The parts of this scope to be considered are shown schematically in Figure I.1.2.
NF P 94-262
Figure I.1.2 - Length calculation of lateral friction
I.1.3
Laws vis-à-vis interaction short period of application of stress
(1) Except for special cases (I.1.3 Clause (3)), the mobilization law of the end reaction r = pB depending on the displacement 8 of the pile must be defined by:
—
a straight line through the origin and Kf slope;
—
a bearing ri. (Figure I.1.3.1) r
S Caption: r1: Front reaction; 8: relative movement of the foundation member.
Figure I.1.3.1 - Front reaction Act - General case (2)
The evaluation of K f and r from Ménard pressuremeter test results shall follow the instructions below:
- Kf modulus is calculated from one of the two following formulas:
12 E
K f = ------------------------- M ----------- when B
(I.1.3.2)
Kf is the li near module mobilization of the front pressure for a deep foundation member (Note 1); EM IS THE PRESSIOMETRIC MENARD MODULE; 12 E
when B> B0
M
f =
K
4 B0 3 B
2.65 B B0
a t
+a
(I.1.3.1)
NF P 94-262
B is the width of the member perpendicularly to the direction of travel; B0 is a r eference width set equal to 0.60 m; a is a coefficient characterizing the ground in the pressiometric method (I.1.3.1 and I.1.3.2 Tables). - RF bearing is taken equal to:
ri = Bpf * (I.1.3.3) B is the width of the member perpendicularly to the direction of travel; p * is the net flow pressure ( Note 2)
NOTE 1 - Kf is bonded to the surface module called kf reaction coefficient Kf by the expression B = kf NOTE 2 - The results of calculations have to highlight the maximum value calculated reaction (usually the head) and compare it to pf * if the resulting cross-reactions of the ground on the deep foundation is null before application of stress. In the case where a state of overburden stress is considered (resultant of the side reactions of the non-zero ground), the maximum value calculated pressure to be compared with m.p.. (3)
For some calculations, for example vis-à-vis very brief accidental stresses (shock), or for cohesive soils, rare solicitations short, it is accepted that justifications are
conducted from an interaction diagram such as that shown in FIG II3.2. (4)
The value of r2 bearing is defined by the following relationship: r = Bp,
__
5¡S
B is the width of the member perpendicularly to the direction of travel; pl * is the net pressuremeter limit pressure.
Figure I.1.3.2 - Front reaction Act - Special case
(I.1.3.4)
NF P 94-262
Table I.1.3.1 - rheological coefficients a - Method pressiometric Land
Peat at
Clay
Silt
E
M / pl
I
-
> 16
II
1
9-16
III
-
7-9
E
at
M / pl
Sand at
Serious
E
at
E
M / pl
M / pl
at
> 14
2/3
> 12
1/ 2
> 10
1/3
2/3
8-14
1/ 2
7-12
1/3
6-10
1/4
1/ 2
5-8
1/ 2
5-7
1/3
1
-
-
I was: overconsolidated or very tight field II : Normally consolidated ground or normally tight, III : Sub-field overconsolidated altered and redesigned or loose.
Table I.1.3.2 - Coefficients has rocky terrain - Method pressiometric at Rock
(5)
Very few fractured
2/3
Normal
1/ 2
highly fractured
1/3
very thirsty
2/3
Mobiliza tion law of the tangential reaction, that is to say the fricti on developed on the side surfaces of the elongate founda tion elements such as webs, must be defined
by: —
a line segment passing through the origin and of slope Ks = Kf;
—
rs a bearing (Figure I.1.3.3).
NOTE 1 - It is permissible to use other relationships to estimate Ks especially considering the relationships that exist between the reaction coefficients kf and ks.
Legend: r: tangential reaction; 8: displacement of the foundation element.
Figure I.1.3.3 - tangential reaction Act - General case (6)
The rs assessment from Ménard pressuremeter test results must be performed from the following relationship:
rs
=
2
Lsqs
Ls is the l ength over which is calculated on the lateral friction (I.1.2 I.1.2 and Figure);
(I.1.3.5)
NF P 94-262
qs qs is the friction limit whose value is taken equal to that of the axial friction.
(7)
The law of mobilization of the overall reaction to consider is the sum of the reaction front and the tangential reaction defined above in I.1.3 clauses (1) to I.1.3 (5). As a
result, in the current case, the overall i nteraction law in the form illustrated in FIG II3.4.
Legend: r: resulting reaction; O: movement of the foundation member.
Figure I.1.3.4 - overall reaction Act - General case I.1.4
Laws vis-à-vis interaction of long-term application solicitations
(1) In the usual case (Notes 1 and 2), the l aw of interaction to be considered vis-à-vis long-term application of stress i s defined as follows:
—
the end reaction is in all cases bounded by the value r;
—
the level of the tangential rs reaction is equal to the value defined above to the I.1.3 clause (6) for short period of application of stress;
—
values describing modules mobilization resistant forces as a function of relative displacement are taken equal to half of those defined above in Section I.1.3 for short-term application of stress (Figure I.1.4.1 ).
NOTE 1 - W hen an audit "fork" is considered, a specific analysis of interaction to adopt laws necessary. It will i n particular the fact that, for granular soils, interaction laws may be substantially identical vis-à-vis the load short and long-term application. NOTE 2 - The results of calculations have to highlight the maximum value calculated reaction (usually * head) and compare it with mp.
NF P 94-262
Figure I.1.4.1 - Act vis-à-vis interaction of long-term application of stress - Cases usual I.1.5 If an element implanted sloping head (1)
In the case of foundations operating in peak slope, frontal reaction and possible lateral friction of the soil must be fully taken into account from a dimension such that the
horizontal thickness of soil that can be set abutment is at least equal to 5.B. NOTE 1 - This covers the most common situations where the horizontal force applied to the foundation is exercised towards the embankment, permanently or alternations. In rare cases, where the force is exerted exclusively in the direction opposite to that of the slope, there is no need to apply the reductions prescribed below. (2)
The end reaction and any side friction of the soil above the level defined in I.1.5 (1) shall be determined by the following provisions:
—
the slopes of the basic laws of mobilization of the front pressure and any lateral friction is maintained;
—
is made linearly vary the value of the plastic bearing these laws between the imaginary point of intersec tion of the slope with the axis of the above-mentioned element and the level defined in I.1.5 (1), by assigning a zero value at the point of i ntersection of the axis of the pile and the plane of the slope (Figure I.1.5.1).
Legend: r: frontal or tangential reaction; O: horizontal movement of the element of fondation.Figure I.1.5.1 - Interaction Act in the case of a foundation element implanted bank
head
NF P 94-262 I.1.6
Changes near the soil surface
(1)
In areas close to the surface, the linear module ground and the step value must be minus by the following:
—
the zc towards which applies this lower bound, counted from the surface after the work is taken as 2.B for cohesive soils and 4.B to the rubbing soils;
—
z
—
O axis;
—
r direction;
- ratio: 0.5
Legend: r: frontal or tangential reaction; O: movement of the foundation member.
Figure I.1.6.1 - Act of interaction to be considered close to the soil surface (2)
To simplify the calculations, depending on the type of soil, it is accepted to consider a uniform profile on 2B or 4B tall with applicable law in mind and a limited bearing
0,7r1.
I.1.7 (1)
Case of an element subjected to transverse thrusts
When a foundation element is subjected to transverse forces (horizontal movement) marker, the laws of long-term soil-element interaction shall be defined according to
the provisions of Articles I.1.3 I.1.4 and replacing the value the bearing by r1 r2 value. NOTE 1 - In the case of a deep foundation established in talus head, transverse forces are generally related to the presence of the sl ope and they are carried to the outside of the latter. (2)
These provisions take into account the fact that the transverse forces of the field are likely to cause stress in deep foundation element worse than those that lead the
response laws defined in I.1.3 and I.1.4. (3)
If one application of these transverse forces, the lower bounds defined in I.1.6 and I.1.7 respectively to reflect the presence of a slope and close to the ground surface
should not be considered. (4)
When transverse thrusts and horizontal forces led coexist, can be calculated by combining the two actions, successively considering the profile of the laws of
réactionsincorporant all reductions (reaction laws limited to pf * and / or consideration surface effects), then the profile of the reaction to laws pl * without surface effects.
NF P 94-262 I.1.8 (1)
Multiple burdens long and short term application When the consequences of hysteresi s phenomena can be considered negligible, to calculate the stresses and displacement s in the structure as a combinatio n of specific
actions, the following shall apply: —
we begin by studying the equilibrium state of the structure under the effect of actions (Note 1) of long-only application is:
r o = # v (KB) (I.
1.8 .1)
rv = Ov (Sv) is the law vis-à-vis load-displacement action of long duration;
—
then studies the incremental movement OT = O-ôv0 and incremental efforts rt = r -rv0 with the law (Notes 2 and 3):
r = o [Ot + o-1 (v o)] - rv o
( |
I82)
r = O; K) is the act vis-à-vis force-displacement action of short duration; choosing, when O (Kv0) from the plastic bearing Ot l aw for O-1 value (rv0) the smallest displacement K such that Ot (K) = rv0.
r
v _ ^ v. (Kv) r
i = V (K)
NOTE 1 - The shares are introduced with their "design values" in accordance with section 7.3 NOTE 2 - This procedure amounts to performing a translation, parallel to the axis K on the law r = O (K), the amplitude of this translation being such that the new law passes through the point of coordinates (v0, rv0). These arrangements are ill ustrated in Figure I.1.8.1.
NOTE 3 - When O v and O i are linear laws, it is equivalent to independently study the effects of actions of long and short duration of application and to make the sum.
Legend: r: frontal or tangential reaction; K: movement of the element of fondation.Figure I.1.8.1 - Principle accumulated charges long and short duration of application
NF P 94-262
I.2 Groups of deep foundations I.2.1 (1)
Overview The provisions of Annex I.2 apply to define the laws of transverse behavior of several deep foundation elements when the minimum spacing rules defined in section 8.7.3
(I.2.2.1 and I.2.3 Figures .1) are satisfied and that therefore no interaction between the behavior of various elements.
I.2.2 (1)
Elements placed in the direction of travel When there is a possible interaction between the behaviors of various deep foundation elements placed in the direction of travel (Figure I.2.2.1), the force-displacement
laws defined in section I.1 shall be amended as follows :
—
the slope of mobilization Kf of the front pressure remains unchanged;
—
for all elements located rearward relative to the direction of travel, the value of the plastic bearing rf is reduced in the ratio:
at
(I.2.2.1)
2max (B, The ) B is the width of the member perpendicularly to the direction of travel;
L is the l ength of the element parallel to the direction of travel; a is the distance between two
elements in the direction of travel (Figure I.2.2.1); - modeling of potential lateral friction laws
are not changed.
Figure I.2.2.1 - Conditions for non-interaction between two deep foundation elements placed in the direction of travel I.2.3 (1)
Elements placed perpendicular to the direction of travel When there is a possible interaction between the behaviors of various deep foundation elements placed perpendicular to the direction of travel (Figure I.2.3.1), the force-
displacement laws of the frontal reaction defined in section I.1 shall be modified as follows: - the plastic bearing r1 remains unchanged; - the value of Kf module on each foundation element is reduced, when b is less than 2B, by applying the following minorateur coefficient:
2B
(I.2.3.1)
NF P 94-262
b is the distance between two elements perpendicular to the direction of movement B i s the width of the element perpendicular to the direction of travel; p0 is the ratio Kf own module to a group of n elements and n times that own a single element determined from the following expression:
Kf (n B )
NKF (B
)(
+ 3 (2'65T
at
(I.2.3.2)
na) + 3 (2,65n) '
n is the number of foundation elements involved; a is a coefficient characterizing the ground in the pressiometric method (Tables I.1.3.1 and I.1.3.2)
Figure I.2.3.1 - Conditions for non-interaction between deep foundation elements placed
perpendicularly to the direction of travel NOTE 1 - It should be noted that this formula can not be applied to a small number of elements; beyond group behavior approaches that of a continuous curtain. The plastic bearing ri remains unchanged. (2)
When there is a possible interaction between the behaviors of various deep foundation elements placed perpendicular to the direction of travel (Figure I.2.3.1), the force-
displacement laws of tangential reaction defined in section I.1 shall be modified as follows: —
when b <2.B, no tangential reaction shall be taken into account;
—
when b> 2.B:
—
Ks module remains unchanged;
—
the value of rs plastic bearing on each foundation element is reduced, when b is less than 2L, in the report: b - 2 B2 (L - B)
b is the distance between two elements perpendicular to the direction of travel; B is the width of the member perpendicularly to the direction of travel; L is the length of the element parallel to the direction of travel; - we finally holds for each element the most unfavorable vis-à-vis the effect law between law defined above and the law of the single element.
(I.2.3.3)
NF P 94-262
I.3 Laws vis-à-vis interaction of seismic loading (1) In the usual case (Note 1), the interaction law to take into account vis-à-vis the seismic loading is defined as follows:
—
the reaction front is bounded by the r2 value taking into account possibly the decrease in the mechanical characteristics of the soil under the effect of the cyclic loading of the earthquake;
—
the level of the tangential rs reaction is equal to the value defined above to the I.1.3 clause (5) for short-term application of stress;
—
the module values describing mobilization efforts resistant versus displacement may be significantly higher (Note 2) as defined for the short period of application of stresses (Figure I.1.4.1).
NOTE 1 - This clause does not apply in case of liquefiable soils. NOTE 2 - The loading factor can commonly reach a value equal to 3. This increase is related to the variation of soil shear modulus as a function of the distortion. More detailed information is available in professional recommendations.
I.4 Other calculation model (1) The correlation between the penetration resistance and the limit pressure used to estimate the reaction module Kf and the bearings r1 and r2 from the penetrometer data. In this case, the relationship to use are: II
(I.4.1) O
r, ß = B
(I.4.2)
ß
(I4.3)
r = bq
qc is the penetration resistance measured peak electric static penetrometer; p1 and p2 are function parameters of the soil type in the pénétrométrque method (Appendix G) and defined in I.4.1 and I.4.2 tables.
Table I.4.1 - p coefficients to calculate Kf from sth
Soil type
soils chalk
Intermediate 2.05
and
Clay soils Ir> 2.6
marl P
4.5
7.5
4.5 12
Table I.4.2 - Coefficients p 1 and P 2 for calculating r 1 and r 2 from sth Type ground
sandy soils IR <2.05
soils intermediate
chalk and
clay soils IR> 2.6
marl
2.05
13
5
13
10 ß2
3.5 8
6
8
NF P 94-262
Appendix J (Informative) group effects vis-à-vis an axial loading
J.1 Application - Definition (1)
The provisions of Annex J apply for the justification of ultimate limit states of global mobilization of the field of deep foundations under axial load according to the
provisions of sections 9 and 10 and for the justification of raising serviceability limit states ground under the base of a p ile group under the provisions of section 14.2 (Note 1). (2)
These provisions are applicable without modifications as foundations formed of circular piles or squares arranged in a square mesh under the distribution plate.
(3)
This annex defines the procedures for conducting the vis-à-vis checks two phenomena may reduce the lift of a pile group defined in clause 9.3 (3):
—
approximation of pious modifies mobilized reactions. This phenomenon mainly affects the axial friction. He speaks with an efficiency this;
—
the overall behavior of the group consisting of pile group and enclosed land which may have a lower strength because of its interaction with the surrounding ground.
J.2 Effect group linked to reconciliation stakes - efficiency coefficient This (1) The group of related effects approximation piles affects the axial friction of a pile group. The reduction is expressed by a coefficient of efficiency it. The lift of the Rg group is then given by the following relation (J.2.1):
Rg = î Rbg + c. î R "
i=1
(J-2.1) i=1
Is the coefficient of efficiency; Rg is the r esistance boundary of a cluster of n piles; Rb i is the peak strength limit of a pile i isolated supposed group; Rs i i s the axial boundary friction resistance of a pile i isolated supposed group. (2)
In the case of a group of pious m n lines stuck in a homogeneous soil, failing more precise justification based on theoretical and experimental bases, it should determine
the coefficient of efficiency This from the following r elationships: d is the distance between the piles;
this =
(J.2.2)
when d> 3 B 1
(( C e
1-2C
N O January 1 Yi T 1 'D N I -iwith: Cd = 1 ---------------------- 1 + 17 m not )) ) VB) d 4l
when 1 <- <3
d B
(J.2.3)
NF P 94-262
B is the diameter piles; m is the number of piles lines; n is the number of piles by lines. (3)
In the common situation where the stakes through poor resistance layer and are anchored to the base in a very firm ground, the group effect played little and it is
acceptable to adopt a value of the coefficient of efficiency This equals 1 .
J.3 group effect linked to the behavior of the box (1)
One should check that the lift of a group of deep foundations, considering it
as a monolithic block, that is to say as one foundation element, is sufficient vis-à-vis the vertical load transmitted by lowering the scope structure. (2)
The evaluation of the lift of R group can be based on the following method which apply
if d <3 B: —
it should consider all the piles and soil they enclose as a monolithic bloc, excluding any inclined piles;
—
the monolithic block limit load floor is calculated by summing the limit axial friction (in the layers where it is positive) and the breaking stress at the base of the block;
—
the axial friction is equal to the ground-ground friction, estimated from the short-term or long-term shear values measured or deduced by correlation from test results in place;
—
the lift factor is one of deep foundation or shallow foundation according to the slenderness;
—
according to its equivalent recessed, this block is regarded as a shallow foundation, semi-shallow or deep.
J.4 compaction estimated deep foundations group (1)
For all the methods defined above, the compaction of the pile group and floor of the monolithic block is to be determined according to methods adapted calculations
(reaction coefficient method or finite element method or finite difference). It is necessary to consider the adequacy of the settlement of piles and ground up. (2)
When a pile group is implanted in clayey or loamy soils with growing modules approximately in proportion with the depth (normally consolidated soils), we can apply the
calculation scheme Terzaghi, which consists in considering an imaginary tread in 2/3 of the pile length and apply it throughout the load on the foundation. (3)
When a deformable ground layer is present below the anchoring soil of a pile group (Figure J.4.1) it is necessary to evaluate the share of the load which is exerted at the
base of the piles, including any negative friction and then apply a load distribution scheme to the roof of the deformable layer of soil, for example in a 1/2 slope of the truncated cone, and finally to calculate the packing the deformable layer with the constraint thus obtained.
NF P 94-262
Figure J.4.1 - Calculating a compaction pile group according to the method of Terzaghi
J.5 Interaction of the tip between two neighboring deep foundations (1)
It is necessary to draw attention to the fact that the deep foundations built on the property line can also mobilize the reaction of the soil mass on the outside of the property.
Their bearing capacity may therefore be reduced if future work i s undertaken on the neighboring property. (2)
More than 3 diameters centerline to centerline, there is no interaction of the tip of a pile on the neighboring pile and thus the transverse thrust induced by a pile on each
other when the first has its leveled low higher than the second is negligible. (3)
A stake realized after the loading of another (case of delayed construction of two neighboring buildings) and located more than three diameters of the latter is not affected
by the mobilization of the tip of the other stake since the stress state of the soil around the new stake is not changed. However, when the spacing shaft axis is less than 3 diameters, appropriate to test the i mpact of a pile on the other because the initial stress state can then be disturbed by the realization.
NF P 94-262
Appendix K (Informative) horizontal displacement of a land layer
K.1 Scope (1) These rules relate to the measurement of the horizontal displacement of a compressible layer subjected to an asymmetrical load embankment (Notes 1 to 4). NOTE 1 - This horizontal movement, denoted g (z), is involved in the justification of the elements of a deep foundation through the compressible layer. NOTE 2 - The estimated traveling and represents the movement "free" ground in the absence of the foundation. NOTE 3 - Some or all of these rules are to be applied in the absence of more precise information (measurements on site, measures in case of similar studies, specific studies, etc.). NOTE 4 - Strictly speaking, the presence of the foundation changes the distribution and amplitude of movements of the ground, but there i s currently no easy way to account for this i nteraction.
K.2 Principle of the method (1) The method is applicable to a compressible layer of thickness D loaded by a height of embankment H, yr volumetric weight, and angle of slope p.
Figure K.2.1 - Moving the slope foot floor - Scope When, after a certain depth h0 load provided by the backfill is less than ap - Î0 °, is given D value h0 (at being the preconsolidation pressure, at v0 the vertical earth pressure at the point considered). (2)
NF P 94-262
(3)
It is assumed assumed that the the horizontal horizontal displacement displacement of the soil expressed as a function function of depth depth z in compressible soil and the time t is of the the form:
g (z, t) = G (Z) gmax (t) where: Z = D
(K.2.1)
K.3 Determination of G (Z) (1) The curves G (Z) are given, as the case (K.3 Clause (2)) by one of the following two expressions, illustrated by FIG K.3.1:
—
curve 1: G (Z) = 1.83 Z3 - Z2 4.69 2.13 + Z + 0.73 (K.3.1)
—
(2)
curve 2: G (Z) = Z3 + -2.0 1.5 + 0.5 Z
(K.3.2)
curve 1 is used in the general general case. Curve 2 is used when there is on the the surface, over over a significant significant height (> 0.3 0.3 x D), a less deformable deformable layer than the deeper layers.
Legend: Y: N - X: G (z) Figure K.3.1 - function G (z)
K.4 Determining gmax (t) K.4.1 Principles (1) gmax value (t) is obtained from the following expression:
NF P 94-262
9max (t) = 9max (0) + Ag
(K.4.1)
max (t)
gmax (0) is determined in accordance with K.4.2; Ag ma x (t ) is de te rm in ed in ac co rd an ce wi th K. 4. 3; t = 0 cor re sp on ds to th e en d of co ns tr uc ti on of th e
embankment.
Figure K.4.1 - Determination of gmax (t) - Notations K.4.2 Determination of gmax (0) (1) When the safety factor to the great slip F is greater than 1.5 and that the embankment embankment is put in place relatively quickly , gmax (0) is obtained as shown in K.4.1 (2), involving the following parameters: —
average cohesion:
c
—
u = D f (z) z
(K42
i)
dimensionless parameter characterizing the undrained soil strength strength cu relative to the charge level YRH:
+ 2 h
(not
(K.4.2.2) YRH
- parameter characterizing both the position of the pile relative to the crest of the embankment and the slope of the slope (0
(K.4.2.3)
(f) for 1
4 f > 3 F for: 85 (f ) = April cu (z) i s measured field vane or default determined from=laboratory )tests = or correlation with field tests. A (m, f )
(K.4.2.6) (K.4.2.4) (K.4.2.5)
(2) gmax (0) is determined as follows, for f> 1.1 (Figure K.4.2):
NF P 94-262
Figure K.4.2 - Determination of gmax (0) - Abacus K.4.3 Determination ATgmax (t) (1) It is assumed that Agmax (t) is connected to the settlement based on the axis of the fill, in current section, by the following relationship:
AT
S max (t) = r [s (t) - s (0
s (0) i s the compaction at the end of the construction of the embankment; embankment; s (t) is the compaction at the instant t. r is an experimentally determined determined coefficient from measurements at different sites, given in Table K.4.3.
)]
(K 43 )
NF P 94-262
Table K.4.3 - Values of coefficient r Embankment) 0.5
Situation
r
foot embankment
0.16
Peak embankment
0.25
tan P = 0.4 - foot pad
0.08
tan P <0.5 b) tan P = 0.25 - foot pad a)
0,035
to tanp given, r decreases as the distance to the foot of the embankment increases, ie with tan
p.
K.5 Determination of g (z) in the compressible layer K.5.1
b)
Length embankment and tgp less than 0.5, the value of the coefficient r decreases with tgp (see data values
indicative for TANP = 0.4 TANP = 0.25).
case the foundation is carried out before the embankment (1) In this case (Note 1), moving to take into account is the total displacement between the initial state and the moment = " ie:
(Z) = G (Z) with H gmax: Z =
z
(K.5.1)
D
NOTE 1 - This way of working, highly recommended, can be made necessary by the demands of the site.
K.5.2 case or foundation is performed after the embankment (1) In this case, the move to consider is the displacement between t = t1 realization of the foundation and t = ", or:
g(z )=G ( Z ) r KOW) -s (t i )] Where: Z =D
K.6 Determination of g (z) in the embankment (1) Whether it is between the foot and the crest of the embankment, ie when P
^ (Notes 1 and 2), it i s assumed that g (z) for z <0 is a linear function of z determined by: —
the value g (0) at the surface of the compressible soil;
—
the g value (H) corresponding to the upper surface of the embankment.
NOTE 1 - For the study of the movement of the embankment, it extends the validity of domain P 'P'> n / 2.
(K.5.2)
NF P 94-262
NOTE 2 - It is advisable to perform calculations with fork assumptions seeming the most likely following the case. Among these include the following: —
the displacement is uniform in the embankment, g (H) = g (0);
—
the displacement corresponding to the upper surface of the embankment is zero, g (H) = 0;
—
the displacement corresponding to the upper surface of the embankment is opposite in direction to that of the compressible soil and is: g (-H) = -g (0).
NF P 94-262
Appendix L (Informative) axial stiffness of a deep foundation
L.
1 Scope
(1) These rules concern the assessment of the axial stiffness vis-à-vis the axial force of a single element of deep foundation. It is permissible to use the proposed methods (Note 1) when the standard rules given in section 8.5.1 are deemed insufficient precision. NOTE 1 - Two methods are proposed: —
an evaluation method from the creep load RCT (Article L.2). This is certainly the most accurate method when conducted load tests. Otherwise, we may consider that this method is satisfactory for the calculation of stresses in the different elements of the same foundation, but that provided displacement values are indicative.
—
an evaluation method from the laws of mobilization of axial friction and effort peak (the one from Frank Zhao), which generally allows a satisfactory assessment of displacement (settlement) deep foundations when not method for load tests. It is described in Article L.3.
L.
2 Feedback from charging parameters
(1) In calculating the stress, it is assumed that the element foundation behaves resiliently and linear and the axial stiffness of the element is taken equal to its secant stiffness between 0 and the creep load Rcr. It was in this case: —
vis-à-vis short-term load application: R K = - ^ - lō
(L.2.1) v
shout
S
Ki is the stiffness value of deep foundation element for short-term load application; Rcr is the value of the creep load;
Scr; i represents the depression caused by the assumed Rcr load short period of application;
—
vis-à-vis long-term load application: R K
v
Kv is the stiffness value of deep foundation element for long-term load application; Rcr is the value of the creep load; Scr; v represents the depression caused by the assumed load Rcr long term application.
S ".
(L.2.2)
'
NF P 94-262
(2)
When adding one or more tests of representative piles, Scr; Scr i and v must be estimated from the results of these tests, taking into account possible differences in
geometry between the test piles and actual piles. They can be taken equal to the depressions in the creep load corresponding to t = 1 h and extrapolated to t = 1 year. (3)
In the case where the Rcr creep load is determined from Pressuremeter or penetrometer test, one must determine the values of SCR; i and Scr v from the following
relationships: o, B
S = k --------------------- + andi
(L.2.3)
eli represents the instantaneous shortening in the Rcr load the part of the not included in the field element.
B - k -------------- + eh
S
cr v
100 1
(L.2.4)
elv is the shortening of the portion of the member not included in the ground when the l oad is assumed Rcr maintained indefinitely; k is an empirical factor, usually taken equal to 2 if more representative value.
L. 3 Assessment from the mobilization laws of axial friction and advanced effort (1)
The head settlement of an isolated deep foundation can be calculated if one knows the fricti on mobilization laws t depending on the vertical displacement s deep
foundation in each section of it, and the law of mobilization q the peak effort according sp vertical displacement thereof. The method of Frank and Zhao below to determine these laws from pressiometric EM module, the axial friction values qs boundary and the strength limit peak qb, calculated in the manner defined in Appendices F and G (Figure L.3.1).
Figure L.3.1 - Evaluation of the axial stiffness of a pile from mobilization of laws axial friction and the effort point
(2) may be adopted, for both elements fought for elements drilled the following rules (Notes 1 to 4) - for fine soils:
k
T
2,
0 Em B
. Em = 11.0 q
B
(L.3.1)
NF P 94-262
- for granular soils:
k =
0,8Em
(L.3.2)
B
NOTE 1 - The results of this method are regarded as representative only for less than or equal to 0.7 Rcr l oads, which represent the loading area on which i t was keyed. NOTE 2 - By cons, in this range of loading, we can consider that the duration of the load does not introduce significant difference in behavior of the soil. This method can be applied to both long loads of short duration of application, taking into account, however, the rheology of the material of the pile. NOTE 3 - After numerical solution, this method allows to trace the load-deflection diagram head between 0 and 0.7 Rcr and deduce the overall axial stiffness of the pile. NOTE 4 - These rules have been established for piles having a diameter between approximately 0.8 and 1.2 m.
NF P 94-262
Annex M (Informative) geotechnical characteristics and values land properties
M.1 Recognition of courses (1)
Articles 3.2 and 3.3 of the standard EN 1997-1 and Article 2 of the NF EN 1997-2, taking into account the particulars in this Annex, allow the development of land reconnaissance
and evaluation geotechnical parameters. (2)
The following aspects should be considered in developing the content of the geotechnical (Notes 1 to 3):
—
reliably identify the provision and nature of training concerned with achieving the pious;
—
providing geotechnical, mechanical, hydraulic and electrochemical properties of the soil layers required for the design and justification of the stability of the pile foundation;
—
clamping the webs (free or ground) for the calculation of the pile foundation.
NOTE 1 - The article essentially aims knowledge of the original soil layers of the stock piles and those which develop the geotechnical resistance and the conditions of external and groundwater, to allow the establishment of a model geotechnical reliable. NOTE 2 - The training under the base of the piles are known, usually to a depth of 3 to 5 times their diameter, and well beyond, in some design situations, such as when a ground layer low resistance is likely to occur under the r estraint foundation layer, and may be r equested by the pile group. NOTE 3 - geotechnical can also have as objectives, providing information necessary to choose the technique of execution and identification of difficulties that may arise during construction. It is assumed here that the content of the recognition is essential purpose the calculation of the book. (3)
Polls and tests to be performed in field and laboratory are selected to obtain directly (Notes 1 and 2) the desired information (arrangement of the layers, the mechanical parameters
of strength and deformation of land, l and permeability, etc.), in taking into account the following indications: —
the combined use of laboratory tests and up soil tests to better assess the representativeness and variability of results across the site; the pressiometric pl or penetrometer qc strength parameters are at least to provide for empirical calculation methods of lift described respectively in Appendices F and G;
— —
actual mechanical resistance properties and soil deformation 9 ', c', E ', v' and when necessary (fine soils) the total stress in properties of strength and deformation of cu soils, Eu are at least to provide for methods of analytical calculation and evaluation of negative friction; shear strength parameter values 9 'and c' of the fine soils consistent, are normally (M.2 Clause (2)) to deduce shear laboratory tests triaxial press (preferably drained consolidated testing (CD) or failing tests not consolidated drained with pore pressure measurement (CU + u)) on intact samples (Class 1 sampling); —
shear strength parameter values 9 'and c', of fine or coarse granular soils are normally derived shear laboratory testing, triaxial press, or the shear box, on soil specimens saturated desired reconstituted to the density of the soil i n place;
—
several shear tests in each layer of soil are normally carried out to obtain representative strength properties.
NOTE 1 - It is pertinent example to perform core drilling completed by identification tests to define the layout and nature of the terrain layers. Also it is preferable to perform laboratory shear tests in sufficient numbers to access soil shear strength parameters rather than using correlations, etc. NOTE 2 - Annex A of the NF EN 1997-2 specifies the parameters can be deduced directly from each soil test. The tables M.1.1 and M.1.2 below recall and supplement these data by presenting a list of French standards on these aspects. They indicate, respectively, for field trials in field and la boratory, the directly measurable parameters, soil types concerned and additional information that may be drawn from the test. For these areas, NF type of EN developed at European level also exist.
Table M.1.1 - Field testing in place a - Hydraulic parameters measured and can be deducted
NF P 94-262
Working area
Purpose of the test
derived parameters
pumping test (NF P 94-130) Estimate granular soil aquifers aquifers fine soils or rocky crossed by discontinuities network
- the average coefficient of permeability - pumping action radius
Permeability middle ground
- the pumping rate - the amplitude of the feeder
water test LUGEON (NF P 94-131) Evaluate the possibility of movement Rock
water in soil
cohesive soils suitably resistor (1)
Detect heterogeneities and
Number of LUGEON IU units (2)
cracking
water test LEFRANC (NF P 94-132) Granular or fine soils below the water table
Determine the permeability LEFRANC
Permeability LEFRANC kL (3)
Notes : (1)
compatible with the pressure of 1 MPa injected during the test;
(2)
a LUGEON unit is the average flow rate injected under a pressure of 1 MPa, expressed in l / minute and reduced to 1 m of drilling;
(3)
permeability LEFRANC kL sol (measured in a pumping or injection test) is expressed by Q / (mh B), Q: flow rate, h load m: coefficient of B form, diameter of the portion strainer.
NF P 94-262
Table M.1.1 - Field testing up (continued) Ground
b - resistance parameters and measured deformation and may be deducted measured parameters Stratigraphy derived parameters (1)
Ménard pressuremeter test (NF P 94-110-1) All types (except very soft or very loose soil)
limit pressure, pi flow pressure, m.p. Module pressiometric Ménard, Em
(2)
Fine soils: - cu (correlation with p |) coarse soils: - internal friction angle 9 ' - state of compactness (correlation with EM / p |)
Test scissométrique up (NF P 94-112) Soil consistent purposes su
undrained cohesion cu
-
<0.1 MPa
static penetration test (NF P 94-113) or test piezocone (NF P 94-119) Fine soils: - cu (correlation with QC)
Resistance to penetration of the cone, qc Friction unit axial qs Dm0y <20mm
*
(2) (3)
grained soils: - internal friction angle 9 '
pore pressure, u *
- state compactness (correlation with QC)
Dynamic penetration test A (NF P 94-114) Dav <60mm
advanced dynamic resistance, qd
(2)
-
(2)
-
dynamic penetration test type B (NF P 94-115) Dav <60mm
Number of sheep liked to penetrate the tip of 20 cm, ND20
penetration test corer (NF P 94-116) Dav <20mm
Number of sheep liked to penetrate the core barrel SPT 30 cm
(2)
N
grained soils: - internal friction angle 9 ' - density index Id (correlation with N)
Test phicometer (XP 94-120) Shear strength
-
Notes : (1)
the internal friction angle 9 'is in this case being indicative;
(2)
succession and homogeneity land layers may be deduced from a survey;
(3)
the presence of fine anomalies (alternation of sand and clay in a layer, for example) can be identified.
178
grained soils: - internal friction angle 9 '
NF P 94-262
Table M.1.2 - Laboratory tests
a - identification tests and land classification Ground measured parameters
Nature
State
By weight water content: oven method (NF P 94-050) all floors Water content, w YES Atterberg limits: Liquidity limits to the cup and plastic roller (NF P 94-051) - Lim it liquidity cone i NF P 94-052) d <400 | im liquid limit, wThe or wThec and plasticity, wP plasticity index, YES Ip density : Method of the cutting drum, the mold and immersion in water (NF P 94-053) fine soils Density, p YES density of the solid particles of the soil: water pycnometer method (NF P 94-054) all floors density of the solid particles, ps YES weight organic content: chemical method (NF P 94-055) all floors content by weight of organic materials, MO particle size analysis by sieving dry after washing (NF P 94-056) maximum grain diameter dmax granular Distribution d> 80 | im of particle size analysis by sedimentation (NF P 94-057) d <80 | im granular distribution of
Notes (1)
(2) (1) (1)
YES
-
-
YES
-
-
YES
-
-
Von Post Test: Decomposition State (humidification) organic soils (XP P 94-058) Soil MO> 10% Classification YES
-
-
YES
YES
-
YES
-
(1)
YES
-
-
-
minimum and maximum densities of cohesionless soils (NF P 94-059) Pdmax maximum density and minimum density d <50 mm Pdmin Index,ID Carbonate content: Method calcimeter (XP P 94-048) All soil, rock Carbonate content% Citœ3
Dry density of a rock element: method by hydrostatic weighing (NF P 94-064) rock Density, p methylene blue value of a ground by the spot test (NF P 94-068) All soil, rock blue value, .VBS
YES
normal and modified Proctor compaction test (NF P 94-093) d <20 mm Pof OPM YES (3) Notes: 36 The correlations used for the values of geotechnical properties must be appropriate to the terrain conditions and the test equipment used and documented (Note 1). If necessary, beare noted the bibliographic data that justify (1) other testit should methods possible, the cited method is that recommended; (2) testing the cone is most often used to determine the liquid limit; NOTE 1 - The correlations in the standard EN 1997-2 are examples of documented correlations. (3) modified Proctor (2700 kNm / m 36) Is preferable to the normal Proctor (600 kNm / m3)
;
M.2.1 geotechnical properties M.2.1.1 Densities land (1) The values of the specific gravities of up land required to share calculation are derived from the water content measurements and density performed in the laboratory or in place (Table M.1.2 a). In the absence of such measures, it is permissible to assign their standard values based on representative bibliographic data, provided that it results clearly increased security for the book.
179
NF P 94-262
Table M.1.2 - Laboratory tests
180
NF P 94-262
Table M.1.2 - Laboratory tests (continued) b - soil mechanics characterization tests Ground measured parameters
Nature
state
-
YES
-
YES
properties
direct shear test rectilinear box (NF P 94-071-1) d <8 mm
Internal friction angle ^ p and cohesion C'p peak angle of internal friction ^ 'r and r esidual cohesion C'R
shear test alternated in the box (NF P 94-071-2) d <1 mm
Internal friction angle ^ p and cohesion C'p peak angle of internal friction ^ 'r and residual cohesion C'R
Shear tests UU, CU and CD + u to the triaxial revolution i all floors
undrained cohesion cu internal friction angle, 9 'and cohesion c effective
NF P 94-070 and NF P 94-074) -
YES
c
0
c
swelling test oedometer (XP P 94-091) fine soils
-
YES
-
YES
swelling pressure o'g swelling resistance, R
compression test oedometer with stepwise loading XP P 94-090-1) fine soils
consolidation pressure, o'p Coefficient of compressibility Cc Cv (2)
Notes : (1)
CCU and 7cu are the parameters for calculating improving cohesion with the constraint;
(2)
Cv is the coefficient of soil consolidation.
M.2 Land up (1)
The geotechnical properties of the terrain and the characteristic values of geotechnical parameters to be determined in accordance with sections 2.4.3 and 2.4.5.2 of
standard NF EN 1997 (Note 1), taking into account indications of articles and M.2.1 M.2.2 it -Dessous. NOTE 1 - It is particularly i mportant that this choice is based on the measured values and the values derived i n situ testing and laboratory supplemented by the lessons learned and the retention characteristic value for a geotechnical parameter is an estimate conservative value that influences the limit state considered (Article M.2.2). (2)
To determine the geotechnical parameters of soil and rock, national standards tests indicated in Tables M.1.1 (tests on land in place) and M.1.2 (laboratory soil testing),
as well as European standards 'soil tests not referenced in this document can be used. 3
M.2.1.2 Shear strength (1)
The values of shear strength parameters (angle of internal friction, cohesion) of the lands are determined (M.1 Clauses (2) and (3)) from shear tests on laboratory sampling
class samples 1. (2)
The shear parameters of drained soil are to be determined by distinguishing, where applicable (overconsolidated soil), the overconsolidated field and normally consolidated
area (Figure M.2.1.2), taking into account where necessary the consolidation stress obtained in the load tests oedometer to d elimit these areas (Notes 1 and 2). NOTE 1 - In the field overconsolidated, the failure envelope is not linear. It is usually accepted to consider the upper part of the load surface as linear. NOTE 2 - In the normally consolidated area, the failure envelope is li near and effective cohesion is normally zero. However, it i s usual to consider cohesion "measured" by limiting the 5 to 10 kPa.
181
NF P 94-262
Legend: Y FIG M.2.1.2 - failure envelope Example of saturated overconsolidated clay obtained Ala triaxial press at consolidated shear tests drained (3)
When laboratory tests are not possible (eg when the nature of the terrain does not permit representative sampling), it is permissible to infer the values of shear strength
properties of the recognized grounds correlations (Notes 1 3), connecting them to strength properties or properties of nature and condition of the ground measured in the field or laboratory, and / or derived from representative bibliographic data. NOTE 1 - Examples of such correlations are given in Annexes D and F of NF EN 1997-2 standard. to estimate the angle of friction f 'non-cohesive soils, respectively from tests on the ground up to the static penetrometer (CPT) and penetration test corer (SPT). NOTE 2 - Procedures are also available in the literature to estimate the friction angle f 'non-cohesive soils, based on test results to Ménard pressure, for example those proposed by O. Combarieu or J. Monnet. NOTE 3 - In general, the greatest caution is advised when the choice of the value f 'adopted in the calculations. In any event, it is highly advisable to book these proceedings to the pre-design of the structures, or evaluation of specific actions as negative friction.
M.2.1.3 deformation modules (1)
Land values of deformation modules from tests are determined and interpreted appropriately to the project requirements and the calculation model used (Notes 1 to 3).
NOTE 1 - Usually, in this case to model the loading of the field is adopted as a module that based on the initial part of the stress-strain curve and to model the unloading of the land is adopted one taken from a loading-unloading cycle . NOTE 2 - Ménard pressuremeter modules are not generally suitable for modeling a loaded field in a linear elasticity model. They are to be used directly against to determine the value of the reaction modules (Annex I) when calculating displacements of a pile from a model soil-structure interaction to the reaction module. NOTE 3 - Ménard pressuremeter modules are used directly to determine the laws of friction mobilization t depending on the vertical displacement s stake in each section of it and the law of mobilizing peak effort based on vertical movement thereof, from the empirical method proposed by "Frank - Zhao" (Annex L), to estimate for example the head settlement of a single pile. (2)
When laboratory tests are not possible (eg when the nature of the terrain does not permit representative sampling), it is permissible to determine land values deformation
modules from appropriate up trials taking into account nonlinear and inelastic behavior of land (Note l). NOTE 1 - This article aims tests by wave propagation in the soil for modeling the behavior of a load ground under very low deformation (Figure M.2.1.3) and to model its behavior in unloading, when using a calculation model of soil-structure interaction finite element or finite difference.
M.2.2 Characteristic values of geotechnical parameters (1) In general, it i s possible to determine, in accordance with Table M.2.2.1: —
initially low values and average values of geotechnical parameters by taking account only of the stratigraphy of the land layers and variability parameters in the same layer (Note 1)
—
then in a second time, the characteristic parameter value within the range as determined in consideration of the work and the field concerned by the volume limit state considered (Note 2).
NF P 94-262 NOTE 1 - The characteristic value can be determined with reference to a calculated probability of a worst value which governs the occurrence of the limit state studied not exceeding 5%, and the average value is determined with reference to a calculated probability a worst value that governs the occurrence of the limit state studied does not exceed 25%. NOTE 2 - The recommended procedures in this case are those proposed by F. Baguelin and JB Kovarik (2)
37
In practice, for the calculation of deep foundations, it is necessary to retain the low values determined as indicated above in M.2.2 (1) or alternatively, resistance patterns or
ground deformation moduli determined so more empirical , provided that it results clearly increased safety for the work (Note 1). NOTE 1 - For example, the lower envelope of the time profiles of mechanical parameters with measured under a measurement of 20 below the selected profile.
37
F. Baguelin JB Kovarik, a method of determining geotechnical parameters characteristic values, French Journal of Geotechnical 93.
NF P 94-262
G: shear modulus - G0: shear modulus at low deformation - ed: déformationdéviatorique (spec the deviatoric part of the strain tensor)
Figure M.2.1.3 - typical area of use of land deformation modules test apparatus for determining the
Step
Table M.2.2.1 - Principle for determining characteristic values and calculating land properties
Properties land
Basic calculations
measured values and / or values derived
geotechnical and / or correlations and / or experience
Average value, low value Xm, Xb '
Geotechnical Hydrogeology +
1
2
Geotechnical Hydrogéologie + + + limit state calculation method 3
characteristic value Xm
4
Value calculation, Xd = Xk / uM
NF P 94-262
M.3 reported Materials
Appendix N (Informative)
(1) For project studies, it is accepted, unless otherwise indicated market and except for cases covered by M.3 clauses (2) and M.3 (3), taking into account a density equal to 20 kN / m3 to soils reported outside ply and equal to 22 kN / m3 to saturated reported soil (Note 1). NOTE 1 - The reported soils are considered saturated when they are under the tablecloth.
(2) In the case where the specific gravity of the reported materials is likely to be favorable vis-à-vis a given combination of action, it is assumed, for this combination, the volume weight of soil reported outside ply and saturated soils reported are 18 kN / m3 and 20 kN / m3, however, these values are justified by performance testing (Note 1). NOTE 1 - If the actual measured values are worse than those adopted for the project, it is necessary to consider the consequences on the stability of the structure. (3) Where use is made of a volume is set by the market. reported material of particular origin, it is appropriate that its weight
185
NF P 94-262
Deformations of structures and foundations movements
No.1 Preamble (1) are given in this appendix guidance on the generally accepted values to ensure a satisfactory service behavior of building structures to set realistic criteria for acceptable travel for pious when associated with these structures.
N.2 Deformation structures and foundations movements (1)
The components of foundation movement, which should be considered are compaction, the compaction relative (or differential), rotation, tilt, deflection, relative deflection,
relative rotation, horizontal movement and the amplitude vibration. The definitions of certain terms relating to the movement and foundations deformations are given in Figure No.1. (2)
It is unlikely that the maximum permissible relative rotations for structures with open frames, frames with filling and bearing walls or walls in solid masonry are the same
but they will likely range between about 1/2 and about 000 1/300 to prevent a serviceability limit state is reached in the structure. A maximum relative rotation of 1/500 is acceptable for many structures. Relative rotation for which it is probable that ultimate limit state is reached is approximately 1/150. (3)
The values in the N.2 clause (2) apply to the case of a deflection of the structure, as illustrated in FIG N.1. In the case of a negative arrow (the edges tamp more than the
middle), the values should be halved. (4)
For common structures isolated foundations, total settlements up to 50 mm and 20 mm differential settlements between adjacent columns are often acceptable. Larger
total and differential settlement can be admitted if the relative rotations remain within acceptable limits, and if the total settlements do not cause problems for networks related to work or tilting, etc. (5)
The guidance above the limits settlements apply to current literature. It should not apply to buildings or structures unusual or where the intensity of the load has an uneven
distribution very pronounced.
No.3 Arrows in reinforced concrete buildings (1) The limit arrows that should generally provide a satisfactory behavior of structures such as homes, offices, public buildings or plants are given in clauses 7.4.1
(4) and (5) of EN 1992-1-1 standard. They are derived from ISO 4356 to which reference should be made for more information on deformations and their limits.
NOTE 1 - The article refers to buildings where there is no particular requirement for the proper operation of machines supported by the structure or to avoid ponding on flat roofs. (2)
The appearance and the general functionali ty of the structure are likely to be altered when the calculat ed deflection of a beam, a slab or a console subjected to quasi-
permanent fillers is greater than l / 250 (l denotes the scope of the work). (3)
For deformation after construction, / 500 is normally adequate to limit the quasi-permanent loads.
NF P 94-262
Appendix N (Informative)
a)
definitions compaction s, differential settlement Ss, rotation <9 and angular deformation
b)
definitions of deflection A and the deflection relative A / L
c)
definitions of the inclination © and the relative rotation (angular distortion) p
Figure No.1 - Setting the foundations of movement
187
NF P 94-262
Appendix O (Informative)
Checklist for construction supervision and monitoring of works ducomportement
O.1 General (1)
We list in this Annex the most important points (Notes 1 to 3) to be taken into account in monitoring the performance of work (Section O.2) and monitoring the behavior of
the structure ended (section O.3). NOTE 1 - In general, the work is done according to plans previously established. If during the work, it is found that the physical characteristics, mechanical, chemical or electrochemical field or the table do not match the predictions, it should verify the i nformation and make the appropriate changes if necessary. NOTE 2 - The importance of the points varies depending on the project. The list is not exhaustive. NOTE 3 - known approach "observational method" in which the design is reviewed during construction is generally not suited to the case of pile foundations. Nevertheless, it shows in M.4 section points to consider when such a procedure is adopted
O.2 Monitoring compliance O.2.1 general Checkpoints (1) The general inspection points are: —
check field conditions and the location and the overall layout of the structure;
—
flow of groundwater and pore pressure regime; effects on webs pumping operations; effectiveness of the measures taken to control seepage flow; process of internal erosion and Fox phenomenon; chemical composition of groundwater; corrosion potential;
—
movements, lamination, stability of the walls and base of the excavation; temporary support systems, effects on buildings and surrounding equipment; measurement of soil pressures; measuring variations in pore pressure due to excavation or loading;
—
security of persons taking into account the geotechnical limit states.
O.2.2 water flow and pore pressure (1) Items to consider are: —
ability of the system to ensure control of pore pressures in all aquifers where excess pressure could affect the stability of a structure, including artesian pressures in aquifers located below the excavations; discharging the water extracted from the dewatering systems; lowering the water table throughout the excavation to avoid quicksand conditions, internal erosion and remodeling of land by construction equipment; deflection and removal of rai nwater and other surface water;
188
NF P 94-262
—
effective and efficient functioning of the lowering of the whole table system throughout the performance of the work taking account of clogging strainers wells, silting wells or cesspools, abrasion in the pumps, the clogging of pumps;
—
Control of web drawdowns to prevent disturbances in adjacent structures or adjacent areas; observation of the piezometric levels; efficiency, operation and maintenance of water recharge systems, if necessary;
—
non-driving fine control;
—
settlement structures or surrounding land;
—
effectiveness of drainage systems by subhorizontal drilling.
O.3 Monitoring Behavior (1) The general points to consider are:
—
ground settlements, especially in the case of a lot of poor quality;
—
lateral displacement and distortion of the structure, particularly in conjunction with the fill implementation, deposits and other material surface charges and water pressures;
—
behavior of terraced structures with multiple points per profile for indications of differential settlements;
—
piezometric levels behind and under the structure or in adjacent areas, especially when a deep drainage or permanent dewatering systems of are installed;
—
measuring the flow rate drains.
M.4 Implementation of the observational method (1) When the "observational method" is retained (O.1 (1) Note 3), the provisions of Article 2.7 of the standard EN 1997-1 apply (Notes 1 to 3). NOTE 1 - The following list recalls the points to consider before beginning construction. —
the limits of the pile foundation of the acceptable behavior must be established;
—
the field of possible behaviors must be analyzed and we must show that there is a reasonable probability that the actual behavior is within the range of acceptable behavior;
—
an instrumentation plan should be established, to verify the actual behavior is between acceptable limits. Monitoring should be demonstrated clearly and as soon as possible and with a frequency measurement that allows to effectively implement measures to rectify the project;
—
the measuring instruments of response times and results analysis procedures must be fast enough compared to the possible evolution of the system;
—
a backup action plan should be established, to be implemented if monitoring reveals an outgoing behavior acceptable limits.
NOTE 2 - The following list recalls the points to take i nto account during construction. —
monitoring is executed as planned. ;
—
the results of observations are analyzed at appropriate stages of the project and must implement the safeguard action plan if it exceeds the limits of the authorized behavior.
—
the measuring equipment is either replaced or extended to incidents, to provide reliable data of appropriate type and in sufficient quantity.
NOTE 3 - It is possible to refer to the guides addressing the design of geotechnical structures from the observational method.
NF P 94-262
Appendix P (Informative)
Geotechnical categories and life of the project
P1 General (1)
The minimum requirements for the scope and content of geotechnical investigations, calculations and implementing controls are established in accordance with DIN EN
1997-1, completed by the provisions of its national annex referenced NF EN 1997-1 / NA (Note 1). NOTE 1 - In order to establish the design requirements, the complexity of each work must be i dentified and the risks associated with its construction and geotechnical category of the project is based on site conditions and the consequences of failure or damage to the structure to be built, taking into a ccount the life of the structure. (2)
The complexity of a work is identified before undertaking the design and rationale (Notes 1 and 2).
NOTE 1 - This appendix provides guidance to establish the geotechnical category of a work, the duration of use and class implications of the project. NOTE 2 - The complexity of a project is to be set by the owner or his representative before the start of the studies. It i s to specify possible as and whe n they progress.
P2 result Classes (1)
The consequence of class destruction or damage to the structure to be built vis-a-vis the people, books and neighboring buildings and vis-à-vis environmental protection is
established by distinguishing as specified in the standard EN 1990: —
low impact (CC1), having low or negligible effects on people, on the book building or surrounding buildings, in social, economic or environmental terms;
—
medium impact (CC2), with moderate effects on people and / or significant impact on the structure to be built or surrounding buildings, in social, economic or environmental terms;
—
high consequences (CC3), having significant impacts on human lives and / or very significant impact on the structure to be built or surrounding buildings, in social, economic or environmental.
P3 Geotechnical Category (1)
According to the National Annex to DIN EN 1997-1, project geotechnical category is defined taking into account the indications of Table P.3.1.
(2)
site conditions (simple, complex) must be established on the basis of knowledge of the topography of the site, the nature and properties of soils, the water regime of the
project site. (3)
The classes of consequences (ICC, CC2 or CC3) are established taking into account the indications of section P2.
Table P.3.1 geotechnical categories based classes accordingly and site conditions and justifications bases
190
NF P 94-262
CLASS RESULT
TERMS OF SITE
CATEGORY GEOTECHNIQUE has
Simple and known
BASIS OF JUSTIFICATION
Experience and qualitative geotechnical admitted 1
CCI complex 2
geotechnical and necessary calculations
simple 2 CC2
CC3
complex
Simple or complex
3
and depth geotechnical calculations
3
at
There are no set rules for the choice of the geotechnical category. In practice, however, it is considered that a book based on wishful succession under category 2, and
geotechnical category is Class 3 books set in an unstable site, or significant seismic risk conditions, or in changing soil or sensitive nuclear work, LNG storage, etc.
P4 design working time (1)
The rationale for a pile foundation and characteristics of products and materials to implement can be linked to the project useful life. It is therefore appropriate to fix it
before undertaking the design and justification of a pile foundation (Notes 1 and 2). NOTE 1 - Indicative times design working normally applied to building and civil engineering works, are given in Table AN.1 the National Annex to EN 1997-1 standard. NOTE 2 - F or protection against corrosion of prestressing steel (which can be used for example to produce micropiles) should be distinguished falsework and the works of more than 2 years service life.
NF P 94-262
Appendix Q (Informative) general design provisions for bridges
Q.1 Constituent materials piles Q.1.1 concrete, grout or mortar (1) For bridges, the provisions of section 6.4.1 concerning the verification of structural strength a concrete pile, grout or mortar are supplemented by the f ollowing specifications: —
the Cmax is limited to 25 MPa;
—
the k3 value specified in clause 6.4.1. (7) can be adapted according to the following recommendations: k3 = 1.2 in the case of enhanced control of the quality and
(2)
According to NF P 94-160-1 (Sonic through method). In this case, the tubes used, 40 mm minimum inside diameter, are placed so as not to harm the coating of the main auscultatory methods (1) AT B According to NF P 94-160-4 (vibration impedance method).
reinforcement cages. Works (3)
(4) EN kind of standards will replace the type of standards NF P 94-160 when they are applicable. Number of pious concerned 100% by transparency (2)
80% by transparency (2) + 30% impedance (3)
Notes: (1) A or B flaw detection procedures can be used interchangeably. continuity of the drum. For piles of bridges, enhanced control is to listen all the pins of the work by Method A or Method B (Table 6.4.1.2 is replaced by the table Q.1.1). Table Q.1.1 Minimum number of piles or webs to listen to enhanced controls
Bridges Integrity
Q.2 Structural strength piles Q.2.1 Piles or foundation reinforced concrete (1)
The piles or foundation elements must be reinforced throughout their length when supporting civil engineering structures such as bridges and underpasses.
Q.2.2 States under normal loading Service limits (1) The justifications required by the NF EN 1992-2 (Concrete bridges - Design and detailing rules, which refers itself to the NF EN 1992-1-1) and its National Annex (NF EN 19921-1 / NA) is supplemented as follows (these provisions provide to consider an allowance on the diameter as indicated in section 2.3.4.2 of the NF EN 1992-1-1)
NF P 94-262
(2)
The average compressive stress of the concrete on the pressed surface thereof is limited to 0,3k3fck * (Article 6.4.l);
(3)
The tensile stress of reinforcements or sheaths, when these are taken into account in the strength of the section is limited to two thirds of the steel yield strength (Note 1).
NOTE 1 - Attention is drawn to the importance, for deep foundation elements, the compatibility between the provisions of the frames and the proper placement of concrete (Clause 9.8.5 (2) of the NF EN 1992-1-1). It is advisable to ensure good motivation restraint exposure class and ensure that constructive provisions reinforcement can be met. (4)
For load cases with almost permanent LIVE, the resulting axial forces exerted on the deep foundations must not account for a traction state.
Q.3 Construction requirements Q.3.1 Principles (1)
In the absence of particular constraints, the plan arrangement of elements of a foundation (that is to say the elements connected by the same bonding pad) must:
—
to ensure a uniform distribution of axial loads between the different elements, as quasi-permanent combinations of actions;
—
to ensure the centering of the elements or groups of elements in the portions of the structure transmitting the stresses to the foundation.
(2)
Unless otherwise specified, all components of the same foundation (concrete, metal, etc.) must have the same constitution. It should, moreover, they are implemented in
the same conditions.
Q.3.2 piles prefabricated reinforced concrete (1) Unless otherwise provided, the following applies (Note 1): —
the longitudinal reinforcement are, wherever possible, a single length. If it is not so, recoveries or welds are not interested in more than a third of the number of bars in the same cross section and are at a distance of upper extremities or equal to six ti mes the smallest transverse dimension of the stake;
—
the diameter of the longitudinal reinforcement is at least 12 mm. Their ends can not be terminated by hooks. They are fully embedded in the bonding pad under the general rules;
—
the diameter of the transverse reinforcement is at least 5 mm. Their current spacing does not exceed 20 cm;
—
at each end, this space is divided at least by two on a length equal to two times the smallest transverse dimension of the pile. When the severity of the implementation, including threshing, motivates, this spacing is divided by three lengthwise above. In addition, a transition zone of the same length comprises a transverse reinforcement spacing equal to 2/3 of the current spacing;
—
in the piles of square section with intermediate longitudinal reinforcement, they are maintained by additional frames or pins.
NOTE 1 - It should also refer to the NF EN 12794 + A1 which deals with prefabricated concrete piles. (2)
In the case where the suspension devices of the piles in the cargo gear may weaken the strength of the stake, it must be taken into account in the calculations.
Q.3.3 tubular piles prestressed concrete Reinforcing steel Q.3.3.1 (1) The head and the base of the pile should include hooping reinforcement to ensure the integrity of the concrete under the effect of actions localized preload and implementation.
Q.3.3.2 Prestressing (1)
Except different requirements, these frames are used in accordance with applicable rules of prestressed concrete limit state.
(2)
During the implementation of the pile, these frames should ensure the concrete medium compression greater than or equal to 5 MPa (Note 1).
NOTE 1 - This minimal compression is intended to compensate the tensile stresses due to the reflection of the shock waves that appear during the implementation of the pile.
Q.3.4 Pious run up and barrettes (1) The following provisions supplement those of the standard EN 1536 on bored piles and those of the NF EN 12699 concerning discharge to ground stakes.
NF P 94-262
Q.3.4.1 geometric Provisions Q.3.4.1.1 Dimensions (1) For road bridges, the smallest transverse dimension of the piles must be greater than or equal to 0.6 m. It must be greater or equal to 0.8 m for circular piles arranged in a single file.
Q.3.4.1.2 Tilt (1) For bridges, unless otherwise specified, only may be i nclined stakes whose performance is completely driving away of a worki ng tube, recovered or not.
Q.3.4.1.3 Distance between axes (1) Unless otherwise specified, the distance of bare bare between two adjacent foundation members is greater than or equal to 0.75 times the sum of their diameters in the case of circular piles and 0.75 times the sum of their widths when it comes to bars (Note 1). NOTE 1 - This requirement is intended to prevent the disorders that the implementation of a pile may cause the pious neighbors, especially in the common case where the constituent concrete is very young, even below the setting phenomenon.
Q.3.4.2 armatures
Q.3.4.2.1 Constitution and dimensions of reinforcement cages (1)
The reinforcement cages circular section piles are constituted by steel longitudinal reinforcement arranged along the generatrices of a cylinder around which are wound
and fixed rigidly hoops or helices. 38 (3) The outer diameter (or width) of the reinforcement cage is: —
at most equal to the inner diameter of the tube decreased by 8 cm for shelled and beaten molded driven piles;
—
at most equal to the inner diameter of the temporary casing decreased by 10 cm for cased bored piles;
—
at least equal to 1.25 times the inner diameter of the eventual concrete column.
(4)
One can replace the reinforcement cage by a profile or a tube. If the profile or the tube is inside the concrete, it is necessary to meet the requirements of DIN EN 1992-1-1
clause 9.1 (3) and the National Annex to Standard EN 1992-2 clause 9.1 ( 103) (Note 1). In addition, it is necessary to ensure the composite behavior of the concrete steel interface and particularly non slip, if necessary by using for example connectors. NOTE 1 - It should set up a table of minimum reinforcement in concrete according to environmental class. For example, XC class must be placed 3 cm 2 per meter of wall (in class XD and XS at l east 5 cm2) perpendicular to the direction of reinforcement but not less than 0.1% of the section of the wall.
Q.3.4.2.2 longitudinal Armatures (1)
The minimum number of longitudinal bars is 6 and their diameter is not less than 12 mm;
(2)
In general, the spacing of the longitudinal bars can be less than 10 cm between bare and can not be greater than 20 cm. Except where otherwise provided, this distance
must be maintained between the bare bars couples the right recoveries; (3)
The minimum section of longitudinal reinforcement Asbpmin is given by 9.6N table section
9.8.5 of the NF EN 1992-1-1 (Table Q.3.4.2.2).
38
For piles of non-circular section and in particular the webs, the transverse reinforcement are composed of frames, pins and brackets.
NF P 94-262
Table Q.3.4.2.2 - minimum area of reinforcement cross-section of the pile Ac
minimum area of longitudinal reinforcement As, bpmin
Ac <0.5 m2
As> 0.005. ac
0.5 m2
As> 0.0025 m2
Ac> 1.0 m2
As> 0.0025. ac
Transverse reinforcement Q.3.4.2.3 (1)
The spacing of the crossbars is at most equal to 15 times the smallest diameter of the longitudinal rods, with a maximum of 35 cm.
(2)
Their diameter is at least equal to four tenths of the largest diameter of the longitudinal rods, with a minimum of 6 mm. It is recommended that the values given in Table
Q.3.4.2.3. (3) (4)
In the case of non-circular piles, and in particular webs, are arranged to prevent movement of the longitudinal bars to the nearest wall. However, it is recognized that some longitudinal bars are only partially retained in order to allow the passage of the column or columns of concrete. Table Q.3.4.2.3 - Diameters recommended for transverse reinforcement (in millimeters) 12-14 25 32 ^ Longitudinal reinforcement ^ Transverse reinforcement
6- 8
16
20
8-10
10-14
10-16
10-16
Q.3.4.2.4 Stiffness (1)
In addition to the justifications for the strength of the finished pile, the design of the reinforcement cage and, in particular, the choice of the diameters of irons, should ensure
a sufficient rigidity to limit deformation during handling, as well as any risk of buckling during concreting. (2)
In the case of bars or piles of large diameter, this rigidity must be improved by adding slashes arranged and fixed so as to gain effective bracing of the cage.
Q.3.4.2.5 Coating
(1) The thickness of the concrete which coats the armatures is at least equal to (Note 1):
—
7 cm for piles, piles or parts of webs in the general case;
—
4 cm for piles or stakes parts comprising a permanent casing or a liner, this coating being counted from the inner surface of the casing or sleeve.
NOTE 1 - It will be noted that the provisions of Article Q.3.4.2.1 on the outer diameter (or width) of the cage reinforcement in the event of use of a temporary casing set in fact a minimum cover for elements of foundations concerned. Q.3.4.2.6 reservations Tubes (1) auscultation tubes (Note 1), injection, etc., are placed so as not to interfere with the proper coating reinforcements (Note 2). NOTE 1 - This is usually 50/60 tubes for sonic auscultation through. The distance between tubes must be adapted to the sensitivity of the method. NOTE 2 - W hatever their destination, the tubes must be rigid, waterproof, and protected during the work against any damage that may affect their use. Cutting back Q.3.4.2.7 (1) Concrete dimension is set so that the sound concrete is reached the theoretical cut-off level (Notes 1 and 2).
NF P 94-262
NOTE 1 - can be described by the following formula: 0.3 * (1 + z) limited to 1.8 m where z represents the theoretical cut-off level. NOTE 2 - However, this value may be reduced subject to guarantee the result. It can also be increased when there is risk of stricture of the concrete before it hardens.
Appendix R (Informative) Consideration of geometric imperfections related tolerances execution
A.1 Preamble (1)
Geometric tolerances of eccentricity and tilt head are indicated by the performance standards.
(2)
The work of a design project may provide different tolerances than those indicated by the standards.
(3)
The tolerances must be taken into account in the design and rationale, knowing that, without exception, can not wait for the deep foundations are conducted to measure
actual geometrical defects and design the superstructure by taking them into account. (4)
The gap on tilt usually induced on piles isolated parasitic forces of much less importance than those resulting from defects in centering head.
(5)
Parasites efforts are not to be considered as part vis-à-vis the ELU justifications; they can be balanced by:
—
deep foundations;
—
trimmers and Stringers installed between deep foundations;
—
poles and walls;
—
an allocation between these elements.
(6)
In some cases, the distribution of the bending forces must take into account the rigidities, such as the deep foundation supports a slender pole that must justify the form
stability or in some cases micropiles. In most cases, can be divided to balance the moments ahead of the deep foundation element the arbitrary resistance mobilizations. (7)
Justifications must form a coherent whole and the rules between the parties must be clearly defined in advance, also considering the cases of corrective measures possibly
necessitated by geometrical defects exceeding the agreed tolerances.
A.2 Rules to specify in the project design (1) The work of a design project must specify (Note 1): —
geometric tolerances of centering and slope of deep foundations (if any of misorientation around the vertical axis for non-axisymmetric foundations) when they are different from those provided by the implementing standards;
—
the choice of structural elements mobilized to the justifications of stability and structure's resistance in a context of respect for tolerance; This normally results in providing a charge down at the base of massive piles head for their own justifications, including parasitic loads generated by the geometri cal defects, and characteristics of the pious
considered by the designer; NOTE 1 - geometrical deviations exceeding the tolerances can have modest consequences such as building frames a sill or heavier such as the addition of structural elements. (2)
When one turns to piles of different characteristics from the initial design,
it is necessary to allow it to be consistent with the implemented solution.
(3)
By default, if the design project does not specify:
—
the piles are justified vis-à-vis the load path is provided;
—
lowering loads is deemed to take into account the consequences of geometrical defects piles when they remain within the tolerances of this standard or performance standards;
—
tolerance of execution is equal to 0.15 m at the execution platform and tolerance of inclination is equal to 3% if pile technology is not fixed; otherwise, apply those
NF P 94-262
performance standards; —
the piles are deemed connected by headers, stringers and cross walls it is sufficient to strengthen if the geometrical defects of some piles exceed tolerances.
R.3 special case of isolated piles subjected to a "compression centered" (1)
This case (Note 1) is that of a stake for which the reasons for the scope structure only occupy a centered vertical reaction, and whose head is not connected to the cross
girders. NOTE 1 - Historically, a common practice was to consider that an axial load could be inconsequential eccentric to B / 8 on unarmed vertical piles solicited between 4 and 5 MPa SLE and respecting specific tolerances; justifications required at ULS are more limiting. (2)
Geometrical defects result in parasitic bending forces; the normal force maximum limit Ngrenz bearable by the stake at ULS is calculated taking into account the maximum
parasitic forces (Note 1). NOTE 1 - It is contemplated an area of maximum eccentricity, for example the maximum value between B / 10 and 0.08m; then determined the normal force Ngrenz the ELU bearable by this maximum diameter for eccentricity. All stake with an eccentricity fault below the limit is able to withstand a normal force at ULS at least Ngrenz. (3)
The normal force Ngrenz remains capped at 65% of the allowable normal force for actually centered care.
(4)
It is often desirable to provide a minimum reinforcement at the top of piles unreinforced concrete to deal with possible impacts during the construction phase. This
reinforcement increases the normal force bearable maximum limit by the stake, since the moments generated by the geometrical defects quickly dampen away from the surface. (5)
Tolerances can be considered more restrictive tolerances than those provided by the implementing standards, reasonably chosen based on technology and geotechnical
context.
NF P 94-262
Appendix S (Informative) Items related to compression in static load tests
S.1 (1)
Preamble This Appendix presents some elements for the realization axial static loading test in compression in order to determine the limit bearing and compressive creep load of a
single element of deep foundation (Notes 1 and 2). NOTE 1 - The test of static load is the most reliable way to determine the creep load and resistance limit of a pile. Its use is particularly recommended for large projects or in difficult locations. These tests can also be an opportunity to develop the means of implementation (need for cladding, grooving, threshing opportunities, etc.) or new types of piles. NOTE 2 - More detailed guidance on situations that require the production of pile load tests and their purpose are given in section 7.5.1 of EN 1997-1 standard. (2)
The way the static load tests are performed (loading procedure required number of test piles) must comply with section 7.5.2 of the standard EN 1997-1, supplemented by
the indications of this Annex (Note 1 items and S.2 to S.4). NOTE 1 - Pending the publication of European standards (EN 22477-1 to 4) on the deep foundation load testing, the tests are conducted and interpreted according to the NF P 94-150-1 and 2, NF P 94151 and NF P 94-153.
S.2
Site Recognition
(1) Where a stake test is considered, the general recognition of the site, in addition to its usual characteristics (Annex M.1), shall demonstrate that the selected location is representative of the project site (Note 1) or allow to determine the best possible test site (S.3). NOTE 1 - should be included in the test area to confirm the recognition such as geology of the site is sufficiently homogeneous terms of the layer thickness and mechanical characteristics, or failing to have the data necessary for the interpretation of test results. NOTE 2 - It is appropriate for each test site is subject to specific recognition campaign consisting of a core drilling and pressuremeter profile or penetrometer made within two meters of the axis of the test pile.
S.3
Location of the test
(1) The location of each test, chosen after recognition campaign, must be representative of types of terrain encountered by the pious of the book and their mechanical characteristics (Note 1). NOTE 1 - It should reflect the final configuration in which the foundation work, which can be different from that of the trial in the case of excavations or embankments.
S.4 test piles (1)
The method of execution of test piles must be identical to that of the piles of the book.
(2)
Except for the cases referred to S.4 clause (3), the test piles must be the same size and shape as the stakes of the book.
(3)
For piles of large transverse dimensions, stakes testing may have smaller dimensions (Notes 1 and 2), within the following limits: B
test - 0.5 Bréel Bessai -
0.6 m NOTE 1 - This type of test is particularly suitable: —
where piles of the book are too large to it is conceivable to perform a field test,
—
where the variability of layer thicknesses or the mechanical characteristics of the foundation soil does not test a sufficient number of representative sites.
NOTE 2 - It is necessary to carefully use this approach in the case of open piles because of the influence of the diameter on the mobilization of the bearing capacity of soil plug located inside the pile.
