March 2005
Process Industry Practices Structural
PIP STE02465 Augered Cast-in-Place Piles Design Guidelines
PURPOSE AND USE OF PROCESS INDUSTRY PRACTICES In an effort to minimize the cost of process industry facilities, this Practice has been prepared from the technical requirements in the existing standards of major industrial users, contractors, or standards organizations. By harmonizing these technical requirements into a single set of Practices, administrative, application, and engineering costs to both the purchaser and the manufacturer should be reduced. While this Practice is expected to incorporate the majority of requirements of most users, individual applications may involve requirements that will be appended to and take precedence over this Practice. Determinations concerning fitness for purpose and particular matters or application of the Practice to particular project or engineering situations should not be made solely on information contained in these materials. The use of trade names from time to time should not be viewed as an expression of preference but rather recognized as normal usage in the trade. Other brands having the same specifications are equally correct and may be substituted for those named. All Practices or guidelines are intended to be consistent with applicable laws and regulations including OSHA requirements. To the extent these Practices or guidelines should conflict with OSHA or other applicable laws or regulations, such laws or regulations must be followed. Consult an appropriate professional before applying or acting on any material contained in or suggested by the Practice.
This Practice is subject to revision at any time by the responsible Function Team and will be reviewed every 5 years. This Practice will be revised, reaffirmed, or withdrawn. Information on whether this Practice has been revised may be found at www.pip.org.
© Process Industry Practices (PIP), Construction Industry Institute, The University of Texas at Austin, 3925 West Braker Lane (R4500), Austin, Texas 78759. PIP member companies and subscribers may copy this Practice for their internal use. Changes, overlays, addenda, or modifications of any kind are not permitted within any PIP Practice without the express written authorization of PIP.
PIP will not consider requests for interpretations (inquiries) for this Practice.
Not printed with State funds
March 2005
Process Industry Practices Structural
PIP STE02465 Augered Cast-in-Place Piles Design Guidelines Table of Contents 1. Introduction .................................. 2
13. Basis of Payment ....................... 6
1.1 Purpose ............................................. 2 1.2 Scope................................................. 2
14. Surveying .................................... 7
2. References.................................... 2
15. Underground Utility Location.... 7
2.1 Process Industry Practices ................ 2 2.2 Other References .............................. 2
16. Construction Permits................. 7
3. Definitions .................................... 2
17. Test Piles .................................... 7
4. General ......................................... 3 5. Preaward Meeting ........................ 3 6. Inspection..................................... 4 7. Spoils Handling............................ 4 8. Grout ............................................. 4 9. Codes............................................ 5 10. Pile Integrity Testing .................. 5 11. Reinforcement ............................ 6 12. Obstructions and Payment for Piles ............................................. 6
Process Industry Practices
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PIP STE02465 Augered Cast-in-Place Piles Design Guidelines
1.
March 2005
Introduction 1.1
Purpose This Practice provides recommendations for the design and installation of augered cast-in-place piles for use by the engineers and specifiers of augered cast-in-place piles.
1.2
Scope This Practice supplements PIP STS02465 and provides assistance to the engineer in the preparation of contract documents for furnishing and installing augered cast-inplace piles. This Practice is modeled on the DFI Augered Cast-in-Place Piles Manual. For additional information, refer to that manual and also to the DFI Inspector’s Guide to Augered Cast-in-Place Piles. This Practice does not describe requirements for lateral displacement or drilled displacement piles, also known as augered cast-in-place displacement (ACIP-D) piles. ACIP-D piles may be a good substitute for augered cast-in-place piles in some soil types/conditions. Because of reduced or eliminated spoils, ACIP-D piles may be a good choice in contaminated soil conditions. However, the different types of proprietary ACIP-D piles may be more or less suited for different soil conditions. Appropriate engineering, including geotechnical engineering, is required. DFI is developing a practice manual on ACIP-D piles, and the Federal Highway Administration is developing a manual on augered cast-in-place piles that addresses ACIP-D piles. Both manuals are due out in 2005.
2.
References Applicable parts of the following PIP Practice and other references should be reviewed by those preparing contract documents for augered cast-in-place piles. 2.1
Process Industry Practices (PIP) – PIP STS02465 - Augered Cast-in-Place Pile Installation Specification
2.2
Other References • Deep Foundations Institute (DFI) – Augered Cast-in-Place Piles Manual – Inspector’s Guide to Augered Cast-in-Place Piles • American Society of Civil Engineers (ASCE) – ASCE 7-2002 - Minimum Design Loads for Buildings and Other Structures
3.
Definitions engineer of record: The engineer responsible for structural design of the project
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Process Industry Practices
PIP STE02465 Augered Cast-in-Place Piles Design Guidelines
March 2005
geotechnical engineer: The party responsible for performing the geotechnical investigation and/or geotechnical consulting during the piling work inspector: The party responsible for performing inspection during the pile work owner: The party who owns the facility wherein the augered cast-in-place piles will be installed purchaser: The party who awards the contract to the supplier. The purchaser may be the owner or the owner’s authorized agent. supplier: The party responsible for furnishing and installing augered cast-in-place piles
4.
5.
General 4.1
The recommendations given in this Practice should be considered in design and construction of augered cast-in-place pile foundation systems.
4.2
These recommendations are provided because of the unique features of the system and should be considered because they improve the final product and reduce problems during construction. These recommendations are not all inclusive, and the specifications and plans should be reviewed by a geotechnical professional experienced in augered cast-in-place pile design and construction.
Preaward Meeting A preaward or preconstruction meeting, including at a minimum the supplier, purchaser, engineer of record, geotechnical engineer, and inspector, should be held to discuss topics such as the following. a.
Safety requirements
b.
Site entry procedures
c.
Available subsurface information
d.
Underground utility identification and location
e.
Survey for elevation and location of piles
f.
Reinforcing steel placement
g.
Grout
h.
Excavated materials disposal
i.
Action required if potentially contaminated soil is encountered
j.
Testing and inspection
k.
Responsibility for required reports
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PIP STE02465 Augered Cast-in-Place Piles Design Guidelines
6.
7.
8.
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Inspection 6.1
The inspection data requirements for augered cast-in-place piles during installation differ from the data typically obtained for driven piles.
6.2
During pile installation, problems that are difficult to detect can occur, which can reduce the load carrying capacity of the pile. For these reasons, careful, purchaserretained inspection by an experienced professional (preferably a geotechnical engineer) on a full-time basis is considered essential.
6.3
Careful attention should be given to the inspection requirements by an experienced professional. Modifications should be made to the inspection requirements to fit the specific requirements of each project.
6.4
For the inspection, automated instrumentation and monitoring systems to measure various elements of the installation process and to produce readout by computer are available. If this type of instrumentation is desired and is to be provided by the supplier, the requirements should be stated by adding an addenda coversheet to invoke and modify PIP STS02465, Section 4.2.3. The instrumentation will be an additional cost to the purchaser. Even if the instrumentation is provided by the supplier, a qualified inspector should be present during the pile work. The special instrumentation is not normally used or available for piles installed in areas having restricted headroom conditions.
Spoils Handling 7.1
The drilling process produces spoils in the form of excess grout and soil returned to the surface by the augers.
7.2
The contract documents should clearly state which party is responsible for removing and disposing spoils, any restrictions on the disposal, and location of a disposal area that the owner can provide, if any.
7.3
If the soil is contaminated, handling and disposal costs should be considered in determining the feasibility of the system.
7.4
If contaminated spoil disposal is an issue, but drilled piles are preferred over driven piles, augered cast-in-place displacement (ACIP-D) piles may be considered (see Section 2, this Practice). All types of ACIP-D piles do not necessarily eliminate spoils, but they at least significantly reduce the quantity of spoils.
Grout 8.1
The required grout strength should be designated on the plans if other than the 4,000 psi (27,580 kPa) at 28 days “default” given in PIP STS02465, Section 4.3.2.7.3.
8.2
Allowable maximum grout temperature and holding time stated in PIP STS02465, Section 4.3.2.7.5, differ from the temperatures and holding times given in the DFI Augered Cast-in-Place Piles Manual guideline specification. However, as also noted in the DFI Augered Cast-in-Place Piles Manual commentary, opinions differ about the allowable maximum temperature, and some think that 90°F (32°C) should be the
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Process Industry Practices
PIP STE02465 Augered Cast-in-Place Piles Design Guidelines
March 2005
maximum (same as given in PIP STS02465). The DFI Augered Cast-in-Place Piles Manual also notes that excessive mixing time and temperature can be detrimental to grout strength.
9.
10.
8.3
As stated in Section 8.2 (this Practice), the requirements in PIP STS02465 are based on 90°F (32°C) allowable maximum temperature. As a result, if a higher and potentially detrimental grout temperature is considered on a particular project or is requested by the supplier, the engineer of record is alerted and given the opportunity to consider whether to allow higher temperatures. If greater temperatures and/or extended holding times are allowed, special procedures for grouting should be developed and followed. It is recommended that additional strength test cubes that represent grout placed at high temperatures and/or after extended holding times be made. To prepare for an occurrence of low strength test results, definitions of remedial actions and assignment of responsibility for the actions should be made and agreed upon beforehand.
8.4
The minimum theoretical grout volume specified in PIP STS02465, Section 4.4.6.13, should be increased as necessary to match the volume used in the test piles and/or the recommendations of the geotechnical engineer, which are made according to soil type encountered during soil borings.
Codes 9.1
Governing codes should be checked for limitations that are more restrictive than those in PIP STS02465. Some building codes place specific limits on design stresses (and/or maximum loads) for this type of pile.
9.2
Codes should be checked for other limitations, such as spacing between piles constructed within 24 hours of one another, reinforcing cover, length to diameter ratio, etc.
Pile Integrity Testing 10.1
Low-strain integrity testing is a relatively quick and inexpensive method of nondestructive assessment of pile cross-sectional integrity, though subject to limitations. If questions arise about the acceptability of piles, such testing may be a useful tool for the engineer to help assess possible problems.
10.2
In some cases, it may be appropriate to perform low-strain integrity testing on a predetermined portion of the completed piles. The engineer should determine the number of piles to be tested. Low-strain integrity testing should be limited to piles with length-to-diameter ratios of less than 30. The use of low-strain integrity testing can cause coordination problems and increase job costs even if the piles are determined to be acceptable. This is especially true if the tests are not completed at the same time that the pile installation is completed.
10.3
Cross-hole sonic logging has been used to evaluate integrity of larger (diameters greater than 24 inches (600 mm) piles. Single-hole sonic logging can be used for piles with diameters of 24 inches (600 mm) or less. The viability of this system must be carefully assessed for usefulness on a particular project.
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PIP STE02465 Augered Cast-in-Place Piles Design Guidelines
11.
12.
13.
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10.4
Specifications should cover acceptance requirements if integrity problems are indicated by these methods.
10.5
Pile integrity testing does not reduce the need for qualified, full-time pile installation inspection. A qualified inspector should be present during the pile work regardless of whether pile integrity testing is performed.
Reinforcement 11.1
Reinforcement cages, if required, should be limited in length to the minimum actually needed for moment and shear resistance.
11.2
Cages longer than about 20 to 25 ft (6 to 8 m) are difficult or impossible to install. If possible, cages should be limited to approximately 15-ft (4.5-m) length. Installation of cages longer than 25 ft (8 m) is normally unsuccessful.
11.3
Full-length single bar reinforcement is commonly employed for tension piles.
11.4
Longitudinal reinforcement and spiral confining steel (or suitable alternative reinforcement) may be needed to withstand seismic pile-soil interaction loading conditions, particularly if these piles derive a significant share of their support in end bearing resistance during and immediately after a major earthquake. Competent geotechnical and structural engineers should confirm the suitability of these foundation elements for the expected loading/distortion conditions.
11.5
According to ASCE 7-2002, Section A9.7.5.4.1, full-length reinforcement cages are required in piles for structures in Seismic Design Category E or F. Accommodations in the design should be made by the engineer of record to facilitate the installation of full-length cages, such as bending reinforcement bars toward the center at the bottom of the cage so that the cage does not catch on the sides of the pile grout hole. In such cases, the supplier should provide a plan to assure that a full-length cage can be installed. In certain soil conditions with deep piles, this requirement may preclude the use of augered cast-in-place piles. A sufficient quantity of grout to complete a pile should be at the site before pile installation begins.
Obstructions and Payment for Piles 12.1
Requirements should be stated for handling piling installation obstructions if encountered.
12.2
Even with a rock bit, augered cast-in-place pile rigs cannot penetrate a significant distance into hard rock, and rock bits may not penetrate many obstructions.
12.3
A payment calculation method for short piles terminated because of obstructions should be stated in the contract documents. Commonly, a pile that cannot be completed to full length because of an obstruction is completed otherwise in accordance with the pile termination requirements, and the supplier is paid for the length installed.
Basis of Payment 13.1
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The basis for payment should be stated in the contract documents.
Process Industry Practices
PIP STE02465 Augered Cast-in-Place Piles Design Guidelines
March 2005
13.2
14.
15.
Typically, the best pricing for the purchaser can be obtained by requesting lump sum bids for the entire installation of the piles and requesting unit pricing for over and under the bid quantity of piles.
Surveying 14.1
The contract documents should clearly state which party is responsible for the survey locating the piles and marking cut-off elevations.
14.2
Location of benchmarks and description of datum plane should be provided, if appropriate.
Underground Utility Location The responsibility for identifying, locating, and marking underground utilities should be clearly defined.
16.
17.
Construction Permits 16.1
Responsibility for permits should be made clear in the contract documents.
16.2
Permits required from regulatory agencies should normally be stated to be the responsibility of the supplier.
16.3
Permits that the supplier shall obtain from the owner/purchaser should be clearly and completely described.
Test Piles 17.1
The contract drawings should show the location, length, number, etc., of probe and/or test piles. See PIP STS02465, Section 4.4.5.1.
17.2
The type of load tests (compression, tension, and lateral) should be designated on the contract drawings. See PIP STS02465, Section 4.4.5.2.
17.3
Details of telltales or strain gauges for test piles should be provided. See PIP STS02465, Section 4.4.5.5.
17.4
The type of test loading procedure should be designated for compression load tests if different from PIP STS02465, Section 4.4.5.12.
17.5
If tension or lateral testing is required, the type of test loading procedure should be designated.
17.6
If dynamic load testing is required, a written procedure for dynamic load testing should be provided.
17.7
If dynamic load testing is required, written assurance should be provided from a professional engineer that the dynamic load testing procedure will yield results that define the allowable load capacities of the piles.
17.8
The viability of dynamic load testing, its applicability to a specific project, the assurance that the testing will not harm the structural integrity of the pile, and the
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PIP STE02465 Augered Cast-in-Place Piles Design Guidelines
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justified degree of confidence to be assigned to the results should be considered in choosing to allow this type of testing and accounted for in selecting the pile design capacities. Further, the applicable building code must be checked to determine whether dynamic testing is allowed.
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Process Industry Practices
