INTRODUCTION TO RAILWAY ENGINEERING
RAILWAY ENGINEERING
The branch of Civil Engineering which deals with the design, construction and maintenance of the railway tracks for safe and efficient movements of trains is called Railway Engineering. 2
As per scope of this book, we shall study here only about construction and maintenance of railway tracks and not with the design of tracks.
SCOPE OF RAILWAY ENGINEERING A part from design, construction and maintenance of tracks, Railway engineering also includes the study of the following important topics :-
3
Contents • Introduction to railway • Classification of railways (on the basis of gauge) • Components of railway track (rails, sleeper, ballast)
Contents • Geometric design of railway track (cross section, gradient, super elevation) • Maximum permissible speed • Railway points and crossings • Stations and yards • Platforms
• Rail transport is where a train runs along a set of two parallel steel rails, known as a railway or railroad. The rails are anchored perpendicular to ties (or sleepers) of timber, concrete or steel, to maintain a consistent distance apart, or gauge. The rails and perpendicular beams are placed on a foundation made of concrete, or compressed earth and gravel in a bed of ballast.
Components of a railway track (Permanent Way) Rails
Sleepers (Ties)
Ballast
What are the advantages of rail transport? • It facilitate long distance travel and transport of bulky goods which are not easily transported through motor vehicles. • It is a quick and more regular form of transport because it helps in the transportation of goods with speed and certainty. • It helps in the industrialization process of a country by easy transportation of coal and raw-materials at a cheaper rate.
• It encourages mobility of labour ad thereby provides a great scope for employment. • Railway is the safest form of transport. The chances of accidents and breakdown of railways are minimum as compared to other modes of transport. • The carrying capacity of the railways is extremely large. • It is the largest public undertaking in the country. Their charges are based on charge what the traffic can bear principles which helps the poor. In fact, it is a national necessity.
Disadvantages • The railway requires a large investment of capital. • Another disadvantages of railway transport is its inflexibility. It routes and timings cannot be adjusted to individual requirements. • Rail transport cannot provide door to door service as it is tied to a particular track. Intermediate loading or unloading involves greater cost, more wear and tear and wastage of time. The time cost of terminal operations are a great disadvantage of rail transport.
• Railway transport is unsuitable and uneconomical for short distances and small traffic of goods.
.
SYSTEMS OF RAILWAYS
The Railways can be provided on, above the below the ground surface, suiting to the area. Further, the Railways below the ground surface can be constructed just below the ground surface can be constructed just below the ground level or at greater depths.
14
There are, therefore, the following four systems of Railways :1. Surface railways; 2. Elevated railways; 3. Under ground railways; 4. Tube railways.
1) Surface railways :-The railways provided over the ground surface are known as surface railways. Suitability :-This system is Railways is most extensively used throughout the world
15
because this is the best system for transporting people and goods. In surface railways, the various means like*level crossings,**over-bridge or***under-bridge are to be provided for crossing of the railway and road traffic safely and efficiently. 2) Elevated railways :-The railways provided at higher or elevated portion, above the ground surface are called “high level” or “elevated railways”. In this system of Railways, a
16
continuous viaduct supported on piers, columns, etc. is constructed and the track is carried on its steel deck. This system is very costly because buildings like stations, waiting halls, offices are to be constructed at high levels requiring stair cases, escalators, etc. but elevated railways cause little obstruction due to piers, columns supporting the track. Suitability :- Elevated railways are suitable in the heavily congested urban areas where the under ground railways cannot be
17
constructed. 3) Under ground railways :- The railways provided just below ground level are called “low level or underground railways”. In this system of Railways, tunnels are constructed for carrying tracks through them and a over - bridge is necessary at every road crossing to carry the road traffic over the railway traffic. Due to ventilation problems in tunnels, electricity is the only source of power for traction in under ground railways.
18
Advantages :i. This system provides rapid and unobstructed transportation. ii. This system helps in reducing traffic congestion problems. iii. This system provides safety during aerial attack in war. Suitability :- Under ground railways are suitable in the heavily congested urban areas where the traffic intensity on roads is heavy.
19
Tube railways :- The railway provided underground at a greater depth of about 18 m or more (up to 52 m) are called tube railways. This system of railways is so called as the section of the underground tunnels, carrying the track, is to avoid the interference of the tracks with water and gas pipes, sewerage systems and oil or drainage pipes, etc Some important features of the tube railways are given below :-
20
i.
The railways stations have to be of cylindrical form. ii. Escalators or moving stair cases are to be constructed to reach the tube railways. iii. Only electric traction to be used to avoid the smoke and ventilation problems. iv. Automatic signaling system is to be used.
21
V. Such a mechanism of the train is to be used that it cannot start until all the doors are closed, and it automatically stops, if the signal is at ‘STOP’ position. This system of railways is used by the London Post Office in transporting mails through a small diameter tunnel with automatic control without any driver.
22
REQUIREMENTS OF A GOOD TRACK • Gauge should be correct and uniform • Alignment of track should be correct • Transition curves should provided wherever required • Perfect cross levels between rails • Gradient should be as gentle as possible • Points and crossings (turnouts) should be designed and maintained properly
List of countries by rail transport network size Rank
Country
Railway length (km)
Date of information
1
United States
226,427
(2007)
2
Russia
128,000
(2006)
3
China
91,000
(2010)
4
India
64,215
(2011)
5
Canada
57,216
(2007)
137
Nepal
59
(2006)
138
United Arab Emirates
52
(2009)
147
Western Sahara
5
(2008)
148
Laos
4
(2005)
149
Lesotho
3
(1995)
150
Monaco
2
(2002)
151
Vatican City
0.852
(2001)
1,370,782
(2006)
World
COMPONENT PARTS OF A PERMANENT WAY :The following are the component parts of a permanent way or a railway track :• Formation or sub grade ; • Ballast ; • Sleepers ; • Rails ; • Fixtures and fastenings. All these component parts of a permanent way are illustrated in Fig given below :25
26
REQUIREMENTS OF AN IDEAL PERMANENT WAY The following are the principal requirements of an ideal permanent way or of a good railway track :i. The gauge of the permanent way should be uniform, correct and it should not get altered. ii. Both the rails should be at the same level on tangent (straight) portion of the track. iii. Proper amount of *superelevation should 27
be provided to the outer rail above the inner rail on curved portion of the track. iv. The permanent way should be sufficiently strong against lateral forces. v. The curves, provided in the track, should be properly designed. vi. An even and uniform gradient should be provided through out the length of the track. vii. The **tractive resistance of the track should be minimum. viii. The design of the permanent way should be such that the load of the train is 28
uniformly distributed on both the rails so as to prevent unequal settlement of the track. ix. It Should provide adequate elasticity in order to prevent the harshness of impacts between the rails and the moving wheel loads of a train. x. It should be free from excessive rail joints and all the joining should be properly designed and constructed. xi. All the components parts such as rails, sleepers, ballast, fixtures and
29
fastenings, etc. should satisfy the design requirements. xii. All the fixtures and fastenings such as chairs, bearing plates, fish plates, fish bolts, spikes etc. should be strong enough to withstand the stresses occurring in the track. xiii. All the *points and crossings, laid in the permanent way, should be properly designed and carefully constructed. xiv. It should be provided with fence near 30
level crossings and also in urban areas. xv. It should be provided with proper drainage facilities so as to drain off the rain water quickly away from the track. xvi. It should be provided with safe and strong bridges coming in the alignment of the track. xvii.It should be provided with safe and strong bridges coming in the alignment of the track. xviii.It should be so constructed that 31
Elements of Railway tracks • The track on a railway or railroad, also known as the permanent way, is the structure consisting of the rails, fasteners, sleepers and ballast (or slab track), plus the underlying sub grade. • For clarity it is often referred to as railway track or railroad track.
33
Track Formation The purpose of track is to transfer train loads to the formation. Requirements for Choosing a Track System: Trains running on Track do not cause excessive environmental pollution in the form of noise and ground vibration. 1. Costs of the total service life of the track must be as low as possible. 2. Maintenance should be low and as inexpensive as possible
Running Rails
Track gauge (Rail gauge) • The distance between the inner sides of the heads of the two load bearing rails that make up a single railway line.
Various gauges used worldwide
Various gauges used worldwide Gauge
Width (mm)
Used in
Standard Gauge
1435
England, USA, Canada, China, Australia
Broad Gauge (BG)
1676 1670
India, Brazil, Argentina Spain, Portugal
Broad Gauge (Russian Gauge)
1524
Russia, Finland
Cape Gauge
1067
Japan, Newzealand
Meter Gauge (MG)
1000 915
India, France Ireland
Narrow Gauge
672 610
India, Pakistan S. Africa
TYPES OF GAUGES PREVALENT IN INDIA The different gauges prevalent in India are of the following these types :1. Broad gauge (1676), 2. Metre gauge (1000), 3. Narrow gauge (762 mm & 610 mm).
40
1. Broad Gauge :- When the clear horizontal distance between the inner faces of two parallel rails forming a track is 1676mm the gauge is called Broad Gauge (B.G) This gauge is also known as standard gauge of India and is the broadest gauge of the world. The Other countries using the Broad Gauge are Pakistan, Bangladesh, SriLanka, Brazil, Argentine,etc.50% India’s railway tracks have been laid to this gauge. 41
Suitability :- Broad gauge is suitable under the following Conditions :(i) When sufficient funds are available for the railway project. (ii) When the prospects of revenue are very bright. This gauge is, therefore, used for tracks in plain areas which are densely populated i.e. for routes of maximum traffic, intensities and at places which are centers of industry and commerce. 2. Metre Gauge :- When the clear horizontal distance between the inner faces of two
42
parallel rails forming a track is 1000mm, the gauge is known as Metre Gauge (M.G) The other countries using Metre gauge are France, Switzerland, Argentine, etc. 40% of India’s railway tracks have been laid to this gauge. Suitability :- Metre Gauge is suitable under the following conditions:(i) When the funds available for the railway project are inadequate. (ii) When the prospects of revenue are not very bright. This gauge is, therefore, used for tracks in underdeveloped areas and in interior areas
43
Where traffic intensity is small and prospects for future development are not very bright. 3.Narrow Gauge :- When the clear horizontal distance between the inner faces of two parallel rails forming a track is either 762mm or 610mm, the gauge is known as Narrow gauge (N.G) The other countries using narrow gauge are Britain, South Africa, etc. 10% of India’s railway tracks have been laid to this gauge. Suitability :- Narrow gauge is suitable under the following conditions :44
( i) When the construction of a track with wider gauge is prohibited due to the provision of sharp curves, steep gradients, narrow bridges and tunnels etc. (ii) When the prospects of revenue are not very bright. This gauge is, therefore, used in hilly and very thinly populated areas. The feeder gauge is commonly used for feeding raw materials to big government manufacturing concerns as well as to private factories such as steel plants, oil refineries, sugar factories, etc. 45
Factors Affecting the Adoption of a Particular Gauge The following are the factors which affect the adoption of a particular gauge for the track :I. Intensity of Population. II. Intensity of Traffic. III. Industrial and Commercial development of the Locality. IV. Prospects of future development of the area. 46
V. Funds available for th railway project. VI. Topographical and Geological Features of the country.
Effects of Breaking the Gauge One country should have only one gauge throughout its various parts. But the policy of India and its Topographical, Geological and Financial conditions have led to adopt various gauges in its different parts. The various effects of breaking or change of gauge are discussed below :-
47
1. Advantages of Breaking the Gauge :i). The most effective advantage of breaking the gauge is to render the railway an economical and profitable concern. ii). It facilitates the provision of a steeper gradient, sharp curves and narrow tunnels by adopting a less wide gauge in hilly and rocky areas. 2. Disadvantages of Breaking the Gauge :i). It causes much inconvenience to the passengers while changing the train at station, with change of gauge. 48
ii). It causes delay in movement of people and goods. iii). It results in wastage of time. iv). It involves extra labour for unloading and reloading the goods. The goods are also likely to be damaged or dislocated at the junction station, having change of gauge. v). It requires the provision of extra and costly transshipment yards, godowns, sheds, etc. at every junction station having change of gauge. vi). It causes extreme difficulty in quick movement of military and ammunition during war days. 49
Which gauge is the best? • Historically….. the choice of gauge was partly arbitrary and partly a response to local conditions • Narrow-gauges - cheaper to build and can negotiate sharper curves • Broad-gauges - give greater stability and permit higher speeds.
Coning of Wheels Coning of wheels is a method of beveling the wheels to avoid depreciation to the wheels and rims. Normally the wheels are conned by a cone of semi-angle. It is based on the theorem of coning. • Introduction Railway wheels are usually beveled by means of a cone semi-angle of the arrangement of 1/20 (rad.). The rails are also fixed at this identical angle to the perpendicular. The width of the wheel is generally 140 mm and the rail top is approximately 80 mm. The proportions of the region of liaison between an encumbered wheel and rail reckon on the exact shapes of the wheel pace and rail head. It also depends on the extent of the load occupied.
51
Coning of Wheels • The space between the inner borders of wheel rims is by and large kept less than the measurement of the track. This results in a gap between the wheel rims and running ends of the rails which is approximately equal to 1 cm, (3/8) on both side. More often than not, the tread of wheels is perfectly the dead centre of the beginning of the rail, since the wheel is chamfered to keep it in this middle position involuntarily. Thus the wheels are beveled at an inclination of 1 in 20. • Advantages of coning the wheels • (i) Coning the wheels reduces the depreciation of the wheel rims and rails. Depreciation is caused because of the friction action of rims with inner faces of the rail top. • (ii) Coning also gives an option of lateral drift of the hinge with is wheels. • (iii) Coning also prevents, to some extent, the slipping of the wheels. 54
Theory of Coning •
On a railway level track, the moment the hinge loco motes towards one rail, the wheel tread width above the rail steps-up but reduces over the other rail. This forbids the auxiliary movement and hinge pulls back to its original position. This is possible only if the diameters on both rails are equal and the pressure on both the rails is also equal. • On a coiled path, because of rigidity of the wheel bottom either of the wheels has to slip by a measure equal to the differentiation of length or else the axle has to move outward a bit so that a tread with longer diameter is formed over the outer rail whereas a slighter diameter tread is formed over the inner rail.
55
FISH PLATE AND FISH BOLTS
BEARING PLATE (BENEATH THE SLEEPER)
HIGH SPEED RAILS • Passenger rail transport that operates significantly faster than the normal speed of rail traffic. • The U.S. Department of Transportation's reasonably expected to reach sustained speeds of more than 125 mph (201 km/h)
WORLD RECORD • The world record for conventional high-speed rail is held by the V150 of France, a specially configured and heavily modified train which clocked 574.8 km/h (357.2 mph) on a test run. • Aerodynamic designs (to reduce drag, lift, and noise), air brakes, regenerative braking, stronger engines, dynamic weight shifting, etc • High Speed train in France (> 574 Kmph)
RAILWAY POINTS AND CROSSINGS
POINTS AND CROSSINGS • To divert trains from one track to another, a special arrangement is made….so that …the inside flange of the wheel can move on the diverted track.
• Such arrangement is called “POINTS AND CROSSINGS”
A Right Hand Diversion
• Points + crossings = TURNOUT
POINTS AND SWITCHES • A railroad switch or points is a mechanical installation enabling railway trains to be guided from one track to another at a railway junction.
POINTS AND SWITCHES
Electric, Hydraulic or Manual
CROSSINGS • It is a special form of construction to provide flange way clearance between two rails to be crossed. • To achieve this, a gap is provided from throat to nose of crossing over which the wheel jumps.
Throat
Components of CROSSING of a Right Hand Turnout
CROSSINGS • To ensure that the wheel negotiates the gap properly and doesn’t strike the nose, the outer rail is guided with the help of CHECK RAILS.
Characteristics of a good crossing: • Should be rigid • Frog and wing rails should be protected against damage so that the wheels do not bump into the gap. • Frog should be of sufficient thickness.
Types of crossings • Acute angle (V-Crossing) • Obtuse angle crossing • Square Crossing
CAPACITY OF RAILWAY TRACK • Maximum number of trains that can run safely on any length of track per hour.
• Maximum number of trains that can be handled in a yard …TERMINAL CAPACITY.
Specification of Indian Railways 1. Sleeper density = no. of sleepers per rail length. Generally, 1 sleeper in every meter length. Depends on: axle load, speed, strength of sleeper, depth of ballast. Sleeper density = n+ x (x = 7 usually) n = length of each rail 2. Rails: 13 m long (for BG track)
• Example: If sleeper density is n + 6 for a BG track, calculate the number of sleepers in 960 m length of railway. Length of each rail = 13 m Total no. of rails in 960 m = 960/13 = 74 No. of sleeper in each rail = 13 + 6 = 19 So, no. of sleeper in 74 rails = 74 x 19 = 1406
3. Materials required per KM length of track 1. No. of rails per km = (1000/13) x 2 = 154 2. Weight of rail per km = (154 x 13) x 60 = 120,120 kg (@ 60 kg/m) 3. No. of sleepers per km = (154/2) x (13 + 7) = 1540 4. No. of fish plates per km = 77 x 2 = 154 5. No. of bolts per km = 154 x 4 = 606 6. No. of bearing plates per km = 1540 x 2 = 3080 7. No. of fasteners = (1540 x 12) 8. Quantity of ballast per km = (0.2 x 3.35 x 1000) cubic meter
