CE 302 Transportation Engineering II

Many slides borrowed from : Dr. Gitakrishnan Ramadurai

Indian Railways The highs!

1831 Idea of a railway line between Madras and Bangalore first conceived

1853 First railway line opened Mumbai to Thane

1891 Toilets introduced in third class coaches!

1925 First electric section Bombay to Kurla

1930 Indian Railways stretches to 66,300 km

1936 First A/C coaches

1984 First metro rail in Kolkata

1995 Ticketing system completely computerized

2002 150 yrs of Indian Railways

2nd largest state owned railway system in the world (after Russian railway)

Classification of Indian railway lines

Based on merely speed criteria

Group A lines Group B lines Group C lines Group D lines Group E lines

Groups

Group A lines - Consists of those routes on which the trains are running or are meant for running at a speed of 160 kmph or more.

Groups B - They consist of those routes on which the trains with a max. sanctioned speed of 130 kmph

Group C lines

They consist of all suburban routes

Group D lines All other routes in the country whether B.G. or

M.G. where max. permissible speed is 100 kmph

Group E lines The other routes and branch lines where the

max. permissible speed is less than 100 kmph

Components

Track or permanent way railroad on which trains run

Locomotive steam, diesel and electric

Traction steam, diesel and electric

Track or Permanent Way

For comfortable and safe ride at the maximum permissible speed with minimum maintenance cost.

The combination of rails, fitted on sleepers and resting on ballast and subgrade (formation) is called the railway track or permanent way.

Track Structure

http://en.wikipedia.org/wiki/File:Section_through_railway_track_and_foundation.png

Consist of 2 parallel rails fastened to sleeper with a specified distance between them

Rails act as girders to transmit the wheel load to the sleepers.

The sleepers are embedded in a layer of ballast and hold the rails in the proper position and transmit the load from rails to the ballast.

The ballast distributes the load over the formation and holds the sleepers in position.

Formation takes the load of the track and train

Track modulus

Index of measurement of resistance to deformation

Defined as the load in kg/unit rail length required to produce 1 unit depression in the rail bottom (kg/cm^2)

Vary with guage, type of rail, sleeper density, ballast cushion

Rails

Functions Provide continuous and level surface for the

movement of trains

Provide a pathway which is smooth

Serve as lateral guide for the wheels

Bear the stresses developed due to vertical load

Rails - Historical Evolution

1. Double-headed rail: Symmetric head and foot so that it could be turned

and reused after a while

2. Bull-headed rail: Larger head to account for more wear and tear.

3. Flat-footed rail:

Flat foot more stability Can be easily fastened using clips (older rails needed

chairs which contributed to wear)

Standard IR sections

IR uses 60kg/m and 52kg/m flat footed sections for modern BG track

Track Alignment

The direction and position given to the centre line of the railway track on the ground is called the railway alignment.

Horizontal alignment includes straight path, its width, deviations in width and curves.

Vertical alignment includes changes in gradients and vertical curves.

Gauge

Minimum distance between two rails measured as the clear distance between the running faces of two rails

Wider gauges can carry larger wagons and coaches and hence more traffic

Type of Gauge system in India Type of gauge Gauge width

Standard gauge (B.G.)

1.676 m.

Metre gauge (M.G.) 1.0 m.

Narrow gauge (N.G.) 0.762 m.

Feeder track gauge or light gauge (L.G.)

0.610 m.

Choice of gauge

Cost of land acquisition, earthwork, sleepers, ballast etc. proportional to size of gauge

Cost of rails, bridges, tunnels, stations, signals etc. almost same for all gauges

Wider gauges can accommodate larger wagons/coaches, and higher speeds hence more traffic.

All new projects in IR since 1992 only in BG unigauge policy Controversy now regarding adoption of Standard Gauge

Sleepers

Transverse ties that are laid to support the rails

Functions: Maintaining the gauge and alignment Giving a firm and even support to the rails Transferring load from rails to ballast Acting as an elastic medium to absorb shocks and vibrations.

Common types of sleepers:

Wooden Metal: Steel/cast iron Concrete: RC, pre-stressed

Comparison of Sleepers

Characteristic Wooden Metal Concrete

Service life (yrs) 12-15 40-50 50-60

Weight for BG (kg) 83 79 267

Maintenance Expensive Medium Cheap (fully mechanized)

Gauge adjustment Difficult Easy Not possible

Damage (decay, corrosion etc.)

High High Low

Elasticity Good Good Best

Creep High Medium Low

Re-usability Low High Not resuable

Sleeper Density

Depends on following factors: Axle load and train speed Type and strength of sleeper Type and section of rail Type of ballast and formation

Common values for modern BG track:

1600/km for trunk routes 1540/km for less important routes

Sleeper density is not constant. Higher near joints.

Ballast

Layer of broken stones, gravel or any other granular material packed below and around sleeper for distributing load from the sleeper to the formation.

Functions: Transfers and distributes load from sleepers to formation Holds the sleepers in position during passage of trains Provides effective drainage Provides elasticity and vibration/shock resistance Provides lateral and longitudinal stability thereby

maintaining level and alignment of the track

IR uses 50-mm ballast for most track.

Points and crossings are subjected to heavy blows from moving loads and are maintained more precisely. They require 25-mm ballast because of its fineness for slight adjustments, compaction and increased frictional area.

Ballast

Most commonly used: Broken stone ballast

Ballast properties. Must satisfy IR specifications on: Size and gradation Shrinkage Aggregate impact value Aggregate abrasion value Flakiness index Specific gravity and water absorption

Ballastless track used for High-speed rail in China Rails supported on a precast slab using concrete pads High initial cost, low maintenance cost

Formation/ Sub-grade

Naturally occurring soil which is prepared to receive the ballast.

Functions Provide a smooth and uniform bed for laying the

track

Bears load transmitted Facilitates drainage Provides stability to the track

Fittings and Fastenings

To hold the rails in their proper position in order to ensure the amooth running of trains

Fishplates rail to rail Dog spikes rail to wooden sleepers Loose jaws rail to steel sleepers Tie bars and cotters rail to cast iron sleepers

Welding (flash butt/thermite) Greater ride comfort, higher speed Low maintenance, higher initial cost

Rail-sleeper fastening

Splice/spike Hole through

foot and bolt

Used for wooden sleepers

Rail-sleeper fastening

Chairs Connect web to

sleeper

Subject to more wear and tear

Used for wooden sleepers

Rail-sleeper fastening

Clips Connect foot to sleeper Less wear and tear Shown in figure:

Pandrol clip used by IR on all concrete sleepers

Turnouts

Tongue rail (movable, can withstand wear)

Stock rail (fixed)

Crossing (flange crosses over)

To go from one track to another

Wheels are provided with inside flanges and hence require special arrangement to navigate their way.

Switches or points aid in diverting the vehicles

Crossings provide gaps in the rails so as to help the flanged wheels to roll over them.

A complete set of points and crossings along with lead rails is called turnout.

Tongue rail or switch rail It is a tapered movable rail. At its thicker end, it is attached to a running rail.

Stock rail running rail against which a tongue rail operates

Points or switch A pair of tongue and stock rails with necessary connections and fittings

Crossing

Device introduced at the junction of two rails

Designed to allow the flange to pass from one rail to another

Crossing

Double crossing

Notice that both straight and left turnings are allowed

Railway EngineeringIndian Railways The highs!Classification of Indian railway lines GroupsGroup C linesComponentsTrack or Permanent Way Track StructureSlide Number 9Slide Number 10Track modulusRailsFunctionsRails - Historical EvolutionSlide Number 15Standard IR sectionsTrack Alignment GaugeType of Gauge system in IndiaChoice of gaugeSleepersComparison of SleepersSleeper DensityBallastSlide Number 25BallastSlide Number 27Formation/ Sub-gradeFittings and FasteningsRail-to-rail joint using fish-plateSlide Number 31Rail-sleeper fasteningRail-sleeper fasteningRail-sleeper fasteningTurnoutsSlide Number 36Slide Number 37Slide Number 38Slide Number 39Slide Number 40CrossingCrossing