Railway Engg 1.3

8/11/2019 Railway Engg 1.3

http://slidepdf.com/reader/full/railway-engg-13 1/37

UNIT 1-RAILWAY

ENGINEERING

• sleepers, various types, spacing and density, ballasts.

Namesh Killemsetty ^ Transportation Engineering II: Railway Engineering^ Sem 5 (2014) ,Civil @ OPJIT

Railway Engineering

TRANSPORTATION ENGINEERING II



Sleepers

• Rails have to withstand the heavy load from thelocomotives and the coaches

• In the absence of sleepers, the track would just

settle down.

• Hence the need of these transverse memberscalled sleepers


Railway Engineering



Function of sleepers

• Holding rail in proper gauge and level

• Act as elastic medium

•

Support the rails firmly and evenly• Distribute the load transmitted from the from the

rolling stock over large area of ballast

• Provides stability to the permanent way


Railway Engineering



Requirements of Sleepers

• They should be sufficiently strong to act as a beamunder loads

• The sleepers should be economical

•

They should maintain correct gauge• They should provide sufficient bearing area for the rail

• The sleepers should have sufficient weight for stability

• They should facilitate easy fixing and taking out of railswithout disturbing them.

• They should be able to resist impacts and vibrations ofmoving trains.

• They should be suitable for each type of ballast.


Railway Engineering



Types of sleeper

Sleepers are of the following types:

1. Wooden Sleepers

2. Steel Sleepers3. Cast Iron Sleepers

4. RCC Sleepers

5. Prestressed concrete sleepers


Railway Engineering



Wooden Sleepers

• The life of wooden sleeper depends on their abilityto resist wear, attack by white ants and quality oftimber used.

• Timbers commonly used in India for sleepers areSal, Teak, Deodar and Chirwood.


Railway Engineering



Wooden Sleepers

• The standard sizes for different gauges:

• For B.G. – 2740 mm x 250 mm x 130 mm

• For M.G. – 1830 mm x 203 mm x 114 mm

• For N.G –

1520 mm x 150 mm x 100 mm


Railway Engineering



Wooden Sleepers

Advantages:

• Easily available in all parts of India

•

Suitable for all types of ballast• Require less fastenings and simple in design

• Give less noisy track

• Absorb shocks and vibrations more than any othersleepers

• Best suited for track circuiting


Railway Engineering



Wooden Sleepers

Disadvantages

• Life is less as compared to other sleeper types

•

Sleepers are subjected to wear, decay, attack bywhite ants, etc.

• Track laid over wooden sleepers is easily disturbed

• Maintenance cost is more as compared to other

sleepers.


Railway Engineering



Steel Sleepers

• Consist of steel troughs made of 6mm thick steelsheets, with its both ends bent down to check therunning out of ballast.

• At the time of pressing of sleepers, an inward slopeof 1 in 20 on either side is provided to achieverequired tilt of rails.

• Standard length of these is 2680mm.

• Steel sleepers are of two types:

• Key type steel sleepers

• Clip and bolt type steel Sleepers


Railway Engineering



Steel Sleepers


Railway Engineering



Steel Sleepers

• Key Type Steel Sleepers

• Lugs or jaws are pressed out of metal and keys are usedfor holding the rails.

•Lugs are formed by forming the pressing out of themetal of the channel section.

• Loose jaw type is an improvement on pressed lug type.


Railway Engineering



Steel Sleepers

• Clip and Bolt type Steel Sleepers

• Clips and bolts are used for holding the rails.

• Cracks are not developed in the sleepers as the holes for

the bolts are small and circular.• Requires four bolts and four clips for holding each rail.


Railway Engineering



Steel sleepers

Advantages:

• Are light in weight and can be handled easily.

•

Require less fastenings• Life is more than the wooden sleepers

• Gauge can easily be maintained and adjusted

• Scrap value is more than the wooden sleepers.


Railway Engineering



Steel Sleepers

Disadvantages

• Initial cost is more than steel sleepers

•

Cracks are developed at rail seat of these sleepers• Are not suitable for track circuiting

• Not suitable for all types of ballast

• Liable to corrosion


Railway Engineering

l



Cast Iron Sleepers

• Are made of cast iron and extensively used in Indiaas compared to other countries

• Are of following types:

• Pot or bowl sleepers

• Plate sleeper

• Box sleeper

• CST-9 sleeper

• Duplex Sleeper


Railway Engineering

il i i



Cast Iron Sleepers•

Pot or bowl sleepers• Pot sleepers consist of two bowls placed under each rail

and connected together by a tie bar.

• Total effective area of both the pots is 0.464m

• On top of each pot, a rail seat is provided to hold rails atan inward slope of I in 20


Railway Engineering

R il E i i



Cast Iron Sleepers

• Plate Sleeper• Consist of two rectangular

plates of 864 mm x 305 mmin size with short sizeparallel to rail.

• Plates are provided rib inthe bottom to provide agrip in the ballast for lateralstability., held in position bytie-bar.

• It provides an effectivebearing area of 0.464 sq mper sleeper


Railway Engineering

R il E i i



Cast Iron Sleeper

• Box sleeper

• Not in use these days

• Are similar to plate sleepers

• A box is provided at the top of each plate to hold therails.


Railway Engineering

R il E i i



Cast Iron Sleeper•

CST-9 Sleeper• Extensively used in Indian Railways since thirty years

• It is a combination of pot, plate and box sleeper

• Consists of a triangular inverted pot one on each side ofrail seat

• Rail seat is provided at the top to hold rails at 1 in 20inward slope.


Railway Engineering

R il E i i



Cast Iron Sleeper

• Duplex Sleepers• These sleepers are used at rail

joints to prevent cantileveraction between two supports

of CST-9 sleepers.

• Consist of two plates each ofsize 850 mm x 750 mm.

•

Plates are placed with thelonger side parallel to the railsand are connected with a tie-bar.


Railway Engineering

Railway Engineering



Cast Iron Sleeper

Advantages

• life of C.I sleepers is more

• Maintenance cost of these sleepers is less

• Gauge can easily be maintained and adjusted withthese sleepers

• Sleepers are more durable


Railway Engineering

Railway Engineering



Cast Iron Sleeper

Disadvantages

• More ballast is required than other type of sleepers

• Number of fittings required is more

• Sleepers are liable to break

• Are not suitable for track circuiting

• Not suitable for all types of ballast


Railway Engineering

Railway Engineering



R.C.C Sleepers

• Through type RCC sleepers

• Known as one piece or monoblock sleeper.

• Cracks develop on the tension side when stressed

• These cracks are very small and almost invisible but tendto enlarge with the repetition of impact loading, causingfailure


Railway Engineering

Railway Engineering



R.C.C Sleepers

• Block and tie type RCC sleeper

• Consist of two RCC blocks connected by a metal tie ofinverted T section.

•These sleepers are not subjected to any degree ortensile stress.


Railway Engineering

Railway Engineering



R.C.C Sleepers

Advantages

• Have long life, generally 40-60 years

• Free from natural decay and attacks by insects, etc

• These require less fittings

• Track circuiting is possible in these sleepers.

• Maintenance cost is low

• Provide more lateral and longitudinal rigidity ascompared to other sleepers.


Railway Engineering

Railway Engineering



R.C.C Sleepers

Disadvantages

• Due to heavy weight, handling and transportationof these sleepers is difficult.

• If not handled properly, the chance of breaking ismore.

• Renewal of track laid with these sleepers is difficult

• The scrap value is nil.


Railway Engineering

Railway Engineering



Prestressed Concrete Sleepers

• Nowadays extensively used in Indian Railways

• Have high initial cost but are very cheap in long runbecause of their long life

• High tension steel wires are used in the sleeper

• these sleepers are heavily damaged in case ofderailment or accident of trains.


Railway Engineering

Railway Engineering



Sleeper Density

Sleeper density is the number of sleepers used perrail length on a track. The density of sleepersdepends upon the following factors:

• Axle load of train• Lateral thrust of locomotives

• Methods of providing rail joints

• Speed of train

•Type of ballast

• Type and section of rails.


Railway Engineering

Railway Engineering



Sleeper density

• Since sleeper provides lateral stability to the track, so morethe number of sleeper more is the lateral stability.

• The number of sleepers, however, cannot be increasedindefinitely as a certain minimum spacing between sleepers

is required for packing of ballast.• Sleeper density is indicated by (n+x), where n is the length

of the rail in metres and x is the number of sleepers inexcess of n.

• In india, number of sleepers per rail length is n+3 to n+6

•

In India, sleeper density of 18 sleepers per rail length isprovided.

• All the sleepers are not provided at equal spacing. At rail joints, the sleepers are kept closer as compared to otherparts to the rail.


Railway Engineering

Railway Engineering



BALLAST

Ballast is the granular material usually broken stoneor any other suitable material which is spread on thetop of railway formation and around the sleepers


Railway Engineering

Railway Engineering



FUNCTIONS OF BALLAST

• To hold the sleepers in position and preventing thelateral and longitudinal movement.

• To distribute the axle load uniformly from sleepers

to a large area of formation.

• To provide an east means of maintaining thecorrect levels of the two rails in a track.

•

To drain rain water from the track.• To prevent the growth of weeds inside the track.


Railway Engineering

Railway Engineering



CHARACTERISTICS OF GOOD

BALLAST• Should have sufficient strength to resist crushing under

heavy loads of moving trains.

• Should be durable enough to resist abrasion and weatheringaction.

• Should have rough and angular surface as to as providegood lateral and longitudinal stability to the sleepers.

• Should have good workability so that it can be easily spreadon formation.

• Should be cheaply available in sufficient quantity near or

along the track• Should allow for easy and quick drainage of track

• Should not have any chemical action on metal sleepers andrails.


Railway Engineering

Railway Engineering



TYPES OF BALLAST

• Broken stone (granite, quartzite, trap)

• Gravel

• Sand

•

Coarse sand• Ashes or cinders (waste products from steam

locomotives)

• Kankar (nodules from which lime is prepared)

• Moorum (obtained by decomposition of laterite)

• Blast furnace slag

• Brick ballast

• Hardened clay and decomposed earth


Railway Engineering

Railway Engineering



SIZE OF BALLAST

• Size of ballast used in railway track varies from19mm to 51mm.

• For wooden sleepers – 51 mm

•For steel sleepers

–38 mm

• For points and crossings – 25.4 mm

• The more the depth of ballast below the sleeper,more will be the load carrying capacity of the track.

• The depth of ballast remains uniform throughoutthe straight tracks, but on curves additional ballastis required to give the required super elevation.


Railway Engineering

Railway Engineering



SIZE OF BALLAST


y g g

Railway Engineering



QUANITITY OF BALLAST

• The quantity of ballast per metre tangent length is

• 1.036 cu.m. for broad gauge

• 0.071 cu.m. for metre gauge

• 0.053 cu.m. for narrow gauge

y g g

Documents

Railway Engg 1.3