# Railway Sleepers, Definition, Functions & Types

Railway Sleepers, Definition, Functions & Types

Sleepers - Sleepers are transverse support for a railway track to give stiffness to it. Transverse sleepers were introduced on the railway track for the first time in 1835 and now they have been accepted universally.

Functions of sleepers

1. To hold the rails to correct gauge and alignment.
2. To give a firm and even support to the rail.
3. To transfer and distribute the axle load through rail over a sufficiently large area of ballast.
4. To act as an elastic medium between the rails and ballast to absorb vibrations and blows of the moving wheels.
5. To maintain the alignment of the track.
6. To provide insulation for the electrified track.
7. To provide a proper grade, longitudinal and lateral stability to the track.
8. To provide means for easy replacement of rail fastening without disturbing the traffic during the service life.

Requirements of an ideal Sleepers

1. The initial, as well as maintenance cost, should be minimum.
2. The weight of the sleepers should be moderate so that it can be handled easily.
3. It should be easy to handle so that gauge may be adjusted easily and maintained correctly.
4. It should be shock and vibrations absorbent, developed due to passages of fast-moving trains.
5. The design of the material of sleepers should be such that it does not get damaged or break while packing below it.
6. The sleepers should have sufficient bearing area.
7. The sleepers should be so designed that it does not get distracted from its position easily by the passage of the trains.
8. It should have anti-theft and anti-sabotage qualities.
9. The design of sleeper and fastenings should be such that it is possible to remove and fix the rails easily.

Sleepers Density

The numbers of sleepers used per rail length are known as sleepers density. generally, one sleeper is employed for each one-meter length of the rail. It is specified as  (N + x)  or (M + x) is the length of the rail and x is a mathematical number which varies according to the followings factors

1. Axle load and speed of the train
2. Type and strength of rail
3. Type and strength of sleeper
4. Depth of ballast cushion
5. Nature of formation

Types of sleepers

1. Wooden Sleepers
2. Cast Iron Sleepers
3. Steel Sleepers
4. Concrete Sleepers

Also, read - Types of Rails