Ballast is the granular material usually broken stone or any other suitable material which is spread on the top of railway formation and around the sleepers.
FUNCTIONS OF BALLAST:
- To hold the sleepers in position and preventing the lateral and longitudinal movement.
- To distribute the axle load uniform from sleepers to a large area of the formation.
- To provide elasticity to the track. It acts as elastic mat between subgrade and sleepers.
- To provide easy means of maintaining the correct levels of the rails in a track.
- To drain rainwater from the track.
- To prevent the growth of weeds inside the track.
CHARACTERISTICS OF GOOD BALLAST:
- It should have sufficient strength to resist crushing under heavy loads of moving trains.
- It should be durable enough to resist abrasion and weathering action.
- It should have a rough and angular surface so as to provide good lateral and longitudinal stability to the sleepers.
- It should have good workability so that it can be easily spread of formation.
- It should be cheaply available in sufficient quantity near and along the track
It should not make the track dusty or muddy to its crushing to powder under wheel loads.
- It should allow for easy and quick drainage of the track.
- It should not have any chemical action on metal sleepers and rails.