Ballast :-
Ballast is the granular material usually broken stone or brick, shingle or kankar, gravel or sand. It provides a suitable foundation for the sleepers. It also holds the sleepers in their correct level and position. The lateral stability of a track depends on it.
Functions of ballast :-
Ballast performs the following functions –
- Transfers the load from the sleepers to the subgrade and then distributes it uniformly over a larger area of the formation.
- Holds the sleepers in position and prevents the lateral and longitudinal movement due to load transfer.
- Imparts some degree of elasticity to the track.
- Provides easy means of maintaining the correct levels of two lines of a track.
- Corrects track alignment.
- Provides good drained foundation immediately below the sleepers and help to protect the top surface of the formation.
Types of Ballast :-
- Broken Stone
- Gravel / Shingle / River Pebbles
- Ashes / Cinders
- Sand
- Moorum