Why Crushed Stones Are Used In Railway Track:
The technical term for these crushed stones is “Ballast or track ballast. A tamping machine is used to pack the track ballast under railway tracks to make the tracks more durable. Usually, a 25–30 cm thick ballast layer (crushed stone 30/60) below the bottom face of sleeper is provided along the track. This thickness varies based on many parameters and conditions.
Following are the reasons for using crushed stones on railway track:
1. To hold the sleepers in place, both laterally and longitudinally (as they, in turn, hold the rails in place & help maintain gauge.
2. To distribute the load of entire moving cargo from rails into the sub-base/formation (ground below the ballast.
3. To maintain the support of and distance between the cross ties.
4. To restrain heat expansion & contraction (due to thermal stresses), and ground movements.
5. To dampen the vibrations — as ballast provides cushioning effect (thus rendering elastic property to the railway track).
6. To absorb vibrations — The air voids present between the stones absorb vibrations and make it comfortable, not only for the traveling passengers but also for the residents next to tracks.
7. To facilitate drainage & stop building up of precipitation from rough weather (which can help — relieve frost heaves & maintain necessary shear stress in sub-base).
8. To overcome weed & plant growth from underneath.
9. To absorb much of the sounds & noises produced by train movements.
10. Minor adjustments can be made in the track as and when required.