Water is the greatest threat to a railway track, and the most prominent factor that adversely affects track maintenance is improper drainage. Excess water affects the stability of the embankment, and the bearing capacity of the soil and its resilience to shear gets considerably reduced. Railway engineers give maximum importance to the proper drainage of the track and the need to do so is felt because of the following concerns.
Settlement of embankment Excess water may cause the embankment to settle. An unequal settlement may lead to variation in cross levels as well as longitudinal levels thereby affecting the safety and riding quality of the track.
Reduction in bearing capacity The bearing capacity of the soil as well as its resistance to shear diminishes due to excess water in the soil. This in turn leads to numerous problems and finally affects the safety and stability of the track.
Failure of embankment The percolation of water in the embankment increases the weight of the soil on the one hand and reduces its bearing capacity and shear resistance on the other. This makes the formation unstable. This is a common reason for the failure of embankments, which occurs in the form of slips.
Formation of ballast pockets Excess moisture leads to punctures in the formation. The constant hammering action of running trains causes the sleepers to move up and down, resulting in ballast pockets, pumping sleepers, and other such problems. All these factors lead to poor riding quality.
Shrinkage and cracking of banks The embankment soil cracks and shrinks once excess water dries up. The problem becomes acute in the case of poor soils. This in turn leads to many problems such as the loss of ballast in the cracks and uneven settlement, which have an adverse effect on track maintenance.
Adverse effects of black cotton soil There are certain soils, such as black cotton soil, which become plastic in nature due to the accumulation of excess water. The
formation shrinks due to change in moisture content. The bearing capacity of the soil is greatly reduced due to the excess water. These problems imperil the safety of the track.
Formation of slush Slush is formed due to the dynamic load of running trains. It is forced out, thus badly clogging the ballast. This makes the maintenance of the track very difficult.