Filtration behaviour of granular soils under cyclic load

A layer of granular materials known as ‘sub-ballast’ is usually placed between the ballast and the subgrade of a railway track to provide an effective drainage layer by preventing migration of fines from the subgrade into the top ballast layer or vice versa. In a poorly designed sub-ballast the presence of excessive water, coupled with high pore water pressure within a subgrade subjected to cyclic loads, increases the possibility of migration of fines in the form of slurry into the uppermost ballast layer. The continuous migration of subgrade slurry affects the track performance, resulting in fouled track and occasional loss...