Assessment of Subballast Filtration under Cyclic Loading

This paper presents an investigation into the seepage hydraulics of a layer of subballast filter subjected to cyclic loading in a fully saturated environment. A multilayer mathematical approach was used to predict the time-dependent permeability of this filter, with a reduction in porosity as a function of compression under cyclic loading, and the amount of base soil (<150?μm) trapped within the filter voids being the two main aspects of this proposed model. Laboratory test results conducted on a novel cyclic loading permeameter apparatus were used to validate the proposed model. The family of equations that are an integral part of the proposed model are then presented in the form of compact visual guidelines anticipated to provide a more practical tool for railway design practitioners.