Abstract
The substantial increase in excess pore pressure and plastic strain in subgrade soil due to faster and heavier trains is a major cause of track instability. Stresses that occur in track substructure during the passage of trains have not often been captured accurately due to insufficient rigour in dynamic analysis. This paper presents a numerical investigation into the plastic/dynamic characteristics of a saturated porous medium (capping and subgrade) subjected to moving axle loads. In this study, a detailed numerical analysis is described, whereby a coupled fluid-dynamic framework is developed for the saturated porous medium in conjunction with a generalized plasticity model, in order to examine the cyclic loading response of a soft subgrade soil. The constitutive model is calibrated by undrained cyclic triaxial testing carried out on a soft foundation soil retrieved from a coastal railroad site having a historical record of mud pumping. Kelvin elements are attached to the