Numerical Modeling of the Effect of Fine Materials on Shear Behavior of Fouled Railway Ballast

Railway network has become the most economical and widely used transportation mode in many countries. This is mainly due to the frequent congestion of major highways which is caused by rapid urbanization. With this increasing demand for railway transportation, the need for heavier and faster trains too has increased. Introducing high-speed trains with heavy axel loads creates high stresses in the track layers and causes excessive settlement and degradation. Therefore, special attention must be given in understanding the behavior of track layers due to vibrations under dynamic loading. The ballast layer plays a crucial part in transmitting and distributing the wheel load from sleepers to the underlying sub-ballast and subgrade. Ballast becomes degraded and fouled by the progressive accumulation of fines between ballast voids due to repeated train loading and various external factors. This phenomenon leads to a change in ballast behavior such as shear and dilation. This study concentrates on analyzing the effect of fine material on the shear behavior of railway ballast material. To achieve this goal a 3D finite element model of ballast during large-scale direct shear test is developed using ABAQUS software. The model is calibrated and validated using data obtained during a previous study. A parametric study is carried on the shear behavior of ballast by varying normal stress and the percentage of fines. This model is then used to predict the effect of fine materials on the shear behavior of ballast.