Discrete Element Modelling of Track Ballast Capturing the True Shape of Ballast Stones

Railway ballast affected by heavy cyclic loading degrades and spreads resulting in an uncomfortable transportation caused by undesirable vibrations. Restoring a well sorted track ballast can be expensive. This paper analyzes track ballast deformation using the Discrete Element Method (DEM). The simulations are performed using the STAR-CCM+ software in a three-dimensional domain. Four track ballast models are studied. The first two models describe the ballast as spheres with and without rolling resistance, respectively. The third model uses a clump model that allows breaking of the ballast, whereas the fourth model describes the ballast as composite particles generated from 3D-scanned ballast stones. The sleepers and rails are modelled as DEM particles. As a supplement to the study of different ballast models, the influence of variation in the loading profile is investigated. The largest obtained deformation is observed in the ballast modelled as spheres and the smallest deformation in the ballast modelled from the 3D scanned ballast stones. The results highlight the importance of describing the ballast as non-spherical geometries.