Deformation behaviour of gap-graded fouled ballast evaluated by a 3D discrete element method

The ballast fouling has been identified as a challenging issue in ballasted railway tracks due to huge maintenance costs. In this research, the deformation characteristics of gap-graded fouled ballast were studied from laboratory experiments and a Discrete Element Method (DEM). The fouled ballasts were prepared with different values of a fouling index, FI p . After the packing behaviour of fouled ballasts was studied by density tests, the stress-strain behaviour of them was studied from triaxial compression tests under both dense and loose states. It was found that the void ratio decreases with FI p up to 50%, then it increases with FI p . The results also indicate that the strain-hardening behaviour of ballast is weakened when fouled by FI p ≥ 30%. The DEM simulation by clump particles produce a similar stress-strain behaviour as the laboratory specimens than their spherical counterparts. The results also reveal that the dilation behaviour of ballast is deteriorated significantly when fouled by FI p > 50%. The peak frictional angle indicates that the strength properties of ballast are deteriorated significantly when fouled by FI p ≥ 30%. Therefore, we recommend that fouled ballast should be treated by a maintenance application when ballast is fouled by FI p > 30%.