Comparison of Bearing Behavior Between I-shaped and X-shaped Sleeper Using DEM Coupled Simulation

A new type of X-shaped sleeper was developed to increase the lateral resistance compared to conventional I-shaped sleepers. A series of sleeper push-out test simulations using discrete element method (DEM) and multi-body dynamics (MBD) were carried out. The contact forces between the sleeper and different zones of the ballast layer were measured. The ballast particle movement and the disturbance of the subballast and subgrade during the sleeper push-out were investigated from the macro-view and micro-view. The results indicate that the lateral resistance of a single X-shaped sleeper was increased by approximately 22.4% compared to the double I-shaped sleepers. Moreover, the frictional resistance of sleeper base is relatively close for both, primarily related to the bottom area. Simultaneously, the V-fork arms of the X-shaped sleeper increase the total resistance between the sleeper sides and the ballast, nearly 2 times compared to the I-shaped sleepers. From the micro-view of the particle movement and contact force distribution, it proved that the disturbance area in the crib ballast for the X-shaped sleeper appears larger, with a greater number of crib ballast particles actively participating in impeding the lateral movement of the sleeper. Similarly, the stress distribution of subgrade indicates the active involvement of the bottom ballast and subgrade in sharing the lateral resistance of the track bed.