Dynamic Performance of Wedge-Shaped Self-Leveling Sleepers in Railway Transition Zones

Hanging sleepers, which result from the differential settlement of the ballast layer, are a prevalent issue that leads to the rapid degradation of track components that include the ballast, sleeper, fastener, and rail. A novel type of sleeper, the wedge-shaped self-leveling sleeper (WSS), was proposed as a solution to the hanging sleeper problem. The WSS leverages the train’s dynamic loading and the gravity of the ballast to naturally allow the ballast particles to fill the gap between the ballast and the sleeper. This paper focuses on the dynamic performance of the WSS from different aspects, which include wedge angles (30°, 45°, and 60°), sleeper materials (concrete and plastic), and the number of WSS to replace regular sleepers in the transition zone. A series of numerical modeling [which coupled multibody simulation (MBS) and discrete-element methods (DEM)] were conducted to design, optimize, and test the WSS. The results reveal that a concrete WSS is well-suited to address the problem of hanging sleepers in transition zones. The WSS with a 45° angle demonstrated superior performance compared with other types of WSS. Importantly, the WSS could reduce vibrations in the vehicle and track, even when dealing with hanging sleepers. Due to the self-leveling function, the WSS shows significant promise for applications in transition zones, which could reduce the frequent need for track geometry maintenance.