Influence of subgrade frost heave on ballasted track dynamics via a hybrid DEM-vehicle model

Abstract

Subgrade frost heave presents a significant threat to the operational safety of ballasted railways in cold regions. To evaluate the impact of frost heave deformation on the vehicle-track coupled system, a discrete element method (DEM) model for the ballasted track-subgrade structure and a vehicle-track dynamic model were established and non-iteratively coupled through the wheel-rail interface. The microscopic mechanical evolution and dynamic response characteristics of the track-subgrade system were systematically analyzed. Results indicate that frost heave disrupts the interlocking structure of ballast, leading to increased porosity and uneven stiffness distribution, which subsequently induces unstable dynamic responses. The primary load-bearing path (i.e., strong force chain) shifts from beneath the sleeper toward the frost heave boundary, resulting in unsupported sleepers at the transition between frozen and unfrozen zones. For a given frost heave amplitude, the shorter frost heave lengths produce a greater number of “unsupported sleepers”. Under high-speed operation, frost heave length shorter than 8 m with amplitudes up to 30 mm significantly elevate vertical wheel-rail forces and vehicle body accelerations, thereby presenting serious risks to operational safety.