Safety-state evolution of the vehicle–track–subgrade system in seasonally frozen regions
Abstract
Frost heave of railway subgrades in seasonally frozen regions can severely threaten the safe operation of railway lines. However, the evaluation criteria for railway operational safety remain inconsistent. In this study, a discrete element model of a ballasted track–subgrade system and a vehicle–track dynamic model were established. The dynamic response parameters of the structural components under different calculation conditions were obtained. By comprehensively considering the key indicators at the vehicle, track, and subgrade levels, a coupled evaluation model integrating unascertained measure theory and set pair analysis was developed to calculate the operational safety coefficient of railways in seasonally frozen regions. The results show that deformation induced by subgrade frost heave can be significantly transmitted to the track structure and is manifested as a cosine-like deformation pattern in the rails, thereby intensifying the dynamic responses of the vehicle–track–subgrade system. Frost heave of the subgrade is likely to induce sleeper voiding in the transition zone between the frost-heaved and non-frost-heaved layers, causing key indicators such as rail vertical displacement, sleeper vertical displacement, and subgrade vertical displacement to exceed the maximum allowable values specified in relevant standards. Subgrade frost heave reduces the operational safety coefficient of the system, and this coefficient is closely related to train operating speed; higher speeds correspond to greater operational risk.