Influence of freeze-thaw of ballasted track on vehicle vibration and its evaluation

In the seasonally frozen regions, railway subgrades are subjected to freeze-thaw cycles due to environmental temperature change. The railway track is likely to be deformed during the freezing and thawing processes of subgrades. As a result, the train operations will be severely affected. In the present study, the track deformation induced by the freeze-thaw of railway subgrade was investigated. In the freeze-thaw analysis, different types of the buried structure (for example, box culvert, pipe culvert) embedded in the subgrade were selected as an analytical example, as the transition section of buried structure owning complex boundary conditions is likely to experience significant frost heave and thaw settlement. The track surface deformation above the transition section was calculated through finite element analysis, considering the influences of groundwater levels and temperature boundary conditions. Two indices, namely, wavelength and amplitude, were used to quantify the surface deformation. The influence of variation of groundwater level and different seasonal temperatures on the deformation was investigated from the aspects of absolute value. Subsequently, to evaluate the influence of subgrade freeze-thaw induced track deformation on train vibration, the vehicle dynamic analysis was conducted using a vehicle-track model. The calculated absolute value of track deformation was inputted into the vehicle-track model as excitation. Finally, the car body vibration was evaluated from the aspect of safety (minimum vertical wheel-rail force and maximum vertical wheel-rail force) and stability (car body acceleration and Sperling index). This study can facilitate understanding the influence of subgrade freeze-thaw on vehicle vibration.