Dynamic Response of Railway Subgrade Under Train Load and Freeze–Thaw Action

In railway engineering research, there is a notable gap as existing studies often focus separately on train-induced vibrations or freeze–thaw cycle impacts on subgrades, lacking a comprehensive analysis of their combined effects on subgrade dynamic responses. This study developed a three-dimensional finite-element model of a double-track ballastless track railway subgrade. The model considers various conditions, including train speeds of 180 km/h, 200 km/h, and 220 km/h, and soil temperatures of 5 °C, −5 °C, and −15 °C, with typical subgrade materials. The results show that under train load, the maximum vertical displacement of the subgrade decreases as train speed increases. Conversely, the maximum vertical stress and acceleration are directly proportional to the train speed. When the train speed rises from 180 km/h to 220 km/h, the maximum vertical stress of the subgrade increases by 1.1% and 3.1%, respectively. As the soil temperature drops from 5 °C to −15 °C, the maximum vertical displacement of the subgrade decreases. The displacement reduces with increasing distance from the train load. At a specific point A, the maximum vertical stress increases by 2.02% and 1.43%, respectively. Additionally, the deformation of the railway subgrade is directly proportional to the temperature difference. These findings are valuable for understanding subgrade behavior and guiding railway construction in freeze–thaw-affected areas.