Impact of subgrade cross-sectional forms on the thermo-mechanical stability of high-speed railway subgrades in cold regions

This study investigates the impact of subgrade cross-section configurations on the thermal-hydraulic-mechanical stability of anti-frost heave subgrade structures, essential for the safe operation of high-speed railways in cold regions. Focusing on the Mudanjiang-Jiamusi high-speed railway in China's deep seasonal frozen soil region, we analyzed typical subgrade cross-sections using a combination of field measurements and field-based analyses. The objectives are as follows: (1) to examine temporal and spatial temperature variations in the anti-frost heave subgrade structure across different cross-sections, with frost depths reaching 2.4–2.8 m; (2) to analyze changes in water content with depth and temperature, noting a 15 % drop in unfrozen water content near 0 °C in winter and a 10 % increase during thaw; (3) to characterize layered deformation evolution and its dynamics in relation to temperature and water content; and (4) to evaluate how the shady-sunny slope phenomenon and cross-sectional form affect subgrade stability. Key findings reveal that: (a) cross-section configuration strongly influences thermal state and water distribution within the subgrade; (b) the peak frost heave, ranging from 1.49 mm in embankments to 2.56 mm in cuttings, varies significantly with cross-section form; and (c) frost heave is affected by both frost penetration depth and the subgrade's hydrological conditions. These results provide a critical foundation for optimizing anti-frost heave subgrade design for high-speed railways in cold regions.