In response to subgrade frost heave damage in cold regions, an active heating method that utilizes geothermal energy is proposed. By using ground source heat pump technology, a dedicated heat regulation system and a distributed heating scheme are designed for the subgrade. A full-scale subgrade test platform is built to test the heating performance and subgrade thermal regulatory mechanisms of this system in winter. The test results show that in the operation mode with a start: stop ratio of 2 h:1 h, the heat regulation system can reach heat supply temperatures of 17∼33 °C. Moreover, the operating performance under cold winter conditions is stable. The coefficient of performance of the thermal regulation system can exceed 5.8, but it decreases with increasing time. The heat diffusion process from the heat supply pipe to the subgrade exhibits spatial hysteresis. Within 4 d, heat can diffuse in the vertical direction throughout surface layer of the subgrade. Furthermore, the magnitude of the increase in temperature gradually decreases with increasing distance from the heat supply pipe or with increasing time. After 4 d of heating, heat diffuses in the longitudinal direction at a distance of 125 cm in the subgrade. The variation in the freezing depth of the subgrade is controlled by both the atmospheric environment and the thermal regulation system. After 16 d of heating, the freezing depth decreases from 74 cm to less than 17 cm.
Hu et al. (2026) studied this question.