Field evaluation of a novel thermally controlled subgrade for mitigating frost heave

Tianfei Hu, Liqi Zhao, Tengfei Wang, Zurun Yue, Yifei Yuan, Yimin Zhang and Dechao Cai

International Journal of Rail Transportation, 2025, vol. 13, issue 6, 1114-1134

Abstract: A new type of thermally controlled subgrade is proposed to mitigate persistent frost heave issues of railway subgrades in seasonally frozen regions. A dedicated ground-source heat pump system collects low-grade geothermal energy from the stable soil layer near the subgrade, converts it into high-grade thermal energy, and transfers it to the frigid subgrade for active heating and temperature control, thereby eliminating the adverse effects of frost heave. A 20-metre-long test section of thermally controlled subgrade was constructed in a frost heave section of the Junggar-Shenchi Railway in Shanxi Province, China. During the winter spanning 2021 and 2022, the heating temperature of the heat pump, the thermal regime of the test section subgrade and the natural subgrade, the frost depth, and the track heave were measured. The results indicate that the heat pump temperature could reach a peak of 59.4 °C, with the average daily heating temperature during intermittent operation reaching 25.2 °C or higher, indicating an efficient heat source that plays a favourable role. The freezing period of the natural subgrade lasted for 141 days, while the subgrade in the test section was 20 days shorter. The maximum frost depths at the track centre, shoulder, and embankment slope toe in the test section were 88 cm, 75 cm, and 58 cm, respectively. These depths were 60 cm, 122 cm, and 78 cm less than those of the natural subgrade, effectively controlling the frost depth within the threshold that may cause potential structural damage. Under natural conditions, the track heave reached a peak of 9.4 mm, leading to a harmful frost heave scenario. In contrast, the track deformation in the test section was less than 3 mm, which did not exceed the regular maintenance threshold. The thermally controlled subgrade proves to be an effective method for preventing and controlling persistent frost heave damage in critical locations such as low embankments, cut section subgrades, turnout areas, and culvert roofs.

Date: 2025
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DOI: 10.1080/23248378.2024.2443978

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International Journal of Rail Transportation is currently edited by Wanming Zhai and Kelvin C. P. Wang

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