(1. School of Civil Engineering，Lanzhou University of Technology，Lanzhou，Gansu 730050，China；
2. China Railway Qinghai-Tibet Group Co.，Ltd.，Xining，Qinghai 810000，China)
Abstract：In order to study the distribution of coupled physical fields in the subgrade of saline soil，relying on the subgrade of Qinghai—Xizang Railway around Qinghai Lake，based on the modified traditional salt field equation，a water-salt-heat-force coupled mathematical model was established using the COMSOL custom partial differential equation and solid mechanics field module. By analyzing the physical field characteristics of groundwater buried under the condition of water and salt recharge at the boundary of open system，the evolution laws of moisture，temperature，salt，and displacement field within the soil mass were obtained. The results show that the soil moisture content shows a four-stage development trend of decreasing firstly，increasing rapidly，then decreasing slightly，and stabilizing finally in the region from the subgrade surface to the depth of －0.4 m，and the peak moisture content increases by 2.65 % compared with the valley value. The salt content of subgrade increases initially and then stabilizes in the region from －0.4 m to －2 m of subgrade，the maximum salt content increases by 2% per meter on average，and the growing rate is proportional to the depth. The response of soil temperature to external temperature change has obvious lag phenomenon under －2 m depth of subgrade，and the lag time is about 30 d for each 1m depth increase. The maximum expansion displacement and salt frost heave height difference are 1.42 cm and 2.64 cm respectively，and the winter expansion displacement accounts for more than 32.2% of the salt frost heave displacement.
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2025, Vol. 44 
