(6)

The engineering diseases caused by seasonal sulfate saline soil in Hexi region of Gansu Province seriously affect the local infrastructure construction and operation maintenance. To address this issue, this study explored the thermal mass transfer law, pore fluid phase transition, soil deformation and microstructure of unsaturated sulfate saline soil under the open system. Firstly, based on the theories of porous media mechanics and continuum mechanics, combined with the conservation equations of mass, energy and momentum and considering the phase transition of pore fluid, a multi-field coupled mathematical model of hydro-thermal-salt-gas-mechanical for unsaturated sulfate saline soil was established. Secondly, basic unknown variables such as pore water pressure, concentration, temperature, porosity, and displacement were selected to perform numerical simulation analysis on the equation system by Comsol Multiphysics finite element method. Finally, a comparative analysis was conducted between the on-site measured data and the numerical simulation results. The results show that the water and salt phase transitions caused by temperature change could lead to soil salt heave and frost heave, alter the pore structure of the soil, and reduce the compactness of the soil, ultimately being reflected in the changes in soil porosity. The influence of external temperature on soil temperature gradually decreases with increasing depth, and the sensitivity of frozen areas to external temperature is much higher than that of unfrozen areas. This study not only enriches the theoretical results of thermal mass transfer law and deformation of unsaturated sulfate saline soil, but also provides practical guidance for the prevention and control of engineering diseases in local sulfate saline soil.

来源平台：JOURNAL OF MOUNTAIN SCIENCE