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.

In the actively evolving research of Mars in recent decades, a special place is occupied by landers and rovers. The diversity of landscapes and soils on Mars, characteristic of terrestrial planets with an atmosphere, makes the development of soil simulators relevant for each new type of terrain in the area of a potential landing site. In the article, based on a comprehensive analysis of the physical and mechanical properties of soils at previous landing sites and a geomorphological analysis of the Oxia Planum plain, the main requirements for the properties of Martian soil analog at the landing site of the ExoMars Rosalind Franklin Mission (RFM) were determined. Readily available technogenic and natural materials have been selected and experimentally justified as components for creating a Martian soil analogue. A methodology for creating the soil analog is presented, and its physical and mechanical properties are measured. The developed Martian soil analog VI-M1 is actively used for large-scale natural experiments, including drop tests of spacecraft in the ExoMars series.