A study on frost heave and thaw settlement of soil subjected to cyclic freeze-thaw conditions based on hydro-thermal-mechanical coupling analysis

Frost heave and thaw settlement are the main cause for damaging the engineering structures in the region of seasonally frozen soil. The soil freeze-thaw (FT) deformation is a typical complex result of multiple physical fields and involves the process of water transfer, heat transfer, ice-water phase transition and stress redistribution. While the theory and model of frost heave have been studied for decades, less attention has been paid to the simulation for soil deformation under FT cycles. In this study, coupled equations for water, heat and the deformation of frozen soil are derived based on previous theories and are realized in numerical software. The volumetric water content of the frozen soil in the experiment was tested by nuclear magnetic resonance (NMR) technology, and the obtained data were imported into the model. Experimental soil samples were arranged in improved model equipment, and the temperature and frost heave at different heights of the soil column varied with time. The model validity and applicability based on the hydro-thermal-mechanical coupled equations is verified by comparing the results of both the experiment and numerical simulation. In this research, from the curves of the soil temperature change, water content distribution, water flux occurred at the soil bottom surface, as well as the displacement of frost heave and thaw settlement, and the pore size distribution, the characteristics of the soil subjected to cyclic FT conditions was analyzed. The existed theoretical model cannot well model the soil FT deformation. Therefore, this study may provide references for developing more accurate theoretical models on the soil subjected to FT cycles.