Study on thermal-hydro-mechanical coupling and stability evolution of loess slope during freeze-thaw process

Disasters occurring at loess slopes in seasonal frozen regions are closely related to changes in the thermo-hydro-mechanical (THM) state in loess by freeze-thaw (FT) action. Current research on FT-induced soil slope failure focuses on frozen stagnant water effects, while the intrinsic connection between the FT-induced stagnant water effect and soil strength deterioration remains unclear. In this study, by taking the FT-induced loess slope failure as an example, field surveys, boreholes, exploratory wells, and 3D topographic mapping were used to reveal the landslide features and stratigraphic information; Furthermore, the temporal and spatial variation of water and heat in loess slope was revealed by on-site monitoring data; A THM coupled model of frozen soil was established using COMSOL Multiphysics simulation software to reconstruct the frozen stagnant water process of shallow loess slope, as well as the influence of THM field on loess landslide. The results show that the effects of FT in the seasonally frozen region occurred in the shallow layer of the loess slope. The water-ice phase transition during FT process broke the phase equilibrium of loess. Numerical calculations and field monitoring indicated a continuous migration of water to the freezing front, creating a water-enriched zone inside the loess. Both the impact of the frozen stagnant water and changes in the stress field led to the degradation of loess structure and reduced the strength properties, thus threatening the stability of the loess slope. The study results can contribute to an in-depth understanding of the mechanism underlying FT loess landslides in seasonal frozen regions, and provide a scientific basis for the evaluation and prevention of FT landslides. In the process of freezing and thawing, water migration occurs in the loess slope, resulting in the frozen stagnant water effect, which makes the water enriched in the slope. This makes the mechanical strength parameters of loess deteriorate. The effect of frost heave and thaw settlement destroys the soil structure and makes the soil particles rearrange. This threatens the stability of loess slope. image