Study on the Variation of Physical and Mechanical Parameters of Gravel Soil Accumulation along Elevation under Rainfall

Rainfall is one of the main factors that induce landslides. In order to study the effect of rainfall on the physical and mechanical parameters of accumulation landslides, the Shuping landslide in the Three Gorges Reservoir area is taken as the object. By simulating the effect of typical rainfall, different elevation samples were taken in the physical model, and the permeability test and direct shear test were carried out at the sampling points to study the evolution law of permeability coefficient and shear strength parameters. The stability analysis of Shuping landslide accumulation body considering the change of parameters along the elevation was carried out. The results show that ignoring the variability of parameters along the elevation due to long-term rainfall will lead to overestimation of slope stability and unsafe design results. After 60 hours of rainfall, from the top to the bottom of the slope, the permeability coefficientkand internal friction angle f of the accumulation of the landslide decrease linearly, and the cohesive c increases linearly. Compared with the initial model,kand φ at the highest sampling point increased by 10% and 2.22%, c decreased by 21.09%, whilekand φ at the lowest sampling point decreased by 2.5% and 6.96%, respectively, and c increased 111.9%. When there is a combined effect of rainfall and reservoir water level in the same elevation, that is, considering the variation of parameters along the elevation of the landslide, compared with the action of the reservoir water level alone, the maximum deformation of the X direction of the 145m and 175m water level increased by 12.81% and 42.52%, respectively, and the stability coefficient decreased by 7.874% and 11.8%, respectively. The research results have reference significance for the stability analysis of accumulation landslides under rainfall conditions.

Keywords: Accumulation, Model test, Variability, Permeability coefficient, Shear strength parameters.