Study on the mechanism of water-induced degradation of slip zone soils and FDEM coupled simulation of slopes based on multi-scale characteristic

Abstract

The evolution of the mechanical properties of slip zone soils had a greater impact on the structure of slopes with large upper porosity and excellent infiltration conditions. Especially under the rainfall effect, it was easy to be affected by the infiltration effect of internal injury, which will lay a "hidden danger" for the slope body to trigger sliding in the secondary transformation process. In this paper, based on Haijiao ping landslide in Guizhou, SEM image recognition techniques were used to reveal the water-induced degradation mechanism of the sliding zone soil from multiple scales and the damage parameters were obtained. Meanwhile, the FDEM numerical model was established to simulate the stability of the slope coupled with indoor TCT test results. The results proved that the angle of internal friction decreased linearly with the increase of water content on the macroscopic scale, but the cohesive force showed an increase and then a significant decrease. The effect of matrix suction in the microscopic scale was significant at lower water content, the internal cohesion formed a large number of agglomerate structures to resist external deformation, but the microstructure was loose and porous after sufficient water immersion. The pore space spreads directionally and the area increases by 2.66 times. The cross-scale discrete-finite element coupled simulation method based on image recognition can visually respond to the macroscopic mechanical properties and stability change response of the slope body caused by microscopic damage. The water-induced degradation effect of rainfall on slip zone soils was the inherent factors for the initiation deformation of landslide. The artificial excavation was the external factor that triggered the slope to slide. This type of landslide was more concealed in its natural state and prone to deformation when excavated after long-term rainfall.