Shallow failure mechanism of unsaturated soil slope during rainfall infiltration

The pore surface fractal dimension was used to characterize pore structure of soil, and the fractal model was applied to predict the hydraulic parameters of unsaturated soil. The degree of disturbance and the depth of atmospheric effect on unsaturated soil slopes in the rainfall-evaporation cycle were determined using two-dimensional infiltration calculations, and the distribution of matric suction change was chosen as an assessment index. The relationship between the pore surface fractal dimension, air-entry value, saturated permeability coefficient of the soil, rainfall intensity and the shallow failure form of unsaturated soil slopes was further analyzed. The results show that the change of matric suction due to rainfall infiltration is significantly greater than that of the volumetric water content. The pore surface fractal dimension, air-entry value, and saturated permeability coefficient of unsaturated soils are all positively correlated with the depth of atmospheric influence, with the intensity of rainfall having a lesser effect. Matric suction can be used as an evaluation index for the degree of slope disturbance and the depth of atmospheric influence. The pore surface fractal dimension, the air-entry value, and the saturated permeability coefficient of soil governor the form of shallow failure of unsaturated soil slopes, with a low correlation with rainfall intensity. This work provides reference for the investigation of shallow failure to unsaturated soil slopes and associated geological engineering issues. © 2024 Central South University of Technology. All rights reserved.