Shallow Stability Analysis for Unsaturated Clay Slope of Subgrade under Rainwater Infiltration

In order to evaluate the shallow stability of unsaturated clay slope induced by rainfall, the defects of the infinite slope method based on the "parallel slope-plane" failure mode ignoring the anti-sliding effect of the upper and lower edges of the sliding body were analyzed. The shallow failure mode of composite "parallel slope-curve" including a upper tension zone and a lower squeeze zone for arc surface of different center, and a main sliding zone in the middle was presented. The geometric equations of composite surface and sliding equilibrium equations of slide body were also deduced. In accordance with the shear strength model of dual stress state variables for unsaturated soils, an analysis method of shallow stability for unsaturated clay slope under rainwater infiltration was established, which can reflect the effect of rising water level on the inner parallel slope surface. The results show that the safety factor decreases linearly with the decrease of the adsorption strength of the soil in the early stage of rainwater infiltration into the unsaturated clay slope. In the later stage, the rainwater infiltrates into the impervious or weak permeable layer to form a thin layer of water, which causes a sudden change in the safety factor, and intensifies the possibility of slope instability. The research can provide reference for the study of subgrade slope stability considering rainfall characteristics. © 2021, Department of Journal of the China Railway Society. All right reserved.