Slope Stability Analysis Considering Effective Stress Law and Material Softening During the First Impoundment of a Reservoir

Abstract

ABSTRACT Slope failure near a reservoir area is mainly influenced by reservoir impoundment and rainfall. In this paper, a bank slope on the Lancang River near a hydropower station in Southwest China is studied. The FEM numerical model is established to investigate the deformation and stability of the bank slope, especially the influence of the reservoir impoundment and rainfall. Unbalanced force (UST) and the factor of safety of the potential failure surface are presented to quantitatively evaluate the monolithic stability of the slope. The numerical analysis results show that the slope reaches a critical state after the first impoundment. The maximum deformation is mainly located at the toe of the slope towards the riverbed. The failure mechanism can be explained that the bank slope especially the toe of the slope is softened by rainfall and water impoundment and the effective stress effect makes it easier for the slope to yield, which results in significant deformation or landslide failure. It is also demonstrated that the toe reinforcement has a significant effect on restraining the shear displacements of the slope and preventing the progressive failure of the landslide. This study presented a feasible approach for more accurate analysis of reservoir slope stability during impounding and rainfall, and also provided practical measures for slope reinforcement. INTRODUCTION Landslides will cause major threat to both lives and property worldwide, especially in regions of steep terrain and heavy rainfall (Xu et al., 2014). Due to the impoundment of many large reservoir dams, more and more landslides have been triggered and cause serious damage. Water is an important factor that influences the mechanical behaviour of geotechnical materials and is responsible for many engineering hazards (Vásárhelyi and Ván, 2006; Wang et al., 2014). The weakening effects caused by water will significantly influence the stability of the reservoir slope.