Analysis of deformation mechanism of rainfall-induced landslide in the Three Gorges Reservoir Area: Piansongshu Landslide

Abstract The Three Gorges Reservoir Area (TGRA) has unique geological conditions that result in the formation of landslides. These landslides are prone to instability when exposed to external factors like rainfall. This study focuses on the Piansongshu landslide in the TGRA and aims to analyze the internal deformation mechanism of rainfall-induced landslides, providing valuable insights for landslide prevention and control. The study begins with field geological investigations to analyze the macroscopic deformation signs and deformation mechanisms of the landslide. GeoStudio numerical simulation software is employed to assess landslide stability, considering changes in internal seepage fields and stability under varying rainfall conditions. The results indicate that with continuous rainfall, a transient saturation zone appears on the slope's surface and extends downwards. The accumulation front edge's infiltration line protrudes towards the surface in areas with greater deformation. The stability coefficient of the landslide's secondary shear surface exhibits more significant variation compared to the overall sliding surface. Higher rainfall intensity and duration lead to a greater decrease in the stability coefficient. Different types of rainfall also impact stability differently. Over time, as rainfall infiltrates, the slope safety coefficient gradually decreases. Even after rainfall ceases, the stability coefficient continues to decline, requiring time for recovery until it reaches a stable state.