Analysis on the mechanism of bank slope sliding considering the effect of reservoir water fluctuation and sliding zone weakening

This study focuses on the Liangshuijing landslide in the Three Gorges Reservoir area, using theoretical analysis and numerical simulations methods to construct a strength weakening model for the sliding zone and proposes a criterion for seepage-driven landslide initiation. The influence of different water level rise and fall rates on landslide stability is analyzed using the finite element program Geo-Studio, and the evolution laws of bank slope seepage field under the rise and fall of reservoir water and the starting and sliding mechanism caused by seepage are revealed. The research finds that changes in seepage pressure and time are crucial in weakening the strength of sliding zone soil. Once it reaches the critical strength, seepage causes pressure shear failure, leading to the initiation of the landslide, which progresses from local to overall failure. During the reservoir water level rise and fall process, the hysteresis of pore water pressure in the slope body is evident, and the rate of water level change affects the response time of groundwater in the slope. A faster rate of water level change leads to a greater change in pore water pressure, more driving force from seepage, and a faster change in landslide stability and a closer approach to progressive failure. When the reservoir water level drops from 175 m to 145 m, the normal stress on the sliding surface of the Liangshuijing landslide decreases by 38.19%, and the shear stress decreases by 22.20%. The maximum decrease in the effective normal stress is 168.64 kPa and the maximum decrease in shear strength is 63.45 kPa. The above findings provide a scientific basis and theoretical methods for the analysis of landslide initiation and sliding mechanisms, instability research of reservoir bank landslides, and emergency prevention and control engineering.