Stability of Liangshuijing landslide under variation water levels of Three Gorges Reservoir

Three Gorges Reservoir area of Yangtze River in China is a geological disaster-prone zone with frequent landslides. Liangshuijing landslide in Yunyang County in this area is just a case. The impoundment water level of Three Gorges Reservoir was 135m in 2003, 156m in 2006 and reached 175m in 2009. The effect of such a large variation of reservoir level on the deformation and stability of Liangshuijing landslide is not negligible. It once suffered from a dangerous situation due to the influences of various factors such as water level variation and rainfall. Based on the geological exploration, a thorough analysis of the deformation status and geological engineering situation of Liangshuijing landslide is made, and the formation and instability mode of the landslide are also judged. Based on the limit equilibrium analysis method, the stability of axial profile of the landslide is studied under three kinds of extreme conditions (impoundment water level of 145, 175m and drawdown of 175-145m). Three-dimensional finite element numerical calculation is then adopted to study the deformation of the landslide under the above conditions based on the hydro-mechanical coupling numerical model. The quantitative calculations reveal that the variation of groundwater level caused by the variation of reservoir level is the main factor for the landslide resurrection, especially under the third condition of rapid drawdown. It is recommended to continue monitoring the landslide so as to further understand the deformation trend of the landslide under the influences of water storage.