The influence of water on the occurrence of Qianjiangping landslide

Qianjiangping landslide was the first catastrophic landslide occurred in the reservoir area of the Three Gorges dam after its impoundment.Following analyzing characteristics of the landslide,variation of its factor of safety(F_s) under the influence of both rise of reservoir water level and durative rainfall was investigated in this paper using sensitive analysis with a consideration of a series effects of water on the landslide,such as: weakening of shear strength of the landslide’s slip zone,increasing unit weight of the landslide materials,imposing a uplift water pressure on the landslide,and rising groundwater table.It was found among these effects,weakening of shear strength of the lower section of the landslide’s slip zone,which developed crossing bedding planes of mudstone,had the strongest influence on the landslide’s stability,followed by those of uplift water pressure,weakening of shear strength of the slip zone’s upper section along the bedding plane of shale,increasing of unit weight of landslide’s materials,whereas rising of groundwater table had little influence on the landslide.Results of this study showed that occurrence of Qianjiangping landslide was a consequence of combined influence of impoundment of Three Gorges’ dam and durative rainfall.However,it seems that influence of the former was much greater that the latter.