Numerical Simulation of Failure Process of the Qianjiangping Landslide Triggered by Water Level Rise and Rainfall in the Three Gorges Reservoir, China

Abstract

The Qianjiangping landslide is a large translational rock slide which occurred in July 14, 2003 shortly after the water level reached 135 m in the Three Gorges Reservoir, China. The landslide destroyed 346 houses, took 24 lives and rendered 1,200 people homeless. In order to understand the failure process of the landslide, numerical simulation was conducted on Qianjiangping slope before sliding. Based on pre-failure characteristics and structural conditions of the landslide, topographic and geological profile of Qianjiangping slope was reconstructed. Seepage field of the Qianjiangping slope before sliding was simulated with the SEEP/W module of GeoStudio software. The results show that the groundwater table rose and infiltrated into the slope during the rise in water level, and the slope surface became partially saturated during the period of continuous rainfall. Using the groundwater table data, the failure process of the Qianjiangping slope was simulated with Flac3D software. The result shows that the shear strain increment, displacement and plastic state region of the slope increased greatly after water level rise and continuous rainfall. Consequently, the landslide was triggered by the combined effects of water level rise and rainfall. The simulated results of the shear strain increment, displacement and plastic state region of the slope show that the failure surface was located in the weak carbonaceous shale layer, and was retrogressive in the lower part of the slope and progressive in the upper part. Analysis of the simulation results before and after the water level rise and rainfall, it was observed that reservoir water level rise was the main triggering factor for the Qianjiangping landslide.