Characteristics and mechanism of spatio-temporal difference deformation of Zengjiapeng landslide

It is of great significance to understand the evolution of the landslide in the Three Gorges Reservoir area. This paper studies the landslide deformation characteristics under the influence of reservoir water level fluctuation and rainfall and analyzes its failure mechanism. According to the GPS surface displacement monitoring data, the deformation characteristics of the landslide at different water level operation stages are detailed analyzed. Then, the grey correlation model is used to identify the main controlling factors of landslides displacement of different parts at different water level operation stages. Finally, GEO-Studio software was used to simulate the stability variation of Zengjiapeng landslide under the coupling effect of historical rainfall and reservoir water level fluctuation. The cross-check with quantitative analysis shows that: The kinematic state of Zengjiapeng landslide is time-varying, changes from slow creep state to step-like deformation state. In surface, more intense movement is observed in the east-central part of the slope than in the west part. In profile, the deformation is initiated in the front part, and then extends to the trailing part. The deformation and instability process are determined: the Zengjiapeng ancient landslide was first activated by the initial impoundment, and the leading edge deformed at first. Rainfall, as the main controlling factor in the middle and late stage, coupled with the fluctuation of reservoir water level and induced multiple step-like deformations of the landslide. Hence, a series of penetrating cracks are formed in the whole body of the landslide. Eventually, the overall failure was triggered by a strong rainfall once in 20 years.