Abstract: Variation of reservoir water level plays a crucial role in triggering and controlling the stability problem of reservoir bank slope. In the present research, the influence of cyclic variation of reservoir water level on a slope deformation is analyzed. Located in the Three Gorges Reservoir area, Bojishi landslide is affected by cyclical water level variation. Compared with smooth water surface, water level fluctuation is much more erosive to the toe of the landslide and leads to more complex slope deformation. According to field investigation result, the shear strain and sliding displacement of the landslide mass during reservoir water level fluctuation are analyzed by coupled hydro-mechanical module FLAC^3Dsoftware. Results reveal that water level variation has no obvious influence on shear strain increment, but leads to more concentrated strain increment than that before impoundment. Moreover, after impoundment, the sliding displacement, which increases with the drawdown of water level and alleviates with the rising of water level, will keep increasing when water level reaches a certain value.

Key words: Bojishi landslide, water level variation, FLAC^3Dsoftware, landslide deformation, shear strain increment