Research on the Impact of the Water-Level-Fluctuation Zone on Landslide Stability in the Three Gorges Reservoir Area

Taking the Lijiapo landslide in Three Gorges Area as an example, the study on the impact of seepage field changes caused by water level fluctuation on reservoir landslide stability was carried out. In order to find out the variation in slope stability when the reservoir water level changes at different rate, the stability calculation model was established adopting the Seep module and Slope module of Geoscience software GeoStudio, and calibrated with a long sequence of real-time monitoring data, based on the landslide survey data and test data. The results show that the reservoir landslide stability affected by the seepage field changes with changing reservoir level is controlled by a variety of factors, including the hydrodynamic pressure, hydrostatic pressure, uplift force, physical and mechanical properties (с, φ value change). When the water level fluctuates at a high rate, the impact of the seepage field changes on the stability is mainly affected by the pore water pressure before the stability reaches the extremum, while after the extremum, with the further infiltration or drainage of reservoir water, it is mainly affected by the change of physical and mechanical properties. When the water level fluctuates at a lower rate, the pore water pressure, uplift force and physical and mechanical properties are the dominant factors.