Effects Of Reservoir Level Fluctuations On Reactivation Of Landslide In Reservoir Area

Reservoir landslide is a severe geological hazard which is caused by the hydrodynamic change due to rainfall and fluctuation of reservoir level. More than 70% of reservoir landslides are the reactivation of old landslides. Numerical analysis of the reviving mechanism of old landslide is important to the forecasting and reinforceing of reservoir landslide.In this paper, the Xietan landslide in the Three Georges Reservoir area is as a case for research. At first, a comprehensive monitoring system was implemented in Xietan landslide based on detailed geological investigate. Through 4 years'monitoring and analyzing, hydrodynamic and deformating responding of landslide under the condition of rainfall and riseing of reservoir water was carried out, and geological model of Xietan landslide was justed and abstracted. Then, unsaturated hydraulics parameters and mechanical parameters of every stratum were tested. Finite element model for saturated-unsaturated seepage computing was established and permeability coefficient of landslide was carried out through back analyseing with BP neural network and Genetic Algorithms. At last, the limit equilibrium method and finite element method of landslide stability under seepage was discussed, and the hydrodynamic evolvement and deformation mechanism of landslide under fluctuation of reservoir level was analysed.Conclusions drawn from the research can be summarized as follow.1. Sufficient data including deformation, groundwater leve, pore water pressure, rainfall precipitation, reservoir water level of the landslide in the pre-impoundment, the first impoundment to 139m of the reservoir and the subsequent fluctuations was achieved through 4 years'monitoring. The data is useful for study the reviving mechanism of old landslide in reservoir area.2. In monitoring period, the effect of rainfall on landslide deformation is negligible; reservoir impoundment is the main causation of reactivation. Deformation score is limited in the middle-front region of landslide. The stabilization effect of the reverse seepage during reservoir filling is temporary and limited.3. The unsaturated hydraulic parameters of gravelly soil are difficult to determine due to its high gravel content and large grain size. In this paper, the soil-water characteristic curve and saturated permeability coefficient was determined...