Unsaturated seepage analysis for a reservoir landslide during impounding

摘要

Xietan landslide is a pre-existing landslide in the Three Gorges Reservoir area and is constitutedof the slide body,the slip zone,the sliding-disturbed zone,and the bedrock from up to down. In hydrogeology,theslide body,the slip zone and the sliding-disturbed zone can be regarded as porous continuous medium,while thepermeable bedrock is fractured rock. In this paper,an equivalent continuum model was used to model all strata,and a finite element model was established to analyze the unsaturated seepage of Xietan landslide. Then the back-propagation neural network was used to substitute finite element seepage analysis. The saturated permeabilitycoefficient of every stratum was optimized by genetic algorithm based on monitored data during reservoirimpounding. The saturated permeability coefficient of the slide body by back analysis is 4.89×10-2cm/s,which is consistent with field testing results (1.78×10-2cm/s to 3.2×10-2cm/s); the saturated permeabilitycoefficient of the slip zone by back analysis is 4.66×10-5cm/s,which is very larger than indoor testing results(2.74×10-7cm/s to 5.73×10-7cm/s). The scale effect of soil samples was reflected by this difference.