Unsaturated seepage analysis and back analysis of permeability coefficient for Xietan landslide in Three Gorges Reservoir area

The hydrogeological structure of Xietan landslide is very complex;its slidebody,slipband and sliding-disturbed zone can be regarded as porous continuous medium,but its infiltrative bedrock is fractured.An equivalent continuum model is used to model fractured rock;and a finite element model of saturated-unsaturated seepage analysis of Xietan landslide is established.Then back-propagation neural network is used to substitute finite element seepage analysis;and saturated permeability coefficient of every stratum is optimized by genetic algorithm based on monitoring data during reservoir filling.The saturated permeability coefficient of slidebody by back analysis is 4.89×10-2 cm/s,which is consistent with field testing result(1.78×10?2 cm/s to 3.2×10?2 cm/s);the saturated permeability coefficient of slipband by back analysis is 4.66×10?5 cm/s,which is very larger than indoor testing result(2.74×10?7 cm/s to 5.73×10?7 cm/s).The scale effect of soil sample is reflected by this difference.