Abstract：As faults，inner layers and interlayer shear bands widely develop in the left dam abutment of Baihetan Hydropower Station，and the fault F33 directly conjoins with the left dam abutment，so，shear deformation easily occurs under the thrust of arch dam. The mechanical indexes of dam foundation such as deformation modulus are relatively small and the anisotropy of dam foundation is obvious due to the development of columnar joints layers. In order to reduce the influence of these geological defects，some engineering measures are taken when designing，such as setting anti-shear tunnel along the direction of arch thrust，the cushion to the rock mass of dam foundation，etc.. These measures will improve the shear and transmission force mode of abutment and foundation to some extent. 3D nonlinear numerical method is applied and 3D numerical model based on geological information is built to simulate certain geological phenomena and related engineering measures in middle dam site of Baihetan Hydropower Station. The safety degree of the downstream dam line is evaluated by overloading method，strength reduction method and point safety factor method. The results obtained by these methods will play a role of support to technical basis and scientific research achievements for choosing dam line.
