A kind of layer element with thickness and anisotropic hardening-softening character is adopted to simulate mechanics and deformation characteristic of soft interlayer in dam foundation. Contact friction element with no thickness is applied to simulating the joint in rock. Three-dimensional nonlinear finite element analysis is performed for slide resistance in deep foundation. Intensity safety factor is adopted to simulate gradual destroy progress and potential destabilization pattern. A judge method for limit load carrying capacity is presented

which synthesizes plastic zone pierce method

displacement jump of typical position and energy method. Then limit load carrying capacity of dam system is gained and slide resistance is evaluated. The finite element calculation results of actual project show that the limit load carrying capacity of dam system is decided by intensity of soft interlayer. Limit intensity safety factor is 2.7.