Dagangshan Hydroelectric Power Station is a large-scale hydroelectric power station developed recently in the main stream of Dadu River. According to the complex geological structures of Dagangshan arch dam，the stabilities of the dam abutment was studied by the comprehensive method of 3D geomechanical model test. Considering both factors of overloading and strength-decreasing, the failure model test was carried out. The deformation character of arch dam abutment was studied, the failure process and final failure pattern of dam abutment and foundation were obtained, and the comprehensive safety factor of dam abutment was determined as 5.0~5.6.
