Abstract：According to the principles of static forces for designing and dynamic forces for checking，3D critical block theory is used to identify and describe all removable blocks based on the geological exploration data. Then the corresponding dominative sliding blocks are determined. For the 3D features of the abutment stability problem，the program of 3D rigid body limit equilibrium method is developed to compute and analyze the sliding resistance stability of high arch dam abutments of a hydropower station，nearly 300 m in height，under static and dynamic loadings with several different elevation planes. In dynamic analysis method，the arch dam，reservoir water body and dam foundation are regarded as an integrated system，so that the dynamic interaction between the blocks and dam body can be effectively considered. The results obtained by the method integrating static and dynamic loadings indicate that the arch dam abutments of both sides are stable under static loading with enough margin of safe. While under the action of earthquake，the dam is safe though the factor of safety is not very high. All of these provide significant scientific bases for design and demonstration of high arch dam.
