Abstract:Aiming at the engineering geological problems of the Dagangshan arch dam,by three-dimensional geomechanical model test,the whole failure process and mechanism of the arch dam and abutments from loading to failure are studied. The model simulates the discontinuous rock body of dam foundation,the mechanical properties of rock and the entire double curvature arch dam. The model considers the various factors influencing the stabilities of dam foundation and abutment during test,including overloading as well as strength-decreasing of weak structural planes in the rock mass of the dam foundation. A kind of model test material called temperature analogous material whose strength varies with temperature in the process of experiment is adopted to simulate the decrease of the weak structural planes. Then,the comprehensive method considering both overloading and strength-decreasing is successfully applied to the model. The displacement fields of arch dam under the pressure of normal pool level and overloading after strength-decreasing are obtained. The deformation characters of dam and abutment and relative displacements of internal fault for typical measurement points are obtained,and the overall developing process of displacement and crack before arch dam and foundation destabilization and its failure mechanism are revealed. The safety evaluation on the model experiment indicates that the strength reserve coefficient K1 and overloading coefficient K2 are 1.25 and 4.0–4.5 respectively,and the global safety factor for the dam foundation and abutment is 5.0–5.6. The slope stability can be evaluated by synthetically analyzing test data,and the reinforcing measures for the weak areas of dam abutment are advised.