Abstract: The global stability of Wudongde double-curvature arch dam is researched by using 3-D geomechanical model in overloading condition. The mechanics behaviors and complex geological structures including discontinuous planes and beddings of dam foundation and abutment are simulated with a model of 1∶300 scale. Through the overloading model test, the deformation characters, failure process, failure pattern and overloading capacity of arch dam are obtained, and the global safety of arch dam and dam foundation is assessed. Furthermore, the displacement fields under normal water-storage level condition and overloading condition are analyzed, relative displacements at typical points on the beddings are obtained, and crack development before and after the failure are described. Results indicate that under design load, the arch dam body and abutments on both sides are stable and the deformation is linear; the overloading factor k₁ for crack initiation in dam heel ranges from 1.7 to 2.0, the nonlinear deformation overloading factor k₂=3.5~4.0, and the ultimate overloading factor k₃=6.0~7.0.

Key words: Wudongde hydroelectric power station, global stability of arch dam, 3D geomechanical model, overloading test