Study On Safety Of High Arch Dams With Complex Foundation

Along with the westward exploitation putting into practice, many high arch dams will be built in the southwest of China where water resources are rich. More and more arch dams are building on complex foundations. Safety evaluation is an important and complex research subject for high arch dam on complex foundations currently. Some primary researches are given in thispaper, combined with the project-stability evaluation of concrete high arch dam of Tengzigou,which is cooperated between Hydraulic Structure Center of Hohai University and Dongbei Hydroelectric Investigation & Design Ltd.Considering actual research work and specification, either concrete strength limit analysis of dam or shear failure of seams in rock abutments are taken singly into account for safety evaluation of high arch dam. They are inconsistent, Since the two types of failure usually effect each other, it is proposed that an arch dam should be appraised according to its whole working capacity.On the basis of 3D nonlinear finite element method, the stability of an high arch dam on the complex foundation is evaluated in two ways of overloading hydraulic pressure and reducing shear strengthes. Considering characteristic of different material zones of dam foundation in computation model, the compatible displacement method for incompatible mesh is presented in this paper, It is convenient for considering the interaction between the arch dam body and the dam abutment. Therefore, the mesh of dam body can be generated with 3D hexahedron elements but that of dam foundation is generated with 3D tetrahedron elements. Moreover, based on routine research method on abutment stability, non-linear finite element shear strengthes reducing by step iteration method is put forward in this paper, which is also applied in the analysis of abutment stability of Tengzigou arch dam successfully.As for high arch dams building on complex foundation, it is necessary to evaluate stability not only by 3D nonlinear finite element method but also by geomechanical model test method. In general ,both of them are used to verify the results. Using geomechanical model test method, the overloading process and wreck character of high arch dam was emulated completely for Tengzigou arch dam. It is emphasized for stabilization safety evaluation various major loading function of high arch dam must be accounted and arch dam's whole stability is the most important.Trough the analysis of stabilization safety on Tengzigou arch dam, some conclusions are obtained in the following: (1) Tengzigou arch dam is safe under normal poll level ; (2) stabilization safety factor of Tengzigou arch dam is about 4-5; (3) It is proved that combinatorial reinforcement measures are effective and feasible.