Simulation Of Damage-Collapse Process And Safety Evaluation For Arch Dams

On the basis of 3-D Mode Distinct Element Method (3MDEM) by Zhang Chong, the linear elastic constitutive relationship of blocks is extended to elasto-plastic. 3MDEM with elasto-plastic is used to simulate the failure process of Meihua arch dam and failure mechanism is studied. Because of the limitations on mass computation of 3MDEM, a procedure of comparative study for safety evaluation of high arch dams is carried out by the nonlinear finite element method (FEM) based on the failure mechanism. Xiaowan arch dam is studied with the comparative projects. The main contents are summarized as follows:1. The groundwork and computational procedure of 3MDEM are introduced at first. 3MDEM is a distinct element method under the assumption of a small strain, finite displacement, and finite rotation for blocks. The deformation of blocks is expressed by a combination of deformation modes in 3MDEM. Then the elasto-plastic constitutive relationship of blocks is investigated through continuum to discontinuum simulation, including Mises and Drucker-Prager model. Due to the shortcomings of the common criterion for contact fracture, a new criterion based on plastic strain is introduced. A failure process from elastic, elasto-plastic to fracture can be simulated on the 3MDEM platform. This is verified by several numerical examples comparing with FEM.2. 3MDEM with elasto-plastic properties is used in failure simulation of Meihua arch dam. The failure mechanism is studied through the crack expanding process. It turns out that the instability of upward sliding of dam is the cause of the failure. Arch dam is a high-order statically indeterminate structure with bearing capacity of arch and cantilever structure. 3 stages are usually involved in the failure process of arch dam:The cantilever failure stage: the failure first occurs at cantilever structure; the arch failure stage: when cantilever structure is weakened, a great many load moves to arch structure especially the middle-up arch, then the middle-up arch damages rapidly; the whole arch dam failure stage: when applied load is continued, most of the dam is damaged, which leads to dam burst at last.3. Based on the failure mechanism studied by 3MDEM, a procedure of comparative study for safety evaluation of high arch dams is carried out by FEM. A set of safety factors for dam heel crack and ultimate bearing capacity is suggested: safety factor for curtain k1, structural mutation safety factor k2, and ultimate safety factor k3. The safety evaluation of Xiaowan arch dam is studied based on engineering analogical method, chosing K?lnbrein and Ertan as comparative projects.4. Firstly the numerical results of Xiaowan are compared with geomechamical model test results. Secondly, the strengthen measurement of Xiaowan project is studied, and the the thermal cracks of dambody is simulated to discuss the influence for dam security. Finally, softening behaviors of concrete material are involved approximatively to give a full-scale safety evaluation of Xiaowan arch dam.