Studies On Seismic Fracture Problems In Gravity Dams Based On Polygon Scaled Boundary Finite Elements

Concrete gravity dams have a simple structure, and can adapt easily to geological conditions. It’s one of the most main dam types for the hydroelectric construction. As the change of temperature in dam body or uneven deformation of foundation, the dams work with cracks usually. Whether the cracks are stable has important influence on the safety of the dam when the dam suffers from earthquake or other extreme loads. Based on the Polygon scaled boundary finite element method (Polygon SBFEM), a numerical model for seismic crack propagation in gravity dam is developed. The contents include the following aspects:(1) The singular stress field and displacement field in the vicinity of a crack tip are obtained semi-analytically. The stress intensity factors can be obtained accurately and easily by using the method which has been proved. However, remeshing technology still was a difficulty point in the crack propagation study. By introducing the polygon element scheme, it becomes flexible and convenient to discrete the irregular structures. At the same time, local remeshing technology that introduces minimum change to the global mesh is involved. Polygon SBFEM and local remeshing technology make it flexible and convenient to predict the crack propagation.(2) Through the numerical simulation of Koyna dam subjected to reservoir overflow, it was found that different mesh densities and crack propagation lengths led to consistent results. The predicted crack trajectories and the structural responses show a good agreement with other numerical simulations reported in the literature, which demonstrates the effectiveness of the model.(3) In the simulation of the dynamic crack propagation, the load varies with time and fracture toughness varies with crack propagation velocity. The dynamic crack propagation of a three-point-bending beam subjected to impacted loading is simulation. At present, the variation rule of concrete’s dynamic fracture toughness has not been unified. Therefore, in the simulation on the seismic crack propagation of Koyna, the dynamic fracture toughness is regarded as a constant. In this paper, the regulations of crack propagation path, stress intensity factor and displacement change following time are shown.