Discussion on seismic calculation methods of underground structure of hydropower station

According to numerous in-situ investigations of earthquake disasters, it is widely regarded that underground structure is of key significance for seismic design of underground cavern. Since no specified simulation methods are definitely issued in the specifications for seismic design of hydraulic structures in China, three common seismic calculation methods of underground structure including quasi-static analysis method, response spectrum method and time-history method are discussed. Numerical calculation are conducted using these methods for underground powerhouse structures of Yingxiuwan hydropower station under Wenchuan earthquake; and calculation results are analyzed based on the in-situ investigation of earthquake disasters. The results show that three methods can reflect the dynamic failure of underground structures to some extent and provide a theoretical basis for the seismic design. It is also shown that the calculation results of the quasi-static analysis method is prior to more safer design and unreasonable for simulating top arch and corbel; response spectrum method can estimate weak parts of structure, but not exactly in interaction analysis of concrete structure and surrounding rock; time-history method is able to precisely simulate the seismic response process under the earthquake disaster; and calculation result is best consistent with in-situ investigation of earthquake disasters, which is better for precise and economic engineering design. Time-history method is suggested to be used for dynamic calculation for the underground powerhouse of high level security, large-scale or in high seismic intensity region.