Elementary Seismic Analysis Of Underground Hydropower Cavern Groups

Along with the strategy of Development of Western Areas in China, a lot of large scale hydraulic power plants will be or have been constructed in areas which are seismically active zones with high earthquake intensity. Due to complexity of geological conditions, most of these power plants are designed to be in underground caverns. Therefore, how to evaluate the safety of the cavern groups when subjected to the earthquake is an important task that engineers should have to face. This paper aims to perform dynamic analysis for these underground caverns excited by earthquakes. The research is supported by the National Natural Science Foundation of China (50809013) and China Institute of Water Resources and Hydropower Research (IWHRO2009019).The rational setup of artificial boundary is a very important problem in dynamic analysis of underground structures, which directly relates to the accuracy and credibility of the calculation results. The codes in Parametric Design Language (APDL), for realization of Multi-order Transmitting Boundary (MTB) and Viscous-Spring Boundary (VSB) with corresponding seismic input methods, are programmed and conveniently linked with general software platform ANSYS. Then the programmed methods and codes are applied to seismic analysis of underground hydropower caverns in time domain. The analyses are performed on a 2-D plane strain model and a 3-D model respectively. And in 2-D analysis, effects of local topography and incident directions of seismic wave on responses of underground caverns are considered. Some seismic response characteristics of underground caverns are then summarized.