Effect of Seismic Frequency Spectra on Surrounding Rock Damage Evolution of Large Underground Caverns

To explore the distribution and evolution of the surrounding rock of underground caverns of hydropower stations, the dynamic compression tests for granite sample were carried out and the dynamic constitutive relation suitable to computer programming was established in terms of strain-based static elastic-plastic damage constitutive relation. By inputting five earthquakes of various frequency spectra, the fully nonlinear dynamic analysis was performed for some large underground caverns in the gorge and mountain region in Sichuan Province in China with the explicit difference method. The simulation results show that, as the input seismic waves become strong gradually, the damage zone generally extends deeply from the middle of side walls. The damage zone reaches the maximum value in areas immediately after the seismic acceleration peak arrives and keeps constant thereafter. According to the initial analysis, if the dominant frequency of input wave approaches the natural frequency of underground caverns, the maximum area of damage zone will increase. Those findings may provide practical data for earthquake-resistant design and construction.