Seismic performance of a large underground cavern at different excitation direction

Underground infrastructures can be adversely affected by earthquake-induced rock engineering vibration causing damage problems. These impacts are even more significantly affected for large underground caverns due to the large span and complex structures. Currently, time-history numerical simulation is still the most popular method for seismic design of underground infrastructure, however it is based on the plane-strain model and assumes the vertical incidence of seismic waves. In fact, the propagation direction of seismic wave is arbitrary and the effect of excitation direction has not been understood well. In this paper, a 3D full-scale hydropower station is built by FLAC3D, and several sets of seismic waves based on the real earthquake motions are applied from different excitation direction. The results show that the wave excitation direction directly influences the result of the large underground cavern assessment, which is manifested by traditional vertical wave applied at bottom underestimating the response, especially for the cases of high lateral stress.