For a nuclear power and water tunnel project

a large-scale three-dimensional finite difference Flac3D model is established to simulate the seismic response under the action of seismic waves schedule in tunnel portal section

adopting nonlinear dynamic analysis method. Simultaneously

two-dimensional finite element model of backfill high-slope is created for slope stability analysis of tunnel entrance under the action of earthquake ground motion to draw the sliding surface of slope position and dynamic time history curve of safety coefficient. Through the input of the site seismic wave and the investigation of the structure response characteristics of the tunnel entrance and slope

duration curve of tunnel lining force under seismic waves action and tunnel lining figure can be obtained. Meanwhile

high slope safety factor of tunnel can be given. The analytical results show that the seismic weak parts of the tunnel entrance are at tunnel spandrel and the sidewall. The analytical method and conclusions have a certain reference value for the seismic design of tunnels.