Study on seismic dynamic response rules of tunnel portal

In this paper three-dimensional seismic dynamic responses of tunnel portal are modeled by FLAC. Seismic response rules of tunnel lining and rock mass are acquired from calculating. Some conclusions are presented as follows:(A) Rules of Displacement: the displacement peak obviously lags behind earthquake action, that means that the displacement values caused by seismic dynamic response will come to maximize after the maximum acceleration caused by earthquake action;(B) Rules of Stress: the maximal displacement values increase with depth-span ratio, and then barely grow when depth-span ratio reaches a certain value;(C) Rules of Plastic Zone: Plastic zone are remarkable developed around the surrounding of tunnels. For tunnel structures, Plastic zone grow apparently nearby their left-hance~ vault~right-hance, and inverted arch.