Influence Analysis Of Surface Structure On Seismic Response Of Underground Station In Earth Fissure Environment

Earth fissures,as a special engineering geological hazard,destroy the integrity of the ground and enlarge the seismic response of the structures.In recent years,a large number of existing and proposed underground stations are affected by earth fissures,some of them even across the existing or secondary fissures.Meanwhile,the underground stations are often located near busy commercial or residential areas.Therefore,it is of great theoretical significance and engineering practical value to study the SSSI(structure-soilstructure interaction)system under earthquake.Firstly,the 3D finite element models of underground station-soil-surface structure interaction system in earth fissure environment were built based on the actual project.The boundary condition,which was defined as visco-elastic artificial boundary,was verified by the seismic response of measuring point in boundary.Then,the seismic responses of earth fissure ground were compared with the test results,showing the same tendency and verifying the reliability of FEM model.Secondly,different conditions of SSSI system were established,which included the different parameters of soil and surface structure.Based on the acceleration amplification factors of side wall and column in the underground station,it shows that the existence of earth fissure and surface structure both increases the seismic response of underground station.With the increasing of floor number of structure,the decreasing of shear modulus and damping ratio,the dynamic response of underground station increases and the existence of earth fissure enlarages the amplification effect of other parameters.Thirdly,according to the most disadvantageous condition,the refined model of SSSI system with solid element of structures in earth fissure environment under earthquake was established and analyzed.It presents that underground station in earth fissure environment is mainly shown lateral and vertical shear deformation,and the underground station is destroyed and loss its bearing capacity due to the P-(35)effect of the column under earthquake.Meanwhile,the seismic response and hysteresis energy of underground station in hanging wall is larger than these in the foot wall due to the influence of earth fissure and the self-gravity of surface structure.Thus,the column in hanging wall is vital to the safety of underground station.