Seismic Response Analysis Of Underground Structures And Its Influence On Ground Surface

All sorts of underground structures have been developed rapidly in the transportation, water conservation, national defense and other fields.especially city subway, has received its fastigium completely. China is a seismic active country, and with the increase in the number of underground structures, the possibility that it is subjected to earthquake damage is higher and higher. in the2008Wenchuan earthquake,the Longxi tunnel,small-Tianzhu subway station,as well as a large number of tunnels on the Duhan Highway and State Road213etc have been damaged in varying degrees.the subway has become an important part of urban lifetime in China and the cost is prodigious.once Earthquake occurs,it will result in direct economic losses and secondary disasters,there is an extremely important political, economic and military significance.therefore,it need higher requirements for construction, use and safe of anti-seismic.and compared with the ground structures,the information of earthquake damage of underground structures is comparatively little,therefore, anti-seismic of subway structures is important both in theoretical research and engineering.Adopting the method of finite elements coupled infinite elements, The seismic response of free field,subway station structure and ground surface after subway excavated is compared with the corresponding response before excavation was studied using three-dimensional large deformation FEM model.and effect of ground structure-soil-underground structure dynamic interaction was considered. The major studies are as follows:(1) Firstly, the seismic response analysis of the free site is performed subjected to different seismic waves, and response results of free site are given, the results include horizontal acceleration, relative displacement and response spectrum. The characteristics and laws of free field seismic response are summarized. Secondly, the influence of the factors on the acceleration amplification effect of soil is looked into, which include Peak acceleration, free-field size of the soil and the soil stiffness.Finally, In the case of building the subway structure and free site, the horizontal relative displacement and acceleration responses of ground surface has been done a comparative analysis briefly.(2)The seismic response of shallow-buried subway station structure was studied, the changing of column moment along lognitudinal direction of station, the internal force growth of the station structure components caused by seismic loads and the horizontal relative displacement and acceleration responses of subway station structure subjected to different seismic waves are performed, the characteristics and laws of subway station seismic response are summarized. additionally, it focus on that the influence of the vertical seismic ground motion on the displacement response, acceleration responses and the maximum stress of subway station structure, the horizontal distortion, axial force, bending moment and shear force of the station column. as well as the influence of soil stiffness and structural stiffness on the relative displacement of the subway station. the results can provide a useful guide for the Seismic design of the subway station structure.(3) In the case of ground structure, a systematic study was conducted on that the relative horizontal displacement and the acceleration of ground surface after subway excavated is compared with the corresponding response before excavation, given the influence of the excavation for underground subway station on the ground surface considering the presence of the ground structure. finally, effect of the factors to seismic response of ground surface is also looked into, which include the size of ground building, soil stiffness, relative distance and the ground structure stiffness, and it is can reflect the actual situation better compared with only considering the influence of underground structures on ground surface seismic response analysis.