Study On Seismic Response Of Metro Tunnel Adjacent To Ground Fissure Zone

Since the 1950 s,there have been 14 ground fissures crossing the urban area in Xi'an,covering the total area over 250km~2,which poses a serious threat to the urban construction in Xi'an.Meanwhile,Xi'an locates in the highly intensity seismic area and the seismic fortification of urban construction has to be mainly considered.Urban metro system belongs to the important lifeline engineering and once suffers earthquake damage,it will bring serious harm to the life and property of people.The emergency treatment and post-earthquake restoration is extremely difficult.The seismic response of the metro tunnel in the development area of ground fissure with highly earthquake intensity has become a hot issue of seismic resistance of the urban lifeline engineering.So it is of great practical significance and engineering value to study the seismic response of metro tunnel crossing ground fissure site.Taking Xi'an metro tunnel crossing ground fissure site as main research object,with the method of large-scale shaking table model test and dynamic numerical simulation of FLAC3 D,the seismic response characteristics of metro tunnel adjacent to ground fissure zone are systematically studied.The major research results of this dissertation are as follows:(1)Based on similarity theory,the generalized model is established.The shaking table model test of metro tunnel adjacent to ground fissure is carried out firstly.Combined with the numerical simulation,the seismic response characteristics of metro tunnel adjacent to ground fissure zone under the action of seismic ground motion are revealed,including the deformation and failure characteristic of the ground,the acceleration response rules of site and tunnel structure,frequency domain variation of site,as well as the strain response of the tunnel structure.The influence law of ground fissure on the seismic response of metro tunnel and the site is obtained.(2)Through the numerical software of FLAC3 D,based on the typical stratum structure of Xi'an,the dynamic analysis models of ground fissure site and ground fissure site with tunnel are established,and the seismic response of metro tunnel adjacent to ground fissure zone is simulated.The results show that the surface acceleration response of two sites are both the strongest near ground fissure,with a significant amplification effect,and it gradually decreases from the ground fissure to two sides of hanging wall and footwall.The earthquake influence scope of ground fissure site is respectively 32 m or 13 m in the hanging wall or footwall.The earthquake influence scope of ground fissure site with tunnel is respectively 15 m or 13 m in the hanging wall or footwall.The PGA magnification coefficient of the hanging wall is larger than that of the footwall,showing obvious magnification effect of the hanging wall.The dynamic earth pressure of ground fissure site is larger near the ground fissure and gradually decreases toward two sides of hanging wall and footwall.The dynamic earth pressure variation law of ground fissure site with tunnel is basically the same as ground fissure site near the ground fissure,but its dynamic earth pressure near the tunnel structure is significantly increased.