Seismic Response Analysis Of Large Diameter Shield Tunnel Considering Joint Nonlinearity

With the rapid development of China's economy and the increasing population,subway-based underground rail transit has gradually become the first choice for people to travel,and a large number of shield tunnels that have been built and to be built in China are located in high earthquake areas.Facing a serious threat of earthquake damage.Therefore,it is very necessary and meaningful to analyze the seismic response of shield tunnel.In this thesis,the response of shield tunnel under earthquake is studied and analyzed systematically by using the method of numerical simulation.The specific work is as follows:In this thesis,firstly,the seismic response of the free site is analyzed,the law of the seismic response of the free site is studied,and the corrected velocity-displacement curve is obtained,which provides a reliable input for the seismic response calculation of the subsequent tunnel structure.Then,based on the beam-spring model,considering the non-linearity of the joint and concrete,the fiber beam-nonlinear joint model is established,and the bending moment-rotation curve and the opening height of the joint under different initial conditions are calculated.The nonlinear stiffness of each joint in the cross section of a typical section of a practical project is obtained by iterative calculation.After that,three kinds of cross-section models are established,and the seismic response is analyzed by the response displacement method,and the effects of the existence of the joint on the axial force,shear force,bending moment and the stiffness of the joint on the rotation angle of the joint are compared.Based on the idea of response displacement method,the Pushover analysis method of underground structure is proposed,and the dynamic response of shield tunnel under earthquake until structural failure isobtained by finite element calculation.Finally,taking the opening amount of the joint as the failure index,the vulnerability curve of the tunnel based on the opening amount of the joint is obtained,and compared with the vulnerability curve based on the section bearing capacity,it is found that when the seismic strength is small,the section failure is the main one.When the earthquake intensity is very large,the joint has a greater probability of serious damage.