Longitudinal Seismic Vulnerability Analysis Of Shield Tunnel

In recent years,shield tunnels have developing rapidly in our country,but our country is also a country with frequent earthquakes,once a strong earthquake occurs,the shield tunnel will be seriously damaged.Therefore,it is necessary to study the damage degree of shield tunnel under earthquake.Based on a subsea shield tunnel in Guangdong Province,through the establishment of finite element model and use IDA analysis method,stude the seismic response of the tunnel under different ground motions,at the same time,the seismic vulnerability method is used to evaluate the damage probability of shield tunnel under different ground motion intensity.The main contents of this paper are as follows:(1)Firstly,summarize the common analysis methods and models of longitudinal seismic resistance of shield tunnel,and compare their advantages and disadvantages,applicable conditions,and select the generalized response displacement model and beam spring model which are suitable for this paper;Secondly,use ABAQUS finite element software to establish a two-dimensional free field numerical analysis model of subsea shield tunnel,including element type selection,mesh generation,artificial boundary setting and soil dynamic constitutive model;Finally,based on the generalized response displacement method,the longitudinal refined beam spring model of the tunnel is established,and the spring stiffness parameters of the tunnel ring joint and the foundation spring parameters are given,which lays a theoretical foundation for the subsequent longitudinal seismic response analysis.(2)In order to evaluate the damage degree of shield tunnel under different earthquake intensity.Firstly,introduce the basic principle of IDA in detail;Secondly,select the peak ground acceleration as the ground motion intensity parameter,and use the opening between longitudinal rings of the tunnel as the performance index,according to the different values of the opening between longitudinal rings of the tunnel,put forward the grading evaluation standard,and based on the actual site environment,select seven typical seismic waves for the analysis in this paper;Then,compare and analyze the displacement time histories of different observation points along the longitudinal position of the shield tunnel under four working conditions,and put forward them,the displacement time histories are applied to the soil spring model in the form of forced displacement load to analyze the seismic performance,and finally extract the longitudinal ring opening of the shield tunnel.Finally,the IDA analysis method is used to calculate the amplitude of each seismic wave according to the above steps.Finally,the IDA curve of the shield tunnel is drawn with the extreme value of the opening between the longitudinal rings of the shield tunnel as the abscissa and the ground motion intensity PGA as the ordinate,and the curve is analyzed.(3)According to the IDA analysis results and the shield tunnel damage evaluation system,through the vulnerability analysis theory,the performance level probability of the subsea shield tunnel under different ground motions is analyzed,and the vulnerability curve is drawn,so that the damage state of the shield tunnel under earthquake can be judged from the perspective of probability.