Seismic Vulnerability Analysis Of Tunnel Lining Based On The IDA Method

With the increasing number of highway tunnels in China,how to reasonably predict the damage degree of tunnels under the possible earthquake in the future is one of the urgent problems to be solved in tunnel disaster control.Based on the actual tunnel seismic damage and the existing tunnel damage evaluation methods,the paper gives the tunnel performance index,and establishes the tunnel damage evaluation system.Then the influence of different earthquake action and parameters of ground motion intensity on the seismic response of tunnels is discussed by IDA analysis method.In addition,the probability of different damage degree of tunnels under different earthquake action is analyzed by vulnerability analysis theory.The above research results could be used as a reference for pre-earthquake disaster prediction and post-earthquake loss assessment of highway tunnels in seismic fortification areas.According to the existing methods of tunnel damage evaluation,it is not easy to quantify the seismic damage of tunnels when evaluating the seismic damage of tunnels.The deformation rate of tunnel diameter is taken as the performance index of tunnels by summarizing the common failure modes and analyzing the damage mechanism of tunnels.Based on these,the damage degree of tunnel lining is divided into four performance levels,and the damage evaluation body of tunnels under earthquake is established.It provides theoretical basis for IDA analysis and vulnerability analysis of tunnels under earthquake.Aiming at the fact that the common seismic analysis methods of tunnels can not reflect the whole process from cracking to destruction of tunnels under earthquake action,this paper takes a tunnel as an engineering example for analyzing the response law of tunnels under different seismic waves with IDA method.In the process of numerical calculation,the deformation rate of tunnel diameter is be used to measure the damage degree of tunnels as an index.And the validity of vibration intensity parameters is discussed.With the increase of ground motion intensity,the diameter deformation rate of tunnel increases linearly at first,and then its growth accelerated.When different parameters of ground motion intensity are selected,the tunnel IDA curves have similar trends.However the IDA results obtained by using PGA as ground motion intensity parameter are more effective than those obtained by using PGA and Sa.Based on the tunnel damage evaluation system and a large number of IDA analysis results,the probability of tunnel lining damage reaching different performance levels under different intensity earthquake is analyzed by vulnerability analysis theory with the help of statistical method.Then the vulnerability curve is given.At different performance levels,the vulnerability curves of tunnels are “S” shaped when the seismic intensity increases gradually.And the overall slope of tunnel vulnerability curve tends to decrease with the improvement of tunnel performance level.With the increase of seismic fortification intensity,the intersection points of coordinate axes corresponding to different seismic fortification intensity and vulnerability curves gradually shift from performance level I and II to performance level II,III and IV.At the same time,the probability value of intersection points gradually increases.