Study On The Method Of Determining Seismic Stability Of Tunnels

Most of China’s cities are located in high intensity areas with seven or more earthquakes with strong earthquakes.With the large-scale construction of the city,tunnels in high-intensity earthquake zones are increasing,and the seismic problem of tunnel is getting more and more attention.Wenchuan earthquake and Qinghai Yushu earthquake caused many tunnels to damage,so it is necessary to research the tunnel seismic stability.However,there are still many problems in the seismic research of tunnels.Among them,the method of tunnel seismic stability is a problem to be solved and needs further study.In this paper,through the theoretical analysis and numerical simulation,the method of determining the seismic stability of the tunnel is analyzed.The main contents and achievements are as follows:(1)Summarize and analyse the existing methods to determine the seismic stability of tunnels;(2)Based on the constitutive relation,artificial boundary,model damping and seismic wave analysis,the model parameters of the calculation are determined.(3)From the perspectives of static analysis and dynamic analysis,the influence of the construction stage on the stress state of the tunnel is compared.The results show that the tunnel stress state is more consistent with the actual after considering the construction phase.Therefore,the initial stress field analysis before tunnel seismic analysis takes into account the construction phase.(4)The existing two methods for determining the seismic stability of tunnels are analysed including the plastic zone of plasticity-plastic shear strain increment method and lining stress state method.The results show that the plastic zone-plastic shear strain increment method has some shortcomings to determine the stability of the tunnels.There is a certain limitation on the stability of the tunnels by the stress state method.(5)The tunnelling feature point displacement difference method is proposed,which is to determine the stability of the tunnel through the change of the horizontal displacement difference of the tunnel feature point.According to the change of the horizontal displacement difference of the feature points,it can be determined whether the tunnel is in elastic deformation,plastic deformation or complete failure stage under the action of different peak acceleration seismic waves.Finally,by applying different types of seismic waves to verify the accuracy of the law.