Research On The Deep And Shallow Burial Questions For Seismic Design Of Tunnel Under Earthquake

With the more and more number of underground engineering in China,it is inevitably that tunnels are built in the seismic region and even in high intensity earthquake zone.The damage of tunnels have the larger relationship with depth under earthquake action,and the seismic design of deep buried and shallow buried of tunnels are quite different.How to reasonably judge the types of deep burial and shallow burial of tunnels under earthquake has important practical significance to the safety and economical efficiency of seismic design of tunnels.But so far the judgment of deep burial and shallow burial of tunnels in seismic design is still using the methods under the static conditions which can not reflect the dynamic characteristics of tunnels under earthquake action,also can not give a relatively accurate criterion,and at present there is little research on this problem.Therefore,research on the deep and shallow burial for seismic design of tunnel under earthquake is an urgent problem to be solved,has important theoretical significance and practical application value.In this thesis,we research the judgment problem on the deep and shallow burial for seismic design of tunnel under earthquake,the main research contents and results are as follows:(1)Based on the Bierbaumer theory,the theoretical formula for calculating the critical depth of dynamic deep burial and shallow burial of tunnel under earthquake is deduced,and the factors influencing the calculation results and the applicable conditions of the formula are analyzed.(2)Based on the pressure arch theory,using the stress path method to research the relationship and change rules between tunnel depth and pressure arch height under different tunnel depth conditions,which includes different rock classification,different seismic intensity,different structural shapes and different tunnel span,and thus get the critical depth of the arch of dynamic deep burial and shallow burial of tunnel under different calculation conditions.A judgment calculation formula of the critical depth of dynamic deep burial and shallow burial of tunnel is presented on the basis of considering various kinds of factors influenced on the critical depth of the arch.(3)Using dynamic finite element numerical analysis method to research the relationship and change rules between tunnel depth and lining stress,surrounding rock stress increase coefficient under different influencing factors,and then,use the inflection point of change rules as the reference base of the critical depth judgment of dynamic deep burial and shallow burial of tunnel under eartequake action,finally get the reasonable values range of the critical depth of dynamic deep burial and shallow burial of tunnel under different analysis conditions.(4)Using the shaking table model test to research the relationship and change rules between tunnel depth and dynamic stress of tunnel lining,dynamic earth pressure and seismic acceleration of surrounding rock,then use the inflection point of change rules in combination with soil deformation around the tunnel and the damage form of lining structure after test under earthquake action to comprehensive consideration for the judgment basis of the critical depth of dynamic deep burial and shallow burial of tunnel,finally get the reasonable critical depth under test conditions.It validate the feasibility and reliability of other research methods by comparing the result of experimental analysis with other research methods.(5)Through the comprehensive comparison of different research methods,found that the results have a more consistent,and also have differences.This thesis uses several research methods and mutual authentication in lacking the systematic research on the judgment method of the critical depth of dynamic deep burial and shallow burial of tunnel,and provides the reference in order to judge the critical depth is more consistent with the actual conditions.This thesis researches the problem of the critical depth of dynamic deep burial and shallow burial of tunnel under earthquake,we except it can provide a beneficial reference for seismic design of tunnel engineering.