| In the process of large-scale highway construction in our country,highway tunnels often pass through the high intensity seismic area,so it is very necessary to study the dynamic response of highway tunnel structure and its safety evaluation.Combined with the science and technology project on transportation construction in the west region by the Ministry of Communications(31874004)“High intensity seismic region earthquake damage assessment and tunnel structure seismic design technology research” and National Natural Science Foundation of China(51078324)“study on aseismatic and damping theory of tunnel to near-fault pulse-type ground motions”.Based on the seismic damage investigation data of Wenchuan earthquake,took Tibet the Galongla tunnel as support project,a large-scale shaking table test was carried out,The dynamic response of the tunnel and its safety evaluation under earthquake are studied.The main research contents of this paper are as follows:(1)The seismic damage of highway tunnels in the "5.12 Wenchuan earthquake" was investigated,Combined with other domestic and foreign tunnel seismic damage data,Factors affecting tunnel damage were analyzed,including tunnel site,seismic wave characteristics,buried depth,geological conditions of surrounding rock,lining conditions etc.the damage mechanism of tunnel caused by earthquake was analyzed from the point of view of seismic wave propagation characteristics.(2)Based on pseudo-static method theory,the load transfer coefficient wais defined,the stress calculation formula of the shock absorption layer was derived.Based on the vibration method,the tunnel damping system model of “surrounding rock-absorption layer-lining” was established,The main factors affecting the damping effect of the absorption layer were studied.(3)The tunnel lining was considered as a long cylindrical shell structure,the analytical solution of axial strain,shear strain and hoop strain of tunnel lining structure were deduced by the wave method and shell theory,And compared with the results of finite element method,it is found that the results are in good agreement.(4)Take the entrance of Galongla tunnel as prototype,the similarity relationships of the model were drafted,the orthogonal tests of similar materials were carried out,the reasonable material mix ratio is obtained.The seismic resistance and absorption shaking table test was made up as the analogous materials of surrounding rocks and lining has been chosen,in which the absorption layers and the measuring points of shaking table model have been arranged.A reasonable seismic wave is selected.The test results were analyzed,Combined with numerical simulation results,The seismic response of the tunnel and the damping effect of the absorption layer are studied.(5)Several kinds of numerical model for dynamic analysis of tunnels was constructed.Several main factors such as peak acceleration of seismic wave,buried depth,surrounding rock level,lining thickness and concrete strength,which affect the seismic response of tunnel are studied by using time history analysis,Reveals the influence of the main factors on the seismic response of tunnel structures.(6)The dynamic stress concentration factor of the surrounding rock is the key parameter to reflect the dynamic response of the tunnel,The factors affecting the dynamic stress concentration factor were analyzed.The results show that: in a certain range,the dynamic stress concentration factor of the maximum and minimum principal stresses is approximately linear with the acceleration amplitude,the buried depth,level of surrounding rock,the thickness of the lining,the strength grade of the lining concrete.Based on the analysis of the above parameters,the evaluation formula and method of the earthquake safety evaluation of the tunnel are put forward. |
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