Research On Failure Mechanism And Control Technology Of Stick-slip Fault Tunnel In Strong Earthquake Area

With the continuous and in-depth development of China's transportation infrastructure,tunnels crossing stick-slip faults are constantly emerging.Statistics of Wenchuan earthquake disasters show that fault dislocation induced by strong earthquakes will cause serious adverse effects on existing tunnels.It is necessary to carry out systematic research on viscous-slip fault tunnels in strong earthquake areas.This paper,based on the seismic damage of F8 stick-slip fault section of Duwen high-speed,is to have a systematical research into dynamic response,failure mechanism,design method and control technology of tunnel with stick-slip fault in strong earthquake area by means of numerical simulation,theoretical deduction and field data.The research work and results are as follows:With the increase of fault breakage bandwidth,the maximum principal stress and influence range of the structure increase gradually,and with the increase of fault dip angle,the maximum principal stress of the structure increases gradually,but the influence range decreases gradually;the change of fault breaking width and fault dip angle has a greater impact on the maximum principal stress of the structure.The anti-dislocation design is the key point in the design of viscous-slip fault tunnels in strong earthquake area;the hanging wall of the tunnel is the key point in the longitudinal design of the tunnel with stick-slip fault in strong earthquake area;and the arch top of the tunnel is the key point in the cross-section design of the tunnel with stick-slip fault in strong earthquake area.The second lining structure of tunnel is under the combined action of tension,compression and shear in the process of strong earthquake vibration,and under the combined action of strong earthquake vibration and fault dislocation,the second lining structure is mainly under the combined action of tension and shear.Based on the energy release theory,the releasable strain energy formula of the unit is deduced,and the calculation method of tunnel anti-fault structure design under the action of fault stick-slip fault is established by the principle of energy conservation.The first step is to determine the energy generated by fault slip,and the second step is to determine the absorbable energy of surrounding rock-lining system.In order to ensure structural safety,the energy generated by the fault slip should be less than that absorbable energy of surrounding rock-lining system.The increase of the elastic modulus of the damping layer will reduce the seismic absorption effect of the structure,when the elastic modulus of the damping layer increases to a certain extent(about 100 MPa),the seismic absorption effect tends to be stable;the increase of the width of the sho ck absorption joint can improve the shock absorption effect of the hanging wall of the tunnel,but the shock absorption effect of the foot wall of the tunnel is limited.The anti-seismic effect of single fortification measures is limited,and the effect of rigid-flexible combination measures is obvious in resisting and reducing the combined effect of strong earthquake vibration and fault dislocation.The anti-seismic effect of rigid-flexible combination measures is between 78%and 141%.The anti-seismic effect of rigid-flexible combination measures is between 58%and 67%in resisting and reducing the combined effect of strong earthquake vibration and fault dislocation.