Study On The Damage Pattern Of Tunnel Structure Under The Action Of Earthquake And Creep Slip In Active Fracture Zone

With the rapid development of China’s economy and the in-depth implementation of the strategy of large-scale development of the western region,the transportation tunnel project has developed rapidly.Due to the many faults and frequent earthquakes in the western region of China,the tunnel construction in the western region inevitably passes through geological faults in the selection of routes,and it is inevitable that active fault zones will be encountered.Fault creep-slip misalignment in active fault zone is a major threat to the safe construction and operation of tunnels,and coupling with seismic action can easily cause tunnel engineering disasters,so it is urgent to study tunnels through active fault zones to find out the impact of fault misalignment and seismic action on structural safety.Relying on the key project of the National Natural Science Foundation of China"Catastrophe Mechanism and Life Cycle Safety Evaluation and Design of Tunnel Engineering under Strong Seismic and Perrigtuous Effect of Active Fault Zone"this study selects the F9-1 tunnel through the fault zone in the "Kangding No.2 Tunnel Project of Sichuan-Tibet Railway"as the research object,and uses the combination of model test and numerical simulation to study the response law of tunnel structure under three different effects,namely creep,earthquake and coupling of the two,and reveal the tunnel structure failure mechanism,aiming to provide a reference for engineering safety.The specific research contents and conclusions are as follows:(1)The influence of fault creep on tunnel structure under different dislocations,fracture belt width and inclination angle is studied,and the research results show that the overall deformation degree and scope of tunnel structure are basically the same under different working conditions,and the overall distribution is "S";the tunnel structures all have stress concentration phenomenon when passing through the broken zone.The larger the amount of fault dislocation,the smaller the width of the fault,and the greater the inclination angle,which is more detrimental to the safety of the tunnel structure.The above results are basically consistent with the results of the model test,that is,the tunnel structure first cracks and fails at the bottom of the arch,so these parts should be heavily fortified.(2)The influence of different ground movements on the structure of fault tunnels was studied,and the results showed that the relative deformation of the tunnel structure at the fault zone was greater than that of other positions,and the top of the arch was the most obvious.The tunnel structure has stress concentration phenomenon at the fault,and the maximum stress occurs in the left and right arches,so the seismic fortification should be strengthened.(3)The influence of the coupling of peristalsis and seismic on the structure of fault tunnel was studied,and the results showed that the stress concentration occurred in the tunnel structure when passing through the fault fracture zone,and the maximum stress on the left and right arches of the tunnel structure was significantly greater than the maximum principal stress of the vault and the inverted arch.Seismic action has little influence on the tunnel lining structure,and creep-slip dominates.