Analysis Of Failure Mechanism Of Mountain Tunnel Crossing Active Fault And Its Security

When the mountain tunnel passes through the active fault,due to the activities of the fault rupture,the stress concentration occurs near the interface of the tunnel structure and fault.It is one of the difficult problems in seismic engineering to the study of the anti-seismic technology of the tunnel structure.In this dissertation,combined with the commonly used seismic measures,after comprehensive comparison,the paper presents a comprehensive multi-level shock resistant variable structure,and show the relevant numerical simulation analysis.The main conclusions are as follows:(1)Based on the elastic foundation beam theory,using the hyperbolic function,solve the expression of longitudinal force of the tunnel structure.(2)By comparing the stress of the tunnel structure under the action of the peak acceleration of 0.3g seismic wave and the fault dislocation 0.5m.It is known that the fault dislocation is the main cause of the tunnel structure damage.Through numerical simulation,studied under different fault factors,which include fault rate,fault width,fault dip,fault momentum and fault rupture form,tunnel structure stress and stress distribution caused by the faulting.The results show that the fault dislocation and fault rupture form have the greatest influence on the tunnel structure?(3)In the fault fracture zone and its vicinity,a comprehensive multi-level seismic structure is proposed.The structure is:Tunnel section construction,cross section expansion,the establishment of 0.3m thick shock absorption layer,in the main area of the impact of grouting 2m thick,the secondary influence of the region 1m thick grouting,the establishment of shock absorbing joints.The numerical simulation shows that the structure can be safely operated at the fault width of 20m,the fault dislocation velocity is O.lm/s,and t fault dislocation quantity of 0.5m.(4)The calculation of the load acting on the tunnel structure is carried out,which under the action of no anti shock measures.There is an amplification factor between static load and dynamic load.By means of the stress ratio of the tunnel structure before and after the fault faulting,the load amplification factor under the normal fault dislocation,the reverse fault and the strike slip fault dislocation are solved respectively.(5)According to the difference of seismic structure and stress along the longitudinal cross section of tunnel,the expression of displacement and internal force of the resistance to shock absorption structure is put forward.