Study On Seismic Dynamic Response And Antiseismic Measures Of Tunnels Crossing Active Faults

With the continuous implementation of the“Thirteenth Five-Year Plan”of the railway,a large number of tunnel projects have emerged in the western region.It is inevitable that fault fracture zones will be encountered during tunnel excavation.Especially under the action of earthquakes,the lining structure of tunnels crossing active faults is more likely to be damaged.The study of seismic dynamic response laws and anti-vibration measures of mountain tunnels across fault fracture zones is very important.This paper uses the Kongtangla tunnel as a supporting project and uses FLAC^3D finite difference software to study the basic laws of seismic dynamic response of tunnels across fault fracture zones under earthquake action,analyze the impact of active fault dislocation on the tunnel structure during earthquakes,and discuss The anti-seismic effect of different anti-seismic measures,the research results have certain theoretical value and practical engineering significance,the main research content and results are as follows:1.A three-dimensional seismic dynamic numerical simulation of a cross-fault tunnel was carried out.The results show that the fault fracture zone has a significant amplifying effect on the acceleration,stress and internal force of the tunnel lining structure.According to the analysis of the maximum tensile stress angle,the most unfavorable position of the fault fracture zone lining structure is the arch foot,which should be considered in seismic fortification;The dynamic response law of tunnel structure under different fracture zone inclination angles.As the inclination angle of the fault fracture zone decreases from 90°to 30°,the lining safety factor gradually decreases.The seismic fortification with fault inclination angles of 30°,50°,70°,and 90°is proposed.The ranges are 3.6D～4D（D is the tunnel diameter）,2.6～2.8D,1.8D～2D,and 1～1.4D.2.The dynamic response law of the lining structure under normal fault dislocation is studied by imposing a velocity boundary at the bottom of the model.The results show that under different fault fault rates,the tunnel structure is mainly controlled by tensile stress,and its arch waist and arch toe are dangerous parts.The fault resistance of the tunnel should be considered.The fault resistance effect of different grouting reinforcement ranges is studied.The results show that when When the grouting range is5m,the lining structure has tended to be safe.3.The anti-seismic measures of the foam concrete damping layer with different material parameters are set,and the damping effect of the foam concrete damping layer with different density and elastic modulus is studied.The results show that the main stress of the lining structure is greatly reduced after the lightweight,low elastic modulus foam concrete shock-absorbing layer is installed,and the safety factor is greatly improved.As the quality and elastic modulus decrease,the shock-absorbing effect gradually improves.4.The comprehensive loading method of ground motion and fault dislocation is used to simulate the deformation and force characteristics of the tunnel crossing an active fault under the action of an earthquake,and at the same time,the"rigid and flexible"seismic means with anti-error effects and shock absorption effects are used to Analyze its anti-seismic effect.It is obtained that the deformation of the tunnel structure near the fault is mainly controlled by the fault dislocation,and the deformation of the tunnel structure far away from the fault is mainly controlled by the earthquake action;after the joint anti-seismic measures are installed,the principal stress of the lining structure is greatly reduced,which verifies that the anti-seismic measures are reasonable and effective of.