Study On Seismic Fortification And Seismic Measures Of Cross Section Of New Tongziling Tunnel

The transition section of the surrounding rock of the cross-fault fracture zone is a location where earthquake damage occurs frequently.The seismic fortification of the cross-fault tunnel has always been a difficult problem that has to be faced during the construction of the tunnel.To study the dynamic response characteristics of the cross-fault tunnel surrounding rock transition section,It can provide a certain reference for tunnel seismic fortification.Therefore,based on the Science and Technology Research Project of Chongqing Municipal Education Commission(KJ1500534),this paper studies the dynamic response characteristics and seismic fortification of cross-fault tunnels based on the dynamic finite difference method,and obtains the seismic fortification of cross-fault tunnels under different geological conditions.Scope,research results are as follows:(1)Using FLAC3D software to establish a numerical simulation model,the dynamic response of the velocity,displacement,stress and internal force of linings with different rock mass stiffness on both sides of the fault fracture zone are analyzed.The calculation results show that the fault fracture zone has a significant amplification effect on the velocity,displacement,stress and internal force of the lining of the tunnel;the greater the difference in the rigidity of the rock mass on both sides of the fault fracture zone,the more obvious the amplification effect,but it is not numerically Exceeding the rock masses with small differences indicates that the rigidity of the rock mass in the fault fracture zone has a certain restrictive effect on the dynamic response of the fracture zone lining,which reduces the dynamic response characteristics of the rock mass in the fault fracture zone to a certain extent.(2)The stiffness of different surrounding rock on both sides of the fault fracture zone generally shows that the greater the rock body stiffness on both sides,the smaller the fortification range on both sides of the fault fracture zone,and the increase in the width of the fault fracture zone has less effect on the seismic fortification range on both sides of the fault.Taking the supporting project as an example,when the rock mass stiffness ratio on both sides of the fault fracture zone is 2 and 4,the seismic fortification range on both sides should be concentrated in the range of 16～20m;the rock mass stiffness ratio on both sides of the fault fracture zone is 8 and 16,the seismic fortification range on both sides should be concentrated within the range of12～16m.(3)In view of the anti-seismic measures commonly used in the construction of grouting reinforcement of surrounding rocks and changing the stiffness of the lining,the dynamic rules and anti-seismic effects of different anti-seismic measures were analyzed.The research shows that the increase of the thick Ness of the grouting layer greatly reduces the speed,displacement,stress and internal force of the lining.As the thick Ness of the grouting layer increases,the decrease decreases gradually.From the perspective of construction economy,the thick Ness of the grouting layer It is not as thick as possible;as the stiffness of the lining increases,the speed,stress,and internal force of the lining increase significantly,but the displacement decreases.It can be k Nown from the analysis of the internal force of the lining that the stiffness of the lining is not as large as possible,and should be analyzed according to the specific engineering geological conditions.(4)The seismic fortification of the fault section of the new Tongziling tunnel relying on the project meets the requirements of the existing seismic fortification codes.