Study On Seismic Dynamic Response And Aseismic Measures For Fault Fracture Zone In Mountain Tunnels

The lining structure of the fault zone of the mountain tunnel is prone to more serious damage during the earthquake.How to prevent the seismic fortification of the fault zone is a difficult and difficult problem in the construction of the tunnel engineering.The research on the seismic dynamic response and the aseimic measures of the fault zone of the mountain tunnel is helpful to improve the tunnel.Aseismic ability to mitigate the damage.This paper takes the Mogangling tunnel as the support project,and utilizes on-site investigations,laboratory experiments,and numerical simulations to carry out seismic response laws and anti-seismic measures for the fault fracture zone in mountain tunnels.The research results not only provide suggestions for the seismic fortification of the Mogangling tunnel,but also provide a reference for the seismic fortification of similar fault zones.Theresults obtained in this paper are as follows:(1)Using FLAC3 D software,a numerical model was established to simulate the portal section of Mogangling tunnel,and the dynamic response rules of acceleration,displacements and lining structure stress of the mountain tunnel portal section are revealed.The fault has a significant amplification effect on the acceleration of the tunnel lining,and the closer,the greater.The maximum shear stress,equivalent stress and maximum or minimum princil stress of lining are all larger and concentrate in fault fracture zone.The displacement dislocation of lining in fault fracture zone is more severe than other position.According to the results above,the fortification range can be fault fracture zone and each 10-m before and after in Mo Gangling tunnel.(2)Based on the measured parameters of the surrounding rock of the mogangling tunnel,a typical tunnel lining structure model with different fracture zone width and different broken zone angle is established.The results show that,with the increasing of fault width,the response such as acceleration,stress,X-dis,Z-dis of tunnel lining increase.With the reduction of dip angle,the response such as acceleration,stress,X-dis and Y-dis of lining increase.In summary,the fortification range can be fault fracture zone and each 10 m to 15 m before and after in tunnel.(3)In view of the four kinds of anti shock absorption measures,such as grouting to reinforce the surrounding rock,setting damping layer,setting aseismic seam and changing lining rigidity,the calculation model of different reinforcement thickness,different damping layer thickness,different type of seismic seams and different lining stiffness is established,and the anti shock mechanism and effect of different anti shock measures are carried out.The results show that with the increasing of thickness of grouting,the acceleration amplification effect of fault fracture zone,stress and displacement of lining decrease.Meanwhile,with the increasing of the thickness of seismic buffer,the acceleration of lining increases,while maximum or minimum princil stress decreases,and the displacement of lining decreases lightly.To sum up,the thickness of seismic buffer equals to 15-cm can acquire preferably effect.At the same time,large-stiffness lining has a large acceleration and stress while its displacement is smaller.Finally,using seismic joints can reduce obviously the peak acceleration and stress of lining at fault,but it will enlarge the displacement of lining.In addition,inclined seismic joints perform better than vertical seismic joints.(4)Based on the dynamic response law and the seismic fortification range of the fault zone of the mogang tunnel,the seismic fortification scheme of the fault zone is proposed.The effectiveness of the proposed aseismic measures is verified by FLAC3 D.The results show that the acceleration,princil stress and displacement of lining decreases,after setting the anti-seismic measures in Mogangling tunnel,which proves that anti-seismic measures are effective,reasonable.The comprehensive use of a variety of anti shock measures is superior to the use of single anti shock measures,and the advantages and disadvantages of different anti shock measures can complement each other.