Study On Vibration Safety Influence Of Existing Tunnel Induced By Drilling And Blasting Of Underpass Tunnel

The influences of building or structure vibration caused by adjacent blasting excavation are universal,blasting vibration effect and vibration control on approach tunnels have become hot research topics in the engineering field.Jinjiang Jinjishan diversion tunnel has the characteristics of passing under the existing tunnel at a very small clearance and angle,which make the vibration safety influence in upper tunnel when blasting in cross section an urgent technical problem to solve.Based on the construction of Jinjiang underpass tunnel,The combined methods of field blasting experiment,vibration monitoring and numerical simulation are used for the research on the propagation characteristics of blasting seismic wave,characteristics of blasting vibration response and vibration control measures.According to the location characteristics in different sections of tunnel,the site blasting tests are carried out.And the preliminary cognition of the characteristics about existing tunnel vibration response at different blasting sections is generally obtained.Based on that,intensive vibration monitoring of the whole cross section is also carried out,by the work of vibration effect evaluation based on data feedback,some measures are taken to improve the effect of cyclic blasting,and the effective control of blasting vibration is realized.For a further research on the laws of blasting vibration response of the underpass tunnel at a small angle,based on Jinjiang tunnel,and by using ANSYS LS-DYNA software,numerical simulation about vibration responses and stress responses of the existing tunnel lining under the cut blasting load which produced by different working faces is studied.Then,the laws of field measurement are verified,and a comprehensive understanding about the laws of blasting vibration is obtained.Furthermore,Numerical simulations of typical tunnel vibration response under different cross angle conditions are studied.By a series of research on vibration effects on existing tunnel induced by blasting of underpass tunnel,the main achievements are as follows:(1)The intensity of the vibration response in the upper tunnel lining caused by blasting seismic wave reaches the maximum in the vicinity of the explosion source,and the vertical velocity is controlled.Peak particle velocity(PPV)facing the blasting side is obviously greater than PPV away the blasting side in the same section of lining.Moreover,the attenuation rate of the vibration velocity in un-excavation area is less than that of the excavated area.(2)By using the measures of reducing circulating footage,increasing the number of excavation,optimizing detonation network,and contour control technique,helping to effectively control vibration intensity and obtain good excavation quality.(3)The monitoring data and numerical simulation both show that cross angle factor influences vibration response characteristics of tunnel.Under the same blasting load,the smaller the cross angle is,the greater the vibration intensity is,vertical velocity vy and axial velocity vz mainly influence the lining,With the increase of angle or distance,vibration intensity decreases,vz and vy significantly decrease,while radial vibration vx increases in number and proportion.It indicated that cross tunnel with large cross angle or remote parallel are more conducive to stable.