Study On Vibration Effect Of The Existing Tunnel Caused By Blasting Construction Of New Tunnels

Since the 1990 s,with the development of the national economy,the railway construction in China has been booming,and the railway network has been constantly improved.In this process,it came out an unending flow that new tunnels have been constructed where near the existing tunnels.However,the drilling and blasting method is still the mainstream method in the construction of mountain tunnels.Blasting vibration will affect the structure of existing tunnels and endanger the safety of tunnels' operation.Based on the Pumei railway project,this paper studies the blasting vibration effect of the existing bias tunnel induced by two nearby tunnels.The research object has three complex problems: bilateral proximity,bias and blasting,which pose a great threat to the existing tunnel structure.At the same time,there are few studies on the order and influence law of blasting construction of two tunnels under biased pressure.Therefore,in order to build railway tunnels with high standards and reduce the risk of tunnel construction,it is of great research value and practical significance to study the influence law of existing tunnels under blasting load.This paper systematically studies the vibration effects of new tunnel blasting on existing tunnel through on-site testing and numerical simulation.The main results are as follows:(1)This paper analyzes the research status of tunnel blasting at home and abroad,studies the blasting mechanism and failure mode of rock mass,and establishes the blasting vibration criterion of this paper.(2)In this thesis,the three-dimensional numerical model is established by using the finite element software ANSYS/LS-DYNA.Then the peak value of the vibration velocity of the existing tunnel lining structure under the new tunnel blasting construction is calculated and compared with the field measured data.And it is proved that the numerical simulation method is feasible.(3)The numerical simulation of different blasting schemes under two surrounding rock conditions is carried out.By comparing the effects of blasting on the existing tunnel induced by two new tunnels under different horizontal spacings,the vibration response of existing tunnels under bias conditions is determined,and reasonable construction sequence recommendations are proposed based on relevant indicators.(4)The variation of vibration velocity along the axis of the existing tunnel is obtained by numerical simulation,and the vibration propagation and attenuation along the axis of the tunnel under two blasting schemes are revealed.(5)In this thesis,the influence of millisecond blasting with different millisecond intervals on the vibration of existing tunnel under different charge ratios is analyzed by numerical simulation.Based on the calculation results,the optimal design scheme of cutting holes is established,which provides a reference for optimizing the blasting design scheme.