Blasting Vibration Effect On Existing Tunnels And Optimization Of Blasting Parameters In Construction Of New Metro Tunnels

With the increase of the number of subway lines in the city,many new subway tunnels need to go through the existing tunnel.When the new subway tunnel is constructed by mining method,blasting vibration will affect the existing tunnel.Because of the complex stress state in the surrounding rock of tunnel,blasting vibration produced by excavation is difficult to be effectively controlled.Therefore,it is necessary to study how to reduce the impact of blasting vibration to the existing tunnel structure and ensure the normal operation of the existing tunnel.In this paper,the mining construction interval tunnel of Yinhu Station to Bagualing Station of Line 6 of Shenzhen Metro is taken as the engineering background.ANSYS/LS-DYNA is used to analyze the influence of new tunnel blasting construction on existing tunnel,and the blasting parameters are optimized.The specific research content is as follows:(1)The numerical model was established on the basis of the actual blasting parameters,and the accuracy of the numerical model parameters was verified by comparing the simulated and measured surface vibration data.(2)ANSYS/LS-DYNA is used to simulate the impact of blasting vibration on the existing tunnel in tunnel excavation,analyze the most unfavorable position of the existing tunnel affected by blasting vibration,and judge whether the blasting vibration velocity of the existing tunnel exceeds the blasting safety control standard,and whether the blasting scheme will affect the safe operation of the existing tunnel.(3)In view of the shortcomings of the existing blasting scheme,three blasting parameters,namely,blasting footage length,differential delay time and uncoupling coefficient of charge,were selected to analyze the impact of different blasting parameters on blasting vibration under different working conditions and optimize them to reduce the intensity of blasting vibration.(4)According to the optimization results of blasting parameters,the new blasting parameters are designed,the blasting construction scheme is adjusted,the reasonable measures of vibration reduction are put forward and applied to engineering practice.Based on the engineering practice,this paper studies the problems such as the large blasting vibration intensity encountered in the mining method construction process,which has certain practical value and provides reference for the mining method excavation of urban subway tunnels in the future.