Vibration Reduction Mechanism And Technology Of Drilling And Blasting Construction In Beijing Zhangjiakou High Speed Railway Tunnel Group

In the blasting construction of small spacing tunnel,the excavation of adjacent tunnel will have a certain impact on the stability of the first tunnel,so in the process of blasting construction,it is usually required to take certain vibration reduction measures to protect the stability of the first tunnel and its intermediate rock wall.Among them,the use of electronic detonators or the arrangement of damping holes or damping ditches in the excavation of tunnel face is a more effective method of damping.However,different damping holes,damping trenches or electronic detonators with different delay time will have different damping effects.In order to obtain the best vibration reduction effect,this paper studies the influence law of the parameters of the shock absorption hole,the shock absorption ditch and the electronic detonator on the vibration reduction effect through numerical simulation,and puts forward the best parameter combination suitable for the actual project,and applies the research results to the actual project to get a better vibration reduction effect.The main research contents and achievements of this paper are as follows:(1)Combined with the actual project of Badaling Great wall section of Beijing Zhangjiakou high speed railway,the influence of different parameter damping holes arranged on the excavation tunnel face on the damping effect of adjacent advance tunnels is studied by numerical simulation.The influence law of the size,spacing,depth,row number of damping holes and the distance between the damping holes and the blasting holes on the damping effect is obtained,and the best damping effect by the best parameter combination of shock absorption hole suitable for the actual project is proposed.(2)Similar to the study of shock absorption hole,through numerical simulation,the influence of different parameters of shock absorption ditch arranged on the excavation tunnel face on the vibration reduction effect of adjacent advance tunnel is studied,and the influence rule of the width and depth of the shock absorption ditch on the vibration reduction effect is obtained,and the best combination of parameters of the shock absorption ditch suitable for the actual work is proposed.(3)Combined with the actual project,through numerical simulation,the vibration wave period of single hole under the actual engineering surrounding rock condition is obtained.Through the comparison of the vibration reduction efficiency of cut hole blasting under different delay time,the optimal delay time interval of cut hole under the actual engineering surrounding rock condition is obtained.(4)Combined with the field measured data and according to the blasting safety regulations,the stability of the first tunnel lining during the blasting construction of the main tunnel in the range of DK68 + 185 ? DK68 + 115 is evaluated.(5)Through numerical simulation,the damping efficiency of the optimal parameter combination of the damping hole,damping ditch or the use of electronic detonator is obtained,and the damping measures with the highest damping efficiency are applied to the actual project,effectively reducing the tunnel vibration.Finally,combined with the field monitoring data,the validity of the model is verified.