Excavation Blasting Dynamic Response Analysis For Surrounding Rock And Structure Adjacent To Tunnel Groups

Blasting excavation of multiple tunnels with small spacing,blasting seismic waves generated by explosive explosion may endanger the safety and stability of surrounding rock and shotcrete structures of adjacent tunnels,which will directly threaten the safe of workers.Based on a tunnel group project,this paper adopt 3D FEM to analyze the effects among parallel tunnel groups and cross tunnel in the condition of blasting.Firstly,the dynamic response law of surrounding rock and shotcrete structure under the condition of shotcrete with different types of surrounding concrete and concrete with different surrounding rock types is discussed.Secondly,the spatial intersecting tunnels with different vertical spacing and different surrounding rock types are established.The distribution law and influence of new tunnel blasting on the vibration velocity and principal stress of the existing traffic tunnel lining are analyzed,and the safety spacing is determined.This provides a reference for the design and optimization of on-site construction blasting schemes and similar engineering construction.The main research work and conclusions of this paper are as follows:1.Through the analysis of rock mass blasting mechanism,blasting wave propagation theory and blasting vibration numerical simulation research at home and abroad,the rock mass blasting mechanism and failure form,blasting stress wave classification,attenuation law and blasting vibration safety standards are analyzed in detail.According to the comparison of the dynamic finite element research methods,theblasting load model is determined.2.The finite element numerical simulation is used to study the vibration response of the parallel tunnel groups with or without shotcrete,surrounding rock of different rock types and lining structure during blasting.The results show that the adjacent tunnel,single-interval tunnel and multi-interval tunnel are synchronized and the lag is 1~3times span.The middle part of the tunnel is most affected by blasting vibration.By comparing the vibration velocity and principal stress attenuation law of tunnel shotcrete under different working conditions of shotcrete and different surrounding rock types,it is concluded that in the case of shotcrete,when the adjacent tunnel of Class III surrounding rock excavat should be delayed 1 time span.Working conditions will be f meet the requirements.In the case of shotcrete,the excavation tunnels of adjacent tunnels of Class III and IV surrounding rock shall be delayed by 2 times and 3 times respectively.When single-slot tunnel blasting,Class III surrounding rock shotcrete meets the requirements.After the Class IV surrounding rock shotcrete,the tunnel should be delayed by 1 times.When the multi-interval tunnel is synchronized and the lag is 1~3times spanning.Concrete has little impact.3.Through the numerical simulation to change the vertical spacing between the two tunnels,the blasting dynamic response of the 4# tunnel excavation blasting concrete in the upper tunnel of the III and IV surrounding rock is analyzed.It is concluded that the blasting vibration has the greatest influence on the arch & bottom and the wall foot of the existing traffic tunnel;The vibration velocity and principal stress of each section on both sides of the cross section are roughly symmetrically distributed with respect to the cross section;When the spacing is less than 1.5D,the vibration speed varies greatly with the spacing,and vice versa;When the tunnel spacing is greater than 2.5D hole spacing,it is the optimal safety spacing.When the blasting construction,there is no damage to the shotcrete in the traffic tunnel.