Study On The Blasting Vibration Control Technology Of New Mountain Tunnel Under-cross Existing Diversion Tunnel

With the rapid development of China's infrastructure,the number of tunnels continues to increase and the situation of new tunnels under-crossing existing tun nels also occurs frequently.At present,the drilling and blasting method is still a major construction method of the mountain tunnel.The blasting will have vibrat ional effects on the adjacent tunnel.In order to ensure both the safety of existin g tunnel and the efficiency of new tunnels,it is of great scientific significance t o study the propagation law of blasting seismic waves and the vibration response of existing tunnels during blasting.This paper took the Xinlin tunnel under-cross existing Shapin diversion tunn el in The Chengdu-Kunming railway as the engineering background.Based on th e theory of blasting seismic wave,This paper discusses the vibration velocity of tunnel concrete lining Through finite element analysis software,the dynamic resp onse law of diversion tunnel caused by blasting seismic wave is studied.At the same time,the corresponding blasting parameters of the controlled blasting sectio n are optimized according to the engineering practice and relevant specifications.The main research results are as follows:(1)According to the theory of elastic stress wave,the inner surface of tunn el lining is regarded as a free surface.The incidence angle of the most unfavora ble stress wave and the maximum safe blasting vibration speed of tunnel concret e lining are obtained.(2)Through regression analysis of the monitoring data,the parameters of So dev's empirical formula for blasting under this project is obtained.Based on the numerical simulation software of LS-DYNA,a two-dimensional model and a thre e-dimensional model of tunnel blasting are established.By comparing the measur ed and calculated values,the validity of the model is verified,and then the vibr ation response of the diversion tunnel is analyzed.The most disadvantageous position of the diversion tunnel cross section,the range of longitudinal influence an d the propagation law of vibration between surrounding rock and lining are studi ed.(3)In view of the possible problems of blasting scheme and vibration monit oring measurement in engineering practice,The working conditions under differen t blasting parameters are established,and the parameters in the corresponding bla sting scheme are optimized after analysis and comparison.At the same time,the corresponding blasting vibration reduction measures are put forward.