Study On Determination Method Of Blasting Parameters Of Urban Tunnel Under Electronic Detonator Initiation System

The parameter calculation method based on electronic detonator initiation is the basis of accurate and intelligent blasting control of urban tunnel,and its research is still in its infancy.At present,the technical potential of electronic detonators has not been brought into full play in tunnel engineering.An important reason is that there is no blasting parameter calculation method supported by strict theory.The core blasting parameters such as charge and inter hole delay are mostly designed by ordinary mine method.Based on the research background of Chongqing Guanyinqiao tunnel and the theory of delayed blasting vibration synthesis,this paper establishes the parameter calculation method of the whole time history of electronic detonator blasting for various types of blast holes in urban tunnel.The main work is as follows:A synthetic method of delay blasting vibration of electronic detonator for urban tunnel blasting is established.Based on Anderson’s superposition principle,the site single hole blasting test is designed,taking the vibration data at the protected object as the calculation vibration source and fitting the curve;based on the spatial relationship between shallow tunnel and different blast holes,millisecond delay vibration synthesis is implemented by computer program.According to this method,the variation law of the peak value of synthetic vibration velocity under the changes of parameters such as delay time and charge is analyzed,and the blasting parameters are determined after comparison with the vibration control standard.The method is applied to determine the parameters under the single free surface in the initial stage of tunnel blasting.The field test shows that the calculated curve is in good agreement with the measured vibration curve.The problem of identifying the formation time of new free surface in tunnel blasting is solved.Taking the vibration curve of the ground measuring point after the single free surface and single hole blasting in the tunnel site as the calculation vibration source,calculate the synthetic vibration curve with a certain delay interval during the hole by hole cutting blasting(the curve does not consider the influence of the new free surface on the vibration velocity),select the same delay interval and the same charge to carry out the full section hole by hole blasting,and measure the blasting vibration curve at the same measuring point(the vibration curve includes the influence of the new free surface on the vibration velocity);from the comparison of vibration velocity and accumulated energy,analyze and calculate the significant difference interval and critical point between the synthetic vibration curve and the measured vibration curve,and obtain the accurate time of the formation of the new free surface.The blasting parameters of electronic detonator after the formation of new free surface(the second free surface)are determined.On the basis of obtaining the formation time of the new free surface,carry out the on-site single hole blasting test after the formation of the new free surface,take the vibration data at the protected object as the calculation vibration source,based on the delay blasting vibration synthesis theory,use the MATLAB calculation program to carry out the millisecond delay vibration synthesis calculation,and determine the cutting and auxiliary hole blasting parameters after the formation of the new free surface;Through LS-DYNA numerical calculation,the influence of peripheral hole blasting parameters on surrounding rock damage is determined,and the peripheral hole charge and delay parameters after the formation of new free surface are determined.The field test proves the rationality of the selected blasting parameters.In order to determine the optimal blasting parameters according to the complex coupling relationship between multiple blasting parameters,the vibration wave synthesis theory and calculation program are used to solve the vibration synthesis curve under the combination of different charge,the number of hole and delay parameters.Considering the influence of multi factor coupling between blasting parameters,each blasting parameter is selected and the optimal parameter interference is used to eliminate vibration.For the difference of vibration characteristics between long and short delay,the difference of blasting synthetic vibration velocity between long and short delay is compared based on the calculation method of delay vibration synthesis.It is found that the vibration velocity of long and short delay both may exceed the standard;Monte Carlo method is used to study the influence of the initiation error of electronic detonator on the synthetic vibration velocity of short and long time delay.The delay error of electronic detonator has a greater influence on the synthetic vibration velocity of short time delay blasting superposition;The difference of accumulated energy of long and short delay time before the formation of new free surface is analyzed.It is obtained that when the number of blasting holes is large,the accumulated energy of short time delay is large.Through numerical simulation and theoretical analysis,the influence of inter hole delay on multi hole synergy of cut blasting is studied.In order to enhance blasting synergy,the inter hole delay should be taken as a small value(0-10ms).Based on the above research results,the blasting parameters of electronic detonator in the whole time course of urban tunnel blasting are determined,and the field tests were carried out.The high-efficiency footage is realized while controlling the low vibration velocity,which gives full play to the advantages of the electronic detonator.The parameter calculation method has a reliable theoretical basis and calculation accuracy,which is of great significance to the blasting parameter design of electronic detonators in urban tunnels and the realization of accurate tunnel blasting in the future.