Study On The Vibration Effect Characteristics Of Underground Cavern Group Blasting Excavation

The seismic effect of blasting excavation will inevitably affect the adjacent existing cavern,this has always been a difficult problem in the excavation of the cavern group,and has always been the focus of the research of experts and scholars.This paper relied on the research of blasting vibration hazard control of a lead-zinc mine in southern China,on the basis of reading a large number of related literatures,combined the latest research findings of experts and scholars,with modern blasting theory,dynamics theory,rock mechanics,and signal processing as theoretical basis,we studied the effect of the seismic effect on the adjacent cavern by the field test method.According to the engineering practice,the scene model was built,and with the Flac3 D finite element software as tool,the vibration data of each monitoring point was obtained by numerical simulation,the accuracy of numerical calculation was verified by comparing with field measured data.On the basis of this,the influence rule of the blasting excavation of the cavern on the vibration velocity,displacement and stress of the adjacent existing parallel chamber was studied,and the scientific guidance was provided for the blasting excavation.The main research results of this paper are as follows:(1)Through the regression analysis of the vibration data monitored by five blasting tests,the vibration intensity attenuation rule of rock point tangential vibration during excavation process of chamber blasting in S5#S chamber was concluded,also the relationship between the maximum explosive weight and the minimum explosive distance was calculated.Used the HHT method,the energy size of frequency of blasting vibration signal was analyzed,the energy of frequency that within 50 Hz occupy half of the total energy,and the energy of frequency that within 300 Hz was 98.9% of the total energy.It is indicated that the vibration frequency of these five blasts is within 300 Hz.(2)Three-dimensional model of the cavern group was established,and according to the empirical formula and the actual blasting parameters,a triangular blasting impact load model is obtained,then compared the numerical results with the field measured data,the relative error is within 15%.The trend consistency of the field measured vibration velocity regression curve with the numerical simulation result are good,especially in the area that far away with explosion source,the approximate degree of the two curves is higher,which indicates that the numerical calculation model established in this paper is reasonable.(3)Based on the dynamic analysis of the model,the vibration characteristics of the surrounding rock mass are studied.The results show that the vibration velocity,displacement and stress of the surrounding rock mass near the explosion source side are much larger than that of the backside,the part where the maximum vibration velocity and the maximum displacement occurs of the adjacent cavern are the upper part of the wall near the explosion source.Under the effect of blasting vibration,the tensile stress concentration in the middle of the adjacent cavern wall is further increased,this increases the risk of stretching damage in the middle of the straight wall.Meanwhile,the action of dynamic load also increases the shear stress concentration of the arch foot and the wall foot,which can easily cause the shear failure.Through the analysis of the change law of vibration velocity,displacement and stress we can know that the upper part of the wall near the explosion source is the most dangerous part,therefore,the protection and monitoring of this part should be strengthened during blasting.The results of this study can effectively monitor and predict the damage degree of blasting excavation to the adjacent cavern structure,which has important guiding effect on safe construction and effective protection.