Attenuation Law And Signal Time-frequency Analysis Of Blasting Vibration Under Two Initiation Methods

With the extensive application of blasting technology in engineering field,people pay more attention to the influence factors and the control technology of blasting vibration.As a commonly used blasting technology,the delay blasting technology with different amount of explosive detonates successively causes the interference effect of blasting vibration wave in the process of propagation,and the difference of delay accuracy of different detonators leads to the difference of seismic wave interference in time and space.In order to study the blasting vibration signal of detonating tube detonator and electronic detonator,the rock physical mechanics experiment and the field blasting experiment of open pit mine were carried out in this paper.According to the measured blasting vibration signal,the characteristics of blasting vibration in time domain and frequency domain are analyzed comprehensively from the aspects of attenuation law,energy of each frequency band and peak vibration velocity of each frequency band.The main research contents and conclusions are as follows:(1)Rock physical and mechanical parameters of open-pit mine were obtained through acoustic test,point load test and uniaxial compression experiment,so as to determine the on-site blasting plan and monitor blasting vibration signals.The analysis of the blasting vibration peak velocity of the two initiation methods shows that the electronic detonator can effectively control the blasting vibration.Compared with the detonating tube detonator,the initiation can reduce the particle peak velocity by more than half,and the larger the charge,the smaller the distance between the detonation center,the better the vibration reduction effect.(2)Based on the prediction formula of blasting vibration,the attenuation law of peak velocity and main vibration frequency of the two detonating methods with the interval deck charge and detonation center distance were compared and analyzed.The results show that the attenuation of blasting vibration velocity of electronic detonator is slower than that of detonator,but the attenuation of main vibration frequency of electronic detonator is faster than that of detonator.(3)In order to obtain the maximum charge in a more scientific and reasonable way,the safe allowable vibration velocity of blasting vibration is divided in more detail according to different frequency intervals.The analysis shows that,at the same safety distance,the electronic detonator can increase the maximum dose of charge on the basis of detonating tube detonator,which is beneficial to improve economic benefits.However,when the safety distance is large,in order to prevent the resonance phenomenon between blasting vibration and the building,the selection standard of the maximum charge in the detonation of electronic detonator should be appropriately reduced.(4)Based on the wavelet analysis,the energy and peak vibration velocity distribution characteristics and attenuation rules of the two initiation methods in different frequency bands were analyzed by extracting blasting vibration signals of each frequency band.The analysis results show that most of the energy of blasting vibration signals is distributed between 9.77 and 312.5Hz,but with the increase of detonation distance,the proportion of high frequency energy decreases,while the proportion of low frequency energy increases,which indicates that the propagation medium has the function of high frequency filtering.In addition,the distribution characteristics of the energy peaks in each frequency band and the PPV peaks of the two detonators are consistent,and the PPV peaks in each frequency band and the peak vibration velocity of the original signal show certain self-similar characteristics,indicating that the blasting vibration intensity can be expressed by the energy in each frequency band.