Research On Propagation Characteristics Of Blasting Vibration Signals In Surface Layers

Blasting operations in underground coal mine production are all near-surface blasting activities.By passive detection of blasting activities in coal mine production and positioning of blasting positions,data support can be provided for a comprehensive grasp of coal mine production and mining scope,coal mine resource supervision and safe production.In this paper,the blasting vibration wave under complex geological conditions near the surface are taken as the research object.Based on D’Alembert model,the dispersion and attenuation characteristics of blasting vibration wave propagating in near-surface complex media are systematically studied by using theoretical analysis,numerical simulation and field verification methods,and a propagation model of blasting vibration wave with frequency dissipation is established,which provides model support for improving the accuracy of vibration wave phase identification and arrival detection.(1)The construction methods and wave equation of Maxwell model,Kelvin model,standard linear model,Boltzmann model and D’Alembert model are compared and analyzed.The construction method of the D’Alembert model is concise and requires few parameters,more in line with the characteristics of blasting vibration propagation media,so the propagation characteristics of blasting vibration wave are studied based on this model.A correction of the viscosity coefficient to the frequency dissipation coefficient is proposed in order to solve the problem that the D’Alembert model can only represent the macroscopic properties,but cannot well represent the propagation characteristics of vibration waves,and the elastic Lame coefficient in the model cannot represent the characteristics of viscoelastic media.The elastic skeleton is changed into viscoelastic skeleton,and the propagation model of blasting vibration wave with frequency dissipation is established by combining the wavefront diffusion theory.The method also solves the problem of dimensional mismatch of the original formula.(2)Using the variable analysis method to analyze the propagation model of blasting vibration wave with frequency dissipation proposed in this paper,the effects of porosity,viscosity coefficient and permeability coefficient on the performance of blasting vibration wave dispersion attenuation characteristics are analyzed.Under the condition of relatively low frequency,the inverse quality factor value would increase with the increase of porosity and viscosity coefficient or the decrease of permeability coefficient,while the change of phase velocity is opposite,which shows the characteristics of high frequency dispersion and strong attenuation.When the frequency increases,it would show the characteristics of low frequency dispersion and weak attenuation.Revealing that longitudinal wave and shear wave have similar dispersion and attenuation characteristics.(3)In order to verify the description effect of the blasting vibration wave propagation model with frequency dissipation proposed in this paper,The simulation study on the fitting degree between the dispersion and attenuation curves with frequency and the measured data of this model,BISQ model and viscoelastic BISQ model,which can characterize the dissipation characteristics of medium,is carried out.The simulation results show that the dispersion and attenuation curves of BISQ model and blasting vibration wave propagation model with frequency dissipation can be used to simulate the fitting degree of measured data.The result shows that the blasting vibration wave propagation model with frequency dissipation has better description effect and uses the least number of parameters.(4)Design verification test,the experimental data are collected and the correlation between the predicted waveform and the actual waveform of the two models before and after improvement is calculated.By comparison and analysis experimental data,the predicted waveform of the blasting vibration wave propagation model with frequency dissipation proposed in this paper has a significant correlation with the actual waveform,which proves that it is of practical engineering significance to use the model to describe the strong attenuation dispersion characteristics of near-surface strata media.