Research On The Test And Propagation Law Of Earth Surface Explosion Seismic Wave

While explosive technology brings convenience to industries,a series of hazards,especially the seismic effects of explosions,have also become the focus of attention.At present,most researches focus on the seismic waves induced by explosions in the rock and soil.However,when accidental explosion accidents occur,most of them are surface explosions.Therefore,studying and analyzing the propagation characteristics and attenuation laws of surface explosion seismic waves is a further improvement of the theory of explosion seismic effects,and then provides a reasonable reference basis for safety protection and engineering applications.In this paper,through the establishment of a building model,ground explosion tests with different charges and different initiation conditions were carried out.Using theoretical analysis,field test,digital signal processing and other methods to fully research and discuss the testing technology and propagation law of ground explosion seismic waves.The main research contents and results are as follows:(1)Theoretical research and analysis on the types of explosion seismic waves,wave equations and propagation mechanisms have been carried out,and the characteristics and propagation laws of different types of seismic waves have been clarified.That is,body wave has fast speed,small amplitude and short period;surface wave has slow speed,large amplitude and long period.The two gradually separate with the increase of the propagation distance and most of the energy of the surface explosion is concentrated in the surface wave.Through the analysis of the evolution of seismic waves,it is believed that the surface soil layer is an inelastic medium when the ground explodes,which will cause the seismic waves to disperse during the propagation process.In addition,comparing natural earthquakes and explosive earthquakes,it shows that the two have a certain similarity,and the vibration frequency of explosive seismic waves is higher,the energy carried is less,and the action time is shorter.(2)Through the theoretical analysis and practical application of the explosion vibration test system,the monitoring of ground explosion seismic wave signals with different initiation conditions and initiation charges has been completed.After processing measured data,the waveform characteristics of the ground explosion seismic wave are obtained.The calculation of the relevant waveform parameters shows that when the seismic wave propagates in the sandy environment,its wave speed and wavelength are much smaller than the natural seismic wave,and the vertical amplitude is the largest and the tangential amplitude is the smallest.After fitting the empirical formula to the peak velocity of the seismic wave,the values of the attenuation coefficients K and ? related to the environmental medium are 148 and 1.51,respectively.And when detonating in the presence of buildings,the seismic wave amplitude-ratio distance scatter points all fall below the seismic wave fitting curve for detonation without buildings.It shows that the existence of buildings will cause reflection,refraction and scattering of seismic waves,so that the propagation amplitude decays faster.(3)Through theoretical of Fourier transform and wavelet packet analysis methods,and using computer software for programming,the Fourier transform and wavelet packet analysis of explosion seismic wave signals are realized.The Fourier spectrum shows that the dominant frequency band in the near area of the explosion vibration is 0-30 Hz,and the center frequency is about 20 Hz;the dominant frequency in the far area of the explosion vibration is between 20 and 40 Hz,and the center frequency is about 30 Hz.With the increase of the propagation distance,due to the scattering effect and the difference in the speed of the body wave and the surface wave,they will gradually separate,leading to the fracture of the dominant frequency band of seismic waves.The energy distribution of seismic waves in different frequency bands is obtained by wavelet packet analysis.The energy distribution is mostly concentrated in the range of 0-31.250 Hz and 46.875-62.500 Hz.As the propagation distance increases,the energy of the seismic wave in the 46.875?62.500 Hz frequency band increases to some extent in the case of without building.When there is a building,it will absorb more energy in the middle and high frequency components,so that the seismic wave will propagate in the low frequency.