Study On Transmitted Seismic Wave Field Characteristics And Detection Method Of Goaf In Upper Part Of Coal Seam Groups

The upper goaf of the coal seam group where the working face is located has a direct impact on the safety of the in-plane mining.The 3D seismic exploration on the ground is difficult to meet the fine exploration needs of the upper goaf of the multi seam mining face,and the drilling is limited by the construction cost;the geophysical prospecting method of the mine meets the detection demand because of its advantages such as close to the target and strong effective signal.When the water is less filled,the electromagnetic method has certain advantages The limitation of transmission seismic exploration is an effective method to solve the detection of upper goaf.The premise is to carry out comparative study on the transmission seismic wave field characteristics of the upper goaf of coal seam group,and find out the transmission and transformation mechanism of transmission seismic wave in the upper goaf.In this paper,according to the characteristics of transmission seismic wave field in the upper goaf of coal seam group in the working face,the development,propagation and conversion of seismic wave in goaf with different sizes,voids and collapse state are studied based on three-dimensional numerical simulation.The dynamic and kinematic parameters of different models are compared and analyzed.Based on the field data,the attenuation imaging method of the Airy phase Channel-wave is used to analyze the seismic wave attenuation of the goaf in different sizes,voids and caving states The results of the study are as follows:(1)When the position of goaf passes,the response of P wave is small,and the S-wave phase axis will reflect and diffract,and the phase axis will be widened;when the slot wave signal passes through the stope,the amplitude change is small,but the phase axis is disturbed by the S-wave diffraction,and the amplitude energy will be weakened and the frequency will change when there is a caving zone.In the later period,some energy may be recovered after re intervention,but the identification of the signal phase axis decreases.(2)The change of porosity in goaf has little influence on the development and propagation of seismic wave field,which only shows that the response of amplitude curve changes with the increase of porosity is delayed,among which the lower the porosity is,the better the response of x component to the size of goaf is.In different models,the energy and frequency of the groove wave are directly decreased in the30 m size goaf.the energy of Channel wave near the source boundary of the 120 m goaf will be obvious The energy recovery of the goaf is basically unchanged after the goaf is reduced,and the frequency is basically unchanged;the response of Channel wave near the source position of the 220 m goaf is basically the same as 120 m,but the interference of diffraction wave and the surface wave in the goaf will be enhanced again and the frequency will increase.(3)Based on the results of three-dimensional numerical simulation,although the energy of X-component trough wave is weaker than Y and Z components,the amplitude response to the goaf boundary is stronger than that of the other two components.The X-component has a good response to the size of the goaf,and the amplitude of other components changes more obviously,but the response to the goaf should be mainly reflected in the boundary near the source side,and the far source boundary response is poor.The X-component Channel wave Airy phase amplitude attenuation inversion results of dispersion analysis transmit seismic wave have the best performance in the three components,which can be used as the data acquisition component in the actual exploration.(4)The results show that the seismic wave energy is different from that of the non goaf one.The results of Channel wave energy inversion are in accordance with the drilling results of the mine.It shows that the attenuation of Channel wave signal in the direction of the lower coal face can reflect the development position of the upper goaf of the coal seam group,and it can provide the basis for the detection of the upper goaf of the working face.