Research on the Channel Wave Field Characters of Goaf in Coal Mine and Its Application

Goaf badly affects coal mine production safety; therefore, accurate geophysical exploration method to ascertain the goaf is urgently needed. Channel wave seismic technology is suitable for coal mine goaf detection because it has many advantages, such as long transmission distance, high resolution. Because coal seam thickness affects the wave propagation, firstly, we carry out numerical simulation under the condition of coal seam thickness variation in the goaf. Secondly, we analyze the channel wave field characteristics of the goaf. Thirdly, we pick up the dispersion curve of transmitted channel wave. Lastly, we discuss the effects goaf makes on channel wave and imaging condition under the variation of the coal thickness. The results show that, the Airy-phase velocity of channel wave decreased as thickness of coal seam increases, and the dispersion strengthens as Wave propagation distance becomes longer. Firstly, seismic reflection survey is carried out in the target area: 15,030 working face of Xin'an coal mine. Through the analysis of dispersion, spectrum, direct wave's velocity and travel time of the shot-gather records, we recognize the reflected waves from the goaf. The goaf boundary is imaged by the Kirchhoff migration method. Combining the other results of geophysical exploration with the known geological data we geologically explain the imaged results.