Characteristics and detection performance of the source of seismic while excavating in underground coal mines

Against a background of intelligent coal mines, seismic while excavating has become one of the key geological guarantee technologies for safe excavation in the mining face. It can detect hidden geological structures in real-time, in advance and finely, such as goafs, faults, and collapsed columns, effectively promoting safe and efficient excavation and production. Different from the widely used advanced detection technology of reflection in-seam wave, the vibration signal of the tunneling machine is used as the excitation source, which replaces the explosive source in conventional seismic exploration. It has the advantages of environmental frendliness, safety, low cost, recyclability and combined exploration and excavation. Great differences between the TBM(Tunnel Boring Machine) source and the explosive source in excitation mode, energy, frequency and bandwidth cause much attention to the former’s detection performance. By studying the focal mechanism, wave field characteristics, propagation distance and imaging accuracy of the seismic-while-excavating, its detection performance is analyzed in detail. It is considered that the in-seam wave and shear wave in the wave field of the seismic caused by excavation is sufficient, and can be used for advanced detection. The Y component has the advantage of better signal-to-noise ratio, but with the trend of reflection surface being considered in practical application; the Z component has more advantages with the same amount of equipment. The direct S-wave propagation distance of seismic-while-excavating can reach more than 700 meters, and the advance detection distance of S-wave 300 meters. The propagation distance of direct in-seam wave of seismic-while-excavating can exceed 400 meters, and the advance detection distance of in-seam wave 170 meters. At a normal excavating speed, the reflected waves can be superposed for 16 times. Compared with a conventional detection, the signal-to-noise ratio can be increased by 4 times, which effectively improves the detection accuracy. The performance parameters of the seismic-while-excavating technology will be further modified through a large number of application data.