Optimization and field practice of microseismic vertical positioning in near-level horizontal thick coal seams

In order to improve the vertical positioning accuracy of the microseismic system in the near-level horizontal thick coal seam, a scheme was designed to increase the height difference between the microseismic stations by installing the deep hole detector, and the space layout of the microseismic system station in the near horizontal thick coal seam was optimized; the numerical simulation of the optimal design theory combined with the engineering experiment method was carried out to study the theoretical feasibility of the installation of the deep hole geophone to improve the vertical positioning accuracy of the source, and it was verified by field practice. The numerical simulation results show that by increasing the Z coordinate of the station, the vertical positioning error in the vicinity of the station can be effectively improved. The field practice results show that the frequency of coal seam events and the proportion of microseismic energy received after the installation of the deep hole geophone increased by 10.42 percentage points and 6.64 percentage points, respectively. The frequency of roof events and the proportion of microseismic energy received increased by 11.58 percentage points and 12.73 percentage points respectively. Comparing the results of the same event, the deep hole detector was involved in event location, and the top event was vertical. The height is increased by 36.61 m and the maximum height is 92.64 m.The microseismic energy is also increased, with an average increase of 1 903.44 J and the maximum increase of the microseismic energy is increased by 9 457.39 J. The waveforms of the same event are compared, the deep hole detector is compared with the vibration waves received by the neighboring detectors are effective to the time difference. The installation of deep-hole geophones effectively improves the vertical positioning accuracy of the microseismic system for roof events, and provides guidance for the optimization of the microseismic network layout in the near-level coal seam.