Study on the reasonable number of demolished pre-drainage boreholes drilled along coal seams.

In order to determine the reasonable number of demolished pre-drainage boreholes drilled along coal seams, against the backdrop of actual coal mines, the paper considered the comprehensive impact of pressure-relief ranges of the coal seams in front of the mining face, the advance rate of the working face, and drainage radius on the number of demolished pre-drainage boreholes. By means of numerical simulation and engineering verification, the paper determined the pressure-relief range of the coal seams in front of the mining face as 8.0m. Based on in situ mining progress and the relative production program, on the premise that the advance rate of the mining face remained constant, the paper analyzed the number of boreholes to demolish in front of the mining face at different gas pre- drainage time. The result showed that: when the gas pre- drainage time was defined as 30d, 60d and 90d, respectively, and the daily advancing distance of the working face was set as 3.6m at the same time, the number of boreholes to demolish was calculated to be 3, 3 and 2, respectively. This research result may act as a guidance to the reasonable deployment of mining programs in the coal mine, and may coordinate underground mining and gas extraction. It can also help realize coal seam outburst elimination and safety production to the greatest extent at the same time when economic benefits are maintained. [ABSTRACT FROM AUTHOR]