Determination of sealing depth of in-seam boreholes for seam gas drainage based on drilling process of a drifter

摘要

In order to determine a reasonable sealing depth for seam gas drainage boreholes, an innovative method is proposed to study the geological conditions in the coal seam by monitoring the response of the drift while drilling the boreholes. Based on the investigation of the in-situ tests on the drift, we found that the idle pressure of the hydraulic motor, which features a rapid increase at the depth of approximately 14 to 16 m from the roadway wall, appeared to be suitable for characterizing the coal mass condition. Then, a numerical simulation was performed to investigate the reason for the response of the idle pressure. It reveals that high stress and gas pressure are the main factors accounting for the rapid increase of the idle pressure. Accordingly, the rapid increase of idle pressure becomes an indication for high stress and gas pressure.