Air-leakage Model and Sealing Technique With Sealing-Isolation Integration for Gas-drainage Boreholes in Coal Mines

Sealing of boreholes for gas drainage is crucial for ensuring efficient gas drainage in coal seams. In this paper, the damage to coal masses where roadways were excavated and boreholes were drilled was separately simulated to determine the distribution ranges of pressure-relief plastic and elastic zones. Furthermore, the factors influencing air leakage of boreholes were analyzed to determine three patterns of air leakages-air leakage, air leakage, borehole fissure due to roadway fissure zones, borehole fissure zones and materials in borehole-sealing sections, respectively. In addition, a model for the air leakage of boreholes was established, and the principle underlying the sealing of boreholes with sealing-isolation integration was illustrated to separately determine the reasonable borehole-sealing depth, the position and depth of slots, and the grouting parameters. The borehole-sealing techniques for different parame-ters were compared to verify the applicability of the borehole-sealing technique with sealing-isolation integration. The gas-drainage concentrations after drilling for 30 days showed that, compared with the test borehole sealed using the traditional technique, the initial gas-drainage concentration in the bore -holes sealed with sealing-isolation integration increased by 1.5-2 times, and the average gas-drainage concentration increased by approximately 2-3.5 times. (c) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.