Abstract
How to quickly eliminate outburst in long-distance through-coal seam tunnels is one of the major challenges faced by the tunnel industry in mountainous areas. Compared with coal mine rock crosscut coal uncovering, the work surrounding the rock of through-coal seam tunnels has a high degree of breakage, large cross-section of coal uncovering, and tight time and space. In this paper, a method of networked slotting in long-distance through-coal seam tunnels for rapid pressure relief and outburst elimination is proposed. Based on this method, the corresponding mathematical governing equations and numerical simulation models have been established. The optimal borehole arrangement spacing and the slot arrangement spacing obtained by numerical optimization are 2.85 m and 3.1 m, respectively. Field gas production data of through-coal seam tunnels show that compared with the traditional dense-borehole gas extraction, the method of networked slotting in long-distance through-coal seam tunnels for rapid pressure relief and outburst elimination can shorten the extraction time by about 66%, the net quantity of peak extraction is increased by 3.55 times, and the total quantity of gas extraction when reaching the outburst prevention index is increased by 1.26 times, which verifies the feasibility of this method and the reliability of numerical simulation results. This study could be used as a valuable example for other coal deposits being mined under similar geological conditions.
Highlights
With the rapid development of the national economies of the world, high-speed tunnels and railways have formed a comprehensive transportation system for modern cities to communicate and connect with each other
When excavating and uncovering coal in gas tunnels, it is necessary to consider the similarities and differences between long-distance through-coal seam tunnels and coal mine roadway driving according to specific engineering conditions, take targeted outburst prevention measures with low damage to surrounding rocks on the premise of accurately predicting outburst dangers, and make timely adjustment according to the characteristics of dynamic behaviors to ensure safe and rapid uncovering of coal seams
In order to verify the correctness of the numerical analysis results, hydraulic slotting extraction was carried out at the optimized 2.85 m along-seam borehole spacing and 3.1 m slot spacing for the 60 m pretunneled through-coal seam tunnel
Summary
With the rapid development of the national economies of the world, high-speed tunnels and railways have formed a comprehensive transportation system for modern cities to communicate and connect with each other. When excavating and uncovering coal in gas tunnels, it is necessary to consider the similarities and differences between long-distance through-coal seam tunnels and coal mine roadway driving according to specific engineering conditions, take targeted outburst prevention measures with low damage to surrounding rocks on the premise of accurately predicting outburst dangers, and make timely adjustment according to the characteristics of dynamic behaviors to ensure safe and rapid uncovering of coal seams. This requires that the preextraction of gas in gas tunnels before mining needs the characteristics of less disturbance to the surrounding rocks of roadways, short gas emission period, high efficiency, etc. Through numerical analysis and field test verification on key parameters of borehole arrangement spacing and hydraulic slot arrangement spacing for preextraction of gas tunnels, it is intended to obtain the optimal borehole arrangement spacing and slotting that meets the gas preextraction index
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