Pressure–Relief Gas Cooperative Drainage Technology in a Short-Distance Coal Seam Group

Abstract

The gas in a coal seam is a clean energy source, but it is also the main cause of gas accidents during the mining of mineral resources. There is a large pressure–relief gas influx in the upper and lower adjacent layers of 1211 working face in the Wanfeng Coal Mine in Jinhui, Shanxi Province, China. Based on the evolution law of overburden fractures, the collaborative pressure–relief gas extraction mode of “directional drilling in the gas-conducting fractured zone + staggered buried-pipe in the goaf” is innovatively proposed. The research results indicate that, under the influence of gas pressure gradient and buoyancy, a gas–concentration enrichment zone is formed at a distance of 10.8–24.1 m from the boundary of the mining layer. After optimizing the arrangement of roof directional-drilling layer and layer position, as well as the staggered distance of buried pipe drainage, the average gas-drainage rate reached 83.2% during the test working face, and the gas volume fraction in the upper corner was maintained below 0.7%. This mode can greatly improve the efficiency of mining mineral resources and gas energy utilization in short-distance coal seam groups, while solving the problem of gas accumulation in the upper corner caused by negative pressure of air flow during the mining process of mineral resources.