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The techniques of stress relief mining in low-permeability coal seams and pillarless gob side retained roadway entry using Y-type ventilation and gas drainage systems were developed to control gas outbursts and applied successfully. However, as the mining depth increasing, parts of the gas drainage system are not suitable for mines with high gas emissions. Because larger mining depths cause higher ground stresses, it becomes extremely difficult to maintain long gob side roadways. The greater deformation suffered by the roadway is not favorable for borehole drilling for continuous gas drainage. To solve these problems, Y-type ventilation and gas drainage systems installed from a roof roadway were designed for drainage optimization. This system was designed based on a gas-enrichment zone analysis developed from mining the 11-2 coal seam in the Zhuji Mine at Huainan, Anhui Province, China. The method of Y-type gas extraction from different mine areas was applied to the panel 1112(1) in the Zhuji Mine. The absolute gas emission rate was up to 116.3 m3/min with an average flow of 69.1 m3/min at an average drainage concentration of nearly 85 %. After the Y-type method was adopted, the concentration of gas in the return air was 0.15 %–0.64 %, averaging 0.39 % with a ventilation rate of 2100–2750 m3/min. The gas management system proved to be efficient, and the effective gas control allowed safe production to continue.

Gas drainage from different mine areas: optimal placement of drainage systems for deep coal seams with high gas emissions