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With the increase of coal mining depth, the gas content in coal seams could also become larger and larger, which could suddenly cause an inrush of gas into the longwall mining face. It is very dangerous for miners' safety in the underground. The U-shaped ventilation pattern of longwall mining face that underground coal mines currently use is not enough to deliver sufficient air quantities to dilute gases in mining faces, which could result in the gas concentration over the required celling limit by government laws. Thus, the mine must stop production. In this paper, the high level roadway (HLR) is designed and the U + HLR new ventilation pattern is proposed to control gas emission in a longwall mining face. using computational fluid dynamics simulation (CFD) software, the flow field and gas transportation in the mine gob are studied. The optimized ventilation parameters are summarized. It is found that the best vertical distance of the HLR is 35 m over the coal seam and the horizontal distance is 25 m from the air return roadway. It is recommended that the negative suction pressure design of the high level roadway should be ranged from 9000 pa to 10000 pa. Based on the study outcomes, the gas emission could be well controlled in mining faces and avoid any gas disaster accidents. [ABSTRACT FROM AUTHOR]

The negative pressure of high level roadway extraction is one key factor which can influence coal spontaneous combustion and the gas extraction, to determine the reasonable negative pressure of extraction, combined with the actual situation of gas over-limit and spontaneous ignition in 401102 fully mechanized caving face of a mine, ANSYS numerical simulation and field measurement method were adopted to study the influence of negative pressure of extraction in high level roadway on gas extraction effect and “three zones” distribution of coal spontaneous combustion, and engineering practice was carried out. The results show that negative pressure can result in coal spontaneous combustion. When negative pressure increases from 0.5 kPa to 3.5 kPa, gas extraction scalar increase by 21.02 m3/min, compared with the “U” ventilation mode, when the negative pressure of the high roadway was 3 kPa, the width of the oxidation heating zone increased by 17 m on the inlet side, and decreased by 14 m in the middle and 11 m on the return side; the method of defining the range of reasonable negative pressure of extraction was proposed, and the fluctuation range of negative pressure was determined between 0.951 6 and 2.558, and the optimal point was 2.558 kPa. When high level roadway is adopted in coal seam, the reasonable setting of negative pressure can ensure the coupling prevention and control of gas and coal spontaneous combustion in goaf.