Influence of Negative Pressure in High Level Roadway on Coupling Hazard Prevention of Gas and Coal Fire in Gob

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.