Study on the Method for Determining Dangerous Zones of Coal Self-Ignition in Gobs in a Fully Mechanized Top-Coal Caving Face

Based on the heat output of coal and the rate of oxygen consumption tested by the big coal spontaneous combustion experiment unit, and through determining oxygen concentration distribution in a gob, the rule of distribution for air leak intensity in gob is deduced. In view of the conservation principle of energy and real distributions, such as coal thickness, air leak intensity, oxygen concentration, the terminal parameters resulting in coal self ignition are calculated, and the necessary condition determining the dangerous zone of coal self ignition is established. According to the width of temperature rise zone and the shortest period of coal self ignition, the least mining velocity resulting in coal self ignition can be calculated, and the sufficient condition determining the dangerous zone of coal self ignition is established. Applied to the 2 D mathematical model of coal self ignition, the shortest period of coal self ignition is obtained under actual mining conditions in the dangerous zone of coal self ignition in a gob.