Distribution of Methane and "Three zones" of Coal Spontaneous Combustion in Gob Under Stereo Extraction Method

The complex disaster of gas and coal spontaneous combustion is a major challenge in coal gob, especially under conditions of three-dimensional extraction. Taking the 15,101 mining face in Shigang Mine as the field background, COMSOL Multiphysics software was employed to construct models of airflow, methane migration, and stress distribution in gob under the stereo extraction method of "U+high-low level roadway." The range of oxidation zone was divided by combining the oxygen concentration and wind velocity field. The results showed that the methane can be discharged through the low-level airway and the return airway, and most of the methane at the top area in gob can also be discharged from the high-level roadway, indicating that the stereo ventilation was beneficial for methane dilution at both the upper and lower region. However, the oxidation zone in the middle of gob was the widest and closed to the mining face, it on the return side was narrower than intake side, and its distribution range was closer to the mining face. And finally, the range of the oxidation zone expanded with the increase in height in the vertical direction. These indicate the dangerous area for preventing gas and coal spontaneous combustion disasters in gob.