Determination and prevention technology for spontaneous combustion in goaf during negative pillar mining in steeply inclined coal seams

WANG Yu; WEI Gaoming

doi:10.11799/ce202601015

Abstract：To address the issue in steeply inclined coal seam mining where the layout of negative coal pillars in roadways,while effective in avoiding rockburst,tends to create air leakage channels with surrounding goaf and subsequently induce spontaneous coal combustion,the 412W working face of Huafeng Coal Mine was taken as the research subject.We systematically analyzed the mining characteristics and spontaneous combustion risks in the goaf of steeply inclined faces with negative coal pillars.Using a combined approach of field observation and numerical simulation,we investigated the multi-physical field coupling among temperature,pressure,and gas concentration in the goaf,accurately delineated spontaneous combustion hazard zones,and ultimately proposed a targeted prevention and control strategy for such mining conditions.Results show a significant pressure difference exists between the intake and return sides of the goaf,promoting air leakage channel development.Connectivity with adjacent goaf further expands the leakage scope.Major leakage zones are concentrated between supports of the 412W working face and at the return airway corner,with an air leakage rate of approximately 146.56 m3/min from the rear goaf into the working face,and about 78.76 m3/min from the goaf of 411W working face into the upper gate road of the 412W working face.Based on these findings,an integrated prevention system combining high-level borehole injection of composite gel and cyclic nitrogen injection into the goaf was established.Through the dual mechanisms of oxygen isolation/sealing and inerting/cooling,this system effectively curbed the spontaneous combustion hazard,providing technical support for safe mining in steeply inclined faces with negative coal pillars.