Air Leakage Law and Prevention Technology of Coal Spontaneous Combustion in the Goaf of “Isolated Island” Fully Mechanized Caving Face

Abstract

ABSTRACT The coal pillar along the goaf of the completely mechanized caving face of “Isolated Island” is severely damaged, with complex air leakage and a high risk of coal spontaneous combustion. In order to research the law of goaf air leakage in “Isolated Island” working face and effectively control the hidden threat of coal spontaneous combustion in goaf, it is necessary to investigate the goaf air leakage law. In this work, the 3302 “Isolated Island” entirely mechanized caving face of Jining No. 2 Coal Mine in Shandong province, China, served as an example. SF6 tracer gas air leakage measurement was utilized to identify the air leaking route in the goaf. In conjunction with the numerical modeling, the air leakage route surrounding the goaf was evaluated to establish the coal spontaneous combustion risk region, and the targeted prevention and controlled ways of coal spontaneous combustion were proposed. The results indicated that the primary source of air leakage was the seepage of air flow through the working face to the rear goaf and the diffusion to the adjacent goaf through the broken coal pillar. The risk area for coal spontaneous combustion was 40–80 m behind the rear goaf and 50 m within the coal pillar of the adjacent goaf. Regarding this region, the comprehensive prevention and control strategies of plugging and oxygen reduction, inerting and cooling, monitoring and forecasting were proposed. In addition, the fire prevention and extinguishing system combining slurry spraying, sodium silicate, and liquid CO2 injection was designed at both ends of the 3302 track and haulage roads. Using field measurements during the working face mining process, the corresponding methods for reducing the CO volume fraction in 3302 return air roadway and air return corner effectively prevented and controlled the hidden danger of coal spontaneous combustion in the goaf and ensured the safety of working face mining. This research developed a new technology for the prevention and management of coal spontaneous combustion in the goaf of the “Isolated Island” working face.