Disaster-causing mechanism and risk area classification method for composite disasters of gas explosion and coal spontaneous combustion in deep coal mining with narrow coal pillars

In order to reduce the stress on the underlying coal seam and improve mining efficiency in deep coal mining activities, narrow coal pillars are often used. They are the main factor that increases the risk of coal spontaneous combustion in the goaf. Based on the on-site experiment and the experimental analysis in the laboratory, this paper adopted correlation coefficient criteria and safety principles to research the disaster-causing mechanism of such risk. It also classified and divided the studied area into different risk levels to effectively manage it. The results show the coal mass fractures generated by the movement of stress concentration points on the narrow coal pillars is the main factor that contribute to the increased spontaneous combustion in the goaf. The two main forms are gas explosion caused by CH4 flowing into the roadway and spontaneous combustion of residual coal caused by O-2 flowing into the nearby goaf. By adopting correlation coefficient criteria and safety principles, this paper selected two indicators, gas-impermeability of narrow coal pillars and risk degree of residual coal spontaneous combustion in the goaf to divide the whole narrow coal pillars and goafs into three areas, namely "Safe Area", "General Area" and "Dangerous Area". This can maximize safety benefits with the lowest cost and guarantee safe and efficient coal mining. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.