Formation mechanism and prevention technology of spontaneous combustion occurred in overburden goaf in contiguous seams

Based on the theoretical study and site practices on the spontaneous combustion prevention and control in the contiguous seams, taking the oxygen concentration control as the key, the paper provided the comprehensive prevention and control technology of the spontaneous combustion occurred in the overburden goaf with the multi point monitoring, automatic feedback and nitrogen injection mainly. The theoretical analysis and the numerical simulation were applied to study the induced mechanism of the coal spontaneous combustion in the overburden goaf caused by the fracture development in the mine roadway roof. From a view of the oxygen concentration control, a simulation analysis and the site practices were conducted on the prevention and control of the coal spontaneous combustion occurred in the overburden goaf. The study result showed that a large area air leakage and the oxygen supply caused by the fracture development in the mine roadway roof was the important incentive to cause the coal spontaneous combustion in the overburden goaf. The coal spontaneous combustion danger zone was located in the roof falling delta area of the top slicing and near the mining terminal line. With the air leakage intensity increased, the coal spontaneous combustion danger zone would be expanded to the air return side steadily. In comparison with the conventional multi point nitrogen injection method, the multi point automatic feedback technology could reduce the nitrogen consumption over 36%. Meanwhile,the accurate positioning of the high air leakage point and the dynamic monitoring of the regional coal oxidation process were realized. The site practices showed that the comprehensive prevention and control technology with the multi point automatic feedback could realize the feasibility to have the optimized distribution of the nitrogen injection volume and the recognition and control of the high air leakage point.