Research and prevention of upper remaining coal spontaneous combustion induced by air leakage in multi-inclination regenerated roof: A case study in the Luwa coal mine, China

Coal is a widely used fossil energy. The multiple mining and stratified mining technology effectively improves its utilization. However, the regenerated roof formed in this process induces coal spontaneous combustion by air leakage. Therefore, by the governing equation of fluid dynamics, the remaining coal spontaneous combustion characteristics of regenerated roof were studied, the risk area was delineated by numerical simulation and field experiments, the composite fire extinguishing technology was proposed. The results showed that air leakage intensity and coal particle size were easily affected by mining disturbance, especially near the surface of the roadway, under the influence of concentrated stress, the particle size of coal decreasing, the cracks penetrating, the air leakage intensity increasing. When the inclination angle of the regenerated roof increased, oxidation-zone was easy to form near the turning point. The air leakage crack near the surface of the roadway increasing, forming a cooling-zone, the fire-zone was formed behind the turning point, which had a low wind speed, creating a good heat storage environment. The decline in index gas concentration and fire-zone temperature illustrated that the composite fire extinguishing technology has a good prospect in controlling the coal spontaneous combustion of regenerated roof. •Turning point of Multi-inclination regenerated roof is more dangerous.•Dynamic pressure difference is the main cause of air leakage in inclined roof.•Support beam structure of roof increases the risk of coal spontaneous combustion.•Coal fire can be controlled by regional plugging composite technology.