A method to identify coal spontaneous combustion-prone regions based on goaf flow field under dynamic porosity

Abstract Once the residual coal occurs spontaneous combustion in mine, it will cause a fire accident resulting in heavy personal injury and property damage. So it is of great significance for mine safety to quickly determine the location of dangerous areas of residual coal spontaneous combustion. A fracture-pore evolution model of goaf is constructing, the pore evolution and porosity distribution in a goaf overburden are simulated by the distinct-element modeling software Particle Flow Code (PFC). By compiling the extracted porosity distribution data into Fluent using a User Defined Function (UDF), a dynamic porosity model of goaf is being proposed. With this model, the air flow field in a goaf is simulated, and the regular air distribution pattern in that area is obtained. Using oxygen concentration as the indicator, the residual coal spontaneous combustion-prone region in the goaf is identified, and the results are basically the same as those determined from real mine measurements. The consistency in results validates that the residual coal spontaneous combustion-prone region can be accurately and reliably identified by investigating the goaf flow field distribution under consideration of porosity dynamics. Our approach offers a new concept and method with a higher precision of results for identifying residual coal spontaneous combustion prone-regions in goafs, and it provides the basis for preventing and extinguishing goaf fires and guarantees the mine safety.