Study On The Leakage Law From The Surface To Goaf Of Shallow Coal Seam Group In Coal Mine

Mine shallow seam mining group is easy to communicate with surface cracks formed bymining influenced, that resulting in leakage channel between the surface and goaf. At the endof the over coal cell mining, when mining coal under cover, after being impact of coalmining, surface subsidence would be secondary, upper left pillar coal and further brokendown two coal mined-out area will communicate, plus surface leakage effects, when theoxygen concentration in air leakage serious mining area increased, the upper left ofspontaneous combustion of coal will have dangerous, and the lower impact of coal mining.This paper studies the status of shallow seam group mining a coal mine in northernShaanxi, and analysis of the causes and laws of shallow seam surface cracks and thecombined effects resulted in the serface leakage in shallow coal seam group suck as:thepressure difference of the leakage of air leakage between the source and sink, the case offractured roof strata, free diffusion of gas et al.On-site observations of surface leakage by using tracer gas SF6of face12401and understratified face22402, and modified the measurement methods and calculation method oftraditional SF6tracer gas flow rate of air leakage. That we get a seam group channel leakageand leakage of surface velocity field dataFor the actual site of air leakage characteristics and rules, numerical simulation by usingthe ANSYS FLUENT14.5software on the actual situation was simulated, that can drawdown the oxygen concentration distribution in coal goaf area of goaf12401and face22402and the leakage flow velocity distribution law. And than we modified the physical model,made the numerical simulation with the surface crack sealing physical model that simulate theoxygen concentration changes of the the up and down mined coal cell in the region. Instruct that the filled crack will reduce the oxygen concentration in the goaf and decrease with thelength of the oxidation temperature.