Experimental Research And Numerical Simulation Of Gas Migration Rule In Mining-induced Fractures Field

Gas migration rule in mining-induced fractures field is the significant foundationof realization of deep simultaneous exploitation of coal and gas. This paper took7#coalof Datong first Mine as the research object. An experimental researh on the mechanicalproperties of containing-gas coal rock and gas permeability was carried out by triaxialstress thermal-hydro-mechanical coal containing gas permeameter. A mining fissurefield engineering simplified three-dimensional rectangular ladder geometry model wasestablished. The gas diffusion mathematical model was constructed by using thetranslational diffusion equation and Fick diffusion theorem. The gas migration rule inMining-induced fractures field to Y-ventilation condition was made simulated withCOMSOL Multiphysics by comparing with the U-ventilation finally, gas migration andconcentration distribution rule in mining-induced fractures field of two ventilationconditions were analysised.The main research results were as follows.(1) From the microstructure of coal seam, gas occurrence state in coal seam,mining-induced fracture field characteristics and the formation process, the permeabilitycharacteristics of gap in unloading of coal and rock, the gas flow characteristics wastheoretically analyzed. Rectangular terraces of fissure development in three dimensionalproject model was used to describe the mining strata. The rectangular terraces wasdivided, the rule of fracture field in goaf under mining was described more accurately.(2) Briquette full stress-strain gas seepage experiment under different gas pressureand confining pressure gave mechanical properties and permeability rule under thecondition of triaxial. Under certain confining pressure, triaxial compressive strength ofbriquette reduced with the increase of gas pressure, the permeability transformation lawof briquette was not a monotonous with the increase of gas pressure. triaxialcompressive strength of briquette increased with the increase of confining pressure, thepermeability decreases monotonously with the increase of confining pressure, under thecondition of a certain gas pressure. The curve of permeability-axial strain curve wasthe "U" type, permeability decreased at first and then increased with axial strainincreases.(3) Compared with the U-ventilation,the working face gas concentration waslower in Y-ventilation,the gas concentration along the coal gradually rised from workingface to deep goaf.The gas concentration was higher and the shape of goaf gas equivalent plane distribution was closer to the space V with the farther distance from working face.the gas concentration was higher of the work face return airway in U-ventilation,theform of the gas concentration changes was regular, gas concentration changed fast.InY-ventilation,the gas concentration of face upper corner was0.26%, In U-ventilation,thegas concentration of face upper corner was6.62%, the problem of gas overrun was wellsolved in Y-ventilation.