Study On Mining-induced Fractures Field Evolution And Gas Migration Rule

The overburden rock fissures evolution and pressure relief gas migration law is thecore technology of " coal and gas safety mining ", but also one of the coal green miningtechnology. This paper takes15th coal seam of10th mine Pingdingshan CoalmineGroup as the object, FLAC3Dand UDEC numerical simulation softwares are used toanalysis the overlying rock stress field in mining and overburden rock cavingdestructionthe and law of distribution of crack field, respectively. Project simplifiedmodel is extracted by analyzing the results of UDEC software simulation, the goafpressure relief gas distribution regularity in two different ventilation modes aresimulated by using COMSOL MULTIPHYSICS software, the following preliminaryconclusions:①The overburden rock breaking ionospheric law and the breaked shape,characteristics were analyzed and that a mining fractured rectangular ladder platformwhich can meet the precision engineering formed in entire overlying strata and therectangular ladder platform can approximate a non-homogeneous porous medium,which provides a theoretical basis for the study of gas migration law in the rectangularladder platform.②The permeability of coal specimen first decreases and then increases withincreasing axial strain during the complete stress-strain; coal specimen under thecondition of loading-unloading, the permeability of coal sample suddenly increased inreached peak strength of40%～60%, and then decreased slightly, then again increaserapidly in coal specimen destruction paragraph; under the same confining pressure andgas pressure conditions, peak intensity of coal specimen under the condition ofloading-unloading is low than which under conditions of conventional three axis.③The stress distribution law and plastic failure pattern of the overlying strata inseam mining are analysised by using FLAC3D. Looking along the coal seam strikeprofile as trapezoidal shape; looking parallel to the seam profile, the plastic zone of theroof that closer to the coal seam seem as the rounded rectangle circle, as the heightincreases away from the seam roof, plastic zone tends to oval.④The overlying rock caving morphology is analyzed by using the UDECnumerical simulation software. Based on UDEC simulation caving morphology diagram,combined with previous research, a three-dimensional diagram of mining fissure rectangular ladder platform is delineated out. Specificing to the object of this study, thescope, height and angle of fracture parameters of mining fissure rectangular ladder aredetermined.⑤Simulation results of COMSOL show: in the case of U-type ventilation systemconditions, gas concentration of face upper corner greatly exceeds the limits of1%; inthe case of U-type+towards high pumping lane, the guide action of high pumping laneto airflow high made the high concentration gas of goaf deep and face fresh air flowtowards high pumping lane and changed the distribution of the gas concentration andthe corner gas concentrations also dropped to less than1%.