Experimental Study On Evolution Rules Of Mining Fracture In Soft And Hard Interbed Based On Energy Dissipation

With the increasing of mining depth and intensity in our country,to strengthen coal seam gas disaster,and the "three high three low" characteristics of coal seam gas occurrence.The effect of the single gas extraction method is not very ideal,the use of gas drainage in pressure releasing area is the important direction of coal mine gas prevention and control in our country.The paper systematically summarized and reviewed plenty of achievements of the mining fracture and breaking law,rock fracture quantitatively described the fractal calculation,rock mass deformation and instability of energy analysis,it can get that mining fracture evolution process is the key to quantitative description mining-induced fracture evolution and distribution law based on energy.According to mechanical behavior of coal and rock in mining process,analysis the law of elastic energy density and dissipation energy density in the process of rock deformation and failure under different condition of uniaxial cyclic loading,loading rate,confining pressure,ratio of height to diameter,lithology.Get the energy conversion law in process of rock deformation and failure,accordingly,building damage constitutive equation based on energy dissipation,and establishing the energy yield criterion in the process of rock deformation and failure.By physical simulation experiment and FLAC3D numerical simulation,analysising the change of the mining fracture generation,development and distribution form,acoustic emission characteristics with soft and hard interbed.Get the effect of soft and hard interbed to the law of mining fracture evolution and distribution,stress distribution,acoustic emission characteristics,with the strength of lithological character,mining affected areas is decreasing,and the mining affected strength increasing.Through theoretical analysis,combining with physical simulation experiment and numerical analysis results,analysising the distribution of sliding resistance,due to the weight of rock layer,the vertical stress of upper srata,the friction between rock layers and adhesion stress between rock layers.Got the length of overhanging rock,based on rock layer mechanics and geometry size,determined the height of rock layer broken,after the certain advancing distance,optimized elliptical parabolic zone mathematical model.Obtained mining fracture distribution form mathematical equations.Based on the physical analog simulation experiment and numerical analysis results,analysising the mining fracture evolution process from the perspective of energy,obtained that rock length,fracture number and horizontal distribution equation of goaf compaction after rock layer broken,studied quantitatively the law of fracture density and fracture dimension distribution in goaf,namely overburden rock mining fracture distribution characteristics.Carrying out field industrial experiment with the use of microseismic monitoring system and drilling peep method in No.301 working face of tianchi energy limited liability company heshun country shanxi province.Analysising the three-dimensional spatial distribution law of microseismic events,the distribution law of fracture in the borehole drilled,establishing the mining fracture distribution form and charactors,further verify overburden mining fracture evolution and distribution law.The paper revealed the overburden mining fracture evolution mechanism,provided theory support for gas drainage in pressure releasing area,and provided some theoretical basis for simultaneous extracting of coal and methane.