Study On Damage And Law Of Coal Crack Expansion Around Gas Drainage Boreholes Under Uniaxial Loading

During the gas drainage process,the coal around the borehole is prone to instability and deformation under the repeated interference of external engineering stress and cracks appear,resulting in low gas drainage efficiency and easy occurrence of coal mine power disasters.And the law of crack propagation has important theoretical and practical significance of engineering application.This paper mainly uses the combination of theoretical research and experimental research,and uses the digital image correlation method to study the deformation and failure characteristics and damage and evolution characteristics of the coal surrounding rock under uniaxial loading.First of all,Synthetically uses digital image correlation method and elastic theory of coal rock surface inversion strain stress analysis around gas drainage.The appropriate mechanical model and damage mechanics theory are selected to study mechanism of Coal damage around gas drainage boreholes,and the relationship between surface damage factor and stress and strain of coal samples was analyzed.The surface strain and damage of different samples of coal and rock damage are discussed.Secondly,The system carried out damage tests of different coal and rock samples under uniaxial,single-stage and grading loading.Combined with VIC-3D to study the change of surface strain field of coal samples,the relationship between speckle damage factor,instantaneous strain,strain rate and crack growth rate is analyzed.According to suitable creep model of different coal samples and creep parameters effective stress relationships,Analysis Compressive mechanical properties of coal and rock mass creep law.with the coal of partial and overall around gas drainage boreholes.Then,Study on the surface deformation failure and crack expansion around the coal of gas drainage boreholes,through drilling test in the laboratory,non-porous under uniaxial loading test.The variation process of the surface damage factor,crack growth rate,stress and strain during the damage process of the surrounding coal rock mass under one-way loading is analyzed.Finally,Combined with the theory of damage mechanics,and the digital image correlation method was used to establish the mechanical model of surface damage and crack expansion around the coal of gas drainage boreholes under uniaxial loading.The variation of surface damage factor and fracture growth rate in the test is verified,which provides theoretical guidance for studying the mechanism of damage and crack expansion around the coal of partial and overall around gas drainage boreholes.