Analysis On Evolution Of Damage And Gas-solid Couple Law In Coal-rock By Mining

As the drilling or excavation disturbance coal, coal-rock experience from aroundthe unperturbed state to produce the original injury, fractured extended until the coalcrushing stages, structural properties, mechanical behavior and flow characteristics ofcoal nature have taken place changes, coal can not be simply seen as a particularmedium, medium coal and rock properties directly related to lesion size.Based on rock mechanics, fluid mechanics, and other related theories, damageand fracture characteristics for the coal and rock, introducing strain injury variableswithin variables derived corresponding elastic damage constitutive equations, andbased on the effective stress principle, derived under the gas-solid coupling damagecoal and rock deformation equations. Also according to the size of coal and rock todetermine the degree of damage in the basic form of coal gas migration, namely theproliferation of sports, sports seepage, and seepage diffusion coupled motion, theestablishment of a gas-solid coupling of gas seepage under the coal and rock damagecontrol equation defines gas-solid coupling variables associated with the damagevariable. Based on this theory, the paper is derived to calculate the gas flow in coaland rock damage the basic equations and finite element and using FORTRANlanguage to complete the corresponding gas-solid coupling analysis of coal and rockdamage finite element program development. In this paper, the use of this program forthree projects carried out numerical examples:(1) For gas drainage drilling process was simulated. The results show that: withthe increase of gas pumping time of mining, coal seam permeability increases, gradualoutflow of gas to drilling, gas drainage effective radius increased.(2) The use of finite element program developed for a single seam miningprocess was analyzed. The results show that: with the face advance from20m to100m, work injury front side coal scope of4.3m to33.5m, the maximum damage inthe region to increase the penetration of2-3orders of magnitude; with the faceforward, gas the scope of the flow increases, the work front side of the gas pressureand its gradient decreases.(3) The use of finite element program developed, calculated and analyzed by aprotective layer damage distribution and evolution of the field and seepage fielddouble protective layer under the conditions of Ulan Coal Mine. The results show that:the protective layer after mining, the lower strata appear Gob expansion cracks, roof strata, appears to be a protective layer of tension cracks, resulting in greater damage,significantly increased coal and rock permeability, is the effect of the protective layerof gas relief obviously, from the coal seam gas gradually flow into the rock, isconducive to the formation of the gas be drained.The overall results show that the paper establishes the gas-solid coupling theoryand damaged partitions is more consistent with the actual project.