Study On The Breaking Law Of Thick And Hard Roof And The Control Of Ground Fracturing

The thick and hard roof is thick and strong.As the exposed area of the roof in coal seam mining increases and is not easy to collapse,the collapse of the large step roof will cause strong mining pressure on the working face and cause safety accidents.IIn order to solve this kind of problems,according to the physical and mechanical characteristics of coal and rock mass in the 8106 face of Tashan Coal Mine in Datong,numerical simulations and field experiments are carried out to study the breaking law of thick and hard roof and the weakening technology of ground fracturing.Analyzed the distribution law of the pressure step,stress,displacement,and vertical stress of the coal seam when the thick and hard roof broke,and concluded that the thick and hard basic roof is the main reason for the strong rock pressure in the working face.Based on the theory of fracture mechanics and fluid-solid coupling,using the secondary development of ABAQUS software to realize the global embedding of the matrix network,a numerical model of the coupling of coal seam excavation and hydraulic fracturing was established,and the thick and hard basic roof before and after the control of surface hydraulic fracturing was analyzed.The distribution of cracks and the changes in ground stress reproduce the fracture process of the rock mass after coal seam excavation;the distribution characteristics of coal seam stress before and after the control of surface hydraulic fracturing was analyzed.The distribution of cracks and the changes in ground stress reproduce the fracture process of the rock mass after coal seam excavation;the distribution characteristics of coal seam stress before and after prefabricated cracks of different shapes are compared and analyzed,with the goal of reducing the working pressure,the hydraulic fracture spacing is optimized and the control effect is Carrying out evaluation and analysis,the above-mentioned research work and results are as follows:(1)Based on the theory of fracture mechanics and fluid-solid coupling theory,a numerical mechanics model for the fracture of thick and hard roofs was established,and the laws of rock pressure for the fracture of thick and hard roofs were simulated,and it was clear that the fracture of thick and hard basic roofs caused coal seam work.The main reason for strong mining pressure on the surface.(2)Through orthogonal experiment and regression analysis method,the influence degree of each factor of thick and hard basic roof on working face is analyzed,and the formula for predicting basic roof pressure grade by primary and secondary factors is fitted.(3)Analyzed the weakening mechanism of vertical fracture surface and horizontal fracture surface caused by ground fracturing,and established a numerical simulation model that couples coal and rock mass excavation and hydraulic fracturing prefabricated fractures,and analyzed the difference of ground fracturing The weakening effect of the fracture surface provides a theoretical basis for ground fracturing technology.(4)The field test of the thick and hard roof of the 8128 working face in Datong mining area was carried out.According to the research results of the paper,the fracturing method was determined,and the effect of the ground fracturing was carried out in terms of the crack propagation law and the weakening characteristics of the mineral pressure.verification.