Application Study Of Deep Borehole Pre-fracturing Blasting Enhancing Permeability Technology To Seam Opening In Mine Shaft Of Xieqiao Mine

With the expansion of the scale of coal mining and the increase of mining depth,crustal stress and gas content increased,seam permeability lower,the danger of mine gas accident in coal such as coal and gas outburst greatly increased. Duing to limitations of the work site of the mine shaft uncovering coal, there are more particularity and dangerous, making it the danger of coal and gas outburst in a maximum degree,especially when exposing deep wells with high gas low permeability outburst coal seam becomes increasingly apparent.Therefore, how to increase coal seam permeability, improve the gas drainage rate, eliminating outburst risk has become an urgent problem.In this paper, through theoretical analysis, numerical simulation and method in combination with the engineering test, the application of pressure relief and permeability increasing technology in low permeability and high gas coal seam in the deep hole pre-splitting blasting was studied systematically, points out the different mechanical properties of coal and rock, control hole guiding role and influence of blast hole spacing and control the effect of blasting holes, made the following conclusions:1.The physical and mechanical properties of coal and rock blasting coal and rock porosity, density, density, gravity wave impedance and broken and so on are closely related;After blasting in coal and rock, the first shock formation, its decay quickly, little scope,but it consumes the most explosive energy, stress wave attenuation of time after the formation of the shock wave is relatively long, the larger scope, is the main area of coal and rock damage and destruction in the form of coal and rock into shear failure and pull stretch destroy two kinds.2.By discussing deep hole pre-splitting blasting pressure relief antireflection mechanism,analyses stress wave,control hole,detonation gas and coal seam gas pressure,in the role of crack propagation.Firstly, the stress wave acts on the coal and rock,producing radial compressive stress and tangential tensile stress,makes the coal produces crack;secondly,the reflected tensile wave formed in the control hole further increases the cracked area;Finally, high-temperature,high-pressure gas and coal seam gas detonation pressure together act on the gaping fissures of the cavity walls and cracks tip stress concentration,so that further expansion cracks and eventually formed a circle and secondary fractures,including fractures circle the complex fracture network.3.According to the well hole uncovering coal seam13-1scene situation,use three-dimensional dynamic finite element program LS-DYNA3D to establish numerical models that conform to the actual conditions;Through Numerical simulation of stress cloud crack picture of a single hole blasting,a single hole blasting of a single control hole and Two blast hole (different hole spacing)of a single control hole,reproduction of the stress wave propagation and attenuation law in the coal and rock,and expansion in the process of coal and rock fissures;When the two blast hole spacing4-6m,can make large amounts of coal and rock through fissures, blasting better.4.From the test results of uncovering coal seam13-1, the effect of deep hole presplitting blasting pressure relief antireflection test is obvious,significantly increases the permeability of coal,improves concentration and extraction volume of gas extraction,for the prevention and treatment of outburst of high gas low permeability outburst coal seam is a positive feasible solution.