Research And Application Of Cracking And Increasing Through High-Pressure Air Blasting Technology Applied In Low Permeability Coal Seam

Many coal seams in China's coal mining areas have the characteristics of high gas content,large ground stress,poor gas permeability and soft coal.The coalbed methane extraction rate is low,which is easy to cause gas disaster accidents.How to increase the permeability of coal seam and improve the extraction effect of coalbed methane has important theoretical significance and practical value for improving the development and utilization of coalbed methane in coal mines and preventing the occurrence of coal mine gas disasters.In this thesis,theoretical analysis,numerical calculation,experimental research,product development and other methods are combined with the actual situation to carry out research on high-pressure air blasting cracking and anti-reflection technology in low permeability coal seam.Through the high-pressure air blasting test,the gas migration law of different coal bodies was studied,the mechanism of high-pressure air blasting cracked coal seam was explored,and the high-pressure air blasting cracking complete equipment was developed,which has a universal applicability,high intelligence and good operability.High-energy gas blasting cracking and anti-reflection technology and equipment with high applicability and high degree of mechanization provide technical support for the development of coalbed methane in coal mines in China and the improvement of coal mine safety production status.Firstly,by analyzing the structural characteristics of coal,the characteristics of gas flow in coal,the process of high-pressure air blasting and the influence of crack propagation,the mechanism of high-pressure air blasting cracked coal seam is studied.The essence is blasting stress wave,high pressure gas and coal.The physical properties,gas pressure,ground stress and other factors,the coal body cracking,expansion,bifurcation,crack arrest process;Secondly,using the self-built high-pressure gas blasting test platform,the gas blasting test is carried out on the specimens under different gas bursting pressure,confining pressure and strength conditions:the coal specimens are broken and broken under the action of high-pressure air blasting.A large number of fissures,coal permeability has been significantly improved;burst pressure is a key factor affecting the anti-reflection effect;for low permeability and hard coal,high-pressure air blasting cracking effect is significant.Thirdly,based on the theory of coal-body elastic-plasticity,gas-solid seepage theory and damage analysis theory,the numerical model of high-pressure air blasting fractured coal is constructed.The numerical calculation is carried out by COMSOL Multiphysics finite element software.The results show that high-pressure air blasting is adopted.The method of rupturing the coal body can effectively break the crack in the coal-rock medium,contribute to gas desorption and extraction,and verify the feasibility of using high-pressure air blasting to improve the permeability of the coal seam.The strength of the coal seam and the stress of the ground are high-pressure air.The crack propagation effect of blasting impact has a significant effect;the choice of blasting hole spacing has a significant impact on the coalbed methane drainage effect.According to the crack propagation simulation calculation,the arrangement of the extraction drilling hole should be centered on the blasting hole,and the maximum extraction radius is 2.5m.Finally,based on theoretical analysis and numerical calculation,combined with the actual situation,a new type of underground mobile high-pressure air pressure pumping station was developed,and a complete set of high-pressure air blasting equipment was developed and remote control was realized.It was carried out in the well of Dingji Coal Mine in Huainan.Industrial test,the actual output pressure of high pressure air pressure pumping station is up to 65MPa,the natural attenuation coefficient of borehole gas emission is reduced by 94%after blasting and the blasting effect increases by 141.04%?400.65%.The range reaches 5m,the coal seam permeability coefficient is increased by more than 50 times,and good economic and social benefits have been achieved.It has opened up a new way for the low permeability coal seam anti-reflection technology,and the research results have broad promotion and application value.There are 104 figures,23 tables and 175 references in this thesis.