| The coal and gas outburst is one of the most serious disaster in coal mine safety production.With the increasing of mining depth,the outburst danger is more and more serious during the tunneling of coal seam.The traditional outburst prevention methods can not meet the needs of the safety production in coal mine.Therefore,this paper proposes the use of hydraulic punching technology to eliminate stress and gas outburst prevention,the main research contents include the following aspects:1.The establishment of the force model of coal and gas outburst in coal seam tunnel,the thesis analyzes the impact factors in the development process of outburst.Based the Mohr-Coulomb yield criterion,the stability of the stress-released zone is analyzed,and the thesis points out that trying to release coal stress and exhaust gas adequately is the effective way to extend the width of the stress-released zone and eliminate outburst risk.Then the structural characteristics of coal are analyzed,the structure of coal is divided into pore and fissure structure,and through the analysis of the permeability of coal,the coal seam permeability function is introduced and the factors that influence the infiltration capacity are introduced.2.Based on the hydraulic punching technology and the mechanism of increasing penetration,the main characteristics of hydraulic punching water jet are analyzed.Then,based on the momentum theorem,the formula of the total blow force of the water jet on the surface of the coal body is deduced.At the same time,the combat force and the target parameters of the jet and the basic parameters of the jet are summarized.Between the empirical equation.And then analyze the process of gas from desorption to escape to cutting seam slot after stress-released,which took the way of “desorption-diffusion-seepage” into the cutting seam slot.3.The influence of the nozzle type and parameters on the jet characteristics is analyzed and the design and calculation of the hydraulic punching nozzle structure are carried out,and the hydraulic punching nozzle body is designed.And then the nozzle water jet pressure and hydraulic punching coal pressure was calculated,and finally determine the size of the nozzle structure.4.The FLUENT software was used to simulate the internal flow field of of the hydraulic punching nozzle body and the pressure relief effect after hydraulic punching was simulated by FLAC3 D software.The effect of hydraulic perforation is mainly reflected in the following: First,out of a large number of coal,providing sufficientspace for the expansion of coal deformation.The stress spread around,play local relief role.Secondly,in the course of the out of the coal out of a large number of gas,due to the expansion of coal deformation,coal permeability increased,expanding the radius of gas extraction,to achieve the desired extraction effect.Finally,the punching hole also increases the bare surface area of the coal body,forming a large number of cracks around the hole,increasing the pumping time per unit time and shortening the pre-pumping time.5.In the Daping Mine working surface,the hydraulic punching technology was tested in the field,and the effect of the amount of coal produced after the hydraulic punching and the outburst of the discharged gas were observed.After the punching is completed,the stress of the coal body is released within a certain range around the hole,and the gas emission effect is remarkable.The displacement of the coal in the working face is shifted and the concentrated stress is transferred to the deep,and the danger is reduced or eliminated.In summary,as a kind of effective outburst prevention measure,through trying to release coal stress and exhaust gas adequately,the technology of the hydraulic punching technology plays a key role for outburst prevention. |
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