| As the first coal producing country in the world,coal output is related to our economic development and the sustainable development of energy.The safe production of the coal industry is one of the important factors to ensure the rapid economic development of our country.Coal and gas outburst is one of the key prevention objects in the process of coal mining.aiming at the problem of coal and gas outburst in high gas coal seam,hydraulic antipermeability technology has the advantages of easy operation,short working cycle and high safety factor.Hydraulic anti-penetration technology has achieved good results in many mining areas,but due to the different actual geological environment of each coal seam,no systematic technical scheme has been formed,such as borehole layout,technological process,selection of flushing coal quantity and so on.therefore,the technology of hydraulic antireflection and enhanced borehole extraction needs to be further studied.Aiming at the conditions of high gas coal seam and taking 11223 working face of Paner Coal Mine as the test site,this paper studies from the following aspects through the combination of theoretical analysis,numerical simulation and field test.? According to the definition of fracture structure and porosity of coal body,the dynamic change equation of porosity under the influence of mining work is obtained from the factors of changing porosity,and then the dynamic change equation of permeability is obtained by Kozany-Carman equation.The occurrence state of coal seam gas and the calculation of coal seam gas content are analyzed,and the influence factors of coal seam gas content are studied,which provides theoretical help for the study of coal seam gas drainage.The hydraulic antireflection mode is analyzed,and from the analysis of the types of water jets and the characteristics of different water jets,it is concluded that the hydraulic punching water jet is an ordinary continuous high pressure water jet.After ejecting the nozzle,the water jet is divided into dissipation section,basic section and core section according to its length.The properties of water jet in each stage are analyzed,and the calculation formula of water jet pressure on coal body is obtained,and the pressure change of water jet on different coal wall is analyzed.The coal-breaking mechanism of hydraulic punching is analyzed,and the key factors affecting the coal-breaking effect of hydraulic punching are obtained.? Combined with the field test of 11223 working face in Paner Coal Mine,after the gridding extraction boreholes are arranged in the west second section of group A coal,the gas pressure at the distance of 4m from the drainage boreholes decreases to 0.74 MPa within28 days,which is 1m higher than that under the condition of single boreholes.COMSOL Multiphysics numerical simulation software is used to simulate the variation of coal seam gas pressure with drainage time under the arrangement of single and gridded boreholes.The results show that the effective extraction radius of boreholes is up to 4m under the arrangement of gridded boreholes,and about 3m under the condition of single boreholes.The rationality of the model is verified,the on-site drilling arrangement scheme is optimized,and the construction efficiency is improved.? With the combination of field and software simulation,the reasonable gridding drilling model is applied to hydraulic antireflection simulation to simulate the effective extraction radius and influence radius of boreholes after hydraulic punching.The influence of hydraulic punching coal output on pressure relief and outburst prevention of coal seam is simulated,and the result is that when the coal output reaches 1t/m,the strengthening and outburst elimination effect of hydraulic punching is the most obvious in a certain time range.Combined with the site layout of 11223 high drainage roadway according to the optimized drilling network,it is found that before and after hydraulic punching construction,the gas extraction pure quantity and gas concentration are changed at different places from the punching position,and the gas drainage speed is increased by 2.5 times at 2.5m from the punching position.the influence lasts for 6 days,and the maximum gas drainage speed at5 m and 6m can also reach 1.5 times of the original gas extraction speed.The result of good effect of pressure relief and outburst prevention in coal seam can be obtained,and the feasibility of hydraulic punching enhanced outburst elimination technology can be verified.Figure 31 table 8 reference 42... |
PDF Full Text Request