Research And Application Of The Influence Law Of The Angle Between Borehole And Coal Seam On Hydraulic Flushing Effect

The safe mining of coal mines in China was seriously threatened by the occurrence of coal and gas outburst disasters.Hydraulic punching,pressure relief,and dermeability enhancement measures can effectively improve the gas drainage effect,reduce the gas content in coal seams,and highlight the danger.However,the coal which is around the boreholes is gas preesure of different angles and the law of gas evolution are unclear,which severely hinders the efficient application of this technology in coal mine sites.Under this background,the evolution law of stress and gas parameters of coal and rock bodies around different boreholes in Liangbei Coal Mine was studied.The main results and conclusions obtained are as follows:According to the Hoek-Brown failure criterion,the stress distribution of the coal around the hole is analyzed,and the calculation equations for the radius of the crushing zone and the plastic zone are established.Based on the multiphysics coupling theory,combined with the seepage theory and elastoplastic mechanics,the borehole is considered The influence of the deformation of surrounding coal framework on gas flow establishes the fluid-solid coupling governing equation of gas-bearing coal body.According to the change characteristics of samples with different inclination angles under uniaxial compression,we conclude that with the decrease of the borehole inclination angle,under the same stress,the strain of the sample gradually increases,and the increase amplitude the compressive strength of the specimen has a linear relationship with the drilling angle.According to the actual coal seam geological conditions of Liangbei Coal Mine,COMSOL multi-physics simulation software was used for analysis.and analyze the stress and gas distribution evolution law of coal bodies around single-hole hydraulic punching under different coal output and different borehole inclination conditions.The simulation analysis results show that with the increase of coal production,the radius of the borehole increases,the influence range of the first principal stress increases,the gas pressure of the coal seam around the borehole decreases rapidly,and the pressure of coalbed methane decreases.The effective range of the borehole has increased,but the degree of increase has become smaller and smaller.The inclination of the borehole will have a greater iMPact on the effective range of the borehole.With the decrease of the inclination of the borehole,the effective range of the borehole will gradually increase,and the increase will gradually increase.Decreasing and increasing,between 60°and30°inclination,the effective range of drilling increases the fastest.When the borehole inclination is constant,the smaller the hole spacing,the more obvious the superimposed effect between the boreholes.With the increase of the extraction time,the gas pressure between the boreholes becomes lower and lower,but the decline gradually decreases,but because The mutual influence between boreholes,and the decrease of gas pressure between porous holes is larger than that of single hole drainage under the same conditions.When the borehole spacing is constant,the smaller the inclination of the boreholes,the more obvious the interaction between the boreholes,and the lower the gas pressure of the coal body between the boreholes.With the increase of the extraction time,the negative pressure in the drainage is increased.The range of gas seepage field formed under the action gradually increases.Field tests were carried out in Liangbei Coal Mine.Based on theoretical calculations and field practices,the reasonable water pressure required for hydraulic punching through the layers of Liangbei Coal Mine was studied and designed.Based on the law of coal body stress evolution after hydraulic punching,the effective influence radius was investigated to determine the effective influence radius of different borehole inclination angles,and the exhaust gas concentration and residual gas content of the inspection hole around the drill hole were examined after punching.And gas pressure to verify the gas treatment effect of boreholes with different inclination angles,the main conclusions are as follows:compared with the maximum gas concentration of the monitoring hole inside the elastic zone of 18%,the gas in the monitoring hole within the effective range of hydraulic punching is effective The maximum concentration is46%,so the hydraulic punching technology can significantly improve the gas drainage effect.The residual gas content and air pressure are used to verify the anti-outburst effect of drilling at different inclination angles.According to the coal bed residual gas content is less than 6m~3/t,the residual gas pressure is less than 0.6MPa,when the drilling inclination angle is 90°?75°?60°?45°?30°,the effective radii of influence are 4.3m,4.6m,5.0m,5.5m,and 6.3m.There are 42 papers,4 tables and 79 references.