Study On The Reasonable Sealing Parameters Of Gas Drainage Boreholes Along Coal Seam

Gas drainage from boreholes along coal seamis the main meansof preventing and control of gas disasters in coal mine,and boreholes sealing parameters is an important factor which determines gas drainage effect.In order to accurately determine the reasonable sealing parameters of boreholes along coal seam,according to the geological conditions of the 1024 mining face of theWang xingzhuang mine,the stress distribution characteristics and permeability evolution around roadway have been studied in this paper.Based on the above results,the reasonable sealing parametersof boreholes along coal seamhave been simulated,while the resultsare validated by field experiment.The main research results are as follows:?1?Through testing the physical mechanics parameters of coal and rock samplers ofthe ?₁ coal seam's roof and floor inWang xingzhuang mine,the numerical simulation software,FLAC3 D,was used to simulate the roadwayexcavationfor analysing the stress distribution characteristics around roadway,combining with filed test of the drilling cutting weight,and coal permeabilityaround roadway after excavationof numerical simulation was calculated.Simulation results show that the maximum permeability in the stress disturbance zones of roadway is 2290 times of the initial permeability,and the minimum permeability is 0.36 times of the initial permeability.?2?The gas-solid coupling model of gasmigration and coal deformationwas implemented in the COMSOL Multiphysics,in which the process of gas drainageof boreholes along coal seam with different sealing depth and sealing lengthwas simulated.Simulation results show that the sealing depth of boreholes along coal seam should not exceed the peak of the stress concentration area,and when the peak of the stress concentrationarea is exceeded,a barrier will be formed at the peak of the stress concentrationarea that can hinder the flow of gas near the peak of the stress concentrationarea.The sealing length of boreholes along coal seam should exceed the pressure relief area and reachthe stress concentrationarea while it should be slightly less than the distance from he wallofroadway to the peak of the stress concentrationarea.?3?The slurry penetration and diffusion process was simulated by utilizing COMSOL Multiphysics software.The results shows that increasing the grouting pressure can significantly increase the permeability of the slurry penetrating coal and the slurry diffusion radius under the same grouting time,and the increase of the slurry diffusion radius increases slowly with the increase of the grouting pressure.Under the same grouting pressure,the slurry diffusion radius can be increased by prolonging the grouting time,but the increase rate gradually decreases and there exists an extreme value.The reasonable grouting parameters of gas drainage boreholes along coal seam should be able to meet the slurry to seal cracks of coal body around the borehole completely.?4?The results of field experiments inWang xingzhuang mine showed that the gas concentration of boreholes along coal seamwhich is sealing by reasonable sealing parameters is higher andthe attenuationcycle ofgasdrainageis significantly prolonged.