| Gas Drainage is one of the most direct and effective ways to prevent and control mine gas,which can not only eliminate the danger of coal seam outburst and ensure the safety of mine production,but also realize “Turning harm into treasure” and maximize the benefit of resource utilization.The coal geological conditions are complex in China,and with the increasing depth of coal resources mining,the permeability of most coal seam is low,and the efficiency of gas extraction is low.Therefore,it is necessary to adopt the relevant technical means of pressure relief and permeability enhancement to enhance the efficiency of gas extraction.As a new technology of enhancing gas drainage,mechanical hole-making through seam with bottom drainage is a good test result in low permeability outburst coal seam.However,at present,there are few research results on mechanism,technological process,technical characteristics and related influencing factors of hole-making technology in floor-to-floor and throughfloor,and the field test research is not deep enough to promote the technology widely.To this end,after extensive data collection,full site investigation,rigorous numerical analysis and scientific experimental research,the related research on the technical system,pressure relief and permeability increasing mechanism and field test of holemaking by mechanical drilling in floor-to-floor Roadway with bottom pumping has been completed.Through the above research,the main conclusions or progress of this thesis are as follows:(1)Through the research and analysis of the technical principle,equipment system,drilling technology and technical characteristics of the hole-drilling machine in the floor-pumping roadway through the floor,an integrated system of mechanical hole drilling,which has high drilling efficiency,wide application range and stable holemaking effect,is constructed.Large diameter holes are constructed in coal body by mechanical hole-making device,and effective pressure relief is realized for outburst media,improve the coal seam permeability,to achieve the outburst of the coal seam to enhance the gas extraction;(2)By deducing the coupled gas seepage equation of coal seam and the deformation field equation of coal body,the solid-gas dynamic coupling model of low permeability coal and gas was established.With the help of COMSPL-Multiphysics numerical simulation software,the influencing factors related to mechanical cavitation of drilling hole through the bottom drainage roadway were simulated and analyzed,and the following conclusions were drawn:(1)With the increase of the initial gas pressure,the gas pressure gradient near the borehole also increases.However,the gas extraction radius of mechanical cavitation hole does not change greatly with the change of the initial gas pressure of coal seam.(2)The larger the cavitation diameter of drilling machine is,the better the effect of coal pressure relief and reflection improvement is;(3)It is reasonable to use Φ550mm mechanical cavitation gas to extract gas from boreholes through the layer for 90 days to keep the spacing of boreholes within the range of 8～10m.In field practice,it is necessary to design the spacing of boreholes for gas extraction according to the radius of coal seam gas extraction and other practical conditions.(4)The greater the negative pressure of gas extraction,the better the gas extraction effect,but the effect is weak;(3)Combined with the actual situation of the test working face,the drilling layout scheme of gas drainage in the air bottom drainage roadway of the test mine 15309 working face is designed;The gas extraction radius of mechanical cavitation drilling hole in 15 coal seam of the test mine was measured by "flow method" at the test site.Compared with ordinary drilling hole,the gas extraction radius of mechanical cavitation drilling hole was 1.36 times larger.There are 39 figures,9 tables and 117 references in this thesis. |
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