Research On The Principle And Application Of Two-blocking And One-pressure Sealing Technology In Coal Seams With Outburst In Mine

The consumption of coal in our country accounts for about 56.8% of the primary energy consumption,in the future period,coal will still be the basic energy and industrial raw materials of our country’s economic development,in the economic and social development,is playing the important role that other resources cannot replace.But with the increase of coal mining depth,mine outburst disaster will be more and more serious.At present,pre-pumping coal seam gas is the main measure to prevent coal and gas outburst,and the effect of sealing holes directly determines the effect of pre-pumping coal seam gas.In this paper,focusing on the gas extraction effect of lifting boreholes,aiming at the two-plugging and one-pressure sealing technology of coal seams with protrusion in mines,this paper carried out in-depth research on the sealing material ratio,reasonable sealing parameters and engineering application effect of this technology through theoretical analysis,experimental research and numerical simulation,and obtained the main research results as follows:(1)The effects of different additives on the expansion performance,setting time and ultimate compressive strength of Portland cement were analyzed by single factor experiment.Twenty-nine groups of experimental schemes were designed using Design-Expert software.Combined with the response surface multi-factor analysis results,the optimal mixing ratio of each additive for the quick-setting hole sealing material was determined.(2)The defects existing in the sealing process of the traditional bag-type "two plugging and one injection" hole sealing device are analyzed,and the up-down hole sealing process of "two plugging and one pressure" is designed,and the drilling sealing process is simulated experimentally.The test results show that: Based on the traditional bag type "two plug and one injection" sealing device,the optimized design of "two plug and one pressure" sealing device can effectively make up for the defects existing in the sealing process.(3)Theoretical analysis shows that the optimal sealing depth should be greater than the radius of the elastic region;The best sealing length is the distance from plastic zone to elastic zone.The minimum grouting pressure should make the penetration radius of the grout no less than the plastic zone radius.Taking the 20#coal seam of Zhongheng Coal Mine in Guizhou Province as the engineering background,FLAC3 D software is applied for numerical simulation,and it is concluded that the initial sealing depth of the 20# coal seam of Zhongheng Coal mine should not be less than 3m,the optimal sealing length is 6-7m,and the grouting pressure should not be less than 0.73 Mpa.(4)The field application results of Coal seam floor gas drainage Roadway No.20,12 Centralized Roadway,Zhongheng Coal Mine,Guizhou Province show that:The decay ratio of 48-day average gas extraction concentration in scheme 1(polyurethane sealing)was 61.5%,that in scheme 2(" two plugging and one injection" sealing)was 2%,and that in scheme 3(" two plugging and one pressure" sealing)was 16.3% higher.(5)The field application results of 12183 return air roadway of Dongli Coal Mine in Guizhou Province show that the average extraction concentration,average branch mixed flow,average branch pure flow and other gas drainage parameters of "two plugging and one pressure" sealing technology are 3.57 times,1.02 times and2.5 times higher than that of "two plugging and one injection" sealing technology,respectively.