Experimental And Theoretical Studies Of Coal And Gas Outburst Hole Formation Mechanism And Prominent Energy Source

China is one of coutries with most serious and greatest danger in coal and gasoutburst, which has been posing critical threat to the safety production in coal mine.And with increasing of mining depth, the conundrums concluding high in-situ stress,high gas content, big gas pressure and low venting quality faced, therefore, it isnecessary for systematically experimental and theoretical researches on trigger ofoutburst and the mechanism of formation processes of outburst hole in this paper. Somekey questions will be solved during the research: to study the formation and evolutionof coal and gas outburst hole by using mechanics, and clear the delineation method ofcoal and gas outburst hole abstractly; the law of gas adsorption, desorption and seepage;the research on transformation of power and energy during from the perspective ofenergy theory, and mechanism of coal and gas outburst were further revealed. Based ontypical outburst case in coal mine, combining theoretical investigation, experimentalstudy and numerical simulation analysis in the paper, the research results are asfollowed:Based on field data of coal and gas outburst and the results of simulation testing inlab, the effect of geological structure, ground stress, gas pressure and the physicalmechanics of coal properties on coal and gas outburst has been analysed, meanwhile thegeneral rule of coal and gas outburst and the pattern of outburst hole have beensummerrized.According to discrimination criterion of stress, strain and gas outburst timeprediction theory and the geological data of outburst target point, this paper has built thenumerical analysis model of coal road tunneling face, and analyzed the morphology ofoutburst hole during the excavation process, meanwhile the possible time of coal andgas outburst has been calculated.The experiment studied the adsorption and desorption capacity of methane, andfound that the adsorption of methane on coal belong to theⅠkind of sorption, which canbe described by the Langmuir Equation, Freundlich Equation, BET Equation and D-REquation, while the desorption law can be described by emprical formula, diffusionmodel and percolation model, among these, diffusion model can describe the thedesorption of methane on coal excellently.Gas seepage properties in coal have been exprimently studied, and it is found that the permeability rate and effective stress both first decreased and then increased withincreasing of the ratio between effective axial stress and effective confining pressure;the permeability rate decreased with increasing of effective stress and then tend togentle at a given ratio between effective axial stress and effective confining pressure,and there is a relationship of negative exponential function between permeability rateand effective stress.Based on the energy theory of coal and gas outburst, elastic properties of coal andgas expansion energy have been experimentally studied, which showed that there has arelationship of power function between unit volume elastic energy and body stress; gasexpansion energy has a linear relationship with gas pressure, which was closely relatedto moisture content, density of coal and gas pressure.The experiment studied the breaking capacity during coal and gas outburst process,which showed that fragmentation mechanism of coal can be explained by the newsurface theory, the similarity hypothesis and the crack hypothesis, among these, thecrack hypothesis can excellently describe the relationship between breaking capacityand fragment-size of coal, and there has a linear relationship between the specificenergy W and1/（d_m）^1/2.