Research On Real-time Monitoring & Early Warning Technology Of Coal And Gas Outburst Of The Driving Working Face

With the extension of mining depth, stress and gas pressure are growing. And coal and gas outburst disaster become more and more serious and complex. Low index outburst, roof and floor rock roadway outburst occurred occasionally. The traditional prediction methods cannot meet the demands of safe and efficient mining completely, so it needs an accurate, real-time monitoring and early warning technology to predict coal and gas outburst urgently. Coal and gas outburst is a coupling complicated dynamic evolution process under stress and gas pressure. Therefore, the real-time monitoring and early warning technology about coal and gas outburst was researched. The gas emission law before loaded failure of coal containing gas and the coal and outburst of the heading face were analyzed. The dynamic model of gas emission in the heading face and the inverse model of gas content and the main influence factors of gas emission were studied. A real-time early warning index system of coal and gas outburst was established. The early warning method was proposed. The results were verified by developing real-time monitoring and warning software for coal and gas outburst. The following results have been obtained in this paper:The experimental system about monitoring gas emission of the loaded coal containing gas was established. Gas emission in the failure process of coal containing gas was analyzed under different loading rate, adsorption pressure and confining pressure. It was found there was critical slowing down characteristics in gas emission before coal containing gas failure. The increase trend of variance and autocorrelation coefficient about gas emission can be used as the precursor signals of the coal containing gas failure.The gas emission abnormal characteristics of the heading face before coal and gas outburst were studied according to the Jiulishan Coalmine, etc. It was found that there existed three abnormal types, such as the increase type, fluctuation type and first drop and then rise type before coal and gas outburst. And there were also critical slowing down characteristics. Among them, the increase type of gas emission is mainly because of the working face with high gas pressure gradient or fast driving speed. And with driving, gas emission will continue to rise, which is easy to cause the typical coal and gas outburst. The fluctuation patterns of gas emission which is mainly caused by the high stress and high gas pressure in the deep coal seam. Under the external disturbing, there is paroxysmal deformation and fracture in coal and abnormal fluctuations in gas emission. The first drop and then rise type of gas emission mainly occurred in the region of abnormal increase of stress. The coal body is strongly compressed by high stress and the seepage channel of the gas is squeezed, which leads low permeability, so gas emission gradually decreased. With the driving, the environment of gas occurrence is destroyed by the superimposed effects of high ground stress. The coal seam cracks number gradually increase, gas seepage channels increase and connect, so gas emission gradually increase.According to the source of gas emission of the driving working face, the effective stress, gas adsorption expansion effect, the role of pore pressure to coal skeleton and all these to permeability were considered to build gas emission model and gas content inverse model which could reflect the dynamic features of gas emission. The main influencing factors of gas emission in the heading face were analyzed by numerical simulation. The increase of gas pressure, stress and the driving speed, and the variation of coal thickness and strength will lead to the increase of stress gradient, gas pressure gradient or both increases. Gas emission showed abnormal emission of increasing or decreasing. The entire phenomenon has revealed the precursor mechanism of coal and gas outburst, such as the increase type, fluctuation type and first drop and then rise type.On the basis of the above research, the real-time early warning index system of coal and gas outburst, including variance and autocorrelation coefficient which can reflect gas emission critical slowing down, gas content, acoustic emission and electromagnetic radiation is established. The coupling early warning method of Fisher discrimination analysis and Fuzzy comprehensive evaluation is proposed. The software of real-time monitoring and early warning system for coal and gas outburst is developed.The real-time monitoring and early warning technology is verified. The results show the coupling early warning method of Fisher Discrimination analysis and Fuzzy comprehensive evaluation monitor 72 times, of which 7 are warning and 5 are dangerous according to the conventional index exceeded or spray hole. And the coupling early warning method avoids lost effectively, the accuracy of early warning was improved. The early warning technology of coal and gas outburst achieves real-time monitor and early warning gas outburst.The research provides important theoretical significance and practical value to the coal and gas outburst prevention.