Sensitive Indicators And Threshold’s Ditermination Study On Coal And Gas Prediction

The ground stress of coal seam, gas content and gas pressure increase with the depth of exploration, and the gas disasters that caused by changes are more and more serious. After analyzing the gas disasters happened from2013 to 2015, the author got a conclusion:the prevention of coal and gas outburst is the key point for coal mine safety. This thesis using "three ration method", "equations of mathematical physics" and "grey association analysis" analyzed the drillings methane absorption index Ah2 and drillings quantity index S from No.5 coal seam in Yong Shan coal mine and No.2 coal seam in Jiu Long coal mine. The main research findings are as followed.1) With the help of "three ration method", this thesis calculated the outburst rate Ah2 value of No.5 coal seam in Yong Shan coal mine is 25%, S value is 30.6%. The accuracy of outburst rate is 66.7%, S value is 54.5%. The non-outburst rates are all 100%. The outburst rate Ah2 value of No.2 coal seam in Jiu Long coal mine is 23.3%, S value is 3.33%. The accuracy of outburst rate is 57.1%, S value is 0%. The non-outburst rate is 100%, S value is 86.2%.2) Using "equations of mathematical physics" method, this thesis got the sensitivity of outburst dangerous index of the two selected coal mine. For the No.5 coal seam in Yong Shan coal mine, the sensitivity of drillings gas absorption index is 0.303, the S value is 0.286. For the No.2 coal seam drillings gas absorption index in Jiu Long coal mine is 0.339 and the drillings quantity S value is 0.174.3) Utilizing "grey association analysis" principle, this thesis got the relative degree of outburst index. For the No.5 coal seam in Yong Shan coal mine, the relative degree of the drillings gas absorption index is 0.904, S value relative degree is 0.890. For the No.2 coal seam in Jiu Long coal mine, the relative degree of drillings gas absorption is 0.832, S value relative degree is 0.724.4) From the relation curve of gas absorption index â–³h2 in coal sample and gas pressure, this thesis got the conclusion that the critical value of No.5 coal seam in Yong Shan coal mine is 330Pa, the critical value of No.2 coal seam in Jiu Long is 190 Pa. Combining the real-site research data, the critical value Ah2 of Yong Shan coal mine is 200 Pa, and the critical value â–³h2 of Jiu Long coal mine is 190 Pa.