Research On Dynamic Comprehensive Early Warning Technology Of Dangerous Gas Outburst In Driving Face

As coal mining enters deep areas,coal seam gas pressure and ground stress continue to increase,and the danger of coal and gas outbursts is increasing.In particular,low-index outburst dangers are becoming more and more obvious,and the difficulty of early warning is gradually increasing.The current conventional index forecasting method in coal mines is difficult to predict the outlier danger in real time and continuously,and the accuracy of early warning needs to be further improved.Based on a large number of previous research results in coal and gas outburst monitoring and early warning,this paper analyzes the influencing factors of gas dynamic changes in the driving face of the test mine,and constructs a coal seam gas parameter inversion model,based on the geological parameters and the driving process of the test mine.The data continuously revised the model inversion parameters and verified the inversion model.The regular indexes and coal thickness changes during the tunneling process,the gas dynamic response regularities and characteristics before the emergence of coal seam outburst hazard and during the mining process of the working face are studied,and the correlation analysis between the gas concentration signal of the working face and the conventional indexes is carried out.Based on the precursor characteristics of gas dynamic change before the emergence of the prominent hazard,the gas dynamic characteristic parameters were mined by the linear fitting method,and the gas dynamic trend early warning method was proposed.The logistic regression analysis method is used to couple multiple early warning indicators,and a real-time comprehensive early warning model of coal and gas outburst based on gas dynamic indicators is established,and verified by field application,the model has a higher early warning accuracy rate and better early warning effect.The specific research results are as follows:(1)When the speed of excavation in the working face is accelerated,the thickness of the coal seam changes frequently,the gas content and pressure increase,and the geological structure in the coal seam,etc.,can cause abnormal changes in the gas concentration of the driving face of the test mine,and increase the risk of coal and gas outburst at the working face.(2)Based on the analysis results of the influencing factors of gas dynamic changes and the source of gas emission,a gas content and pressure inversion model was constructed.After field verification,the maximum error between the inversion value of coal seam gas content and the measured value is 13.6%,and the average error is 8.2%.The maximum error between the inversion value of coal seam gas pressure and the measured value is 15.4%,and the average error is 9.05%.The inversion result of coal seam gas parameters is basically consistent with the actual situation,and the error meets the requirements of engineering applications.(3)During the excavation of the test mine face,the measured K₁ and S values of the conventional indicators did not exceed the limit,but the conventional indicators had an abnormal increase process before the outburst hazard occurred,and they corresponded well to the changes in coal seam thickness.Before the outburst hazard appears,the real-time gas concentration at the working face shows a trend of first rising and then falling.In the process of mining face,the gas concentration gradually decreases,and finally remains at a low level,which corresponds well to the coal seam drainage effect.The changes in coal seam gas content and gas pressure calculated by inversion can better reflect the effect of coal seam pressure relief and drainage.The correlation between the average daily gas concentration and the conventional indicators is analyzed.Among them,the gas concentration has a good correspondence with the conventional indicator K₁ value,reaching a significant degree of correlation,and has a poor correspondence with the conventional indicator S value,showing a weak correlation.(4)According to the gas dynamic change characteristics before the prominent hazard appears,the linear fitting method is used to mine the gas dynamic characteristic parameters,namely the slope K,the correlation coefficient R² and the rate of change C as early warning indicators,and the gas dynamic trend warning is proposed.Method to determine the critical value of the gas dynamic early-warning indicators in the test mine:the slope K₁ is 0.01(-0.01),the correlation coefficient R₂² is 0.1,the rate of change C₂is 0.35(-0.35),and the initial phase time period T₁ is 2h,and the early warning phase time period T₂ is 4h.(5)Using the method of Logistic regression analysis,the gas dynamic trend method warning result T,gas inversion parameters and the conventional index K₁ value were coupled and analyzed,and a real-time comprehensive warning model for coal and gas outburst based on gas dynamic indexes was established to confirm the warning,The critical value of the index is 50%,and the comprehensive early warning model has been verified on site.The results show that the outburst risk early warning accuracy rate of the coal and gas outburst real-time comprehensive early warning model is 90%,and the accuracy rate of the no outburst risk early warning is 100%.No underreporting.The research results of this paper have important guiding significance and practical value for the monitoring and early warning of coal and gas outbursts in coal mining face.The paper contains 33 figures,16 tables,and 87 references.