Research On Sensitive Indexes And Critical Values For Predicting The Area And Local Of Coal And Gas Outburst In Xiangshui Coal Mine

Coal and gas outburst accidents seriously threaten the safe production of mines.Regional prediction and local prediction are the two"four-in-one"steps of gas prevention and control.It is of great significance to determine the outburst prediction indicators and critical values reasonably.The 19#coal seam of Xiangshui Coal Mine is an outburst coal seam.Using scientific and reasonable methods to determine its outburst prediction sensitivity index and critical value can play an important role in guiding the subsequent outburst prevention work.This article first studied the existing methods for determining the critical value of gas content in regional predictions,and analyzed the applicability of laboratory methods,empirical formula methods and statistical methods of prominent historical data to determine the critical value of gas content in the 19#coal seam of Xiangshui Coal Mine.The results showed that the critical value of gas content determined by the laboratory method was deviated from the actual situation on the 19#coal seam of Xiangshui Mine;the empirical formula method only considers the solidity coefficient and volatile content of the coal body,and cannot objectively and truly reflect the outburst elements of 19#coal seam of Xiangshui Mine.Outburst historical data statistical method requires sufficient outburst historical data,while the 19#coal seam outburst historical data of Xiangshui Coal Mine is scarce,so this method cannot be used to analyze the critical value.Based on the shortcomings of the above methods,a new method for determining the critical value of gas content based on regional effect test gas content and historical data analysis of local predictive indicators was proposed.Subsequently,the existing methods for determining the sensitivity of local predictors were studied.The sensitivity function method only analyzes the sensitivity of the indicators by the degree of dispersion of the predictors,and does not take into account the prominent main control factors;gray correlation analysis method requires more types of predictive indicators to determine the system mapping amount in an all-round way,while the local outburst predictor indicators used in the 19#coal seam of Xiangshui Coal Mine are only K₁and S.This method is also not applicable to Xiangshui Coal Mine.Based on the deficiencies of these methods,the analysis method of the correlation between the local predictive index and the outburst factor was determined to analyze the sensitivity of the local predictive index of the 19#coal seam of Xiangshui Coal Mine.Analyzed and studied the"three-rate"method,which is widely used to determine the critical value of local predictive sensitive indicators.In the"three-rate"method,the prediction protruding rate needs to be selected within the interval of 10%to 30%,and there is a certain degree of randomness.To this end,this paper proposed a new method for predicting the outburst rate selection.This method was based on the historical data of local outburst prediction in the process of roadway excavation,and the proportion of the area with outstanding signs in the excavated roadway was counted,and this ratio was used as the prediction prominence rate.According to the above research results,the gas content critical value of the 19#coal seam of Xiangshui Coal Mine was determined by the historical data analysis method based on regional effect test gas content and local prediction index,and the critical value of gas content was 7.1 m³/t;the correlation analysis method of local predictive indicators and main controlling factors of outburst was used to study the sensitivity of K₁ and S values of the 19#coal seam of Xiangshui Coal Mine,and it was concluded that the K₁ value is more sensitive than the S value;the critical value of K₁ value was determined using the"three rates"method,and the critical value of K₁ value was obtained as 0.48 m L/(g·min^1/2).Finally,the determined critical value of the predicted gas content in the region and the critical value of the local prediction sensitivity index K₁ were tracked and verified.The results showed that the determined critical value can ensure the safe mining of the working face.At the same time,it also verified the rationality of the used predictive index sensitivity and criticality determination method.The paper has 28 figures,19 tables,and 81 references.