| The production conditions of coal mines in China are complex,and various disasters and accidents often occur,among which gas accidents are the main cause of casualties.Therefore,the monitoring and early warning of gas disaster hidden danger is the premise and key to effectively prevent the occurrence of gas disaster.The gas concentration of working face is affected by many factors,such as coal seam gas content,permeability and ground stress and mining process itself.The change of gas concentration in working face caused by it will reduce the accuracy of early warning of gas disaster hidden danger to a certain extent.In view of the above problems,the research in this thesis is based on the methods and achievements of predecessors in gas disaster early warning.Based on the coal mine safety monitoring and control system of a city,the gas monitoring data before and after different coal mine gas disasters are collected.The variation law and time sequence characteristics of various processes are clarified,the variation law of gas disaster precursors is revealed,and the early warning index system of gas disaster is established and improved.Based on the early warning method of gas disaster,the early warning model of gas disaster hidden danger based on Fisher discriminant method is established,and it is applied and verified in different coal mines.The specific research results are as follows:The variation law of gas concentration in various processes of coal mining process is studied,and the dynamic variation characteristics of gas concentration in different processes of mining face are obtained,including the gradient and periodic characteristics of gas concentration in mining and tunneling process.The timing characteristics of gas concentration in various processes are studied,and the early warning system of gas disaster is determined,which lays a foundation for the establishment of early warning model of gas disaster potential hazard.The variation law and characteristics of gas dynamic precursor in the evolution process of gas disaster are studied.The results show that the gas concentration will show a significant upward trend before the occurrence of gas disasters,and the change rate is large;precursors of gas concentration generally appear 1-2 days before the occurrence of gas disasters,accompanied by large fluctuations.The 12-hour and 4-hour time scales were determined as the best observation scales for the macroscopic change trend of gas concentration and the precursory characteristics of gas disasters,respectively.The variance of critical slowing characteristics is used to extract the precursor information of gas disaster.The results show that the gas emission before the occurrence of gas disaster risk has abnormal precursor and presents the characteristics of critical slowing.With the increase of gas disaster risk,the gas concentration gradually increases,and the variance of gas concentration increases.Therefore,the variance or standard deviation can be used as the early warning index of gas disaster.The early warning system of gas disaster potential hazard is established,and the standard deviation,the slope of the highest peak value and the mean value are selected as the early warning indicators.The early warning method of gas disaster potential hazard based on overrun early warning and dynamic trend early warning is proposed.An early warning model of gas disaster potential hazard based on Fisher linear discriminant method was established,and the accuracy of the model was verified.The results show that the accuracy of gas disaster danger signal warning is as high as 93.8 %,the accuracy of no danger signal warning is 100 %,and there is no missing report.The overall accuracy is 96.7 %.According to the gas data of different coal mines,the accuracy and reliability of the gas disaster early warning model are verified.The results show that the early warning results of 10 gas disasters are accurate,indicating that the early warning results are highly reliable.The research results of this thesis provide a theoretical basis for the early warning of gas disasters,and have important practical significance and application value for the monitoring and early warning of gas disasters.There are 37 figures,29 tables,81 references in this thesis. |
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