Study On The Microseismic Precursor Characteristics And Early-warning Model Of Coal And Gas Outburst

As one of the most promising methods of dynamic prediction,microseismic monitoring for the early-warning of coal and gas outburst is still in the exploration stage.In order to study the feasibility and early warning method of coal and gas outburst predicted by microseismic monitoring technology,the methods of laboratory test,numerical simulation,theoretical analysis and field test are adopted in this thesis.The characteristics of acoustic emission evolution in the deformation and failure process of different types of outburst coal are studied.The microseismic precursory characteristics of four kinds of typical coal and gas outburst dangers are discussed.Based on the field monitoring data of other people,the microseismic precursor characteristics of coal and gas outburst(danger)on the spot are revealed,and the comprehensive early-warning model is proposed.Experimental research on outburst prediction by microseismic monitoring technique in Xinyuan coal mine of the Yangquan Coal Group is carried out.The following research results have been obtained:(1)The evolution characteristics of acoustic emission from different types of outburst coal during deformation and failure process are studied in laboratory test.The influence of loading stress and coal mechanical properties on acoustic emission is obtained.There is a positive correlation between the acoustic emission parameters and the stress of the raw coal.Nevertheless,the evolution of the acoustic emission parameters of briquettes is divided into two stages,the calm period before the peak stress and the outbreak period after the peak stress,which have a sudden increase in the process of coal failure.The average and peak values of acoustic emission parameters of raw coal are far greater than the corresponding values of acoustic emission parameters of briquette.(2)Based on the conclusions of acoustic emission experiment and the research results of the predecessors,numerical simulation is used to qualitatively analyze the microseismic precursory characteristics of four kinds of typical coal and gas outburst dangers of tunneling faces.Before the coal roadway driving encounters regional tectonic coal or soft stratification,microseismic signal evolution has experienced three stages,the safe period,the foreshock period and the quiet period.Before the rock cross-cut coal uncovering and encountering the fault during coal roadway driving,the microseismic intensity generally increases gradually.(3)Based on the microseismic precursory characteristics of four kinds of typical coal and gas outburst dangers and coal and gas outburst(danger)on the spot,the comprehensive early-warning model is established.The model contains three criteria.The first criterion identifies the abnormal high value of the early-warning index.The second criterion is used to identify the abnormal high value of relative change rate of early-warning index.The third criterion is used to identify the abnormal high value of chi-square value of early-warning index.Besides,the accuracy,effectiveness and practicability of the early-warning model is verified through examples.(4)The engineering application of microseismic monitoring technology verifies the accuracy and effectiveness of the comprehensive early-warning model.In the outburst danger area,the microseismic early-warning index and its chi-square value are larger and exceed the critical value many times.Besides,gas emission and daily prediction results are also relatively large,accompanied by dynamic phenomenon about coal and gas outburst.