Research On Monitoring And Early Warning Of Coal And Gas Outburst In Driving Process Of Coal Roadway By EMR,AE And Gas

With the increase of mining depth and strength,coal and gas outburst becomes more and more serious and complex in China.Electromagnetic radiation(EMR)and acoustic emission(AE)monitoring and early warning technology of has been widely used in coal and rock dynamic disasters.But at present,the mechanism of coal and gas outburst and the corresponding evolution characteristics of EMR and AE are not clear,the research on the identification of effective signals in the process of coal and gas outburst monitoring and the filtering method of interference signals are still insufficientt,and early warning methods are not perfect,all these deficiencies seriously affect the improvement of the accuracy and reliability of early warning.Based on this,this paper established the simulation experiment system of coal and gas outburst in coal roadway,studied the change law of EMR,AE,gas pressure and stress in the process of outburst evolution,determined the sensitive index of EMR and AE monitoring,and the prominent precursory information was also extracted.In the process of field monitoring,an automatic identification and filtering method based on the characteristics of noise source signals was proposed,effective EMR and AE signals in the process of coal and gas outburst were obtained,a multi index monitoring and warning model based on effective signals was established,and the field verification and application were carried out.This paper has obtained the following main research results:First,the time and frequency of the interference signal and the coal rock fracture signal were measured and analyzed in real time.The results showed that the frequency component of coal rock EMR and AE interference signal was single,and the energy was mainly concentrated in the lower frequency range.During the loading fracture of coal and rock samples,the energy value,the pulse counts and the centroid frequency of EMR and AE were the sensitive indexes of monitoring,and signal amplitude havd a good response to the large rupture group during the period of instability.Second,based on the simulation experiment of coal and gas outburst induced by roadway drivage,the changes of stress,gas pressure,and time domain,frequency domain and waveform characteristics of EMR and AE signals in the evolution process of coal and gas outburst were analyzed.The results showed that the energy value,pulse counts and centroid frequency of EMR in coal roadway drivage all presented an increasing trend,and there were sudden augmentation precursors before outburst.High amplitude effective signals could be regarded as the characteristic signal of coal and gas outburst and were signs of coal instability.Third,the damage-EMR-AE coupling model of coal and rock was built to study the change rule of EMR and AE signals during the evolution process of gas outburst.The results showed that the development process of coal and gas outburst was characterized by spatio-temporal change of coal and rock destruction.In the early stage of the stress concentration area,coal body was mainly subjected to pressure shear failure.In the late stage of the outburst development,coal body mainly took place in tensile failure.In the process of outstanding evolution,the variation range of stress field,damage field and gas seepage field were 0~10m,0~5m,and 0~8m ahead the heading face respectively.Fourth,there are two types of AE and EMR interference signals generated by underground activities,they are intermittent type and short-term burst type.Among them,the intermittent interference signals were produced during the outburst regional prevention drilling and roof holding,and the short-term burst type signal were produced when cleaning coal,blasting or moving sensors.Combining the change rate judgment method and the local polynomial prediction method,automatic recognition and filtering of interference signals were realized during monitoring.Fifth,a multi index EMR,AE and gas monitoring early warning method based on effective signals is proposed.Before early warning,the signals were identified and filtered,and centroid frequency and the number of characteristic signal waveform were introduced in the early warning process.The field verification results showed that the filtered signals could surely improve the reliability of the EMR and AE monitoring data,more effectively reflect the evolution process of the coal and gas outburst,and reduce the false alarm rate.The multi index comprehensive early warning method can comprehensively reflect the danger in front of the heading face,and make early warning of the outburst danger in time.Multiple indicators can be verified and compensated for each other to avoid missing reports..The research results provide theoretical basis and scientific basis for further revealing the mechanism and precursory characteristics of coal and gas outburst in coal roadway.It has theoretical and practical value for the prevention and control of coal and gas outburst and the improvement of the accuracy of EMR-AE-gas monitoring and early warning.