煤体静载破坏中低频磁场变化特征及产生机制研究
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摘要
为了研究煤体静载破坏中低频磁场变化特征及其产生机制,进一步完善煤矿动力灾害监测预警技术,通过室内试验、现场试验研究了煤体静载破坏中低频磁场时、频谱特征,并结合微震信号提出了低频磁信号的产生机制。结果表明:煤体静载破坏中所产生低频磁场信号强度为19～156 nT,信号最大幅值、能量与试样强度、加载速度均呈正相关关系。垂直于裂纹扩展面磁场最强,平行于裂纹扩展面磁场最弱。并结果微震信号提出了低频磁场产生机制。低频磁场与微震信号具有时、频域同步性,带电裂纹面随微震信号同频振荡为低频磁场产生机制。现场放炮破煤低频磁信号由簇状脉冲信号及小幅震荡信号组成,其中簇状脉冲成分产生于炮后振动波带动带电壁面的同频振动,而小幅震荡成分是巷帮煤壁趋向新应力平衡状态时发生的横向拉伸破坏及带电煤碎屑运移、摩擦及转动的结果。
The aim of this paper is to study the characteristics and generation mechanism of the low-frequency magnetic field generated during the damage of coal under static load, and to complete the monitoring and warning technology of dynamic disasters in coal mine. Laboratory and field experiments were conducted to analyse the characteristics in time and frequency domain of low-frequency magnetic signal. Laboratory experiment results show that the strength of the generated magnetic field is in the range of 19-156 nT. Both the maximum amplitude and magnetic field energy have a positive correlation with the intensity of coal and loading speed. It also shows that the magnetic field perpendicular to crack surface is the strongest, while the magnetic field parallel to the crack surface is the weakest. Then, by combining with the micro-seismic signal, generation mechanism of the low-frequency magnetic field was proposed. Results reflect that the magnetic signal and micro-seismic signal are synchronous in the time and frequency domain, and oscillation of crack surface with charge leads to low-frequency magnetic field. Field test results indicate that the magnetic signal includes the cluster pulse signal and small amplitude oscillation signal. The cluster pulse signal is caused by the crack surface vibration generated from blasting. The small amplitude oscillation signal is the result of lateral tensile failure generated during the formation process of the new stress equilibrium in coal wall, and migration, friction and rotation of coal particles with charge.
The aim of this paper is to study the characteristics and generation mechanism of the low-frequency magnetic field generated during the damage of coal under static load, and to complete the monitoring and warning technology of dynamic disasters in coal mine. Laboratory and field experiments were conducted to analyse the characteristics in time and frequency domain of low-frequency magnetic signal. Laboratory experiment results show that the strength of the generated magnetic field is in the range of 19-156 nT. Both the maximum amplitude and magnetic field energy have a positive correlation with the intensity of coal and loading speed. It also shows that the magnetic field perpendicular to crack surface is the strongest, while the magnetic field parallel to the crack surface is the weakest. Then, by combining with the micro-seismic signal, generation mechanism of the low-frequency magnetic field was proposed. Results reflect that the magnetic signal and micro-seismic signal are synchronous in the time and frequency domain, and oscillation of crack surface with charge leads to low-frequency magnetic field. Field test results indicate that the magnetic signal includes the cluster pulse signal and small amplitude oscillation signal. The cluster pulse signal is caused by the crack surface vibration generated from blasting. The small amplitude oscillation signal is the result of lateral tensile failure generated during the formation process of the new stress equilibrium in coal wall, and migration, friction and rotation of coal particles with charge.
引文
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[22]李成武,解北京,杨威,等.煤冲击破坏过程中的近距离瞬变磁场变化特征研究[J].岩石力学与工程学报,2012,31(5):973-981.LI Cheng-wu,XIE Bei-jing,YANG Wei,et al.Characteristics of transient magnetic nearby field in process of coal impact damage[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(5):973-981.
[23]孙晓元.受载煤体振动破坏特征及致灾机理研究[D].北京:中国矿业大学(北京),2016:3-4.SUN Xiao-yuan.The research on vibration failure characteristics and disaster-causing mechanism of loaded coal[D].Beijing:China University of Mining&Technology(Beijing),2016:3-4.
[24]胡广书.数字信号处理:理论、算法与实现[M].北京:清华大学出版社,2003:293-298.HU Guang-shu.Digital signal processing:Theories,algorithms and implementation[M].Beijing:Tsinghua University Press,2003:293-298.
[2]孙强,薛晓辉,朱术云.岩石脆性破坏临界信息综合识别[J].固体力学学报,2013,34(3):311-319.SUN Qiang,XUE Xiao-hui,ZHU Shu-yun.The identification method of critical information for rock brittle failure[J].Chinese Journal of Solid Mechanics,2013,34(3):311-319.
[3]TRONIN A A.Satellite thermal survey:A new tool for the study of seismoactive regions[J].International Journal of Remote Sensing,1996,17(8):1439-1455.
[4]WU L X,LIU S J,WU Y H,et al.Precursors for rock fracturing and failure―PartⅠ:IRR image abnormallities[J].International Journal of Rock Mechanics and Mining Sciences,2006,43(3):473-482.
[5]GELLER R J.Earthquake prediction:A critical review[J].Geophysical Journal of the Royal Astronomical Society,1997,131(3):425-450.
[6]郭自强,刘斌.岩石破裂电磁辐射的频率特性[J].地球物理学报,1995,38(2):221-226.GUO Zi-qiang,LIU Bin.Frequency properties of electromagnetic emission associated with microscopic cracking in rocks[J].Chinese Journal of Geophysics,1995,38(2):221-226.
[7]李夕兵,万国香,周子龙.岩石破裂电磁辐射频率与岩石属性参数的关系[J].地球物理学报,2009,52(1):259-265.LI Xi-bing,WAN Guo-xiang,ZHOU Zi-long.The relation between the frequency of electromagnetic radiation(EMR)induced by rock fracture and attribute parameters of rock masses[J].Chinese Journal of Geophysics,2009,52(1):259-265.
[8]YOSHIDA S,OGAWA T.Electromagnetic emissions from dry and wet granite associated with acoustic emissions[J].Journal of Geophysical Research Solid Earth,2004,109(9):271-297.
[9]CRESS G O,BRADY B T,ROWELL G A.Sources of electromagnetic radiation from fracture of rock samples in the laboratory[J].Geophysical Research Letters,1987,14(4):331-334.
[10]何学秋,王恩元,聂百胜,等.煤岩流变电磁动力学[M].北京:科学出版社,2003.HE Xue-qiu,WANG En-yuan,NIE Bai-sheng,et al.Electromagnetic dynamics of coal or rock rheology[M].Beijing:Science Press,2003.
[11]何学秋,聂百胜,王恩元,等.矿井煤岩动力灾害电磁辐射预警技术[J].煤炭学报,2007,32(1):56-59.HE Xue-qiu,NIE Bai-sheng,WANG En-yuan,et al.Electromagnetic emission forecasting technology of coal or rock dynamic disasters in mine[J].Journal of China Coal Society,2007,32(1):56-59.
[12]王恩元,何学秋,聂百胜,等.电磁辐射法预测煤与瓦斯突出原理[J].中国矿业大学学报,2000,29(3):225-229.WANG En-yuan,HE Xue-qiu,NIE Bai-sheng,et al.Principle of predicting coal and gas outburst using electromagnetic emission[J].Journal of China University of Mining&Technology,2000,29(3):225-229.
[13]王恩元,何学秋.煤岩变形破裂电磁辐射的试验研究[J].地球物理学报,2000,43(1):131-137.WANG En-yuan,HE Xue-qiu.An experiment study of the electromagnetic emission during the deformation and fracture of coal or rock[J].Chinese Journal of Geophysics,2000,43(1):131-137.
[14]聂百胜,何学秋,王恩元,等.煤体剪切破坏过程电磁辐射与声发射研究[J].中国矿业大学学报,2002,31(6):609-611.NIE Bai-sheng,HE Xue-qiu,WANG En-yuan,et al.Study on electromagnetic radiation and acoustic emission in shearing process of coal[J].Journal of China University of Mining&Technology,2002,31(6):609-611.
[15]刘晓斐,王恩元,何学秋.孤岛煤柱冲击地压电磁辐射前兆时间序列分析[J].煤炭学报,2010,35(增刊1):15-18.LIU Xiao-fei,WANG En-yuan,HE Xue-qiu.Time series analysis of electromagnetic radiation precursor of rockburst in gob-surrounded coal pillar[J].Journal of China Coal Society,2010,35(Supp.1):15-18.
[16]胡少斌,王恩元,李忠辉,等.受载煤体电磁辐射动态非线性特征[J].中国矿业大学学报,2014,43(3):380-387.HU Shao-bin,WANG En-yuan,LI Zhong-hui,et al.Norlinear dynamic characteristics of electro-magenetic radiation during loading coal[J].Journal of China University of Mining&Technology,2014,43(3):380-387.
[17]WANG E Y,ZHAO E L.Numerical simulation of electromagnetic radiation caused by coal/rock deformation and failure[J].International Journal of Rock Mechanics and Mining Sciences,2013,57:57-63.
[18]刘明举,何学秋,许考.孔隙气体对断裂电磁辐射的影响及其机理[J].煤炭学报,2002,27(5):483-487.LIU Ming-ju,HE Xue-qiu,XU Kao.Influence of porous on ruptured electromagnetic radiation and its mechanism[J].Journal of China Coal Society,2002,27(5):483-487.
[19]HE X Q,NIE B S,CHEN W X,et al.Research progress on electromagnetic radiation in gas-containing coal and rock fracture and its applications[J].Safety Science,2012,50(4):728-735.
[20]LI C W,SUN X Y,WANG C,et al.The correlated characteristics of micro-seismic and electromagnetic radiation signals on a deep blasting workface[J].Journal of Geophysics&Engineering,2016,13(6):1020-1035.
[21]LI C W,WANG C,XIE B J,et al.Study on lowfrequency tem effect of coal during dynamic rupture[J].Shock and Vibration,2015,(16):1-8.
[22]李成武,解北京,杨威,等.煤冲击破坏过程中的近距离瞬变磁场变化特征研究[J].岩石力学与工程学报,2012,31(5):973-981.LI Cheng-wu,XIE Bei-jing,YANG Wei,et al.Characteristics of transient magnetic nearby field in process of coal impact damage[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(5):973-981.
[23]孙晓元.受载煤体振动破坏特征及致灾机理研究[D].北京:中国矿业大学(北京),2016:3-4.SUN Xiao-yuan.The research on vibration failure characteristics and disaster-causing mechanism of loaded coal[D].Beijing:China University of Mining&Technology(Beijing),2016:3-4.
[24]胡广书.数字信号处理:理论、算法与实现[M].北京:清华大学出版社,2003:293-298.HU Guang-shu.Digital signal processing:Theories,algorithms and implementation[M].Beijing:Tsinghua University Press,2003:293-298.