煤破裂带电裂纹扩展及壁面振动诱发电磁辐射机理

Rockbursts pose a serious threat to coal mine safety. Electromagnetic emission (EME) technique has been widely used in coal mines with rockburst risk due to its advantages in risk monitoring and early warning. However, the mechanism of EME is still unclear, resulting in relatively low application reliability of this technique. Based on the knowledge of EME phenomenon which states EME is produced by charge separation and movement during coal rock fracture, this work seeks to further solve the basic science problems associated with EME mechanism, namely how is the charge produced and distributed, how does the crack propagate and oscillate and thus influencing charge movement. In this work, the coal will be quantitatively loaded and measured in micro-scale to study its electrical characteristics at static and loading state, and thus to reveal the charge production mechanism and charge distribution law. The coal will also be loaded and measured in macro-scale to study the characteristics of crack propagation and oscillation and the characteristics of EME waveform and amplitude-frequency, and thus to reveal the influence of crack propagation and oscillation on EME. Based on investigations above, the influence of crack propagation and oscillation on charge movement will be studied. Also, a theoretical model explaining EME induced by propagation and oscillation of electrically charged crack will be established. Furthermore, the constitutive relation between transient electromagnetic field and electrically charged crack propagating and oscillating will be revealed. The theoretical model and constitutive relation will be proved and amended by macroscopic experiments which contain loading on specimens with artificial cracks and EME response in crack propagating process. The research is able to further develop coal rock EME theory and technique.

我国冲击地压灾害严重，煤岩电磁辐射技术在冲击危险性监测预警方面具有优势，已在煤矿大量应用。然而，煤岩电磁辐射机理不清导致该技术应用的可靠性有待提高。本项目基于对煤破裂产生电荷并导致电荷运动而诱发电磁辐射的认识，拟进一步研究解决煤破裂如何产生电荷并导致电荷分布、煤破裂导致裂纹如何扩展振动进而影响电荷运动的基础科学问题。本项目将对典型煤微结构进行定量加载和微观测试，研究煤微表面静态和加载时的电性特征，揭示裂纹扩展电性产生机制及其特征规律；开展典型煤样宏观加载实验，研究煤破裂裂纹扩展振动特征及电磁辐射波形特征和幅频特性，揭示裂纹扩展振动对宏观电磁辐射的影响规律；在此基础上，研究裂纹扩展振动对周边电荷运动的影响，建立带电裂纹扩展及壁面振动诱发电磁辐射机理模型，揭示煤破裂瞬态电磁场与破裂和电性的本构关系；最后，采用预制裂纹煤样加载电磁响应进行验证和完善。预期成果可进一步发展煤岩电磁辐射理论和技术。

我国冲击地压灾害严重，煤岩电磁辐射技术在冲击危险性监测预警方面具有优势，已在煤矿大量应用。然而，煤岩电磁辐射机理不清导致该技术应用的可靠性有待提高。本项目研究发现了煤岩微表面的电性特征及煤岩破裂裂纹扩展振动特征，揭示了带电裂纹扩展振动诱发电磁辐射机理，并进行了实验验证。主要成果为：.①研究了煤岩微表面静态和加载时的电性特征，以及电性产生及变化的机制，发现煤岩微表面电势可达几十至上百mV，且分布不均匀，存在局部正/负电性主导，表面电势会随加载而出现局部高低电势区的转移，变化幅度为数十mV量级，破裂时新生电荷可在表面存续；②研究了煤岩破裂裂纹扩展振动特征及对电磁辐射的影响，发现裂纹振动是裂纹壁面不断开合的先加速后减速的双向振荡过程，破裂时电磁辐射和震动信号同步产生，二者的波形特征和幅频特性具有显著相关性，裂纹及壁面振动的时空特征与电磁辐射具有关联性；③研究了裂纹扩展振动对电荷运动的影响，发现电荷运动是裂纹壁面振荡带动的电荷振荡运动，电磁辐射由带电裂纹振动产生，裂纹壁面原生电荷及新生电荷是电磁辐射的电性基础，裂纹扩展振动是电磁辐射的动力源，据此构建了带电裂纹扩展振动诱发电磁辐射理论模型，揭示了煤岩破裂瞬态电磁场与破裂和电性内在联系；④利用室内实验验证了电磁辐射理论模型的合理性，结果表明，模型计算得到的电磁辐射波形与实测电磁辐射波形具有较好相关性；⑤出版英文专著1部，发表学术论文27篇，其中SCI论文19篇,授权发明专利13项，获省部级科技进步一等奖1项、二等奖4项，培养博士生2名，硕士生1名，国际交流访学2人。.研究成果解决了煤破裂如何产生电荷并导致电荷分布、煤破裂导致带电裂纹如何扩展振动进而诱发电磁辐射的基础科学问题，进一步发展了煤岩电磁辐射理论；同时，将进一步提高电磁辐射技术在矿山动力灾害监测预警领域应用的可靠性。