煤岩破裂电磁辐射矢量特征规律

Vector characteristics and laws of electromagnetic radiation generated from coal rock fracture

煤炭等资源的安全开采是保障我国能源安全的关键.随着开采强度和深度的不断增加,煤与瓦斯突出等煤岩动力灾害严重威胁着煤炭安全高效开采.电磁辐射技术作为一种实时、非接触、前兆性强的地球物理监测方法,在煤岩动力灾害监测预警等方面发挥了重要作用.但当前电磁辐射理论与技术研究主要针对标量参数进行,忽略了电磁场本身包含的空间矢量特征.基于此,利用自主研发的三轴电磁天线,根据矢量合成原理研究了煤岩破裂产生的电磁辐射矢量特征规律.结果表明:煤岩破裂过程产生的三轴电磁信号在时域上具有明显差异性,而在频域上分布较为一致,可视为破裂产生的电磁场在3个方向上的分量,并且该矢量电磁场在试样周围呈非均匀分布状态;通过三轴电磁信号的方向性差异可表征电磁辐射矢量,其等效矢量方向与裂纹面方向表现出明显的相关性;煤岩破裂产生的矢量电磁场是多个微裂纹综合作用的结果,多频电磁信号可视为不同方向、不同频率的多个偶极子受迫振荡和阻尼振荡产生的电磁效应叠加;现场测试表明利用电磁辐射矢量特征规律可辅助判识断层区域和危险程度.研究结果有助于进一步揭示煤岩破裂全过程破裂性态的时空演化规律,为实现非接触、时空定位精细化的煤岩动力灾害监测预警奠定基础.

The safe mining of coal and other resources is the key to guaranteeing energy security.With the continuous increase in mining intensity and depth,coal and gas outburst and other dynamic disasters pose a serious threat to the safe and efficient mining.As a real-time,non-contact,and highly precursor geophysical monitoring method,electromagnetic radiation(EMR)technology has played an important role in monitoring and warning of coal-rock dynamic disasters.Current research primarily focuses on scalar parameters,overlooking the spatial vector characteristics inherent in the electromagnetic field.Therefore,based on the principle of vector synthesis,the vector characteristics of fracture-induced electromagnetic signals were studied using a self-developed three-axis electromagnetic antenna.Electromagnetic signals on the three axes have obvious differences in the time domain,while the distribution in the frequency domain is relatively consistent.They can be regarded as the components of the electromagnetic field in the three directions.Generated vector field is non-uniformly distributed around the specimen.The directional difference of signals can be used to characterize vectors.There is a clear correlation between the direction of the equivalent vector and the crack surface.The vector electromagnetic field results from combined effects of multiple microcracks.Multi frequency signals can be regarded as the superposition of electromagnetic effects generated by forced and damped oscillations of multiple dipoles in different directions and frequencies.On-site tests show that the use of electromagnetic vector characteristics can assist in identifying fault areas and hazard levels.The research results contribute to further revealing the spatiotemporal evolution of the fracture behavior throughout the entire fracture process.This can lay the foundation for the monitoring and early warning of coal-rock dynamic disasters in a non-contact,spatiotemporal and precise manner.