New approach to monitoring and characterizing the directionality of electromagnetic radiation generated from rock fractures

Electromagnetic radiation (EMR) is a common phenomenon widely used in engineering and geology fields for detection and monitoring. Although there are some attempts to monitor the directionality of electromagnetic radiation, they are limited by the inability to perform multi-directional measurements at the same time. As a result, the directionality of electromagnetic radiation induced by rock fracture is less involved. Here, four symmetrical three-axis antennas are used to monitor the fracture-induced electromagnetic radiation signals and characterize directionality during uniaxial compression experiments of limestone and granite. The synthesized signals of the four antennas are obtained based on the principle of vector synthesis. Signals monitored on the three axes differ significantly with the direction as the three electromagnetic field components are at the same position. The resultant vectors at the maximum intensities and the equivalent vectors calculated by energy ratio are used to characterize the directionality of electromagnetic radiation caused by fractures. The direction of those vectors shows an obvious correlation with the crack surface. Based on the above research, a new approach using electromagnetic radiation directionality to monitor the stress state and failure in engineering and geological sites is established.