Research on vector characteristics and applications of electromagnetic radiation induced by rock failure

Abstract

Coal and rock electromagnetic radiation (EMR) measurement plays an essential role in the monitoring and early warning of underground engineering dynamic hazards as a real-time, dynamic, non-contact geophysical monitoring method of coal and rock fissure. The electromagnetic field has obvious directionality; however, the EMR measurement instruments used in underground engineering are scalar rather than vector instruments. Therefore, this paper uses a self-developed three-axis antenna to measure the vector EMR for rock Brazil splitting failure. Study the influence of crack size (D), the distance of measuring point (r) and crack azimuth angles (θ 0) on the vector characteristics of EMR induced by rock splitting failure. Analyze the vector response mechanism of EMR induced by rock splitting failure, and conduct on-site vector EMR measurements in the Lilou Coal Mine. The study achievements are concluded as follows: the amplitude of vector EMR ( A s) increases linearly with the increase of crack size (D), decreases with the distance square (r 2) from the measurement point to the crack increases, and increases and then decrease with the increase of angles (θ 0) between the sample direction and the initial fixed position, showing arching changes; The direction of vector EMR ( A s) is mainly affected by θ 0 impact. The results of experiments are consistent with that of theoretical analysis. The field measurement results show that the stress concentration area and its orientation of the roadway could be measured using the three-axis vector EMR instrument we researched and developed.