Effect of Rock Properties on Electromagnetic Radiation Characteristics Generated by Rock Fracture During Uniaxial Compression

The phenomenon of electromagnetic radiation (EMR) generated by rock fracture is relatively common. Due to different properties of rock, the variation laws and distribution characteristics of signals in time and frequency domain are significantly different. In this paper, the uniaxial compression experiments of four different kinds of rocks were carried out under the same loading conditions. EMR response characteristics during loading were studied, and the relationship between EMR signal statistics and mechanical parameters or quartz contents of rocks were analyzed. However, quartz content is not a decisive factor since quartz-free rock can also produce significant EMR signals when it fractures. Quartz content does not stimulate the activity and intensity of EMR signals generated by rock fracture. For the same kind of rock, specimen with larger elastic modulus tend to exhibit higher EMR signal intensity. Activity of EMR signals is not strictly proportional to the compressive strength of rocks but affected by complex stress-induced crack events during the loading process. With the continuous evolution of cracks, the dominant frequency of EMR signal shifts from a higher band to a lower frequency. As the quartz content decreases, the dominant frequency of EMR signal appears in a higher frequency band.