Electromagnetic radiation characteristics and mechanical properties of deformed and fractured sandstone after high temperature treatment

Abstract In this paper, the electromagnetic radiation (EMR) characteristics and mechanical properties observed during sandstone deformation and fracture after high-temperature treatment were studied. The sandstone mechanical strength was found to decrease after high-temperature treatment. EMR signals and acoustic emission (AE) signals were produced during the process of sandstone deformation and fracture. The EMR signals increased with the increase in stress. The EMR signals' change trend was varied after different temperature treatments. Overall, the change trend of EMR and AE signals was consistent, but not strictly synchronized. In addition, the mechanisms of generation of the EMR and AE signals were different. The EMR signals were consistent with the Hurst statistical law, with the Hurst index being greater than 0.5. The main frequency of the EMR signals increased with the increase in stress. At the initial loading stage, the main frequency of EMR signals was low and its intensity was small. With the increase in temperature, the intensity of the EMR signals increased at the same stress level. As the loading increases, the main frequency and the EMR intensity fluctuated significantly. Under conditions of instability and failure, the EMR frequency changed notably, and the EMR intensity reached the maximum. Application of EMR count as a damage variable reflected the sandstone deformation and fracture process. This study provides guidance for application of EMR to detect and evaluate the thermal stability of rocks after high-temperature treatment.