Oil Shale, Vol.37, No.1, 70-88, 2020
Correlation between the surface infrared radiation and deformation characteristics of oil shale during uniaxial compression
The emission of infrared radiation from oil shale is, compared with other rocks, more intense due to the anisotropy during deformation. In this research, cracks in oil shale specimens were scanned with computed tomography (CT) scanning equipment, and the infrared radiation from their surface, as well as surface strain during uniaxial compression were analyzed. The results show that the specimens surface temperature constantly changes. Prior to the fluctuation of the internal stress of a test specimen, the temperature curve exhibits varying degrees of decline. Then the curve abruptly rises close to the specimen's point of failure. By analyzing the coefficient of variation of the surface temperature distribution of the specimens, it was found that the turning point on the curve from the horizontal fluctuation to rapid increase can serve as a warning of impending specimen failure. In a low-stress state, the location of a crack is indicative of the low-temperature infrared anomaly. With increasing stress, the high-temperature infrared anomaly will appear at the crack tip. Near the failure of the specimen, the appearance of an anomalous infrared precursor on its surface is related to the mode of failure. A high-temperature infrared precursor will occur in a shear failure zone, while a low-temperature infrared precursor will occur in a tensile zone. These regularities are very important to be taken into account to understand the development of the internal fracture network and deformation of oil shale deposits during insitu pyrolysis.