Experimental Study on the Thermal Infrared Spectral Variation of Fractured Rock

Previous studies have shown that thermal infrared radiation (TIR) anomalies occur in the vicinity of fractures that form when a rock is loaded to failure. Different types of fracturing modes correspond to different TIR anomaly trends. However, the spectral features and the mechanisms responsible for the TIR changes in the fracturing stage remain poorly understood. In this paper, experiments involving observations of the thermal infrared spectrum (8.0-13.0 mu m) of loaded sandstone during the fracturing stage were conducted under outdoor conditions. The experiment yielded the following results: (1) Different fracturing modes can lead to different trends in the spectral radiance variation; (2) when an extensional fissure appeared on the rock surface, the radiance increased with a local peak in the 8.0-9.7 mu m range; (3) when local bulging formed at the surface, the radiance decreased, with a local valley in the 8.0-9.7 mu m range. The radiance variation caused by morphologic changes is the combined result of changes in both the temperature and the emissivity. The characteristic waveband corresponding to the reststrahlen features (RF) of quartz was mainly related to the emissivity change. This study provides a preliminary experimental foundation for the detection of crustal surface fractures via satellite-based remote sensing technology.

Automated summary

Different types of fracturing modes exhibit different trends in thermal infrared (TIR) radiance variation. Experimental observations show that extensional fissures lead to increased radiance with a local peak in the 8.0-9.7 µm range, while local bulging results in decreased radiance with a local valley in the same range. These changes in radiance are influenced by both temperature and emissivity variations, with the characteristic waveband relating to quartz emissivity changes.