Thermal infrared spectrum variation and waveband features of loaded rocks with different mineral components during the fracture evolution process

Previous studies focused mainly on temporal -spatial analyses of thermal infrared radiant temperature variations based on statistical parameters for rocks. These spectral analyses indicated that the thermal infrared radiance variation during the rock loading and fracturing process was a combined effect of the changes in both temperature and emissivity variation. The spectral features and mechanisms responsible for the thermal infrared spectral radiance changes in the fracturing stage and the relationship to the lithology remain poorly understood. In this paper, three types of typical rocks on the earth ground surface with different mineral components, i.e., sandstone, granite, and marble, were selected to investigate the thermal infrared spectrum (8.0-13.0 mu m) waveband regulation during the loading process in the outdoor condition. The experiment yielded the following results: (1) The advantageous waveband corresponded to the reststrahlen feature (RF) waveband of the static emissivity spectrum, which was in the 8.2-9.4 mu m, 8.4-10.3 mu m and 11.1-11.4 mu m range for sandstone, granite, and marble, respectively. There is a significant influence on the thermal infrared radiance variation caused by the waveband range. (2) The emissivity changes during the fracturing stage were the main factors causing the spectral radiance change, with opposite waveband features of the temperature change leading to an overall increase in amplitude. (3) The combination of spectral features in the advantageous waveband was more conducive to the analysis of the temporal -spatial -strength evolution of the thermal infrared radiation (TIR) temperature field on the loading rock surface. These results provide a scientific basis for thermal infrared remote sensing satellite loading design and waveband optimization and combination configuration.