Characteristics and generation mechanisms of key infrared radiation signals during damage evolution in sandstone

Infrared radiation count (IRC) is considered as an indicator for damage evolution of rocks. This new indicator links damage intensity and corresponding infrared radiation temperature. As demonstrated exemplary for sandstone, the sudden change of IRC can be considered as a damage indicator for rocks under loading. All samples showed IRC sudden changes around the peak stress, and 75% of the samples showed sudden changes before reaching the peak stress. Therefore—considering that infrared camera covers only about 25% of sample surface—IRC can be used as an early warning signal for rock failure. IRC variations are mainly related to energy release during the energy transformation process from elastic strain energy into fracture energy, heat and seismic energy. IRC is randomly distributed over the whole sample surface with very low values in the quasi-elastic deformation stage, but with the onset of local cracking, sudden and significant changes occur. The use of IRC as a nondestructive failure precursor in laboratory tests is recommended.