Theoretical damage characterization and failure precursor recognition of the rock under uniaxial compression using infrared radiation

The propagation of micro-cracks will cause the change of rock infrared radiation (IR) information, which provides the possibility to study the rock damage behavior and failure precursor using IR. In this paper, a new quantitative characterization method of rock damage evolution using IR is proposed. Firstly, the maximum classes square error and median filter methods are used to separate the temperature increment caused by crack development in IR images. On this basis, a new index, Damage Infrared Energy Response (DIER), is proposed to describe the crack evolution state and recognize the failure precursor of rock. It is found that the change characteristics of DIER and Acoustic Emission (AE) count are consistent: the DIER remains at the level in the compaction and elastic stages, rises gradually in the stable crack propagation stage, and increases sharply in the unstable crack propagation stage and fluctuates with the appearance of AE count “peak”. The change characteristics of DIER in unstable crack propagation stages can be regarded as the failure precursors of rock, about 84.10% of peak stress. Then, according to the continuum damage mechanics theory, the DIER is used to establish a theoretical characterization of the damage variable for rock, which can accurately describe the damage evolution process of the rock under uniaxial compression. The research results can provide experimental and theoretical support for monitoring slope and rock engineering stability by IR.