The mechanical characteristics and mechanisms of rock failure involve complex rock mass mechanics problems involving parameters such as energy concentration, storage, dissipation, and release. Therefore, it is important to select appropriate monitoring technologies to carry out relevant research. Fortunately, infrared thermal imaging monitoring technology has obvious advantages in the experimental study of rock failure processes and energy dissipation and release characteristics under load damage. Therefore, it is necessary to establish the theoretical relationship between the strain energy and infrared radiation information of sandstone and to reveal its fracture energy dissipation and disaster mechanism. In this study, an MTS electro-hydraulic servo press was used to carry out uniaxial loading experiments on sandstone. The characteristics of dissipated energy, elastic energy, and infrared radiation during the damage process of sandstone were studied using infrared thermal imaging technology. The results show that (1) the transition of sandstone loading from one stable state to another occurs in the form of an abrupt change. This sudden change is characterized by the simultaneous occurrence of elastic energy release, dissipative energy surging, and infrared radiation count (IRC) surging, and it has the characteristics of a short duration and large amplitude variation. (2) With the increase in the elastic energy variation, the surge in the IRC of sandstone samples presents three different development stages, namely fluctuation (stage Ⅰ), steady rise (stage Ⅱ), and rapid rise (stage Ⅲ). (3) The more obvious the surge in the IRC, the greater the degree of local damage of the sandstone and the greater the range of the corresponding elastic energy change (or dissipation energy change). (4) A method of sandstone microcrack location and propagation pattern recognition based on infrared thermal imaging technology is proposed. This method can dynamically generate the distribution nephograph of tension-shear microcracks of the bearing rock and accurately evaluate the real-time process of rock damage evolution. Finally, this study can provide a theoretical basis for rock stability, safety monitoring, and early warning.

The infrared radiation response characteristics and mechanisms of sandstone samples under uniaxial compression were investigated using infrared thermal imaging and strain measurement techniques. The stress–strain curves were divided into different damage stages (i.e., crack closure, elastic deformation, stable crack growth, unstable crack growth, and post-failure) by the damage thresholds determined using the transverse and vertical strains. Experimental results show that the infrared radiation response characteristics of sandstone include the superposition of different mechanisms, which lead to either temperature increase or decrease. The response mechanisms of infrared radiation vary depending on the damage stage. During crack closure and elastic deformation stage, temperature variations are mainly governed by thermoelastic effects and the nearly adiabatic compression of air in the pore space. In the stable and unstable crack growth phase, the temperature variations are dominated by two reverse acting processes: heat production by frictional sliding and cooling by the expansion of gases in pore spaces. This leads to complex inhomogeneous radiation and consequently temperature distribution at the sample surface with local hotspots.