Estimating the change in the stress state of soils and rocks from the change in the flux intensity of infrared radiation from their surface

Features of thermomechanical effects in rock salt samples under uniaxial compression

“…They involve the change in temperature of a solid upon varying the first invariant of stress tensor [3,12] and the relationship between the intensity of infrared radiation from a solid surface and the temperature [3,13]. As previously shown [8][9][10], such approach can become effective for the contactless measurements of elastic stresses in geomaterials.…”

“…The experiments were carried out on the samples made of rock salt, which features higher thermal activity, i.e. higher level of IR-radiation intensity changes for the common stress variations, in comparison with the examined geomaterials (marble, limestone, concretes, and so on) [8][9][10]. Moreover, the listed rocks tend to fracture in a brittle manner, while rock salt under uniaxial compression is characterized by a large difference between the elastic limit e σ and ultimate strength c σ [15,16].…”

“…The authors of [8][9][10] emphasize the necessity to meet the technological requirement to IR diagnostics of changing the stress state of geomaterials, namely, to fulfill the conditions of quasiadiabaticity of the deformation process during testing. This means the absence of the heat exchange between the deformed solid and the environment [3,12].…”

“…The current methods are based on using the mentioned effects, which appear under changes in the state of geomaterials and allow the information of them to be found [6][7][8][9][10][11].…”

“…As in [8][9][10], RTN-31 is used as the primary infrared radiation detector [14] meant for the contactless measurement of optical radiation intensity in the infrared spectrum of wave lengths. IR radiation detector 1 is fixed approximately at the center of sample 2 at a distance of 0.5-1 cm from its surface.…”