Thermal radiation characteristics of stress evolution of a circular tunnel excavation under different confining pressures

The infrared thermography has been tested herein for the study of the thermal radiation characteristics of stress evolution induced by a circular tunnel excavation during the biaxial compression tests of the similar material, together with the uniaxial compression test for the cylindrical specimen of the same material. The results showed that the stress curve of the cylindrical specimen displayed some larger fluctuations while the average infrared radiation temperature (AIRT) curve decreased with time. The correlations between the axial stress of the cylindrical specimen and its surface thermal radiation temperature presented distinctly two stages, namely negative nonlinear correlation in the front-peak curve and linear correlation in the post-peak curve. The cylindrical specimen demonstrated a tensile failure mode and showed the cooling effect. Under biaxial uniform compression, the temperature field and the stress field of the surrounding rock displayed a homogeneous state after the circular tunnel excavation. Maintaining the horizontal load constant and continuing to increase the vertical load, the thermal radiation temperatures on the specimen surface demonstrated a significant change after the circular tunnel excavation, which verified the consistency of the dynamic evolution process of the temperature field and the stress field during the circular tunnel excavation. The results obtained in the study lay the foundations for future studies focusing on the utility of the infrared thermography in the similar engineering.