Thermomechanical failure analysis of sandstone subjected to high ground temperature

The temperature effect of rock failure has primarily focused on high temperature and large temperature gradients. However, the temperature range of engineered rocks in high ground temperature tunnel is generally within 100 °C. For this, this study conducts real-time thermomechanical coupling tests with small temperature gradient within the engineering temperature. We analyzed rock mechanical parameter, rock failure characteristics, and acoustic emission (AE) and energy characteristics. The results indicate that the strength, peak strain, elastic modulus, and peak energy storage of sandstone decrease with increasing temperature. The peak AE count of sandstone in triaxial test at high temperature decreases with increasing temperature. The RA (Rising time/Amplitude) and AF (Average frequency) parameters associated with the AE signals indicate that the shear and tensile cracks are produced almost simultaneously throughout the rock failure process with increasing temperature. The PFC (particle flow code) simulation results show that the crack number of PBM (parallel bond model) specimen at high σ 3 is significantly higher than that at low σ 3 and the cracks number difference under high and low σ 3 also rises as the temperature increases. Finally, the strength attenuation characteristics are explained by the competition and coupling action of temperature and σ 3 . This paper provides theoretical insights into rock failure mechanisms under thermomechanical coupling related to underground engineering.