Triaxial Compressive Strength, Failure, and Rockburst Potential of Granite Under High-Stress and Ground-Temperature Coupled Conditions

Deep underground rock tunnels and caverns in mountainous areas are often subjected to the coupling impacts of high geo-stresses and high-ground temperature that can threaten the stability of rock masses. This paper presents an experimental study of strength, deformation, and failure as well as energy evolution characteristics for rockburst potential evaluation of granite under the influence of coupled high confining pressure and ground temperature using a series of triaxial compression tests with samples drilled from a borehole about 1000 m in the depth of a mountain tunnel in Tibet area. Three representative confining pressures (20, 40, and 60 MPa) and four typical temperatures (30, 60, 90, and 120 celcius) around the engineering range were inspected according to the previous tunnel site investigations. The strength and deformability of the granite samples were analyzed under the influence of coupled high confining pressure and temperature. An energy storage index is introduced to discuss rockburst potential of the granite under thermal-mechanical coupled conditions. It is found that high-ground temperature leads to degradation of mechanical properties of the granite samples, while high pressure increases its strength and deformability. In addition, the high pressure and ground temperature couplings increase both the energy storage capacity and rockburst potential, with 60-90 celcius being the strengthening range. The findings are beneficial to understanding the behavior of surrounding rock masses, the evaluation of its stability, and rockburst potential for deep underground tunnels in areas with high in-situ stress and ground temperature.