Non-monotonic effect of differential stress and temperature on mechanical property and rockburst proneness of granite under high-temperature true triaxial compression

Complicated geological conditions such as high geo-stress and high ground temperatures often have a significant impact on the mechanical behavior and failure potential of hard rocks in deep engineering. This study aims to investigate the mechanical behaviors and rockburst proneness of granite under high differential stress and high temperatures in deep-buried high-temperature tunnels. A comprehensive experimental study was conducted on the coupling behavior of granite under high-temperature and high differential stress by true triaxial compression tests. The strength and failure mechanism of granite as well as their relationship with high temperature and high differential stress were revealed. The rockburst proneness of granite from a deep-buried high geothermal tunnel was assessed based on the rock's ultimate energy storage characteristics. It shows the strength, failure mechanisms, and rockburst proneness of granite, are significantly correlated to the granite high-temperature high-stress conditions. The temperatures extend the strengthening range of the intermediate principal stress on the true triaxial peak strength of the granite. With increasing temperature and differential stress, secondary vertical cracks develop quickly to induce the macroscopic failure of granite. Under high temperatures, the failure of granite changes from compressive-shear failure to tensile-shear failure at low differential stress. High temperature coupled with high differential stress strengthens approximately 1.14 times the rockburst proneness of granite. The results are important for the safe construction, and disaster assessment of deep-buried high geothermal tunnels.