Temperature‐dependent shear behavior and constitutive model of the rock–concrete interface

Abstract Shear tests were conducted at a shear rate of 1 mm/min and a shear displacement of 10 mm to investigate the effect of temperature on the shear behavior of the rock–concrete interface, with the aim of revealing the interaction between the surrounding rock and the lining during tunnel fires. The experimental results obtained several key findings: The mechanical properties of rock and concrete deteriorated with temperature. The mass loss rate of rock was 1.28%, with a decrease in compressive strength of 22.77%. The mass loss rate of concrete was 7.79%, with a decrease in strength of 33.27%. Concrete is more sensitive to temperature than rock under the experimental conditions. As the temperature rose, the shear fracture surface gradually shifted from within the concrete to the rock–concrete interface. Simultaneously, compaction shear displacement and peak shear displacement increased, while peak shear stress, shear stiffness and interface fracture energy decreased. In particular, the increase in compaction shear displacement and the decrease in shear stiffness were characteristic of the shear behavior of the rock–concrete interface at elevated temperatures. Subsequently, a temperature‐dependent shear constitutive model of the rock–concrete interface, based on damage mechanics and statistical theory, was developed to eliminate reliance on specific experimental variables and serve as a reference for similar situations beyond the experimental conditions. This study contributes to advancing our understanding of the shear behavior of the rock–concrete interface at elevated temperatures.