Heat damage and bond-slip performance of steel arch frame-concrete in high-geothermal tunnels

According to the real construction environment in high-geothermal tunnel, push-out test on fifty-four I-shaped steel and concrete samples subjected to different relative humidity and variable temperature curing conditions were carried out to evaluate the bond slip performance at the interface. The study results indicated that there are three models of crack evolution in failure process under different curing conditions. Compared with the samples cured under standard condition, higher curing temperature contributes to the early development of bond strength, but the long-term bond strength decreased significantly. Relative humidity is beneficial for increasing the intensity and shearing stiffness, enhancing bonding properties and reducing the loss of long-term bond strength of samples cured under VTC condition. More initial defects lead to the weak slip resistance of the interface under hot and dry environment. According to the regression analysis of experiment data, the formula of characteristic strength and segmental constitutive equation of the bond-slip under coupling effect of temperature and humidity are obtained. The parametric finite element model (FEM) of the new constitutive relation proposed in this paper was established using parametric design language. The final results may contribute to provide a reference for related support design and construction in high geothermal tunnel.