Effect of Freeze–Thaw Cycle Times on Basic Properties and Bond Performance with Steel Reinforcement of Tunnel Lining Concrete in the Tibetan Plateau

To investigate the bond performance between reinforcement and tunnel lining concrete under freeze–thaw cycles in plateau regions, pull-out tests were conducted on secondary-lining-reinforced concrete specimens subjected to different numbers of freeze–thaw cycles. The variations in the fundamental properties of the lining concrete, as well as the bond stress and maximum slip between the reinforcement and the concrete, were examined. The results indicate that, with an increasing number of freeze–thaw cycles, the mass of the lining concrete first increases and then decreases, while the compressive strength and splitting strength gradually decrease. The bond stress between the reinforcement and concrete shows a decreasing trend, whereas the maximum slip exhibits an increasing trend. Furthermore, a finite element model of the reinforced concrete pull-out specimen was established using ABAQUS software to simulate the bond performance under different freeze–thaw cycles. The comparison between experimental and simulated results validates the rationality of the finite element model. This study provides a reference for understanding the bond–slip behavior of tunnel lining reinforced concrete subjected to freeze–thaw environments in cold plateau regions.