Evolution Law of Bearing Performance of Tunnel in Cold Regions Considering Gradual Deterioration of Lining

There are temperature differences in the radial depth of tunnel lining, resulting in varying degrees of continuous gradual degradation along the radial direction under freeze-thaw cycles. In order to investigate the effect of gradual degradation of lining on the bearing performance of tunnel in cold regions, Yangbajing No. 2 Tunnel was taken as the engineering basis in this study. Through on-site temperature testing, combined with numerical simulation calculations of tunnel temperature field and stress in lining structure, the evolution laws of the bearing performance of tunnel in cold regions with gradual deterioration of lining was investigated. The findings indicate that under the repeated effect of positive and negative air temperature changes occurring approximately 170 times per year, the tunnel lining surface experiences about 11 equivalent indoor freeze-thaw cycles. With the increase of radial depth, the number of freeze-thaw cycles experienced by the lining decreases exponentially. The compressive strength and elastic modulus of the lining concrete also deteriorate exponentially along the radial depth, which is mainly concentrated within a depth range of 35 cm from the lining surface. Under the condition of gradual degradation of lining, as the service years increase, the eccentricity of the arch section gradually increases, and the height of the compressed zone decreases, resulting in a large eccentric compression. The safety factor of the lining decreases at a fast rate, leading to serious deterioration of the bearing performance. On the contrary, in the case of full-section deterioration of lining, the compression state at the arch crown gradually changes from large eccentricity to small eccentricity, resulting in a slower decrease in the safety factor and less degradation in bearing capacity. The remaining sections exhibit similar changes in the bearing capacity of the lining under both deterioration conditions. Therefore, in the long-term durability design of tunnel lining, the gradual degradation of concrete along the radial depth must be considered for the arch section.