The present study explored the degradation law and service life prediction of tunnel lining concrete with different mineral admixtures under coupled actions of sulfate attack (SA) and drying–wetting (DW) cycles. The deterioration resistance coefficient (DRC) of compressive strength and influence coefficients of sulfate concentration, mineral admixture content, water/binder (w/b) ratio, and curing regime on DRC were studied. After that, a new service life prediction model based on damage mechanics was developed and analyzed. Results show that, by increasing the DW cycles, the DRC first increases and then decreases. DRCs of Ordinary Portland cement (OPC), fly ash (FA), and ground granulated blast-furnace slag (GGBS) concrete linearly decrease with the increase of sulfate concentration, while the silica fume (SF) concrete displays a two-stage process; by increasing the admixture content, the DRCs of FA and GGBS concrete exhibit two distinct stages, while the SF concrete depicts a three-stage process; increasing the w/b ratio linearly decreases the DRC; the DRC of curing regime was sequenced as standard curing (SC) > fog curing (FC) > water curing (WC) > same condition curing (SCC). Based on the experimental results, the service life prediction model is applied and validated. The validation results show that the proposed model can accurately predict the lifetime of concrete with different mix proportions. Furthermore, it is found that the mineral admixture can effectively improve the lifetime of concrete, and the composite mineral admixture is more effective than a single mineral admixture in improving the lifetime of concrete.

The deterioration of rock mass and shotcrete lining has major consequences on the long-term performance of tunnels in the weak rock mass. In this study, the long-term behavior of rock mass and shotcrete in tunnels was simulated by using the three-dimensional finite difference method, considering the nonlinear deterioration mechanism. The degradation of rock mass was simulated by weakening the mechanical parameters, while the deterioration of shotcrete was modeled by decreasing the thickness. The support pressure, internal force, and displacement of the secondary lining were monitored with the gradual degradation of rock mass and shotcrete. As a consequence, the factor of safety (FoS) evolution with time was discussed. The results indicated that 1) the deterioration of both rock mass and shotcrete would significantly increase the rock pressure on the secondary lining, leading to an increase in the displacement (0–14 mm). The FoS of the secondary lining was reduced by 85%. 2) The influence of shotcrete’s deterioration on the secondary lining was relatively less, and the rock pressure on the secondary lining increased from 0 kPa to 13.8 kPa. The long-term safety of the tunnel is remarkably affected by the deterioration of rock mass, depending on the deterioration characteristics of the rock mass. Therefore, the deterioration characteristics of rock mass should be fully considered in tunnel maintenance.

This study examines freeze–thaw deterioration patterns and predicts the service life of wet-sprayed concrete with composite cementitious materials in cold-region tunnels. The microstructure and particle size distribution of four materials (cement, fly ash, silica fume, and mineral powder) were analyzed. Subsequent tests evaluated the rebound rate, mechanical properties, and durability of wet-sprayed concrete with various compositions and proportions of cementitious materials, emphasizing freeze–thaw resistance under cyclic freezing and thawing. A freeze–thaw deterioration equation was developed using damage mechanics theory to predict the service life of early-stage wet-sprayed concrete in tunnels. The results indicate that proportionally combining cementitious materials with different particle sizes and gradations can enhance concrete compactness. Adding mineral admixtures increases concrete viscosity, effectively reducing rebound rates and dust generation during wet spraying. Concrete incorporating binary and ternary mineral admixtures shows reduced early-age strength but significantly enhanced later-age strength. Its frost resistance is also improved to varying degrees. The ternary composite binder fills voids between cement particles and at the interface between paste and aggregate, resulting in a dense microstructure due to a ‘composite superposition effect.’ This significantly enhances the frost resistance of wet-mixed shotcrete, enabling it to withstand up to 200 freeze–thaw cycles, compared to failure after 75 cycles in plain cement concrete. The relative dynamic modulus of elasticity of wet-shotcrete follows a parabolic deterioration trend with increasing freeze–thaw cycles. Except for specimen P5 (R² = 0.89), the correlation coefficients of deterioration models exceed 0.94, supporting their use in durability prediction. Simulation results indicate that, across all regions of China, the service life of wet-shotcrete with ternary admixtures can exceed 100 years, while that of plain cement concrete remains below 41 years.