Assessment of structural performance of super large cross-section subsea RC shield tunnels: Emphasis on the combined effects of highly hydrostatic pressure and corrosion-induced deterioration

For the subsea reinforced concrete (RC) shield tunnels in China, the use of super large tunnel section and the presence of high hydrostatic pressure from seawater have been becoming increasingly common in practical engineering. However, owing to the combined effects of complex structural systems, extreme external loads and aggressive environments, it is a great challenge to sustain a reliable structural performance of these subsea shield tunnels within the prescribed service life. In this study, a novel approach for evaluating the structural safety of a deteriorated large-section subsea RC shield tunnel is presented with an emphasis on the spatial correlation and variation of corrosion damages and the impact of high hydrostatic pressure. Gumbel distributed random fields are established to simulate the spatial variability of steel corrosion in the segmental linings. A random field-based numerical model for the deteriorated RC segmental linings is developed in conjunction with the modeling of nonuniform steel corrosion and local-regional material degradation. In an illustrative example, the effects of the corrosion degree of internal and external steel reinforcements and the level of applied hydrostatic pressure on the structural safety of a large-section subsea RC shield tunnel are investigated. •Random field-based modeling for nonuniform steel corrosion is introduced.•Deteriorated performance of shield tunnels with a super large cross-section is revealed.•Bending moment is much sensitive to the change of corrosion state in segment.•Steel corrosion in tunnel extrados can cause a greater deterioration deformation.•High hydrostatic pressure exacerbates the serviceability and safety of degraded tunnels.