Service safety assessment of submarine shield tunnels considering corrosion deterioration induced by seawater environments

Abstract Submarine shield tunnels operate in a long‐term, persistently erosive environment throughout their service life. High water pressure and complex geological conditions create a synergistic effect that leads to the progressive degradation of the tunnel structure's load‐bearing performance, which directly threatens its long‐term operational safety. To address this issue, this study first analyzes the deterioration characteristics of shield tunnel structures in seabed erosive environments. It also develops theoretical models for assessing the load‐bearing capacities of corroded segment structures and joints. Then, using the Jintang Subsea Highway Tunnel as the engineering prototype, a three‐dimensional calculation model of the submarine shield tunnel structure under erosion was established, considering key factors such as corrosion of steel bars and bolts, interface bond slip between steel bars and concrete, and concrete deterioration. The established model was applied to assess the load‐bearing performance of shield tunnel segments and their joints, thereby revealing the structural deformation patterns, failure mechanisms, and safe load‐bearing states of the tunnel under various deterioration scenarios. Finally, based on the GA‐BP neural network algorithm, a prediction model for the bearing capacity loss of submarine shield tunnel structures was constructed, and the influence of corrosion degradation parameters on the bearing capacity loss rate of shield tunnel structures was clarified. The results show that erosion‐induced deterioration significantly reduces the load‐bearing capacity of both the tunnel structure and joints, remarkably increases tunnel convergence deformation, continuously decreases the overall structural safety factor, and causes segmental joints to reach the load‐bearing limit state first. The GA‐BP model can predict the structurally safe load‐bearing state with relative accuracy, meeting engineering evaluation requirements.