Improved Deformation Calculation Method for Immersed Tunnels Considering Siltation Effects: A Case Study of the Yongjiang Immersed Tunnel in Ningbo, Zhejiang Province, China

This paper introduces an advanced method for calculating the deformation of immersed tunnels when accounting for the impact of repeated siltation loads during maintenance. Based on the insights into the force and deformation characteristics of segmental immersed tunnels, the Timoshenko beam model, which considers bending and shear deformation and is based on the Kerr foundation model (KTM), is used to accurately simulate tunnel–foundation interactions, which simulates the continuity between foundation spring elements and more adequately represents the connection and distinction between the easily compressible soil layer and the less compressible soil layer of the foundation. By its application to the Yongjiang immersed tunnel, this method demonstrates significant improvements in predictive accuracy compared to the two-dimensional settlement (TDM), Euler–Bernoulli (WEM), and Timoshenko model based on the Winkler foundation (WTM). Of note, settlements that result from siltation loads display exponential growth over time, with dredging frequency exerting a discernible influence. These findings have substantial implications for the design and operational management of immersed tunnels, which offer advanced insights to enhance their structural integrity and operational longevity.