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.

The existing research shows that the immersed tunnel is significantly affected by the earthquake, but the damage will cause serious casualties and property damage, and it is difficult to repair. However, the shaking table test of immersed tunnel including seabed and seawater site is difficult to realize at present, and numerical simulation is generally used for analysis. It has been found that seawater layer, seabed site conditions and soil-structure interaction have a large effect on the seismic response of immersed tunnels, but most of the existing studies have used two-dimensional models to analyze. In order to determine the influence of three-dimensional seabed site on the seismic response of immersed tunnel. Firstly, a three-dimensional layered site wave analysis program was established by using the coordinate system transformation and transfer matrix method, and combined with the finite element dynamic analysis software, a three-dimensional seismic wave analysis method of seawater and seabed immersed tunnel coupling was proposed. Besides, the correctness of the method is verified, and the influence of multi-dimensional site characteristics on seismic response of seabed site is analyzed. Finally, the immersed tunnel of Hong Kong-Zhuhai-Macao Bridge in China is taken as an engineering example, and the effects of tunnel longitudinal slope, incidence angle of ground motion, thickness of soft soil layer and water depth on seismic response analysis are studied. The results show that there is a great difference between twodimensional and three-dimensional seabed site model in seismic response. When considering the soft soil layer, the vertical seismic response of three-dimensional seabed site is significantly greater than that of twodimensional seabed site.Moreover, the silty soft soil layer also has a significant effect on the seismic response of the immersed tunnel, there is an obvious amplification effect on the tunnel horizontal seismic response. Besides, the horizontal seismic response of tunnel will be amplified with the increase of tunnel longitudinal slope and incidence angle, while the seismic response of tunnel will be inhibited with the increase of seawater depth.

Immersed tunnels, as a form of underwater transportation engineering offering numerous advantages, have been widely deployed in coastal and riverside cities. However, due to the shallow burial and underwater characteristics, immersed tunnels present significantly different surrounding soil and water environments compared to land-based tunnels. Currently, there is limited research on the seismic analysis of submarine immersed tunnels, raising questions about the direct application of the methods of land-based tunnels. In this study, the Davidenkov soil constitutive model is introduced to simulate the strong nonlinearity of deep sedimentary soil in marine areas. The Coupled Acoustic-Structure (CAS) method is employed to simulate the dynamic interaction between seawater and seabed. A time-history analysis model is developed to capture the coupling interactions between seawater, seabed, and tunnel structure. The effects of the soil-tunnel contact mode and seismic input method on the seismic responses of immersed tunnels are investigated in detail. Seismic response characteristics of immersed tunnels are analyzed from four perspectives: distribution of tensile damage in the tunnel, maximum inter-story drift ratio, maximum bending moment, and tunnel inclination angle in the cross-sectional direction. The results indicate that the overlying seawater and sand compaction piles negatively impact the seismic performance of immersed tunnels in the scenarios of this study. Furthermore, their impact pattern and extent are closely correlated with the intensity of the input seismic motion.

For evaluating the post-earthquake failure probability of the immersed tunnel of Hong Kong-Zhuhai-Macao Bridge subjected transverse earthquake loading. A two-dimensional (2-D) finite element model considering the water-soil-tunnel interaction has been built based on the Abaqus software platform, and a more refined threedimensional(3-D) model was built to examine the preciseness of the 2-D model in calculating the displacement response of immersed tunnel. The seismic damage evaluation of immersed tunnel was presented based the numerical analysis results of 3-D model, and it indicated the IDR is significant related to the damage level of tunnel. The inter-story drift ratio limits of immersed tunnel were defined based on the seismic performance curve obtained from the Pushover analysis. The non-linear dynamic analysis was performed for the 2-D model subjected different amplitude-modulated earthquake records according to the incremental dynamical analysis (IDA) procedure. The IDA curve cluster and corresponding 16 %, 50 %, 84 % percentile lines were plotted by defining the damage measure as the inter-story drift ratio, and employing the PGA to describe the intensity measures. The probability of the immersed tunnel exceeding different seismic performance level subjected different earthquake intensity have been given, and the finding shown the immersed tunnel perform enjoying good seismic performance.