## 1 Introduction  
In recent years, China's intensified investment in new energy construction has spurred the rapid development of nuclear power as a viable alternative. Currently, most nuclear power plants in China are situated in coastal areas, utilizing seawater once-through cooling systems that require substantial water intake. Immersed tunnels are widely employed in these systems due to their minimal sea surface area requirements, eco-friendliness, cost efficiency, and straightforward construction. Given China's susceptibility to earthquakes, many plant sites are located in regions with high seismic activity. Earthquakes present a significant threat to the safety of nuclear power facilities, making seismic performance a critical concern in the construction of these projects. Currently, a well-developed research system exists for seismic studies in underground engineering. Seismic response data have been analyzed using scaled-down tunnel models designed for indoor shaking table tests. [PERSON] et al. [1] proposed a design method for a compartmental particle damper suitable for immersed tunnels. They constructed a 1:60 scale model of an immersed tunnel and performed shaking table tests before and after installing the particle dampers. [PERSON] et al. [2] based their research on the Hong Kong-Zhuhai-Macao Bridge immersed tunnel project, conducting shaking table model tests on immersed tunnel systems under three site conditions (dry sand, saturated sand, and underwater saturated sand) with modelsat a 1:30 scale ratio. [PERSON] et al. [3] investigated the dynamic response characteristics of immersed tunnel structures and their joints using shaking table tests, considering longitudinal traveling wave excitation with varying apparent velocities. [PERSON] et al. [4] performed compression-shear tests on joints at a 1:10 geometric scale, examining their mechanical properties under low cyclic loading. [PERSON] et al. [5] conducted underwater shaking table tests on small-scale immersed tunnel models to measure seismic response data. [PERSON] et al. [6], through shaking table tests, explored the effect of unsaturated soil foundations on internal force distribution in immersed tunnels. [PERSON] et al. [7] analyzed the displacement behavior of immersed tunnels under seismic activity, providing valuable references for seismic studies. [PERSON] et al. [8] performed shaking table tests under multi-dimensional seismic waves, focusing on the tunnel-soil system to study the dynamic response of tunnels and surrounding soil. With the continuous advancement of finite element method theory and computer technology, numerical simulation has become a prevalent and cost-effective method for studying the dynamic responses of underwater structures. [PERSON] [9] developed a mechanical model to examine the interaction between immersed tunnels, soil, and fluid. Using the Newmark algorithm, he investigated stress changes in immersed tunnel structures under various seismic excitations and water depth conditions. [PERSON] et al. [10] considered the dynamic nonlinear properties of seabed soil and tunnel concrete, along with the coupling effects between seawater and the seabed, developing a finite element model to analyze the interactions among seawater, seabed, and tunnel, focusing on the seismic response of undersea tunnels. [PERSON] et al. [11] utilized finite element software ADINA to create an integrated model of seawater, immersed tunnels, and the seabed, analyzing the seismic responses of immersed tunnel structures under various conditions, specifically with vertically incident seismic P-waves. and effectively addressing deformations due to temperature and water pressure, concrete shrinkage, and stratum movements. [PERSON] et al. (2019) determined the minimum compression necessary to ensure the watertightness of GINA water stops using the average water pressure method and the contact stress method, establishing a safety warning level based on the remaining compression. [PERSON] et al.