###### Abstract
Due to on-site construction limitations, thoroughly investigating the deformation mechanisms of tunnel lining structures is often challenging. Nonetheless, numerical simulations can address this limitation. Using numerical software to establish a model of the tunnel and the surrounding geotechnical body allows for the flexible simulation of various working conditions of the tunnel under fluid-solid coupling conditions. [PERSON] et al. [15] considered the construction processes of tunnel lining installation, grouting material solidification, and tunnel excavation advancement to establish a refined numerical model. The results showed that the pore water pressure induced during tunnel construction is most affected by grouting support pressure, while the tunnel diameter and the compressibility of the surrounding geotechnical body have a smaller impact on the lining structure. [PERSON] et al. [16] simulated the impact of uneven water pressure on the lining structure of water-rich tunnels. The simulation results indicated that under high external water pressure, tensile failure occurs at the arch foot and invert of the lining structure, while compressive failure occurs at the crown of the lining structure due to the surrounding rock pressure. [PERSON] et al. [17] considered that groundwater infiltration reduces the mechanical properties of the surrounding rock and proposed a safety assessment method for water-rich tunnels in mudstone and sandstone formations. The reliability of this numerical assessment method was demonstrated in actual engineering projects. [PERSON] et al. [18] derived the water resistance conversion coefficient of the tunnel lining structure through numerical calculations, subsequently converting the water pressure from model tests into the actual water pressure resistance applied to the lining. The existing analytical solution for the external water pressure of circular tunnels underestimates the water pressure at the invert. To address the issue of water leakage in water-rich tunnels, [PERSON] et al. [19] proposed an analytical solution for the distribution of external water pressure in non-circular tunnels and corrected the analytical solution for high external water pressure distribution in tunnels based on this. The finite discrete element method (FDEM) has not been previously applied to the study of the mechanical characteristics of mudstone. Based on the FDEM method, [PERSON] et al. [20] discovered that an increase in the water content of mudstone results in a decrease in compressive strength and an increase in expansive deformation. The study results provide guidance for determining the lining structure parameters of water-rich tunnels in mountainous regions. Under high internal water pressure, DRC segments in shield tunnels develop cracks. [PERSON] et al. [21] addressed this problem by using MSC Marc to simulate the constitutive relationship distribution of DRC segments, effectively capturing their nonlinear behavior under combined loading conditions. [PERSON] et al. [22] found in their simulation of water and mud inrust in water-rich fault tunnels that the inrust particles inside the tunnel exhibit an elliptical distribution. Excessive changes in groundwater flow velocity can cause negative pore water pressure. To efficiently calculate the external water pressure on tunnel linings in horizontal strata, [PERSON] et al. [23] assumed that the strata traversed by the tunnel are entirely horizontal. They optimized the analytical solution for the external water pressure on tunnel linings and demonstrated that this theoretical solution is more accurate than the numerical solution. [PERSON] et al. [24] analyzed the deformation characteristics of tunnel lining structures in karst areas. Based on the relationship between the grouting ring and the lining structure, they proposed an analytical solution formula for groundwater level and tunnel seepage fields. The research results can help mitigate the adverse effects of karst water on tunnel linings.