###### Abstract  
Water inflow analysis is critical for subsea tunnel construction. However, existing studies largely concentrate on the inflow issues pertaining to single-hole tunnels. To address current practical engineering problems, a three-hole parallel configuration is common for subsea tunnels, which may alter water inflow patterns due to the influence of their seepage fields. Herein, numerical simulations are conducted to investigate the water inflow characteristics of a three-hole parallel subsea tunnel. Specifically, the impact of various factors on the water inflow phenomenon, including the permeability coefficient of the surrounding rock, the depth of the seawater, the depth of the tunnel, the spacing between tunnels, and the relative size of the tunnels, are comprehensively studied. Furthermore, based on the principles of the analytic hierarchy process and fuzzy mathematics, an exhaustive assessment framework is developed to evaluate the water inflow of three-hole parallel subsea tunnels. The results indicate that there is a mutual influence between the three parallel tunnels, differing from the predicted water inflow, which is overestimated in a single-hole tunnel model. Therefore, the water inflow assessment for a three-hole parallel subsea tunnel system should account for the inter-tunnel influences. The findings of this study offer valuable insights for the design of waterproofing and drainage systems in three-hole subsea tunnels. subsea three-hole tunnel; main tunnel; service tunnel; inter-tunnel influences; grading of water inflow; analytical hierarchy process; fuzzy comprehensive evaluation +
Footnote †: journal: Medical  
of a grouting ring and validated the theoretical solution through comparison with numerical simulations and experimental techniques. Applying the principles of mass conservation and Darcy's law, [PERSON] et al. [12] investigated the steady-state seepage field of underwater double-hole parallel tunnels using the conformal transformation method [13; 14] and the Schwartz iteration method. However, [PERSON] et al. 's solution lacks closure and requires implementation through a computational program. [PERSON] et al. [15] conducted a study on the water inflow process in subsea tunnels using large-scale physical model experiments and numerical simulations, analyzing the water inflow mechanism as well as the variations in structural displacement and pore water pressure during the process. Their results can provide valuable references for tunnel structural design and disaster warning. [PERSON] [16] et al. attempted to correlate the geological and hydraulic parameters of rock mass experimentally and logically in order to estimate the amount of water flowing into tunnels. Their methodology was exemplified through an analysis of a tunnel in the Zagros region. [PERSON] [17] conducted an extensive investigation involving more than ten different types of tunnels in the Iranian region, identifying and summarizing seven key factors influencing tunnel water inflow. Building upon the geomechanical rock mass rating concept, [PERSON] proposed a site groundwater rating method that categorizes tunnel water inflow into seven grades based on the perceived level of danger. Stochastic mathematical methods, such as attribute mathematical models, the analytic hierarchy process [18], and fuzzy extension theory [19], have been applied in tunnel engineering for the effective analysis and evaluation of water inflow issues. Despite the inclusion of indicator analysis, weight evaluation, and other processes in the analysis, the accuracy and reliability of the evaluation results are widely recognized [20]. [PERSON] et al. [21] proposed an enhanced grayscale relationship analysis method (GRA) with an optimal combination weight approach for evaluating water inflow risks in subsea tunnels with complex geological conditions. Identifying eight key factors, the method was applied to assess and grade tunnel water inflow, as exemplified in the Qingdao Jiaozhou Bay undersea tunnel project. [PERSON] et al.