Numerical Simulation Study on the Influencing Factors of Water Inflow in Subsea Tunnels

The construction of undersea tunnels involves multiple potential hazards, among which water-related risks are particularly critical during the construction phase. Tunnel water inrush can trigger serious safety incidents and increase maintenance costs during operation. Therefore, accurately predicting water inflow is essential to ensure construction safety and long-term operational reliability. This study calculated the water inflow per meter of an undersea tunnel using the built-in FISH programming language in FLAC3D 7.0 finite difference software. A series of numerical models was established to examine the effects of eight influencing factors, including seawater depth, permeability of the surrounding rock, overburden thickness, and the thickness and permeability coefficients of both the grouting ring and the lining. The results indicate that water inflow generally increases linearly with greater seawater depth and overburden thickness. Although higher permeability of the surrounding rock leads to increased inflow, the growth rate gradually decreases. When the thickness of the grouting ring exceeds 6 m, the marginal benefit of its effect gradually decreases. The inflow was found to decrease as the lining permeability declined, with a more evident reduction under higher grouting ring permeability. Sensitivity analysis further revealed that seawater depth exerts the most significant influence on water inflow, whereas the thickness of the grouting ring has the least effect.