Prediction and control measures of water inflow for subsea tunnels

Predicting water inflow and optimizing waterproofing-drainage systems are critical for subsea tunnel safety. This study addresses the limitations of static parameter-based models by proposing a dynamic analytical formula for water inflow prediction, integrating tunnel depth, hydraulic head, and lining permeability using complex variable functions and Darcy's law. Additionally, three-dimensional numerical simulations were conducted to evaluate the stability and pore water pressure distribution of the tunnel in land section, sea section, and land-sea transition section with fully encapsulated or half-encapsulated waterproofing-drainage schemes. Key findings include: the half-encapsulated system reduced lining deformation by 15-20% in the land section, offering a cost-effective solution; pore water pressure in the sea section remained below 0.5 MPa (excluding class IV/V zones), recommending a fully encapsulated system with pressure-relief valves; and elevated pore water pressure (up to 0.42 MPa) at the land-sea interface necessitated adaptive drainage measures. While the analytical formula and numerical simulations address distinct aspects of tunnel design (water inflow prediction and structural stability), their combined insights provide a holistic framework for optimizing subsea tunnel systems under dynamic hydraulic conditions.