Analytical Solution for Water Inflow into Deeply Buried Symmetrical Subsea Tunnels with Excavation Damage Zones

Abstract

The water inflow into tunnels will vary with the development of excavation damage zones (EDZs). Currently, there are few analytical studies on the evaluation of the water inflow into deeply buried symmetrical subsea tunnels, considering the influence of EDZs. Therefore, a solution was analytically developed using seepage mechanics, conformal mappings, and the superposition principle. The proposed solution was verified with a simplified solution and a numerical solution. A range of parametric analyses were performed to determine the effects of EDZs and spatial parameters on the water inflow, and an application to an engineering case was carried out. The results in this study reveal that the relative error between the proposed solution and the numerical solution is always less than 2.5% when the ratio of the buried depth to the radius of the tunnel is greater than or equal to 4. The water inflow increases significantly at an early stage of increasing the EDZ permeability coefficient, then gradually stabilizes and increases approximately linearly with the EDZ thickness. The effects of EDZs are greater with smaller buried depths and greater distances between the two tunnel centres. Compared with a single subsea tunnel, there is a diverting effect between the symmetrical subsea tunnels, which can be promoted by increasing the EDZ parameters. Moreover, this diverting effect increases as the buried depth increases and the distance between the two tunnel centres decreases. The application in this study shows that an increase of 13.82% to 30.42% in the water inflow occurred after considering the EDZs’ effects. The proposed solution can provide an efficient method to evaluate the water inflow into the deeply buried symmetrical subsea tunnels with EDZs.