Complex variable analysis for stress distribution of an underwater tunnel in an elastic half plane

When an underwater tunnel is excavated, the groundwater may flow into the tunnel. The seepage forces consequently induced can have important effects on the effective stresses around the tunnel. Moreover, the influences of the free surface of a shallow underwater tunnel should also be considered. In this research, an analytical solution is presented to calculate the seepage-induced effective stresses around a shallow underwater tunnel in an elastic half plane. The solution uses the complex variable method and consists of conformally mapping the half plane with a hole onto a transformed circular ring. The coefficients of the various terms in the Laurent series expansions of the stress functions in the transformed region can be obtained from the boundary conditions. The total stress distribution around a shallow underwater tunnel can be calculated by the potentials in the half plane. The effective stress can be obtained by subtracting the pore pressure from the total stress. The analytical solution is validated by numerical simulations and can be used to perform both the short-term and long-term analyses. By using the proposed solution, it is found that the circumferential effective stresses around the tunnel increase greatly because of seepage, and they increase with the increase of water depth in both the undrained and drained conditions. Copyright (C) 2015 John Wiley & Sons, Ltd.