Influence of water pressure on deep subsea tunnel buried within sandy seabed

Abstract

For a subsea tunnel, the changeable high water pressure is of great significance in the soil-water-tunnel interaction. In this study, a series of parametric studies were conducted to investigate the effect of high water pressures on the seabed settlement and the earth pressures as well as the axial forces and bending moment of a tunnel lining during excavation. The simulation results disclose that the seabed settlement along the transversal tunnel direction increased linearly with the rising water level and the ranges of settlement troughs can be up to around 5 D (D, tunnel diameter) in width. Similarly, the settlement along the longitudinal tunnel direction featuring a semi-trough shape also shows a linear increase with the rising water level, and the maximum influence zone could reach a length of 3 D in front of the excavation face. With the increase of water pressure during tunneling, the total earth pressures along the perimeter of a circular tunnel lining increased significantly and their distributions were prone to be more uniform around the tunnel perimeter. As a result, the deep sea tunnel lining has a typical feature of large axial force and relatively smaller bending moment.