Geotechnical investigation and tension-pile solution for foundation of SFT prototype at Qiandao Lake

Mooring foundation system is one of the key components for Submerged Floating Tunnel (SFT). In-situ geotechnical investigations have been performed at Qiandao Lake, China and the geological characteristics of the lake-bed sediments are obtained. In accordance to the geotechnical analyses and the review on various types of foundations in the offshore engineering, the rock-embedded tension-pile may be employed as the potential foundation solution for providing the required uplift resistance to the buoyancy of SFT, especially for the steep sloping terrain at the sea/lake bed. The uplift bearing capacity of the tension pile embedded in the layered sediments is further investigated numerically, with an axisymmetric finite element model for the vertical-loading condition, and with a symmetric 3-D finite element model for the oblique-loading one. Numerical results indicate that, the sediment characteristics have much effect on the shear stress along the pile-sediment interface, and the loading angle also has much influence on the ultimate tension loads.