Pile Foundation System for Offshore Protection Structure

The hydrocarbon production facilities offshore eastern Canada must contend with icebergs. Subsea infrastructure is typically protected by placement in excavated drill centers (EDCs). EDCs are large excavations where subsea infrastructure is installed below the depth of potential iceberg penetration. However, EDCs are expensive for marginal field developments and therefore alternative concrete Subsea Ice Protection Structures (SIPS) are being evaluated. A concept 8 m high circular concrete SIPS of 45m and 25m outside and inside diameter, respectively, would be placed directly on the seabed. Global loads from contact with an iceberg are estimated to be less than 100 MN without ice management. Pipe piles are proposed to resist the lateral forces. Such large diameter pipe piles are commonly used on the Grand Banks to anchor mooring lines. Movement of the iceberg onto the SIPS may also generate greater vertical load onto the structure, increasing the sliding resistance. This paper presents an evaluation of the ultimate lateral load capacity of the piled foundation at large displacements. Centrifuge model tests were compared to numerical modelling results and to reduce the uncertainty with extrapolating the P-y method of pile analysis beyond its typical limits. The load sharing behavior between the piles and the SIPS foundation base was also evaluated.