Non-Linear Dynamic Response of Deepwater Suction Pile Foundation

Deepwater subsea petroleum developments present unique challenges for the geotechnical engineer. The combination of very soft soils and moderate to strong seismic ground motion requires innovative foundation solutions. This paper describes the seismic design of suction caisson foundations for subsea infrastructure in a deepwater field. Six-meter diameter, 12-m long suction piles were used to support underwater manifold assemblies. The seismic response of the structures was evaluated using a non-linear analysis in the time domain to predict foundation displacements under the design seismic event. The methodology used to define foundation response and assess structure displacements is presented. Results of the analysis showed that although there was local yielding of the foundation soils, the expected dynamic and permanent displacements were acceptable.