How do suction piles work

Suction piles have been used effectively as mooring anchors and foundations since the 1990s. They started to be used as anchoring points with the expansion of deep water projects. But how do suction piles work? How are they installed and embedded in the seafloor? We review: 

• Deployment
• Self-penetration
• Embedment 

 Suction piles (also called suction caissons or suction anchors) are a long steel cylinder topped with a pile top or cap. The cap comprises valves to assist with embedment as well as connections that differ depending on the use of the pile. 

Deployment 

Suction piles can be deployed as deep mooring anchors and foundations for subsea infrastructure. They are used as suction anchors on large deep water projects such as the Delta House Floating Production System in the Gulf of Mexico. Suction pile installation can be achieved from an offshore construction vessel or from an anchor handling vessel, with or without an A-frame. The suction pile is lowered to the seabed. Loads are resisted through the structure with mooring padeyes or pile top footings to the soil via direct bearing and skin friction. 

Self-penetration 

Large steel cylinder with an open bottom, the suction pile penetrates up to 60% of its length under its own weight, depending on soil conditions and the pile properties. 

Embedment 

The remainder of embedment is achieved through suction: a remote-operated vehicle (ROV) pumps water out of the top suction port after sealing pile top valves. Pile top and ROV instrumentation contribute to a precise installation.

The pile can also be retrieved by reversing the installation process, applying an overpressure inside the caisson.

For nearly three decades, suction piles have been effective foundations for pipeline initiations and terminations, as well as subsea manifolds and pump stations. Intermoor, Acteon’s Moorings and Anchors business line, provides complete lifecycle management: integrated geotechnical consultancy and structural pile design, fabrication, and suction pile installation. Geotechnical and structural engineering needs to be carefully applied to the design to prevent buckling. With more than 170 suction piles currently in service, Intermoor has cultivated a unique breadth of experience.