Gravity foundations

Photo: Petri & Betz
Under the appropriate conditions, gravity-based foundations offer an attractive solution to offshore wind farms

Local manufacturing, inexpensive materials and proven design may be the right combination for foundations at water depths of up to 60 metres.

COWI's design for gravity-based foundations has been adopted in several completed offshore wind farms.

Right conditions

Given the right conditions in terms of water depth, soil conditions, number of foundations and capability of contractor to optimise a series production, gravity-based foundations offer an attractive option for many offshore wind farms.

Inexpensive solution
Under the right circumstances, the gravity-based foundation proves to be an inexpensive solution, and the aspect of local job creation may, in some cases, add to the advantage of the gravity-based foundation.

In COWI, we use our in-house highly specialised FEM model as the basis for the design of gravity-based foundations. All our projects have been certified including our specialised tools applied for the design. 

We work in close cooperation with the contractors and possess the essential knowledge related to design-constructability issues which are key to any well-performed project.

Manufacturing

Gravity-based foundations are constructed on land and transported by barge or crane to the offshore position. The structure is placed on a gravel bed to accommodate for unevenness in the existing seabed, and potentially to substitute inadequate soil with low strength.

The structures are then typically ballasted with stones or sand to attain the necessary stability. Scour protection is placed around the toe of the structure and to cover the cables leading to and from the foundation.

LAST UPDATED: 07.02.2017