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Constructing a turbine foundation In the Horns Rev project, Elsam used the so-called "mono-pile" concept, single piles that are driven into the seabed. Pile driving is a fast process, and piles are relatively inexpensive to produce. Geotechnical surveys show that the seabed was made up of sand, and this makes mono-pile foundations particularly attractive. Mono-pile foundations have also been used for offshore turbines in the Netherlands and Sweden. Similarly, the project�s meteorological tower rests on a mono-pile foundation. The foundation is designed as a cylindrical steel pipe with a diameter of approx. 4 m and a material thickness of 5 cm. A large, hydraulic ram drives the steel pipes into the seabed to a depth of some 25 meters. A "mattress" of gravel is placed around the foundation to protect against erosion.
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| The construction phases | ||
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A "gravel mattress" were arranged to minimise erosion. - Thickness: 0.5 m.
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| The mono-pile (4-m diameter and
5-cm material thickness) were driven through the mattress to the planned
depth (approx. 25 meters).
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| The transition piece (complete
with pre-installed features such as boat landing arrangement, cathodic
protection, cable ducts for sub-marine cables, turbine tower flange, etc.)
were cast together with the mono-pile.
The transition piece made it possible to raise the towers to a completely vertical position even if the foundation were not completely level.
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| The cable ducts for the
sub-marine cables were closed. The concrete is left to cure.
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| The protective gravel mattress
was finished with an additional layer of gravel and stones.
- Thickness: 0.8 m.
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| Erection of the wind turbine and installation of 36-kV cables to substation. |  |
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Pile driving Specially designed barges with a heavy-duty ram were used to drive the mono-pile into the seabed.
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