Suction Bucket or Caisson Foundations
Article published on Thursday, 07 January 2016
Suction caissons are best described as upturned buckets that
are lowered into marine sediment, to anchor structures. This is done by
pumping water out of ‘bucket’ to lower the pressure inside bucket skirt,
this negative pressure and weight of foundation causes the foundation to
sink into sea floor. This process is easily reversed for removal of foundation.
This type of foundation has been used in the oil and gas
industry since the early 80’s to anchor floating structures to seafloor.
Some installations taking place at depths of over 1500m
- Low noise during installation
- Reduced weight
- Increased installation speeds
- Ease of decommissioning
- Little to no seabed preparation needed
- Suitable for deep waters and large turbines
variants are currently being developed for the offshore wind sector, Mono
Bucket by Universal Foundation and Suction Jacket Foundation by DONG energy
Mono Bucket (Universal Foundation)
Source: Universal Foundation
The all-in-one Mono Bucket structure consists of a large
monopile type structure that is welded to the top of a single giant suction
The Universal Foundation concept was one of four foundation designs selected
in The Carbon Trust’s Offshore Wind Accelerator programme.
The Mono Bucket foundation is installed using a jet and suction system
as the driving force. Lowering the pressure in the cavity between the foundation
and the seabed generates water flow, which lowers resistance around the
edge of the foundation’s skirt. This reduces resistance and allows seabed
A patented jetting system controlling vertical alignment ensures the foundation
is installed within prescribed tolerances, removing the need for a transition
piece to adjust verticality.
Source: Universal Foundation
- Can be installed in a wide variety of site conditions,
including sand, silt, clay and layered strata.
- A patented jetting system controlling vertical alignment
ensures the foundation is installed within prescribed vertical tolerances,
removing the need for a grouted transition piece to adjust verticality.
- Installation does not (in most cases) require seabed preparation.
- Installation is noise free and offers no risk to marine
- The foundation can be easily removed by reversing the
process used during installation.
- Single-lift or self-floating installation
- Designed for water depths of up to 55m
2002 August - Frederikshavn, Denmark
Prototype of suction bucket installed onshore to support
a Vestas V90 3MW turbine. This project was delivered by MBD Offshore Power
(Universal Foundation) and ELSAM (DONG Energy) in cooperation with the
March - Horns Rev 2 Meteorological Mast, Denmark
- Bucket diameter 12m
- Height of bucket 6m
- Total weight 135 tonnes
Universal Foundation in cooperation with DONG energy installed
a mobile meteorological mast with a suction bucket foundation at Horns
Rev 2 site. The foundation was fabricated by Bladt Industries in Aalborg
in 2008. Foundation was floated out to location, prior to installation.
Met mast decommissioned and completely removed from site on 7th July 2015,
as mast was no longer required by DONG energy. Removal method was to reverse
the installation method, by increasing pressure within the bucket structure
2013 September - Dogger Bank 2 x Meteorological Mast,
In October 2011, Universal Foundation was awarded the contract
for the turnkey installation of two meteorological masts at Forewind’s
Dogger Bank offshore wind farm.
Both of the Mono Buckets were installed successfully within the prescribed
tolerances and achieved cost, time saving and noise reduction targets.
2014 September North Sea Trial Installation, UK
As part of The Carbon Trust’s Offshore Wind Accelerator
(OWA) programme trial installations took place at three UK offshore wind
sites - Dogger Bank, Dudgeon and Hornsea. 29 installations were carried
out in 24 days.
The trial was to assess foundation penetration, verticality, water injection
impact on soil plug, forces and stress in skirt structure and internal
soil levelling capability.
It is understood that the Mono Bucket coped very well with multiple installation-retrievals
and the differing sediments, as soil characteristics within the three sites
varied from soft clay, moraine clay, boulder bank clay – with sand spikes
and layers, clay crust, sand and silt.
Two suction bucket foundations were used in trial, one measuring 8m in
diameter with a 6m skirt and a reference structure of 4m diameter with
Suction Bucket Jacket (DONG energy)
The suction bucket jacket design consists of three legs
welded together in a lattice jacket structure that stand atop of three
giant suction bucket foundations.
Structure is lightweight and requires a single operation when installed
The Suction Bucket Jacket was designed by DONG Energy and based on ideas
from the SPT Offshore foundation, a finalist in a global competition run
by the Carbon Trust to find lower cost foundation solutions.
Source: Dong Energy
- Significant reduction of the foundation cost, due to minimal
- Environmentally friendly installation process.
- Transport and installation in one procedure.
- Suitable for water depths of 30-60m
1. The suction bucket jacket
is lowered to the seabed
2. An under pressure is
applied to the buckets by individual suction pumps
3. The hydrostatic pressure
difference and the weight of structure causes the buckets to penetrate
4. The suction pumps are
recovered to the installation vessel
5. A thin layer of concrete
is injected between seabed and bucket lid
2014 October Borkum Riffgrund 1 Germany
Full scale test with Siemens SWT-4.0-130 turbine at Borkum
Riffgrund 1 offshore wind project in Germany, site was selected due to
its dense sand seabed, which created a challenging installation situation.
Installation was carried out in water depth of 25m.
DONG energy and The Carbon Trust have collaborated on this
full scale demonstrator, and received 6m GBP in funding from The Carbon
Trust through the Offshore Wind Accelerator programme (OWA)
Borkum Suction Bucket Jacket Specifications
- Transition Piece: 130 t
- Jacket: 372 t
- Buckets: 250 t
- Installed weight: 752 t
- Footprint: 23 x 23 m
- Top: 16 x 16 m
- Buckets: 8 x 8 m
- Total height: 56.6 m