• Period | 2011 - 2013
  • Country | Norway
  • Market | Offshore energy
  • Project Manager | Vaughan Meyer
  • Client | The Norwegian Research Council
R&D program|

Offshore wind turbine foundations

Advancing the current state of knowledge in the areas of site characterisation, geotechnical design and monitoring of offshore wind turbine foundations.
With the greater emphasis placed on the development of renewable energy in recent years, NGI has experienced a significant increase in work for offshore wind farm projects.

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Background

NGI initiated a three-year (2011-2013) research programme with focus on geotechnical issues specific to the offshore wind energy sector. This research programme concentrated on advancing the current state of knowledge in the areas of site characterisation, geotechnical design and monitoring of offshore wind turbine foundations.

NGI involvement with offshore wind Projects
SP2 figure 1 crop

With the greater emphasis placed on the development of renewable energy in recent years, NGI has experienced a significant increase in work for offshore wind farm projects.

The nature of NGI’s offshore wind activities can be roughly equally split into areas of site characterisation, geotechnical design and monitoring.

Offshore wind farms and the turbine structures themselves present particular geotechnical challenges, which include:

  • site characterisation of large offshore areas (up to approximately 8 500 km2) and associated spatial variability in geotechnical conditions
  • the loading scenarios for geotechnical design of the foundations differ to those for other types of offshore structures
  • foundation stiffness is important since the turbines are sensitive to motions as well as their frequency
  • the level of industry experience with different foundation types varies
  • the long-term behaviour of the different foundations is largely unproven
  • there are uncertainties in the application of standard design approaches to some foundation types
  • the foundations are a significant part of the overall structure cost, raising the prominence of the foundation design in the project
  • given the large number of foundations to be installed, robust designs and efficient installation procedures are required
  • environmental and code verification requirements may influence the chosen foundation design

Outline of research

The focus of the research programme was to:

  • identify areas where geotechnical-related research and development would be of benefit for offshore wind turbine foundations
  • based on existing knowledge, improve existing methodologies and/or develop new techniques, focusing on the areas of site characterisation, geotechnical design and monitoring
  • where possible, adopt an integrated approach to the research in conjunction with industry. 

Research methodology

NGI’s approach to this research programme is based on over 40 years’ experience with foundations for offshore structures. In this respect, it is important to note that the change in focus from the design and construction of a foundation for a single, large offshore structure, such as an oil and gas platform, to the foundations for an offshore wind farm, is much like the shift from bespoke, or tailor-made engineering, towards mass production.

The research methodology has concentrated on filling gaps in the existing knowledge base identified from the particular geotechnical challenges highlighted for offshore wind turbine foundations.

Research areas with subtopics
 

SP2 figure 2

 
 
Comparison between an offshore platform and an offshore wind farm

Tailor made Mass production

 

 

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Project management

The research programme was coordinated by NGI under the supervision of Vaughan Meyer. Technical guidance was provided by Knut H. Andersen (Technical Expert, Offshore Energy), Lars Andresen (Managing Director), Hans Petter Jostad (Technical Expert, Numerical Modelling), Karl Henrik Mokkelbost (Director, Offshore Energy), Per Magnus Sparrevik (Technical Expert, Subsea Technology) and James Strout (Head of Technology Development and Innovation).

An international external advisory panel provided industry input into the research programme and guidance of the research aims during the course of the programme. The advisory panel’s contribution to the research programme is greatly appreciated.

The panel members were:

Morten Liingaard (DONG Energy) - Denmark

Pieter Mattelaer (GeoSea) - Belgium

Henrik Mikkelsen (MT Højgaard) - Denmark

Julian Osborne (East Anglia Offshore Wind / Vatenfall) – United Kingdom

Knut Ronold (DnV) - Norway

Marc Seidel (RePower) - Germany

Pål Johannes Strøm (Statoil) - Norway

Tor Inge Tjelta (Forewind / Statoil) – Norway

Offshore Wind turbine Foundations
Summary report, 19 November 2013
 

Publications in scientific journals

Norén-Cosgriff, K., Jostad, H.P., Madshus, C. (2015). Idealized load composition for determination of cyclic undrained degradation of soils. In V. Meyer (Ed.), Frontiers in Offshore Geotechnics III (Chapter 152, pp. 1097-1102). Boca Raton: CRC Press.
http://tow.ngi.no/article/title.aspx?tkey=90915
 
Page Risueño, A. M., Jostad, H. P. & Saue M. (2013). Application of an undrained and a partially drained cyclic accumulation model for monopole design. In Y.-J. Cui et al. (Ed.) Proceedings of the 5th International Young Geotechnical Engineers' Conference – 5th iYGEC 2013, Marne-la-Vallée, France, August 31–September 1, 2013 (pp.205-208). IOS Press.
http://tow.ngi.no/article/title.aspx?tkey=81876
 
Sauvin, G., Bazin, S., Vanneste, M., Lecomte, I. & Pfaffhuber, A.A. (2011). Towards joint inversion/interpretation for landslide-prone areas in Norway - Integrating Geophysics and Geotechnique. In Proceedings of the Near Surface Geoscience 2011 – 17th European Meeting of Environmental and Engineering Geophysics, Leicester, United Kingdom 12 – 14 September 2011 (pp. 531-535). Houten: EAGE.
http://tow.ngi.no/article/title.aspx?tkey=81980
 
Socco, V.L., Maraschini, M., Boiero, D., Vanneste, M., Madshus, C., Westerdahl, H., Duffaut, K. & Skomedal, E. (2011) On the use of NGI’s prototype seabed-coupled shear wave vibrator for shallow soil characterization - Part II: Joint inversion of multi-modal Love and Scholte Surface Waves. Geophysical Journal International, 185(1), 237-252. doi:10.1111/j.1365-246X.2011.04961.x
http://tow.ngi.no/article/title.aspx?tkey=68881
 
Sturm, H. (2011). Geotechnical performance of a novel gravity base type shallow foundation for offshore wind turbines. Geotechnik, 34(2), 85-96. doi:10.1002/gete.201100013.
http://tow.ngi.no/article/title.aspx?tkey=68887
 
Sturm, H., Andersen, K.H., Langford, T. & Saue, M. (2012). An introduction to the NGI cyclic accumulation approach in the foundation design of OWTs. In Proceedings of the 12th Baltic Sea Geotechnical Conference, Infrastructure in the Baltic Sea Region, Rostock, Germany 31 May - 2 June 2012. Eigenverlag DGGT Essen.
http://tow.ngi.no/article/title.aspx?tkey=74914

Vanneste, M., Longva, O., L’Heureux, J.-S., Vardy, M.E., Morgan, E., Forsberg, C.F., Kvalstad, T.J., Strout, J.M., Brendryen, J., Haflidason, H., Lecomte, I., Steiner, A., Kopf, A., Mörz, T. & Kreiter, S. (2013) Finneidfjord, a Field Laboratory for Integrated Submarine Slope Stability Assessement and Characterization of Landslide-prone Sediments: a Review.
In Proceedings of Offshore Technology Conference 2013 (OTC 2013). Houston, Texas, USA, 6 - 9 May 2013. (OTC 23967). New York: Curran. 
http://tow.ngi.no/article/title.aspx?tkey=74928

Vanneste, M., Madshus, C., Socco, L.V., Maraschini, M., Sparrevik, P.M., Westerdahl, H., Duffaut, K., Skomedal, E. & Bjørnarå, T.I. (2011). On the use of NGI’s prototype seabed-coupled shear wave vibrator for shallow soil characterization - Part I: Acquisition and processing of surface Waves. Geophysical Journal International, 185(1), 221-236. doi:10.1111/j.1365-246X.2011.04960.x 
http://tow.ngi.no/article/title.aspx?tkey=68894

 

NGI reports
NGI Report No. 20110087-01-R
Estimation of hysteretic soil damping from laboratory measurements including strain accumulation
12 May 2014
Contact NGI for access: doksenter@ngi.no
 
NGI Report No. 20110186-00-1-R
Soil Structure Interaction for OWT Monopile Foundation
7 December 2011
 
NGI Report No. 20110255-00-1-R
A new procedure for analysis of load
19 December 2011       
             
NGI Report No. 20120132-01-R
Instrumentation and monitoring strategy for wind energy foundations
18 January 2013
           

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