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Conference programme 

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Poster session

Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Jens Brink Clausen Geo, Denmark
Co-authors:
Jens Brink Clausen (1) F P
(1) Geo, Kgs. Lyngby, Denmark

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Poster
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Presenter's biography

Biographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited

Jens Brink Clausen is Department Director of Geo’s geotechnical Offshore Investigations Department. Jens has a B.Sc. from The Technical University of Denmark and a M.E. in geotechnical engineering from University of Florida (1992). During the last 20 years, Jens has accumulated a vast expertise within planning, optimisation and completion of larger, complex offshore investigations. The last decade has focused on offshore wind projects, where he has been involved in more than 30 projects across Europe. Due to his vast experience, Jens is regularly interviewed in business media and TV. Jens is also a board member of the Danish Geotechnical Society.

Abstract

Optimising the geotechnical investigation

Introduction

The geotechnical site investigation for offshore wind farms is a key input for the foundation selection and design, as well as cost optimisation of the whole wind farm. The effort to improve the output, from the site investigation work, is an ongoing process. The aim for the optimisation can have different focus areas. For Geo the first area of focus has been to improve even further the HSE performance.

Approach

The challenge from the technical point of view is how best to combine the HSE focus with the aim of still being able to deliver the best possible site investigation solution in a cost effective way.

In relation to offshore wind farm locations, one of the major technical challenges have been how to improve the sample quality in inhomogeneous soil and soft rock formations – such as boulder clay, chalk and other often complex formations.

Main body of abstract

To evolve the approach and methods to carry out geotechnical drilling work for offshore wind farms, Geo has developed a new concept for floating (heave compensated) drilling. One ambition for this new concept was how to transform 50 years of knowledge from high quality onshore geotechnical drilling work, to be used in the offshore environment, while still performing and providing high sample quality.
The key element in the technical design of the system was the principal belief that to perform geotechnical drilling, the basic drill rig should be a “geotechnical rig” operated with heave compensation. Further, the setup should be designed able to handle the range of different tools, including Down-The-Hole tools, required for drilling, sampling and testing in a variety of soil/rock conditions.


Conclusion

The paper presents the background and realisation of the drilling concept and discusses the results obtained. The discussion includes comparison with the predominate present drilling and sampling technique used in challenging seabed formations, such as hard soil and chalk. The link between geotechnical investigations and project cost will also be addressed, and key factors for potential cost saving will be highlighted.


Learning objectives
The learning objectives of the abstract are to provide the delegates with a knowledge of a new technical approach and views on the link between planning the geotechnical investigation and project cost savings.