Vibratory piling may be an alternative

Thursday, 26 November, 2015 - 11:00
Static load testing took place on a test area near Cuxhaven. (Photo: RWE Innogy)
Static load testing took place on a test area near Cuxhaven. (Photo: RWE Innogy)

On a test site the vibratory pile installation method has shown significantly reduced peak noise emissions as well as installation time compared to a hammered installation and can be controlled to produce a similar bearing capacity to impact hammered piles.

New methods of constructing wind farms at sea are playing a major role in reducing costs and shortening building times. That is why a group of developers and operators of offshore wind farms – RWE Innogy, Bilfinger, Dong Energy, EnBW, E.ON and Vattenfall – joined forces last year and launched a pilot project to test the pile behaviour as a consequence of an alternative installation method for offshore foundations. The project was part of the Carbon Trust Offshore Wind Accelerator, a world-leading research and development programme for reducing the costs of offshore wind energy.

Now first results are on the table: the tests on land are highlighting the vibratory method generates lower peak noise emissions and is up to ten times faster. Continuously present noise emissions will need to be determined on a project specific basis. The lateral bearing capacity of large diameter piles has been measured allowing an initial methodology for the prediction of vibrated pile bearing capacity to be developed.

In summer 2014, three steel piles were vibrated and another three piles were hammered conventionally into saturated, sandy soil on a test area near Cuxhaven. The 4.3 m diameter monopiles were the very first produced from the new Steelwind Nordenham fabrication facility, the hammer was supplied by IHC Hydrohammer and the vibrator was supplied by PVE Dieseko. Technical University Braunschweig ran the data capture, such as installation times and noise emissions, in collaboration with various other institutions and technical experts alongside certification and regulatory authorities.

The piles were then left in the ground for a period of four months before they underwent static load testing, which examined how the piles behave when subjected to the kind of lateral load that is typical in offshore conditions. RWE Innogy was the project lead and contracted Bilfinger Marine & Offshore Systems, who also sponsored parts of the project, to execute the major test works.

Jan Matthiesen, Director of Innovation at the Carbon Trust, commenting on the positive results: “The project results not only demonstrate that vibro techniques could be a viable method for piling, but are also evidence of what can be achieved through industry collaboration.” RWE Innogy now plans to build on these tests and launch an additional subproject intended to investigate ways of optimising the installation methodology itself.

Katharina Garus / RWE

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