Interview with Tobias Griesshaber, Project Manager, RWE Innogy GmbH

Mr Griesshaber, you’re currently testing the vibration technology for offshore pile foundations at the Cuxhaven-Altenwalde site as part of a four-month pilot project called VIBRO in conjunction with other business partners. Are the piles that are inserted by means of vibration as stable as those that are rammed into the ground in the traditional way?

That’s exactly what we want to explore in this pilot project. We’ve inserted three test foundations in the subsurface using the vibration technique during the last few weeks and installed three other foundations with the traditional impact ramming process. We’ll compare the two techniques in August and examine whether both processes provide the same degree of stability: that is to say, whether the soil characteristics provide in both cases a secure anchor in the seabed for the wind turbines against the forces of wind and waves over an operating period of 25 years. We’ll probably be able to say something about the results by the end of the year.

What benefits are there in using the new ramming process for the offshore wind power sector?

We hope to make savings by using the vibration technology when building offshore wind parks and send an important signal to the sector. Inserting piles by means of vibration is faster than impact ramming. The technology is also much quieter and this will particularly benefit protected marine mammals like porpoises. If the process proves to be just as efficient as impact ramming, future offshore projects could benefit from this when steel piles need to be installed.

Why was the Cuxhaven-Altenwalde site selected for the tests?

The sandy base in Cuxhaven-Altenwalde is absolutely ideal for the project, because the soil conditions here are very similar to those encountered in the North Sea. For example, the dense layers of the sand and the groundwater level, which is about two metres below the site’s surface, are very similar to the conditions that we find out at sea. As a result, we can transfer the results from here to most of the offshore wind parks that are being planned for the North Sea and this makes the tests all the more meaningful.

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