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Dynamic and Static measurements at 40 m waterdepth

Overview testlocation

Overview testlocation

 

To optimize and certify the final design of the Wikinger Offshore Wind Farm (OWF) in the Baltic Sea near the German island of Ruegen, the project owner, Iberdrola Renewables, initiated a test program, whereby test piles were installed at the planned location of 3 wind turbines in 40 meter deep water.

 

During the first phase the test piles were driven into the sea floor as Pile Driving Analysis (PDA) measurements were taken using underwater sensors. In addition signal matching was applied on the measurements during the final hammer blow to predict the mobilized static bearing capacity of each pile.

 

After a set-up period of approx. 13 weeks the second phase took place, during which at each location one test pile was subjected to a static tensile load test (up to 15 MN) while the other pile was subjected to a high strain dynamic test. For the latter signal matching was applied on the first restrike to predict the mobilized static bearing capacity (incl. the set-up).

 
Among the many project challenges two must be mentioned:

First of all there was the design and construction of an assembly to perform static load tests under water. In a joint effort between the construction contractor Bilfinger Marine & Offshore, engineering firm Fichtner Wind & Water, the Norwegian Geotechnical Institute NGI and Allnamics a practical, innovative and re-useable assembly was developed that can be installed from the vessel deck without diver intervention.

 

Secondly the underwater sensors had to remain functional for at least 3 month in salt water at a water depth of 40 meters (so they could be used during the second phase). The sensors supplied by Allnamics all met this challenge. Apart from supplying the sensors Allnamics was also contracted by Bilfinger to perform and evaluate the static and dynamic load tests of the test piles. These tests were performed using the PDR, a state-of-the-art multi-purpose monitoring system that can also be used for Rapid Load Testing.

 

For more details about this project click here to see a movie made by SAL Offshore, and in case you would like more information on the PDR or underwater testing, please feel free to contact us or download the PDR brochure.

Underwater Sensors (UW)

Under water Sensors (UW)

 

Pile Driving Frame

Pile Driving Frame

4 Paal tijdens het hijsen dichtbij

Pile with sensors during lifting

5 Paal tijdens het hijsen

Pile during lifting

6 Aansluiten sensoren op de PDR

Connected double sensor set on both PDRs

7 Menck Hamer

Menck Hamer

8 Meten tijdens het heien

PDA Measuring during driving

10 Ophalen kabels na 10 weken op de zeebodem

Retrieving cables after 10 weeks at a water depth of 40 meters

 

11 Aansluiten kabels aan de meetapparatuur

Connecting the cables on the PDR monitoring unit

12 Statische proefbelasting

Measuring during SLT

13 Eenvoudige voorstelling van meetsetup

Simple explanation of the measurement setup

14 Meetframe SLT

Static Load Testing Frame

15 Reactieframe in Water

Reaction frame

16 Onderwater robot

ROV

17 Onderwater sensoren

The UW sensors

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