Testing methodology
The six mono-piles were driven in a grid. Each of the three impact hammer driven piles was driven opposite to one of the three vibrator driven piles. Six months after driving the lateral load of each pile was tested by pulling the piles towards each other with hydraulic jacks. The hydraulic jacking system had a maximum pulling force capacity of 2000 mT. A total of 50 sensors were installed in the piles to monitor the movement of the pile as the jacking force was increased by 400 mT increments. In this independent test no difference in lateral load capacity between impact or vibrator driven piles was detected. The conclusion of the test is that monopiles driven by Dieseko’s vibratory hammer to full depth are equivalent to those driven by impact hammer. With the presentation of these results the last remaining concerns of using vibratory piling technology for the installation of monopiles have been lifted.
 
Some quotes from the participating companies:
“The benefit is faster and more environmentally benign monopile installation in offshore wind farm projects.”  RWE Innogy.
 
“The pilot project’s objective was to demonstrate that the lateral load capacity of vibrated and hammered piles in sand is to be regarded as equivalent. Furthermore it aims to indicate that full depth vibro-driving of monopiles in comparison to hammered piles has lower noise levels causes lower fatigue symptoms and stress to the monopiles and is faster and more cost effective. Last but not least this technique shall simplify the installation for large monopiles due to fewer tools involved in the construction process of offshore wind turbines.” Carbon Trust Offshore Wind Accelerator (OWA).

The investigations are focusing on a comparison on the horizontal load bearing capacity of impact and vibration sunk piles. Horizontal loads occur in particular with the monopile type of foundation. The vibration piling method could well lead to considerable improvements with regard to noise emissions cause fewer signs of pile fatigue in the piles and reduce the amount of work required in terms of equipment needed for the installation process.” Bilfinger.
 
“Dieseko’s 40 year expertise in vibratory piling equipment has now irrefutably demonstrated that the 500M-2000M vibrator series paired with the 3200 Power Pack offer the necessary driving power for the more demanding applications such as driving the world’s largest monopiles. We look forward to implement vibrating technology for the installation of monopiles at the participating test partners’ upcoming foundation projects.”  Dieseko.