Monopiles are the most commonly used foundations for offshore wind turbines and it is expected that these remain the preferred option in the foreseeable future. Monopiles have a simple design, are relatively easy to install, are suitable for the shallow North Sea, and are robust. The dominant method used to drive monopiles into the seabed is the so-called hydraulic impact piling (hammering). The main disadvantages of this technique are the noise levels emitted during pile driving, and the high impact loads on the monopiles induced by the hammer hits. Without changes to the current applied pile installation method the expenses on noise reduction measures will increase and a firmer and heavier design of the monopile may be required to allow for the induced impact loads.
This project Gentle Driving of Piles (GDP) aims to make the pile installation process more efficient. In this project the consortium aims to develop and test a novel pile installation method based on simultaneous application of low-frequency and high-frequency vibrators exciting two different modes of motion on the monopiles. This method is called “gentle” for its envisaged capability to reduce the driving loads and the emitted installation noise which is harmful for the environment, e.g. to mammals and fish.
Next to the novel pile driving technique, the consortium aims to develop new models that explain the physics governing the novel pile installation technique, optimise the procedure and show that noise generated with GPD is considerably reduced compared to conventional installation methods. We will validate these models with experimental data collected from the dedicated measurement campaign of this project and data of previous project that are provided by the consortium partners.
We strive to develop this technique without compromising the pile penetration speed and the soil bearing capacity, which is essential for a stable offshore wind turbine operation.
In this project a solid “proof of concept” of the proposed installation method will be delivered. We will experimentally test the novel pile installation technique based on simultaneous application of vibrators acting in several directions. Furthermore we will analyse the data of the experiments and use the data for validation of several numerical models. In this way the project will show that the pile penetration speed and the soil bearing capacity stay uncompromised. In addition, we will produce models that are able to predict the effects of this new GDP technique including noise emission and soil stability.
This project is supported by the Netherlands Enterprise Agency and TKI Wind op Zee.
Gentle Driving of piles (presentation at GROW side-event 2019)
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