Driving of Foundation Piles for Offshore Wind Turbines

While it is common practice to monitor pile installation for offshore platforms in the hydrocarbon industry, the installation of foundation structures for offshore wind turbines is a new challenge. Wind Turbines to be installed in the German sector of the North Sea are mostly built on pile foundations. Both monopile as well as multiple pile - mainly three pile (tripile) - solutions are designed. As these piles have to resist high lateral loading, they must be embedded in strong competent soil layers. Open-end steel piles of large diameters are generally used and installed by impact driving. In general, hard driving conditions exist. It will be shown that the monitoring of the driving process by the Pile Driving Analyzer is not only important for the assessment of hammer performance and stresses in the pile or axial soil resistance, but also for lateral resistance. The assessment of the cyclic stability of the foundation requires an accurate prediction of the static capacity, which can be realised by dynamic pile tests. A proposal is given for the derivation of approximate p-y-curves for lateral loading directly from the solutions of CAPWAP model parameters.