Dynamic and cyclic pile-soil response curves for monopile design

Monopiles remain the most commonly used foundation for offshore wind turbines. Their design is governed by the lateral pile-soil response under operational and environmental loads that the turbine tower will be sub-jected to in its lifetime. In practice, semi-empirical p-y curve methods recommended in offshore standards and calibrated from field tests of piles with diameters less than one metre are still applied. Several publica¬tions have questioned this approach for large-diameter piles as these can be conservative or unconservative depending on the load case, pile diameter and soil conditions. In this paper, a methodology to derive p-y curves that capture the full non-linear pile-soil response from very small elastic to large cyclic pile displace-ments is discussed. The method was first developed for carbonate soils and has been applied in several de-tailed design projects (Erbrich, et. al. 2010, 2017). It directly considers cyclic laboratory test data and the site-specific cyclic load history. This allows a more accurate prediction of the pile-soil response for different load cases and limit states. The application of this method in conventional silica sands and clays is presented along with an example of an offshore wind turbine design demonstrating potential cost savings that can be achieved.

Proceedings of the 8th International Conference, 12-14 September 2017, Royal Geographical Society, London, UK