Offshore foundation installation; on the road to losing its semi-empirical nature?-PPT Presentation

PPT Presentation

Pdf Summary

The presentation examines the challenges of installing offshore wind foundations in complex ground conditions, particularly overconsolidated, extremely strong clays and weak mudstones. Installation methods include self-weight penetration, vibro-driving, suction and impact driving; reliable predictions of soil resistance to driving (SRD) are essential for planning pile installation.<br /><br />Case studies of glacial till and Cretaceous clay show that similar cone penetration test (CPT) and laboratory results can nevertheless correspond to different impact-driving behaviour. CPT data alone do not explain these differences, suggesting that geological factors such as material origin or mineralogy may also matter.<br /><br />Mercia Mudstone illustrates the difficulty of characterizing materials that lie between soil and rock. Its strength and behaviour vary with lithology and weathering; weaker material may occur beneath stronger layers. Sampling and testing are challenging, and classification tests can be misleading. CPTs may indicate high resistance even when laboratory tests show low strength, complicating the selection of SRD parameters and prediction methods.<br /><br />Comparisons of measured pile-driving performance with predictions from several SRD methods highlight that no single approach reliably covers all ground conditions. Better outcomes require high-quality site investigations combining CPTs with suitable sampling and adapted laboratory testing, alongside a sound understanding of local geology. SRD methods should be supported by broad datasets spanning different regions and foundation dimensions. DEME Offshore is developing its installation database toward probabilistic approaches that can capture the range of material behaviours.

Keywords

offshore wind foundations

soil resistance to driving

cone penetration test

impact driving

glacial till

Cretaceous clay

Mercia Mudstone

site investigation

laboratory testing

probabilistic approaches