A new load transfer model for axially loaded piles driven in chalk

Chalk poses geotechnical challenges for offshore foundation designers, because it can present as either a weak rock or a highly sensitive and putty paste, depending on the loading applied and the chalk’s varia-ble natural structure. Piles supporting jacket structures mainly work through an axial push-pull action, while floating Tension Leg Platforms (TLPs) exert mainly axial tension. Their safe and economical de-sign in chalk for dynamically sensitive offshore wind turbines is challenged by uncertainties regarding their axial load-displacement behaviour. This paper first introduces a recently developed load transfer model for axially loaded piles driven in chalk, which is expressed as a function of geotechnical proper-ties measured directly by laboratory and in-situ tests, accounting indirectly for installation effects. The main aim of the paper is to assess the performance of the new model based on field pile tests at a well-characterized chalk site, in terms of axial displacements at the pile head, the distribution of axial force over the pile shaft and the profile of local shaft displacement at failure. Good agreement between the computed and measured pile head response demonstrates the applicability of the new proposed model and shows its advantages in comparison with existing industrial design approaches.