Physical modelling to demonstrate the feasibility of screw piles for offshore jacket supported wind energy structures

Craig Davidson, Michael Brown, Benjamin Cerfontaine, Jonathan Knappett, Andrew Brennan, Therar Al-Baghdadi, Charles Augarde, William M. Coombs, Lei Wang, Anthony Blake, David Richards, Jonathan David Ball

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Abstract

Screw piles potentially offer quieter installation and enhanced axial tensile capacity over straight shafted driven piles. As such, they have been suggested as a possible foundation solution for offshore jacket supported wind turbines in deeper water. To investigate the feasibility of their use in this setting, centrifuge testing of six model screw piles of different designs was conducted to measure the installation requirements and ultimate axial capacity of the piles in very-dense and medium-dense sand. The screw piles were designed to sustain loads generated by an extreme design scenario using published axial capacity and torque prediction formulae. Single and double-helix designs, including an optimised design, intended to minimise installation requirements, with reduced geometry were installed and tested in-flight. Piles in the medium-dense sand for example had significant installation requirements of up to 18.4MNm (torque) and 28.8MN (vertical force) which were accurately predicted using correlations with cone resistance data (CPT). Existing axial capacity design methods did not perform well for these large-scale screw piles, overestimating compressive and tensile capacities. Revised analytical methods for installation and axial capacity estimates are proposed here based on the centrifuge test results.
Original languageEnglish
Pages (from-to)1-19
Number of pages19
JournalGeotechnique
Volume0
Early online date23 Sep 2020
DOIs
Publication statusE-pub ahead of print - 23 Sep 2020
Event1st International Symposium on Screw Piles for Energy Applications - University of Dundee, Dundee, United Kingdom
Duration: 27 May 201928 May 2019

Keywords

  • Screw piles
  • Offshore engineering
  • Renewable energy
  • Wind energy

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