Full-scale observations of dynamic and static axial responses of offshore piles driven in chalk and tills

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Title: Full-scale observations of dynamic and static axial responses of offshore piles driven in chalk and tills
Authors: Buckley, R
Jardine, R
Kontoe, S
Barbosa, P
Schroeder, F
Item Type: Journal Article
Abstract: This paper describes and interprets tests on piles driven through glacial tills and chalk at a Baltic Sea windfarm, covering an advance trial campaign and later production piling. The trials involved six instrumented 1.37m diameter steel open-ended tubes driven in water depths up to 42m. Three piles were tested statically, with dynamic re-strike tests on paired piles, at 12-15 week ages. Instrumented dynamic driving and re-strike monitoring followed on up to 3.7m diameter production piles. During driving, the shaft resistances developed at fixed depths below sea-bed fell markedly during driving, with particularly sharp reductions occurring in the chalk. Shaft resistances increased markedly after driving and good agreement was seen between long-term capacities interpreted from parallel static and dynamic tests. Analyses employing the sites’ geotechnical profiles show long-term shaft resistances in the chalk that far exceed those indicated by current design recommendations, while newly proposed procedures offer good predictions. The shaft capacities mobilised in the low-plasticity tills also grew significantly over time, within the broad ranges reported for sandy soils. The value of offshore field testing in improving project outcomes and design rules is demonstrated; the approach described may be applied to other difficult seabed conditions.
Date of Acceptance: 24-Jun-2019
URI: http://hdl.handle.net/10044/1/71677
ISSN: 0016-8505
Publisher: Thomas Telford
Journal / Book Title: Géotechnique
Copyright Statement: This paper is embargoed until publication.
Sponsor/Funder: Technology Strategy Board
Institution of Civil Engineers
Institution of Civil Engineers
Engineering & Physical Science Research Council (E
Scottishpower Renewables (UK) Limited
Funder's Grant Number: 101968
1603
R & D 0213
EP/P033091/1
TBC
Keywords: 0905 Civil Engineering
Geological & Geomatics Engineering
Publication Status: Accepted
Embargo Date: publication subject to indefinite embargo
Appears in Collections:Civil and Environmental Engineering
Geotechnics



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