Stanier, S.A., Black, J.A. and Hird, C.C. (2013) Modelling helical screw piles in clay and design implications. Proceedings of ICE - Geotechnical Engineering, 167 (5). pp. 447-460. ISSN 1353-2618
Abstract
Helical screw piles are a popular solution for relatively low-capacity, removable or recyclable foundations supporting road and rail signage or similar light structures. When specifying a helical screw pile, a designer must choose the active length and the helical plate spacing ratio, which are governed by the number, spacing and size of the individual helices. This paper presents an investigation using transparent synthetic soil and particle image velocimetry to observe the failure of helical screw piles with helical plate spacing ratios of 1·5–3 and active lengths up to three times the diameter. For the geometries and properties examined, capacity is shown to be a function of active length and the dominant failure mechanism is characterised by the formation of a cylindrical failure surface. A simple analytical model is developed and used to assess the impact of different design methodologies on immediate displacements under loading. A traditional ‘permissible stress' method is shown to be conservative, whereas modern ‘partial factor' methods are more economical and lead to greater immediate displacements for a given design load. Designers using modern ‘partial factor' approaches, such as Eurocode 7, might benefit from specifying a helical plate spacing ratio of less than 1·5 to maximise the stiffness of the response to axial loading and minimise the immediate displacements experienced upon application of working loads.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2013 ICE. Reproduced in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Civil and Structural Engineering (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 12 Jun 2014 10:49 |
Last Modified: | 30 Nov 2014 01:38 |
Published Version: | http://dx.doi.org/10.1680/geng.13.00021 |
Status: | Published |
Publisher: | ICE |
Refereed: | Yes |
Identification Number: | 10.1680/geng.13.00021 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:79300 |