Time-dependent uplift capacity of driven piles in low to medium density chalk

Francesca Ciavaglia, John Carey, Andrea Diambra

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

A series of load tests have been performed on instrumented 762mm diameter tubular steel piles driven into low to medium density Grade A/B chalk at St. Nicholas-at-Wade, Kent, United Kingdom. This paper presents the results from the static axial uplift tests, which were performed on two piles 7, 50 and 120 days after installation in order to investigate the time dependent variations in shaft resistance. The resultsshow that the static ultimate shaft resistance of this type of chalk can increase by up to a factor of seven over this time period, as a consequence of ‘set-up’ effects. The test results also show that the ‘set-up’ effect is reduced if the pile is subject to lateral loads up to 50% of the ultimate lateral capacity before uplift loading, whilst the application of lateral loading up to 10% of ultimate lateral capacity had negligible influence on the axial capacity. The measured load distribution from strain gauges suggests a mobilization of larger unit shaft resistance in the lower half of the pile. This paper also describes the geotechnical site conditions, the pile instrumentation and the effects of pile-driving on the chalk.
Original languageEnglish
Number of pages7
JournalGéotechnique Letters
Volume7
Issue number1
Publication statusPublished - 12 Jan 2017

Keywords

  • Chalk
  • Offshore engineering
  • Piles & piling

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