The University of Southampton
University of Southampton Institutional Repository

An analytical study of the effect of penetration rate on piezocone tests in clay

An analytical study of the effect of penetration rate on piezocone tests in clay
An analytical study of the effect of penetration rate on piezocone tests in clay

Finite element cavity expansion analysis investigating the effect of penetration rate on piezocone tests in clay is presented. A coupled analysis was performed, in which the rate of cavity expansion was linked to the penetration rate of the cone and the cone angle, using the assumption that the deformation was wholly radial, and took place only between the cone tip and the cone shoulder. The soil was modelled using modified cam clay with two sets of parameters and varying values of overconsolidation ratio (OCR). The influence of penetration rate on the stress and pore pressure distributions was examined. For slower penetration rates, the excess pore pressure at the cone shoulder is lower since consolidation is permitted coincident with penetration. The radial profiles of post-penetration voids ratio demonstrate that partially drained penetration is permitted by volume change in the near field, in addition to radial movement in the far field. The radial distribution of excess pore pressure after slow penetration differs from the undrained case, with a relatively low radial gradient existing at the cone face. As a result, the dissipation curves after slow penetration lag behind those following fast penetration. The cone velocity is made dimensionless by normalizing with the coefficient of consolidation and the cone diameter. 'Backbone' curves of normalized velocity against normalized tip resistance and excess pore pressure capturing the transition from undrained to drained penetration are derived. The normalized pore pressure backbone curve is unique, whilst the normalized tip resistance shows a small dependency on OCR. These backbone penetration curves are compared with centrifuge model piezocone tests conducted at varying rates, and subsequent dissipation tests. The numerical and experimental results suggest that the value of consolidation coefficient operative during the dissipation phase is 2-4 times higher than the virgin compression value due to changes in the operative soil stiffness, as demonstrated from the stress paths of individual soil elements. The use of multirate penetration tests to deduce values of consolidation coefficient is discussed, in light of these differences.

Cavity expansion, Clay, Dissipation test, Piezocone test, Rate effect
0363-9061
501-527
Silva, Marcelo F.
8c6d098f-1698-4b00-8e4e-e21f005dd891
White, David J.
a986033d-d26d-4419-a3f3-20dc54efce93
Bolton, Malcolm D.
9fbf6ba8-1095-4220-a7f6-38f5463a58e7
Silva, Marcelo F.
8c6d098f-1698-4b00-8e4e-e21f005dd891
White, David J.
a986033d-d26d-4419-a3f3-20dc54efce93
Bolton, Malcolm D.
9fbf6ba8-1095-4220-a7f6-38f5463a58e7

Silva, Marcelo F., White, David J. and Bolton, Malcolm D. (2006) An analytical study of the effect of penetration rate on piezocone tests in clay. International Journal for Numerical and Analytical Methods in Geomechanics, 30 (6), 501-527. (doi:10.1002/nag.490).

Record type: Article

Abstract

Finite element cavity expansion analysis investigating the effect of penetration rate on piezocone tests in clay is presented. A coupled analysis was performed, in which the rate of cavity expansion was linked to the penetration rate of the cone and the cone angle, using the assumption that the deformation was wholly radial, and took place only between the cone tip and the cone shoulder. The soil was modelled using modified cam clay with two sets of parameters and varying values of overconsolidation ratio (OCR). The influence of penetration rate on the stress and pore pressure distributions was examined. For slower penetration rates, the excess pore pressure at the cone shoulder is lower since consolidation is permitted coincident with penetration. The radial profiles of post-penetration voids ratio demonstrate that partially drained penetration is permitted by volume change in the near field, in addition to radial movement in the far field. The radial distribution of excess pore pressure after slow penetration differs from the undrained case, with a relatively low radial gradient existing at the cone face. As a result, the dissipation curves after slow penetration lag behind those following fast penetration. The cone velocity is made dimensionless by normalizing with the coefficient of consolidation and the cone diameter. 'Backbone' curves of normalized velocity against normalized tip resistance and excess pore pressure capturing the transition from undrained to drained penetration are derived. The normalized pore pressure backbone curve is unique, whilst the normalized tip resistance shows a small dependency on OCR. These backbone penetration curves are compared with centrifuge model piezocone tests conducted at varying rates, and subsequent dissipation tests. The numerical and experimental results suggest that the value of consolidation coefficient operative during the dissipation phase is 2-4 times higher than the virgin compression value due to changes in the operative soil stiffness, as demonstrated from the stress paths of individual soil elements. The use of multirate penetration tests to deduce values of consolidation coefficient is discussed, in light of these differences.

This record has no associated files available for download.

More information

Accepted/In Press date: 17 August 2005
e-pub ahead of print date: 28 December 2005
Published date: 28 March 2006
Keywords: Cavity expansion, Clay, Dissipation test, Piezocone test, Rate effect

Identifiers

Local EPrints ID: 419844
URI: http://eprints.soton.ac.uk/id/eprint/419844
ISSN: 0363-9061
PURE UUID: d37ca899-0680-476c-87cd-b006ebcf8c3f
ORCID for David J. White: ORCID iD orcid.org/0000-0002-2968-582X

Catalogue record

Date deposited: 23 Apr 2018 16:30
Last modified: 16 Mar 2024 04:32

Export record

Altmetrics

Contributors

Author: Marcelo F. Silva
Author: David J. White ORCID iD
Author: Malcolm D. Bolton

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×