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Experimental micromechanics: grain-scale observation of sand Deformation

Andò, Edward; Hall, Stephen LU ; Viggiani, Gioacchino; Desrues, Jacques and Bésuelle, Pierre (2012) In Géotechnique Letters 2(3). p.107-112
Abstract
Strain localisation plays a key role in the deformation of granular materials. Such localisation involves bands of just a few grains wide, which dominate the material's macroscopic response. This grain-scale phenomenon presents challenges for continuum modelling, which is the rationale behind models that explicitly take micro-scales into account. These in turn require micro-scale experimental analysis. In this work, X-ray tomography is used to image a small sample of oolitic sand while it deforms under triaxial compression. Grains are followed with a technique combining recent developments in image correlation and particle tracking. From these rich data, the evolution of the material in a subvolume of a thousand grains inside the sample... (More)
Strain localisation plays a key role in the deformation of granular materials. Such localisation involves bands of just a few grains wide, which dominate the material's macroscopic response. This grain-scale phenomenon presents challenges for continuum modelling, which is the rationale behind models that explicitly take micro-scales into account. These in turn require micro-scale experimental analysis. In this work, X-ray tomography is used to image a small sample of oolitic sand while it deforms under triaxial compression. Grains are followed with a technique combining recent developments in image correlation and particle tracking. From these rich data, the evolution of the material in a subvolume of a thousand grains inside the sample (which contains 53 000 grains) is presented. The subvolume is chosen to lie inside the shear band that appears at the sample scale. Three-dimensional (3D) grain kinematics are analysed in three increments: the beginning of the test, the peak of the sample's macroscopic axial stress response and the residual stress state. When the sample's deformation is homogeneous (increment one) or fully localised (increment three), the kinematics of the grains in the subvolume appear to be representative of the kinematics occurring at the sample scale, allowing micro-mechanical observations to be made. In the transition from homogeneous to localised deformation (increment two), however, the scale of observation requires a zoom out of the subvolume to the sample scale in order to capture the complex mechanisms at play. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
laboratory tests, strain localisation, sand
in
Géotechnique Letters
volume
2
issue
3
pages
107 - 112
publisher
ICE Publishing Ltd.
external identifiers
  • Scopus:84871830044
ISSN
2045-2543
DOI
10.1680/geolett.12.00027
language
English
LU publication?
yes
id
c6a85bfc-5d26-4ce7-832d-b1908795e929 (old id 3164461)
date added to LUP
2012-11-13 10:28:05
date last changed
2016-10-13 04:31:15
@misc{c6a85bfc-5d26-4ce7-832d-b1908795e929,
  abstract     = {Strain localisation plays a key role in the deformation of granular materials. Such localisation involves bands of just a few grains wide, which dominate the material's macroscopic response. This grain-scale phenomenon presents challenges for continuum modelling, which is the rationale behind models that explicitly take micro-scales into account. These in turn require micro-scale experimental analysis. In this work, X-ray tomography is used to image a small sample of oolitic sand while it deforms under triaxial compression. Grains are followed with a technique combining recent developments in image correlation and particle tracking. From these rich data, the evolution of the material in a subvolume of a thousand grains inside the sample (which contains 53 000 grains) is presented. The subvolume is chosen to lie inside the shear band that appears at the sample scale. Three-dimensional (3D) grain kinematics are analysed in three increments: the beginning of the test, the peak of the sample's macroscopic axial stress response and the residual stress state. When the sample's deformation is homogeneous (increment one) or fully localised (increment three), the kinematics of the grains in the subvolume appear to be representative of the kinematics occurring at the sample scale, allowing micro-mechanical observations to be made. In the transition from homogeneous to localised deformation (increment two), however, the scale of observation requires a zoom out of the subvolume to the sample scale in order to capture the complex mechanisms at play.},
  author       = {Andò, Edward and Hall, Stephen and Viggiani, Gioacchino and Desrues, Jacques and Bésuelle, Pierre},
  issn         = {2045-2543},
  keyword      = {laboratory tests,strain localisation,sand},
  language     = {eng},
  number       = {3},
  pages        = {107--112},
  publisher    = {ARRAY(0x5b55768)},
  series       = {Géotechnique Letters},
  title        = {Experimental micromechanics: grain-scale observation of sand Deformation},
  url          = {http://dx.doi.org/10.1680/geolett.12.00027},
  volume       = {2},
  year         = {2012},
}