Quantifying stress-induced anisotropy using inter-void constrictions

Shire, Thomas; O’Sullivan, Catherine; Barreto, Daniel; Gaudray, G

doi:10.1680/geot.11.t.020

Cited by 25 publications

(20 citation statements)

References 22 publications

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“…While particles are physical features in the image, the definition of individual voids is more abstract or subjective, as voids connect with each other (Shire et al, 2012). As noted above, here a watershed segmentation approach was used to distinguish individual pores (Atwood et al, 2004).…”

Section: Void Orientationsmentioning

confidence: 99%

Quantifying the evolution of soil fabric during shearing using directional parameters

Fonseca¹,

O’Sullivan²,

Coop³

et al. 2013

Géotechnique

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142

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Over the past 50 years, experimental studies have repeatedly demonstrated that the mechanical behaviour of sand is sensitive to the material fabric, that is, the arrangement of the grains. Up until now there have been relatively few attempts to describe this fabric quantitatively. Much of our understanding of the link between the particle movements and interactions and the macro-scale response of granular materials, including sand, comes from discrete-element modelling and experiments on 'analogue' sands with simple, idealised shapes. This paper investigates methods of quantifying the directional fabric of a real sand and its evolution under loading. Statistical analyses of the distribution of fabric directional data in terms of particle, contact normal, branch vector and void orientations were carried out at different stages of shearing deformation. The data show that the initial particle orientation fabric that develops during the deposition of the material tends to persist during shearing, while in the post-peak regime the contact normals seem to be reoriented along the direction of the major principal stress. Different patterns were observed within the shear band, as both the particles and the contact normal vectors appeared to rotate along the shear plane.

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Section: Void Orientationsmentioning

confidence: 99%

Quantifying the evolution of soil fabric during shearing using directional parameters

Fonseca¹,

O’Sullivan²,

Coop³

et al. 2013

Géotechnique

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142

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“…The pore throat distribution in granular packings was also theoretically investigated by To et al [50], Jaafar and Likos [3], Reboul et al [1] and Shire et al [51], where the pore throat distribution is estimated from the given particle size distribution of the granular packing. To et al [50] and Reboul et al [1] considered the flow process of suspensions in porous granular packings and therefore the pore throat areas were described by circular voids, which were smaller than the real constrictions sizes.…”

Section: Pore Throat Determinationmentioning

confidence: 99%

“…Refs. [2,3,50,51]. However, the applied models are often inaccurate to determine the constriction size distribution.…”

Section: Pore Throatsmentioning

confidence: 99%

Hydraulic properties of porous sintered glass bead systems

et al. 2017

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In this paper, porous sintered glass bead packings are studied, using X-ray Computed Tomography (XRCT) images at 16 µm voxel resolution, to obtain not only the porosity field, but also other properties like particle sizes, pore throats and the permeability. The influence of the sintering procedure and the original particle size distributions on the microstructure, and thus on the hydraulic properties, is analyzed in detail. The XRCT data are visualized and studied by advanced image filtering and analysis algorithms on to the extracted sub-systems (cubes of different sizes) to determine the correlations between the microstruc- Institute of Applied Mechanics (CE), University of Stuttgart, Pfaffenwaldring 7, 70569 Stuttgart, Germany ture and the measured macroscopic hydraulic parameters. Since accurate permeability measurements are not simple, special focus lies on the experimental set up and procedure, for which a new innovative multi-purpose cell based on a modular concept is presented. Furthermore, segmented voxel-based images (defining the microstructure) are used for 3D (three-dimensional) lattice Boltzmann simulations to directly compute some of the properties in the creeping flow regime. A very good agreement between experimental and numerical porosity and permeability could be achieved, in most cases, validating the numerical model and results. Porosity and permeability gradients along the sample height could be related to gravity acting during sintering. Furthermore, porosity increases in the outer zones of the samples due to the different contact geometry between the beads and the confining cylinder wall during sintering (which is replaced by a membrane during permeability testing to close these pores at the surface of the sample). The influence of different filters on the gray scale distributions and the impact of the segmentation procedure on porosity and permeability is systematically studied. The complex relationships and dependencies between numerically determined permeabilities and hydraulic influence parameters are investigated carefully. In accordance to the well-known Kozeny-Carman model, a similar trend for local permeability values in dependence on porosity and particle diameter is obtained. Other than statistical models, which estimate the pore throat distribution on the basis of the particle size distribution, in this study XRCT scans are used to determine the pore throats in sintered granular systems, which are finally linked to the intrinsic permeability through the lattice Boltzmann simulations. From the μXRCT analysis two distinct peaks in pore throat distributions could be identified, which can be clearly assigned to typical pore throat areas occurring in polydisperse granular systems. Moreover, a linear dependency between average pore throat diameter and porosity as well as between permeability and pore throat diameter is reported. Furthermore, almost identical mean values for porosity and permeability are found from sub-system and full-system REV analysis. For sintered granular...

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“…Durán et al (2010) stated that deformation of pores and tangential displacement at contacts are the primary contributors to strain in granular assemblies. Shire et al (2013) specifically considered pore constrictions to explore anisotropy in numerical simulation of elemental shear tests (in triaxial compression, plane strain and triaxial extension modes), where the orientation of pore constrictions was related to the force chain network.…”

Section: Introductionmentioning

confidence: 99%

“…Konishi and Naruse (1988) presented a 2D void tensor allowing for the determination of the principal orientation of individual pores, which can subsequently be implemented in a mean void tensor to describe a collection of pores. A 3D fabric tensor is implemented in (Shire et al, 2013) to quantify stress-induced anisotropy by considering the orientation of pore constrictions. This paper presents quantitative tools to describe shape, volume distribution and orientation characteristics of the pore space in granular assemblies.…”

Section: Introductionmentioning

confidence: 99%

Pore shapes, volume distribution and orientations in monodisperse granular assemblies

et al. 2015

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The complex mechanical behaviour of granular materials is commonly studied by considering the evolving particle contact network. An often overlooked feature is the influence of micro-scale geometric configuration of pores on the macroscopic response. This paper presents a series of tools to quantify the shape, volume distribution and orientation characteristics of the pore space. The proposed approach is validated using data from physical and numerical experiments with monodisperse assemblies of spheres. A pore shape parameter is proposed that relates pore volume and surface area, and is analytically related to the void ratio and the number of edges forming the polyhedral pore unit cell. The pore volume distribution is shown to be uniquely described by the analytical k-gamma distribution proposed by Aste and Di Matteo (2008). A pore orientation tensor is introduced to define the principal orientation of individual pore units. This is subsequently used to define a global orientation tensor that reveals an isotropic pore network for the reference monodisperse assemblies. The global orientation tensor is analytically expressed in terms of the parameters defining the pore volume distribution. The pore characteristics described in this paper provide the basis for describing the evolution of the pore space during deformation and its relationship to mechanical properties.

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Quantifying stress-induced anisotropy using inter-void constrictions

Cited by 25 publications

References 22 publications

Quantifying the evolution of soil fabric during shearing using directional parameters

Quantifying the evolution of soil fabric during shearing using directional parameters

Hydraulic properties of porous sintered glass bead systems

Pore shapes, volume distribution and orientations in monodisperse granular assemblies

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