Evolution of fabric anisotropy of granular soils: x-ray tomography measurements and theoretical modelling

Zhao, Chao-Fa; Pinzón, G.; Wiebicke, Max; Andò, Edward; Kruyt, Nicolaas P.; Viggiani, Gioacchino

doi:10.1016/j.compgeo.2021.104046

Cited by 29 publications

(6 citation statements)

References 93 publications

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“…The initial location of the ME inside the localization zone is selected in the middle of the sample, while that of the ME outside this zone is located off the centre line to reduce the influence of the shear band and the boundary constraint on its behaviour. Further sensitivity analysis on the location of the outside ME can be found in Appendix C. The first method adopted to extract ME's behaviour is the fixed Eulerian tracking method, previously used by Zhao et al 32 to capture the microstructural evolution of granular materials in X-ray CT tests topology. In this method, MEs' location inside and outside the localization band remains fixed throughout the shearing process, as illustrated in Figure 10B.…”

Section: Definitions Of the Mesoscale Representative Volume Elementmentioning

confidence: 99%

“…In recent years advanced experimental techniques such as X‐ray tomography imaging or Digital Image Correlation (DIC) have been useful for the detailed analysis of material behaviour. These techniques allow for quantitively measure several aspects of granular material at the grain scale, such as local void ratio, contact number, contact fabric, evolution and size of the shear band 29–32 . Nevertheless, experiment techniques are limited in measuring the forces and stresses at local scales hindering the complete quantification of material response.…”

Section: Introductionmentioning

confidence: 99%

“…These techniques allow for quantitively measure several aspects of granular material at the grain scale, such as local void ratio, contact number, contact fabric, evolution and size of the shear band. [29][30][31][32] Nevertheless, experiment techniques are limited in measuring the forces and stresses at local scales hindering the complete quantification of material response. In contrast to the experimental investigations of granular materials, Discrete Element Modelling (DEM) has become a popular computational tool for conducting numerical experiments to investigate the constitutive response of granular materials.…”

Section: Introductionmentioning

confidence: 99%

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Strain localization in the standard triaxial tests of granular materials: Insights into meso‐ and macro‐scale behaviours

Phan,

Bui,

Nguyen

et al. 2024

Num Anal Meth Geomechanics

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The standard triaxial tests cease to be valid as material tests since the homogeneity of the granular mass is lost when localized failures such as shear bands occur requiring a different approach to interpreting and analyzing material responses at the meso scale from the macro behaviour. This study sheds light on the above issue by analyzing the standard triaxial tests of the granular specimens undergoing localized failure at different scales using DEM. For the first time, the behaviour of material inside and outside of the shear band as well as the entire sample are quantitatively quantified through DEM simulations. The results enable confirmation of various theoretical hypotheses and experimental observations on the localized failure in granular materials. For example, by quantifying the inter‐particle contact forces of materials inside and outside the shear band zone, it is confirmed that the material outside the localization band undergoes inelastic unloading beyond the bifurcation point, while those inside the localization band experience inelastic shearing to reach the critical state. Moreover, the analysis in this study suggests that if the volume of the localization zone can be precisely measured from the experiment, the mesoscale constitutive responses that truly represent the inelastic behaviour can be quantified. This gives rise to a more appropriate method to obtain inelastic constitutive responses of granular materials from specimens undergoing localized failure in triaxial tests.

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Section: Definitions Of the Mesoscale Representative Volume Elementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Strain localization in the standard triaxial tests of granular materials: Insights into meso‐ and macro‐scale behaviours

Phan,

Bui,

Nguyen

et al. 2024

Num Anal Meth Geomechanics

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“…The alignment of force 253 chains suggests anisotropy, another common hallmark of the 254 approach to jamming, in which grains are preferentially aligned 255 and therefore exhibit greater structure (and lower mobility) 256 than randomly oriented grains (41,46,47). Fabric anisotropy 257 refers to properties such as shear strength and dilatancy taking 258 on different values along different directions due to the state 259 of the granular material's microstructure, where microstruc-260 ture refers to the arrangement of particles, void spaces, and 261 interparticle contacts (48). Though it could be characterised 262 with the arrangement of particles and void spaces, this study 263 characterises the microstructure with a fabric tensor based on 264 inter-particle contacts due to forces being transmitted along 265 these contacts, forming force chains (see Methods for the math-266 ematical formulation of the fabric tensor).…”

Section: Anisotropy and The Approach To Shear Jammingmentioning

confidence: 99%

How particle shape affects granular segregation in industrial and geophysical flows

Cunez¹,

Patel²,

Glade³

2023

Preprint

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Industrial and environmental granular flows commonly exhibit a phenomenon known as ``granular segregation," in which grains separate according to physical characteristics (size, shape, density), interfering with industrial applications (cement mixing, medicine and food production) and fundamentally altering the behavior of geophysical flows (landslides, debris flows, pyroclastic flows, riverbeds). While size-induced segregation has been well studied, the role of grain shape is not well understood. Here we conduct numerical experiments to investigate how grain shape affects granular segregation due to grain-grain and grain-fluid interactions. To isolate the former, we compare dry, bidisperse mixtures of spheres alone with mixtures of spheres and cubes in a rotating drum. Results show that while segregation generally increases with particle size ratio, the presence of cubes decreases segregation levels compared to cases with only spheres. Further, we find hysteresis in segregation trends with size ratio; segregation is lowest when the small grains are cubic as they approach a jammed state with reduced mobility. We find similar hysteresis in simulations of a shear-driven coupled fluid-granular flow (e.g., a riverbed), demonstrating that this phenomenon is not unique to rotating drums; however, in contrast to the dry system, we find that total segregation increases in the presence of cubic grains, and fluid drag effects can qualitatively change segregation trends. Our findings demonstrate competing shape-induced segregation patterns in wet and dry flows—independently from grain size controls—with implications for many industrial and geophysical processes.

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“…The importance of the fabric on the emerging mechanical response of geomaterials is undisputed. Experimental quantification of fabric started with 2D plane stress experiments on photoelastic discs (Oda and Konishi 1974) and have since progressed to the study of more complex assemblies of (natural) granular materials using laboratory-or synchrotron-based XCT (Imseeh et al 2018;Rorato et al 2020;Wiebicke et al 2020;Zhao et al 2021). For the latter, directional measurements of fabric are based on geometrical features extracted from the 2D and/or 3D image data.…”

Section: Introductionmentioning

confidence: 99%

Fabric Investigation of Natural Sensitive Clay from 3D Nano- and Microtomography Data

et al. 2022

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The three-dimensional (3D) fabric in natural sensitive clay is quantified from a combination of high resolution nano and microtomographies, scanning electron microscopy, and dynamic light scattering. Although the speckle arising from clay particles and the pores they enclose is discerned in the nanotomography data and compare well with scanning electron microscopy (SEM) images on the same clay, the individual platelet-shaped clay particles cannot be segmented for subsequent quantitative analysis. Regardless, a very wide range of particle sizes-0.1-300 μm-was detected using the current state-of-the-art in imaging and postprocessing. The measured aspect ratios range was 2.5 AE 1; hence, the particles identified were not clay platelets but, rather, mechanically weathered particles embedded in the clay matrix. Furthermore, the smaller particle sizes <80 μm presented a consistent 22-23°deviation in orientation from the horizontal plane, whereas the larger fractions had a horizontal orientation. The latter finding agrees well with prior findings on the inclination of the clay minerals using small angle X-ray scattering. Finally, the measured mean particle size of 450 nm determined from the nano data is corroborated by an independent determination of particle sizes using dynamic light scattering.

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Evolution of fabric anisotropy of granular soils: x-ray tomography measurements and theoretical modelling

Cited by 29 publications

References 93 publications

Strain localization in the standard triaxial tests of granular materials: Insights into meso‐ and macro‐scale behaviours

Strain localization in the standard triaxial tests of granular materials: Insights into meso‐ and macro‐scale behaviours

How particle shape affects granular segregation in industrial and geophysical flows

Fabric Investigation of Natural Sensitive Clay from 3D Nano- and Microtomography Data

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