Flat boundaries and their effect on sand testing

Marketos, G.; Bolton, M. D.

doi:10.1002/nag.835

Cited by 44 publications

(33 citation statements)

References 15 publications

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“…Specimen height is less important here because no attempt is made to describe possible strain localisation inside the specimens. When localisation is of concern the strong horizontal boundary effects discussed by Marketos & Bolton (2010) should be considered.…”

Section: Upscaling Proceduresmentioning

confidence: 99%

An approach to enhance efficiency of DEM modelling of soils with crushable grains

Ciantia¹,

Arroyo²,

Calvetti³

et al. 2015

Géotechnique

181

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In this study oedometric compression tests of hydrocarbon coke, Fontainebleau sand and silica sand are simulated in three dimensions using breakable particles. The method adapts a rigorous breakage criterion for elasto-brittle spheres to represent failure of grains isolated between platens or within granular masses. The breakage criterion allows for the effect of particle bulk and contact properties to be treated separately. A discrete fragmentation multigenerational approach is applied as a spawning procedure. The number of particles quickly increases during the simulation, but is kept manageable by systematic fine exclusion and upscaling. Fine exclusion leads to mass losses between generations, but that loss is accounted for outside the mechanical model. Sensitivity analysis shows that it is enough to keep 53% of the crushed particle mass within the mechanical model to correctly reproduce experimental macroscopic behaviour. Practical upscaling rules are proposed for (a) contact stiffness, (b) breakage criteria and (c) grain size distribution, and validated simulating the same test, reducing by half the initial number of particles. The results are promising as both the mechanical and grading evolution are well captured with two orders of magnitude savings in computing efficiency.

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Section: Upscaling Proceduresmentioning

confidence: 99%

An approach to enhance efficiency of DEM modelling of soils with crushable grains

Ciantia¹,

Arroyo²,

Calvetti³

et al. 2015

Géotechnique

181

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“…The projected-area of this region was measured by connecting the centroids of the outer grains as shown for stages 1 and 4 in Figure 8 difference between major principal strains) calculated relative to the initial geometry in Figure 8(a) for the three subsequent deformation stages. The strains were calculated from the entire set of grain displacements using the best fit approach described in [41]. Positive volumetric strains indicate dilation.…”

Section: Macroscopic Response To Loadmentioning

confidence: 99%

In situ study of granular micromechanics in semi-solid carbon steels

et al. 2013

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This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent repository link AbstractThe granular micromechanics of semi-solid steel at 80% solid are studied by synchrotron radiography. A particulate soil mechanics approach to image analysis shows that deformation occurs by the translation and rotation of quasi-rigid grains under the action of contact forces, and that the changes in directional fabric and grain-grain contacts occur by mechanisms similar to those of highly compacted soils including "locked sands". Grain-scale phenomena are then linked to the macroscopic displacement and strain fields and it is shown that shear-induced dilation is a fundamental response at both the grain and macro scales. Based on this, recommendations are made on future rheology experiments.

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“…Marketos and Bolton [10] showed how the apparent macroscale stiffness of an oedometric test could be strongly affected by the microscale details of the contact at the boundary top and bottom walls. For axisymmetric problems, Cui et al [6] and Arroyo et al [2] have shown that rigid walls enforcing symmetry conditions induce specific microstructural features and result in changes of macroscopic response.…”

Section: Introductionmentioning

confidence: 99%

Steady state of solid-grain interfaces during simulated CPT

Butlanska¹,

Arroyo²,

Gens³

2013

Studia Geotechnica Et Mechanica

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It has recently been shown (Arroyo et al. [1]) that 3D DEM models are able to reproduce with reasonable accuracy the macroscopic response of CPT performed in calibration chambers filled with sand. However, the cost of each simulation is an important factor. Hence, to achieve manageable simulation times the discrete material representing the sand was scaled up to sizes that were more typical of gravel than sand. A side effect of the scaled-up discrete material size employed in the model was an increased fluctuation of the macro-response that can be filtered away to observe a macroscopic steady-state cone resistance. That observation is the starting point of this communication, where a series of simulations in which the size ratio between penetrometer and particles is varied are systematically analyzed. A micromechanical analysis of the penetrometer-particle interaction is performed. These curves reveal that a steady state is arrived also at the particle-cone contact level. The properties of this dynamic interface are independent of the initial density of the granular material.

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Flat boundaries and their effect on sand testing

Cited by 44 publications

References 15 publications

An approach to enhance efficiency of DEM modelling of soils with crushable grains

An approach to enhance efficiency of DEM modelling of soils with crushable grains

In situ study of granular micromechanics in semi-solid carbon steels

Steady state of solid-grain interfaces during simulated CPT

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