Visualization of Crushing Evolution in Granular Materials under Compression Using DEM

Lobo-Guerrero, Sebastián; Vallejo, Luis E.; Vesga, L. F.

doi:10.1061/(asce)1532-3641(2006)6:3(195)

Cited by 84 publications

(32 citation statements)

References 19 publications

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“…Later, Lobo-Guerrero & Vallejo (2005) and Lobo-Guerrero et al (2006) elected to calculate particle stress using the maximum contact force, as F max /d (in two dimensions), and employing a size effect on particle strength. Use of the maximum contact forces does not consider any additional contacts on a particle; however, they took particle coordination number into account by only allowing particles with three or fewer contacts to break.…”

Section: A Review Of Breakage Criteria Used In Demmentioning

confidence: 99%

Particle breakage criteria in discrete-element modelling

Bono

McDowell

2016

Géotechnique

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Previous work by the authors using the discrete-element method (DEM) has used the octahedral shear stress within a sphere together with a Weibull distribution of strengths and a size effect on average strength, to determine whether fracture occurs or not. This leads to fractal particle size distributions and a normal compression line which are consistent with experimental data. However, there is no agreement in the literature as to what the fracture criterion should be, and as yet it is not clear whether other criteria could lead to the correct evolution of voids ratio and particle size distribution under increasing stress. Various possibilities for the criterion have been studied in detail here to ascertain whether these other criteria may give the correct behaviour under normal compression. The use of the major principal stress within a particle, the mean stress and the stress calculated from the maximum contact force on a particle are each investigated as alternatives to the octahedral shear stress. Only the criterion based on the maximum contact force is shown to give behaviour observed experimentally and the simulations shed further insight into the micro mechanics of normal compression.

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Section: A Review Of Breakage Criteria Used In Demmentioning

confidence: 99%

Particle breakage criteria in discrete-element modelling

Bono

McDowell

2016

Géotechnique

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“…However, it is a challenge to consider both irregular particle shape and ballast degradation in DEM modelling of railway ballast; e.g. Lobo-Guerrero and Vallejo [20,21] published work on DEM of ballast degradation but only circular particles were used, and the studies where the complex ballast particle shapes were modelled, particle breakage was ignored [22][23][24][25]. Considering that most ballast degradation is not attributable to particle splitting but instead primarily particle abrasion [4,5], Lu and McDowell [14,15] introduced a tetrahedral shaped clump with small breakable asperities ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Discrete element modelling of scaled railway ballast under triaxial conditions

McDowell

2016

Granular Matter

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The aim of this study is to demonstrate the use of tetrahedral clumps to model scaled railway ballast using the discrete element method (DEM). In experimental triaxial tests, the peak friction angles for scaled ballast are less sensitive to the confining pressure when compared to fullsized ballast. This is presumed to be due to the size effect on particle strength, whereby smaller particles are statistically stronger and exhibit less abrasion. To investigate this in DEM, the ballast is modelled using clumps with breakable asperities to produce the correct volumetric deformation. The effects of the quantity and properties of these asperities are investigated, and it is shown that the strength affects the macroscopic shear strength at both high and low confining pressures, while the effects of the number of asperities diminishes with increasing confining pressure due to asperity breakage. It is also shown that changing the number of asperities only affects the peak friction angle but not the ultimate friction angle by comparing the angles of repose of samples with different numbers of asperities.

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“…Lobo-Guerrero & Vallejo (2005a) and Lobo-Guerrero et al (2006) used 2D DEM simulations to investigate the evolution of particle fracture under isotropic, biaxial and uniaxial loading conditions. They adopted the particle replacement approach described earlier to model particle breakage.…”

Section: Introductionmentioning

confidence: 99%

3D evolution of sand fracture under 1D compression

Cil¹,

Alshibli²

2014

Géotechnique

119

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Three-dimensional (3D) synchrotron microtomography (SMT) and the discrete-element method (DEM) were used to investigate the evolution of particle fracture and deformation behaviour of a granular assembly subjected to the k 0 -loading condition. A series of one-dimensional (1D) compression laboratory experiments were first conducted to better understand the effect of specimen aspect ratio (height-to-diameter ratio, H/D) on deformation behaviour, which demonstrated that changing the specimen aspect ratio influences the stress-strain response of sand. 1D compression was simulated using a 3D DEM model by mapping particle positions from SMT images. Crushable sand particles were modelled in DEM using agglomerates of spherical sub-particles that were bonded by parallel bonds. The DEM model successfully predicted the compressive behaviour of specimens with different aspect ratios. The experimental and DEM results show that the onset of particle fracture and specimen yielding occur at the same strain level. The evolution and distribution of particle fracture were analysed non-destructively at the particle and specimen scales using SMT images and the DEM model. The SMT images revealed that the majority of the particle fracture occurred in particles close to the loading platen. The onset of the fracture pattern of individual sand particles within the granular assembly was also examined at consecutive strain levels using SMT images and DEM simulation results. The development and collapse of force chains were investigated using the DEM model and it was observed that the agglomerates that are part of a strong force chain mostly experience bond breakages. Combining SMT imaging technique and DEM simulations provided valuable insight into complex micromechanical processes occurring during the compression of crushable granular materials.

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Visualization of Crushing Evolution in Granular Materials under Compression Using DEM

Cited by 84 publications

References 19 publications

Particle breakage criteria in discrete-element modelling

Particle breakage criteria in discrete-element modelling

Discrete element modelling of scaled railway ballast under triaxial conditions

3D evolution of sand fracture under 1D compression

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