Discrete element modelling of soil particle fracture

McDowell, G. R.; Harireche, Ouahid

doi:10.1680/geot.52.2.131.40930

Cited by 43 publications

(43 citation statements)

References 10 publications

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“…The internal void ratio and shape indices for each grain type in the 60501‐soil sample are obtained from Katagiri et al () and shown in Figure a. The internal void ratio is a measure of the cracks and voids within a grain and can affect the compressibility and strength of individual grains under stress (McDowell & Harireche, ). Katagiri et al () compared the grain volume estimates from image processing under two different processes, where one contained the volume of internal voids and cracks while the other excluded them.…”

Section: Methodology and Approachmentioning

confidence: 99%

“…These size effects can impact soil behaviors under compressional or shear stresses. For example, as a failure on the grain‐level progresses under compressional loading, the grains with low values of m become smaller and thus stronger, causing a hardening response after an overall failure of the soil specimen (McDowell et al, ; McDowell & Harireche, ). Now the question is how to implement the grain size effects and strength distribution in a PFC model.…”

Section: Methodology and Approachmentioning

confidence: 99%

“…As explained earlier, a grain can be modeled as an agglomerate of spheres bonded together. Following this approach, McDowell and Harireche () described a procedure for obtaining the size effects in a DEM model. They randomly removed zero to 27% of spheres within each grain before loading them under compression.…”

Section: Methodology and Approachmentioning

confidence: 99%

“…This approach regards each grain as a cluster of spheres that individually interact through connecting bonds that may deform and even break once the load on each grain exceeds its internal strength. Several researchers such as McDowell and Harireche () and Wang and Yan () used spherical clusters for simulating crushable soil grains by DEM simulations. This allowed for simulating grain‐level failures under high stresses but tremendously increased the computation time compared to clumping methods.…”

Section: Introductionmentioning

confidence: 99%

“…McDowell and Harireche () introduced further complication in the simulation of granular soil under stresses by following studies (e. g. Billam, ; Lee, ) that experimentally showed even seemingly homogenous grains of similar types and shapes may have a wide range of strength values mainly depending on the size of each grain. They showed that strength of grains and its dependence on the grain size can be described by a Weibull distribution (Weibull & Sweden, ) and can be reproduced by DEM cluster elements with a spherical shape.…”

Section: Introductionmentioning

confidence: 99%

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Simulation of Lunar Soil With Irregularly Shaped, Crushable Grains: Effects of Grain Shapes on the Mechanical Behaviors

2019

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One of the challenges to overcome in Moon mining operations, such as soil handling, drilling, excavation, and wheeled movement, is understanding the mechanical behaviors of lunar soil, which is composed of grains characterized by highly irregular shapes. The impracticality of performing mechanical experiments on lunar soil samples has made computational techniques useful for exploring the mechanical behaviors of lunar soil. This paper uses particle flow code and describes a procedure for simulating lunar soil grains with specific size, shape, and strength distributions. We adopt data from soil samples 64501 and 60501 retrieved in Apollo 16. Lunar soil samples are simulated as assemblies of different shapes of grains consisting of rigid spheres connected through parallel bonds. We classify grains into four categories based on their shape: agglutinate, breccia A, breccia B, and plagioclase. We simulate each grain based on available imaging studies on their shape characteristics. We reveal the significance of grain shape irregularity through angle‐of‐repose tests on samples with and without irregularly shaped agglutinates. Results show that the shape irregularity increases the angle of repose by 6°. We repeat the test under different gravitational acceleration ranging from 0.1 to 25 m/s2 and show that for values below about 10 m/s2, the angle of repose is inversely related to the gravity but above 10 m/s2, remains independent of the gravity. We perform triaxial compression tests to investigate behaviors of simulated samples under confined loadings. The confinement varies from zero to 15 kPa, corresponding to the lateral in situ stress at depths up to 250 cm. The cohesion and friction angle derived from the triaxial tests are shown to agree with the lab and in situ measurements. This numerical practice and presented methodology pave the way for full‐scale simulation of mining operations on the Moon surface.

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Section: Methodology and Approachmentioning

confidence: 99%

Section: Methodology and Approachmentioning

confidence: 99%

Section: Methodology and Approachmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simulation of Lunar Soil With Irregularly Shaped, Crushable Grains: Effects of Grain Shapes on the Mechanical Behaviors

2019

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Cavity expansion analyses of crushable granular materials with state‐dependent dilatancy

Jiang

Sun

2011

Num Anal Meth Geomechanics

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SUMMARYCrushability is one of the important behaviors of granular materials particularly under high stress states, and affects both the deformability and strength of the materials that are in essence associated with state-dependent dilatancy. In this presentation, first, a new critical state model is proposed to take into account the three different modes of compressive deformation of crushable granular materials, i.e. particle rearrangement, particle crushing and pseudo-elastic deformation. Second, the governing equations for cavity expansion in crushable granulates are introduced, in which the state-dependent dilatancy as well as the bounding surface plasticity model are used. Then, the procedure to obtain semi-analytical solutions to cavity expansion in the material is described in detail, in which a commercial differential equation solver is employed. Finally, cavity expansion analyses are carried out on Toyoura sand, a well-documented granular material, to demonstrate the effects of crushability and state-dependent dilatancy. The study shows that particle crushing does occur at both high stress and critical states and affects the stress fields and the deformation behavior of the material surrounding the cavity in association with state-dependent dilatancy. This leads to conclusion that particle crushing and state-dependent dilatancy have to be taken into account when cavity expansion theory is used to interpret cone penetration tests and pressuremeter tests.

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On the role of particle breakage in the shear failure behavior of granular soils by DEM

Wang

Yan

2011

Num Anal Meth Geomechanics

134

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SUMMARYThis article presents a fundamental study on the role of particle breakage on the shear behavior of granular soils using the three-dimensional (3-D) discrete element method. The effects of particle breakage on the stress ratio, volumetric strain, plastic deformation, and shear failure behavior of dense crushable specimens undergoing plane strain shearing conditions are thoroughly investigated through a variety of micromechanical analyses and mechanism demonstrations. The simulation of a granular specimen is based on the effective modeling of realistic fracture behavior of single soil particles, which is demonstrated by the qualitative agreement between the results from platen compression simulations and those from physical laboratory tests.The simulation results show that the major effects of particle breakage include the reduction of volumetric dilation and peak stress ratio and more importantly the plastic deformation mechanisms and the shear failure modes vary as a function of soil crushability. Consistent macro-and micromechanical evidence demonstrates that shear banding and massive volumetric contraction depict the two end failure modes of a dense specimen, which is dominated by particle rearrangement-induced dilation and particle crushing-induced compression, respectively, with a more general case being the combination and competition of the two failure modes in the medium range of soil crushability and confining stress. However, it is further shown that a highly crushable specimen will eventually develop a shear band at a large strain because of the continuous decay of particle breakage.

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Discrete element modelling of soil particle fracture

Cited by 43 publications

References 10 publications

Simulation of Lunar Soil With Irregularly Shaped, Crushable Grains: Effects of Grain Shapes on the Mechanical Behaviors

Simulation of Lunar Soil With Irregularly Shaped, Crushable Grains: Effects of Grain Shapes on the Mechanical Behaviors

Cavity expansion analyses of crushable granular materials with state‐dependent dilatancy

On the role of particle breakage in the shear failure behavior of granular soils by DEM

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