DEM study on the effect of roundness on the shear behaviour of granular materials

Nie, Zhihong; Fang, Chuanfeng; Gong, Jian; Liang, Zhenyu

doi:10.1016/j.compgeo.2020.103457

Cited by 63 publications

(18 citation statements)

References 60 publications

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“…In dry granular media, the restriction of particle rotations is a consequence of the nonspherical particle shape [21]. A general observation is that μ * increases as the particle shape deviates even slightly from a circle or a sphere, but then tends to saturate with shape deviation [22][23][24][25][26][27][28][29]. Another interesting result concerns the ideal case of frictionless grains.…”

Section: Introductionmentioning

confidence: 99%

Combined effects of contact friction and particle shape on strength properties and microstructure of sheared granular media

et al. 2020

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We present a systematic numerical investigation concerning the combined effects of sliding friction and particle shape (i.e., angularity) parameters on the shear strength and microstructure of granular packings. Sliding friction at contacts varied from 0 (frictionless particles) to 0.7, and the particles were irregular polygons with an increasing number of sides, ranging from triangles to disks. We find that the effect of local friction on shear strength follows the same trend for all shapes. Strength first increases with local friction and then saturates at a shape-dependent value. In contrast, the effect of angularity varies, depending on the level of sliding friction. For low friction values (i.e., under 0.3), the strength first increases with angularity and then declines for the most angular shapes. For high friction values, strength systematically increases with angularity. At the microscale, we focus on the connectivity and texture of the contact and force networks. In general terms, increasing local friction causes these networks to be less connected and more anisotropic. In contrast, increasing particle angularity may change the network topology in different directions, directly affecting the macroscopic shear strength. These analyses and data constitute a first step toward understanding the joint effect of local variables such as friction and grain shape on the macroscopic rheology of granular systems.

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Section: Introductionmentioning

confidence: 99%

Combined effects of contact friction and particle shape on strength properties and microstructure of sheared granular media

et al. 2020

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“…The 3D morphology of particles can be expressed in terms of form, convexity and angularity, usually measured by the following descriptors (Nie et al 2020): two aspect ratios of principal dimensions, i.e. elongation index EI and the flatness index FI, sphericity, convexity C V and roundness R. EI, FI and sphericity are commonly used to describe the particle form, while R is used to quantify the particle angularity (Zhao and Wang 2016).…”

Section: D Blocks' Morphology Quantificationmentioning

confidence: 99%

Influence of Block form on the Shear Behaviour of Soft Soil–Rock Mixtures by 3D Block Modelling Approaches

et al. 2022

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The influence of block forms on the shear behaviour of soil–rock mixtures with soft blocks (soft S–RMs) can be efficiently investigated by the discrete element method (DEM) on the basis of accurate 3D models accounting for the block breakage. This paper proposes a novel modelling approach, based on the spherical harmonics series, for the generation of 3D block geometries with different forms but same convexity and angularity. An already existing non-overlapping modelling approach was improved, characterized by a reduced computational cost, for the set-up of 3D block DEM models accounting for the block breakage. A number of soft S–RM DEM samples, subjected to numerical direct shear tests, were generated to analyze the influence of block forms and volumetric block proportion VBP on the mesoscopic and macroscopic behaviours. The results showed that the breakage degree is maximum for the spheroidal blocks, followed by the oblate, prolate and blade ones, due to the combined influence of the block frictional sliding and rotation. The shear strength of soft S–RMs is mainly controlled by the block interlocking and breakage, being maximum in the case of spheroidal block samples when the applied normal stress is low and in the case of prolate and blade ones for a high normal stress. It was found that a nonlinear Mohr–Coulomb criterion can provide a good description of the shear strength envelope of soft S–RMs. Soft S–RMs are characterized by a higher friction angle if composed by spheroidal and prolate blocks when the VBP is 40%, due to their elevated block interlocking, and in the case of prolate and blade blocks when the VBP is 60% at the higher normal stress, due to their lower block breakage degree.

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“…To be more precise in capturing particle shape, clump models using multiple spherical particles 14,15 and LS‐DEM 16,17 have also been adopted, which can reflect the irregular concave‐convex characteristics of granular materials such as natural sand. With the introduction of non‐spherical particles, research has been conducted to study the effect of sphericity and roundness on the mechanical behavior of granular materials 18–24 . However, such models are generally computationally costly and are often still unable to simulate small scale surface asperities.…”

Section: Introductionmentioning

confidence: 99%

Influence of small particle surface asperities on macro and micro mechanical behavior of granular material

Pan

Zhang

Wang

2022

Num Anal Meth Geomechanics

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The shape of particles can have a great impact on the mechanical behavior of granular material, which is not only limited to general shape measures such as sphericity and roundness, but also applies for small scale measures such as surface asperities. In this study, triaxial tests on 3D printed particles and DEM tests show that small surface asperities on spherical particles can contribute significantly to the peak strength and dilatancy of granular material, which cannot be reflected by simply altering the traditional contact parameters in DEM. Using polydispersed particles with artificially designed surface asperities in the form of bumps for laboratory and DEM triaxial tests, both macro and micro scale behavior of granular material are analyzed to reveal the influence of these small surface asperities. The result shows that surface asperities can change the coordination number, anisotropy, and normal contact force on the micro scale, increasing the interlocking between particles and restricting particle rotation, which leads to the increase of peak strength and dilatancy on the macro scale. Although the commonly adopted approach of introducing rolling resistance to reflect shape influence can help to enhance the simulation of stress‐strain relationship, especially for particles with relatively small artificial asperities, the micro scale influence of rolling resistance and surface asperities are found to be different as the size of the asperities increase.

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DEM study on the effect of roundness on the shear behaviour of granular materials

Cited by 63 publications

References 60 publications

Combined effects of contact friction and particle shape on strength properties and microstructure of sheared granular media

Combined effects of contact friction and particle shape on strength properties and microstructure of sheared granular media

Influence of Block form on the Shear Behaviour of Soft Soil–Rock Mixtures by 3D Block Modelling Approaches

Influence of small particle surface asperities on macro and micro mechanical behavior of granular material

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