Mechanical properties of inclined frictional granular layers

Atman, A. P. F.; Claudin, Philippe; Combe, Gaël; Martins, Gustavo H. B.

doi:10.1007/s10035-014-0482-8

Cited by 11 publications

(6 citation statements)

References 47 publications

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“…Unlike such steady states, the configurations and the mechanical response of granular materials under small and moderate strains are sensitive to the initial material structure. In addition to their density, initial states are characterized in terms of structural anisotropy, whose importance has long been recognized in experiments [21][22][23][24][25][26], and more recently investigated by numerical means [27][28][29]. Coordination numbers (i.e., average numbers of force-carrying contacts per grain) have also been observed to vary, independently of density.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of one-dimensional compression of granular materials. I. Stress-strain behavior, microstructure, and irreversibility

et al. 2017

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The behavior of a model granular material, made of slightly polydisperse beads with Hertz-Mindlin elastic-frictional contacts, in oedometric compression (i.e., compression along one axis, with no lateral strain) is studied by grain-level numerical simulations. We systematically investigate the influence of the (idealized) packing process on the microstructure and stresses in the initial, weakly confined equilibrium state, and prepare both isotropic and anisotropic configurations differing in solid fraction Φ and coordination number z. Φ (ranging from maximally dense to moderately loose), z (which might vary independently of Φ in dense systems), fabric and force anisotropy parameters, and the ratio K_{0} of lateral stresses σ_{2}=σ_{3} to stress σ_{1} in the compression direction are monitored in oedometric compression in which σ_{1} varies by more than three orders of magnitude. K_{0} reflects the anisotropy of the assembling process and may remain nearly constant in further loading if the material is already oedometrically compressed (as a granular gas) in the preparation stage. Otherwise, it tends to decrease steadily over the investigated stress range. It is related to force and fabric anisotropy parameters by a simple formula. Elastic moduli, separately computed with an appropriate matrix method, may express the response to very small stress increments about the transversely isotropic well-equilibrated states along the loading path, although oedometric compression proves an essentially anelastic process, mainly due to friction mobilization, with large irreversible effects apparent upon unloading. While the evolution of axial strain ε_{1} and solid fraction Φ (or of the void ratio e=-1+1/Φ) with axial stress σ_{1} is very nearly reversible, especially in dense samples, z is observed to decrease (as previously observed in isotropic compression) after a compression cycle if its initial value was high. K_{0} relates to the evolution of internal variables and may exceed 1 in unloading. The considerably greater irreversibility of oedometric compression reported in sands, compared to our model systems, should signal contact plasticity or damage.

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Section: Introductionmentioning

confidence: 99%

Numerical study of one-dimensional compression of granular materials. I. Stress-strain behavior, microstructure, and irreversibility

et al. 2017

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“…To probe the remaining discrepancies, new careful experiments or discrete element simulations performed at slow drum rotation rates over multiple avalanche events would be very valuable. Detailed particle simulations could also help elucidate the grain-scale mechanisms governing slope failure and basal erosion (Atman et al 2014). Likewise, the effects of finite grain size relative to channel width, slope length and flow thickness remain to be clarified.…”

Section: Discussionmentioning

confidence: 99%

“…For erosion to occur (), the basal shear stress must overcome the erosion resistance where is an angle of friction describing the bed resistance to erosion: a greater shear stress is needed to unjam bed grains than to keep them flowing at a slow shear rate (Atman et al. 2014; Farain & Bonn 2023). Note that the angle , like the failure angle , does not take a unique value.…”

Section: Model Formulationmentioning

confidence: 99%

A continuum model of discrete granular avalanches

Liang,

Capart

2024

J. Fluid Mech.

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A simple continuum model is proposed for discrete granular avalanches, as observed in slowly rotating drums. Subject to granular transfer across the basal interface, the model evolves the transient surface inclination and mid-slope velocity profile of the avalanches, from failure to arrest. This is done using new boundary conditions that allow entrainment or detrainment contingent on the basal shear rate. For entrainment to occur, the basal shear stress must overcome the erosion resistance of the jammed deposit, while for detrainment to take place the basal shear rate must vanish. The resulting avalanche dynamics is controlled by a single dimensionless number, the ratio of excess slope at failure to excess resistance to erosion, that can be determined from inclination history data. This number provides a measure of slope brittleness, from which the peak flow rate and arrest inclination can be predicted. Analytical techniques are used to derive model solutions, and clarify the resulting behaviour. Finally, the model is tested by comparing solutions with laboratory experiments and discrete particle simulations.

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“…The transition between solid and liquid phases in granular matter, which is commonly referred to as jamming/unjamming transition, has been extensively studied from both theoretical and experimental perspectives [4,[6][7][8][9][10][11]. Currently, a great effort is being made to under-060007-1 stand the nature of this transition, which is still a subject of debate [12]. The jamming/unjamming transition is not a specific property of granular matter, being observed in many kinds of materials, such as foams [13], emulsions [14], colloids [15], gels [16], and also in usual molecular liquids [17] -glass transition.…”

Section: Introductionmentioning

confidence: 99%

Jamming transition in a two-dimensional open granular pile with rolling resistance

et al. 2014

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We present a molecular dynamics study of the jamming/unjamming transition in twodimensional granular piles with open boundaries. The grains are modeled by viscoelastic forces, Coulomb friction and resistance to rolling. Two models for the rolling resistance interaction were assessed: one considers a constant rolling friction coefficient, and the other one a strain dependent coefficient. The piles are grown on a finite size substrate and subsequently discharged through an orifice opened at the center of the substrate. Varying the orifice width and taking the final height of the pile after the discharge as the order parameter, one can devise a transition from a jammed regime (when the grain flux is always clogged by an arch) to a catastrophic regime, in which the pile is completely destroyed by an avalanche as large as the system size. A finite size analysis shows that there is a finite orifice width associated with the threshold for the unjamming transition, no matter the model used for the microscopic interactions. As expected, the value of this threshold width increases when rolling resistance is considered, and it depends on the model used for the rolling friction. *

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Mechanical properties of inclined frictional granular layers

Cited by 11 publications

References 47 publications

Numerical study of one-dimensional compression of granular materials. I. Stress-strain behavior, microstructure, and irreversibility

Numerical study of one-dimensional compression of granular materials. I. Stress-strain behavior, microstructure, and irreversibility

A continuum model of discrete granular avalanches

Jamming transition in a two-dimensional open granular pile with rolling resistance

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