Rigidity phase transition in granular packings

Aharonov, Einat; Sparks, D. W.

doi:10.1103/physreve.60.6890

Cited by 132 publications

(137 citation statements)

References 28 publications

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“…Near and above the critical volume fraction for the same boundary conditions the granular aggregate may exhibit either slow creeping flow, solid-like behavior, or both. The latter case, known as stick-slip phenomenon, is observed both experimentally and numerically [2,11,28]. In an experiment under constant volume boundary conditions a series of stick-slip events occur without a significant change in the solid fraction, which is insensitive to global rearrangements relieving the accumulated stress.…”

Section: Molecular Dynamics Simulationsmentioning

confidence: 98%

“…A small rearrangement of the force network may result in strong fluctuations of either field, while such quantities as the solid fraction or granular temperature will remain virtually constant. It is known that granular aggregates exhibit rigidity phase transition near the critical volume fraction ν c [11]. When the volume fraction is near or above ν c , the granular material has elasto-plastic rheology and below this critical value it behaves as a fluid.…”

Section: Molecular Dynamics Simulationsmentioning

confidence: 99%

“…In the last few year there have been many experimental [1,2,3,4,5,6,7] and theoretical [8,9,10,11,12,13,14] studies that explored a broad range of granular flow conditions from rapid dilute flows to slow dense flows, as well as the details of the shear-driven fluidization transition. While dilute granular flows can be well described by the kinetic theory of dissipative granular gases [15], dense granular flows still present significant difficulty in formulation of a continuous theory.…”

Section: Introductionmentioning

confidence: 99%

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Partially fluidized shear granular flows: Continuum theory and molecular dynamics simulations

2003

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The continuum theory of partially fluidized shear granular flows is tested and calibrated using two dimensional soft particle molecular dynamics simulations. The theory is based on the relaxational dynamics of the order parameter that describes the transition between static and flowing regimes of granular material. We define the order parameter as a fraction of static contacts among all contacts between particles. We also propose and verify by direct simulations the constitutive relation based on the splitting of the shear stress tensor into a"fluid part" proportional to the strain rate tensor, and a remaining "solid part". The ratio of these two parts is a function of the order parameter. The rheology of the fluid component agrees well with the kinetic theory of granular fluids even in the dense regime. Based on the hysteretic bifurcation diagram for a thin shear granular layer obtained in simulations, we construct the "free energy" for the order parameter. The theory calibrated using numerical experiments with the thin granular layer is applied to the surface-driven stationary two dimensional granular flows in a thick granular layer under gravity.

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Section: Molecular Dynamics Simulationsmentioning

confidence: 98%

Section: Molecular Dynamics Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Partially fluidized shear granular flows: Continuum theory and molecular dynamics simulations

2003

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“…The DEM approach has successfully been used to investigate various aspects of fault gouge processes in 2D (e.g. AHARONOV and SPARKS, 1999;MORGAN, 1999) and more recently 3D (e.g. HAZZARD and MAIR, 2003), but these studies have generally involved minimal evolution of the individual gouge grains.…”

Section: Methodsmentioning

confidence: 99%

Breaking Up: Comminution Mechanisms in Sheared Simulated Fault Gouge

Mair

Abe

2011

Pure Appl. Geophys.

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Abstract-The microstructural state and evolution of fault gouge has important implications for the mechanical behaviour, and hence the seismic slip potential of faults. We use 3D discrete element (DEM) simulations to investigate the fragmentation processes operating in fault gouge during shear. Our granular fault gouge models consist of aggregate grains, each composed of several thousand spherical particles stuck together with breakable elastic bonds. The aggregate grains are confined between two blocks of solid material and sheared under a given normal stress. During shear, the grains can fragment in a somewhat realistic way leading to an evolution of grain size, grain shape and overall texture. The 'breaking up' of the fault gouge is driven by two distinct comminution mechanisms: grain abrasion and grain splitting. The relative importance of the two mechanisms depends on applied normal stress, boundary wall roughness and accumulated shear strain. If normal stress is sufficiently high, grain splitting contributes significantly to comminution, particularly in the initial stages of the simulations. In contrast, grain abrasion is the dominant mechanism operating in simulations carried out at lower normal stress and is also the main fragmentation mechanism during the later stages of all simulations. Rough boundaries promote relatively more grain splitting whereas smooth boundaries favor grain abrasion. Grain splitting (plus accompanying abrasion) appears to be an efficient mechanism for reducing the mean grain size of the gouge debris and leads rapidly to a power law size distribution with an exponent that increases with strain. Grain abrasion (acting alone) is an effective way to generate excess fine grains and leads to a bimodal distribution of grain sizes. We suggest that these two distinct mechanisms would operate at different stages of a fault's history. The resulting distributions in grain size and grain shape may significantly affect frictional strength and stability. Our results therefore have implications for the earthquake potential of seismically active faults with accumulations of gouge. They may also be relevant to the susceptibility of rockslides since non-cohesive basal shear zones will evolve in a similar way and potentially control the dynamics of the slide.

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“…We identified different regions in the σ n − V X,0 parameter space where the system follows either a stick-slip dynamics or is in steady sliding mode. These two regimes are typical of dynamical regime for the granular layer [31].…”

Section: Model Descriptionmentioning

confidence: 99%

Effect of boundary vibration on the frictional behavior of a dense sheared granular layer

et al. 2014

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We report results of 3D Discrete Element Method (DEM) simulations aiming at investigating the role of the boundary vibration in inducing frictional weakening in sheared granular layers. We study the role of different vibration amplitudes applied at various shear stress levels, for a granular layer in the stick-slip regime and in the steady-sliding regime. Results are reported in terms of friction drops and kinetic energy release associated with frictional weakening events. We find that larger vibration amplitude induces larger frictional weakening events. The results show evidence of a threshold below which no induced frictional weakening takes place. Friction drop size 2 is found to be dependent on the shear stress at the time of vibration. A significant increase in the ratio between the number of slipping contacts to the number of sticking contacts in the granular layer is observed for large vibration amplitudes. These vibration-induced contact rearrangements enhance particle mobilization and induces a friction drop and kinetic energy release. This observation provides some insight into the grain-scale mechanisms of frictional weakening by boundary vibration in a dense sheared granular layer. In addition to characterizing the basic physics of vibration induced shear weakening, we are attempting to understand how a fault fails in the earth under seismic wave forcing. This is the well know phenomenon of dynamic earthquake triggering. We believe that the granular physics are key to this understanding.

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Rigidity phase transition in granular packings

Cited by 132 publications

References 28 publications

Partially fluidized shear granular flows: Continuum theory and molecular dynamics simulations

Partially fluidized shear granular flows: Continuum theory and molecular dynamics simulations

Breaking Up: Comminution Mechanisms in Sheared Simulated Fault Gouge

Effect of boundary vibration on the frictional behavior of a dense sheared granular layer

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