Force chain buckling, unjamming transitions and shear banding in dense granular assemblies

Tordesillas, Antoinette

doi:10.1080/14786430701594848

Cited by 226 publications

(349 citation statements)

References 53 publications

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“…θ * < θ . The sensitivity of the procedures described above to the chosen threshold values has been studied extensively using both experiments and simulations (Peters et al, 2005;Muthuswamy and Tordesillas, 2006;Tordesillas, 2007;Tordesillas and Muthuswamy, 2009). Such studies suggest that our choices for the threshold values for PLV (i.e.…”

Section: Discussionmentioning

confidence: 99%

“…Tordesillas et al, 2010;Tordesillas, 2007). For completeness, we provide a brief outline of these methods here.…”

Section: Appendix a Detection Of Linear And Cyclic Building Blocksmentioning

confidence: 99%

“…This DEM model has been employed to examine the constitutive response of granular assemblies subject to a range of monotonic and cyclic compression and penetration tests (e.g. Muthuswamy and Tordesillas, 2006;Tordesillas, 2007;Tordesillas and Muthuswamy, 2009). Moreover, this model has been subjected to a comprehensive comparative analysis of multiple aspects of granular deformation and failure (e.g.…”

Section: Discrete Element Simulationsmentioning

confidence: 99%

“…Among the most studied is the formation of self-organised load-bearing particle groups called "force chains" which vary in size from a few to many grains that can percolate through the whole sample (e.g. Geng et al, 2003;Oda and Kazama, 1998;Oda et al, 2004;Tordesillas, 2007). From the standpoint of material characterisation and modelling, these emergent structures pose great scientific challenges as their analytical formulation embodies strong nonlinearities and multiscale dynamics in space and time.…”

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confidence: 99%

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Force chain and contact cycle evolution in a dense granular material under shallow penetration

Tordesillas

Steer

Walker

2014

Nonlin. Processes Geophys.

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Abstract. The mechanical response of a dense granular material submitted to indentation by a rigid flat punch is examined. The resultant deformation is viewed as a process of self-organisation. Four aspects of the mechanical response (i.e. indentation resistance, failure, Reynolds' dilatancy, the undeforming "dead zone") are explored with respect to the linear and cyclic structural building blocks of granular media self-organisation: force chains and contact network cycles. Formation and breaking of 3-cycle contacts preferentially occur around and close to the punch uncovering a "dilation zone". This zone encapsulates (i) most of the indentation resistance and is populated by force chains consisting of six or more particles, (ii) all buckling force chains, and (iii) a central, near-triangular, undeforming cluster of grains beneath the punch face. Force chain buckling is confined to the zone's outer regions, beneath the corners and to the sides of the punch where surface material heave forms. Grain rearrangements here involve the creation of 6-, 7-, and 8-cycles -in contrast with Reynolds' postulated cubic packing rearrangements (i.e. 3-cycles opening up to form 4-cycles). In between these intensely dilatant regions lies a compacted triangular grain cluster which moves in near-rigid body with the punch when jammed, but this dead zone unjams and deforms in the failure regimes when adjacent force chains buckle. The long force chains preferentially percolate from the punch face, through the dead zone, fanning downwards and outwards into the material.

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Section: Discussionmentioning

confidence: 99%

“…Tordesillas et al, 2010;Tordesillas, 2007). For completeness, we provide a brief outline of these methods here.…”

Section: Appendix a Detection Of Linear And Cyclic Building Blocksmentioning

confidence: 99%

Section: Discrete Element Simulationsmentioning

confidence: 99%

mentioning

confidence: 99%

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Force chain and contact cycle evolution in a dense granular material under shallow penetration

Tordesillas

Steer

Walker

2014

Nonlin. Processes Geophys.

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“…The baseline model is a discrete element simulation of plane strain biaxial compression under constant confining pressure of an assembly of 5098 spherical particles [8]. A contact moment is introduced to account for the effect of particle shape angularity, e.g.…”

Section: (A) Kinematics Of Hostun Sand Under Triaxial Compressionmentioning

confidence: 99%

Revisiting localized deformation in sand with complex systems

et al. 2013

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Complex systems techniques are used to analyse X-ray micro-CT measurements of grain kinematics in Hostun sand under triaxial compression. Network nodes with the least mean shortest path length to all other nodes, or highest relative closeness centrality, reside in the region where the persistent shear band ultimately develops. This trend, whereby a group of grains distinguishes themselves from the rest in the sample, remarkably manifests from the onset of loading. The shear band's boundaries and thickness, evident from the network communities' borders and essentially constant mean size, provide corroborating evidence of early detection of strain localization. Our findings raise the possibility that the formation and the location of the persistent shear band may be decided in the nascent stages of loading, well before peak shear stress. Grain-scale digital image correlation strain measurements and statistical tests confirm the results are robust. Moreover, the trends are unambiguously reproduced in a discrete element simulation of plane strain compression.

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Shear‐induced force fluctuations and acoustic emissions in granular material

Michlmayr

Cohen

2013

JGR Solid Earth

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[1] We conducted a series of strain-controlled experiments to study the characteristics of a shear zone forming in dense flow of confined dry granular media. The primary objective was to link force fluctuations due to jamming and force network reformation with episodic release of elastic energy as passively monitored by acoustic emission sensors. Under constant deformation rate, the shear stress exhibits a characteristic sawtooth behavior reflecting the strong influence of micromechanical processes on the macroscopic stress-strain behavior. Measured shear stress jumps were highly correlated with low-frequency (< 20 kHz) acoustic emission events. High-frequency (30 kHz-80 kHz) acoustic signals that were measured with different sensors appear to be directly linked to continual grain-scale interactions (e.g., friction, rolling). A conceptual mechanical fiber bundle model (FBM) was used to represent dynamics at the shear zone of large granular assemblies. The model was capable of reproducing the dynamics of stress jumps and associated elastic energy release events. The combination of acoustic emission (AE) measurements and FBM framework offers new insights into the behavior of shear failure and enhances capabilities for resolving grain-scale mechanical processes and for predicting rapid mass movement such as shallow landslides and debris flows.

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Force chain buckling, unjamming transitions and shear banding in dense granular assemblies

Cited by 226 publications

References 53 publications

Force chain and contact cycle evolution in a dense granular material under shallow penetration

Force chain and contact cycle evolution in a dense granular material under shallow penetration

Revisiting localized deformation in sand with complex systems

Shear‐induced force fluctuations and acoustic emissions in granular material

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