Shear Band Patterns in Biaxially Sheared Granular Media

2009 ◽  
Author(s):  
J. Török ◽  
L. Brendel ◽  
D. E. Wolf ◽  
Masami Nakagawa ◽  
Stefan Luding
Keyword(s):  
Shear Band ◽  
Granular Media

Monitoring of damage processes in cemented granular materials with acoustic emissions and seismic velocity reduction

2020 ◽  
Author(s):  
Vincent Canel ◽  
Xiaoping Jia ◽  
Michel Campillo ◽  
Ioan R. Ionescu
Keyword(s):  
Acoustic Emission ◽  
Shear Band ◽  
Sound Velocity ◽  
Granular Materials ◽  
Fracture Process ◽  
Granular Media ◽  
Acoustic Emissions ◽  
Shear Band Formation ◽  
Band Formation ◽  
Velocity Decrease

<p>Earthquakes or fault core sliding occur naturally in response to long-term deformation produced by plate tectonics. However, the way the damage or fracture process of rocks control the frictional slip is not well understood. It involves indeed materials in very different states: from granular-like materials near the shear band within the highly cracked fault core [1] to almost cohesive state in distant host rocks. To address this issue, we perform controlled laboratory experiments and new numerical simulations of damage in cemented granular materials to study the material evolution from cohesive to granular-like states under external loading. Our synthetic rocks (porous media) are made of cemented glass beads in which the packing density and the cement property (ductile or brittle) as well its content are tunable [2,3]. Two mechanical tests have been conducted: i) under oedometric load in a cylindrical cell with rigid wall; and ii) under triaxial load in a cell with elastic membrane (confined by atmospheric pressure). The fracture processes are monitored by acoustic waves, measuring the longitudinal ultrasound velocity (active detection) [4] and the acoustic emission (passive detection) [5].</p><p>More precisely, in the case (i) the fracture process is likely associated with the crack increase, spatially diffused without shear-band formation. For a rock sample cemented by a ductile bond, the damage induced by load appears likely as an anomalous deviation in the master curve of stress-strain whereas the combined acoustic detection provides a very clear evidence with an important sound velocity decrease. Upon cyclic unloading-reloading, we recover a power-law scaling of the sound velocity with the pressure similar to the law in purely granular media but with a finite velocity at vanishing pressure which depends on the residual cohesion of the damaged material. When the drop stress occurs intermittently in fractured samples cemented with brittle materials, we measure not only the sound velocity decrease but also acoustic emissions. In the case (ii) under a triaxial load, we observe the formation of shear-bands, i.e. fractures on the scale of the sample at a load much smaller than those applied in the oedometric loading (i). Again, there is a strong elastic softening (velocity decrease) [4]. Finally, we also compare these experiments with the finite-element modelling of damage and wave propagation in 2D dense cemented disk packings with various cement contents and elasto-visco-plastic properties. This numerical simulation allows to characterize the heterogeneous damage of the material at a microscopic scale.</p><p> </p><p><strong>References</strong></p><p>[1] C. Marone, Laboratory-derived friction laws and their applications to seismic faulting, Annu. Rev. Earth Planet. Sci. 26 <strong>1998</strong>, 643-696.</p><p>[2] V. Langlois, X. Jia, Acoustic probing of elastic behavior and damage in weakly cemented granular media, Phys. Rev. E 89 <strong>2014, </strong>023206.</p><p>[3] A. Hemmerle, M. Schröter, L. Goehring, A cohesive granular material with tunable elasticity, Scientific reports <strong>2016.</strong></p><p>[4] Y. Khidas, X. Jia, Probing the shear-band formation in granular media with sound waves, Phys. Rev. E 85 <strong>2012, </strong>051302.</p><p>[5] P.A. Johnson et al., Acoustic emission and microslip precursors to stick-slip failure in sheared granular media, Geophys. Res. Lett. 40 <strong>2013</strong>, 5627-5631.</p>

scholarly journals Shear Band Formation in Granular Media as a Variational Problem

2004 ◽  
Vol 92 (21) ◽  
Author(s):  
T. Unger ◽  
J. Török ◽  
J. Kertész ◽  
D. E. Wolf
Keyword(s):  
Shear Band ◽  
Variational Problem ◽  
Granular Media ◽  
Shear Band Formation ◽  
Band Formation

scholarly journals Emergence of Shear Bands in Confined Granular Systems: Singularity of the q-Statistics

Entropy ◽  
2018 ◽  
Vol 20 (11) ◽  
pp. 862 ◽  
Author(s):  
Léo Viallon-Galiner ◽  
Gaël Combe ◽  
Vincent Richefeu ◽  
Allbens Picardi Faria-Atman
Keyword(s):  
Shear Band ◽  
Granular Media ◽  
Experimental Validation ◽  
Scaling Law ◽  
Shear Bands ◽  
Percolation Cluster ◽  
Granular Systems ◽  
Original Approach ◽  
Exact Point ◽  
Confined System

The statistics of grain displacements probability distribution function (pdf) during the shear of a granular medium displays an unusual dependence with the shear increment upscaling as recently evinced (see “experimental validation of a nonextensive scaling law in confined granular media”). Basically, the pdf of grain displacements has clear nonextensive (q-Gaussian) features at small scales, but approaches to Gaussian characteristics at large shear window scales—the granulence effect. Here, we extend this analysis studying a larger system (more grains considered in the experimental setup), which exhibits a severe shear band fault during the macroscopic straining. We calculate the pdf of grain displacements and the dependency of the q-statistics with the shear increment. This analysis has shown a singular behavior of q at large scales, displaying a non-monotonic dependence with the shear increment. By means of an independent image analysis, we demonstrate that this singular non-monotonicity could be associated with the emergence of a shear band within the confined system. We show that the exact point where the q-value inverts its tendency coincides with the emergence of a giant percolation cluster along the system, caused by the shear band. We believe that this original approach using Statistical Mechanics tools to identify shear bands can be a very useful piece to solve the complex puzzle of the rheology of dense granular systems.

Undrained Shear Band Deformation in Granular Media

1997 ◽  
Vol 123 (6) ◽  
pp. 577-585 ◽  
Author(s):  
Michael A. Mooney ◽  
Gioacchino Viggiani ◽  
Richard J. Finno
Keyword(s):  
Shear Band ◽  
Granular Media ◽  
Band Deformation ◽  
Undrained Shear

Development of shear bands in annular shear granular flows

2002 ◽  
Vol 759 ◽  
Author(s):  
Payman Jalali ◽  
Mo Li
Keyword(s):  
Shear Rate ◽  
Shear Band ◽  
Granular Media ◽  
Shear Bands ◽  
Granular Flows ◽  
Area Fraction ◽  
Entire System ◽  
Local Properties ◽  
System Characteristics ◽  
Solid Area

ABSTRACTUsing hard-disk simulations of relatively dense packs of mono-sized system in an annular Couette geometry the formation of dilute regions inside the granular media, namely shear bands, are investigated. The results represent the influence of entire system characteristics such as solid area fraction and shear rate on the development of shear bands as well as the local properties of grains that cause them to participate in the formation of a shear band. Moreover, simulations have been performed for binary-sized system, which revealed that the formation of such diluted shear bands is unlikely.

Force-chain buckling in granular media: a structural mechanics perspective

2010 ◽  
Vol 368 (1910) ◽  
pp. 249-262 ◽  
Author(s):  
Giles W. Hunt ◽  
Antoinette Tordesillas ◽  
Steven C. Green ◽  
Jingyu Shi
Keyword(s):  
Shear Band ◽  
Finite Number ◽  
Granular Medium ◽  
Granular Media ◽  
Structural Model ◽  
Lateral Displacement ◽  
Force Chain ◽  
Linear Elastic ◽  
Evolutionary Route ◽  
Localized Form

Parallels are drawn between the response of a discrete strut on a linear elastic foundation and force-chain buckling in a constrained granular medium. Both systems buckle initially into periodic shapes, with wavelengths that depend on relative resistances to lateral displacement, and curvature in the buckled shape. Under increasing end shortening, the classical structural model evolves to a localized form extending over a finite number of contributing links. By analogy, it is conjectured that the granular model of force-chain buckling might follow much the same evolutionary route into a shear band.

Influence of Bedding on Shear Band Formation of Quasistatic Granular Media

2009 ◽  
Author(s):  
Zafar Mahmood ◽  
Kazuyoshi Iwashita ◽  
Masami Nakagawa ◽  
Stefan Luding
Keyword(s):  
Shear Band ◽  
Granular Media ◽  
Shear Band Formation ◽  
Band Formation
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