Sand Shear Band Thickness Measurements by Digital Imaging Techniques

Alshibli, Khalid A.; Sture, Stein

doi:10.1061/(asce)0887-3801(1999)13:2(103)

Cited by 138 publications

(48 citation statements)

References 15 publications

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“…As observed from Fig. 8, normalized thickness of shear bands is decreasing with the increase in D 50 , which is in agreement with the observations of earlier researchers [45].…”

Section: Direct Shear Testssupporting

confidence: 82%

Influence of Particle Size on the Friction and Interfacial Shear Strength of Sands of Similar Morphology

Vangla

Latha

2015

Int. J. of Geosynth. and Ground Eng.

120

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Size and morphological characteristics of particles play vital role on the shear and interfacial shear strength of sands. Often, effects of these parameters are merged and cannot be easily separated. Effect of size of the particles on the shear and interfacial shear strength of sands is presented in this paper through direct shear and interface direct shear tests complemented with image analyses and surface roughness studies. To eliminate the effect of morphological characteristics, three sands of different particle sizes with similar morphological characteristics like angularity, roundness, sphericity and roughness were selected for the study. These morphological characteristics for all three sands were determined from the analysis of scanning electron microscope images and were found to be similar for all three sands. It was observed from the symmetric direct shear tests that the particle size has no effect on the peak friction angle when the tests were carried out at same void ratio. However, ultimate friction angles were affected by the particle size. Shear band thickness was estimated from image segmentation analysis of the profiles of colored sand columns during shear and the same was correlated to the particle size. Interface direct shear tests were carried out on sand-geomembrane interfaces to study the effect of particle size on the interfacial shear strength. Microscopic images of geomembranes were captured after the interface shear tests to understand the change in surface roughness of the geomembrane due to particle indentations. Surface roughness studies on geomembrane samples after the tests confirmed that the plowing and groove formation on geomembranes during interface shear tests depend on the particle size as well as the relative roughness of the sand particles with respect to the membrane. Sand of medium particle size showed highest interfacial strength because of more number of effective contacts per unit area of the interface.

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“…As observed from Fig. 8, normalized thickness of shear bands is decreasing with the increase in D 50 , which is in agreement with the observations of earlier researchers [45].…”

Section: Direct Shear Testssupporting

confidence: 82%

Influence of Particle Size on the Friction and Interfacial Shear Strength of Sands of Similar Morphology

Vangla

Latha

2015

Int. J. of Geosynth. and Ground Eng.

120

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“…It was found that the shear strain around the centre of the shear band reaches a value of 500% compared to 10% outside the shear band which leads to a very high void ratio in that zone, [10]. Alshibli and Sture [11] observed values of the void ratio inside the shear band to be greater than the maximum global void ratio.…”

Section: Introductionmentioning

confidence: 97%

Modelling strain localization in granular materials using micropolar theory: numerical implementation and verification

Alshibli

Alsaleh

Voyiadjis

2006

Int. J. Numer. Anal. Meth. Geomech.

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SUMMARYImplementation and applications for a constitutive numerical model on F-75 silica sand, course silica sand and two sizes of glass beads compressed under plane strain conditions are presented in this work. The numerical model is used to predict the stress versus axial strain and volumetric strain versus axial strain relationships of those materials; moreover, comparisons between measured and predicted shear band thickness and inclination angles are discussed and the numerical results compare well with the experimental measurements. The numerical model is found to respond to the changes in confining pressure and the initial relative density of a given granular material. The mean particle size is used as an internal length scale. Increasing the confining pressure and the initial density is found to decrease the shear band thickness and increase the inclination angle. The micropolar or Cosserat theory is found to be effective in capturing strain localization in granular materials. The finite element formulations and the solution method for the boundary value problem in the updated Lagrangian frame (UP) are discussed in the companion paper.

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“…Shear bands in sands are of considerable thickness, with values reported on the scale of about 8-25 grain diameters, e.g., [2,3,14,21,30,34]. The displacement field within the shear band is of particular interest, as once the shear band forms, all significant material straining is confined only to within the shear band, e.g., [30]: subscale kinematics within this material zone then govern macroscopic stress evolution from softening to critical state.…”

Section: Introductionmentioning

confidence: 99%

Characterization of mesoscale instabilities in localized granular shear using digital image correlation

Rechenmacher

Abedi

Chupin³

et al. 2011

Acta Geotech.

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Within shear bands in sands, deformation is largely non-affine, stemming primarily from buckling of well-known force chains and also from vortex-like structures. In the spirit of current trends toward multiscale modeling, understanding the links between these mesoscale deformational entities and corresponding macroscale response will form the basis for the next generation of sand behavioral models and may also aid in efforts to understand jamming-unjamming transitions in dense granular flows in general. Experimental methods to quantify and characterize such subscale kinematics, in particular in real sands, will play critical roles in these efforts. Digital Image Correlation (DIC) is a fast growing experimental technique to nondestructively measure surface displacements from digital images. Here, DIC has been employed to identify and characterize the development of vortex structures inside shear bands formed in dense sands during plane strain compression. A rigorous assessment of the DIC method has been performed, in particular for subscale behavioral characterization in unbonded granular solids, and guidelines are offered for accurate implementation. While DIC systematically overestimates shear band thickness, a methodology has been devised to compensate for this overestimation. Shear band thickness for four different uniform sands were found to range between 6 and 9 grain diameters, and for a well-graded sand between 8 and 9.5 grain diameters. These determinations agree with visual inspections of grain kinematics from the image data, as well as recent theoretical predictions.

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Sand Shear Band Thickness Measurements by Digital Imaging Techniques

Cited by 138 publications

References 15 publications

Influence of Particle Size on the Friction and Interfacial Shear Strength of Sands of Similar Morphology

Influence of Particle Size on the Friction and Interfacial Shear Strength of Sands of Similar Morphology

Modelling strain localization in granular materials using micropolar theory: numerical implementation and verification

Characterization of mesoscale instabilities in localized granular shear using digital image correlation

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