Role of interparticle forces and interparticle friction on the bulk friction in charged granular media subjected to shearing

Abstract

We study the consequences of the interplay between electrostatic forces, mechanical contact forces, and frictional properties of grains upon the bulk frictional properties of charged granular media subjected to quasistatic shearing. We show that, the variations in short-range electrostatic forces between the grains (which are often ignored in the existing studies) dominantly affect the bulk friction. Charging enhances the fabric anisotropy of heavily loaded contacts--this enhances the bulk friction, more significantly, in the case of low frictional granular systems.

Micro-macro correlations and anisotropy in granular assemblies under uniaxial loading and unloading

“…In comparison, the structural anisotropy is much smaller than the deviatoric stress ratio. The decrease in the maximal structural anisotropy is in disagreement with observations reported for triaxial tests [8,48], where it is observed to increase with increasing friction. One main reason is that under triaxial loading, the coordination number decreases with increasing strain (dilatancy), but it increases under uniaxial loading (due to ongoing compaction) while in both cases fabric anisotropy is induced by shearing.…”

“…In comparison to other deformation protocols studied in literature, while the coordination number is found to decrease with increasing triaxial loading (or increasing deviatoric strain) [8,57], we find that the coordination number always increases with strain under uniaxial compression. Under triaxial loading, the number of contacts is found to increase in the vertical (compression) direction while decreasing or dilating in the horizontal (fixed stress) direction [48], but in the uniaxial mode, the number of contacts is found to increase in both the horizontal and vertical directions.…”

“…Under triaxial loading, the number of contacts is found to increase in the vertical (compression) direction while decreasing or dilating in the horizontal (fixed stress) direction [48], but in the uniaxial mode, the number of contacts is found to increase in both the horizontal and vertical directions. Also, the peak deviatoric fabric is found to increase with increasing friction under triaxial loading [8,57], whereas in the uniaxial mode, the peak deviatoric fabric decreases with increasing friction.…”

“…In addition, the effects of contact friction between the constituent grains influence the micromechanical response under uniaxial loading, such that a rather simple element test begins to reveal interesting features. Several studies have numerically investigated the extent to which the response of granular media is affected by friction [6][7][8][9][10], especially in the triaxial geometry, but not many studies exist on uniaxial loading and unloading of frictional systems [11].…”

Interplay between the inclusions of different sizes and their proximity to the wall boundaries on the nature of their stress distribution within the inclusions inside particulate packing

“…The link between the signature (structural alignment) of the force network and bulk mechanical properties of granular systems is quite significant [14]. For example, studies have attributed the microscopic origin of the bulk shear strength of granular materials, to the fabric alignment of the strong-force transmitting contacts under different external loading conditions [5,15,16]. Strong contacts account for a small proportion (about 25-30%) of all the contacts [2][3][4][5].…”