Micromechanics of compressive and tensile forces in partially-bonded granular materials

Abstract

In granular media, the presence of even small amounts of interparticle cohesion manifests as an increase in the bulk strength and stiffness, effects that are typically associated with an increase in the average number of constraints per particle. By performing an ensemble of isotropic compression experiments, all starting from the same initial particle configuration but with varying fraction of bonded particles, we use photoelastic force measurements to identify the causes of this phenomenon at the particle-scale and meso-scale. As a function of the percentage of bonded particles, we measure a small decrease in the critical packing fraction at which jamming occurs. Above jamming, the local pressure increases predominantly for the bonded particles, measured relative to the unbonded case, through approximately equal contributions of both tensile and compressive forces. Histograms of the magnitude of the interparticle forces become broader for systems with more bonded particles. We measure both pressure and coordination number as a function of distance from a bonded dimer, both of which are locally enhanced for nearest neighbors, indicating that dimers appear to act as areas of concentrated force and connectivity that improve rigidity.

6 pages, 4 figures, 4 pages supplementary material, 4 figures

References in corpus (6)

• Soft Sphere Packings at Finite Pressure but Unstable to Shear
• The physics of cement cohesion
• Creating bulk ultrastable glasses by random particle bonding
• Elasticity-Controlled Jamming Criticality in Soft Composite Solids
• Criticality enhances the reinforcement of disordered networks by rigid inclusions
• Extracting Contact Forces in Cohesive Granular Ensembles