Mechanical Failure of Grains in Sheared Granular Media: Effect of Size Ratio

Abstract

Recent studies have shown that, when the size ratio of grains (ratio of size of a grain normalised to the average size of surrounding grains) exceed about five, the stress state of the grains is dominantly hydrostatic (fluid‐like) in dense granular packing subjected to shearing. This behaviour explains the reason for the retardation tendency of breakage of large particles observed in sheared dense granular media. However, most of the engineering applications dealing with sheared random particulate media, for example mixing of detergent grains, often involve particles having size ratio less than five and information on the nature of stress experienced by grains in such scenario remains unknown, an aspect addressed in the present work using Distinct Element Method (DEM) simulations. Our stress map of particles precisely defines the stress transition:‐for particles with size ratio greater than ∼3, the stress state is dominantly hydrostatic; and between ∼1.66 and 3, the stress state gradually transit form from hydrostatic to deviatoric. For size ratio less than 1, the particles experience fluctuating stress state from zero stress to dominantly deviatoric stress state depending on whether they form part of force network or not under shearing.