(206c) Effect of Mechanical Interlocking on Particle-Phase Stress in Sheared Granular Flows

In order to obtain reliable predictions for the flow behavior of highly angular particles, such as Lunar and Martian soils, mechanical interlocking associated with sustained particle-particle interactions needs to be described. Mechanical interlocking gives rise to large particle-phase stress in granular soils and a significant resistance to deformation. In this study, the effect of particle interlocking in dilute and dense-phase granular flows is investigated via discrete element method (DEM) simulation of a 3D system of ‘C’-shaped particles in simple shear flow using Lees-Edwards periodic boundary conditions. The effect of particle shape is assessed by progressively varying the degree of curvature of these ‘C’-shaped particles. The particle shape varied from a straight, elongated particle to one in which the straight particle is folded in half. For each particle shape, a total normalized interlocking time and distribution of particle interlocks are determined over a range of solid concentrations. At low solid volume fractions, the normal and shear stresses are proportional to the inverse of the projected area of the particle in the plane perpendicular to the flow, consistent with the stress behavior of elongated particles [1]. For larger solid volume fractions, normal and shear stresses increase with increasing interlocking, showing a direct dependence between stress and degree of mechanical interlocking.

[1] Y. Guo, C. Wassgren, W. Ketterhagen, B. Hancock, B. James and J. Curtis, “A Numerical Study of Granular Shear Flows of Rod-like Particles Using the Discrete Element Method”, Journal of Fluid Mechanics, 713, 1-26 (2012)