Numerical evaluation of particle shape effect on small strain properties of granular soils

Abstract

This paper presents a numerical investigation about the effect of particle shape on small strain properties (e.g., shear stiffness and Poisson's ratio) of granular soils through 3D discrete element simulations of drained triaxial shearing tests. To this end, different mass proportions of realistic shape clumps and ideal spheres with the same grading are mixed together to prepare five types of granular samples with varying particle shape features. Four independent 3D shape descriptors including aspect ratio, sphericity, convexity and roundness are determined for constituent particles within each samples to describe their shape polydispersity characteristics from different shape scales (e.g., global form and local roundness). A well-defined and practical 3D shape parameter named particle overall regularity is adopted to collectively quantify multiscale shape differences among the five samples. Based on the simulated shape dependent small strain properties results, the applicability of two common empirical expressions to capture the confining pressure and density dependent small strain stiffness are evaluated. Correlations between model parameters of these two equations and different shape descriptors are also built. Moreover, the micromechanical quantities (e.g., mechanical coordination number and contact stiffness) are explored to unravel the underlying micro mechanisms of particle shape dependent small strain properties of granular soils.