Grading-Dependent Behavior of Granular Materials: From Discrete to Continuous Modeling

The aim of this paper is to investigate the effect of soil grading on the stress-strain and the critical-state behavior of granular materials from idealized spheres to natural soils as well as from discrete to continuous modeling. The three-dimensional discrete-element method has been applied to study the mechanical behavior of idealized granular materials. The results confirm that the critical-state line (CSL) shifts downward as grading broadens with an increase of the coefficient of uniformity C-u. An exponential relationship between the critical-state parameters and the coefficient of uniformity C-u can then be established. Furthermore, experimental investigations on an artificial material (glass beads) and a natural material (Hostun sand) were carried out. The experimental results confirm the grading dependency of the critical-state behavior, and a similar relationship between CSL and C-u, for both glass beads and natural sand, extending previous literature results for high C-u values up to 20. Moreover, the experimental results show that the CSL tends to stabilize when the coefficient of uniformity C-u becomes higher than 10. Based on all test results, a simple elastoplastic model accounting for the influence of the grain size distribution (GSD) on the mechanical behavior of granular materials has been developed within the framework of critical-state soil mechanics. Comparisons between experimental results and simulations show that the model can accurately reproduce the mechanical behavior of granular materials with different GSDs. (C) 2014 American Society of Civil Engineers.