The role of fines content and particle size ratio on the load-bearing structure of binary granular soil: A micromechanical approach

Abstract

The particle size ratio and fines content are the most important factors influencing the behavior of binary graded granular soil. Previous studies have focused more on the effects of the fabric, particle size distribution and fines content on the macroscopic response of binary mixtures. The effect of the fines participation factor (β) on the load-bearing structure of binary graded soil and estimation of this parameter (β) from the macro and micromechanical perspectives have rarely been evaluated. The present study used a micro-mechanical approach and DEM to evaluate the global void ratio (e), intergranular void ratio (e*) and the contribution of the fines content to the load-bearing structure of binary graded soil during drained and undrained tests. The effects of the particle size ratio, fines content, initial packing density and confining pressure on β also have been evaluated. The results showed that e* is a more reliable parameter than e for interpreting the behavior of binary graded soil. In a binary graded mixture that contains coarse and fine grains, β increased non-linearly and lower values of β were obtained for denser samples. With an increase in the particle size ratio, the values of β and microscopic parameters such as the coarse-fine (C-F) particle contact decreased. The decrease in the C-F particle contact caused a decrease in β. An equation is proposed to estimate β based on the fines content and particle size ratio of the binary mixtures.