Influence of Fabric on Stress Distribution in Gap-Graded Soil

The combined influence of density and stress-induced fabric anisotropy on the nature of stress transmission in gap-graded soils with cohesionless fines has been explored using the discrete element method (DEM). Various particle size ratios and fines contents were considered in simulations of constant mean stress triaxial compression. Analysis of the available particle-scale data focused on understanding how stress was distributed among and between the finer and coarser particles. While the study confirms that stress is transferred from the coarser to the finer fraction with increasing fines content, the concept of a threshold fines content at which there is a definitive transition in the nature of stress transmission is not supported. Rather, there is a gradual evolution of the distribution of stresses between the two size fractions with increasing fines content, and the relationship between fines content and stress in the finer fraction depends on the size ratio, density, and fabric anisotropy. For the denser samples considered, the stress transmitted by the finer fraction systematically reduced during shearing. An alternate definition of granular void ratio is introduced, which accounts for the nonactive fine and coarse particles and is formulated in a consistent manner to capture both the intergranular and interfine void ratios commonly found in the literature, along with the equivalent granular void ratio. The anisotropy of the network of contacts formed by the interactions of coarse particles was observed to be the dominant contributor to fabric anisotropy.