An Investigation of Fines and Coarse Contents in Granular Soil Mixtures by Using Discrete Element Method (DEM)

It was believed that adding fines grains to a base coarse-grained soil would result in shear strength increase due to filling up the voids among coarse content and reducing global void ratio. However, this belief was against following experiments. New variables referred to as the equivalent intergranular and interfine void ratios, have been proposed to resolve this problem. In this paper, by using Discrete Element Method, several soil samples were created by mixing two coarse- and fined-grained soils. Simulations were performed in two-dimension in which, the particles are circular. After the soil sample preparation, it was consolidated under isotropic confining pressure followed by biaxial compression loading. The loading condition was continued until the samples reached the critical state. Based on the simulated results, the required parameters to estimate the portion of coarse- and fine-grained parts in the global soil behavior, were obtained. Comparison of the results of the this study with those of experiments shows good agreements. The threshold fines content, which indicates the government of either of coarse or fine-graind parts was also derived. The two-dimensioanl simulations indicate that for each sample with a specified fine content, the corresponding critical state line can be obtained. If the definitions of equivalent intergranular and interfine void ratios are used, unique critical state lines are reachable.