A 3D-DEM Model for Tropical Residual Soils under Monotonic and Cyclic Loadings

10 Tropical residual soils are found in different parts of the world and consist of mixtures of different 11 types of soil such as sand, silt and clay, resulting in intricate microstructures and mechanical 12 responses. In this context and inspired by the soil’s composition, a 3D-DEM model is developed 13 in which two different contact models are assigned among idealized spherical particles to represent 14 the coarse and fine parts of the tropical soil with two distinct sets of numerical parameters. A simple 15 linear rolling resistance contact model is used to represent the coarse, cohesionless, component, 16 while a softer adhesive rolling resistance contact model with a linear approximation of the van der 17 Waals attraction force is used for the fine, cohesive, component. The numerical coarse network is 18 continuous in terms of interparticle contacts and represents the main skeleton of the DEM sample, 19 whereas so-called fine contacts form a local force network between the coarse particles. After a 20 parametric study on the effects of adopting such a numerical mixture, the model is calibrated for a 21 drained compression triaxial test with a specific void ratio. In order to estimate the equivalent DEM 22 model void ratio, a proportionality between the real soil void ratio and the DEM model void ratio 23