Tropical residual soils are found in different parts of the world and consist of mixtures of different types of soil such as sand, silt and clay, resulting in intricate microstructures and mechanical responses. In this context and inspired by the soil's composition, a 3D-DEM model is developed in which two different contact models are assigned among idealized spherical particles to represent the coarse and fine parts of the tropical soil with two distinct sets of numerical parameters. A simple linear rolling resistance contact model is used to represent the coarse, cohesionless, component,