Development of a saturation-based Mu(I)-rheology for wet granular materials using discrete element method

The discrete element method (DEM) is used to establish a rheological model that relates the apparent viscosity of a granular material to shear rate, normal stress, and water saturation. A theoretical model is developed to determine water distribution and water-induced forces between particles for different saturations. The resulting forces are embedded in a 3D shear cell as a numerical rheometer and a wet specimen is sheared between two walls. A power law rheological model is obtained as a function of inertia number and saturation. It was found that up to a critical saturation, the apparent viscosity increases with saturation and is higher than that of the dry specimen. However, when the saturation exceeds a critical value, the viscosity suddenly drops below that of dry condition. To evaluate the model, the collapse of two-dimensional granular material on a horizontal rigid bed is studied using continuum-based numerical simulation which utilizes the proposed rheological model.