A coupled, two-phase fluid-sediment material model and mixture theory implemented using the material point method

Abstract

A thermodynamically consistent constitutive model for fluid-saturated sediments, spanning dense to dilute regimes is developed from the integral form of the basic balance laws for two-phase mixtures. This model is formulated to capture the (i) viscous inertial rheology of wet grains under steady shear, (ii) the critical state behavior of granular materials under shear, (iii) the viscous thickening of fluid due to the presence of suspended grains, and (iv) the Darcy-like drag interaction for both dense and dilute mixtures. The full constitutive model is combined with the basic equations of motion for each mixture phase and implemented in the material point method (MPM) to accurately model the coupled dynamics of the combined system. Qualitative results show the breadth of problems, which this model can address. Quantitative results demonstrate the accuracy of this model as compared with analytical models and experimental observations.