Hierarchical multiscale modeling of fluid-saturated soils

Abstract

This paper presents an extension of a hierarchical multiscale computational method previously developed by the authors to model the behavior of fluid-saturated soils. The original hierarchical multiscale framework is based on rigorous coupling between the finite element method (FEM) and the discrete element method (DEM). It helps to bypass the phenomenological constitutive model in the conventional FEM modeling, and meanwhile faithfully reproduces the typical soil behaviors by DEM simulations at the Gauss points of the FEM mesh which naturally offers great convenience for cross-scale analysis. The current study features a key extension of the framework to further consider the coupled hydro-mechanical behavior in saturated soils based on the u-p formulation. It enables us to take into account the effects of pore fluid pressure and pore fluid flow on the mechanical responses of soil, while retaining reasonable computational efficiency. The approach is first benchmarked by a classic 1D consolidation problem, where the numerical predictions are compared against the closed-form solution. It is further applied to the simulation of a globally undrained biaxial compression test on a dense soil. The interplay between the fluid flow and the strain localization observed in the sample is discussed.