Estimation of hydraulic anisotropy of unconsolidated granular packs using finite element methods

Abstract

The effect of particle shape and heterogeneity on hydraulic anisotropy of unconsolidated granular packs is hereby investigated. Direct simulation was carried out on synthetically generated spherical, aspherical, ellipsoidal (aspect ratio of 2 and 3) and lenticular samples. Single phase Stokes equation was solved on models discretised on finite element geometries and hydraulic permeability computed in the horizontal and vertical directions to estimate the degree of anisotropy. The spherical and aspherical packs with varying degrees of particle shapes and heterogeneities are virtually isotropic. Ellipses with aspect ratios 2 and 3 have higher anisotropy ratios compared to the spherical and aspherical geometries while the lenticular geometry is the most anisotropic. This is attributable to the preferential alignment of the grains in the horizontal flow direction during random dynamic settling under gravity.