A Micromechanics Model for Solute Diffusion Coefficient in Unsaturated Granular Materials

Abstract

International audienceA new micromechanics analysis of solute diffusion in unsaturated granular materials is put forward. This permits predicting the percolation effect. To do so, the pore water is divided up into four phases that account for the different spatial distributions and diffusion properties: interconnected capillary water, isolated capillary water, wetting layer and water film. A parameter denoted as connectivity ratio is introduced to account for the connectivity of the capillary pore water. Our model agrees well with experimental results on unsaturated sands and glass beads from literature. It also permits interpreting the physical meaning of the saturation exponent of Archie’s law: The latter is found to be correlated with the connectivity ratio of the unsaturated granular materials

Pore-scale velocities in three-dimensional porous materials with trapped immiscible fluid

“…Understanding and quantifying the impact of pore-scale flow heterogeneity on the observed behavior of fluid flow and transport at the continuum (Darcy) scale is key to the assessment of anomalous features documented in natural and engineered media under saturated [1][2][3][4][5][6][7][8] and unsaturated conditions [9][10][11][12][13][14]. Knowledge of the probability distribution of pore-scale velocities has been demonstrated to be critical in determining dispersion mechanisms in porous media [15] and is a major element which allows advancing our ability to characterize fluid flow processes in porous media.…”

Computation of Saturation Dependence of Effective Diffusion Coefficient in Unsaturated Argillite Micro-fracture by Lattice Boltzmann Method

“…Another limitation of the presented results consists in the impossibility for the lattice Boltzmann model to take into account water-films thinner than one voxel (0.35mm for the finest lattice used in this study). A difference between the effective diffusion coefficient calculated with our model and the real one is then maybe of concern for low saturations (Yang et al, 2016).…”

“…Note that m (the "cementation exponent" linked to porosity) and n (the "saturation exponent") are found to vary from 1 to 3 in literature with an average value around 2 for real porous media (See Hamamoto et al (2010) for a review). It is to mention that theoretical works on effective diffusion dependence on saturation are still currently of interest (Ghanbarian et al, 2015;Yang et al, 2016).…”

Self-Consistent Channel Approach for Upscaling Chloride Diffusivity in Cement Pastes

“…Another interesting extension of the present model could relate to the case of unsaturated pores. This could be done based on the very interesting recent suggestion (Yang et al 2016) of covering an Eshelby inclusion representing the solid phase by a liquid layer. This extension should be readily applicable to the Eshelby problem of Fig.…”