Chemical potential of a two-component liquid in porous media: The case of unsaturated soil

• Published in: Geomechanics for energy and the environment 2017-03, Vol.9, p.36-45
• Main Authors: Bénet, J.C., Jamin, F., El Youssoufi, M.S.
• Format: Article
• Language: English
• Subjects: Chemical and Process Engineering; Chemical potential; Civil Engineering; Engineering Sciences; Géotechnique; Porous media; Reactive fluid environment; Soil water retention curve; Unsaturated soil
• ISSN: 2352-3808; 2352-3808
• DOI: 10.1016/j.gete.2016.09.001

The aim of this paper is to propose a method to determine the chemical potential of two miscible components of a solution in porous media, particularly in the case of an unsaturated soil. It is limited to the capillary state; the equilibrium of the liquid phase in the soil is determined by gas–liquid interfaces whose geometry obeys Laplace’s law. Deduction of the chemical potential of the two components from the chemical potential of pure water is based on the assumption that, for the same volume occupied by the fluid phase in the porous medium, the geometry of the fluid phase is independent of the composition of the solution. The expressions of the chemical potentials of the two components were established. They show the superposition of two effects: the effect of interfacial forces and the effect of the presence of the other component. A study of the water–alcohol solution in a clayey silty sand soil was then conducted to alcohol mole fractions between 0 and 0.15 and water content in the 5%–15% range. In this field, the chemical potential of the water was seen to be affected by the capillary effects below a water content of 10%. Above that, its variation as a function of the mole fraction of alcohol differed little from that of the potential of the water in a free solution. The chemical potential of the alcohol was little affected by the capillary effects. •Chemical potential expressions of the components for a binary liquid solution in soils.•Crossed effects of every component and the liquid–gas interfaces on the chemical potential of components.•Determination of the chemical potential from the properties of every component and the relation suction-pure water content.•Case study in the capillary domain for a water–alcohol solution in a clayey-silty sand.