Viscosity and dielectric constant controls on the hydraulic conductivity of clayey soils permeated with water-soluble organics

Abstract

Water-soluble organic liquids may, under some circumstances, dramatically increase the hydraulic conductivity, k, of water-saturated clayey soils, thus destroying their effectiveness as barriers for contaminants. Double-layer contraction at constant void ratio with resultant increases in the pore space available for flow has been identified as a primary mechanism for such increases in k. This paper shows, however, that the increased viscosity of solutions of some organics in water results in significant decreases in k.Pure alcohols (ethanol and methanol) and other water solubles (dioxane) when permeated through water-compacted clay samples produce an initial decrease in k, followed by a gradual increase to equilibrium values. The "hydrocarbon" front raises the viscosity of the pore fluid and causes an initial drop in k. Tests using aqueous solutions of ethanol and dioxane show decreases in k at concentrations up to ~70%. Only at high concentrations does the dielectric constant, double-layer effect overcome the viscosity effect and produce net increases in k.Effective stresses σ′vof 160 kPa during permeation with ethanol and dioxane prevent the increases in k. Physicochemically induced consolidation and increased K0-shearing effects that close shrinkage cracks are operative. Key words: hydraulic conductivity, liquid hydrocarbons, clay, viscosity, dielectric constant.

Hydraulic Conductivity of Nonprehydrated Geosynthetic Clay Liners Permeated with Inorganic Solutions and Waste Leachates

“…Nonpolar ‰uids or polar ‰uids having low dielectric constants such as alcohols are also a factor to increase the hydraulic conductivity of clay liners (Shackelford et al, 2000). However, no signiˆcant increase in the hydraulic conductivity occurs when the concentration of organic chemical compounds is lower than 50z, because the dilution with water increases the dielectric constant (Mesri and Olson, 1971;Bowders and Daniel, 1987;Fernandez and Quigley, 1988;Shackelford, 1994). In addition, an increase in the hydraulic conductivity by the permeation of electrolytic solutions is of great concern to use GCLs in the sea areas or waste containment facilities.…”

“…Thisˆgure indicates the relation between the free swell of the bentonite and the ionic strength of the chemical solutions.``Na(X) : K(Y)'' shown in thisˆgure means the mixing of volumetric ratio NaCl solution and KCl solution. For example,``Na(2) : K(8)'' indicates that NaCl solution and KCl solution were mixed under the volumetric ratio NaCl : KCl＝2 : 8. The open plots show the free swell for the deionized water and the single-species solution, and in contrast, the closed plots show the free swell for the multi-species solution.…”

The Influence of the Dielectric Constant and Electrolyte Concentration of the Pore Fluids on the Undrained Shear Strength of Smectite

“…These play an important role for the engineering response of the material. Numerous authors have already dealt with and analyzed the problem (e.g., Mesri and Olson, 1970;Mesri and Olson, 1971;Olson, 1970;Fernandez and Quigley, 1988;Di Maio, 1996; Fang, 2000, Anandarajah andZhao, 2000;Sridharan, 2002). The in‰uence of the dielectric constant and the electrolyte concentration of pore ‰uids plays an important role, particularly in the case of 2:1 expanding clays such as smectite.…”

Chemically induced deformation of a porous layer coupled with advective–dispersive transport. Analytical solutions

“…Experimental studies of hydraulic conductivity of clays exposed to di!erent permeants show that the transport of chemicals and the resultant interaction of the chemical with solid skeleton may cause chemically driven deformation of the material [22]. In order to illustrate the application of the proposed model for clayey soils the advective}dispersive transport of dioxane and chemically induced deformation in a layer of Sarnia clay are considered.…”

“…In order to illustrate the application of the proposed model for clayey soils the advective}dispersive transport of dioxane and chemically induced deformation in a layer of Sarnia clay are considered. The set of parameters characterizing the materials was identi"ed based on experimental data from the constant #ow rate permeability test as described in the paper by Fernandez and Quigley [22], see Table I. The thickness of the layer in the considered example is equal to 1 m, the concentration at the upper boundary amounts 0.2 kg/dm and the pore pressures at the upper and lower boundaries are kept constant and equal to 100 and 0 kPa, respectively.…”