Double layer theory and compressibility of clays

Abstract

The compressibility of pure clays under external load depends not only on the negative charges and crystallite morphology of clay minerals but also on the ion concentration, cation valency, dielectric constant and temperature of the pore fluid. The electrical double layer theory has been used by several investigators to derive the void ratio-pressure relationship of clays. This Paper presents a detailed study with regard to the Gouy—Chapman theory and the compressibility of clays. The relationship between the distance between parallel clay platelets and external pressure is shown to be almost independent of clay type. The surface area represents the clay type in showing the variations in void ratio-pressure (e–p) relationships of different clays. When the concentration of cations in the pore fluid is low, the log e–log p relationship is linear, and the compression index is a direct function of void ratio and independent of clay type. Examination of experimental results of other workers shows the validity of the Gouy—Chapman theory for predicting the e–p relationship qualitatively and, under certain circumstances, quantitatively. La compressibilité des argiles pures sous charge extérieure dépend non seulement des propriétés mécaniques des minéraux d'argile mais aussi des caractéristiques physicochimiques du fluide interstitiel. La théorie électrique des couches doubles a été employée par plusieurs rechercheurs pour représenter le rapport indice des vides/pression des argiles. Cet article offre une étude détaillée de la théorie Gouy-Chapman appliquée à la compressibilité des argiles. Le rapport entre la distance séparant les feuillets parallèles de l'argile et la pression extérieure est presque indépendant du type de sol. La zone superficielle représente le type d'argile, car elle indique les variations du rapport indice des vides/pressions des différentes argiles. Lorsque la concentration des cations dans le fluide interstitiel est basse le rapport log e/log p est linéaire et l'indice de compression est une fonction directe de l'indice des vides. Le dépouillement des résultats expérimentaux démontre que la théorie Gouy-Chapman est valable pour prédire le rapport e/p qualitativement et aussi quantitativement dans certaines circonstances.

Hydraulic conductivity and compressibility characteristics of bentonite enriched soils as a barrier material for landfills

“…The interaction between soil particles such as crushing, rolling, sliding past each other, based on the physical properties of the mineral particles controls the mechanical effect of the compressibility of bentonite. Whereas, the physico-chemical interactions between particles include the interaction between the particles through the diffuse double layers [25,31,32]. According to Robinson and Allam [30] both increasing and decreasing trends are observed in C v values for soils of unknown clay mineralogy.…”

Recent Developments in Nanomaterials for Geotechnical and Geoenvironmental Engineering

“…The nanoalumina was purchased from Inframat Advanced Materials, Manchester, CT, USA. It has a chemical formula Al 2 O 3 , particle density of 3.6 g/cm 3 , surface area of > 150 m 2 /g, and a transitional gamma crystal structure [19]. For high plasticity soils (given as S3 and S4 with plasticity index of 18 and 69, respectively), the CIF is minimum at 0.1 % nano-alumina content (Fig.…”

“…Since then these swelling pressure equations ( Fig. 1) has been also used by a number of other researchers, notably by Sridharan & Jayadeva [3], Komine & Ogata [4] & [5], Tripathy et al [6], Tripathy & Schanz [7], and Gurtug [8] to study clay behavior.…”

Swelling pressure of sodium montmorillonites

“…Sridharan & Jaydeva (1982) suggested an equation, the same as equation (6) in the paper, to compute the u values for any given Kd values. Equation (6) is valid for all pure clays (kaolinite, illite and montmorillonite).…”

“…The discussers would also like to point out that double layer repulsion depends strongly upon dielectric constant, cation valency, and cation concentration (Sridharan & Jaydeva, 1982). For a given pore-fluid medium, the effect of the increase in valency is to suppress the diffuse double layer (Mitchell, 1993), and hence the swelling pressure will decrease.…”