Consolidation Characteristics of Montmorillonite

Abstract

Synopsis Artificially sedimented specimens of Wyoming bentonite (Volclay) were used to investigate the effect of physico-chemical variables on the consolidation properties of montmorillonite. One-dimensional consolidation tests were performed on calcium and sodium montmorillonite at various electrolyte concentrations. The influence of pH and organic pore fluids on the consolidation properties of montmorillonite was also investigated. The consolidation curves of calcium montmorillonite were essentially independent of both the electrolyte concentration in the free pore water and the pH of the suspension from which the specimens were sedimented. The influence of pore water electrolyte concentration on the swelling curves of calcium montmorillonite was much smaller than would be predicted from the Gouy-Chapman double layer theory. The consolidation and swelling curves of sodium montmorillonite were affected by the concentration of electrolyte in free pore water and there was reasonable agreement between the measured swelling curves and the double layer theory. Consolidation tests in which organic pore fluids were used demonstrated that swelling of montmorillonite is caused by either adsorption of the pore fluid or formation of diffuse double layers. The coefficient of permeability of the sodium montmorillonite in water was as low as 2 × 10−l2 cm/s. The coefficients of permeability were higher for the montmorillonite in ethanol than in water, and considerably higher values were obtained when the pore fluid was non-polar, all compared at the same void ratio. On a utilisé des échantillons artificiellement sédimentés de bentonite du Wyoming (Volclay) pour étudier l'effet des variables physico-chimiques sur les propriétés de consolidation de la montmorillonite. On a fait des essais de consolidation unidimensionnelle sur les formes calcium et sodium de la montmorillonite à diverses concentrations d'électrolyte. On a également étudié l'influence du pH et des liquides de pore organiques sur les propriétés de consolidation de la montmorillonite. Les courbes de consolidation de la forme calcium de la montmorillonite sont essentiellement indépendantes de la concentration d'électrolyte dans l'eau libre des pores et du pH de la suspension à partir de laquelle on a fait sédimenter les échantillons. L'influence de la concentration en électrolyte dans l'eau des pores sur les courbes de gonflement de la forme calcium de la montmorillonite est beaucoup plus faible que ne permet de le prévoir la théorie de la double couche de Gouy–Chapman. Les courbes de consolidation et de gonflement de la forme sodium de la montmorillonite sont influencées par la concentration en électrolyte dans l'eau libre des pores et il y a un assez bon accord entre les courbes de gonflement mesurées et la théorie de la double couche. Des essais de consolidation effectués en utilisant des liquides de pore organiques ont démontré que le gonflement de la montmorillonite est dû soit à l'adsorption du liquide de pore, soit à la formation de doubles couches diffuses. Le coefficient de perméabilité de la forme sodium de la montmorillonite est aussi bas que 2 × 10−12 cm/s. Les coefficients de perméabilité sont plus élevés pour le systéme montmorillonite éthanol que pour le système montmorillonite eau, et on a obtenu des valeurs considérablement plus élevées lorsque le liquide de pore était non-polaire, toutes ces mesures étant ramenkes à la même fraction de vide.

Effect of thermal history on the properties of bentonite

“…However, the DDL is formed on the external surface of clay particles and the volume of attracted shown that the volume change in clays due to water-cations interaction can be predicated based on Guy-Chapman theory (Mitchell, 1993). A number of important contributions have been made to better understand the influence of DDL on clay behaviour (Olson and Mesri, 1970;Olson, 1971 andRao, 1973). Moreover, intensive research has focuced on computing the swelling pressure by employing the Guy-Chapman DDL theory (Pusch et al 1990;Komine and Ogata, 1996and Sridharan and Choudhury, 2002.…”

An experimental and constitutive investigation on the chemo-mechanical behaviour of a clay

“…Various authors use different terminology for these phenomena: Barbour & Fredlund (1989) mention osmotic consolidation and osmotically induced consolidation, whereas Kaczmarek & Hueckel (1998) discuss chemical consolidation and chemico-osmotic consolidation. Barbour & Fredlund (1989) interpreted the results of a series of four experiments conducted by Mesri & Olson (1971), and presented additional experimental results on two different types of soil to quantify 'osmotic compressibility and permeability'. The main conclusion of their work was that the dominant mechanism of volume change was osmotic consolidation, referred to as chemical consolidation here.…”

“…In the 1970s and 1980s, chemically induced consolidation, permeability and shear strength variations, and osmosis and osmotic effects were extensively studied (e.g. Mesri & Olson, 1970, 1971Mitchell et al, 1973;Sridharan & Venkatappa Rao, 1973, 1979Marine & Fritz, 1981;Fritz, 1986;Barbour & Fredlund, 1989). The late 1990s and 2000s brought forth coupled chemo-mechanical models, in which the concentration or mass fraction of certain species in the pore liquid played a major role (e.g.…”

An Analysis of the Factors Affecting the Hydraulic Conductivity and Swelling Pressure of Kyungju Ca-Bentonite for Use as a Clay-Based Sealing Material for a High-Level Waste Repository

“…The increase of the salinity might increase the hydraulic conductivity in the buffer and backfill and enhance the water movement through the buffer and backfill. Several researchers [26][27][28] have reported that a dramatic increase in hydraulic conductivity may occur when a concentrated salt solution is introduced into a clay. Castellanos et al [29] reported that the hydraulic conductivity of a highly compacted saturated FEBEX bentonite increases when high-salinity permeants are used, especially for low densities.…”

“…A reduction in the double layer thickness may result in changes in the net repulsive forces between the sheet of montmorillonite particles, which is the major mineral of bentonite [28,33,34]. The decrease of the net repulsive force in turn decreases the tendency of the sheet to separate.…”