Swelling Pressure of Montmorillonite

Abstract

A montmorillonite suspension was placed in a miniature compression chamber bounded on one side by a cellulose membrane supported by a water saturated porous Alundum disk, and on the other by a rubber film. Changing the ambient pressure on the film caused water to move across the membrane until the swelling pressure of the suspension equalled the applied pressure. Existing theory, based upon the Gouy‐Chapman description of the diffuse double layer and upon its anticipated osmotic activity, was used to predict swelling pressures for different suspensions. During initial compression, measured swelling pressures of both Na‐ and Ca‐montmorillonite exceeded predicted values. Subsequent decompression and recompression cycles were reversible except for a slight but measurable hysteresis, but the position of the reversible portion of the curve depended upon the terminal pressure of the initial compression. When the latter was large (25 to 50 atm.), measured swelling pressures of decompression‐recompression cycles for Na‐montmorillonite agreed quantitatively with theory over the range 0.2 to 50 atm. Under similar conditions, Ca‐montmorillonite exhibited pressures appreciably less than predicted by theory.

Susceptibility of Undisturbed Soils to Compression as Evaluated from the Changes in the Soil Water Characteristic Curves

“…Thus, paying attention to the alteration of the pore size characteristics, we may define the compression susceptibility X of a saturated soil as follows: (4) We can expect that the value of X ranges from 0 for very rigid, incompressible soils to 1 for fully saturated compressible soils with no skeletal structure. An example of the latter case can be seen in the swelling pressure measurements (17) where it is tacitly assumed that the applied pressure is counterbalanced exclusively by the development of the overburden water pressure, and that at equilibrium its magnitude is equal to that of the swelling pressure of the system due to interparticle repulsive forces. If X is extended by substituting Up for Up!, thus relaxing the condition that u=O, it becomes identical with the load factor a introduced by CRONEY and CoLEMAN (2) and further analyzed by several workers (7,14,15).…”

Changes in Sediment Volume, Liquid Limit, and Plastic Limit of Alluvial Soils upon Drying

“…EMERSON (16) estimated the degree of drying which is necessary for the aggregation of clay crystals into domains. This was assumed to correspond to about pF 4.2 for calcium montmoriIlonite and pF 4.5 for London clay, based on data on the swelling pressure of the former (17) and suction-water content relationship of the latter (18), respectively. Furthermore, according to NORRISH (19), the transition from stepwise swelling to osmotic swelling occurred in a 0.3 M sodium chloride solution for sodium montmorillonite.…”

Boron Adsorption by Clay Minerals Using a Phenomenological Equation

“…However, the maximum boron adsorption for Na-montmorillonite (6.02 • 10 -6 mole/g, is much lower than that for Ca-montmorillonite (1.18 • 10 -5 mole/g) and Ca-illite (1.51 • 10 ~ mole/g). Particles of Na-montmorillonite exist in suspension as single platelets (Shainberg and Otoh, 1968;Warkentin et al, 1957), and the distance between the separate platelets is determined by the diffuse double-layer forces. Conversely, Ca-montmorillonite exists in tactoids consisting of several platelets each (Blackmore and Miller, 1961;Norrish and Quirk, 1954), and a similar structure exists for illite.…”