Shearing Strengths of Kaolinite, Illite, and Montmorillonite

Abstract

During the years 1957-1970, over 400 S and R triaxial compression tests were performed using sedimented, slurried, or remolded specimens of kaolinite, illite, and montmorillonite, prepared with several adsorbed cations and ranges in pore-water electrolyte concentration and pH, to study the relative effects of physicochemical variables on the shearing properties. The strengths were found to be controlled mainly by physical effects related to the size and shape of individual particles. Diffuse double-layer forces were never found to be significant for calcium clays. They were also insignificant for sodium kaolinite but were effective in reducing the strength of sodium illite, and caused major loss in strength for sodium montmorillonite by causing a great decrease in particle thickness thus leading to highly flexible particles of low physical strength.