Shear Strength of Clays and Clayey Soils: the Influence of Pore Fluid Composition
This paper reports experimental results relative to the influence of pore fluid composition on the peak shear strength of the Bisaccia clay and on the residual shear strength of several different clayey soils: the Ponza bentonite, commercial bentonite and kaolin, Bisaccia, Gela and Marino clays. Triaxial tests were carried out on the Bisaccia clay reconstituted with distilled water and with a 1 M NaCl solution. Direct shear and ring shear tests were carried out on dry materials and on the materials reconstituted with distilled water, NaCl solutions at various concentrations, cyclohexane. Some tests were carried out by using KCl solutions, ethanol and ethylene glycol. The results show that pore fluid composition influences greatly both the peak and residual shear strength of smectitic soils, even when the clay fraction is very low. The residual friction angle is about 5° in distilled water, 15° in concentrated NaCl solution, and varies between 30° and 35° for materials dry or prepared with cyclohexane. The residual friction angle is strongly correlated to the static dielectric constant of the pore fluid.
KeywordsShear Strength Void Ratio Triaxial Test Pore Fluid Clayey Soil
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