Influence of the Ca substitution for mechanical characteristics of Na-type bentonite and sand mixture for long term seapage

In this paper outlines the observations made on the change in permeability when an aqueous calcium solution was left to permeate a material consisting of sodium bentonite mixed with different quantities of sand over a set period of time. The Ca substituted test specimen was then subjected to a triaxial compression test to determine the effects of Ca substitution on shear strength. An increase in permeability was observed as sodium ions were discharged from the sodium bentonite specimen when the aqueous calcium solution was left to permeate over a set period of time. Results of the quantitative analysis of the Ca substituted test specimen performed after the mechanics test indicated that the Ca substitution ratio was between 75 and 98%, with Ca substitution being confirmed. Results of a triaxial compression test to determine shear strength indicated that the Ca substituted bentonite sand mixture specimen with different quantities of sand displayed a higher shear strength than that of the sodium substituted specimen. (author)