A Study on Compressibility, Swelling and Permeability Behaviour of Bentonite-Sand Mixture

In geotechnical engineering field, bentonite-sand mixtures have been proposed and used as engineered barriers for containing the waste. This paper presents the laboratory evaluation of compressibility by performing one-dimensional consolidation tests on six different mixtures of bentonite with sand. The bentonite-sand mixtures were formed by varying sand content in bentonite in increments of 5% from 5 to 25% by dry weight. Dry bentonite-sand mixtures were placed initially in the consolidation cell at their loosest dry state and then allowed to saturate. Swelling characteristics and swelling pressures of the bentonite-sand mixtures were also evaluated. This paper also presents the laboratory evaluation of permeability of the bentonite-sand mixtures by performing falling head test after every load increment during the consolidation test. This study arrived at the conclusion that amount of swelling (expressed in percentage) and swelling pressure decreased with addition of sand. Moreover, changes were observed for the consolidation parameters upon addition of sand to bentonite. The void ratio versus log of permeability plots was found to be linear, and permeability was found to increase with increase in sand content.