Permeability and swelling characteristics of bentonite

Abstract

Permeability and swelling characteristics of bentonite and bentonite-sand are the essential parameters for designing any type of waste disposal or in geo-environmental engineering applications. To design and construct these facilities accurate values of permeability for these bentonite-sand mixtures must be evaluated. For this purpose, a series of various laboratory tests were performed to investigate the coefficient of permeability using direct and indirect test methods derived from consolidation theory using liquid limit 1.5 of bentonite. Permeability tests were also carried out for dynamically compacted bentonite. Void ratio of bentonite is a key parameter of permeability for bentonite and bentonite-sand mixtures. The specimen manufacture method had no effect on permeability. A series of swelling pressure and deformation tests are performed using variable content (30 to 90%) of bentonite at initial dry density of 2 g/cm3to investigate the characteristics of buffer material for radioactive waste disposal. Content of bentonite in bentonite-sand mixture is the prime criteria of buffer material and must be taken into consideration in designing any types of waste disposal facilities. Content of bentonite and loading pressure on the specimens is noticeably influenced on maximum swelling rate. Key words: Bentonite, permeability, swelling pressure, swelling deformation.