SALINITY EFFECT ON SWELLING CHARACTERISTICS OF COMPACTED BENTONITE

Swelling characteristics of compacted bentonite is the most important factor for nuclear waste disposal facilities. Salinity effect on swelling behaviour of compacted bentonite was investigated experimentally. A series of one dimensional swelling deformation tests have been performed. The tests were conducted for various initial dry densities from 1.33 g/cm(3) to 1.90 g/cm(3) for compacted bentonite saturated with NaCl of various concentrations in solution from 0 to 4.0 M. It Was found that initial dry density and concentration of NaCl strongly influence the swelling rate of bentonite. The swelling rate of bentonite decreases with increasing the concentration of NaCl. Swelling rate depends on the concentration of NaCl more than on initial dry density and loading effect. Bentonite may change from highly swelled material to coagulate in saline water. Liquid limit of bentonite is also remarkably decreased with the change of liquid from distilled water to saline one, while the plastic limit is slightly increased.