The effects of gas permeation on the hydraulic permeability of
bentonite/sand mixtures were studied experimentally by conducting
permeability tests with various fluids and by microscopic observations. In
these tests, hydraulic permeabilities were measured before and after helium
gas was applied to permeate the mixtures.
Although gas formed preferential migration paths through the mixtures, the
imperviousness of the bentonite/sand mixtures to the tested fluids never
deteriorated because the paths became filled by swelling bentonite on
re-saturation.