Air conductivity of a heavily compacted swelling clay-sand mixture

摘要

In this paper, we present some air permeability results obtained by running air flow tests with relative humidity (or suction) control using salt solutions. A mixture clay (bentonite) (70 percent)-sand (30 percent) is used. Samples are compacted ata water content of 6.6 percent to have a dry unit weight of 20.1 kN/m~3. During the tests, the air flow is monitored, giving at a given suction value the variation of the flow as a function of the air pressure. In order to apply the generalised Darcy's law for the results analysis, only the tangent at zero pressure to this curve is considered. The obtained air permeability is then compared to that obtained on the same material using the method of Yoshimi and Osterberg (Yahia-Aissa et al. 1997, Determination des proprietes hydromecaniqws de l'argile Kunigel. Rapport de recherche ANDRA, Identif. C RP OCRM 97-001, p. 77.), showing that the two methods are consistent and complementary. The former is much more suitable for the low air void ratio values, whereas the latter is easier for high air void ratio values.