Permeabilities of various swelling clay suspensions were evaluated by performing constant-pressure filtration tests in accordance with Ruth's equation and Darcy's law at several pressures ranging from a low hydraulic head, which simulated typical magnitudes of hydraulic gradients at waste landfills, up to pressures used in conventional filtration tests for bentonite muds. Values of filtration rate coefficient, specific resistance of wet cake and hydraulic conductivity of Na-bentonite, Na-exchanged bentonite, and kaolin-bentonite mixture (1:1) were examined. Ca-bentonite and kaolin were used as references for the low or non-swelling samples. Mud cakes from suspensions containing bentonite exhibited significant compressibility. Consequently, void ratio and specific resistance of wet cake were used as indications of permeability and compressibility of clay samples.
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