Water permeability of unsaturated compacted kaolin

The paper presents an experimental investigation into the permeability of compacted kaolin. Tests were performed in a suction-controlled oedometer using the air overpressure technique: ambient air pressure (raised above the atmospheric pressure) was kept constant and pore water pressure was modified. Permeability was measured by monitoring water inflow in response to a suction decrease and interpolating experimental data using a simplified solution of Richards’ equation (unsteady-state method). Corrections were made to account for the impedance of the high air-entry ceramic disc, the water lost by evaporation into the air pressure line and the air diffusing through the ceramic. The experimental results have shown that axis-translation technique may be problematic at high degrees of saturation and that permeability can be significantly underestimated.