ABSTRACT
Measurement of the coefficient of permeability of unsaturated soils by the steady-state methods, though more accurate than the transient-state methods, is more difficult and time-consuming. The condition for steady state is achieved when the inflow is equal to outflow. In some cases, it is near impossible to obtain the steady-state condition. A review of transient-state methods to measure unsaturated permeability can be found in Benson and Gribb. Transient-state methods include Bruce-Klute adsorption, sorptivity, outflow, instantaneous profile and thermal methods. The instantaneous profile method using a soil column is described in ASTM D7664-10 Method A. The instantaneous profile method makes use of mass continuity to evaluate the instantaneous water content and suction profiles of the soil column one-dimensional water flow condition. Infiltration at the top of the soil column can be applied by a peristaltic pump system where the amount of water flowing onto the top surface of the soil column can be measured using a weighing balance or graduated cylinder.
