Estimation of the hydraulic conductivity of unsaturated soil incorporating the film flow

In the conventional method for the estimation of the hydraulic conductivity of unsaturated soil, only the capillary water is considered in the estimation. However, it is known that a water film can be formed around soil particles due to the adsorptive force. The water may migrate in the soil through the water film. As a result, both water flow in the capillary water and water film should be considered in the estimation. In this paper, a new equation was proposed for the estimation of the hydraulic conductivity of unsaturated soil by considering the film flow. The proposed method was verified with the experimental data from the literature. It is recommended that both capillary water flow and film flow should be considered in the estimation of the hydraulic conductivity of unsaturated soil.