Approach to Estimate Hydraulic Conductivity Function from Soil-Water Retention Curve for Noncohesive Soils

Pavement materials are prone to damage due to mechanical loadings and rainfall infiltration. The rainfall initiates moisture movement within the layers and accelerates the damaging rate. A better understanding of the moisture flow and damage can be achieved by rigorous and efficient modeling. The hydraulic conductivity function (HCF) is one of the essential soil properties for numerical seepage modeling. Due to the difficulty in direct HCF measurements, it is generally predicted empirically or statistically by integration along the soil-water retention curve (SWRC) based on the fundamentals of fluid flow in porous media. This paper presents an analytical approach to predict the HCF from experimentally obtained data of an SWRC for noncohesive soils. The model is derived based on the Hagen-Poiseuille law and Darcy law and considered the pore size distribution, porosity, and geometry of the soil grains as inputs. The pore size distribution is considered analogous to a normalized SWRC based on the fundamentals of the capillary theory. The proposed model is validated based on a large number of published experimental data of SWRC and HCF, illustrating the robustness of the model. Additionally, the application of the model is presented for the pavement drainage design.