Specific Surface and Hydraulic Conductivity of Fine-Grained Soils

The Kozeny-Carman (K-C) equation can be used to predict the saturated hydraulic conductivity of a soil, provided enough information is given regarding the porosity and the specific surface. The main limitation of the K-C equation lays in the determination of the specific surface of the soil, a parameter that is not regularly measured but can be estimated with analytical or empirical relations. A method to evaluate the soil’s specific surface is proposed, which combines the contribution of the plastic clayey fraction and that of the granular silty-sandy particles. The applicability of the proposed method and its effect on the performance of the K-C equation have been verified by comparing the K-C estimated hydraulic conductivity with the result of approximately 130 hydraulic conductivity tests on saturated soil specimens in the triaxial apparatus. The results show that the K-C equation and the method for estimating the specific surface predict within an order of magnitude the saturated hydraulic conductivity of clayey to silty-sandy soils with measured hydraulic conductivity in the range 1×10−11–5×10−6 m/s.