Generalized Fitting Parameters of Three Permeability Functions for Predicting Water Coefficient of Permeability of Lateritic Soil

The understanding of water flowing through unsaturated soil, such as in the upper layer of a residual hillside or earth dam, is particularly important for numerous geotechnical and geo-environmental problems. However, the effect of the water coefficient of permeability on flow of seepage through unsaturated soil, which is a function of void ratio and volumetric water content (or matric suction), is often ignored in engineering practice due to the requirements of a more advanced testing equipment and a longer testing duration for the determination of such a coefficient. A flexible-wall permeameter has been manufactured and used to determine the water coefficient of permeability of unsaturated lateritic soil under wetting condition. Three permeability functions have been evaluated and fitted to the laboratory measured results. From this, generalized fitting parameters, in terms of effective normal stress, of the three permeability functions have been derived for the study soil. The proposed generalized fitting parameters together with the permeability functions will provide practicing engineers with the essential parameter for the analysis of seepage related problems involving lateritic soil.