Calculation of Saturated Hydraulic Conductivity of Some Pedal Clay Soils Using Micromorphometric Data

Abstract The saturated hydraulic conductivity ( K sat ) was calculated for undisturbed freeze‐dried samples of seven clay soils, by using micromorphometric Quantimet data. Voids were characterized in terms of quantity (number and length), type and directly measured size. Methylene blue was used to indicate flow patterns. A statistical planar and tubular void‐interaction model was used to estimate sizes of “necks” in the flow system, which were assumed to determine K sat . Measured K sat values were within the calculated K sat range, when relatively large, vertically continuous tubular voids were not present. Very small variations of the width of planar “necks” had a strong effect on the magnitude of K sat . Soil which was moist when sampled had larger planar “necks” and higher K sat values than soil which had been in wet condition for several months. This difference was attributed to the effects of soil swelling. In general, volumetric percentages of active (stained) voids (estimated by % surface area) were <1. This illustrates the basic difficulty of estimating K sat in clay soils by methods which use relative volumes of voids.