EFFECTS OF DESICCATION ON THE HYDRAULIC CONDUCTIVITY VERSUS VOID RATIO RELATIONSHIP FOR A NATURAL CLAY

Abstract

Undisturbed and reconstituted specimens of a soft gray Pleistocene clay were subjected to various degrees of desiccation, resaturated, and then tested to determine their hydraulic conductivity (k) versus void ratio (e) relationships. The log k versus e relationships for all of the specimens have a common shape that is characterized by a steep slope at high void ratios and a much flatter slope at lower void ratios. Desiccation affected primarily the magnitude, and not the shape, of the log k versus e relationships. With increasing degrees of desiccation, the relationships were displaced in the direction of increasing hydraulic conductivity. The desiccation-induced changes for the undisturbed specimens were greater than those exhibited by the reconstituted specimens. These characteristics of the log k versus e relationships can be explained in terms of the cluster model of clay fabric. At high void ratios, the steep slope of the log k versus e relationship is dominated by reductions in the sizes of the macropores surrounding the clusters. At lower void ratios, the increasing relative importance of pore-size reductions within the clusters is reflected in the decreasing slope of the log k versus e relationship. The generally higher hydraulic conductivity values with increasing degrees of desiccation in both the undisturbed and reconstituted samples reflect desiccation-induced shrinkage of clusters.