EFFECTS OF EXCHANGEABLE CATIONS ON HYDRAULIC CONDUCTIVITY OF A MARINECLAY

A laboratory study of the hydraulic conductivity (HC) of a marine clay with monovalent, divalent and trivalent cations revealed large differ ences in HC. The exchangeable cations employed in this study are Na, K , NH4, Mg, Ca and Al in order of increasing valency. An interpretation of the results derived from consolidation tests suggests that HC is s ignificantly affected by the valency and size of the adsorbed cations. An increase in the valency of the adsorbed cations leads to quicker r ates of consolidation and higher HC, while, for a constant valency an increase in the hydrated radius of the adsorbed cations results in a l ower rate of consolidation and HC. The reduction in HC was related to the dispersion and deflocculation of clay. Lower valency and higher hy drated radii of the exchangeable cations enable the double layer repul sive forces to predominate, thereby increase dispersion and defloccula tion.