Controlling the destructive effects of clay – organic liquid interactions, by application of effective stresses

The magnitude of the effective stresses acting on a clay barrier appear to play a critical role in preserving low hydraulic conductivity, k, during exposure to soluble organic liquids. This paper summarizes the results of a research study on a natural clay from southwestern Ontario permeated with various mixtures of landfill leachate and water-soluble organic liquids at effective stresses ranging from 0 to ~300 kPa. Laboratory testing of "unconfined", water-compacted clays indicated that municipal solid waste leachates containing ethanol and dioxane at concentrations in excess of 70% can cause damaging increases in k of up to 1000-fold. Predamage application of vertical effective stresses can reduce or even eliminate these increases in k because of chemically induced consolidation and closure of macropores that develop as a result of double layer collapse. The levels of static effective stress required to prevent the increases in k were much higher for nonpolar dioxane (> 160 kPa) than for intermediately ...