Osmotic consolidation of expansive soil

Abstract

The mechanical behavior of expansive soils is influenced by the concentration of salts in their pore water. Research has shown that volume change of soil can occur due to a difference in salt concentration in the pore water between different zones of the soil as a result of either osmotically-induced consolidation or osmotic consolidation. The effect of the salt concentration of the pore water in unsaturated soil mechanics can be expressed as osmotic suction. Very little work has been done to quantify the mechanical equivalence of osmotically-induced and osmotic consolidation. This study attempts to quantify the mechanical stress equivalence of consolidation of an expansive soil submerged in a salt solution. Two remoulded soil samples of kaolin - bentonite mixture in proportions of 70% – 30% and 90% - 10%, (kaolin – bentonite) by dry mass were submerged in different concentrated salt solutions to investigate the effect of osmotic suction. Results showed that osmotic suction caused an additional settlement over the consolidation settlement under a mechanical stress but does not affect the soil compressibility. The osmotic coefficient of volume change (mπ) is only a fraction of the coefficient of volume change (mv).