A REVIEW OF THE INFLUENCE OF CLAY BRINE INTERACTIONS ON THE GEOTECHNICAL PROPERTIES OF CA-MONTMORILLONITIC CLAYEY SOILS FROM WESTERN CANADA

Natural Ca-montmorillonite clay soils or engineered clay barriers in w estern Canada are often used to contain brine generated from the surfa ce disposal of potash tailings or from drilling activities associated with the oil and gas industry. The performance of these barriers has r anged from excellent to poor. The influence of salt brines on the geot echnical properties of these soils has been recognized as a potentiall y important factor for some time. It has been well documented in the l iterature that the behavior of clayey soils is strongly influenced by physicochemical interactions between clay particles and pore-fluid che mistry; consequently, the properties of these soils are sensitive to c hanges in the electrolyte concentration of the pore fluid. An increase in the concentration of the pore fluid to the levels of a concentrate d brine can cause significant changes in the geotechnical properties o f the soil. In this paper, the impact of brine contamination on the ge otechnical properties of two Ca-montmorillonitic clayey soils of glaci al origin from western Canada is reviewed. The influence of clay-brine interactions on the index properties (liquid limit, plastic limit, pl astic index, mineralogy, density, grain size, and compaction character istics), mechanical properties (volume change and shear strength), and hydraulic properties (hydraulic conductivity) is described. A quantit ative explanation for the changes that occur in the hydraulic and mech anical properties of these soils as a result of brine permeation is al so provided. This explanation relates the changes in pore-fluid chemis try to changes in an effective physicochemical stress state. This appr oach may be used to predict the changes in hydraulic conductivity, vol ume, or shear strength of a clayey soil as a result of brine contamina tion.