Salinity and Clay Mineralogy Effects on Consolidation Behavior of Pure Clays

Pure clays or sand-clay mixtures with different clay mineral are widely used in liners or vertical barriers of waste landfill, and the pore water was characterized by its high salinity in coastal area. Thus, it is essential to understand the salinity effects on their consolidation behavior. In this study, oedemeter and SEM tests were conducted on four pure clays with different mineralogy. Several aspects of soil behavior, such as compression index, the end of primary consolidation stage and micro-structure, were investigated in view of pore water salinity effect. The results show that higher ionic concentration significantly decreases the compression index C-c and liquid limits (LL) for clays containing montmorillonite. While the period of primary consolidation was shorten under the impact of water salinity. For kaolinite with or without sodium chloride, a similar C-c, LL and the ending time of primary consolidation stage t(p) were observed. In view of flocculation, the salinity effect on consolidation behavior was interpreted. Increasing in salinity allows a flocculation and particle readjustment at constant water content for montmorillonitic clay. Then, larger inter-particle spaces and effective void ratio increased the permeability and decreased the drainage period, and larger internal frictions decreased the compression index C-c and LL.