The Effect of Saline Fluid on Hydraulic Properties of Clays

The effect of pore fluid concentration on the hydraulic conductivity of barrier material is one of the key factors which are considered in the long-term performance of a geological repository. The current study presents the effect of various NaCl concentrations on Atterberg limits and hydraulic properties of two bentonites and one kaolin clay. The results indicated that the liquid limit, shrinkage limit, and consolidation characteristics of bentonites such as compression index (CC) and the time required for 90% of consolidation (t90) were decreased significantly with an increase in salt concentrations. Similarly, the hydraulic conductivity and coefficient of consolidation (Cv) increased drastically with increase in salt concentrations; however, the significant impact was found for the high smectite bentonite. The experimental results showed that the hydraulic conductivity of the clays mainly depends on the particle arrangement rather than percentage of clay fraction and consolidation stress. For kaolin soil, both the liquid limit and shrinkage limit were found to be slightly increased up to 0.5 M NaCl, however, the effect was found to be decreased at further increase in concentrations, whereas hydraulic conductivity was found to be increased with increase in NaCl concentration. Further, the effect of molding water content on the consolidation characteristics of the clays was also investigated. The parameter compression ratio was used to evaluate the impact of initial moisture content on the compression index of the soil specimens. The hydraulic conductivity of the clays was noted to be increased at higher pore fluid concentration, due to the diminishing of the diffused double-layer thickness of clay minerals.