Effect of Salt Solutions on Landfill Clay Liners

Engineered waste landfills separate the buried waste from the groundwater system and the above ground environment during and after the operational periods of the disposal facility. Liners of these landfills are of great import-anttce as they play a crucial role in minimizing pollutant migration and therefore preventing ground water contamination. Liners may consist of a locally available soil and bentonite mixtures. In this study effect of NaCl and MgCl2 solutions of various concentrations has been investigated.The mixtures were prepared with a local clay specimen from Varamin and a proportion of bentonite content of 10 % and 20 % of total dry weight. Laboratory tests including 1D consolidation for determining permeability and compressibility of the soil mixtures, liquid limit and free swell tests were carried out. Results indicated that both solution type and its concentration affect the properties of the mixtures. Comparison of hydraulic conductivity of different salt solutions shows that the divalent cations have more effect than monovalent cations. Comparison of different salt concentrations for a particular salt on a particular soil mixture shows that the hydraulic conductivity decreases with decreasing salt concentration. This decrease can be attributed to an increase in diffuse double layer thickness.