Temperature effects on the swelling capacity and barrier performance of geosynthetic clay liners permeated with sodium chloride solutions

This paper examines the swelling capacity and hydraulic performance of geosynthetic clay liners (GCLs) at different temperatures against sodium chloride (NaCl) solutions. Free swell tests were conducted with deionized water and the NaCl solutions of 0.1–0.4 M. Permeating tests with the 0.4 M NaCl solutions were conducted using soil columns, which consisted of a GCL and underlying base layer soil similar to that in the bottom liner system in a landfill. The measured intrinsic permeabilities of the GCL to the 0.4 M NaCl solution are 5.9 × 10−18 m2 for 20 °C and 2.5 × 10−17 m2 for 60 °C, while the measured free swells to the solution are 8.5 mL/2 g for 20 °C and 11 mL/2 g for 60 °C and the free swells to other solutions tested also increase as the temperature increases. Even after accounting for the temperature dependence of the kinematic viscosity of the NaCl solutions, the intrinsic permeability increases with temperature because bentonite swelling depends on temperature. However, the free swell of bentonites in the GCLs increases as the temperature increases, and the relationship between free swelling and the permeability differs from the common notion that permeability decreases as the free swell increases. Consequently, the previous relationships obtained from free swell tests and hydraulic conductivity tests at room temperature are not applicable at elevated temperatures because at elevated temperatures, the increased intrinsic permeability is related to the decreased swelling pressure.