Chemico-Osmotic Coefficients of Geosynthetic Clay Liners under Different Confinement Conditions

Chemico-osmotic diffusion tests have been widely used to determine the chemico-osmotic coefficient (omega) of soils and geosynthetic clay liners (GCLs). A modified device for chemico-osmotic testing has been developed, which offers the option to confine the specimen by a load cell to monitor the total stress, besides the commonly adopted approach (confinement by a blocked piston). Being the strain conditions slightly different between the two approaches (i.e., small-strain versus no-strain), comparative chemico-osmotic tests have been performed. A dense prehydrated GCL and a 20 mM KCl as source solution were used. Under the no-strain condition omega was 0.33. Under the small-strain condition. was 0.31, and the total vertical stress changed from 59 kPa in equilibrium with deionized water to 22 kPa in equilibrium with 20 mM KCl. Therefore, very close osmotic coefficients were obtained, with the advantage of monitoring the vertical stress during the test when using the load cell.