Characterization of water sorption and retention behavior of partially saturated GCLs using vapor equilibrium and filter paper methods

This paper examines the water absorption-desorption behavior of geosynthetics clay liners (GCLs) using vapor equilibrium method (VEM) as well as the water retention behavior of partially saturated GCLs using the filter paper (FP) method. An overburden pressure equivalent to that of landfill cover soil was applied onto the GCLs to understand the stress- and time-dependent water absorption and desorption behavior of GCLs. The influence of calibration curves for obtaining total and matric suction from FP method on water retention behavior of GCLs was examined. The experimentally obtained discrete suction-gravimetric water content data were fitted with recently developed water retention curve (WRC) models to obtain WRC key parameters which may be used for modeling purposes. This study provides a systematic evaluation of the method of testing, the effect of calibration curves and WRC models on the WRC key parameters. Results show that the relative humidity (RH) and the overburden pressure have a significant influence on the water absorption and desorption behavior of GCLs. In addition, the equilibration time of both absorption and desorption behavior depends on the RH. The WRC (matric or total suction) of GCLs at higher suction obtained using few calibration curves from the FP method is in agreement with VEM. Results also conclude that data obtained using various calibration curves have a significant influence on the WRC key parameters.