Parameters affecting the vertical deformations of GCLs during hydraulic conductivity tests

The hydraulic conductivity and swelling behaviours of geosynthetic clay liners (GCLs) are closely related to each other. An alternative system was developed to measure the swelling or compression (vertical deformation) behaviour of GCLs during permeability tests by simply modifying flexible wall permeameters. In this system, the cell part of the flexible wall permeameter was removed, thereby allowing the application of vertical stress on the specimen to be provided by a simple frame system. The vertical deformations were determined using dial gauges, which were placed on the frame. In this study, vertical deformation and hydraulic conductivity were examined depending on the concentration of test liquid, mass per unit area (MPUA) of GCL, and vertical stress. GCLs within 3.0-5.5 kg/m 2 MPUA were subjected to hydraulic conductivity tests under two different vertical stresses and with various CaCl 2 solutions. The results showed that the hydraulic conductivity increased, and the pattern of vertical deformations remarkably changed when the concentration of permeant increased. Furthermore, reducing the vertical stress applied on GCLs resulted in an increase in vertical swelling; however, there was no definite relationship between hydraulic conductivity and effective stress. Similarly, reducing the MPUA of GCLs decreased the vertical swelling, but increased the hydraulic conductivity from 2.8×10 -11 m/s to 3.4×10 -7 m/s.