Unsaturated behaviour and cation self-diffusion of geosynthetic clay liners in Antarctica

The impact of time-dependent unsaturated behaviour of virgin and the impact of cation self-diffusion on the time-dependent unsaturated behaviour of exhumed geosynthetic clay liner (GCL) specimens were investigated using a chilled mirror hygrometer. Total suction values (after 7 weeks' water homogenisation) are reported for ten virgin (six different bentonites) and one GCL exhumed after exposure to the thermo-hydro-mechanical (THM) conditions in Antarctica. The time-dependent unsaturated responses of four different virgin GCLs 1 day and 1 week after hydration are compared with the results at homogenisation and the implications discussed. For the suction (0.1-300 MPa) and water content range (5-140%) examined, the post-water homogenisation water retention behaviour of the GCLs is affected by bentonite characteristics. At a given gravimetric water content, the total suction of GCLs increased with increasing smectite content and total soluble salt content and decreased with increasing total bound cation content in the bentonite. Cation self-diffusion also increased the total suction in the GCL exhumed after exposure to Antarctic THM conditions. It is concluded that the impact of cation self-diffusion on the unsaturated behaviour of a GCL during its time in service before exposure to pollutants needs to be considered in designing hydraulic and gas barriers.