Forensic examination of field GCL performance in landfill capping and mining containment applications

Geosynthetic Clay Liners (GCL’s) have been used extensively in landfill capping and mine containment applications in the Australian environment, since 1996, and while they have been widely accepted by regulatory authorities and design engineers over this time, some questions remain over their long-term in-field service life and performance. To better evaluate the field performance of GCL’s in terms of hydraulic performance, changes to bentonite mineralogy and physical characteristics, an on-going study of the in-field performance of GCL’s exhumed from landfill capping and mine containment sites around Australia has been initiated. Our preliminary results presented in this paper support previous research indicating that superior field hydraulic performance in GCL’s are related to high RMD values, which provide a low risk of bentonite calcium for sodium exchange. However, for one site with marked wet/dry cycling, calcium for sodium exchange due to low RMD values, coupled with low moisture content, hardly influenced the GCL hydraulic performance after 6 years.