Craig H. Benson, PhD, PE, NAE
Wisconsin Distinguished Professor Emeritus
University of Wisconsin-Madison
chbenson@wisc.edu
ABSTRACT: Geosynthetic clay liners (GCLs) are broadly used as hydraulic and contaminant transport barriers for a wide range of containment systems, ranging from heap leach pads for ore processing to municipal solid waste landfills to low-level radioactive waste storage facilities. GCLs are highly effective in controlling the flow of water and the migration of contaminants when used in appropriate scenarios. They can be ineffective when deployed in unsuitable environments. This presentation will cover lessons learned regarding appropriate use of GCLs from more than two decades of research, forensic analysis of case histories, and engineering practice. The presentation covers the fundamental mechanisms that control the hydraulic conductivity of GCLs, including GCLs prepared with granular or powdered bentonite as well as bentonite-polymer composites. Factors that alter GCLs are described, including chemical interactions with liquids, wet-dry cycling, and freeze-thaw cycling. Methods to evaluate GCLs in the laboratory are described and appropriate specifications for design are discussed. Case histories are used to illustrate key points regarding design, specification, and deployment of GCLs.