Geosynthetic clay liners (GCLs) have gained widespread acceptance in many applications where natural soils have been used traditionally. Their competitive cost, high performance, and relative ease of installation are a few of the many reasons why GCLs have become so popular. However, while they offer numerous advantages over compacted clay liners, GCLs have vastly different engineering properties. Foremost among these differences is shear strength, which has been researched nearly to the exclusion of other design issues of equal importance. Not so extensively investigated is the long-term hydraulic performance of the GCL when exposed to commonly encountered leachates and liquids. This design issue requires an evaluation of the barrier component of GCLs―bentonite―upon exposure to various physical and chemical stresses over time. Given its unusual properties, bentonite is an inherently difficult material to evaluate. The purpose of this paper is to discuss bentonite as a long-term hydraulic barrier and to reveal a technological improvement in this important performance parameter.
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