Geosynthetic Clay Liner (GCL) is the most common term for a composite hydraulic barrier made of geosynthetics and high swelling bentonite clay as the sealing element. They are also known as Clay Geosynthetic Barriers (GBR-C). The widest spread type of GCL is needle-punched, where the sealing bentonite clay is sandwiched between two geosynthetic geotextiles. Other forms of GCLs may also additionally contain a coating or a lamination to either improve the strength of the composite or add other features to the GCL such as a root or a desiccation barrier and may even be used to improve the hydraulic barrier. As geosynthetic clay liners (GCLs) are frequently and often used to replace hard to build compacted clay liners (CCLs) it is useful to compare the hydraulic performance of each liner with respect to overall leakage to demonstrate the heightened performance that can be obtained with needlepunched GCLs. The hydraulic performance of liners is often evaluated by their total leakage and their breakthrough time. Total leakage is simply defined as the volume of leachate that passes through the liner over a given time period. Breakthrough time is defined as the length of time required for leachate to pass through the liner. This paper will compare GCLs and compacted clay liners (CCLs) with each other based on rational mathematical equations in regard to hydraulic performance. Further it will highlight the benefits of GCL products over traditional natural materials, when used for composite liner applications in landfills and discusses several common techniques used in their installation, emphasizing the role that equipment plays in ensuring a successful installation. At the end real field study results will also be presented, demonstrating the efficiency of the different systems.
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