You are here:
REPORT OF THE 1995 WORKSHOP ON GEOSYNTHETIC CLAY LINERS
Citation:
Daniel, D. E. AND H. B. Scranton. REPORT OF THE 1995 WORKSHOP ON GEOSYNTHETIC CLAY LINERS. 1995 Workshop on Geosynthetic Clay Liners, Cincinnati, OH, August 09 - 10, 1995. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-96/149, 1996.
Impact/Purpose:
information
Description:
A workshop was held at the EPA's National Risk Management Research Laboratory in Cincinnati, Ohio, on August 9 and 10, 1995. On August 9, attendees were shown field plots of GCLs that have been constructed at a site in Cincinnati, and given a detailed account of the test plot layout, instrumentation, and performance to date. Fourteen test plots, with cross-sections that are typical of landfill cover systems, were constructed. Five of the test plots were constructed on 3H:1V slopes, and the remainder were constructed on 2H:1V slopes. All test plots were two GCL roll widths wide (approximately 10 m), and 20 to 30 m long. The thickness of the cover materials over the GCLs was approximately 900 mm. The objective of the project was to verify that the GCLs would remain stable against mid-plane shear on 3H:1V slopes with a factor of at least 1.5. So long as the slopes are stable at 2H:1V, it can be demonstrated that the minimum factor of safety is 1.5 for s 3H:1V slope. Thus far, all slopes have remained stable with respect to mid-plane shear, although two interface failures did occur between the GCL and an overlying textured geomembrane. Both failures occurred at the interface between the woven geotextile component of a GCL and the geomembrane. Interface shear testing performed after the failures demonstrated that the failures could have been predicted, based on the laboratory shear test results. A significant finding from the project is that in landfill cover applications, the internal strength of GCLs may not be the critical strength - interface strengths may be lower than the internal strength of the GCL. Another significant finding has been that bentonite encased between two geomembranes on one test ploy has undergone unanticipated hydration, when the expectation was that it would remain dry. The cause of hydration has not been isolated but may be related to water migration through the penetrations made for instrumentation cables. On August 10, a series of presentations summarized recent research findings for the field test site, as well as other on-going research projects. Significant information was presented concerning laboratory shear testing results and seepage rates through composite geomembrance/GCL liners based on flow rates in the leakage detection layer of double composite liner systems. This workshop marks the third in a series of workshops. The first two were held in 1990 and in 1992. The breadth and depth of information presented at the 1995 workshop is much greater than in the earlier two workshops, and reflects the maturing of the GCL industry and the efforts of many individuals to develop the technical information that is needed to evaluate and assess GCLs as they are used in waste containment facilities.