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Current status of the Cincinnati GCL test plots
Journal article   Peer reviewed

Current status of the Cincinnati GCL test plots

Robert M. Koerner, David A. Carson, David E. Daniel and Rudolph Bonaparte
Geotextiles and geomembranes, v 15(4), pp 313-340
1997
DOI: https://doi.org/10.1016/S0266-1144(97)10013-9

Abstract

This paper describes the design, layout, construction and current status on the performance of fourteen full scale test plots targeted at assessing the internal shear strength of GCLs in landfill cover applications. Five different commercially available GCLs from four manufacturers were used in the study. Each test plot is two geosynthetic clay line roll widths wide, with lengths of 29m (95 ft) on the 3(H)-to-1(V) (horizontal-to-vertical) slopes and 20m (67 ft) on the 2(H)-to-1(V) (horizontal-to-vertical) slopes. The plots are being monitored with numerous deformation ‘telltales’ as well as subgrade and GCL moisture gages. Two slides occurred shortly after construction. Both involved the upper surfaces of the GCLs against the overlying textured geomembranes. The slides were clearly the result of bentonite lubricated interfaces and (although of interest) did not relate to the internal shear strength focus and goals of the project. Upon inducing internal shear stress in the GCLs by cutting all of the overlying geosynthetics, the deformations have been small except for one plot. This plot involved a unreinforced bentonite GCL, sandwiched between two geomembranes. It was sampled and found to have a large region of unexpected and excessively high moisture content. Subsequently, the test plot slid, the interface being the upper geomembrane against the bentonite of the GCL. The test plot was constructed a second time and the current response is more in keeping with the anticipated behaviour. Other than these slides, however, all of the other GCL plots appear to be stable. If the internal stability of the GCLs continue, it can be assumed that the 2(H)-to-1(V) slopes have a factor-of-safety of 1.0 or greater. This being the case, the 3(H)-to-1(V) slopes have a factor-of-safety of 1.5 or greater. While this hypothesis is still being substantiated, it speaks well for the internal shear strength of the GCLs used in the study when properly installed. The project is ongoing as of, the writing of this paper.

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