Laboratory Simulation of Bentonite Erosion by Downslope Flow on a GCL: Fid-Bau Portal

Laboratory Simulation of Bentonite Erosion by Downslope Flow on a GCL

Ashe, L. / Rowe, R. Kerry / Brachman, R. W. I. / Take, W. Andy

Abstract

Under some circumstances, leaving a composite geomembrane/geosynthetic clay liner (GCL) exposed to solar radiation in the field has been shown to cause shrinkage of the underlying GCL. Recent field studies have shown that leaving a composite liner exposed can also lead to erosion of bentonite from the GCL due to downslope moisture migration. This paper reports an experimental technique that reproduced similar erosion in the laboratory on a typical landfill side slope of $3 H : 1 V$ . The test method simulates the features that occur with the erosion of bentonite caused by downslope migration of evaporative water in the field. The laboratory tests demonstrate that erosion features can be present but may not be visible unless the appropriate back lighting is used. Erosion features measuring over 25 mm in width were produced. The test method simulated the features that were observed with bentonite erosion in the field and has the potential for use in examining other factors that may affect this type of erosion. The test method developed can be used for examining the response of GCLs when part of a composite liner that will be left exposed. The findings from this laboratory study provide additional motivation for timely covering of composite liner systems as recommended by GCL manufacturers.