Destructive and Nondestructive Testing of Geosynthetic Clay Liner(GCL) Panel Seams

摘要

Geosynthetic clay liner (GCL) panel separation of the overlapping edges has occurred in five known situations when theyrnhave been placed beneath geomembranes exposed to the atmosphere. Exposure time varied from 15 mos.-to-5 yearsrnand the separation distances varied from loss of overlap to as much as 1.2 m. Of course, any amount of physicalrnseparation challenges the concept of a composite liner and should be avoided. The current thinking to prevent panelrnseparation when exposed conditions are necessary is a mechanical bonding (or “seaming”) of the initial overlaps. Thisrnpaper will first address manufacturing of seven different seaming types, aka, procedures. It then introduces seamrnstrength testing methods for GCL seams.rnThe testing methods described herein can be conducted in the laboratory as destructive tests and/or in the field asrnnondestructive tests. Both types can be conducted on GCL seams irrespective of how the seams were made in the field.rnThe destructive test method is used to determine the ultimate tensile strength of the GCL seams. It is straightforward andrnfollows similar procedures of geomembrane seam testing in shear. Results can then be compared to the unseamedrnGCL’s wide width tensile test results and thus a seam efficiency can be calculated.rnIn determining the in-situ GCL seam strength, numerous trials in gripping and evaluating representative samples ofrndifferent thickness, geometry, and stiffness were performed. The resulting recommended field test places the GCL seamrnin a shear mode such that the applied force is less than the ultimate strength in a manner similar to conventionalrnnondestructive geomembrane testing.