Field observed GCL panel shrinkage for five GCLs in composite liners

Field observed shrinkage was quantified and compared for one GCL type left covered only by a black geomembrane, a white geomembrane and 0.3 m of gravel cover, and additionally for four GCLs left covered only by a black geomembrane for up to 28 months exposure at the QUELTS II experiment. All GCLs were needle-punched geotextile encased: one containing fine granular bentonite, two with powdered bentonite, one with polymer amended granular bentonite, and one multicomponent GCL with a film coating installed film up. All the GCLs examined have the potential to shrink with the magnitude of the shrinkage primarily dependent on the thermal/moisture cycles to which it is subjected and the degree of adhesion between panel overlaps. It is shown that the panel overlap adhesion can be highly variable and this is primarily attributed to condensation of water vapour below geomembrane wrinkles during daily thermal cycles. With a an initial GCL overlap of 300 mm, the shrinkage observed over 28 months left ≥ 32% of the original overlap, however if the overlap had been only 150 mm then gaps or ineffective seems would have occurred for several GCLs. Guidance regarding mitigating GCL panel shrinkage is provided.