Physical Response of Geomembrane Wrinkles Overlying Compacted Clay

Brittle rupture of an aged HPDE geomembrane at local gravel indentations under simulated field conditions

“…• A 0.4 mm thick circular lead sheet (500 mm in diameter) was placed on the GCL for monitoring geomembrane strains (e.g., Witte 1997;Tognon et al 2000;Gudina and Brachman 2006;Gudina 2008a, 2008b;Dickinson and Brachman 2008;Rowe et al 2010b) and to be used as part of the leak detection system described later.…”

“…In many cases, it is loaded by an out-of-plane overburden pressure forcing gravel to indent the liner (Figure 9). The level of indentation will depend on the pressure, gravel, and protection layer but in each case it will induce strains in the GMB that will vary from one location to another (Tognon et al 2000;Gudina and Brachman 2006;Gudina 2008a, 2008b;Dickinson and Brachman 2008;Brachman and Sabir 2010;Gudina and Brachman 2011;Sabir and Brachman 2012). Thus, one might hypothesise that unless there are surface scratches on the GMB, coincidentally, at locations where there are significant tensile strains through the entire thickness of the GMB, they will have little effect on the GMB cracking.…”

“…Cracks were observed at strains as low as 6%, highlighting the need to prevent indentations that cause tensile strains of this magnitude by ensuring an appropriate protection layer between the drainage gravel and GMB. Various types of protection layer have been used to limit local tensile strains in GMBs used in landfills including: thick soil layers Müller 1996, 2003;Gudina and Brachman 2006;Dickinson and Brachman 2008;Rowe et al 2013); very thick nonwoven needle-punched geotextiles (Seeger and Müller 1996;Zanzinger 1999;Gudina and Brachman 2006;Brachman and Gudina 2008a;Koerner et al 2010); multi-layered geotextiles composites (Brachman and Sabir 2013); various sand-filled geocomposites (Saathoff and Sehrbrock 1994;Zanzinger 1999;Tognon et al 2000;Dickinson and Brachman 2008); rubber geocomposites (Zanzinger 1999;Tognon et al 2000); and recycled rubber tire shreds (Reddy and Saichek 1998;Dickinson and Brachman 2008). At present, only thick soil layers have been shown to limit the long-term tensile strain to very small levels (, 2%) for 50 mm coarse gravel above a 1.5 mm thick HDPE geomembrane and at a pressures up to 1000 kPa (Tognon et al 2000;Gudina and Brachman 2006;Gudina 2008a, 2008b;Dickinson and Brachman 2008).…”

“…These tensile strains may cause short-term gravel punctures in GMB liners (e.g., Gudina 2007). Research has shown that these short-term (ductile) punctures can be minimised by the selection of a suitable protection layer Koerner et al 1996;Tognon et al 2000;Gudina and Brachman 2006;Dickinson and Brachman 2008;Koerner et al 2010;Brachman et al 2011). Assuming sufficient protection to avoid short-term puncture, the second possible mechanism for hole formation after waste placement is 'long-term' rupture of the GMB liner due to stress cracking that is most likely related to the magnitude of the sustained tensile strains in the GMB following installation at local gravel indentations, the stress crack resistance of the GMB, and temperature.…”

“…This can be achieved by selecting a proper protection layer aiming to limit the tensile strains in the GMB liner to prevent stress cracking rather than only preventing short-term puncturing Müller 1996, 2003). Numerous short-term physical experiments have examined the magnitude of the strains induced by drainage gravel for GMBs with different protection layers and clay liners (Tognon et al 2000;Gudina and Brachman 2006;Dickinson and Brachman 2008;Gudina 2008a, 2008b;Gudina and Brachman 2011;Hornsey and Wishaw 2012). However, since these experiments were intended to quantify the demand (i.e., the local tensile strains that may develop in the GMB) they were not run sufficiently long enough to assess the potential long-term GMB resistance -specifically, whether or not the geomembrane can rupture under sustained tensile strains.…”