The influence of bentonite extrusion on shear strength of GCL/geomembrane interface

Laboratory Investigation of the Effects of Temperature and Moisture on Interface Shear Strength of Textured Geomembrane and Geosynthetic Clay Liner

“…No consistent trend was exhibited between AR and 50% moisture content (Figure 4.8). The trend of decreasing moisture content with increasing δ agrees with previous work (McCartney et al 2004, Seo et al 2007, Vukelic et al 2008, Chen et al 2010 and is likely due to increased bentonite extrusion. Under cover liner normal stresses, the extruded bentonite may clog the spaces between the geotextile filaments and lubricate the geotextile filaments, decreasing the amount of hook and loop interaction and in turn, decreasing the interface friction angle.…”

“…Investigation of internal shear strength of GCLs is not as critical, as the use of needle punched (NP) reinforced GCLs has resulted in internal shear strengths to be greater than interface shear strengths under the majority of investigated normal stresses (McCartney et al 2002, Zornberg and McCartney 2009, McCartney et al 2009a). Many researchers have investigated the shear resistance along geosynthetic interfaces, specifically between GCLs and geomembranes (e.g., Hewitt et al 1997, Triplett and Fox 2001, Seo et al 2007, Vukelic et al 2008, McCartney et al 2009a, Zornberg and McCartney 2009, and Chen et al 2010. The majority of GCL interface shear research reported uses a large scale direct shear device to determine the interface shear strengths between GCLs and geomembranes (Hewitt et al 1997, Triplett and Fox 2001, McCartney et al 2009a).…”

“…Between a textured GM and a GCL, the bentonite can act as a lubricant, decreasing the interface friction angle (Seo et al 2007). As the moisture content increases, the bentonite becomes less viscous, increasing the amount of extrusion (Seo et al 2007, Vukelic et al 2008, Chen et al 2010). Vukelic et al (2008) reported that bentonite primarily extrudes through woven geotextiles and through thin nonwoven geotextiles (having mass per unit area less than 220 g/m 2 ).…”

“…As the moisture content increases, the bentonite becomes less viscous, increasing the amount of extrusion (Seo et al 2007, Vukelic et al 2008, Chen et al 2010). Vukelic et al (2008) reported that bentonite primarily extrudes through woven geotextiles and through thin nonwoven geotextiles (having mass per unit area less than 220 g/m 2 ). The amount of bentonite extruded generally increases as the geotextile becomes thinner, the bentonite is wetted, and more water flows to the interface during consolidation .…”

“…Interface shear strengths were measured using large-scale interface direct shear tests under representative field conditions. Targeted temperatures and moisture contents were tested, unlike the majority of previous investigations of T-GM/GCL interface shear strength (Hewitt et al 1997, Triplett and Fox 2001, McCartney et al 2004, Seo et al 2007, Vukelic et al 2008, McCartney et al 2009a, Zornberg and McCartney 2009, and Chen et al 2010.…”