Slope Stability of Geosynthetic Clay Liner Test Plots

Evaluation of Interface Shear Strength between Geosynthetics Under Wet Condition

“…The hydration time for GCL(A) was chosen, referring to the time suggested by Daniel et al (1998) and obtained from preliminary tests. Namely, interface shear tests with varying hydration times were carried out to determine the time showing a constant shear strength value.…”

State-of-the-art report: GCL shear strength and its measurement – ten-year update

“…Full-scale field tests and failure investigations have played an important role in understanding the internal and interface shear behavior for GCLs (Tanays et al 1994;Feki et al 1997;Daniel et al 1998). The advantages of such tests are that GCL shear strength is mobilized under typical field conditions that may include effects of geomembrane wrinkles, subgrade irregularities, panel overlaps, construction procedures, changing climatic conditions (e.g.…”

“…The Daniel et al (1998) study, including associated laboratory direct shear tests, produced several key findings: (1) for reinforced GCLs, GMX/GCL interface shear strengths were lower than internal shear strengths under low normal stress conditions, (2) the NW GT side of a reinforced GCL had higher interface strength than the W GT side when placed against a GMX, (3) hydrated bentonite migrated through the W GTs of some reinforced GCLs and reduced GMX/GCL interface strength over time, (4) the 2H:1V test plots were too steep to yield a safety factor that is normally considered adequate and the 3H:1V test plots yielded safety factors of at least 1.5 for project conditions, and (5) observed failures and non-failures were consistent with limit equilibrium stability analyses using peak shear strengths obtained from short-term shear tests. Based on this latter observation, Daniel et al (1998) concluded that the Cincinnati test plots confirm the accuracy of current design methods and thus field test sections should generally not be required. Daniel (2013) noted, in hindsight, that the 2H:1V failures are not surprising because slope angles were close to interface friction angles and that results of the project pointed the industry toward using NW/NW GCLs to deliver enhanced interface shear strength for slope applications.…”

“…Laboratory and field tests have shown that swelling bentonite can extrude through the supporting geotextiles of a GCL and smear on adjacent materials, forming a slippery interface (Byrne 1994;Gilbert et al 1997;Pavlik 1997;Daniel et al 1998;Eid et al 1999;Triplett and Fox 2001;Vukelic et al 2008;Daniel 2013). In these studies, extruded bentonite was more commonly observed on the W side of a W/NW NP GCL than the NW side.…”

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

“…Daniel et al (1998) and Seo et al (2007) indicated the shear strength of bentonite decreased significantly from 0 to 50% moisture content, but the shear strength at a water content of 50% was approximately the same as that of fully hydrated bentonite.…”