Static shear strength of geosynthetic clay liners

The focus is hydrated needlepunch-reinforced GCLs and their interface with textured high-density polyethylene geomembranes. Hydrated sodium bentonite has very low shear strength. Reinforced GCLs can be manufactured as needlepunched or stitch-bonded. Needlepunching is now the preferred method and involves the use of barbed needles to pull nonwoven fibers from one geotextile through the bentonite core and the opposite geotextile. Peak interface strengths for a GMX placed against the nonwoven side of a NP GCL are higher than those for the woven side due to extrusion of hydrated bentonite through the woven geotextile. The variability of normal stress at failure mode transition highlight the need for project-specific shear tests using representative materials and conditions. Observations of internal shear failure of NP GCLs are thus far limited to the laboratory because there are no known cases of internal shear failure of NP GCLs in the field.