Dynamic shear response of a geomembrane/geosynthetic clay liner interface

A series of large-scale dynamic direct shear tests were performed to measure the interface shear strength between a textured geomembrane (GMX) and a needle-punched geosynthetic clay liner (NP GCL) under cyclic loading. The study was conducted for large ranges of shearing normal stress (σ_n,s= 13 to 2071 kPa) and cyclic displacement amplitude (Δ_a = 2 to 30 mm). The experimental data indicate that the failure mode of a GMX/NP GCL specimen depends on both σ_n,s and Δ_a. All tests conducted at low to moderate normal stress levels (σ_n,s ≤ 692 kPa) produced interface failures. Partial to complete internal failures were observed for some tests at low Δ_a and high σ_n,s. Interface failures still occurred for the largest displacement amplitude (Δ_a = 30 mm) at all normal stress levels. In general, the testing program has indicated a more complex interrelationship among failure mode, normal stress level and shear displacement rate than has been previously considered for these materials.