Static and Dynamic Shear Strength of a Geomembrane/Geosynthetic Clay Liner Interface

Abstract

A series of monotonic (single-direction) and dynamic (bi-directional) direct shear tests were performed involving the interface of a textured geomembrane (GMX) and a needle-punched geosynthetic clay liner (GCL).A large dynamic direct shear machine was used to perform the test procedure.The GCL was hydrated and placed on a stationary bottom plate consisting of an aggressive gripping surface with steel teeth approximately 1.5 mm in height.The textured side of the GM was then placed against the top-half of the GCL.The smooth side of the GM was secured to a steel pullout plate with epoxy.The interface was tested in monotonic shear at varying displacement rates and in cyclic shear at multiple displacement amplitudes.All cyclic tests were followed by a post-cyclic static interface shear test.The series of shear tests were performed to investigate a number of factors: (1) whether internal GCL failure could be induced at high normal stresses, (2) the effect that a range of normal stresses (13 to 1382 kPa) can have on interface behavior, and (3) the effects of displacement rate and displacement amplitude on static and dynamic shear response, respectively.The results presented in this report indicate that monotonic displacement rates have no effect on shear strength at high normal stresses (348, 692, and 1382 kPa), and vii