Enhanced Measurement of Geosynthetic Interface Shear Strength Using a Modified Inclined Plane Device

Composite lining systems comprising different geosynthetics and soil are typical capping devices in modern landfills. Analyses of the behavior of capping devices have shown that they are very sensitive components thanks in part to the shear strength of geosynthetic interfaces, many of which were reported to have controlled slippage between capping lining components during landfill slope failures. There are some laboratory testing alternatives for measuring the shear strength of the interface between geosynthetics or between geosynthetics and soil. The inclined plane test is especially appropriate for shear strength tests under low normal pressure which is a specific condition of these geosynthetic systems on cap cover. However, the selected shear strengths, inferred from the laboratory experimentation, show considerable variability, which depends on the test procedure. This work proposes a new procedure and a new interpretation of the inclined plane test taking as an example the interface between geospacers and geomembranes often considered as a critical interface. The measurement of displacement acceleration during the test gives the possibility of more accurately defining the large sliding displacement shear strength, which may approach the true residual condition.