Lower-bound shear strength for geosynthetic clay liners in base liners

摘要

The objective of this paper is to establish the minimum available shear strength fornany type of geosynthetic clay liner (GCL) in a base liner. Direct shear tests are conducted on verynthin (nominally 1 mm thick) specimens of reconstituted bentonite placed against a smoothngeomembrane to measure the drained, residual strength of this interface. The use of thin specimensnminimizes the time required to achieve drained conditions, and also minimizes the shearndisplacement required to mobilize the residual strength; testing times were several weeks andnresidual strengths were mobilized within 10 mm of shear displacement. The Mohr–Coulomb strengthnenvelope developed from these test results corresponds to a secant friction angle of 4.78 over a rangenof effective normal stresses from 250 to 1500 kPa. Limited published information for the shearnstrength of bentonite and GCLs at these effective normal stresses supports the use of this envelope asna lower-bound strength for all types of GCL. This envelope establishes a conservative design checknfor slope stability and a benchmark for evaluating product-specific and project-specific test resultsnwith GCLs.