One from the archives: ASTM Committee D35 on Geosynthetics’ March 2013 announcement of a direct shear-related revised test for geosynthetic clay liners (GCLs) has us recalling Geosynthetica’s May 2011 article on an at-the-time new direct shear guide. The March 2013 revised standard is ASTM D6243-13 – Standard Test Method for Determining the Internal and Interface Shear Resistance of Geosynthetic Clay Liner by the Direct Shear Method.
Here is the brief note published in May 2011:
ADVANCES IN BARRIER GEOSYNTHETICS
Guide for Evaluating Direct Shear
ASTM Committee D35 soon will publish a much-needed guide for evaluating direct shear results involving geosynthetics. Some projects have been rejected because of misinterpretation of interface shear strength results regarding GCLs, geomembranes, or other geosynthetics.
“On a slope, those types of interfaces can be the critical slip plane,” said Chris Athanassopoulos of CETCO Lining Technologies. Athanassopoulos took the lead on compiling D7702.
“What the document does is help eliminate some of the questions on how the products perform,” said TRI Environmental’s John Allen. “You need to look at everything in terms of shear strength and not just friction angle and adhesion.”
Both note that D7702 will greatly help ease the process of updating specifications, the wide range and differing quality of which have helped bring this guide into existence.
The D7702 guide does not say explicitly how things must be done, but it does provide ample evidence for the designer to know just how conservative his design might be. Ultimately, the guide is intended to assist designers and users of geosynthetics. It is not intended to replace education or experience and should only be used in conjunction with professional judgment.
Athanassopoulos and his industry colleagues have assembled around 40 reference documents in D7702. “For people who don’t work with these materials every day, they will be able to go to one location to help them evaluate their direct shear test results,” Athanassopoulos said.
Special thanks to John Allen (www.geosyntheticstesting.com) and Chris Athanassopoulos (www.cetco.com) for sharing their field expertise. Have insight you’d be willing to share with the geotechnical community? Contact us.
