On February 12 during the Geosynthetics Conference 2019 in Houston, Texas, a roundtable discussion was held regarding geocomposite peel testing and a potential new approach for testing of this index property. The session was moderated by Richard Thiel and included approximately 65 attendees. The lively discussion focused on the previously unrecognized high variability of the bond strength between the geonet core and the heat-bonded upper/lower nonwoven geotextiles across the roll width of manufactured geocomposites. The fact that this variability could affect the shear strength and constructability of the product was recognized. It was suggested that the Standard Test Method ASTM D7005, Determining the Bond Strength of Geocomposites, be considered for revision so that the test results would accurately reflect the variability in the bond strength across the roll width.
Valuable input was given by several industry professionals representing a number of industry sectors including (1) Owners: John Workman, (2) Designers: Richard Thiel, Bob Mackey, Richard Erickson, (3) Geosynthetic test labs: Sam Allen, Henry Mock, (4) Consultants: Boyd Ramsey, (5) Academia: George Koerner, (6) Manufacturers: Ed Zimmel, Nathan Ivy, and (7) Installers: Tim Rafter and Junior Thompson.
It was concluded that the current method of testing only five specimens that are 4 inches wide across the width of the geocomposite sample (representing only 13% of the roll width) is inadequate to identify the variation in geocomposite lamination strength across the roll width. This issue and session feedback will be referred to the ASTM Committee D35 on Geosynthetics to explore further to potentially incorporate needed changes into the test standard. It will still be left up to designers to decide how to incorporate the test results into project specifications (a companion paper in the conference proceedings presented by Richard Thiel provides one example approach in this regard). The issue of the minimum, maximum and log-normal variation of the geocomposite lamination strength as regards short-term construction loadings, as well as its long-term durability to provide adequate shear performance, is an area ripe for further research and development of engineering approaches.