Air channel testing of thermally bonded PVC geomembrane seams

Polyvinyl chloride (PVC) possesses excellent thermal welding characteristics, such as a wide thermal seaming range and the absence of a need for surface preparation such as grinding. The focus of this study was to utilise these welding characteristics to develop a procedure for air channel testing of dual track thermal seams and recommend that destructive testing of PVC geomembranes be reduced and possibly discontinued. This is possible because of the development of a relationship between thermally welded seam burst strength and seam peel strength for a given sheet temperature. To develop this relationship, test welds were created using hot air and wedge welders at two different geomembrane temperatures, two different geomembrane thicknesses, three welding speeds, and three welding temperatures. The 72 seams created were evaluated by conducting ASTM D 6392 peel strength tests at room temperature (22.8°C) and a burst test developed herein at three different sheet temperatures. This paper presents the test results, which illustrate the importance of welding temperature and speed. The test results are also used to develop a relationship between seam peel strength and burst pressure, which can then be used to conduct field burst tests to ensure the specified seam peel strength(s) are satisfied along the entire seam length instead of over the limited seam length used in destructive tests.