Shear strength characteristics of PVC Geomembrane-Geosynthetic interfaces

Torsional ring shear and large-scale direct shear tests were conducted to investigate the shear behavior of polyvinyl chloride (PVC) geomembrane-geosynthetic interfaces. Specifically, the smooth and faille-finished sides of a 0.75 mm-thick PVC geomembrane were sheared against five different nonwoven geotextiles, a drainage composite, a geonet, and an unreinforced geosynthetic clay liner (GCL). Test results indicate that the smooth side of the PVC geomembrane yields a higher interface shear resistance than the faille-finished side due to the larger contact area and higher pliability of the smooth side. The interface shear behavior of the PVC geomembrane is compared to that of a high density polyethylene (HDPE) geomembrane and two very flexible polyethylene (VFPE) geomembranes. Faille-finished PVC geomembrane-nonwoven geotextile interfaces experience a post-peak strength loss of less than 25% at normal stresses between 100 and 400 kPa and no post-peak strength loss at normal stresses of 50 kPa and below. This behavior is attributed to the pliability of the PVC geomembrane, which enables (i) the geomembrane surface to be roughened, (ii) the other interface component to embed into the geomembrane as shearing progresses, and (iii) no texturing to be used that can damage the overlying geosynthetic. The effects of nonwoven geotextile fiber type, mass per unit area, and calendering on PVC geomembrane-nonwoven geotextile interface strength are also investigated.