Reductions in GCL Overlap Beneath an Exposed Geomembrane

AbstractReductions in geosynthetic clay liner (GCL) panel overlap are reported for two needle-punched and thermally treated GCLs (GCL1 and GCL2) and compared with values for two other needle-punched but not thermally treated GCLs (GCL3 and GCL4) at the same field-scale test site. The GCLs were covered only by a black geomembrane and otherwise left exposed to study the implications of leaving the composite liner exposed for nearly 5 years on reductions in the overlapped seams between adjacent GCL panels. It was found that all but GCL2 experienced a significant reduction in overlap. After 4.8 years, GCL2 experienced the smallest overlap reductions of only 30 mm (i.e., 90% of the initial 300 mm panel overlap remained), GCL3 overlaps were reduced by 75 mm, whereas GCL1 and GCL4 had the largest reductions with values greater than 600 and 400 mm, respectively, after 4.8 years. Overlap reductions appear to correlate with reference water content and overlap adhesion, which are two laboratory indices affected by confinement and texture of the four GCLs resulting from subtle, but, distinct differences in the method of manufacture.