Field studies and excavations of geosynthetic clay barriers in landfill covers
Stefan Melchior
Abstract
Geosynthetic clay barriers (GCB) are widely used in landfill covers and other applications. In 1994, a large lysimeter study was started on the German landfill Hamburg-Georgswerder to test the performance of GCB under field conditions. Two lysimeters with an area of 100 m2 each were integrated in the landfill cover to measure the leakage through a needle-punched and a stitch-bounded geosynthetic clay barrier under a cover of 30 cm topsoil (sandy loam) and 15 cm drainage layer (gravel). Three other products – one with a geomembrane/bentonite GCB – were installed under similar cover conditions in smaller control plots. In the years 1995, 1996, 1998 and 1999 several very intensive excavations were carried out in order to control the quality of the GCB visually, by taking samples for chemical, physical and mineralogical laboratory tests including e.g. the determination of ion exchange and permittivity. The samples were x-rayed and specimen were prepared to take thin section images and electron microscopic images. The results of the study show that under a shallow cover desiccation, cation exchange, plant root penetration and shrinkage have increased hydraulic conductivity of the tested GCB very much. No significant decrease of the leakage rates has been observed after re-wetting and swelling of the Bentonite.