Geoenvironmental study of hydraulic and mechanical properties of waste containment base barriers

M.Phil. (Civil Engineering)The challenge of buried domestic solid wastes in landfill sites is viewed from the perspective of leachate migration and contamination in the substrate. Generally, this happens through the passage of the contaminant into the barrier lining material. The use of mineral liners as useful economic containment component has resulted in the assessment of their efficiency as barrier materials and in the attenuation of migrating contaminant species. To evaluate the potential use of mineral liners as containment base barriers to domestic waste, natural occurring soil samples from three different waste disposal sites in City of Johannesburg, South Africa were collected and studied. Bentonite-GCL was tested to serve as a bench mark for the three different tested soil samples. The various chemical constituents of the landfill leachate were determined from samples taken from the basins designed to collect the leachate from the respective landfill sites. In this study, series of tests on geocomposite liners under the effect of leachate flow through circular geomembrane defects and tests without geomembranes were conducted in a small-scale model device. A 24mm thick soil barrier layer underlain a 2mm thick polyethylene plastic with centred 5mm hole to simulate defected geomembrane and a 225mm thick attenuation layer (AL) in line with the American Society for Testing and Materials (ASTM) D-3776 and D-5084 constituted the model setup. The model device, a Modular Consolidometer-Percolation Column Hybrid with 160mm diameter was placed on a loading frame capable of applying over 500kPa pressure to the composite barrier..