Fines content for optimum stability within coastal dune sands within Northern KwaZulu-Natal, South Africa

This paper describes the results of geotechnical and geochemical laboratory tests, carried out on dune sands from northern KwaZulu-Natal, to which increasing percentages of fines (<63 μm) were added. The geotechnical tests detail the effects of the fines content on a number of properties of the dune sands, such as the permeability, maximum dry density and shear strength. The peak shear strength and dry density of the dune sands occurs when 20-30% fines were added, whilst the permeability was seen to decrease continuously with increasing fines. Compaction of the samples was seen to significantly increase the shear strength of the dune sands together with a corresponding decrease in the permeability. The results from these tests enabled slope stability analysis to be carried out. Typical fines used in the geotechnical tests were analyzed by XRD, and the clays were isolated and their morphology studied using a transmission electron microscope (TEM). Fines identified include kaolinite, quartz, montmorillonite, calcite, feldspars, iron-oxides and illite. The fines content of the dunes sands has been shown to profoundly effect the geotechnical properties of the dune sands. © Springer-Verlag 2004.