Abstract:
Indiscriminate disposal of wastes generated by the increasing human population and industries pollute surface and groundwater, consequently creating health hazards. An evaluation of five areas in Akure, southwestern Nigeria were undertaken to investigate geotechnical properties of charnockite derived soil for use as isolation barriers and necessary in assessing site suitability for waste disposal. Geotechnical parameters namely, grain size distribution, consistency limits, permeability and consolidation were also obtained, to determine the index and engineering properties of the soil from different horizons for engineering classification purpose, determine the effect of pH on permeability and consolidation properties of soil samples and to generate baseline information on soil vulnerability. The soils possessed amount of fines 26.8 - 86.2% a and clay content (8.8 – 68.3 %) that are within the minimum 30 % and 10 % respectively, considered adequate for a landfill site. Furthermore, they are well graded exhibiting medium to high plasticity, compressibility and consolidation with plastic index of 4.4 to 36.0%. the volume of compressibility 0.330m2/MN to 0.836m2/MN and coefficient of consolidation of 4.23m2/year to 4.45m2/year. The compaction curve showed Sample N2A achieved higher ρdmax at lower moisture content when compared with the rest of the samples. However, the coefficient of permeability of the soil samples leached with the pH values 5, 7 and 9 range from 10-10 to 10-11m/s which are within the maximum requirement of 10-9m/s recommended for soils. The coeffient of permeability of the studied soil samples established that the samples were only suitable for alkaline medium and unsuitable for waste that capable of generating neutral or acidic leachates. This suggested that charnockite derived soil in Akure is only suitable for the leachates that is alkaline in nature or alkaline
contaminated environment. It is therefore recommended that in-situ compaction, lining and addition of bentonite be done on the unsuitable samples to improve their barrier ability
