Geotechnical characterization and suitability analysis of soil underlying solid waste dumpsite in southwestern Nigeria

Soil servers as natural containment medium that influences leachate migration, contaminants attenuation for the stability of waste disposal system. Soil selection for dumpsite should emphasize adequate clay properties, low hydraulic conductivity, favorable plasticity, geotechnical analysis and chemical properties. This research aimed to determine the geotechnical characteristics of Ilokun dumpsite underlying soil in Ado-Ekiti to access its suitability in preventing the migration of the leachate within the environment. Three (3) Soil samples were randomly selected while samples were collected at 0-0.5 and 0.5-1.0m depth within the dumpsite at different locations using trial pit method, air dried, sieved using 2 mm mesh. Each of the pits were dug by hand excavation and samples were collected from pit of 1.0 X 1.0m, while laboratory tests were conducted on the soil samples. Soil index properties and classification test such as particle size distribution, specific gravity, Atterberg limits and permeability test were performed on the samples. All the tests were conducted according to BS 1377:1990. Particle size distribution results show that; the percentage fines of the underlying soil samples are predominantly below 50 % except 1B. A standard value of fines greater than 50 % (≥ 50 %) was specified for clay liner material as reported by CGRM (2007). The values of the Liquid limit of the underlying soil ranged from 19.57 to 27.80, Plastic limits ranged from 10.13 to 24.25 and the Plastic Index ranged from 2.23 to 12.23 respectively. The analysis revealed that the Liquid limit of the soil samples are below 30% and Plastic Index of the soil samples are below 20%. The underlying soil results is indicative that the soil is predominantly coarse-grained and is unsuitable as a liner material.