Variability in the Geotechnical properties of some residual clay soils from southwestern Nigeria

Abstract — Some residual clay soils from southwestern Nigeria have been investigated with a view to elucidating their geotechnical prop-erties and determine the possible variations in these properties in relation to the sampling distance. Eight bulk residual soil samples from two test pits separated 30m apart at intervals of 0.5m up to a depth of 2.0m were analyzed in the la-boratory to determine specific gravity, grain size distribution, consistency limits, linear shrinkage, unconfined compressive strength and compaction characteristics. The data generated were subsequently subjected to statistical analysis. The investigations revealed that the soils are generally well graded, inorganic, with medium to high plasticity and hence compressibility and are of the same geologic origin. Statistical T-test showed no significant difference exists between the soils in terms of specific gravity, liquid limit, plastic limit, plasticity index, linear shrinkage, % clay size fraction, amount of fines, unconfined compressive strength and optimum moisture content. However the maximum dry density of the soils from both pits differed significantly. Although most of the parameters examined are not as varied and showed insignificant difference, the equations generated provide an op-tion in the estimation of properties considering the close sampling distance.