GEOTECHNICAL INVESTIGATION OF CLAYEY-SOIL: A CASE STUDY OF SELECTED SPOTS IN ITESIWAJU LOCAL GOVERNMENT AREA, NIGERIA.

Abstract

Itesiwaju, the study area, is a prominent Local Government Council in Oyo State of Nigeria. A detailed geotechnical investigation was carried out on deposition of clayey-soil in the selected study area through physical observation, field survey and laboratory analysis in line with existing Standards. Seven (7) popular towns (Out-the Council’s Headquarter, Ipapa, Igbojaye, Okaka, Komu, Oke-Anu and Baba-Ode) were considered in the sampling exercise. A representative sampling point was taken from each of the major towns in the study area, all of which revealed well graded soil particles (Gravel-between 7 and 25% Sand-11 to 18% while fines ranged from 64 to 78%). Grading the samples with the American Association of State Highway and Transportation Officials (AASHTO)’s standard, it was discovered that the particles all belonged to A-4, A-5, A-6 and A-7 group. Also, the plasticity Indices of samples from Ipapo and Komu fell into A-7-6 group, while the rest belonged to A-7-5 group. Samples from Oke-Amu, Komu and Baba-Ode have low swelling potentials while those from Ipapo, Okaka, Out, and Igbojaye have medium swelling potentials when compared with standards. All samples were of high plasticity values when measured with Casagrande’s plasticity chart. In addition, all analyzed samples have relatively high moisture contents, low dry densities and considerably moderate California Bearing Ratio (CBR) values. These are all pointers to the fact that the clay material contents in the study area are high, pure, and plastic which are useful for industrial applications.