Abstract
This research investigates the index properties of a residual soil profile at Bosso campus of the Federal University of Technology, Minna. A trial pit was dug to a depth of 3 m and disturbed soil samples were taken at depths of 0.5, 1, 1.5, 2, 2.5 and 3 m respectively. Natural moisture content (NMC) test, Atterberg limit test, mechanical sieve analysis and hydrometer test, specific gravity and standard proctor compaction test were carried out on each sample. By visual inspection it was observed that the soil profile consists of three layers; light reddish at the top, reddish soil at the middle and whitish soil at the bottom respectively. The natural moisture content increased from 2.3 % to 15.3 % at 0.5 m to 1.5 m depth and decreased to 11.8 % at 2 m depth after which it increased to 15.8 % at 3m depth. Using the unified soil classification system (USCS), the top and middle layer were classified as well graded sand (SW) while the bottom layer was classified as clayed sand (SC). The optimum moisture content (OMC) decreased from 10.8 % to 7.2 % at 0.5 m to 2.0 m depth then increased to 7.8 % at 2.5 m depth and decreased to 7.2% at 3 m depth. The maximum dry density (MDD) decreased from 1.99 Mg/m3 to 1.92 Mg/m3 at 0.5 m to 1 m depth, it increased to 2.1 Mg/m3 at 2 m depth, it then decreased to 1.95 Mg/m3 and increased to 2.1 Mg/m3 at 3 m. Based on these investigations, the index properties of the residual soil profile of the pit varies with depth.