EXAMINING GEOTECHNICAL AND GEOCHEMICAL PROPERTIES OF LATERITIC SOIL PROXIMATE TO MIGMATITE
Abstract:
This study investigates the geotechnical and geochemical attributes of lateritic soil formations developed on migmatite formations along the Ogbomosho-Ilorin road in southwestern Nigeria. Laboratory analysis of soil samples from seven distinct laterite profiles, obtained from road cuts, was performed to assess the geotechnical, geochemical, and petrographical features of each horizon within the profiles, with a focus on their suitability for construction and foundation purposes.
Geotechnical tests, conducted following British standard procedures (BS 1377), encompassed index and performance tests. Field geological mapping revealed that the parent rock giving rise to the in-situ lateritic soil was migmatite, with an average soil profile depth of 4.2 meters. The primary mineral composition of the migmatite included quartz (40%), biotite (25%), feldspar (21%), hornblende (6%), and muscovite (5%). The moisture content ranged from 3.1% to 14.2%, specific gravity from 2.50 to 2.74, bulk density from 1.44 to 1.77 g/cm³, and dry density from 1.31 to 1.62 g/cm³, with average values of 1.56 g/cm³ and 1.44 g/cm³, respectively. These results indicate that the soil resulted from in-situ weathering of granitic rocks rich in felsic minerals.
The Atterberg consistency limits ranged from 3.3% to 14% for plastic limit (PL), 40% to 58% for liquid limit (LL), and 17.7% to 35% for plasticity index (PI), with average values of 47.2%, 49%, and 8.1%, respectively. The plasticity chart indicated that the soil falls above the A-line, corresponding to the CL zone, classified as inorganic clay with moderate plasticity according to the Unified Soil Classification System (USCS). Grain size analysis showed fine to coarse-grained sand with particles above 0.075 mm.
The Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) averaged 13.08% and 1.76 kg/m³, respectively. The California Bearing Ratio (CBR) values for soaked and unsoaked conditions ranged from 17% to 66% and 42% to 74%, with average values of 57.58% and 34.8%, indicating suitability for sub-base and subgrade in road pavement construction. The angle of friction (ϕ) and cohesion (C) ranged from 22° to 32° and 10 kN/m² to 30 kN/m², with average values of 27.04 and 21.5 kN/m², suggesting the soil’s potential use in road embankment construction.
X-ray fluorescence analysis identified major oxides, including SiO2, Fe2O3, Al2O3, K2O, Na2O, TiO2, and MgO, with SiO2, Fe2O3, and Al2O3 constituting 70% to 80% of the oxides.
Overall, the study findings indicate that, except for Horizon A and C of the profile, the geotechnical and geochemical characteristics of the lateritic soil derived from migmatite align with the guidelines set by the Nigerian Federal Ministry of Works for road construction materials and are consistent with the results of other research. Sectional failures may have arisen from improper material handling and equipment limitations.
EXAMINING GEOTECHNICAL AND GEOCHEMICAL PROPERTIES OF LATERITIC SOIL PROXIMATE TO MIGMATITE. GET MORE, ACTUARIAL SCIENCE PROJECT TOPICS AND MATERIALS
