The long serviceability expectancy of civil engineering structures depends on the index properties and bearing capacity of the foundation soil. Therefore, the study of engineering behaviour of soil is extremely important during the design, construction and post construction phases of civil engineering projects. This study investigates the index properties of Sobe tropical red soil in relation to building foundation, embankment, and flexible pavement constructions. The study adopted geochemical analysis, in-situ cone penetration test, borehole logging, and geotechnical laboratory soil analysis using American Standard of Testing and Material. Findings revealed the USCS and AASHTO class of the soil to be CH – CL (medium graded soil) and A-7-6 respectively, signifying poor foundation material, of high compressibility and expansion, with intermediate - high plasticity. The soil is characterized by unit weight (av. 18.3 KN/m2), soaked CBR (av. 7%), cohesion (av. 26.4 KN/m2), angle of friction (18°), compression index (0.4489), compression modulus (2.78 N/mm2), coefficient of volume compressibility (0.7721 m2/KN), group index number (11.6), plasticity index (34.74 %). The material showed average bearing pressure of 111 KN/m2 at 1 m depth for building foundation. The average (av.) values of the major mineral oxides present in the samples are Na2O (av. 1.98 %), K2O (av. 2.54 %), Al2O3 (av. 18.79 %), Fe2O3 (av. 19.83 %), and SiO2 (av. 61.18 %). However, Al2O3, Fe2O3, and SiO2 constitute 95 % of the mineral oxides. The silica - sesquioxide ratio (Se) of the soil showed that all the soil sampled soil are lateritic with a range of 1.27 – 1.96 (av. 1.59). The soil has fair to poor stability for embankment slope, thin cores, blankets and dike sections. Thus using the group index and CBR design chart for flexible pavement, the combined thickness of base and surfacing should be 30 cm and 38.1 cm for sub-base/subgrade course. In conclusion, the soil required improvement or stabilization either with chemical (lime, cement, fly ash or asphalt) or by mechanical method, which would invariably reduce its plasticity/compressibility, and increase the shear strength and bearing capacity.
Primary Language | English |
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Subjects | Geological Sciences and Engineering (Other) |
Journal Section | Research Article |
Authors | |
Publication Date | July 4, 2022 |
Published in Issue | Year 2022 Volume: 4 Issue: 2 |