Characterization of Soils for Road Works: Case Study of Borrow Pits in Kwara State, Nigeria

Soil is the ultimate material for road construction and to ensure its suitability for construction. Therefore, its properties must be evaluated. Therefore, there is a need to determine the strength and evaluate the stiffness property of the soils for design and construction purposes. This study aimed to assess the strength and stiffness properties of lateritic soils within Ilorin that can be used for static and dynamic analysis of traffic loadings on roads/pavement structures. A laboratory test was conducted on soil samples collected from two identified borrow pits within Ilorin per BS 1377, and resilient modulus was estimated from California bearing ratio (CBR) value. From the preliminary investigation carried out on the soil samples, the soil samples at Oko-olowo pit are a silt clay with A-7-5 AASHTO classification. In contrast, the samples from Tanke pit are clay with A-7-6 AASHTO classification. The CBR and resilient modulus determined for the samples from the pits are 44.65% and 200.16 MPa and 56.40% and 233.50 MPa, respectively, indicating that the materials have road subbase characteristics that can be improved upon as base material. Therefore, the study recommends detailed soil investigation before the design and during construction of a road to ascertain the quality of the material employed.