This investigation evaluates the engineering behavior and near-surface ground conditions of residual soils developed along the Ado–Akure segment of the F209 highway in Ondo State, southwestern Nigeria, with the objective of producing dependable geotechnical data for informed pavement design and performance assessment. Both field and laboratory analyses were conducted. Field investigations comprised detailed geological mapping and in-situ strength evaluation using the dynamic cone penetrometer (DCP). The predominant bedrock comprises Charnockite (Ch) and Granites, including intermediate and large crystals feature texture. This implies complex and discrete stages of crystallizations. Two distinct geomorphological terrain s were observed. Soils derived from Charnockite exhibited the highest fine and clay contents, as well as water content (WC), subsequent by OGe and OGp-derived soils. Based on plasticity classification, Ch-, OG, and OGp-formed soils were categorized as CH, CI, and CL, respectively. Laboratory and field assessments indicated that OGp-derived soils possess less best water content (BWT) also peak maximum dry density (MDD), highlighting their superior densification potential, whereas Ch-derived soils showed the opposite trend, reflecting suboptimal compaction characteristics. DCP outcome showed that soil formed from Charnockite exhibited the most penetration index, indicating lower resistance and shear strength, while OGp-derived soils recorded lowest penetration index sounding data. Statistical correlation confirmed a strong and significance consequential association of laboratory (CBR) and field CBR measurements. Overall, granite-derived soils displayed more favorable engineering properties compared to Charnockite-derived soils, attributable to variations in textural, mineralogical, and geotechnical characteristics.
