Engineering assessment of Lateritic soils of Obiaruku highway sections in South-southern, Nigeria

Abstract

In order to determine the suitability of lateritic soils for the paving structures of highways, an engineering examination of some numbers of unsuccessful routes and highways in Obiaruku, southern Nigeria, was conducted. Thirty-two (32) lateritic bulk soil samples were taken for road construction-related index and strength testing from three stable and five failing sections. Compared to soils from the failed parts of A-7-6, which indicate poor-quality sub-grade materials, the soils from the stable sections have a greater specific gravity (2.49–2.85) and a lower percentage of clay (23.90%), indicating A-2-6 on the AASHTO classification system. Pores water pressure developed as a result of the high water absorption capacity, high proportion of fine particles (> 40%), and high values of linear shrinkage (> 8%) of the majority of soils from failed sections, leading to a loss in soil index strength. The degree of instability observed is caused by the predominance of fines in lateritic soils, low California bearing ratio (16–39% un-soaked), intermediate and high OMC above recommendation for most soil samples (12.6–19.1), maximum dry density (MDD) (<2000 kg/m3), and liquid limit (35.1–53.0). The lateritic soils of failed sections have poor geotechnical qualities, which suggest that they are not appropriate for use as sub-grade materials in other engineering constructions or even in the construction of new roads. For an accurate assessment of the sub-grade soils for highways, the significance of lateritic soils in detail sampling is emphasized. The findings of this study will be helpful in the rehabilitation and reconstruction of the road's failing parts, and it is advised that this investigation be well documented for future use.