Evauation of road failure along an erosion prone highway in ogun state southwestern nigeria using integrated methods

This study investigated a road failure on an erosion prone highway of Sagamu-Papalanto southwestern Nigeria. The mineralogical and chemical composition of the soils were analyzed using X-ray diffraction and X-ray fluorescence methods. The geotechnical properties of the soil such as grain size distribution, consistency limits test, specific gravity, compaction, California bearing ratio (CBR), porosity, permeability, shear strength test and cone penetrometer test were also conducted on the soil samples. The results of the investigation showed that the moisture content, specific gravity, liquid limit, plastic limits and plasticity index ranged from 9.4–18.2%; 2.54–2.58; 26.8–42.6%; 18.2–25.2% to 7.1–21.6%, respectively. Grain size distribution showed the fine and coarser fractions range from 12–32.5% to 49.4–80.5%, respectively. The maximum dry density and its optimum moisture content ranged from 1.64–1.74 g/cm 3 to 12–17%, respectively. CBR results ranged from 3 to 12%. The class of subsoils namely A-26, A-7, A-2–7 (clayey soils), were identified and rendered unsuitable as road construction materials. The results from this investigation revealed that the subsoils are poor road construction materials due to its fines and plasticties. This should be put into consideration during the reconstruction and rehabilitation of the road.