Geo-engineering Properties of subsurface Soils in parts of Northcentral Nigeria: Implications for Construction of Road Pavements

Due to the persistent failures of road pavements and scarcity of suitable materials for use as fill for road constructions, geotechnical investigations were conducted to characterize and select suitable sites that subsurface soils can be obtained for road construction purposes in the study area. This involved collection of sixteen soil samples from four selected sites. The geotechnical methods deployed include sieve analysis, liquid limit and plastic limit determinations, compaction tests, and, California Bearing Ratio tests (CBR). The particle size distribution curve (PSD) showed ≤35% passing sieve #200. The liquid limit ranges from 22%-47%, the plastic limit from 14%-31%, and the plasticity index range from 6%-18%. The values of the optimum moisture content using the West African Compaction (OMC-WAS) methods ranged from 6.6%-11.5%, with maximum dry density for WAS (MDD-WAS) from 1862 kg/m3-2061 kg/m3 while the optimum moisture content using the modified AASHTO methods (OMC-MAS) ranged from 7.0%-11.6% and maximum dry density for MAS (MDD-MAS) from 1932 kg/m3-2174 Kg/m3 respectively. CBR for unsoaked soil samples ranged from 100%-249% and for soaked samples, 70%-119% respectively. The soils are classified into three groups based on AASHTO classification as A-2-4, A-2-6, and A-2-7 which classifies the soil as gravelly clayey or silty sand. The site investigated is, therefore recommended suitable site for obtaining good to excellent materials for use as fill (bass and sub-base) materials to enhance quality of road pavement construction in the study area.