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 ≤۳۵% passing sieve #۲۰۰. The liquid limit ranges from ۲۲%-۴۷%, the plastic limit from ۱۴%-۳۱%, and the plasticity index range from ۶%-۱۸%. The values of the optimum moisture content using the West African Compaction (OMC-WAS) methods ranged from ۶.۶%-۱۱.۵%, with maximum dry density for WAS (MDD-WAS) from ۱۸۶۲ kg/m۳-۲۰۶۱ kg/m۳ while the optimum moisture content using the modified AASHTO methods (OMC-MAS) ranged from ۷.۰%-۱۱.۶% and maximum dry density for MAS (MDD-MAS) from ۱۹۳۲ kg/m۳-۲۱۷۴ Kg/m۳ respectively. CBR for unsoaked soil samples ranged from ۱۰۰%-۲۴۹% and for soaked samples, ۷۰%-۱۱۹% respectively. The soils are classified into three groups based on AASHTO classification as A-۲-۴, A-۲-۶, and A-۲-۷ 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.

Keywords:

Geotechnical properties , Sub-base , Base course , Subsurface Soils , Road pavement