ENGINEERING PROPERTIES OF SOILS IN NORTHEASTERN IBADAN IN RELATION TOPERFORMANCE AS ROAD CONSTRUCTION MATERIALS

The geotechnical properties of solid within the northeastern parts of Ibadan were determined and related to their suitability as road constr uction materials. Most of the soil samples fell within the SP group wh ile a few were classified as SW and SP-SM groups under the Unified Soi l Classification System. Grain size analysis show that most of the mat erials were poorly graded. Atterberg limit tests defined a generally l ow plasticity range with plasticity indices ranging from 0-18%. Unsoak ed CBR results ranged from 16-198%, while soaked CBR-values were from 6-75%. Consolidated undrained direct shear tests as determined for the SP, SW and SP-SM groups of soils gave a range of cohesion values of 3 5-42 KN/m2 and phi values of 29-30-degrees. Most of the other soils wi thin the study area, in their natural states, did not meet most of the requisite engineering criteria for road construction purposes. Their natural properties needed to be improved upon, probably by stabilizati on processes.