In Nigeria, several billions of naira have been spent on road reconstruction and rehabilitation. Despite this, the roads fail almost immediately after the project is commissioned or even before. This phenomenal might be due to inadequate information about the subgrade properties of the roads. Hence, this study researches the behaviour of the subgrade soils under various conditions and classification of the soils. Laterite soil samples were collected from side-cuts along 5 roads (Ajagba Road, Akinmorin, Ajeigbe Afonja, Idi-Igba and Powerline Road) within Oyo East LGA. The study tests carried out include engineering soil classification test and soil engineering strength tests. The result showed the liquid limit ranges from 10.39 to 65.27 percent, plastic limit falls within the range of 0 to 43.5 percent. The percentage passing the sieve No 200, ranged between 10 and 67 percent. The specific gravity of the samples was between 2.11 and 2.51, while the soil samples have soaked CBR values ranging between 3 and 42.7 percent. The MDD recorded ranged from 1.45 to 2.14 g/m3 and the OMC for the samples ranged from 6.3 to 18.22 percent. Thus, this study concludes that some of the samples satisfy the condition for subgrade soil, while some did not.

Keywords : CBR, Side-Cuts, Subgrade, Engineering Soil Classification, Laterite