Assessment of flexible pavement of selected highways in Odo-Otin Local Government South-Western Nigeria

This paper presents the result of assessment of flexible pavement of selected highways in Odo Otin Local Government Area, Osun State, South-western Nigeria. In order to achieve this, the study involved site observation, Pavement Condition Rating (labeled TP1-TP7), identification of types of failures or distress on the pavement, drainage assessment and geotechnical studies of the selected Highways. Soil samples were collected from both the unfailed and failed section of the selected roads. The samples were subjected to the following laboratory tests; natural moisture content, sieve analysis, atterberg limit, specific gravity, compaction test using West African standard, unconfined compressive strength and California bearing ratio. The study revealed that PCR rating scales for TP4, TP6 and TP7 were in a good condition due to the fact that there was less distress on the road. TP3 and TP were in a satisfactory condition. TP1 and TP2 were observed to be in a poor condition. Only road TP6 and TP7 have effective drainage, but can be predicted for them to have blockage or erode other roads in the nearest future due to no discharge outlet. For other roads, they have no drainage which leads to major causes of some distress all around those roads. The unconfined compressed strength ranges between 41kN/m2 and 181kN/m2 and the CBR value between 26.8% and 59.6%. The result therefore shows that most of the failures are caused by the following: design inadequacies, inadequate drainage facilities, infiltration of surface runoff into underlying course, growth of shrubs and base failure.