Flexible Pavement Assessment of Selected Highways in Orolu Local Government South - Western Nigeria

Abstract

This research aim at investigating the flexible pavement performance of some selected Highways in Orolu Local Government area of Osun State, South-western Nigeria. In order to achieve this, the study involved interview sessions with relevant parties, administering of questionnaires, site observations, Pavement Condition Rating (PCR) was adopted to place a numerical value on the state of some selected roads and geotechnical investigative studies of the selected Highways. Laboratory determination of design parameters, namely Atterberg Limits, particle size distribution, California Bearing Ratio (CBR) and compaction were carried out in accordance with BS1377 (1997) method of soil testing for Civil Engineers. Thereafter, the soil samples that have been collected from failed portions of some of these roads to determine the structural integrity of the underlying soil strata were classified using AASHTO and USCS classifications. Compaction test with Maximum Dry Density MDD between 1730.02 kg/m3 - 1960 kg/m3 and Optimum Moisture Content OMC between 13.05%-20.0% were also carried out. The values of California Bearing Ratio (CBR) of soaked soil samples were within the range of 4.60% and 20.69, while un-soaked soil samples fall within the range of 10.13% to 65.07%, these results shows that samples T1, T3, T5, T7, T8, T9 and T10 are all good as subgrade materials, while samples T2, T4 and T6 are poor subgrade materials and they could have contributed to the failure of their roads: AFP4 (Kelebe road), AFP7 (Elder Akande road) and AFP9 (Ile- Olode road).The PCR values ranged from 61.28 and 100. The results of laboratory tests and field observation produced herein indicates that the failure of pavements in Orolu Local Government Area, Ifon-Osun, Osun State, South-western Nigeria can be attributed to the following: Poor or no design, infiltration of surface runoff into underlying course, growth of shrubs and lack of effective routine maintenance by the concerned agencies.