ABSTRACT

The condition and adequacy of the highway is often _judged by the smoothness or roughness of the pavement, deficient pavement conditions can result in increased user costs and travel delays, unnecessary braking and fuel consumption, vehicle repairs and probability of increased crashes. Pavement failure is usually a result of several factors which includes traffic impacts on the road, environmental factors, poor maintenance culture, geotechnical characteristics of the subgrade and other road construction material, to mention a few. In this study, four failed segments of roads in the !kale local government area were selected for geotechnical studies. The following processes were cal'l'ied out: reconnaissance survey, interview sessions with relevant parties, site observations and geotechnical laboratory tests of road subgrade soil in accordance to B.S, 1377. The geotechnical investigation involved grain size analysis, atterbergs limits, West African compaction test, specific gravity determination, natural moisture content determination, permeability tests and california bearing ratio (CBR) test. Compaction test showed a maximum dry density range of2.0kg/m 3 to I .86kg/m3 and an optimum moisture content range between I 0.5% and 15%. The values of the California Bearing Ratio (CBR) of un-soaked soil samples were within the range of 38.4% and 80.8%. Furthermore, the sieve analysis revealed that a substantial percentage of the soil samples passed through the No, 200 BS sieve suggesting the soil consist mostly of silty clayey material, which translates to a fair material rating according to AASHTO design standard ( 1986). The permeability test result indicates tile samples are semi-permeable soils. From the tests result analysis of the Ikole-Omuo road stretch within the !kale local Government area it appears the subgrade materials under the failed and unfailed segments of the road is suitable according to AASHTO design standard. Therefore, rt is imperative that sustainable solutions addressing the issue of traffic impacts, adequate drainage provision, environmental factors and quality control should be focused on, to curtail the incessant occurrence of road failures on the lkole Omuo road stretch