Geotechnical Assessment of Pavement Failure along Lagos-Ibadan Expressway

Abstract

Pavement failure has contributed immensely to loss of lives, disruption to normal daily activities and increase amount of money being spent on maintenance annually. One of the causes is associated with inadequate investigations on subgrade materials. This study aimed at examining the geotechnical parameters as factors of pavement failure along Lagos–Ibadan Expressway. Samples were collected at the failed and stable portions on some selected road segments and subjected to laboratory tests including Natural Moisture Content (NMC), Linear Shrinkage(LS), particle size distribution and California Bearing Ratio(CBR). The NMC along the failed sections was on the high side (ranged from 13.11% to 26.89%) compared with the stable sections (ranged from 11.11% to 16.40%). Most of the tested soils have percentage passing 0.075mm sieve more than 35% maximum required by the Federal Ministry of Works and Housing for subgrade materials. The maximum dry density(MDD) for the samples at failed and stable sections ranged from 1550 kg/m3 to 1860 kg/m3; 1650 kg/m3 to 1980 kg/m3 respectively while the Optimum Moisture Content(OMC) ranged from 8.30% to 20.30%. The soaked CBR values ranged from 2% to 17% while the unsoaked values ranged from 4% to 25%. The increase in NMC along the failed portions could be as a result of high water table along these sections. Some of the materials at failed locations had values of LS > 8% which suggests high susceptibility to shrinkage and swelling which results in differential settlement and contributed to pavement failure along these sections of the road. Keywords: Geotechnical, Pavement failures, subsurface investigations, Expressway, subgrade materials.