Relationship between road pavement failures, engineering indices and underlying geology in a tropical environment

Abstract

This article presents the results of a study carried out to relate the frequency of pavement failures, the engineering indices of the subgrade materials and the underlying geology. The results show a high variability in the indices such as the liquid limit, LL, the plasticity index, PI, the maximum dry density, MDD, the optimum moisture content, OMC, compressibility and the California Bearing Ratio, CBR, between the different geologic units. Engineering indices having significant correlation with CBR (the major criteria for assessing the quality of subgrade materials), are used to develop a scheme for evaluating the materials at different failure points along the Calabar-Itu Highway in Nigeria. The evaluation shows that locations exhibiting high failure rates are underlain by shaly or marly subgrade whereas locations characterised by low failure rates are underlain by weathered basement or sandy unit as subgrade. It is recommended that maintenance and provision of drainage facilities will go a long way to reducing the rate of failure.

Keywords: engineering indices, failure, road pavement, subgrade, Nigeria

Global Journal of Geological Sciences Vol. 3(2) 2005: 99-108