Influence Of Geology On Pavement Performance: A Case Study Of Shagamu-Benin City Road, Southwestern Nigeria

Abstract

The Shagamu-Benin city Road, a major link highway to the commercial capital of Nigeria in southwestern Nigeria is oriented approximately east-west and traverse geologic formations with extremely variable engineering properties. Field and laboratory investigations which involved geologic mapping, auger boring, sampling and laboratory testing were carried out to determine the stratigraphy and geotechnical properties of the sub-grade and their relationship to the pavement condition.

Field observation indicated that the road may have been based on a single design concept, without due consideration to the influence of geology on the performance of the pavement. The laboratory testing indicated in-situ dry density ranging from 1717 kg/m3 to 2085 kg/m3 in the lateritized zone in Edo state, and from 1678kg/m3 to 1970kg/m3 in the micaceous sections of Ondo state. The soaked CBR values for sub-grade materials of the Ondo section are accordingly low (3% to 6%), while the CBR values for the Edo state section which is reasonably drained is modestly high (2% to 16%). The low CBR values exhibited by the Ondo state section indicated that the sub-grade had a weak bearing strength and was susceptible to erosion on exposure to precipitation or surface runoff, thereby encouraging and exacerbating rutting and deformation of pavement.

KEY WORDS: Geology, Road failure and Performance.

Global Journal of Geological Sciences Vol.3(1) 2005: 17-24