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The Port Harcourt Enugu expressway is part of a national road grid that links parts of southern and northern Nigeria. The severe pavement failure between Umuahia and Okigwe section of the expressway covering a distance of about 30 km was investigated by geotechnical and mineralogical assessment of disturbed and undisturbed samples of the underlying...
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The mainly white-yellow marly soils studied present medium degree of consolidation and induration. The predominant grain size of the non - carbonate constituents is that of silt varying from 34 to 64%. According to the textural classification of soils of the SSDS the samples are mainly silty-clay loams with moisture capacity 30-40%. In the untreate...
Citations
Many cases of road failures have been reported by experts in Nigeria from North to South, East to West. Most of these roads are in a deplorable condition and professionals have attributed it to a number of causes. This study reviewed causes of failure of roads in Nigeria and categorized them into lack of careful and diligent geotechnical studies, inadequate knowledge of geology of the area, and other conditions. Roads that have failed due to lack of proper geotechnical studies include; Awotan-Akufo, Sagamu-Papalanto highway, Onitsha-Enugu Expressway and Akoko highway. Geotechnical studies provide information on the physical and mechanical properties of soil or rock around or brought to the construction site. Some roads have failed as a result of improper consideration of geology for instance the Shagamu -Benin expressway, Lagos- Ibadan expressway, Ibadan -Ife, Osogbo -Iwo expressway, Abakaliki area and Port Harcourt -Enugu expressway. Roads are founded on geologic earth materials and are greatly controlled by geology; hence, geology is very important in road construction. Other conditions such as old age, inadequate maintenance, poor design and construction, lack of drainage, use of poor and substandard materials, and heavy traffic have also led to road failures. Despite the absence of definite statistics, most experts agree that the rate of roads failure have increased in recent years in Nigeria. There is strong evidence to suggest that while geotechnical processes are becoming better controlled and more reliable, failures of small, medium and big scale geotechnical works such as roads continue to arise with embarrassing frequency in the country.
Poor geotechnical and mineralogical properties of soils used for road construction are a significant factor responsible for pavement failures. This is because most soils encountered at failed portions of some pavements do not meet the specifications according to relevant standards. It is with this in mind that this study carried out a systemic review on some residual soils in Nigeria, with a focus on their locations, geotechnical, and mineralogical properties in comparison to standards specified in the Nigerian specification for road and bridges. This study also reviewed how these properties have contributed to various road failures in different regions of the country. It was observed that the geotechnical and mineralogical properties of most residual soils in some regions of Nigeria did not meet up with the standards stipulated by the Nigerian Specification for road materials. Reviews carried out on the place of geotechnical and mineralogical characteristics on various road failures in Nigeria showed that a high volume of research works was carried out in the south-western and southeastern parts of the country compared to the Northern region.
