GEOTECHNICAL INVESTIGATION OF SOILS IN AKURE METROPOLIS AS MATERIALS FOR FOUNDATIONS

Abstract

There have been recent cases of building collapses in Nigeria. Many of these collapses are in newly developed areas of towns and cities. Post-collapse investigations have shown that majority of the collapses relate to poor foundations as well as faulty design and faulty construction (both of materials and processes). Urbanization, population pressures, and the need for housing has led to the expansion of cities into areas hitherto considered as relatively unsafe. Akure (southwestern Nigeria) has been experiencing such rapid population growth, expansion, and change in land use over the years, especially since it became the state capital in February, 1976. The growth has led inhabitants to build in relatively unsafe areas, namely, areas around river and stream channels, areas with poor sub-soils, and steep slopes. In view of this expansion and land use change in Akure coupled with the recent cases of building collapses in Nigeria, there is need for engineering geological planning of Akure. This work was therefore aimed at determining the geotechnical properties of soils of Akure metropolis as materials for foundations (both buildings and roads). This was determined by investigating the index properties and strength characteristics of the soils by carrying out laboratory tests, namely, natural moisture content; specific gravity; bulk density for undisturbed samples; particle size distribution; consistency limits; compaction; consolidation; and triaxial shear strength tests. The soils were classified according to the Unified Soils Classification System and the American Association of State Highway and Transportation Officials’ (AASHTO) system of classification. Based on the geotechnical parameters derived, it looked at the suitability of the soils initially as well as with progress of urbanization. Since soils are formed as a result of the weathering of parent rocks, the influence of parent rock on the geotechnical properties of the derived soils was also considered. The empirical relationships between paired geotechnical parameters were determined using