Engineering-geological properties of subsoil of Yenegoa in Niger Delta, Nigeria

Abstract

The major aim of this research work is to determine the stratigraphy and engineering geological properties of foundation subsoils of Yenagoa, the fast growing capital city of Bayelsa state in the Niger Delta, which can be used as reference database for future infrastructure and environmental development of the area. A total of six (6) boreholes were drilled to depths of about 20m and soil samples were subjected to several geotechnical tests (including natural moisture content, particle size distribution, plasticity, bulk density, specific gravity, organic content, shear box test, consolidation,
etc). The study revealed that the subsoil profile from 0 - 20m, essentially consists of an organic clayeysilt top layer, a middle sand stratum and a gravelly-sand at the bottom. There are great variations in the values of the geotechnical index properties of the soils hence the geotechnical data of one location cannot be used as a basis for design of foundation in other locations. The top organic silty clay horizon can only be considered as foundation substratum for very small/light civil engineering structures whilst the sand and gravelly- sand horizons constitute the best foundation substratum for
medium and large civil engineering structures.