Investigation of foundation bed's characteristics and environmental safety assessment in some parts of Bayelsa State, south-south Nigeria

The application of appropriate geophysical survey is very pertinent in planning for a successful development of civil engineering structures. In this study, an uphole seismic refraction survey and borehole logs were used to determine the foundation bed's characteristics for civil engineering development, while a portable gamma spectrometer was used to assess the environmental safety worthiness in some parts of Bayelsa State, Nigeria. The seismic refraction revealed a two-layer model, composing of an unconsolidated layer and a consolidated layer. The overburden thickness of the unconsolidated stratum varied from 2.2 to 7.5 m. The borehole logs showed alternating sequence of clay and sand up to a depth of 60 m. The radiometric survey revealed that thorium and the average radioactivity ratios of U/K, Th/K and U/Th are above the global standards by factors of 1.4, 6.4, 11.0 and 2.3 in sequence. Though the overburden in the study area is thin, it is advisable to excavate some aerated soil materials within the unconsolidated layer to minimize the effects of clay on the structure's foundation. Furthermore, periodic environmental safety monitoring and assessment is recommended in the study area.