Journal of Earth Sciences and Geotechnical Engineering

Geoelectrical and Geotechnical Evaluation of Foundation Beds at Naze, Owerri Southeastern Nigeria

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• Abstract

  A foundation study has been undertaken at a proposed building site located at about 3km east of Owerri, along Aba-Owerri road, between the Nekede Mechanic village and the Naze/Nekede road junction. The aim of this study is to examine the Geoelectrical and Geotechnical parameters that can be used to evaluate the stratigraphy, nature, structural disposition/integrity and competence of the shallow section of the subsurface for construction purposes and building development. The Vertical Electrical Sounding (VES), using schlumberger configuration and soil analysis techniques were adopted. A total of six (6) Vertical Electrical Sounding (VES) stations were occupied and this was complemented with geotechnical analysis of six soil samples collected at all the VES points down to a depth of 2m within the study area. Quantitative interpretations of the VES curves were carried out using partial curve matching technique and computer iteration technique. The investigation delineated four geologic layers which include the Sandy and Organic-rich top soil, Iron-stained sand, Medium-grained sand and Gravely sand. The topsoil composed mostly of sand and laterite with resistivity generally greater than 350Ωm. The layer (topsoil) with thickness that varies from 1.4–5.8m constitutes the layers within which normal civil engineering foundation is founded. There are no indications of any major structures such as faults, fractures and lineaments down to a depth of 40m that could be deleterious to engineering construction in the area. All the determined geotechnical parameters of the subsoil fall within the specification recommended for foundation material by FMWH, 1972 and are generally increasing towards the southern part of the area. From the results, we conclude that soil units between 0.0-2.0 meters (0-6.6 feet) are characterized by very high bearing capacity of values ranging from 381 to 524 KN/M². The deduction from the above is that, the topsoil formation may be rated as relatively good as a foundation material. The foundation of the proposed civil structure can be hosted by this formation.