Geoelectrical and Geotechnical Investigations for Development of Superstructures at Nkpologwu Proposed Judiciary Site, Anambra Basin, Southeastern Nigeria

Abstract

Geophysical and Geotechnical surveys were integrally carried out at a proposed Judiciary site for civil development of superstructures in Nkpologwu, Anambra Basin, Southeastern Nigeria. Nkpologwu falls within 7 ̊06̍ '40” E to 7 ̊08 ' 42” E longitudes and 5 ̊56' 76” N to 5 ̊57' 78” N latitudes at about 320 m above the mean sea level. The study is aimed at interpreting the lithology of the subsurface at shallow depths in order to accentuate the competence of soil formations at the foundation depths of the site. Vertical Electrical Sounding (VES) data were acquired in the geophysical survey while various geotechnical tests were carried out to ascertain the bearing capacity of the site’s subsoil. The registered data from the VES survey were processed with WINGLET software hence, geoelectric models of at least four layers were obtained. Characterized by apparent resistivity values in the range of about 1524 to 96,561 Ωm. Geotechnical results showed values of 10.4% to 12.4% OMC, 1.95 to 2.01g/cm3 MDD, 30.0 to 39.0% CBR, 21.0 to 30.5% particle size distribution, <12% PI and <35%  LL Atterberg limit for soil samples within foundation depths at the site. Combined interpretation of the surveys showed that at foundation depths at the site were predominantly sand, laterite and sandstones delineated and these were found to meet the required standard of the Federal Ministry of works and housing for construction of superstructures. Therefore, the study provides the knowledge of the lithology and soil competence at foundation depths for future civil construction works at the site.