ASSESSMENT OF SUBSURFACE PROPERTIES FOR PRE-FOUNDATON INVESTIGATION AT NIGERIA UNION OF TEACHERS HOUSING ESTATE SITE, PAGGO, MINNA, NIGERIA

Abstract

The vertical electrical sounding (VES) was carried out to evaluate the subsurface properties of Nigeria Union of Teachers housing estate, Paggo, Minna for pre-foundation investigation. The Abem terrameter model SAS 4000 was used to determine the subsurface layer parameters (resistivity, depths and thickness) that were employed in evaluating the properties of subsurface. A total of sixty VES points were sounded with interval of 100 m apart. It has a maximum current electrode separation (AB/2) of 100 m. Three and four geoelectric layers were observed namely; topsoil, weathered layer, fractured layer and fresh basement layer. The strata sequence of the subsurface shows: topsoil (67.5 – 941.2 Ωm), weathered layer (65.84 – 1199 Ωm), fractured layer (118.9 – 886.8 Ωm) and the fresh basement layer (1094 – 8692 Ωm). Ten VES stations were recommended for building construction where basement is intruded close to the surface, with depths to fresh basement varying between 1.575 and 3.825 m (shallow depths) and have high resistivity values of the fresh basement.