Evaluation of the layering of rock strata and basement rock depth of a university teaching hospital premises in northern Nigeria

Abstract

The layering of rock strata and depth to the basement rocks of a Federal University Teaching Hospital premises in Northern Nigeria was investigated in this study with the aim of providing 2D geo-electrical resistivity images of the subsurface for geotechnical development using a modern and state-of-the-art field instrument, the ABEM Automatic LUND Imaging System (Terrameter SAS 4000 and ES 464). Three profiles were covered and the data processed to display the variations of electrical resistivity using the RES2DINV software. The results of the survey in correlation with borehole data in the area revealed three distinct layers: the overburden which is about 16 m - 26 m thick having a resistivity range of about 194 Ωm – 1759 Ωm. The weathered basement which is appreciably thick (about 5 m – 14 m),which is highly fractured and weathered, so constitutes a good aquifer having a resistivity range of about 0.687 Ωm – 678 Ωm and the fresh crystalline basement having a resistivity of about 1223 Ωm. The fresh crystalline rock is at variable depths of about 21 m - 40 m below the surface.

Keywords: Rock strata, Geotechnical, Electrical resistivity, Basement, Overburden