Delineation Of Anisotropy Properties Of Fracture In Part Of Federal University Oye-Ekiti Campus Southwestern Nigeria, Using Radial Vertical Electrical Sounding (Rves) Method

ABSTRACT

Electrical resistivity survey was used to investigate the anisotropic properties with the view of understanding the major direction of fractures as well as the behavioural patterns of the structures in part of Federal University Oye Ekiti, south western Nigeria. The area lies within the south-western Basement complex of Nigeria underlain by migmatite, granite gneiss. Five Radial Vertical Electrical Soundings (RYES) were carried out along four different azimuths (0°, 45°, 90°, and 135°) to determine the electrical anisotropy. The quantitative interpretation of RYES curves involved the use of partial curves matching and computer iteration using WINRESIST software. Polygons produced from eight radial sounding showed the dominant structural trends of fractures on the banded gneiss. The radial resistivity survey results show that there is significant anisotropy between 0-40 m depth generally striking NE-SW, NW-SE and N-S showing the major structural trend of basement fractures. Variation of apparent resistivity is strongest at the eastern and southern parts of the study area with coefficients of 1. l, and 2.0 this high coefficient of anisotropy implies higher- permeability anisotropy. The orientation of geologic structures from the study area showed an NE-SW, and NWSE directions of the structures depicted by the anisotropic polar plot. The fractures are known to be complex and in turn interconnected. Hence a fracture controlled flow. The main water - bearing unit in the area of study is the weathered basement and the fractured basement which are within the second and third geo-electric layers respectively. The weathered/fractured basement r(?sistivity values vary from 57 Ohm-m and 1282 Ohm-m with thickness values ranging from 0.lm to7.9m.