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Geophysical and geotechnical techniques were used to investigate the sub-surface information of a proposed site for a hostel construction at Federal University of Agriculture, Abeokuta. Ten vertical electrical sounding (VES) stations were adopted. Typical sounding curves obtained include the HA, KH, AKH and KQH types, of which the AKH-type consists of 40% of the survey points, and a maximum of five geo-electric sub-surface layers were delineated. Laboratory analyses were performed to investigate particle size distribution, Atterberg limit, compaction limit, California bearing ratio (CBR) and specific gravity. The CBR revealed that all soil samples, except L4, are mechanically stable and have high load-bearing capacity. The Atterberg limit test and the geo-electric section showed that the second layer of VES 4 is composed of sandy clay with high plastic index and low liquid limit, which may pose a threat to the foundation of any engineering structure. VES locations 5, 6 and 8 were identified as high groundwater potential zones suitable for optimum groundwater abstraction. The study area is suitable for both shallow and deep foundations, however VES 4 and VES 5 require reinforcement.

Vertical electrical resistivity soundings were conducted in order to delineate groundwater potential aquifers in Akobo area, Ibadan, South western, Nigeria. Twenty-one vertical electrical soundings were conducted using the Schlumberger configuration, covering the area. The data were interpreted with the help of Abaque (master) curve. The geoelectrical sections for the study area were: the topsoil, the clayey sand, sandy clayey, shale/clay basement and the fresh basement. The dominant rocks comprise suites of quartz schist and pegmatite. Interpretations of vertical electrical sounding (VES) were used to generate longitudinal conductance map. Isoresistivity contour map was prepared and interpreted in terms of resistivity and thickness of sub-surface layer at 56 m spacing using computer software (SURFER), and resistivity results were correlated with the existing lithology. Similarly, aquifer unit(s) thickness map was also prepared, in which good, moderate and poor zones are classified. The study reveals that the weathered and fractured horizons that occur in the easternmost part of the area constitute the productive water-bearing zones referred to as good groundwater potential aquifers with a thickness value greater than 20 m.

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