Browsing by Author "Abubakar, HO"
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Item Aeromagnetic and Resistivity Tomography Technique for Investigating Leakage Paths in Apodu Dam, Ilorin Sheet 201, Southwestern Nigeria(Alhikmah University, 2021) Olawumi, HB; Olatunji, S; Ajadi, J; Abubakar, HOThe aeromagnetic and electrical resistivity tomography technique was used to evaluate the foundation conditions and stability of the Apodu earth dam located around Malete, Ilorin Sheet 201, Southwestern Nigeria. The Aeromagnetic data set was interpreted to identify dykes, lineaments, and magnetic sources controlling subsurface geology. The extracted lineament structures were employed to examine features controlling the distribution of surface and subsurface hydraulic substances cum stability of dam slope. Magnetic lineaments' length and parallelism in some areas suggested installation under a tensional stress field along pre-existing zones of weakness.Magnetic susceptibilities are not uniform in the area and were categorized viz: high, moderate, and low. The magnetic intensity range at Apodu dam is -644.19 to 285.40 nT. The northeastern part of the study area where the Apodu dam is located shows little or no sign of faulting and appears to be more stable structurally. Characterization of the Apodu dam subsurface for seepage appraisal using electrical resistivity tomography technique revealed that the dam is well compacted at the surface but with observed low resistivity values indicative of possible occurrences of weakness zones that are water-bearing in some areas of the dam embarkment body at depths of around 8m and 25m. These observed low resistivity zones indicating a water-bearing weakness zone were connected in RTM1 and RTM2, and a possible water pathway was established. This water pathway is indicative of a possible seepage pathway and adequate measures are expected to be made to arrest the situation. In conclusion, Apodu dam is situated in a geologically stable environment as deduced from the aeromagnetic study but its earth embarkment is suspected to possess areas with possible seepage zones as obtained from the electrical resistivity techniques of investigations. There is therefore a need to quickly remedy the dam earth embankment to ensure the longevity of the dam and avert possible failure.Item ELECTRICAL PROBE OF THE SUBSURFACE GEOLOGY FOR GROUNDWATER EXPLORATION IN IREWOLEDE ESTATE, ILORIN KWARA STATE(School of Pure and Applied Sciences Modibbo Adama University of Technology, Yola, 2018) Olatunji, S; Abubakar, HOThe resistivity method involving an electrical resistivity survey was carried out using Vertical Electrical Sounding in Irewolede Estate of Ilorin west Local Government, Kwara State. This is to map depth to the thickness and the general resistivity distribution of the study area with high groundwater potential. The survey was carried out with Terrameter model DDC-8; a total of eleven VES points and three profiles respectively were covered. The survey lies within the crystalline basement complex of western central Nigeria and is bounded by latitude 080 27’ 40” N, 080 27’ 45“and longitude 40 33’ 11”, 40 33’ 14” E. The resistivity value was obtained between 2 Ωm to 3000mΩ for profiles 1-3. Four prominent geoelectric layers with varying resistivity and thickness were delineated on all the VES points. The first layer has a resistivity value ranging from 48 Ωm to 934 Ωm with their thickness ranging from 0.5m to 1.0m. This layer is the top soil which contributes to the development of groundwater because it is the passage for the flow of surface water to the fractured subsurface layers. The resistivity value of the second layer dominated by laterite ranges between 7.39Ωm to 2479Ωm while the thickness varies between 1.0m to 11.4m. The third layer resistivity values range between 23.4 Ωm to 255 Ωm with variations in their thickness that range between 3.7m to 29.7m. This and the next layer are believed to contain the aquiferous layer. The fourth layer is the fractured basement, which is believed to be a porch for the underground water. The depth of the aquifer in the area ranges between 3.7m to 29.7m. Overburden is the thickness (about 30m) around the southern part of the area.Item Geophysical Assessment for Characterising Leakages from Asa dam, Nigeria(Faculty of Pure and Applied Sciences, Ladoke Akintola University of Technology, 2021) Olawumi, HB; Olatunji, S; Ajadi, J; Abubakar, HOAeromagnetic and Electrical resistivity tomography techniques were used to evaluate the foundation conditions and stability of the Asa earth dam located in Ilorin. The Aeromagnetic data set was interpreted to identify dykes, lineaments, and magnetic sources that are controlling the subsurface geology. The extracted lineament structures were employed to examine features that are controlling the distribution of surface and subsurface hydraulic substances which affects the stability of the dam. The nature of the magnetic lineaments in some parts of the area suggests rock emplacement under a tensional stress field. Magnetic susceptibilities are not uniform in the area and were categorized viz: high, moderate, and low. The magnetic intensity range at Asa dam is 126.56 to -20.90 nT. The northwestern part of the Asa dam area shows little or no sign of faulting and appears to be more stable structurally than the other part of the study area. Characterization of Asa dam earth embankments for seepage appraisal using resistivity tomography technique revealed that the Asa dam is well compacted with no sign of any seepage. In conclusion, the Asa dam is situated in a geologically stable environment as deduced from the aeromagnetic study, while the earth embankments are well compacted with no sign of seepage as obtained from the electrical resistivity tomography technique of investigationsItem Hydrogeophysical Assessment of Groundwater in a Basement Complex of Southwestern Nigeria(Department of Geology School of Physical Sciences, Federal University of Technology, Minna, 2021) Ige, OO; Abubakar, HO; Olatunji, SHydro-geophysical investigation of a fractured basement involving the Very Low-Frequency Electromagnetic (VLF-EM) and the electrical resistivity methods has been carried out within Oye Ekiti town, South-western Nigeria. This study demonstrates the effectiveness of integrated geophysical investigation in groundwater potential assessment in a typical basement complex environment. This was done to access the groundwater potential of the area. Fourteen (14) VLF-EM and Horizontal Profiling (HP) traverses were established. Thirty-one (31) Vertical Electrical Soundings (VES) were conducted at the investigated site. The VLF-EM data were presented as profiles and 2-D images. Horizontal Profiling data were also presented as profiles while the VES data were presented as geologic sections. The VLF-EM profiles and 2-D images identified conductive zones which were confirmed by the subsurface geologic sections developed from the investigation results of the VES. The geologic sections delineated Frye's subsurface geologic layers. These include the topsoil, laterites, sandy clay, weathered basement, and fresh basement. The weathered basement constitutes the main aquifer unit within the study area. The weathered layer is generally thin and clayey. The relatively low weathered basement resistivity could indicate enhanced permeability due to significantly fractured density and the tendency for moderate groundwater potential and yield through the groundwater potential mapItem Hydrogeophysical Assessment of Groundwater in a Basement Complex of Southwestern Nigeria(Department of Geology School of Physical Sciences, Federal University of Technology, Minna, 2021) Ige, OO; Abubakar, HO; Olatunji, SHydro-geophysical investigation of a fractured basement involving the Very Low-Frequency Electromagnetic (VLF-EM) and the electrical resistivity methods has been carried out within Oye Ekiti town, South-western Nigeria. This study demonstrates the effectiveness of integrated geophysical investigation in groundwater potential assessment in a typical basement complex environment. This was done to access the groundwater potential of the area. Fourteen (14) VLF-EM and Horizontal Profiling (HP) traverses were established. Thirty-one (31) Vertical Electrical Soundings (VES) were conducted at the investigated site. The VLF-EM data were presented as profiles and 2-D images. Horizontal Profiling data were also presented as profiles while the VES data were presented as geologic sections. The VLF-EM profiles and 2-D images identified conductive zones which were confirmed by the subsurface geologic sections developed from the investigation results of the VES. The geologic sections delineated Frye's subsurface geologic layers. These include the topsoil, laterites, sandy clay, weathered basement, and fresh basement. The weathered basement constitutes the main aquifer unit within the study area. The weathered layer is generally thin and clayey. The relatively low weathered basement resistivity could indicate enhanced permeability due to significantly fractured density and the tendency for moderate groundwater potential and yield through the groundwater potential map.Item Integrated Geophysical Delineation of the Aquifers in a Part of the Basement Complex of Akure, South Western Nigeria(School of Engineering and Engineering Technology, Federal University of Technology Minna, 2016) Abubakar, HO; Bayode, S; Olatunji, S; Ajayi, CA; Yusuf, MAElectrical resistivity and Electromagnetic data were acquired using Schlumberger and VLF techniques to investigate zones of favorable groundwater conditions in the hard rock of Federal Housing Estate Akure, Ondo state, Nigeria. The static water level of the study area ranges from 0.3 m – 4.2 m. Four prominent lithological series delineated are topsoil, weathered layer, fractured basement, and fresh basement. The topsoil has resistivity ranges of 73-267 ohm-m and thickness ranges of 0.4-5.1 m. The weathered layer has resistivity ranges of 41-205 ohm-m and a thickness range of 1.1 -8.4 m while the fractured basement has a resistivity range of 85-2387 ohm-m and its thickness varies from 40 to 122.5 m. The low resistivity in the fractured basement which shows in all four traverses could indicate the presence of conductive matters such as water in there. Fresh basement has the highest resistivity of 20614 ohm-m, indicating the freshness of the hard rock in the area. A significant highest positive filtered real VLF value of 40% that indicates high conductivity occurs at traverses 2 and 3 while 1 shows as much as 30%. In conclusion, the interpretation of results of the stations along four established traverses revealed that the area of generally favorable groundwater conditions provided the fractured zones are fully penetrated within the basement in other to exploit a reasonable quantity of water from the area.Item Monitoring of Seepage in Agba Dam, Kwara State, Nigeria, Using Vertical Electrical Sounding Technique(School of Engineering and Engineering Technology, Federal University of Technology Minna, 2015) Olatunji, S; Ojulari, BA; Abubakar, HO; Yusuf, MAThe geophysical investigation has been undertaken at Agba Dam, Ilorin; located around the southern flanks of the Nigeria basement complex. It is bounded by longitudinal E 0040 35’ 0.72” – E 0040 35’ 40.6” and latitude N 080 28’ 23.3” – N 080 28’ 40.1”. This was aimed at investigating possible seepage along the dam’s flank. The vertical Electrical Sounding (VES) technique was used for the field study. Twenty VES stations of four profiles were established along the bank of the dam and data were acquired using the Schlumberger electrode configuration. The resistivity values in the surveyed area vary from 9.28 Ωm to 9409.37 Ωm. Three major geo-electric layers were delineated which are: topsoil, weathered layers, and fresh basement. The 2D pseudo-section along the profiles revealed the lowest resistivity of 30 Ωm at the depth of 3m. This observation could be a signature of seepages around those areas. Also, a minor conductive zone that appears close to the dam embankment could signify inceptions of buried erosion. This could be inimical to the future sustenance of the dam. The highest resistivity of 1000 Ωm was discovered at the depth of 10 m around VES 13 which is the area of the Dam embankment. This implies that the structure of the Dam embankment is not compromised and is still effective.