The Use of Vertical Electrical Sounding (VES) for Subsurface Geophysical Investigation around Bomo Area, Kaduna State, Nigeria (original) (raw)
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2020
The interpretation of 10 schlumberger vertical sounding (VES) data was carried out at Karji area of Kaduna state, Nigeria. It was an attempt to investigate the variation in the resistivity values of earth materials as it varies with depth within the area. Ohmega Resistivity Terrameter was the principal instrument used. No booster was used as the expected depth is within the range of penetration of the instrument. In this instrument consecutive reading are taken automatically and the result averaged continuously and display. The schlumberger electrode configuration was used in the data acquisition. The field procedure consist of expanding AB (distance between current electrodes) while MN (distance between potential electrodes) is fixed. This process yields a rapidly decreasing potential difference across MN, which eventually exceeded the measuring capacity of the instrument; therefore a larger vale for MN was taken to continue with the survey. The VES curves were interpreted using IP...
The electrical resistivity investigation of Zuba and Tungamaje area, of Gwagwalada Area Council, Abuja, was carried out with a view to providing geology and geophysical information on the different sub-surface layers, depth, thickness, and distribution of the fractured basement as potential sources of groundwater. The basement rocks consist of a migmatite-gneisses, granite gneiss, and granite. The granite occurs in several locations of the study area. Twelve vertical electrical sounding stations were established utilizing the Schlumberger electrode configuration. The electrical resistivity data obtained where interpreted using IPI2win software. The results obtained from the analysis of the geophysical data showed that the study area is underlined by three geo-electrical layers. These layers are the topsoil, weathered layers, and fractured basement. The top soil layer of thickness and resistivity values ranging from 1.31-2.16m and 236-990 ohms meters, weathered layer ranging from 1.22-5.19m and 33.8-213 ohms meters and the fractured basement ranging from infinity in thickness and 397-966 ohms meters. Also, the study area lacks sufficient fractures and the thickness of the overburden was also thin for groundwater exploration activities.
2020
Geophysical investigation for engineering and environmental studies has been undertaken at the permanent site of Federal University Dutsin-ma, Katsina state. The study was aimed at assisting in the planning and development of infrastructure at the University, and also to investigate the groundwater potential of the permanent site at Turare which is less than 20km south of the current site the University occupies. Twenty-four Vertical Electrical Soundings (VES) were conducted along predetermined profiles at the permanent site in Dutsin-ma. Terrameter SAS 300 system was used for data acquisition at stations interval of 100m using Schlumberger array. Maximum current electrode separation (AB) of 200m was used. Interpretation was performed using computer software (Ipi2win and surfar7). The interpreted result was used to produce geoelectric and geologic sections. The result of the study indicated that the area is underlain by three to four subsurface layers. The resistivity of the first l...
Geological and Electrical Resistivity Sounding of Olokonla Area in North-Central Nigeria
Geological mapping and Electrical resistivity sounding were carried out in Olokonla area in Moro Local Government of Kwara State in order to determine the apparent resistivities of the subsurface lithologies and correlate them with the exposed rocks observed during the geological mapping. The studies also delineate the pattern of fractures in the area which form prefential pathways for ground water. Three vertical electrical soundings (VES) were performed radially adopting the Schlumberger electrode configuration, with half-current electrode separation (AB/2) varying from 1m to 100m. Anisotropy polygon was also constructed based on the radial electrical sounding. The geoelectric parameters revealed five subsurface layers which were interpreted as topsoil, lateritic soil, dry sand soil, weathered granite and granite respectively. The geological mapping showed that the area is underlain by crystalline rocks comprising biotite granite, granite-gneiss and migmatite. The anisotropy polygon showed that a major fracture direction along 60 0 (northeast to southwest) and the coefficient of anisotropy is 0.79. Based on the apparent resistivities and the structural disposition, a potential aquifer was inferred at a depth of 45m. The fracture pattern in the area was constrained to northeast to southwest direction. The data obtained would be useful in borehole drilling for water within the study area.
2010
Groundwater occurrence and distribution in Basement Complex is localized and confined to weathered /fractured zones. Hence exploration for groundwater in such terrains posses a great challenge to groundwater development agencies as in most cases the risk of failure of such projects is very high. This study was carried out with the aim of demonstrating the application of vertical electrical sounding method of investigation in the exploration for groundwater in Rimin Gado town and environs. A total of 16 VES points were probed located in 4 settlements spread at a distance of 200-300m apart. ABEM SAS 300C terameter was used to generate field data applying the Schlumberger Array with an AB/2 of 1.5-100m. The field data were simulated using Zhody and OFFIX software. The results show that there are 2-4 Geo-electric layers: topsoil (sandy/lateritic), highly weathered Basement (clay and sandy clay), slightly weathered/ fractured Basement (Clay,sand/clayey sand) and Fresh bed rock. Three bas...
Journal of Geography and Mining Research, 2017
Fifteen vertical electrical sounding (VES) stations were sounded using Schlumberger electrode configuration. The result revealed a total of 3 to 4 geoelectric layers. The first layer with resistivity values range from 2.8 to 149.2 Ωm and has thickness and depth of 0.1 to 6.5 m. The second layer has resistivity which ranges from 245.9 to 7761.2 Ωm, thickness of 1.1 to 10.7 m and depth of 1.2 to 17.2 m. This layer was observed to be more resistive than the overlain layer. The third layer was delineated with the resistivity range of 49.4 to 2161.4 Ωm, thickness of 4.5 m-∞ and depth of 5.7 m-∞. The fourth layer has resistivity values which range from 203.3 Ωm-∞ within the maximum current electrode separation. The observed curve types are K, Q, KH and QK with K being the dominant curve type. The contour maps generated display the variation of the electrical properties of the subsurface layers. The lithology layer with clay is not suitable for building foundation due to their expansive nature while the laterite which is mechanically stable is suitable for building foundation. The lateritic layer to a depth of 1.2 to 3.0 m is considered suitable for massive engineering structures with strong base for solid foundation.
Journal of Physics: Conference Series, 2019
Electrical resistivity method has been performed using Vertical Electrical Sounding (VES) technique at a Bishop Smith Memorial College, Ilorin, Kwara State to examine the geophysical parameters that can be used to evaluate the subsurface competency. Eight VES stations were sounded, using Schlumberger configuration for data acquisition with current electrode spacing varying from 1.0 to 140.0 m. The VES data obtained were interpreted using ipi2win+ip Software. The field data acquired was presented as geoelectric sounding curves and geoelectric section. The interpretation of the field results revealed heterogeneous subsurface geologic sequence probed to 34.6 m and beyond. It also showed presence of near surface linear geologic structures of varying lengths, depths and attitude which suggest the competent zones for foundation laying. The major subsurface layers are the top soil which consists of interlocking and concretional lateritic stones and clayey sand, weathered basement, fracture...
Journal of Environment and Earth Science, 2021
The utilization of geophysical methods can increase the effectiveness of civil engineering works since it can provide the information which the conventional civil engineering method was hard to determine due to the concern of money, time and quality. One of such geophysical methods is the Electrical resistivity using the Schlumberger array which was employed in this study. The study identified three lithological units of top lateritic soil, weathered / fractured basement and the fresh basement. The thickness of the top lateritic soil ranges from 0-4m, the weathered/ fractured basement has an average thickness in the range of 3.0-25 m while the fresh basement thickness ranges from 25 m to infinity. The resistivity values of the sub-surface layers range from 11.40 Ωm to 5896.7 Ωm with most of the lithological units rated competent to highly competent. This study serves as basis for further engineering investigation for the design and construction of proposed buildings and has shown the relevancy of the application of geophysics to civil engineering works.
Abstract The objective of this geophysical survey is to evaluate the hydrological characteristics of the study area. This includes the availability of groundwater, depth of aquifer, determining whether the underlying geology is competent basement/weathered basement or fractured bedrock and the delineation of the subsurface into various geo-electric layers. The availability of groundwater in an area is controlled by varying geological factors such as hydrogeological units, stratigraphical faults/folds, and geological sequences The methodology used is the direct current method using the schlumberger configuration. In this electrical resistivity method, artificially-generated electric currents are introduced into the ground and the resulting potential differences are measured at the surface. Deviations from the expected pattern of potential differences from homogeneous ground provide information on the lithological formations and electrical properties of subsurface anomalies. A total of 10 vertical electric sounding was carried out on the study area, which covers the entire community and the data plotted and computer software designed by Vander Velpen BPA was used to iterate the result. This removes the noise and field errors incorporated in the data. The result of the VES curve reveals that there are three major geoelectric layers The fist layer has an intermediate resistivity implying a sandy soil. Very low resistivity corresponds to clayey/clayey sand (VES 4, VES 5, and VES 6) while exceedingly high resistivity (VES 10) implies a lateritic cover. The second layer is the weathered layer sub-divided into minor geoelectric layers such as clays, gravels and weathered rocks. The weathered layers have low resistivity values, possibly due to the presence of conduction fluids such as water. The third layer is the basement or bedrock which may be fractured basement or fresh bedrock. Ajaokuta has more of fresh unfractured bedrocks except in some cases (VES 2 and VES 4) The resistivity of topsoil varies from 12.6Ω to 3247.9Ω with a mean of 657.1Ω ± 947.7. The thickness of topsoil is within the range of 0.4m to 14.9m with a mean of 2.2m ± 4.2. The resistivity of weathered layer ranges from 27.9Ω to 175.5Ω with a mean of 59.2Ω ± 43.5. The thickness of the weathered layer is from minimum of 5.8m to maximum of 37.0 m having a mean of 12.4m ± 9.5. The depth to basement varies from 6.2m to 37.5m with a mean of 13.38 ± 9.07. The resistivity of the basement in the area varies from 183.3Ωm to 4294.2Ωm with a mean 0f 905Ωm ± 1170.The thickness of the topsoil is very low except for (VES 4) The average depth to basement is 13.38m±9.07. Keywords: Boreholes, Ajaokuta, schlumberger configuration, resistivity, VES
International Journal of Geosciences, 2022
This report evaluates the use of electrical method and borehole data to investigate the subsurface to delineate the groundwater potential in Enugu metropolis and the environs, southeastern Nigeria other than rely only on resistivity method which could lead to interpretation error. Integrating these 2 data sets is key in this study. The study area is located in the Anambra Basin and is underlain by Nkporo/Enugu Shale which is overlain by the Mamu Formation. It is bounded by Latitudes 6˚2 0'00"N to 6˚30'00"N and Longitudes 7˚25'00"E to 7˚35'00"E and covers surface area of about 342 m 2. Thirty-one vertical electrical soundings (VES) were carried out across the area using the Schlumberger electrode array with current electrode separation from 2 to 500 m to identify the depths and resistivity values of the identified geo-electric layers. Through data analysis using WinResist software, the apparent resistivity, thicknesses and depths and the thicknesses of the aquifers were generated. The resistivity and depths were modelled to generate resistivity map and depth map. The resistivity of the aquiferous zone within the study area varied from 20.55-427.8 ohm-m at depths of between 10.7-40.05 m. Depth to the water table appears to be shallow at the south western part of the map. The interpreted geo-electric layers show a sequence of lateritic top soil, shale, sand and shale. The frequency distribution of the VES curves generated shows the presence of 3 to 5 layers with HK type as the highest. Also, a 2D model was generated using the correlation of VES to VES data and borehole data to VES data to show the underlying stratigraphy beneath the study area as well as the direction of ground water flow. Result of the VES curve analysis reveals that the sub-surface is underlain by three lithological layers namely: lateritic top soil, shale, sand and shales with NW direction of groundwater flow from the 2D model. Groundwater prospective zones can be seen along NW, SW and