Geosciences-Scholarly Publications

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Browsing Geosciences-Scholarly Publications by Author "Adegbola, R.B"

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    Open Access
    Effect of flood analysis on the foundation investigation using integrated approach
    (Society of Exploration Geophysicists, 2015) Adeoti, L; Odunuga, S; Adegbola, R.B; Oladele, S
    The effect of flood analysis on the foundation investigation of the proposed Gas-Fired Power Plant in Badagry, Lagos, Nigeria was carried out using geophysical, geotechnical and geographical information system (GIS) methods. The subsurface information was obtained by using two electrode arrays for the resistivity data acquisition. Geotechnical data were obtained through two boreholes via percursion drilling within the study area. The integration of geophysical and geotechnical data reveals that the subsoil materials comprises fibrous peat, organic silty clay, clayey sand, sandy clay and sand. The analysis of the subsoil conditions via geotechnical data shows the feasibility of foundation around 25 m via piling while the safe grade elevation has been worked out to be 6.672 m for 100yrs return period via GIS approach. Thus, in order to avoid adverse effect of flood on the proposed structure, the safe grade elevation value has to be added to the foundation floor.
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    Open Access
    Geoelectrical Investigation of Groundwater Potential At Riol Farm, Owode, Abeokuta, Ogun State
    (Journal of the Nigerian Association of Mathematical Physics, 2016) Adeoti, Lukumon; Ijezie, N.T; Adegbola, R.B; Ojo, A.O; Afolabi, S.O; Adesanya, O.Y
    Geoelectrical investigation was carried out in order to solve the problem of drilling unproductive boreholes in RIOL Farm situated at Owode, Abeokuta in Ogun State. Fifteen (15) Schlumberger Vertical Electrical Sounding (VES) with current electrode spacing (AB) ranging from 2 m to 1000 m were acquired using PASI resistivity meter. The VES data were processed and interpreted using partial curve matching and computer iteration technique using WinRESIST software. The qualitative analysis reveals that the rising curves are dry sand devoid of groundwater while the descending parts of the VES curves are indicative of wet sands which could serve as potential aquifer. Four geoelectric sections generated from the interpreted VES results show four to six geo-electrical layers which correspond to topsoil with resistivity ranging between 45.0-993.9 ohm-m and thickness range between 0.5-1.0 m, lateritic clayey sand with resistivity ranging between 61.8-2328.0 ohm-m and thickness range between 1.2-5.5 m, sand/sandstone having resistivity range of between 1003.4-9575.9 ohm-m and thickness range between 4.2-114.8 m, sand with resistivity value ranging from 318.9-1581.2 ohm-m and thickness range between 5.1-78.9 m and consolidated sandstone / ironstone with resistivity value between 23245.5-4388.7 ohm-m. The quantitative analysis reveals that sands at the upper layer are dry within the depth of 2.2 – 69.8 m and appear to be unsaturated while sands at the depth not less than 80 m in VES 2, VES 9 and VES 15 are wet (saturated) and recommended for drilling. Thus, the wet sands denote aquifer units in the study area. Based on our recommendation, the location of VES 15 was drilled and yielded a productive borehole within a depth of 110m.
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    Open Access
    Geoelectrical investigation of the groundwater potential in Mowe, Ogun State, Nigeria
    (British Journal of Applied Science & Technology, 2012) Adeoti, L; Alile, O.M O. M; Uchegbulam, O; Adegbola, R.B
    Electrical resistivity survey was carried out to delineate subsurface layers and to determine the ground water potential in the study area. The study was carried out using the ABEM SAS 1000 terrameter which worked on 16 vertical electrical sounding (VES) points within the area. A maximum distance of 550m current electrode spread was adopted for this survey. The result showed the presence of four geoelectric layers with the resistivity of the first layer ranging from 25.54Ωm to 619.45Ωm and thickness of 0.14-9.21m representing topsoil. The second geoelectric layer has resistivity ranging from 20.94Ωm to 706.82Ωm and thickness of 2.58 to 35.36m representing laterite. The third geoelectric layer has resistivity ranging from 12.29Ωm to 598.93Ωm and thickness of 3.33 to 58.06m representing sandy clay. The fourth geoelectric layer has resistivity ranging from 12.1Ωm to 1980.52Ωm and thickness of 11.4 to 45m representing sand. The depth to the aquifers are 13.11m, 55.31m, 6.35m, 50.28m, 51.08m and 28.01m in VES 1, 2, 6, 9, 11 and 16 respectively.
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    Open Access
    Geophysical and geotechnical assessment of a failed canal.
    (Society of Exploration Geophysicists, 2015) Adeoti, L; Kehinde, I; Jalekun, A.A; Adegbola, R.B
    The integration of geophysical and geotechnical methods was used to assess a failed canal at Ijora Badia, Lagos Nigeria. The subsurface information was obtained by using two electrode arrays for the resistivity data acquisition. Geotechnical data were obtained through four boreholes via percursion drilling within the study area. The integrative approach reveals that the subsoil materials consist of peat, organic silty clay, clayey sand, silty sand, and sand. The study shows that low resistivity values exhibited by soft clay / peat and are possible cause of the collapse. The analysis of the subsoil conditions based on the proposed load of 60 kN/m2 imposed by canal structure on the peaty soil reveals settlement values of 365-843 mm which are too excessive for shallow foundation types. Also lateral and vertical thicknesses of the peat preclude the use of piling and vibroflotation. Thus, ground improvement using chemical grounding is proposed.
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    Open Access
    Geophysical and hydrogeological evaluation of rising groundwater level in the coastal areas of Lagos, Nigeria
    (Bulletin of engineering geology and the environment, 2009) Oyedele, K.F; Ayolabi, E.A; Adeoti, L; Adegbola, R.B
    The paper reports the change in groundwater level observed in 30 wells in ten locations in southern Nigeria. Borehole data confirmed the electrical resistivity soundings which indicated the presence of topsoil, medium sand, sand, clayey sand and coarse sand. In some cases, there was little apparent change in the rate of groundwater rise, but from the data obtained it can be concluded that in the years 2000–2004 the average yearly rise was 0.3 m while between 2004 and 2007 it rose on average by 0.5 m. This rise in groundwater level has serious implications for both existing structures and the nature of the foundations for future building. The electrical resistivity survey was found to be a helpful tool in detailing the morphology of the groundwater surface and is recommended for ongoing monitoring.
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    Open Access
    Resolution Analysis of Different Electrode Array on Synthetic Earth Models of Geological Relevance
    (Journal of the Nigerian Association of Mathematical Physics, 2016) Adeoti, Lukumon; Ishola, K.S; Imenvbore, I; Ojo, A.O; Adegbola, R.B; Afolabi, S.O
    This study compares the resolution capabilities of different electrode arrays in imaging 2-D earth models by employing the Finite difference modeling scheme. The software called RES2DMOD was used to generate 2-D synthetic models having a resistive block in a conductive environment with different resistivity values, three conductive blocks in a highly resistive environment and a high resistive dyke in conductive environment. The synthetic data were contaminated with 6% Gaussian noise and inverted using the RES2DINV inversion software. The reconstructed resistivity values reproduced from a block of 100 Ωm at a depth of 2.8 m by Dipoledipole, Pole-dipole, Wenner-schlumberger and Wenner arrays are 94.1 Ωm, 90.9 Ωm, 77.8 Ωm and 46.7 Ωm respectively. For a dyke model with a resistivity of 500 Ωm, the inverted resistivity values are 355 Ωm, 312 Ωm, 281 Ωm, and 291 Ωm respectively. This shows that the dipole-dipole array recover a more accurate resistivity value of the block. However, the pole dipole array gives a higher resolution image at deeper depth when two blocks of different resistivity values in a conductive environment along a spread of 35 m. For the same structure, the dipole-dipole, pole-dipole, schlumberger and wenner arrays gave a depth estimates with variation of 9.12m, 13.6m, 7.88m and 6.75m from the true value. The study shows that dipole dipole gives best resolution for vertical structures such as dykes while the Pole-dipole seems more efficient for this same purpose at deeper depth. Also, Wenner array gives low resolution while investigating dipping structures. Schlumberger array was able to image sharp boundaries between two lithological units but gives poor results for dipping structures.
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    Open Access
    Soil Resistivity Measurement for Corrosivity Assessment using Barnes Method.
    (Nigerian Research Journal of Engineering and Environmental Sciences., 2018) Adeoti, Lukumon; Adegbola, R.B; Ademilola, J.A; Oyeniran, T.A
    Corrosion attacks are frequently responsible for most material’s failures and its effect on underground metallic materials is a very widespread problem. In order to avoid unpleasant corrosion of pipes and steel structures, the electrical resistivity technique using Barnes method was utilised at PZ Cussons Ikorodu, Lagos State, Nigeria. Electrical resistivity survey (Wenner array method) was carried out with a resistivity meter in which four electrodes were deployed at each of the fifteen electrical resistivity test (ERT) locations. The pattern of distribution of resistivity based on geophysical analysis reflects four groups. Group 1 has resistivity values less than 50 ohm-m. Group 2 accommodates resistivity values between 50 and 100 ohm-m. Group 3 has resistivity values between 100 and 200 ohm-m. Group 4 houses resistivity values above 200 ohm-m. The general trend of the geophysical analysis in Group 4 revealed that resistivity values are high and therefore do not pose a corrosive risk to proposed metal pipes and steel structures at the aforementioned depths. In contrast, groups 1-3 which are predominant, have resistivity values that are less than 200 ohm-m which correspond to low to very high corrosive probability. The analysis revealed that mitigation measure should be considered via good cathodic protection for these groups where resistivity values are considered low at various depths within the study area. Therefore, proposed metal pipes and steel structures should be buried between depth intervals 1.50– 4.50 m in the area under investigation.