Springer (Applied Water Science)

 Journal

 Borehole Depth Determination To Freshwater And Well Design Using Geophysical Logs In Coastal Regions Of Lagos, Southwestern Nigeria

 A. A. Akinlalu · D. O. Afolabi

 2018

The determination of depth to freshwater aquifers and lack of geophysical borehole log data to help borehole developers in the design of borehole have long been identified as a problem in coastal areas. This necessitates a study of the coastal environment of Lagos, southwestern Nigeria, to determine the depth to freshwater and give recommendation on the borehole design during installation stage that can be projected to areas immediate to where geophysical logs are available. For this study, twenty geophysical log data were utilized which are spread across Ikoyi, Victoria Island and Lekki of Lagos metropolis. The study shows that the saline water extent in Ikoyi, Victoria Island and Lekki occurs to an average depth of 146, 154 and 162 m, respectively. Relative variation in quality of water across the regions is because of the differences in the thickness of clay units serving as protective units separating the polluted zones from the unpolluted zones. It is recommended that water wells in Ikoyi, Victoria Island and Lekki be drilled to an approximate depth of 240 m and the last 18 m be screened. This research work was able to develop a design model for the boreholes located in the Island. The model includes gravel packing thickness of about 50 m from the bottom of the hole and cement grouting to the surface of the borehole to avoid the contamination of the borehole. 

 NRIAG Journal Of Astronomy And Geophysics

 Journal

 Evaluation Of Road Failure Vulnerability Section Through Integrated Geophysical And Geotechnical Studies

 K.A.N. Adiat, A.A. Akinlalu , A.A. Adegoroye

 2017

In order to investigate the competence of the proposed road for pavement stability, geotechnical and geo- physical investigations involving Land Magnetic, Very Low Frequency Electromagnetic (VLF-EM) and Electrical Resistivity methods were carried out along Akure-Ipinsa road Southwestern Nigeria. The mag- netic profile was qualitatively and quantitatively interpreted to produce geomagnetic section that pro- vides information on the basement topography and structural disposition beneath the proposed road. Similarly, the VLF-EM profile was equally interpreted to provide information on the possible occurrence of linear features beneath the study area. These linear features pose a potential risk to the proposed road as they are capable of undermining the stability of the pavement structure. The geoelectric parameters obtained from the quantitative interpretation of the VES data were used to generate geoelectric section. The geoelectric section generated shows that the study area was underlain by four geoelectric layers namely the topsoil, the weathered layer, the partly weathered/fractured basement and the fresh base- ment. The major part of the topsoil, which constitutes the subgrade, is characterized by relatively low resistivity values ( 

 NRIAG Journal Of Astronomy And Geophysics

 Journal

 Groundwater Vulnerability Assessment Using Hydrogeologic And Geoelectric Layer Susceptibility Indexing At Igbara Oke, Southwestern Nigeria

 T.E. Oni, G.O. Omosuyi, A.A. Akinlalu

 2017

Groundwater vulnerability assessment was carried out at Igbara Oke Southwestern Nigeria, with a view to classify the area into vulnerability zones, by applying the electrical resistivity method, using Schlumberger electrode arrays with maximum electrode separation (AB/2) of 65 m in (41) different loca- tions for data acquisition. Geoelectric parameters (layer resistivity and thickness) were determined from the interpreted data. The study area comprises four geoelectric layers (topsoil, lateritic layer, weathered/ fractured layer and fresh basement). The geoelectric parameters of the overlying layers across the area were used to assess the vulnerability of the underlying aquifers to near-surface contaminants with the aid of vulnerability maps generated. Three models were compared by maps using geo-electrically derived models; longitudinal conductance, GOD (groundwater occurrence, overlying lithology and depth to the aquifer) and GLSI (geoelectric layer susceptibility indexing). The total longitudinal conductance map shows the north central part of the study area as a weakly protected (0.1–0.19) area, while the northern and southern parts have poor protective capacity ( 

 Kuwait J. Sci

 Journal

 Ntegrated Geophysical Investigation For Pavement Failure Along A Dual Carriage Way, Southwestern Nigeria: A Case Study

 Akinola M. Adesola, Akinlalu A. Ayokunle, Adelusi O. Adebowale

 2017

An integrated geophysical investigation was carried out on some portions of Ogbomoso-Ilorin dual carriage way located within the basement complex area of Southwestern Nigeria, with a view to delineating the cause(s) of road pavement failure observed along the road. Three failed portions and one control stable segment of the road pavement were investigated within the southwestern flank of the road. This study integrated very-low-frequency (VLF) electromagnetic (EM), ground magnetic and electrical resistivity (ER) geophysical prospecting methods for detailed study of the terrain. Two (2) VLF-EM and ground magnetic traverses were established per studied location. A total of fifty three (53) vertical electrical sounding (VES) using Sch lumberger array was occupied. 2-D resistivity imaging using dipole-dipole electrode array were employed along the established traverses. Qualitative interpretation of the VLF-EM and ground magnetic profiles suggest typical fracture zones. The results obtained from the VES and 2-D resistive image of the subsurface showed major geologic features, which are typical of fractures, faults, joints, cavities and voids. The near surface subsoil on which the road pavement is founded within the failed and stable segments is predominantly characterized by low resistive materials ( 

 Elsevier (Journal Of African Sciences)

 Journal

 Aeromagnetic Mapping Of Basement Structures And Mineralisation Characterisation Of Ilesa Schist Belt, Southwestern Nigeria

 A.A. Akinlalu , A.O. Adelusi , G.M. Olayanju , K.A.N. Adiat ,G.O. Omosuyi , A.Y.B. Anifowose , B.E. Akeredolu

 2017

This paper analysed aeromagnetic data over the southern Ilesa schist belt of Nigeria with a view to assessing the sub surface structural settings that might favour mineralisation in the study area. Enhancement of the total magnetic intensity map was carried out to improve the anomaly characteristic of source bodies through upward continuation and reduction to the equator (RTE) of the magnetic fi eld intensity. Estimation of depth to the deep, intermediate and near surface structures was based on the Spectral analysis and Euler deconvolution of the aeromagnetic data. Extracted magnetic anomalies from the RTE map range in amplitude from 115 to 134 nT, with the high magnetic intensities occurring over amphibolite, schist, porphyritic granite, gneiss and undifferentiated Migmatite, while low magnetic in- tensities were observed over quartzite and the undifferentiated schist. The Euler deconvolution solutions revealed that the area is mainly affected by sill/dyke and horizontal cylinder/pipe geologic model with estimated depth to the magnetic source ranging from 73 m e 345 m. The depth estimated from the spectral analysis was in the range of 100 m e 300 m for the intermediate and shallow sources; this compares reasonably well with the results from the Euler deconvolution. The orientations of lineaments extracted from the total horizontal derivative, source edge detection and Euler deconvolution suggest predominantly NE-SW trending structures, characteristic of primary geologic events in the area, while few E-W trending lineaments are imprints of secondary structural alteration in magnetic fabrics in this direction. Thus, the delineated structures are believed to be the hosts to the mineralised targets as observed from small scale mining activities in the area 

 Journal Of Geology And Mining Research

 Journal

 Interpretation Of Aeromagnetic Anomalies And Electr Ical Resistivity Mapping Around Iwaraja Area Southwestern Nigeria

 Adelusi A. O , Kayode J. S. 2 And Akinlalu A. A

 2016

Aeromagnetic, ground magnetic and vertical electric al sounding (VES) methods were used to delineate the basement structures around Iwaraja area, southw estern Nigeria. In doing this, an aeromagnetic sheet 264 of the Geological Survey of Nigeria (GSN) and digitized aeromagnetic map from Nigeria Geological Survey Agency (NGSA, 2008) were interpre ted. Also sixteen ground magnetic profiling were carried out, mostly in the E-W direction. A total o f sixty seven vertical electrical soundings using Schlumberger electrode configuration was occupied. Qualitative interpretation of the aeromagnetic and ground magnetic profiles suggest varying magnetic i ntensities from different sources producing the anomaly. Quantitative interpretation aided by the m anual half slope and automated Euler deconvolution techniques yielded information on depth to fracture , ranging between 6 and 38 m. Vertical electrical sounding results helped in the delineation of four subsurface geologic layers, also basement depressions that coincides with fracture zones were mapped in the area. The top soil layer resistivity ranges from 50 to 2359 ? m. The weathered layer (clay, clayey sand, sand and sandy clay) resistivity ranges from 35 to 4935 ? m while the fractured basement ranges from 152 to 9 81 ? m and the fresh basement resistivity ranges from 1132 to 22821 ? m. A major basement ridge (Rs 1 ) trending approximately in the NE-SW direction was also delin eated 

 Global Journal Of Science Frontier Research

 Journal

 Application Of Electrical Resistivity Method In Designing A Structural Model For A Proposed Filling Station Site, Akure, Southwestern Nigeria

 Akinlalu , A. A. ,Adegbuyiro A, Obore, A. A

 2016

The subsurface characterization of sub - soil of a propose d filling station was carried out along Ilesha road, Akure, Ondo State with the aim of designing a structural model for the filling station. To achieve this, Electrical Resistivity method using Dipole -Dipole and Schlumberger Vertical Electrical Sounding (VES) was employed. Dipole -Dipole run through five (5) traverses in the north -south direction. A total of twenty -five (25) VES points were established with five (5) at each traverses. Dipole -Dipole data were used to generate 2 -D resistivity structure image with resistivity ranging from 19 ohm –m – 487 ohm – m at the topsoil and 19.0 ohm - m – 80 ohm - m at the weathered layer. The VES data were interpreted through partial curve matching and computer iteration. The interpreted data were used to generate geo - electric sections showing that the geo - electric sequence comprise of topsoil, weathered layer, partly weathered/fracture basement and fresh basement. The resistivity ranging from 22 ohm - m – 83 ohm - m at the topsoil, 12 ohm - m – 507 ohm - m at the weathered layer, 185 ohm - m - 864 ohm - m at the partly weathered/ fracture layer and 1987 ohm - m – 33693 ohm - m for the fresh basement. Keywords: subsurface characterization, structural model, filling station . 

 Journal Of Environment And Earth Science

 Journal

 Geophysical And Hydrochemical Investigation Of A Mu Nicipal Dumpsite In Ibadan, Southwest Nigeria

 Tosin, A. Olla, Ayokunle, A. Akinlalu, Gbenga, M Olayanju , Adebowale, O. Adelusi, Kola, A. Adiat,

 2015

Geophysical and hydrochemical investigations have b een undertaken within a reclaimed site of municipal dumpsite in Ibadan, southwestern Nigeria with a vie w of assessing the impact of effluent from the anci ent dumpsite on the soil and groundwater sytem. The stu dy area is underlain by precambrian Basement Comple x rocks mainly granite gneiss. The geophysical invest igation involved electrical resistivity methods usi ng dipole- dipole profiling and Schlumberger Vertical Electric al Sounding (VES), while the hydrochemical investig ation involved physical, chemical and microbial analyses of water samples within the reclaimed land and acti ve dumpsite. A total of 175 sampling points were occup ied using dipole-dipole profiling, while 29 Schlumb erger electrical soundings were carried out. In addition, water samples from available nine wells in the are a whose static water levels range between 1.2 m and 7.4 m w ere analysed. The results from electrical surveys s how that the study area is underlain by a maximum of four su bsurface layers namely the topsoil, the weathered l ayer, the partly weathered/fractured basement and the fresh b asement whose resistivities values range from 41-49 5 ohm- m, 13-643 ohm-m, 86-720 ohm-m and 2800 ohm-m and ab ove. Their thickness of the overburden units varies from 0.7- 49.5 m. The partly weathered/fractured ba sement constitute the main aquifer. The resistivity distribution of the topsoil and weathered layer ind icates that parts of these layers have been infiltr ated by plumes from the reclaimed land and active dumpsite, especi ally in areas characterised by low resistivity ( 

 International Journal Of Physical

 Journal

 Integrated Geophysical Investiga Tion For Post - Construction Studies Of Buildings Around School Of Science Area, Federal University Of Technology, Akure, Southwestern, Nigeria

 A. O. Adelusi, A. A. Akinlalu And A. I. Nwachukwu

 2013

An integrated geophysical investigation involving ground magnetic, very low frequency (VLF - EM), and electrical resistivity methods using dipole – dipole array and schlumberger vertical el ectrical sounding (VES) techniques were conducted around School of Science Area Obanla, Federal University of Technology, Akure, for post construction studies in assessing building foundation integrity. Two traverses were established in approximately E - W d irection of length 170 to 200 m and station interval of 10 m, along which VLF - EM, ground magnetic and dipole – dipole measurements were carried out. Sixteen VES stations were occupied within the study area. The VLF - EM data were interpreted using the Karous Hjelt (KH) package and inverted into its 2D Pseudosection. The VES data were quantitatively interpreted using the partial curve matching technique and 1 - D forward modelling with WinResist 1.0 version software. The dipole - dipole data were inverted into 2 - D resistivity images using the DIPPRO™ 4.0 inversion software. The VLF - EM result mapped three near surface conductive zones suspected to be fractures/faults which are inimical to foundation integrity. The magnetic results delineated series of bedrock ridges and depression. The VES result delineated four major Geo - electric layers within the study area. The topsoil, weathered layer, fractured bedrock and fresh bedrock. The top soil (resistivity varies from 47 to 490 ?m and thickness ranges from 0.7 to 3.9 m); w eathered layer (resistivity varies from 13 to 207 ?m and thickness ranges from 1.9 to 22.1 m), fractured bedrock (resistivity varies from 489.3 to 878.8 ?m and thickness ranges from 2.4 to 19.6 m) and bedrock with resistivity 1094 to 96583 ?m and depth to bedrock 2.6 to 24.8 m). The dipole - dipole results also mapped linear features (fracture) at distance 60 to 100 m and 100 to 120 m respectively along the two traverses. Then from the geophysical investigation, three major causes of potential failure in the area were identified, these are; failure due to lateral inhomogeneity of the subsurface layers, failure precipitated by differential settlement and failure initiated by geologic features such as fractures and faults 

 International Journal Of Water Resources And Environmental Engineering

 Journal

 Geophysical And Hydrochemistry Methods For Mapping Groundwater Contamination Around Aule Area, Akure, Southwestern Nigeria

 A.O. Adelusi, A .A. Akinlalu And S.S. Adebayo

 2013

An integrated geophysical investigation involving 2 D-Wenner profiling, very low frequency electromagnetic, vertical electrical sounding (VES) and water quality analysis was conducted around Aule area within Akure the capital city of Ondo sta te southwestern Nigeria where there have been reported cases of groundwater contamination. Also h ydrochemical analysis was carried out on five water samples in the area; two from boreholes and o thers from hand dug wells. Results of the investigation showed that the groundwater had been contaminated by hydrocarbon arising from a filling station in the area. The hydrocarbon contam inant plumes are characterized by relatively high resistivity values (> 200 -m) and were delineated to a depth of about 10 m. H ydrochemical results showed that three of the sampled water have higher total dissolved solids (TDS) (>240 ppm) compared to the remaining water samples. The major ions iden tified includes (Na + , K + ,Cl - ,Mg 2+, ,Ca 2+ and NO 3 - ). The total dissolved solid (TDS) and electrical conducti vity shows values not in agreement with WHO standards. Twelve (12) Vertical Electrical Sounding (VES) stations were occupied along three traverse lines trending NW-SE and N–S direction. The vertica l electrical sounding results indicate maximum of four subsurface layers-Top soil, hydrocarbon contam inated clay, weathered layer and the fresh basement. The VLF-EM results assist in the delineat ion of non conductive zones which in most cases coincides with the hydrocarbon contaminated plumes delineated by the 2D-pseudo section obtained from modeling the results obtained from Wenner prof iling. The contaminant plume has migrated to a significant depth thus posing an inherent danger to the inhabitant of the area.