scholarly journals Geophysical and Geotechnical Studies of a Proposed Structure at Akure, Southwestern Nigeria

2018 ◽  
pp. 1-12
Author(s):  
Ilugbo Stephen Olubusola ◽  
Adebo A. Babatunde ◽  
Ajayi Oluwasayo Adegbola ◽  
Adewumi Olufemi Olaoluwa ◽  
Edunjobi Hazeez Owolabi
Keyword(s):  
Clay Content ◽  
Geotechnical Investigation ◽  
Cone Penetration ◽  
Geophysical Investigation ◽  
Engineering Structures ◽  
Southwestern Nigeria ◽  
Weathered Layer ◽  
Electrical Sounding ◽  
Geoelectric Resistivity ◽  
Geotechnical Studies

Geophysical and geotechnical studies were carried out at a proposed location for the construction of a multi-storey structure in Akure, Southwestern, Nigeria. The aim was to ascertain the suitability of this location for both Founding and Engineering structures. The geophysical investigation involved the Vertical Electrical Sounding (VES) technique using the Schlumberger configuration, Dipole-Dipole Horizontal Profiling and a geotechnical investigation. A total of twenty-one (21) VES and five (5) Cone Penetration Test (CPT) locations were occupied within the study site. Dipole-Dipole Horizontal Profiling was occupied along traverses 1 and 2 within the investigated area. The electrode separation varies from 1 to 75 m. The investigation delineated three major layers which are topsoil, which is excavated before any foundation is laid. The second layer delineated was lateritic and the last was weathered layer. From the result obtained, depth to lateritic layer ranges from 1.1 to 9.0 m while resistivity defining the lateritic layer ranges from 150 Ωm to 792 Ωm. Some of the sounding curves generated over the VES stations and Dipole-Dipole Horizontal Profiling fairly correlated with those of the CPT profile. The high cone penetration resistance recorded at CPT point 4 and 5 is manifested as high geoelectric resistivity values recorded at VES 13. This shows that the soil has fairly low clay content. It also seen from the study that the geophysical studies has a greater depth penetration, and it also provide better layer characterization compared to geotechnical studies. The choice of foundation material, clay content and topography elevation should be taken into cognizance, since the load bearing capacity of the lateritic layer was appreciably high.

scholarly journals Application of Electrical Resistivity Method in Site Characterization along Ado – Afao Road, Southwestern Nigeria

2018 ◽  
pp. 1-16
Author(s):  
S. O. Ilugbo ◽  
A. D. Adebiyi ◽  
S. O. Olaogun ◽  
T. Egunjobi
Keyword(s):  
Clay Content ◽  
Geophysical Investigation ◽  
Clayey Sand ◽  
Engineering Structures ◽  
Southwestern Nigeria ◽  
Resistivity Method ◽  
Sandy Clay ◽  
Geophysical Study ◽  
Weathered Layer ◽  
Subsurface Layers

A geophysical study was carried out at a proposed location for the construction of a structure along Ado-Afao road, Southwestern Nigeria. The aim of the study is to evaluate the electrical properties of the soil for Founding of Engineering structures. The geophysical investigation involved the Vertical Electrical Sounding (VES) technique using the Schlumberger configuration with a total of twenty-one (21) VES within the investigated area. The electrode separation varies from 1 to 100 m. The geoelectric sections identified three to five geoelectric/geologic subsurface layers along the traverses. The topsoil comprising of clay, clayey sand and sandy clay with the resistivity values range from 28 to 800 Ω-m with its thickness varying from 0.4 to 1.9 m. The second layer was found to be lateritic with resistivity ranging between 200 to 800 Ω-m and thickness ranges from 1 to 7.5 m while the weathered layer comprising of clay, clayey sand and sandy clay with resistivity varies from 30 to 220 Ω-m and its thickness varies from 1.2 to 54 m. The fractured basement with resistivity value of 763 Ωm and thickness value of 8m while the fresh basement has a resistivity value ranging from 365 to 2964 Ωm with depth to basement ranging from 8 to 58 m. The resistivity values of the topsoil are indicative of clay, sandy clay and clayey sand. This layer may not be of any special interest since topsoil is normally excavated. Hence, foundation of the proposed structures cannot be found on this layer. Based on the investigation, the subsurface of the study area can be generally classified as incompetent. There is a presence of lateral inhomogeneity of the subsurface layers and geologic features such as fractures and faults. The construction in the area should be founded on the lateritic layer or fresh basement layer coupled with pile foundation to ensure the stability of the building. The choice of foundation material, clay content and topography elevation should be put into consideration.

scholarly journals Spatial Resistivity Mapping of Ureje Dam Floor, Southwestern Nigeria

2020 ◽  
Vol 66 (4) ◽  
pp. 245-255
Author(s):  
J.O. Fatoba ◽  
A.B. Eluwole ◽  
O.A. Sanuade ◽  
M.T. Aroyehun
Keyword(s):  
Storage Capacity ◽  
Geophysical Investigation ◽  
Southwestern Nigeria ◽  
Near Surface ◽  
Water Storage Capacity ◽  
Fractured Bedrock ◽  
Resistivity Method ◽  
Cumulative Response ◽  
Weathered Layer ◽  
Electrical Sounding

AbstractUreje Dam, Ado-Ekiti has witnessed drastic reduction in the water storage capacity of its reservoir. It became imperative to determine the possible cause(s) of the reduction in storage capacity. Geophysical investigation involving the vertical electrical sounding technique of the electrical resistivity method was conducted in the upstream part of the dam. Five lithologic units that include the mud/suspended materials, such as sandy clay, clay, weathered/fractured bedrock and fresh bedrock, were delineated. The respective resistivity and thickness range of the units are 2–19 ohm-m; 147–206 ohm-m, 2–38 ohm-m; 47–236 ohm-m and 455–1516 ohm-m and 0.4–1.9 m; 0.5–2.5 m; 1.0–12.2 m; 7.3–16.4 m and ∞. The thickness of suspended materials, resistivity/thickness of weathered layer and the presence of near-surface impervious layer were used as the main indices for the spatial demarcation of the dam axis in terms of vulnerability to loss of impounded water. Using the cumulative response of the indices, the study concluded that the eastern to southeastern parts of the dam axis showed the highest indications of vulnerability to loss of impounded water.

Application of Electrical Resistivity in Buildings Foundation Investigation in Ibese Southwestern Nigeria

2014 ◽  
Vol 1 (2) ◽  
pp. 91-102
Author(s):  
Falae Philips Omowumi
Keyword(s):  
Shallow Foundation ◽  
Geophysical Investigation ◽  
Engineering Structures ◽  
Building Site ◽  
Southwestern Nigeria ◽  
2D Inversion ◽  
One Dimensional ◽  
Southwest Nigeria ◽  
Electrical Sounding ◽  
Geological Units

Application of geophysical investigation has been carried out using Vertical Electrical Sounding (VES) at the proposed building site in Ibese Southwest Nigeria to determine the geophysical parameters that can be used to evaluate the structural competence of the subsurface geological characteristics of the site for construction purposes and building development. The Schlumberger configuration was used for the data acquisition. One-dimensional numerical inversion of individual DC resistivity was used to enhance the processing of the results for better achievement of the aim of the study. Models obtained from the 2D inversion of each VES were used for construction of geo-electric sections which exhibit the main geo-electric characteristics of the geological units present in the area. The interpretation results showed that the geo-electric sections consist of three-four layers namely: topsoil, pebble clay, limestone and sand/limestone. The layer resistivities and thicknesses range from 11 - 404 Ohm-m/0.4 - 1.5 m, 2-210 Ohm-m/ 0.8 - 9.2m and 33 - 160Ohm-m respectively. The investigation revealed that the sand/limestone litho unit is to be the most competent for shallow foundation for small to medium engineering structures.  

scholarly journals Hydro-geologic, Corrosivity and Geotechnical Implications of Geoelectric Sounding Survey at FUTA Cooperative Housing Estate, Ilaramokin near Akure Southwestern Nigeria

2020 ◽  
pp. 40-50
Author(s):  
I. A. Adeyemo ◽  
V. O. Iwuala ◽  
T. S. Fadare ◽  
E. O. Otayemi
Keyword(s):  
Groundwater Potential ◽  
Housing Estate ◽  
Engineering Structures ◽  
Southwestern Nigeria ◽  
Low Resistivity ◽  
Cooperative Housing ◽  
Weathered Layer ◽  
Subsurface Layers ◽  
Electrical Sounding ◽  
Structural Failures

Aim: Groundwater potential evaluation, corrosivity and geotechnical competence investigations of the subsurface layers were carried at FUTA Cooperative Housing Estate, Ilaramokin near Akure Southwestern Nigeria in order to facilitate proper positioning of facilities within the estate. Methodology: A total of 14 vertical electrical sounding (VES) data was acquired across the estate using Schlumberger array. Results: The VES survey results delineated 3 - 5 geoelectric layers across the estate which corresponds to the topsoil, weathered layer, partially weathered basement, partially fractured basement and the presumed fresh bedrock. The groundwater potential map of the estate revealed that the groundwater potential is moderate (GWP of 0.5 - 0.75) to high (GWP of 0.75 - 1.0) in the western and southeastern parts of the estate. The depth slice corrosivity maps (1.0, 2.0 and 3.0 m) of the estate indicated that the corrosivity of the subsurface layers within the estate reduces with depth. The 0.5 m depth slice isoresistivity map of the estate indicates that the central and a segment of the southwestern parts of the estate are characterized with low resistivity (50 - 100 Ωm) indicating incompetence, while the estate flanks (west and east) are considered to be moderately competent (100 - 350 Ωm). Likewise, the 1.0 m depth slice isoresistivity map of the estate reveals that the central and western parts of the estate are characterized with low resistivity (50 - 100 Ωm) suggesting incompetent layer, while the northern, southern and eastern parts of the estate are moderately competent (100 - 350 Ωm). Conclusion: These results suggested that structural failures can be expected on any engineering structures sited at the central, northern, southern and eastern parts of the estate. Groundwater efforts should be concentrated at the western and southeastern parts of the estate.

scholarly journals Geophysical Assessment of Subsurface Conditions at Proposed Building Sites: Implications for Foundation Failure and Building Collapse

2018 ◽  
Vol 64 (3) ◽  
pp. 8-20
Author(s):  
Stephen Oluwafemi Ariyo ◽  
Julius Ogunmola Fatoba ◽  
Olateju O. Bayewu ◽  
Kamaldeen Olakunle Omosanya ◽  
Muhedeen Ajibola Lawal
Keyword(s):  
Geological Mapping ◽  
Geophysical Investigation ◽  
Building Collapse ◽  
Resistivity Imaging ◽  
Geotechnical Investigations ◽  
Weathered Layer ◽  
Electrical Sounding ◽  
2D Resistivity Imaging ◽  
2D Resistivity ◽  
Wenner Array

Abstract Building collapse has been a recurrent environmental hazard in Nigeria in the last two decades. This is a corollary of inadequate foundation investigation prior to construction, poor government policies, and general lack of awareness on the importance of geophysical and geotechnical investigations. In this study, geological mapping and detailed geophysical investigation using Electrical Resistivity Imaging (ERI) and Vertical Electrical Sounding (VES) were carried out to understand the suitability of proposed building sites at the main campus of the Olabisi Onabanjo University (OOU), Ago-Iwoye, Nigeria for construction. Both Wenner array and dipole-dipole were used for profiling and Schlumberger for sounding. Four transverses and VES were used in each of the three areas investigated. Our results show that the subsurface of the study areas is underlain by Precambrian basement rock of Nigeria. Rocks in the study area include banded gneiss, porphyroblastic gneiss, biotite-hornblende granite and quartzite schist. The sounding stations across the three areas and 2D resistivity imaging revealed three principal geoelectric layers, the topsoil, the weathered layer and the fractured/fresh basement with varied resistivity values for each layers. At the VES stations, the three geoelectric layers have resistivity values of 62 to 1182 Ωm, 3.2 to 1360Ωm and 87 to 4680 Ωm. On the 2D resistivity imaging profiles, the resistivity of the three layers varies from 2 to 1182 Ωm, 30to 1360 Ωm, and 40 to 2904 Ωm for the topsoil, the weathered basement, and fractured/fresh bedrock. Our work demonstrates that some of the proposed sites are structurally incompetent for engineering or foundation purposes. Excavation of the topsoil and reinforcement are required to sustain the proposed structures.

scholarly journals Application of Vertical Electrical Sounding for Study the Proposed dam site at Wadi Ma’doo, Shabwah Governorate, Yemen

2020 ◽  
Vol 3 (2) ◽  
Keyword(s):  
Two Dimensions ◽  
Shallow Foundation ◽  
Vertical Electrical Sounding ◽  
Electrode Spacing ◽  
Geophysical Investigation ◽  
Engineering Structures ◽  
Geoelectric Section ◽  
True Resistivity ◽  
Dam Site ◽  
Electrical Sounding

Application of geophysical investigation has been carried out using Vertical Electrical Sounding (VES) at the proposed site in wadi Ma’doo, Shabwah Governorate, Yemen to determine the geophysical parameters that can be used to evaluate the subsurface geological layering characteristics of the selection proposed site for dam construction. The Schlumberger array was used for the data acquisition. One-dimensional numerical inversion of individual DC resistivity was used to enhance the processing of the results for better achievement of the aim of the study. Model obtained from the 2D inversion of each VES were used for construction of geoelectric section which exhibit the main geoelectric characteristics of the geological units present in the site. The interpretation of the field data was carried out using the IP12WIN software, which converts the apparent resistivity as a function of electrode spacing to the true resistivity as a function of depth in two dimensions. The interpretation results showed that the geoelectric section consists of three layers namely: boulders and gravels, sandy to pebbly and hard limestone. The layer resistivities and thicknesses range from 18.17 to 746.20 Ω.m/0.20 to 1.084 m, 53 to 60 Ω.m/ 0.20 to 3.059 m and 455 to 1890 Ω.m, respectively. The investigation revealed that the limestone rocks is suitable for shallow foundation for proposed dam engineering structures.

scholarly journals Geophysical and Geotechnical Site Characterization at Lagos Central Area of Lagos State, Nigeria

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Rafiu Adegbola ◽  
Kayode Oyedele ◽  
Elizabeth Abidoye
Keyword(s):  
Central Area ◽  
Maximum Load ◽  
Shallow Foundation ◽  
Silty Sand ◽  
Cone Penetration ◽  
Engineering Structures ◽  
Shallow Subsurface ◽  
Subsurface Geology ◽  
Electrical Sounding ◽  
A Site

Introduction: Geophysical characterization refers to the collection of information associated with subsurface features. Geotechnical involves engineering structural performance studies which are used to obtain information on the physical properties of soil and rock around a site to design earthworks and foundations for proposed structures and for repair of distress to earthworks and structures caused by subsurface conditions. Aim: The study was aimed at characterizing the subsurface formations for the purpose of determining its capacity to withstand engineering structures. Materials and Methods: Geophysical techniques involving eight (8) vertical electrical sounding (VES) and Wenner array were carried out with two (2) traverses. Geotechnical investigation involving cone penetration test (CPT) was also carried out. Results: The results obtained were presented as 1D resistivity profiles and Pseudo-sections of 2-D. Three (3) geo-electric layers were delineated within the study area and these comprise of topsoil, peat or clay and silty sand. The CPT results were used in the calculation of bearing capacity using Bustamante and Gianeselli equation for pile foundations and Meyehorf equation to determine the maximum load the materials can withstand respectively. Conclusion: The shallow subsurface geology was adjudged to be mechanically unstable with low penetration resistance values up to the depth of 11m. The methods conformed and confirmed that shallow foundation was considered unsuitable for the intended engineering structure. Keywords: Meyehorf, Bustamante and Gianeselli, Subsurface, Geology, Unstable, Foundation.

scholarly journals Geophysical investigation of foundation failure at Medina Estate, Lagos, Southwestern Nigeria

2020 ◽  
Vol 18 ◽  
pp. 35-47
Author(s):  
M.A. Oladunjoye ◽  
K.O. Adejato ◽  
A.O. Ogunkoya
Keyword(s):  
Ground Penetrating Radar ◽  
Well Logs ◽  
Vertical Electrical Sounding ◽  
Peat Layer ◽  
Geophysical Investigation ◽  
Southwestern Nigeria ◽  
Electrical Sounding ◽  
Ground Penetrating ◽  
Low Amplitude ◽  
Foundation Failure

Integrated geophysical investigation involving Ground Penetrating Radar (GPR) and Electrical Resistivity methods were carried out at Medina Estate, Lagos southwestern Nigeria to map the subsurface lithology in order to delineate its peat stratigraphy that has been causing foundation failure in the area. Twenty-one traverses (varying from 35-880 m in length) of Ground Penetrating Radar (GPR) survey were conducted along the streets of Medina trending NE-SW and NW-SE directions using the Mala 250 MHZ bi-static shielded antenna. Thirty-six Vertical Electrical Soundings (VES) were carried out using Schlumberger electrode array at some selected points along the established traverses within the area. The GPR data were processed into radar section using Rad Explorer software. The VES data were interpreted quantitatively using the partial curve matching method and 1-D forward modeling with Win Resist Software. Available litho-logs from boreholes drilled within the area were compared with the geophysical results.  Results of the GPR survey delineated three geologic layers which include the topsoil with high amplitude, parallel to sub parallel, horizontal reflections, with thickness varying from 1 to 2 m across the entire profiles and composed of lateritic clay; peat layer with low amplitude, parallel sinuous/wavy reflections with depth of occurrence ranging from 2.0 to 8 m and clay with low amplitude, planar, horizontal, sub-parallel reflections underlying the peat layer. Vertical Electrical Sounding results revealed the presence of three geological layers which are the topsoil, peat and clay and sandy clay with layer resistivity values ranging from 20- 225 Ωm, 5 – 90 Ωm and 36 to 366 Ωm and thickness values ranging from 0.5 – 2 m, 4.0-29.0 m and infinity respectively. Borehole information confirms the occurrence of shallow peat with depth ranging from 1.5 to 9 m and clay layer with depth ranging from 9 to 21 m beneath the area. The GPR survey results correlates with the well logs acquired in the study area. Based on the correlation of the geophysical results with the well logs, the GPR gives better information about the peat layer compared to the Electrical ResistivityMethod. The information obtained from this study shows that the soils at shallow depth are organic soils which are difficult foundation materials because they exhibit very high compressibility, as such making shallow foundation impossible except some form of soil improvement is carried out. The alternative approach is the adoption of deep foundations in form of piles. Keywords: Foundation Failure, Geophysical Investigation, Ground Penetrating Radar, Vertical Electrical Sounding, Peat.

scholarly journals Geoelectrical and Geotechnical Investigations of Subsurface Corrosivity in Ondo State Industrial Layout, Akure, Southwestern Nigeria

2018 ◽  
Vol 18 (1) ◽  
pp. 20-31
Author(s):  
Igbagbo Adedotun Adeyemo ◽  
Olumide Abiola Olumilola ◽  
Michael Adewale Ibitomi
Keyword(s):  
Additive Model ◽  
Central Area ◽  
Liquid Limit ◽  
Plasticity Index ◽  
Southwestern Nigeria ◽  
Geotechnical Investigations ◽  
Weathered Layer ◽  
Electrical Sounding ◽  
Ondo State ◽  
Industrial Layout

Fifty two vertical electrical sounding (VES) data and six subsurface soil samples were collected at Ondo State Industrial Layout, Akure, south-western Nigeria in order to determine the subsurface corrosivity. The VES results delineated 3 to 5 geoelectric layers across the area, which correspond to topsoil, weathered layer, weathered basement, weathered/fractured basement and the presumed fresh bedrock. The layer resistivity values range from 22 to 602 ohm-m, 7 to 2468 ohm-m, 17 to 436 ohm-m, 25 to 39 ohm-m and 203 to 10023 ohm-m in the topsoil, weathered layer, weathered basement, weathered/fractured basement and the presumed fresh bedrock respectively. The iso-resistivity maps at depth slices of 1 and 2 m show that the northeastern, southeastern and the upper central part of the area are non-corrosive (above 350 ohm-m) to slightly corrosive (250 - 350 ohm-m), while the lower central, northwestern and southwestern parts of the area are moderately (150 - 250 ohm-m) to strongly corrosive (60 - 150 ohm-m).  Soil sample analysis shows liquid limit results that  vary from 37.6 to 59.7, while the plasticity limit results vary from 29.3 to 42.5 and all the plasticity index plots were below the A line indicating presence of non-plastic clay. The natural moisture content values vary from 21.4 to 35.5 %. The 2 m depth slice isoresistivity map and clay plasticity factor were synthesized using additive model to generate subsurface CR-index corrosivity model map which indicates that the northwestern, north-eastern and southern parts of the area are moderately (0.4 - 0.6) to strongly corrosive (0.6 - 0.8), while the upper central area and the flanks are slightly corrosive. The moderately and strongly corrosive zones correspond to the low elevation and water logged zones of the study area. The corrosivity model map was validated by the pH and corrosivity data. Keywords: Geotechnical, Liquid Limit, Plastic Limit, Plasticity Index, Clay Plasticity

scholarly journals Borehole inventory, groundwater potential and water quality studies in Ayede Ekiti, Southwestern Nigeria

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Olusegun O. Ige ◽  
Hycent O. Ameh ◽  
Ifeoluwa M. Olaleye
Keyword(s):  
Physicochemical Characteristics ◽  
Groundwater Potential ◽  
Water Levels ◽  
World Health ◽  
Geophysical Investigation ◽  
Southwestern Nigeria ◽  
Groundwater Samples ◽  
Static Water ◽  
Weathered Layer ◽  
Health Organization

AbstractThis study aims at determining the state of government provided boreholes, evaluating groundwater potential and quality assessment within the Ayede Ekiti community. 12 Vertical Electrical Soundings (VES) were conducted using Schlumberger array in order to determine geoelectric layers and fracture attributes. Also, 12 water samples were collected from the study area to evaluate physicochemical characteristics of the groundwater. The study revealed average values of total depth of boreholes, static water levels and water column in the boreholes to be 18.77 m, 6.77 m and 11.99 m respectively. 70% of the boreholes are either abandoned, damaged or with evidence of corrosion and encrustation. Geophysical investigation revealed weathered layer thickness ranging from 1.3 to 34.7 m with two regimes of fracture at 40–50 and 75–80 m. The frequency of curve types obtained shows 16.67%, 33.33%, 25%, 8.33%, 8.33% and 8.33% for AK, HA, KH, AA, QH and HK respectively while weathered and fractured basement are identified as the two types of aquifer unit. Results of water analysis unveiled that dominance cations are in order Ca2+ > Na+ > K+ > Mg2+while anions are in the order of HCO3− > Cl− > SO42−. Three types of hydrochemical facies present are CaHCO3 > NaHCO3 > CaCl in 66.67%, 25% and 8.33% respectively. The Wilcox plot suggests the suitability of the groundwater samples for irrigation purposes when compared with the World Health Organization standards. Despite potential for groundwater and good quality of analyzed samples, the problem of water in this community is traceable to inadequacy in exploration, shallow boreholes with consequent seasonal water availability.

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