scholarly journals Evaluating the Earth Subsurface for Civil Engineering Site Characterization in Agege, Southwest Nigeria Using Integrated Geoelectrical and Multichannel Analysis of Surface Wave (MASW)

2021 ◽  
pp. 1-11
Author(s):  
O. J. Airen ◽  
K. K. Oboshenure
Keyword(s):  
Surface Wave ◽  
Civil Engineering ◽  
Vertical Electrical Sounding ◽  
Geophysical Investigation ◽  
Clayey Sand ◽  
Engineering Structures ◽  
Geoelectric Section ◽  
Multichannel Analysis ◽  
Electrical Sounding ◽  
2D Resistivity

A geophysical investigation involving 1D Vertical Electrical Sounding (VES), 2D Electrical Resistivity Imaging (2D ERI) and Multichannel Analysis of Surface Wave (MASW) has been carried out at Agege, Lagos, Nigeria with a view to delineating the subsurface stratigraphy and locate some competent strata/stratum for founding civil engineering structures. Six (6) 200 m long traverses were established within the study area. Along these traverses, 2D ERI were carried out adopting Wenner electrode configuration. Vertical Electrical Sounding (VES) adopting Schlumberger electrode array were carried out at selected points along profiles 1, 2 and 3 to determine the lithological sequence at depth. MASW data also were acquired along traverses 1, 2 and 3. The data were processed and the result yielded interpretable 2D resistivity structure and geoelectrical parameters (layer resistivity, thicknesses and depth) from the VES. The interpreted VES results were used to generate geoelectric section while the MASW resulted in 2D velocity sections. Three subsoils including topsoil, clay and clayey sand/sand were delineated beneath the study area. The resistivity and thickness range of the layers are; topsoil (34.0-54.6 ohm-m, 0.9 – 1.7 m), clay (10.3 – 17.7 ohm-m, 8.9 – 12.3 m) and clayey sand/sand (48.9 – 323 ohm-m) while the S-wave velocity range for the subsoil falls between 40 – 500 m/sec.

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 Assessment of Groundwater Vulnerability to Diesel Contamination at a Telecommunication Mast in Adebayo Area, Ado-Ekiti, Southwestern Nigeria

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Olaseeni Olayiwola ◽  
Fagbemigun Tokunbo ◽  
Ojo Bosede ◽  
Amosun Joel ◽  
Oyebamiji Ajibola
Keyword(s):  
Electrical Resistivity ◽  
Groundwater Vulnerability ◽  
Diesel Oil ◽  
Vertical Electrical Sounding ◽  
Geophysical Investigation ◽  
Southwestern Nigeria ◽  
Geoelectric Section ◽  
Resistivity Method ◽  
Electrical Sounding ◽  
Electrical Resistivity Method

Abstract An appraisal of the groundwater vulnerability to contamination risk at Adebayo in Ado-Ekiti, Southwestern Nigeria, was carried out using the electrical resistivity method of geophysical prospecting. Two traverses of length 100 m each were established for both vertical electrical sounding (VES) and dipole-dipole. Six (6) Vertical Electrical Sounding (VES) and 2-D dipole-dipole profiling techniques of the electrical resistivity method were adopted for the geophysical investigation. The results show variations in resistivity values, depicting four to five geologic layers: the topsoil, laterite, weathered layer, fractured, and the fresh basement. It was observed from the correlation of the geoelectric section and 2-D resistivity image along traverse 1 (TR1) that the groundwater in the study area flows towards the southwestern part, and the fractured basement serves as a migration pathway to the diesel oil in the same direction as groundwater flow. The fractured basement (Well 2) with no lateritic cover has higher resistivity values compare to the fracture zone that was found directly under the mast which was overlain by the laterite. Comparing the resistivity values of Well 1 and 2, Well 2 that was drilled into the fractured basement has more traces of the contaminant than Well 1.

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 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 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 Investigation of Subsurface Structures for Mapping Groundwater Potential of Joseph Ayo Babalola University Campus Environment, Ikeji Arakeji, Osun State, Southwestern Nigeria

2019 ◽  
pp. 1-12
Author(s):  
O. E. Odeyemi ◽  
O. M. Odeyemi ◽  
S. A. Owolabi ◽  
E. A. Mamukuyomi ◽  
R. A. Salako
Keyword(s):  
Electrode Array ◽  
Groundwater Potential ◽  
Vertical Electrical Sounding ◽  
Electrode Spacing ◽  
Clayey Sand ◽  
Southwestern Nigeria ◽  
Current Electrode ◽  
Campus Environment ◽  
Lateritic Clay ◽  
Electrical Sounding

Owing to fast increase in number of staff and students of Joseph Ayo Babalola University, Ikeji Arakeji, Southwestern Nigeria, it is therefore very important to carry out this research in order to recommend the actual locations where boreholes can be sunk for good potential yields of groundwater when the time comes. The aim of this research is to carry out vertical electrical sounding geophysical survey at study area with a view to determining good aquifers that are good for the accumulation of groundwater. The study area is located between latitude 0820225 m to 0820345 m (UTM) Northings and longitude 717320 m to 717450 m (UTM) Eastings. Schlumberger electrode array was employed for the study using Ohmega Resistivity meter for the data acquisition. The geoelectric survey of the study area comprised of twelve vertical electrical soundings, with maximum current electrode spacing (AB) of 100 m. The modeled curves are mainly KH-type. The geoelectric sections generated from the sounding curves revealed 4 major layers earth models. The topsoil is made up of clay, clayey sand/lateritic sand with resistivity and thicknesses varying from 54.7 – 210.1ohm-m and 0.2 –0.8m respectively. The second layer is the lateritic clay with resistivities and thicknesses varying from 334 – 963ohm-m and 1.5 – 10.8m respectively. The third layer constitutes the clay / sandy fractured quartzite and it serves as the aquifer unit. The resistivity values lie between 71.7 and 498 ohm-m while the thicknesses vary from 2.1 – 76.3 m. The fourth layer is the fractured/presumably fresh basement bedrock with the resistivity varying from 1879 – 13991.8 ohm-m. Areas characterized with fractured basement of low resistivity with appreciable thickness are therefore recommended for the siting of boreholes. It is concluded that the vertical electrical sounding points of the study area are good aquifers for groundwater accumulation.

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