SlideShare uma empresa Scribd logo
1 de 19
Baixar para ler offline
GEOELECTRICAL IMAGING
SURVEY FOR ENVIRONMENTAL
AND ENGINEERING STUDIES
 ABSTRACT
 INTRODUCTION
 AIM AND OBJECTIVES
 LOCATION OF STUDY
 GEOLOGY OF STUDY AREA
 LITERATURE REVIEW
 METHODOLOGY
 RESULTS AND INTERPRETATION
A geo-electrical imaging survey was conducted at Uhunmode Local
Government of Edo State Nigeria for site investigation in order to
determine the applicability of 2-D resistivity imaging for Environmental
and Engineering studies The Wenner array was employed. Field data
were obtained for four electrical imaging lines Using PASI Earth
resistivity Meter. The field data was subjected to inversion Using
RES2DINV in order to remove geometrical effects from the pseudosection
and produce an image of true depth and true formation resistivity. Each
of the profiles indicates that resistivity increases with depth. The first 3
layers across the 4 transverse indicates the presence of alluvium deposits
with scattered deposit of clay in small quantities from 0- 20m in depth
underlain by laterite varying about 15m to 20m in thickness, across the
four transverses with resistivity values ranging from 600ohm.m to about
1000ohm.m. The areas of intermediate resistivity zone 1000 to 3500ohm.m
indicate a natural material like sandstone that have been underlain by a
thin layer of shale and The High resistivity zone 3500ohm.m and above
has been interpreted as bedrock which comprises of gravels and granite.
It has been shown that all the areas are competent for the construction and
also suitable for agricultural purpose.
The knowledge of the subsurface geology and the characterization of the
spatial distribution of subsurface physical properties are necessary for effective
environmental monitoring, protection and remediation in polluted areas, as
well as for infrastructure development purposes. These will, in addition, assist
policy makers and environmental managers to take quality decisions required
to preserve and sustain a healthy environment for mankind and the ecosystems
in general, and to effectively and safely manage our natural resources. (
Ahzegbobor P.A 2010 ) The applications of geophysical methods are able to
investigate and determine soil properties, bedrock depth, topography of the
bedrock surface below unconsolidated material, rock type, layer boundaries,
water table, weak zones and expansive clays, inhomogeneities of the
subsurface, cavities, ancient relics and generally underground structures or
bodies that have different physical properties from their geological
surroundings (Aubert, 1984; Carrara et al., 2001). Land that is contaminated
contains substances at the surface or in the subsurface that are actually or
potentially hazardous to health or the environment. In Nigeria there are
numerous sites where land has become contaminated by human activities such
as mining, industry, chemical and hydrocarbon spills and unregulated waste
disposal. Contamination can also occur naturally as a result of the natural
geology of the area, or through intensive agricultural use.
AIM OF STUDY
The aim of this Research is to determine if the Lithology of the survey area
is suitable for environmental and engineering studies.
OBJECTIVES OF STUDY
1. obtain a 2D model of the subsurface by inverting the data set
2. Infer from the 2D model, the rock formation in the subsurface from
which one can tell if the terrain is suitable for environmental and engineering
studies
GEOLOGY OF THE STUDY LOCATION
Geology of the study area is described in the geology of Niger delta.
Niger delta is one of the ten major sedimentary basins of Nigeria. The
others are Abakaliki basin, Anambra Basin, Benue trough, Bida basin,
Bornu-Chad basin, Dahomey basin, Gongola basin, Sokoto basin and
Yola basement complex. These are Western end of the Cameroun
volcanic zone, Northern Nigeria massif and the eastern end of West
African massif. The niger delta is divided into three formations
AKATA FORMATION
It is characterized by a uniform shale development. The formation is a
marine sedimentary sequence laid down in front of an advancing delta.
These prodeltaic shales are medium to dark grey, fairly hard or at
places soft, gumbo-like
and sandy or silty in several places, the shales of this formation were
found to be undercompacted, and therefore mobile, and may contain
lenses of abnormally high-pressured siltstone or fine-grained
sandstone (Allen, 1965; Reyment, 1965; Short & Stauble, 1967 and
Oomkens 1974).
AGBADA FORMATION:
This sequence of strata forms the hydrocarbon prospective sequence in
the Niger delta. The formation is characterized by alternating sandstones
and shales of the delta front, distributary channel, and deltaic plain
origin. Weber (1971) showed that the alternating sequence of sandstones
and shales of the Agbada Formation is of cyclic sequences of marine and
fluvial deposits. The sand content ranges from 50 to 75 %. The sandstones
are medium to fine grained, fairly clean locally calcareous, and shelly.
They consist
dominantly of quartz and potash feldspar with subordinate and illite.
BENIN FORMATION:
This is the uppermost unit of the Niger delta complex. The formation can
be easily distinguished based on its high sand percentage (70 –
1000 %). The sand is dominantly massive highly porous and freshwater
bearing with locally interbedded shale beds, which are considered to be of
braided stream origin. The sands are poorly sorted, ranging from fine to
coarse – grained and occasionally pebbly and they contain abundant
wood, fragments, which become lignitic with depth. Composition,
structure and grain size show deposition in a probably upper deltaic
environment.
BASIC RESISTIVITY THEORY
Electrical resistivity is a material property which indicates how well a
material retards electrical conduction. Resistivity relates electrical
potential and current to the geometrical dimension of the specified region.
It is the reciprocal of conductivity. Electrical conduction takes place due to
the movement of charges. Charges are displaced from the original
equilibrium condition under the application of electric potential.
However, charge density depends on the applied electric field and
resistivity of the material. Resistivity can be defined by considering
current flow through a cylindrical section. To define resistivity, assuming
a cylindrical section with cross sectional area and length of A and L, if
current flow is I through section resistance R and potential drop across the
section is V, then resistivity can be expressed by the following equation
ρ=RA/L……………………………..(1)
where, ρ=Electrical Resistivity, R= Resistance of the material, V= Potential, I= Current , A= Cross
sectional Area and L= Length. The schematics of cylindrical section and flow of current are
presented
Figure1 : Diagram showing the
flow of current through a
cylindrical section
To obtain a good 2-D picture of the subsurface, the coverage of the
measurements must be 2-D as well. The basic resistivity measuring
technique is just similar to the conventional principles. Basically, four
electrodes are required; two for current injection and two electrodes for
potential measurement. Each array has their own advantages and drawbacks
in data acquisition and processing works. But one might has better
sensitivity and resolution power for vertical as well as lateral structural
variations than the other. For instance, Wenner array in multi-electrode
mode has good resolution power for horizontal structure having vertical
variations but weak for horizontally variable geological structures.
Figure 2: Arrangement of
electrodes for a 2D survey
METHODOLOGY
In this research work, the Wenner array in electrical resistivity survey was
adopted. The basic field equipment for this study is the PASI Earth resistivity
meter which displays apparent resistivity values digitally as computed from
ohm’s law. It is powered by a 12.5 V DC power source. Other accessories to the
Earth Resistivity meter includes the booster, four metal electrodes, cables for
current and potential electrodes, harmers (3), measuring tapes, walking, phones
for very long spread. In this configuration, the four electrodes are positioned
symmetrically along a straight line, the current electrodes on the outside and
the potential electrodes on the inside. The spacing between adjacent electrodes is
“a”. With Wenner array, the first step is to make all the possible measurement with
electrode spacing of “1a”. Electrode 1 is used as the first current electrode C1, electrode
2 as the first potential electrode P1, electrode 3 as the second potential electrode P2 and
electrode 4 as the second current electrode C2. For the second measurement, electrodes
2, 3, 4 and 5 are used for C1, P1, P2, and C2 respectively. This is repeated down the line
of electrodes until electrodes 17, 18, 19 and 20 are used for the last measurements with
“1a” spacing. The spacing is then doubled without moving on, the first active electrodes
with “2a” electrode spacing being 1, 3, 5 and 7. For the second measurement, electrodes
2, 4, 6 and 8 are used. This process is repeated down the line until electrodes 14, 16, 18
and 20 are used for the last measurement with spacing “2a”. The same process is
repeated for measurements with “3a”, “4a”, “5a” and “6a” spacing.
To get the best results, the measurements in a field survey should be
carried out in a systematic manner so that, as far as possible, all the
possible measurements are made. This will affect the quality of the
interpretation model obtained from the inversion of the apparent
resistivity measurements (Dahlin and Loke, 1998).
As the electrode spacing increases, the number of measurements
decreases. The number of measurements that can be obtained for each
electrode spacing, for a given number of electrodes along the survey line,
depends on the type of array used. The Wenner array gives the smallest
number of possible measurements compared to the other common arrays
that are used in 2-D surveys.
METHODOLOGY CONT’D
EQUIPMENT USED FOR THE FIELD WORK
INCLUDE
Measuring Tape, Electrodes (Current And Potential Electrode), Cables,
Terrameter, Hammer , Battery, Cutlass, Gps (Global Positioning System
RESULTS
Figure 3: Inversion result from Location 1 Ekiugbo Community
Figure 4 Inversion result from Location 2 Ekiugbo Community
Figure 5: Inversion result from Location 3 Ekiugbo Community
Figure 6: Inversion result from Location 4 Ekiugbo Community
DISCUSSION OF RESULTS
The obtained electrical resistivity images of the subsurface of the four transverses are
presented as models in figures 4.1, 4.2, 4.3 and 4.4. The root mean square errors
obtained in the inverted models were between a minimum of 4.6 to a maximum of
11.7% after 3 iterations for each of the transverse. The maximum depth of penetration
for transverse 1 is 53.6m while that of transverse 2, 3 and 4 are 54.3m, 53.6 and 54.3
respectively. There is a very good correlation between the subsurface images of the
four transverses which shows that the area of investigation has very well compacted
soil with even deposition across the area. Each of the profiles indicates that resistivity
increases with depth. The first 3 layers across the 4 transverse indicates the presence of
alluvium deposits with scattered deposit of clay in small quantities from 0- 20m in
depth underlain by laterite varying about 15m to 20m in thickness, across the four
transverses with resistivity values ranging from 600ohm.m to about 1000ohm.m. The
areas of intermediate resistivity zone 1000 to 3500ohm.m indicate a natural material
like sandstone that have been underlain by a thin layer of shale and The High
resistivity zone 3500ohm.m and above has been interpreted as bedrock which
comprises of gravels and granite. From the interpretation it can be shown that the
investigated area is competent for engineering purpose as revealed by the geoelectric
imaging of all the transverses. It has been shown that all the areas are competent for
the construction of factories that make use of heavy machines However; the area might
be difficult to access aquifer because of its low conductivity. The four study areas also
shows no form of contamination.
CONCLUSION
The electrical resistivity imaging has been successfully
used to determine the subsurface in the study area from
which it was shown that the study area has compacted
soil and an underlying layer of bedrock which comprises
of gravels and granite the area also shows that there are
no faults which could lead to collapse that are suitable
for engineering purpose. There is also no sign of
contamination which means the soil is not polluted and
can be used from agricultural purposes. However low
conductivity of the study area reveals that it is not
aquiferous and thus might not be suitable for water
supply purposes.
REFERENCES
Ahzegbobor P.A 2010 Acquisition geometry and inversion of 3d geoelectrical
resistivity imaging data for environmental and engineering investigations
Allen, J.R.L., 1965. Late Quaternary Niger Delta and adjacent areas: sedimentary
environments and lithofacies. Am. Assoc. Petroleum Geol. Bulletin, Vol. 49, pp.
547-600.
Aubert, M. (1984). Resistivity and magnetic surveys in ground-water prospecting
in volcanic areas. Case history Maar of Beanit, Puy de Dome, France Geophys.
Prospect. 32: 63–554.
Carrara, E. (2001). Resistivity and radar surverys at the archaeological site of
Ercolano. J. Environ. Eng. Geophys. 6: 32–123.
Short, K.L. and stauble A.J. 1967. Outline geology of Niger delta A.A.
PG-V.5. I P. 761 -799.
Oomkens, E., 1974. Lithofacies relations in Late Quaternary Niger delta complex:
- Sedimentology. Vol. 21, pp. 195-222.
THANK
YOU FOR
LISTENING!!!

Mais conteúdo relacionado

Semelhante a EUNICE PRESENTATION.pptx

Research Inventy : International Journal of Engineering and Science
Research Inventy : International Journal of Engineering and ScienceResearch Inventy : International Journal of Engineering and Science
Research Inventy : International Journal of Engineering and Scienceinventy
 
Geo Environmental Investigation of Abuad Dumpsite, Southwestern Nigeria
Geo Environmental Investigation of Abuad Dumpsite, Southwestern NigeriaGeo Environmental Investigation of Abuad Dumpsite, Southwestern Nigeria
Geo Environmental Investigation of Abuad Dumpsite, Southwestern NigeriaIJERA Editor
 
Exploration Geophysics III semester.pdf
Exploration Geophysics III semester.pdfExploration Geophysics III semester.pdf
Exploration Geophysics III semester.pdfSHAHEENAKBAR3
 
Application of vertical electrical sounding and horizontal profiling methods ...
Application of vertical electrical sounding and horizontal profiling methods ...Application of vertical electrical sounding and horizontal profiling methods ...
Application of vertical electrical sounding and horizontal profiling methods ...Alexander Decker
 
Overburden Properties of Abua in Rivers State, Nigeria, from Vertical Electri...
Overburden Properties of Abua in Rivers State, Nigeria, from Vertical Electri...Overburden Properties of Abua in Rivers State, Nigeria, from Vertical Electri...
Overburden Properties of Abua in Rivers State, Nigeria, from Vertical Electri...Associate Professor in VSB Coimbatore
 
G012645256.iosr jmce p1
G012645256.iosr jmce p1G012645256.iosr jmce p1
G012645256.iosr jmce p1IOSR Journals
 
Determination of Thickness of Aquifer with Vertical Electrical Sounding
Determination of Thickness of Aquifer with Vertical Electrical Sounding Determination of Thickness of Aquifer with Vertical Electrical Sounding
Determination of Thickness of Aquifer with Vertical Electrical Sounding iosrjce
 
G012645256.iosr jmce p1
G012645256.iosr jmce p1G012645256.iosr jmce p1
G012645256.iosr jmce p1IOSR Journals
 
Detection of shallow Aquifers Using Vertical Electrical Sounding in Abua Town...
Detection of shallow Aquifers Using Vertical Electrical Sounding in Abua Town...Detection of shallow Aquifers Using Vertical Electrical Sounding in Abua Town...
Detection of shallow Aquifers Using Vertical Electrical Sounding in Abua Town...Associate Professor in VSB Coimbatore
 
Subsurface 2D Image Analyses of the Uyangha Basement Area, South-Eastern Nigeria
Subsurface 2D Image Analyses of the Uyangha Basement Area, South-Eastern NigeriaSubsurface 2D Image Analyses of the Uyangha Basement Area, South-Eastern Nigeria
Subsurface 2D Image Analyses of the Uyangha Basement Area, South-Eastern NigeriaIOSR Journals
 
Electrical resistivity sounding for subsurface delineation and evaluation of ...
Electrical resistivity sounding for subsurface delineation and evaluation of ...Electrical resistivity sounding for subsurface delineation and evaluation of ...
Electrical resistivity sounding for subsurface delineation and evaluation of ...Alexander Decker
 
Application of Very Low Frequency- Electromagnetic (VLF-EM) Method to Map Fra...
Application of Very Low Frequency- Electromagnetic (VLF-EM) Method to Map Fra...Application of Very Low Frequency- Electromagnetic (VLF-EM) Method to Map Fra...
Application of Very Low Frequency- Electromagnetic (VLF-EM) Method to Map Fra...theijes
 
Groundwater Studies in Abakaliki Using Electrical Resistivity Method
Groundwater Studies in Abakaliki Using Electrical Resistivity MethodGroundwater Studies in Abakaliki Using Electrical Resistivity Method
Groundwater Studies in Abakaliki Using Electrical Resistivity Methodiosrjce
 
Site Investigation of Subsurface Lithology of Ignatius Ajuru University of Ed...
Site Investigation of Subsurface Lithology of Ignatius Ajuru University of Ed...Site Investigation of Subsurface Lithology of Ignatius Ajuru University of Ed...
Site Investigation of Subsurface Lithology of Ignatius Ajuru University of Ed...Associate Professor in VSB Coimbatore
 
Resistivity Imaging of Shallow Sediments within University of Maiduguri Campu...
Resistivity Imaging of Shallow Sediments within University of Maiduguri Campu...Resistivity Imaging of Shallow Sediments within University of Maiduguri Campu...
Resistivity Imaging of Shallow Sediments within University of Maiduguri Campu...iosrjce
 
GEOLOGICAL INVESTIGATTION OF PERCOLATION TANK
GEOLOGICAL INVESTIGATTION OF PERCOLATION TANKGEOLOGICAL INVESTIGATTION OF PERCOLATION TANK
GEOLOGICAL INVESTIGATTION OF PERCOLATION TANKIRJET Journal
 
Geophysical investigation into the cause(s) of structural failure within baco...
Geophysical investigation into the cause(s) of structural failure within baco...Geophysical investigation into the cause(s) of structural failure within baco...
Geophysical investigation into the cause(s) of structural failure within baco...Alexander Decker
 

Semelhante a EUNICE PRESENTATION.pptx (20)

Research Inventy : International Journal of Engineering and Science
Research Inventy : International Journal of Engineering and ScienceResearch Inventy : International Journal of Engineering and Science
Research Inventy : International Journal of Engineering and Science
 
Geo Environmental Investigation of Abuad Dumpsite, Southwestern Nigeria
Geo Environmental Investigation of Abuad Dumpsite, Southwestern NigeriaGeo Environmental Investigation of Abuad Dumpsite, Southwestern Nigeria
Geo Environmental Investigation of Abuad Dumpsite, Southwestern Nigeria
 
Exploration Geophysics III semester.pdf
Exploration Geophysics III semester.pdfExploration Geophysics III semester.pdf
Exploration Geophysics III semester.pdf
 
Electrical method
Electrical methodElectrical method
Electrical method
 
Application of vertical electrical sounding and horizontal profiling methods ...
Application of vertical electrical sounding and horizontal profiling methods ...Application of vertical electrical sounding and horizontal profiling methods ...
Application of vertical electrical sounding and horizontal profiling methods ...
 
Overburden Properties of Abua in Rivers State, Nigeria, from Vertical Electri...
Overburden Properties of Abua in Rivers State, Nigeria, from Vertical Electri...Overburden Properties of Abua in Rivers State, Nigeria, from Vertical Electri...
Overburden Properties of Abua in Rivers State, Nigeria, from Vertical Electri...
 
Gi2511541161
Gi2511541161Gi2511541161
Gi2511541161
 
Gi2511541161
Gi2511541161Gi2511541161
Gi2511541161
 
G012645256.iosr jmce p1
G012645256.iosr jmce p1G012645256.iosr jmce p1
G012645256.iosr jmce p1
 
Determination of Thickness of Aquifer with Vertical Electrical Sounding
Determination of Thickness of Aquifer with Vertical Electrical Sounding Determination of Thickness of Aquifer with Vertical Electrical Sounding
Determination of Thickness of Aquifer with Vertical Electrical Sounding
 
G012645256.iosr jmce p1
G012645256.iosr jmce p1G012645256.iosr jmce p1
G012645256.iosr jmce p1
 
Detection of shallow Aquifers Using Vertical Electrical Sounding in Abua Town...
Detection of shallow Aquifers Using Vertical Electrical Sounding in Abua Town...Detection of shallow Aquifers Using Vertical Electrical Sounding in Abua Town...
Detection of shallow Aquifers Using Vertical Electrical Sounding in Abua Town...
 
Subsurface 2D Image Analyses of the Uyangha Basement Area, South-Eastern Nigeria
Subsurface 2D Image Analyses of the Uyangha Basement Area, South-Eastern NigeriaSubsurface 2D Image Analyses of the Uyangha Basement Area, South-Eastern Nigeria
Subsurface 2D Image Analyses of the Uyangha Basement Area, South-Eastern Nigeria
 
Electrical resistivity sounding for subsurface delineation and evaluation of ...
Electrical resistivity sounding for subsurface delineation and evaluation of ...Electrical resistivity sounding for subsurface delineation and evaluation of ...
Electrical resistivity sounding for subsurface delineation and evaluation of ...
 
Application of Very Low Frequency- Electromagnetic (VLF-EM) Method to Map Fra...
Application of Very Low Frequency- Electromagnetic (VLF-EM) Method to Map Fra...Application of Very Low Frequency- Electromagnetic (VLF-EM) Method to Map Fra...
Application of Very Low Frequency- Electromagnetic (VLF-EM) Method to Map Fra...
 
Groundwater Studies in Abakaliki Using Electrical Resistivity Method
Groundwater Studies in Abakaliki Using Electrical Resistivity MethodGroundwater Studies in Abakaliki Using Electrical Resistivity Method
Groundwater Studies in Abakaliki Using Electrical Resistivity Method
 
Site Investigation of Subsurface Lithology of Ignatius Ajuru University of Ed...
Site Investigation of Subsurface Lithology of Ignatius Ajuru University of Ed...Site Investigation of Subsurface Lithology of Ignatius Ajuru University of Ed...
Site Investigation of Subsurface Lithology of Ignatius Ajuru University of Ed...
 
Resistivity Imaging of Shallow Sediments within University of Maiduguri Campu...
Resistivity Imaging of Shallow Sediments within University of Maiduguri Campu...Resistivity Imaging of Shallow Sediments within University of Maiduguri Campu...
Resistivity Imaging of Shallow Sediments within University of Maiduguri Campu...
 
GEOLOGICAL INVESTIGATTION OF PERCOLATION TANK
GEOLOGICAL INVESTIGATTION OF PERCOLATION TANKGEOLOGICAL INVESTIGATTION OF PERCOLATION TANK
GEOLOGICAL INVESTIGATTION OF PERCOLATION TANK
 
Geophysical investigation into the cause(s) of structural failure within baco...
Geophysical investigation into the cause(s) of structural failure within baco...Geophysical investigation into the cause(s) of structural failure within baco...
Geophysical investigation into the cause(s) of structural failure within baco...
 

Último

Engineering Mechanics Chapter 5 Equilibrium of a Rigid Body
Engineering Mechanics  Chapter 5  Equilibrium of a Rigid BodyEngineering Mechanics  Chapter 5  Equilibrium of a Rigid Body
Engineering Mechanics Chapter 5 Equilibrium of a Rigid BodyAhmadHajasad2
 
Modelling Guide for Timber Structures - FPInnovations
Modelling Guide for Timber Structures - FPInnovationsModelling Guide for Timber Structures - FPInnovations
Modelling Guide for Timber Structures - FPInnovationsYusuf Yıldız
 
Lecture 1: Basics of trigonometry (surveying)
Lecture 1: Basics of trigonometry (surveying)Lecture 1: Basics of trigonometry (surveying)
Lecture 1: Basics of trigonometry (surveying)Bahzad5
 
SUMMER TRAINING REPORT ON BUILDING CONSTRUCTION.docx
SUMMER TRAINING REPORT ON BUILDING CONSTRUCTION.docxSUMMER TRAINING REPORT ON BUILDING CONSTRUCTION.docx
SUMMER TRAINING REPORT ON BUILDING CONSTRUCTION.docxNaveenVerma126
 
Gender Bias in Engineer, Honors 203 Project
Gender Bias in Engineer, Honors 203 ProjectGender Bias in Engineer, Honors 203 Project
Gender Bias in Engineer, Honors 203 Projectreemakb03
 
GENERAL CONDITIONS FOR CONTRACTS OF CIVIL ENGINEERING WORKS
GENERAL CONDITIONS  FOR  CONTRACTS OF CIVIL ENGINEERING WORKS GENERAL CONDITIONS  FOR  CONTRACTS OF CIVIL ENGINEERING WORKS
GENERAL CONDITIONS FOR CONTRACTS OF CIVIL ENGINEERING WORKS Bahzad5
 
Mohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptxMohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptxKISHAN KUMAR
 
Transforming Process Safety Management: Challenges, Benefits, and Transition ...
Transforming Process Safety Management: Challenges, Benefits, and Transition ...Transforming Process Safety Management: Challenges, Benefits, and Transition ...
Transforming Process Safety Management: Challenges, Benefits, and Transition ...soginsider
 
IT3401-WEB ESSENTIALS PRESENTATIONS.pptx
IT3401-WEB ESSENTIALS PRESENTATIONS.pptxIT3401-WEB ESSENTIALS PRESENTATIONS.pptx
IT3401-WEB ESSENTIALS PRESENTATIONS.pptxSAJITHABANUS
 
Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...
Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...
Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...Sean Meyn
 
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...Amil baba
 
ChatGPT-and-Generative-AI-Landscape Working of generative ai search
ChatGPT-and-Generative-AI-Landscape Working of generative ai searchChatGPT-and-Generative-AI-Landscape Working of generative ai search
ChatGPT-and-Generative-AI-Landscape Working of generative ai searchrohitcse52
 
Test of Significance of Large Samples for Mean = µ.pptx
Test of Significance of Large Samples for Mean = µ.pptxTest of Significance of Large Samples for Mean = µ.pptx
Test of Significance of Large Samples for Mean = µ.pptxHome
 
Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...
Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...
Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...Amil baba
 
Technology Features of Apollo HDD Machine, Its Technical Specification with C...
Technology Features of Apollo HDD Machine, Its Technical Specification with C...Technology Features of Apollo HDD Machine, Its Technical Specification with C...
Technology Features of Apollo HDD Machine, Its Technical Specification with C...Apollo Techno Industries Pvt Ltd
 
Basic Principle of Electrochemical Sensor
Basic Principle of  Electrochemical SensorBasic Principle of  Electrochemical Sensor
Basic Principle of Electrochemical SensorTanvir Moin
 

Último (20)

Engineering Mechanics Chapter 5 Equilibrium of a Rigid Body
Engineering Mechanics  Chapter 5  Equilibrium of a Rigid BodyEngineering Mechanics  Chapter 5  Equilibrium of a Rigid Body
Engineering Mechanics Chapter 5 Equilibrium of a Rigid Body
 
Lecture 2 .pptx
Lecture 2                            .pptxLecture 2                            .pptx
Lecture 2 .pptx
 
Modelling Guide for Timber Structures - FPInnovations
Modelling Guide for Timber Structures - FPInnovationsModelling Guide for Timber Structures - FPInnovations
Modelling Guide for Timber Structures - FPInnovations
 
Litature Review: Research Paper work for Engineering
Litature Review: Research Paper work for EngineeringLitature Review: Research Paper work for Engineering
Litature Review: Research Paper work for Engineering
 
Lecture 1: Basics of trigonometry (surveying)
Lecture 1: Basics of trigonometry (surveying)Lecture 1: Basics of trigonometry (surveying)
Lecture 1: Basics of trigonometry (surveying)
 
SUMMER TRAINING REPORT ON BUILDING CONSTRUCTION.docx
SUMMER TRAINING REPORT ON BUILDING CONSTRUCTION.docxSUMMER TRAINING REPORT ON BUILDING CONSTRUCTION.docx
SUMMER TRAINING REPORT ON BUILDING CONSTRUCTION.docx
 
Gender Bias in Engineer, Honors 203 Project
Gender Bias in Engineer, Honors 203 ProjectGender Bias in Engineer, Honors 203 Project
Gender Bias in Engineer, Honors 203 Project
 
GENERAL CONDITIONS FOR CONTRACTS OF CIVIL ENGINEERING WORKS
GENERAL CONDITIONS  FOR  CONTRACTS OF CIVIL ENGINEERING WORKS GENERAL CONDITIONS  FOR  CONTRACTS OF CIVIL ENGINEERING WORKS
GENERAL CONDITIONS FOR CONTRACTS OF CIVIL ENGINEERING WORKS
 
Mohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptxMohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptx
 
Transforming Process Safety Management: Challenges, Benefits, and Transition ...
Transforming Process Safety Management: Challenges, Benefits, and Transition ...Transforming Process Safety Management: Challenges, Benefits, and Transition ...
Transforming Process Safety Management: Challenges, Benefits, and Transition ...
 
IT3401-WEB ESSENTIALS PRESENTATIONS.pptx
IT3401-WEB ESSENTIALS PRESENTATIONS.pptxIT3401-WEB ESSENTIALS PRESENTATIONS.pptx
IT3401-WEB ESSENTIALS PRESENTATIONS.pptx
 
Présentation IIRB 2024 Chloe Dufrane.pdf
Présentation IIRB 2024 Chloe Dufrane.pdfPrésentation IIRB 2024 Chloe Dufrane.pdf
Présentation IIRB 2024 Chloe Dufrane.pdf
 
Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...
Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...
Quasi-Stochastic Approximation: Algorithm Design Principles with Applications...
 
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
 
ChatGPT-and-Generative-AI-Landscape Working of generative ai search
ChatGPT-and-Generative-AI-Landscape Working of generative ai searchChatGPT-and-Generative-AI-Landscape Working of generative ai search
ChatGPT-and-Generative-AI-Landscape Working of generative ai search
 
Test of Significance of Large Samples for Mean = µ.pptx
Test of Significance of Large Samples for Mean = µ.pptxTest of Significance of Large Samples for Mean = µ.pptx
Test of Significance of Large Samples for Mean = µ.pptx
 
Lecture 4 .pdf
Lecture 4                              .pdfLecture 4                              .pdf
Lecture 4 .pdf
 
Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...
Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...
Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...
 
Technology Features of Apollo HDD Machine, Its Technical Specification with C...
Technology Features of Apollo HDD Machine, Its Technical Specification with C...Technology Features of Apollo HDD Machine, Its Technical Specification with C...
Technology Features of Apollo HDD Machine, Its Technical Specification with C...
 
Basic Principle of Electrochemical Sensor
Basic Principle of  Electrochemical SensorBasic Principle of  Electrochemical Sensor
Basic Principle of Electrochemical Sensor
 

EUNICE PRESENTATION.pptx

  • 1. GEOELECTRICAL IMAGING SURVEY FOR ENVIRONMENTAL AND ENGINEERING STUDIES
  • 2.  ABSTRACT  INTRODUCTION  AIM AND OBJECTIVES  LOCATION OF STUDY  GEOLOGY OF STUDY AREA  LITERATURE REVIEW  METHODOLOGY  RESULTS AND INTERPRETATION
  • 3. A geo-electrical imaging survey was conducted at Uhunmode Local Government of Edo State Nigeria for site investigation in order to determine the applicability of 2-D resistivity imaging for Environmental and Engineering studies The Wenner array was employed. Field data were obtained for four electrical imaging lines Using PASI Earth resistivity Meter. The field data was subjected to inversion Using RES2DINV in order to remove geometrical effects from the pseudosection and produce an image of true depth and true formation resistivity. Each of the profiles indicates that resistivity increases with depth. The first 3 layers across the 4 transverse indicates the presence of alluvium deposits with scattered deposit of clay in small quantities from 0- 20m in depth underlain by laterite varying about 15m to 20m in thickness, across the four transverses with resistivity values ranging from 600ohm.m to about 1000ohm.m. The areas of intermediate resistivity zone 1000 to 3500ohm.m indicate a natural material like sandstone that have been underlain by a thin layer of shale and The High resistivity zone 3500ohm.m and above has been interpreted as bedrock which comprises of gravels and granite. It has been shown that all the areas are competent for the construction and also suitable for agricultural purpose.
  • 4. The knowledge of the subsurface geology and the characterization of the spatial distribution of subsurface physical properties are necessary for effective environmental monitoring, protection and remediation in polluted areas, as well as for infrastructure development purposes. These will, in addition, assist policy makers and environmental managers to take quality decisions required to preserve and sustain a healthy environment for mankind and the ecosystems in general, and to effectively and safely manage our natural resources. ( Ahzegbobor P.A 2010 ) The applications of geophysical methods are able to investigate and determine soil properties, bedrock depth, topography of the bedrock surface below unconsolidated material, rock type, layer boundaries, water table, weak zones and expansive clays, inhomogeneities of the subsurface, cavities, ancient relics and generally underground structures or bodies that have different physical properties from their geological surroundings (Aubert, 1984; Carrara et al., 2001). Land that is contaminated contains substances at the surface or in the subsurface that are actually or potentially hazardous to health or the environment. In Nigeria there are numerous sites where land has become contaminated by human activities such as mining, industry, chemical and hydrocarbon spills and unregulated waste disposal. Contamination can also occur naturally as a result of the natural geology of the area, or through intensive agricultural use.
  • 5. AIM OF STUDY The aim of this Research is to determine if the Lithology of the survey area is suitable for environmental and engineering studies. OBJECTIVES OF STUDY 1. obtain a 2D model of the subsurface by inverting the data set 2. Infer from the 2D model, the rock formation in the subsurface from which one can tell if the terrain is suitable for environmental and engineering studies
  • 6. GEOLOGY OF THE STUDY LOCATION Geology of the study area is described in the geology of Niger delta. Niger delta is one of the ten major sedimentary basins of Nigeria. The others are Abakaliki basin, Anambra Basin, Benue trough, Bida basin, Bornu-Chad basin, Dahomey basin, Gongola basin, Sokoto basin and Yola basement complex. These are Western end of the Cameroun volcanic zone, Northern Nigeria massif and the eastern end of West African massif. The niger delta is divided into three formations AKATA FORMATION It is characterized by a uniform shale development. The formation is a marine sedimentary sequence laid down in front of an advancing delta. These prodeltaic shales are medium to dark grey, fairly hard or at places soft, gumbo-like and sandy or silty in several places, the shales of this formation were found to be undercompacted, and therefore mobile, and may contain lenses of abnormally high-pressured siltstone or fine-grained sandstone (Allen, 1965; Reyment, 1965; Short & Stauble, 1967 and Oomkens 1974).
  • 7. AGBADA FORMATION: This sequence of strata forms the hydrocarbon prospective sequence in the Niger delta. The formation is characterized by alternating sandstones and shales of the delta front, distributary channel, and deltaic plain origin. Weber (1971) showed that the alternating sequence of sandstones and shales of the Agbada Formation is of cyclic sequences of marine and fluvial deposits. The sand content ranges from 50 to 75 %. The sandstones are medium to fine grained, fairly clean locally calcareous, and shelly. They consist dominantly of quartz and potash feldspar with subordinate and illite. BENIN FORMATION: This is the uppermost unit of the Niger delta complex. The formation can be easily distinguished based on its high sand percentage (70 – 1000 %). The sand is dominantly massive highly porous and freshwater bearing with locally interbedded shale beds, which are considered to be of braided stream origin. The sands are poorly sorted, ranging from fine to coarse – grained and occasionally pebbly and they contain abundant wood, fragments, which become lignitic with depth. Composition, structure and grain size show deposition in a probably upper deltaic environment.
  • 8. BASIC RESISTIVITY THEORY Electrical resistivity is a material property which indicates how well a material retards electrical conduction. Resistivity relates electrical potential and current to the geometrical dimension of the specified region. It is the reciprocal of conductivity. Electrical conduction takes place due to the movement of charges. Charges are displaced from the original equilibrium condition under the application of electric potential. However, charge density depends on the applied electric field and resistivity of the material. Resistivity can be defined by considering current flow through a cylindrical section. To define resistivity, assuming a cylindrical section with cross sectional area and length of A and L, if current flow is I through section resistance R and potential drop across the section is V, then resistivity can be expressed by the following equation ρ=RA/L……………………………..(1) where, ρ=Electrical Resistivity, R= Resistance of the material, V= Potential, I= Current , A= Cross sectional Area and L= Length. The schematics of cylindrical section and flow of current are presented Figure1 : Diagram showing the flow of current through a cylindrical section
  • 9. To obtain a good 2-D picture of the subsurface, the coverage of the measurements must be 2-D as well. The basic resistivity measuring technique is just similar to the conventional principles. Basically, four electrodes are required; two for current injection and two electrodes for potential measurement. Each array has their own advantages and drawbacks in data acquisition and processing works. But one might has better sensitivity and resolution power for vertical as well as lateral structural variations than the other. For instance, Wenner array in multi-electrode mode has good resolution power for horizontal structure having vertical variations but weak for horizontally variable geological structures. Figure 2: Arrangement of electrodes for a 2D survey
  • 10. METHODOLOGY In this research work, the Wenner array in electrical resistivity survey was adopted. The basic field equipment for this study is the PASI Earth resistivity meter which displays apparent resistivity values digitally as computed from ohm’s law. It is powered by a 12.5 V DC power source. Other accessories to the Earth Resistivity meter includes the booster, four metal electrodes, cables for current and potential electrodes, harmers (3), measuring tapes, walking, phones for very long spread. In this configuration, the four electrodes are positioned symmetrically along a straight line, the current electrodes on the outside and the potential electrodes on the inside. The spacing between adjacent electrodes is “a”. With Wenner array, the first step is to make all the possible measurement with electrode spacing of “1a”. Electrode 1 is used as the first current electrode C1, electrode 2 as the first potential electrode P1, electrode 3 as the second potential electrode P2 and electrode 4 as the second current electrode C2. For the second measurement, electrodes 2, 3, 4 and 5 are used for C1, P1, P2, and C2 respectively. This is repeated down the line of electrodes until electrodes 17, 18, 19 and 20 are used for the last measurements with “1a” spacing. The spacing is then doubled without moving on, the first active electrodes with “2a” electrode spacing being 1, 3, 5 and 7. For the second measurement, electrodes 2, 4, 6 and 8 are used. This process is repeated down the line until electrodes 14, 16, 18 and 20 are used for the last measurement with spacing “2a”. The same process is repeated for measurements with “3a”, “4a”, “5a” and “6a” spacing.
  • 11. To get the best results, the measurements in a field survey should be carried out in a systematic manner so that, as far as possible, all the possible measurements are made. This will affect the quality of the interpretation model obtained from the inversion of the apparent resistivity measurements (Dahlin and Loke, 1998). As the electrode spacing increases, the number of measurements decreases. The number of measurements that can be obtained for each electrode spacing, for a given number of electrodes along the survey line, depends on the type of array used. The Wenner array gives the smallest number of possible measurements compared to the other common arrays that are used in 2-D surveys. METHODOLOGY CONT’D EQUIPMENT USED FOR THE FIELD WORK INCLUDE Measuring Tape, Electrodes (Current And Potential Electrode), Cables, Terrameter, Hammer , Battery, Cutlass, Gps (Global Positioning System
  • 12. RESULTS Figure 3: Inversion result from Location 1 Ekiugbo Community
  • 13. Figure 4 Inversion result from Location 2 Ekiugbo Community
  • 14. Figure 5: Inversion result from Location 3 Ekiugbo Community
  • 15. Figure 6: Inversion result from Location 4 Ekiugbo Community
  • 16. DISCUSSION OF RESULTS The obtained electrical resistivity images of the subsurface of the four transverses are presented as models in figures 4.1, 4.2, 4.3 and 4.4. The root mean square errors obtained in the inverted models were between a minimum of 4.6 to a maximum of 11.7% after 3 iterations for each of the transverse. The maximum depth of penetration for transverse 1 is 53.6m while that of transverse 2, 3 and 4 are 54.3m, 53.6 and 54.3 respectively. There is a very good correlation between the subsurface images of the four transverses which shows that the area of investigation has very well compacted soil with even deposition across the area. Each of the profiles indicates that resistivity increases with depth. The first 3 layers across the 4 transverse indicates the presence of alluvium deposits with scattered deposit of clay in small quantities from 0- 20m in depth underlain by laterite varying about 15m to 20m in thickness, across the four transverses with resistivity values ranging from 600ohm.m to about 1000ohm.m. The areas of intermediate resistivity zone 1000 to 3500ohm.m indicate a natural material like sandstone that have been underlain by a thin layer of shale and The High resistivity zone 3500ohm.m and above has been interpreted as bedrock which comprises of gravels and granite. From the interpretation it can be shown that the investigated area is competent for engineering purpose as revealed by the geoelectric imaging of all the transverses. It has been shown that all the areas are competent for the construction of factories that make use of heavy machines However; the area might be difficult to access aquifer because of its low conductivity. The four study areas also shows no form of contamination.
  • 17. CONCLUSION The electrical resistivity imaging has been successfully used to determine the subsurface in the study area from which it was shown that the study area has compacted soil and an underlying layer of bedrock which comprises of gravels and granite the area also shows that there are no faults which could lead to collapse that are suitable for engineering purpose. There is also no sign of contamination which means the soil is not polluted and can be used from agricultural purposes. However low conductivity of the study area reveals that it is not aquiferous and thus might not be suitable for water supply purposes.
  • 18. REFERENCES Ahzegbobor P.A 2010 Acquisition geometry and inversion of 3d geoelectrical resistivity imaging data for environmental and engineering investigations Allen, J.R.L., 1965. Late Quaternary Niger Delta and adjacent areas: sedimentary environments and lithofacies. Am. Assoc. Petroleum Geol. Bulletin, Vol. 49, pp. 547-600. Aubert, M. (1984). Resistivity and magnetic surveys in ground-water prospecting in volcanic areas. Case history Maar of Beanit, Puy de Dome, France Geophys. Prospect. 32: 63–554. Carrara, E. (2001). Resistivity and radar surverys at the archaeological site of Ercolano. J. Environ. Eng. Geophys. 6: 32–123. Short, K.L. and stauble A.J. 1967. Outline geology of Niger delta A.A. PG-V.5. I P. 761 -799. Oomkens, E., 1974. Lithofacies relations in Late Quaternary Niger delta complex: - Sedimentology. Vol. 21, pp. 195-222.