scholarly journals ELECTRICAL RESISTIVITY METHOD APPLIED TO STUDY GROUNDWATER CONTAMINATION AROUND THE ALAGOINHAS CEMETERY, BAHIA, BRAZIL

2015 ◽  
Vol 33 (3) ◽  
pp. 489
Author(s):  
Eduardo M.S. Amarante ◽  
Olivar A.L. de Lima ◽  
Susana S. Cavalcanti
Keyword(s):  
Electrical Resistivity ◽  
Cross Sections ◽  
Electrode Array ◽  
Data Interpretation ◽  
Least Square ◽  
Resistivity Method ◽  
Static Water ◽  
Least Square Fit ◽  
Subsurface Zones ◽  
Geological Constraints

ABSTRACT. To investigate the subsurface geological and hydrological conditions around the area of the Alagoinhas county cemetery – Bahia State, Brazil, 38 vertical electrical soundings using Schlumberger electrode array were performed to a maximum AB/2 spacing of 300 m. The electrical resistivity data were automatically inverted by computer, using a least square fit criterion to the error of the model with respect to the observed data and the help of public domain softwares RESIST V1.0 and RES1D. Geological constraints of lithological well logs were used to control the data interpretation, by fixing the number of layers and an initial model suggested by the interpreter. Represented as maps, sounding curves and geoelectrical cross-sections, the results allow: (i) to map the static water table depth, which in the more plain areas, are around 27m depth; (ii) to suggest that the subsurface zones of low true resistivity (<300Ω.m) are contamination plumes above the aquifer top, whose sources are related to the cemetery; and (iii) to detect electrical heterogeneities in the aquifer vadose zone, indicatives of the travel of the invading contamination.Keywords: electrical methods, resistivity, Alagoinhas, water contamination.RESUMO. Para investigar as condições geológicas e hidrológicas da subsuperfície na área do entorno do Cemitério Municipal de Alagoinhas, Bahia, foram realizadas 38 sondagens elétricas verticais centradas em pontos acessíveis da área. As sondagens foram executadas usando o arranjo Schlumberger de eletrodos, até espaçamentos máximos de eletrodos de corrente AB/2 de 300 m. Os dados de resistividade elétrica foram invertidos automaticamente em computador usando critérios de ajuste de mínimos quadrados para o erro domodelo comrespeito aos dados observados, usando os programas de domínio público RESIST V1.0 e RES1D. Informações geológicas de poços foram usadas no controle da interpretação, efetuada com o envolvimento do intérprete através da fixação do número de camadas e de um modelo inicial para a inversão. Apresentados na forma de mapas, curvas de sondagens e seções geoelétricas transversais, os resultados permitiram: (i) mapear o nível estático da água subterrânea que, nas partes mais planas da área, situa-se em torno de 27m de profundidade; (ii) indicar que as zonas subsuperficiais de baixas resistividades verdadeiras (<300 Ω.m) são plumas de contaminação na parte superior do aquífero, cuja fonte é associada ao cemitério; e (iii) detectar heterogeneidades elétricas na zona vadosa do aquífero apontando feições indicativas de rotas de invasão do contaminante.Palavras-chave: métodos elétricos, resistividade, Alagoinhas, contaminação da água.

ELECTRICAL RESISTIVITY METHOD APPLIED TO STUDY GROUNDWATER CONTAMINATION AROUND THE ALAGOINHAS CEMETERY, BAHIA, BRAZIL

2016 ◽  
Vol 33 (3) ◽  
Author(s):  
Eduardo M.S. Amarante ◽  
Olivar A.L. de Lima ◽  
Susana S. Cavalcanti
Keyword(s):  
Electrical Resistivity ◽  
Groundwater Contamination ◽  
Electrode Array ◽  
Hydrological Conditions ◽  
Vertical Electrical Soundings ◽  
Resistivity Method ◽  
Electrical Soundings ◽  
Electrical Resistivity Method

ABSTRACT. To investigate the subsurface geological and hydrological conditions around the area of the Alagoinhas county cemetery – Bahia State, Brazil, 38 vertical electrical soundings using Schlumberger electrode array were performed to a maximum AB/2 spacing... RESUMO. Para investigar as condições geológicas e hidrológicas da subsuperfície na área do entorno do Cemitério Municipal de Alagoinhas, Bahia, foram realizadas 38 sondagens elétricas verticais centradas em pontos acessíveis da área. As sondagens foram...

scholarly journals Modeling of Subsurface Integrity Using Dar-Zarrouk Parameters: A Case Study of Ikekogbe UBE Primary School, Ekpoma, Edo State, Nigeria

2019 ◽  
pp. 1-17
Author(s):  
Bawallah Musa Adesola ◽  
Ilugbo Stephen Olubusola ◽  
Aigbedion Isaac ◽  
Aina Adebayo O. ◽  
Oyedele Akindele Akintunde
Keyword(s):  
Electrical Resistivity ◽  
Primary School ◽  
Electrode Array ◽  
Electrode Spacing ◽  
Weak Zone ◽  
Current Electrode ◽  
Resistivity Method ◽  
Edo State ◽  
Structural Failures ◽  
Dar Zarrouk Parameters

In this present study area, most building failures often start with minor/major cracks which widen over time, and it is often followed by post construction remedial measures which fail after sometime, thereby leading to total collapse and sinking of such buildings. The research was carried out in order to be able to unravel the causes of major cracks along the side of a major class room block at Ikekogbe, UBE Primary School, Ekpoma, Edo State, Nigeria in less than five (5) years after it was constructed. The cracks were visible both at the front and at the back of the building along the same axis and almost at this same distance as it was at the front of the building. The investigation involved Electrical Resistivity method using three techniques; Vertical Electrical Sounding (VES), 2-D Electrical Resistivity Tomography (ERT) and Horizontal Profiling (HP). The traverses were established along E-W directions and Eight (8) VES were carried out using Schlumberger array with current electrode spacing varying from 1 to 40 m, with 2-D ERT using Dipole-Dipole electrode array with inter-station separation of 5 m and an expansion factor that varied from 1 to 5 and HP using Wenner array with an electrode spacing of 5 m interval. The VES interpretation results were used to determine the second order parameters for modeling of subsurface integrity/competence. The 2 D imaging (Dipole-Dipole) gave information on the subsurface characteristic and the Wenner profile was characterised by low resistivity at the region of 30 to 45 m considered as the weak zone. Correlating the results with subsurface integrity model along traverses one and three, there was a high degree of correlation as this region coincides with the very low/low integrity/competence with the foundation of the classroom overlying this layers. The research revealed that the problem of structural failures/crack noticed along the building walls and axis was not as a result of human problem alone but mainly the existence of very low/low integrity/competence layers which contributed greatly to the cracks observed on the classroom block. These results reveal that the three Electrical resistivity techniques used for this study are complimentary to each other.

Airblast Atomization of Viscous Newtonian Liquids Using Twin-Fluid Jet Atomizers of Various Designs

1992 ◽  
Vol 114 (1) ◽  
pp. 113-118 ◽  
Author(s):  
S. C. Tsai ◽  
B. Viers
Keyword(s):  
Cross Sections ◽  
Inverse Method ◽  
Threshold Value ◽  
Least Square ◽  
Liquid Jet ◽  
Ohnesorge Number ◽  
Dimensionless Groups ◽  
Least Square Fit ◽  
Newtonian Liquids ◽  
Generalized Inverse Method

Airblast atomization of viscous Newtonian liquids is carried out using coaxial twin-fluid jet atomizers of different nozzle sizes, slit angles, and slit cross sections for air flow. As the atomizing air swirls downstream along the liquid jet, waves form on the surface of the liquid jet. As a result, the liquid jet sheds ligaments which rapidly collapse into small drops. The atomized drop sizes can be described in terms of three dimensionless groups, namely, liquid-to-air mass ratio (M˙L/M˙A), Weber number (We), and Ohnesorge number (Z) in simple forms whose exponents and coefficients are determined by the best least square fit to the experimental results using the generalized inverse method. In addition, we found that the atomized drop sizes substantially decrease as the atomizing air pressure exceeds a threshold value which varies from less than 170 to 220 kPa depending on the nozzle size and the slit cross section.

scholarly journals Hydrogeophysical Implication of Geoelectric Sounding at Igarra Comprehensive High School, Akoko Edo Local Government, Nigeria

2021 ◽  
Vol 8 (12) ◽  
pp. 411-417
Author(s):  
Adediran Olanrewaju Adegoke ◽  
E. Rotimi Olafisoye ◽  
Oluwatoyin Ologe
Keyword(s):  
High School ◽  
Electrical Resistivity ◽  
Local Government ◽  
Electrode Array ◽  
Groundwater Potential ◽  
Comprehensive High School ◽  
Resistivity Method ◽  
Overburden Thickness ◽  
Weathered Layer ◽  
Electrical Sounding

Electrical resistivity method was used to carry out hydrogeophysical study in order to evaluate the groundwater potential of Igarra Comprehensive High School, Akoko Edo Local Government, Nigeria. The vertical electrical sounding technique (VES) was adopted for the resistivity method. A total of eighteen electrical soundings were conducted across the area using the Schlumberger electrode array with AB/2 varying from 1 to 65 m. After the data acquisition, interpretation was carried out qualitatively and quantitatively and the results were presented as sounding curves, tables, charts, maps and geoelectric sections. The generated geoelectric layers from the sounding curves revealed four geologic layers: the topsoil, the weathered layer, the partially weathered/fractured basement and the fresh basement with their resistivity values ranging from 129.1 to 956.4 -m, 6.8 to 1491.1 -m, 261.3 to 776.6 -m and 1515.6 to 2653.5 -m respectively. The overburden thickness in the study area varies from 5.5 to 23.5 m. The groundwater potential map enabled in the classification of the study area into: low, medium and high groundwater potential area. About 85% of the study area falls within the low groundwater potential rating while about 10% constitutes the medium groundwater potential rating and the remaining 5% constitutes high groundwater potential rating. Keywords: Groundwater, overburden, electrical resistivity, basement, geoelectric sounding.

scholarly journals Electrical Resistivity Tomography Application for Buried Foundation Investigations: Insights and Review

2021 ◽  
Vol 54 (2E) ◽  
pp. 122-133
Author(s):  
Raad Eissa
Keyword(s):  
Electrical Resistivity ◽  
Case Studies ◽  
Electrical Resistivity Tomography ◽  
Geophysical Methods ◽  
Data Interpretation ◽  
Traditional Methods ◽  
Resistivity Tomography ◽  
Existing Structures ◽  
Resistivity Method ◽  
Electrical Resistivity Method

Maintenance of existing structures and development or reuse of brownfield sites need to determine buried foundations, in terms of location and dimensions, as accurately as possible. Geophysical methods provide an indirect way to look in the ground and provide information about the subsurface that the traditional methods might be unable to. In particular, the electrical resistivity method has been performed in the context of buried foundation surveys. This review spots the light on the main results obtained from utilizing the electrical resistivity method and the most affecting parameters that can influence the obtained resistivity models, and also, focuses on published case studies to merge their findings to understand the interaction among the method, the foundation and the hosting background for buried foundations surveys. The case studies mentioned in this review show the resistivity method's success and highlight the most important parameters that can control the method’s applicability and data interpretation. The integration of the geophysical-traditional methods has appreciable potential for more accurate findings.

Least-square refinement of structure parameters from CBED integrated intensities: application to determination of temperature factors in Y BA2CU3O7

1992 ◽  
Vol 50 (2) ◽  
pp. 1456-1457
Author(s):  
Kjersti Gjønnes ◽  
Jon Gjønnes
Keyword(s):  
Least Square ◽  
Measured Intensity ◽  
Structure Information ◽  
Accurate Temperature ◽  
Least Square Fit ◽  
Case Application ◽  
Integrated Intensities ◽  
Temperature Factors ◽  
Narrow Bands

Electron diffraction intensities can be obtained at large scattering angles (sinθ/λ ≥ 2.0), and thus structure information can be collected in regions of reciprocal space that are not accessable with other diffraction methods. LACBED intensities in this range can be utilized for determination of accurate temperature factors or for refinement of coordinates. Such high index reflections can usually be treated kinematically or as a pertubed two-beam case. Application to Y Ba2Cu3O7 shows that a least square refinememt based on integrated intensities can determine temperature factors or coordinates.LACBED patterns taken in the (00l) systematic row show an easily recognisable pattern of narrow bands from reflections in the range 15 < l < 40 (figure 1). Integrated intensities obtained from measured intensity profiles after subtraction of inelastic background (figure 2) were used in the least square fit for determination of temperature factors and refinement of z-coordinates for the Ba- and Cu-atoms.

scholarly journals Electrical Resistivity Measurements and Soundings on Glaciers: Introductory Remarks

1967 ◽  
Vol 6 (47) ◽  
pp. 599-606 ◽  
Author(s):  
Hans Röthlisberger
Keyword(s):  
Electrical Resistivity ◽  
Resistivity Measurements ◽  
Resistivity Method

A brief description of the resistivity method is given, stressing the points which are of particular importance when working on glaciers. The literature is briefly reviewed.

scholarly journals Identifying Changes in Sediment Texture along an Ephemeral Gravel-Bed Stream Using Electrical Resistivity Tomography 2D and 3D

2021 ◽  
Vol 11 (7) ◽  
pp. 3030
Author(s):  
Marcos A. Martínez-Segura ◽  
Carmelo Conesa-García ◽  
Pedro Pérez-Cutillas ◽  
Pedro Martínez-Pagán ◽  
Marco D. Vásconez-Maza
Keyword(s):  
Electrical Resistivity ◽  
Cross Sections ◽  
Electrical Resistivity Tomography ◽  
Environmental Changes ◽  
Subsurface Layer ◽  
Sediment Texture ◽  
Borehole Data ◽  
Resistivity Tomography ◽  
Gravel Bed ◽  
Basin Scale

Differences in deposit geometry and texture with depth along ephemeral gravel-bed streams strongly reflect fluctuations in bedload which are due to environmental changes at the basin scale and to morphological channel adjustments. This study combines electrical resistivity tomography (ERT) with datasets from borehole logs to analyse the internal geometry of channel cross-sections in a gravel-bed ephemeral stream (southeast Spain). The survey was performed through longitudinal and transverse profiles in the upper channel stretch, of 14 to 30 m in length and 3 to 6 m in depth, approximately. ERT values were correlated with data on sediment texture as grain size distribution, effective grain sizes, sorting, and particle shape (Zingg’s classification). The alluvial channel-fills showed the superposition of four layers with uneven thickness and arrangement: (1) the softer rocky substrate (<1000 Ω.m); (2) a thicker intermediate layer (1000 to 2000 Ω.m); and (3) an upper set composed of coarse gravel and supported matrix, ranging above 2000 Ω.m, and a narrow subsurface layer, which is the most resistive (>5000 Ω.m), corresponding to the most recent armoured deposits (gravel and pebbles). The ERT results coupled with borehole data allowed for determining the horizontal and vertical behaviour of the materials in a 3D model, facilitating the layer identification.

Array design

1968 ◽  
Vol 58 (3) ◽  
pp. 977-991
Author(s):  
Richard A. Haubrich
Keyword(s):  
High Resolution ◽  
Data Processing ◽  
Least Square ◽  
Wave Number ◽  
Array Design ◽  
Least Square Fit ◽  
The Difference ◽  
Set Of Points ◽  
Array Output

abstract Arrays of detectors placed at discrete points are often used in problems requiring high resolution in wave number for a limited number of detectors. The resolution performance of an array depends on the positions of detectors as well as the data processing of the array output. The performance can be expressed in terms of the “spectrum window”. Spectrum windows may be designed by a general least-square fit procedure. An alternate approach is to design the array to obtain the largest uniformly spaced coarray, the set of points which includes all the difference spacings of the array. Some designs obtained from the two methods are given and compared.

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