APPLICATIONS OF ELECTRICAL RESISTIVITY METHOD

Geophysical Investigation was carried out along Ugbogbo road, Secretariat area in Igarra, Edo State Nigeria. In this area, the self potential method, electrical resistivity method of both the horizontal profiling technique and the vertical electrical sounding were adopted to determine possible causes of road failures which are basically geological, and recommend solutions to this problem.
A total number of 10 Vertical Electrical Soundings were carried out. The geo-electric interpretation and the inverted 2-D resistivity structures of the wenner-schlumberger technique revealed three subsurface layers: the topsoil, weathered layer and the presumed fresh bedrock. The topsoil resistivity ranges from 32 to 936 ohm-m and with an average thickness of 2.2 m. The topsoil is underlained by the fractured layer of apparent resistivity of 11.3 to 67 ohm-m and average thickness of 20 m. Along the transverse, some part of  the topsoil (10 m,115 m)  especially at the area where the stream was flowing underneath across the road (at 190 m) are suspected to be either clayey sand or water saturated. This study reveals that transverse is not really fit for road construction and some excavation and filling should be done before road construction.

Ras El Hekma area represents one of the main headlands along the southern Mediterranean coast, this study is focused on Fuka Area on the Northwestern coast of Egypt.
The purpose of this study is the determination of the subsurface layer’s distribution, exploration of water-bearing layers and determination of their thickness and depth, as well as delineation of saltwater intrusion in Fuka coastal aquifer, which represents the main environmental problem in the coastal areas.
The study area has three aquifers: Holocene, Pleistocene, and Middle Miocene aquifers. The present study clarifies the depth to fresh water which is recommended to be drilled and also reveals the saline water depth to be avoided. This delineation was by using Geoelectric method to make true resistivity, true depth and true thickness maps and interpret them with considerations of the Hydrogeology and Geology of the area that was previously studied.

This research has examined the numerical modeling of electrical resistivity data using Lagrangian interpolation. The Lagrangian generated a polynomial of minimum degree that represents/mimic the original trend of the data. The reason behind the formulated lagrangian is to reduces the stress of interpretation and improve the smoothness of the field curve. The art of the modeling involves a range [a,b] R when R is the range covering the entire data. The numerical concept is applied to reflect the real trend of the data collected. The Lagrangian interpolation skill was carried out using the MATlab program, and the curves generated showed a good fit that represent the entire trend in the range [a,b]. In respect of this, three VES locations were used as test, to confirm the efficacy of the Lagrangian. All the locations showed that the Lagrangian is efficient with the error values maintained at 2.5%,5.6% and 6.6% compared with the conventional error maintained at 2.5%, 6.4% and 5.8%. The research however concluded that the lagrangian of minimum degree are intelligent to guest the trend of the whole data when considered as a whole at values [a,b] of the generated polynomial.

Collapse dolines are closed karst depressions of various size and morphology, which can be found all over the Slovenian karst. A collapse of cave chamber roofs is the basic mechanism of their formation. Limited dimensions of cave chambers result only in the formation of small collapse dolines. The formation and allocation of collapse dolines of greater dimensions are closely related to specific underground hydrology in areas with concentrated underground water flow, water table oscillation and higher corrosion or erosion in cave passages. The analysis of collapse dolines morphology and the interpretation of processes lead to the understanding of dynamics and mechanisms of collapse dolines formation and transformation with various geomorphic processes. The dissertation introduces the new models of processes in collapse dolines, which can be used for the interpretation of collapse dolines development in time context or for interpretation of mechanics and dynamics of specific geomorphologic processes.

The resistivity survey was carried out by using vertical electrical sounding (VES) and 2D imaging techniques in the northern Badra area, Eastern Iraq. Eleven VES points distributed on two parallel profiles and six 2D imaging stations were applied using long survey lines. In general, two types of aquifers are recognized in the study area. The first is the Quaternary aquifer, which appears in all geological sections and inverse model of 2D imaging stations (2DS).This aquifer can be divided into upper and lower aquifers as shown in (2DS1), (2DS3), and (2DS4). Generally, the thickness of this aquifer ranges between (30-200 m) which occurs at a depth of (10-30m) according to geological sections, while its thickness ranges between (35-180m) and occurs at depth (10-45m) according to the inverse model of 2D imaging stations. The second is the AL-Mukdadiya aquifer, which appears only in 2DS1 at a depth of (140m), and it thickness is more than (80m). The comparison between VES and 2D imaging techniques revealed that the VES technique is the best in delineating the boundaries between layers. However, the 2D imaging technique is better at delineating the aquifers, and at determining the vertical and horizontal changes in resistivity within layers and aquifers, and it also succeeded in recognizing the upper and lower aquifers of quaternary aquifer as shown in (2DS1), (2DS3), and (2DS4). Therefore, 2D imaging is better at recognizing more layers or aquifers than that of VES technique, especially with the gradual decrease (or increase) in resistivity values or layers with small thickness. Also, the VES technique showed a high depth of investigation (DOI) in comparison with 2D imaging technique.

The  phenomenon  of  building  collapse  in recent  times  has  become  a  source  of  national concern. Particularly alarming is the situation in Lagos,  the  commercial  nerve  center  of  Nigeria.
Several  attempts  made  to  proffer  solution  to this  excluded  geophysical  investigations,  as general  opinion  did  not  support  subsurface geology as being responsible. However, 2-D and
3-D  electrical  resistivity  surveys  were  carried out    using    wenner    electrode    configuration with  64  electrodes  connected  to  a  multi-core cable,  along  three  (3)  profiles  of  260  m  length at  an  inter-electrode  spacing  of  4m.  Resistivity
measurements were    taken    alongside    with Induced  Polarization  measurements  using  the same  electrode  configuration.  The  survey  was conducted  round  to  cover  all  the  areas  where distress in building structures is noticeable. The
2-D and 3-D electrical resistivity and IP images for  the  three  profiles  revealed  that  the  main cause  of  structural  defect  in  buildings  around the  area  is  the  subsurface  geology,  contrary  to general opinion which favours insufficiency and/or lack of genuine building materials. From the results,  it  is  quite  obvious  that  the  entire  land mass of the study area is underlain by materials of  very  low  resistivity  values  below  30  Ωm  at
the  near-surface  depth  of  5  m  down  to  above 30  m.  Local  high  resistivity  in  the  near  surface material  is  due  to  either  the  effect  of  sand-filling  for  road  network  and/or  the  presence  of exotic  highly  resistive  concrete  materials  used
to reclaim land. The IP inversion models help to delineate  clay  formation  from  sandy  formation filled  with  saline  water.  The  high  IP  signals  in the  subsurface  mainly  confirm  the  presence  of clayey formation.

This paper deals with the resistivity continuous surveys on extensive area carried out at the Mont'e Prama archaeological site, in Sardinia (Italy). From 2013 to 2015, new research was performed using both non-destructive surveys and traditional archaeological excavations. The measurements were done in order to find geophysical anomalies related to unseen buried archaeological remains and to define the spatial extension of the ancient necropolis. The electrical resistivity of soils was measured by means of the Automated Resistivity Profiling (ARP©) system. This multi-pole method provided high-resolution maps of electrical resistivity in the whole investigated area using a computer-assisted acquisition tool, towed by a small vehicle. Through this acquisition layout, a surface of 22,800 m 2 was covered. The electrical resistivity data were derived in real time with centimetric horizontal precision through a differential GPS positioning system. Thanks to the simultaneous acquisition of ARP and GPS data, the rigorous georeferencing of the tridimensional experimental dataset was made possible, as well as the reconstruction of a detailed Digital Terrain Model. Here, the experimental results are analyzed and critically discussed by means of the integration of the results obtained by a high-resolution prospection performed with a multi-channel Ground Penetrating Radar system and taking into account other information derived from previous geological and archaeological studies. Geophysical results, jointly with topographic reconstruction, clearly permitted the identification of more interesting areas where future archaeological investigations could be focused.

We describe the construction and testing of a simple and efficient low-cost resistivimeter designed for use in practical classes in Applied Geophysics. The equipment was successfully tested in a vertical electrical sounding (VES) performed on sandy terrain within the campus of the Universidade Federal de Sergipe, Brazil. The VES results were in good agreement with the profiles obtained from two boreholes located approximately 500 m from the test area, clearly demonstrating the efficiency of the equipment and the adopted methodology.

This paper deals with the resistivity continuous surveys on extensive area carried out at the Mont’e Prama archaeological site, in Sardinia (Italy). From 2013 to 2015, new research was performed using both non-destructive surveys and traditional archaeological excavations. The measurements were done in order to find geophysical anomalies related to unseen buried archaeological remains and to define the spatial extension of the ancient necropolis. The electrical resistivity of soils was measured by means of the Automated Resistivity Profiling (ARP©) system. This multi-pole method provided high-resolution maps of electrical resistivity in the whole investigated area using a computer-assisted acquisition tool, towed by a small vehicle. Through this acquisition layout, a surface of 22,800 m2 was covered. The electrical resistivity data were derived in real time with centimetric horizontal precision through a differential GPS positioning system. Thanks to the simultaneous acquisition of ...

Hydrostratigraphy and hydrogeology of the Maira vicinity is important for the characterization of aquifer system and developing numerical groundwater flow models to predict the future availability of the water resource. Conventionally, the aquifer parameters are obtained by the analysis of pumping tests data which provide limited spatial information and turn out to be costly and time consuming. Vertical electrical soundings and pump testing of boreholes were conducted to delineate the aquifer system at the western part of the Maira area, Khyber Pakhtun Khwa, Pakistan. Aquifer lithology in the eastern part of the study area is dominated by coarse sand and gravel whereas the western part is characterized by fine sand. An attempt has been made to estimate the hydraulic conductivity of the aquifer system by establishing a relationship between the pumping test results and vertical electrical soundings by using regression technique. The relationship is applied to the area along the resistivity profiles where boreholes are not drilled. Our findings show a good match between pumped hydraulic conductivity and estimated hydraulic conductivity. In case of sparse borehole data, regression technique is useful in estimating hydraulic properties for aquifers with varying lithology.

This paper deals with the resistivity continuous surveys on extensive area carried out at the Mont’e Prama archaeological site, in Sardinia (Italy). From 2013 to 2015, new research was performed using both non-destructive surveys and traditional archaeological excavations. The measurements were done in order to find geophysical anomalies related to unseen buried archaeological remains and to define the spatial extension of the ancient necropolis. The electrical resistivity of soils was measured by means of the Automated Resistivity Profiling (ARP©) system. This multi-pole method provided high-resolution maps of electrical resistivity in the whole investigated area using a computer-assisted acquisition tool, towed by a small vehicle. Through this acquisition layout, a surface of 22,800 m2 was covered. The electrical resistivity data were derived in real time with centimetric horizontal precision through a differential GPS positioning system. Thanks to the simultaneous acquisition of ...

The resistivity survey was carried out by using vertical electrical sounding (VES) and 2D imaging techniques in the northern Badra area, Eastern Iraq. Eleven VES points distributed on two parallel profiles and six 2D imaging stations were applied using long survey lines. In general, two types of aquifers are recognized in the study area. The first is the Quaternary aquifer, which appears in all geological sections and inverse model of 2D imaging stations (2DS).This aquifer can be divided into upper and lower aquifers as shown in (2DS1), (2DS3), and (2DS4). Generally, the thickness of this aquifer ranges between (30-200 m) which occurs at a depth of (10-30m) according to geological sections, while its thickness ranges between (35-180m) and occurs at depth (10-45m) according to the inverse model of 2D imaging stations. The second is the AL-Mukdadiya aquifer, which appears only in 2DS1 at a depth of (140m), and it thickness is more than (80m). The comparison between VES and 2D imaging ...

An electrical resistivity tomography supported with Vertical Electrical sounding (VEs) survey was carried out within the precincts of a Faculty building at Olabisi Onabanjo University Main campus, Ago-Iwoye, Nigeria. The building is intensively affected
by dangerous cracks that cause structural instability  a  few  years  after  its  construction.  The  survey aimed to image the shallow subsurface structures and determine the possible cause of the structural instability.  2D  Resistivity  imaging  using  Wenner
array with smallest electrode spacing of 10m and VES  using  schlumberger  electrode  configuration were  carried  out  along  four  traverses  extending about  130  meters  at  the  precinct  of  the  building complex.  The  acquired  data  were  processed  and
interpreted  spatially  to  expose  the  shallow  structural  setting  of  the  site.  Integrated  interpretation led  to  the  delineation  of  hazard  zone  in  the  area. This zone is interpreted as fault with vertical and sub-vertical linear features having moved both vertically  and  horizontally  with  associated  resistivity values as low as 5Ωm. This feature is suggested as the main reason of the rock instability that resulted in potentially dangerous cracking of the buildings. Inferred lithologic units which include silty/clayey
soil, sandy clay and the basement were mapped out at  the  site.  compacted  lateritic  (hardpan)  topsoil along traverse 4 (backside of the building), though not  a  rock  unit,  constitutes  an  important  factor to  the  re-construction  of  geologic  unit  from  ERT model. The possible cause of failure of the building was  proposed  to  result  from  the  underlying  fault on which the whole weight of the building rests. It was also discovered that the pre-construction geo-technical  investigations  possibly  failed  to  capture the zones because they are point investigations that lack continuous imaging of subsurface condition. Key  words:  2-D  electrical  resistivity  tomography, structural  instability,  Fault  zone,  synclinal  features, compressible soil and springs.

The strength and stability conditions of unconsolidated geo-materials, for example soils, are influenced by modifications of their micro-structure, texture, mineralogy and effective stress levels. These modifications in the internal structures of the soils often result in geohazards (e.g., landslides, liquefaction, debris flow), which often claim so many lives, destroy the environment, and cause considerable amounts of property damage. Characterization and monitoring of such geohazards demand knowledge about the geotechnical (physical and mechanical) properties of unconsolidated near-surface geo-materials of interest. The fundamental relations between geo-electrical parameters and the geotechnical properties that influence the mechanical behavior of soils are investigated by performing controlled laboratory experiments on sand-clay mixtures under stress. Spectral electrical response (SER) measurements are performed on these mixtures over a range of frequencies [Formula: see text] wi...

Abstract Reservoirs represent a specific environmental component in many parts of the Earth, especially where water supply is limited. As is the case of the Moldavian hilly area, due to its dryness, the inhabitants created an extensive network of reservoirs since the medieval period, in the proximity of the settlement network. Over time, many dams were abandoned, while others have been relocated with impressive dynamics at a historical scale. In this paper, by analyzing old maps, LiDAR high-res DEMs, ERT surveys, and sediments, we have reconstructed the reservoir network's expansion in the last century at a regional scale and investigated the main geomorphologic characteristics of dams and associated landforms. In Jijia catchment (3386 km2) we found a total number of 1351 dams, of which 832 abandoned. 495 reservoirs were recognized on different topo maps dating from the 20th century, while 337 have been identified on DEMs. Two reservoirs were investigated in detail by field surveys, ERT surveys, profile digging, sediment analysis, and micro-sedimentological study, confirming lacustrine deposits according to the topographic reconstructions based on high-resolution LiDAR DEMs. These sedimentary lacustrine archives can substantially contribute to detailed paleoclimatic, paleohydrologic, and paleovegetation reconstruction in the study area.

Reservoirs represent a specific environmental component in many parts of the Earth, especially where water supply is limited. As is the case of the Moldavian hilly area , due to its dryness, the inhabitants created an extensive network of reservoirs since the mediev al period , in the proximity of the settlement network. Over time , many dams were abandoned, while others have been re located with impressive dynamics at a historical scale. In this paper, by analyzing old maps, LiDAR high-res DEMs, ERT surveys , and se diments, we have reconstructed the reservoir network 's expansion in the last century at a regional scale and investigated the main geomorphologic characteristics of dams and associated landform s. In Jijia catchment (3 38 6 km 2) we found a total number of 13 51 dams , of which 832 abandoned. 495 re servoirs were recognized on different topo maps dating from the 20 th century , while 337 have been identified on DEMs. Two reservoirs were investigated in detail by fi...

The strength and stability conditions of unconsolidated geo-materials, for example soils, are influenced by modifications of their micro-structure, texture, mineralogy and effective stress levels. These modifications in the internal structures of the soils often result in geohazards (e.g., landslides, liquefaction, debris flow), which often claim so many lives, destroy the environment, and cause considerable amounts of property damage. Characterization and monitoring of such geohazards demand knowledge about the geotechnical (physical and mechanical) properties of unconsolidated near-surface geo-materials of interest. The fundamental relations between geo-electrical parameters and the geotechnical properties that influence the mechanical behavior of soils are investigated by performing controlled laboratory experiments on sand-clay mixtures under stress. Spectral electrical response (SER) measurements are performed on these mixtures over a range of frequencies (0.001 Hz–1 kHz) with concurrent measurements of their geotechnical properties. Electrical parameters, such as phase, resistivity amplitude, capacitance, and loss tangent, are extracted from the SER measurements, and geotechnical properties of the mixtures, which include void ratio, dry density, and the modulus of elasticity, are obtained from laboratory measurements. Cross-plots of geotechnical properties and geo-electrical parameters indicate significant correlations. The phase and capacitance values decrease with an increase in the dry density, whilst the loss tangent and the resistivity values increase with increase in dry density. The phase and capacitance values, however, decrease with an increase in the values of the modulus of elasticity, whereas the loss tangent and the resistivity values increase with increase in elastic modulus. These relations can be useful in non-invasive prediction of the physical, mechanical, and geotechnical properties of unconsolidated geo-materials relevant in the assessment, monitoring, and mitigation of geohazards.

Electrical resistivity tomography is a geophysical method that was used to characterize the soil in Ahamdu Bello University Phase II, Zaria. Ahmadu Bello University site II lies between longitudes 7° 37.98' E and 7° 39.07' E and latitudes 11° 7.86' N and 11° 8.50' N. A multi-electrode resistivity meter (ABEM Terrameter SAS 4000) was used for data acquisition on the field using a dipole-dipole array and the data were processed and interpreted using RES2DINV. The results obtained from the resistivity tomograms of the three profiles were used to correlate with the borehole data and the correlation indicates four distinct layers (Topsoil, weathered basement, fractured and fresh basement). The most competent layer for building a foundation in the study area is the fresh basement which is about 15.9m deep from the earth surface. In this study, electrical resistivity tomography has been successfully used to determine the depth to basement and the extent to which the bedrock was delineated. Weak zones that may be prone to subsidence and the competent areas that can support massive engineering were identified.

Electrical Resistivity Imaging (ERI) is a widely used tool in geophysical surveys for investigation of various subsurface structures. In this study an ERI was conducted in collapse doline floors located in Divača karst, Slovenia. This group of collapse dolines in hinterland of River Reka ponors have floors inundated and flattened with loamy sediment. Collapse doline development and transformation processes are discussed, and various characteristics and potential formation mechanisms of flat
and loamy doline floors are considered. The loamy fills might reflect sedimentation of suspended material from floodwaters that inundated the lower parts of the collapse dolines, or could have originated in now-demolished cave passages on the slopes that were filled with finer material.

ABSTRACT Geodynamic activity in the area of West Bohemia is typified by the occurrence of earthquake swarms, Quaternary volcanism and high flux of mantle-derived CO2. The highest swarm activity occurs beneath the eastern edge of the Cheb basin, which is delineated by the NW-SE trending morphologically pronounced Mariánské Lázně Fault (MLF) controlling the formation of the basin. The previous trenching survey across the MLF zone has identified several fault strands with possible Quaternary activity. In this paper we present the results of the geophysical survey focused to trace the faults signatures in geophysical sections and to build an image of near surface tectonics. The method of electric resistivity tomography (ERT) along two profiles parallel to the trench identified a strong resistivity contrast between the bodies of sandy gravels in the middle and conductive clayey sands to the west and weathered crystalline basement to the east. The 2-D ground penetration radar (GPR) sections show direct correlation of reflections with lithological boundaries identified in the trench. As expected, the GPR signal amplitudes increase with the resistivities found in the ERT sections. Two of the four faults identified in the trench are indicated in the resistivity and GPR sections. A 3-D GPR measurement has identified a spot of high amplitudes elongated parallel to the MLF trend, which coincides with the high resistivity body. To improve the signal-to-noise ratio of the time slices we stacked the GPR time slices within vertically homogeneous blocks. This provided a contrast image of the sand-gravel body including its boundaries in three dimensions. The detailed analysis of the 3-D GPR cube revealed additional fault that limits the highly reflective sands and appears to be offset by another younger fault. Our results suggest a complex fault pattern in the studied area, which deserves a further study.

Several types of contact karst are found within the Slovenian karst, but the most common is the ponor type, which usually develops at boundaries between flysch and limestone. The most extensive contact of this type is in the area of Matarsko podolje in western Slovenia and in its northern extension, Vrhpoljska brda. In this contact karst area two types of alluvial fans appear on carbonate bedrock. Members of the first type are ordinary alluvial fans with active alluvial processes where flysch derived sediment covered limestone surface in a distinct fan shape. The other type, described as relict alluvial fans, is fan-shaped features preserved in the carbonate bedrock. These essentially bedrock landforms developed as a result of the gradual removal of pre-existing alluvial fan cover and the concurrent but non-uniform chemical denudation of the underlying carbonate bedrock. Geomorphologic and morphometric description of alluvial fans and relict alluvial are provided in the article and mechanisms of relict alluvial fans formation are discussed.