Pole-dipole Array Research Articles

Evaluation of the possibility of searching for groundwater using electrical resistivity tomography based on the data of numerical modelling in complicated permafrost conditions (the case of the territory in the eastern part of the Republic of Buryatia)

Relevance. Groundwater is the main source of industrial and technical water supply for mining facilities. The geological structure of the studied areas can be complicated by various factors that make it difficult to search for and localize groundwater. In this regard, electrical geophysical prospecting methods are often included in the complex of prospecting and exploration works, before which it is necessary to justify the application of the chosen method for solving the problems by performing numerical modelling. Aim. To substantiate the use of electrical resistivity tomography for the search for groundwater, taking into account complicating factors, including perennially frozen rocks, taliks, and fault zone, by numerical modelling. Objects. Geological environment represented by Quaternary system rocks and permafrost rocks of Cretaceous sediments of the Zazinskaya intermontane area, fault zone, talik zones. Methods. Solution of the direct problem, solution of the inverse problem, ground geophysical surveys using electrical resistivity tomography. Results. Based on the performed numerical modelling, it is shown that the use of electrical resistivity tomography is expedient when searching for groundwater in the area characterized by various factors: permafrost, talik, and a fault zone. Based on the results of solving direct and inverse problems of electrical survey, using field works performed in 2020 in the Eravninsky district of the Republic of Buryatia as an example, it is shown that pole-dipole arrays in electric resistivity survey with electrode distance of 5 m, successfully confirmed by drilling operations, allow us reliably delineate potential zones of water inflow. These zones, characterized by low values of electrical resistivity, in this area, are related to talik zones, which are powered by heat flow from the bowels of the earth.

Study on the Placement Location of the Infinite Pole of an ERT Pole-Dipole Array

Study on the Placement Location of the Infinite Pole of an ERT Pole-Dipole Array

Characterizing mudstones and fault structure in Bumita Quarry, Perlis through integrated geophysical techniques

The parameters of seismic refraction and electrical resistivity play a crucial role in geological studies, as they provide insights into the composition of rocks or soil beneath the Earth’s surface. Previous researchers have established reference ranges for seismic velocity and resistivity values based on different rock types, which are presented in tabulated forms. However, the wide variability in these values sometimes leads to challenges in interpretation due to overlapping ranges. In the region of Perlis, Malaysia, a comprehensive geophysical investigation involving seismic refraction and electrical resistivity methods was conducted within the Chepor Member of the Kubang Pasu Formation at the Bumita Quarry and Utan Aji. The results were then correlated with porosity and permeability data. The Chepor Member primarily comprises both red mudstone and grey mudstone. Interestingly, the seismic velocities of these two mudstone types are quite similar, differing only by a small margin of approximately 200 m/s. The resistivity method employed utilized a pole-dipole array configuration. In terms of resistivity values, the red mudstone exhibited lower readings (ranging from 15 to 100 Ωm) compared to the grey mudstone (ranging from 120 to 500 Ωm). Assessing porosity, the red mudstone displayed a value of 0.95%, alongside a permeability of 5.58×10-5 μd, while the grey mudstone indicated a slightly higher porosity value of 1.9% and a permeability of 2.06×10-5 μd. Consequently, the study successfully established seismic velocity and resistivity benchmarks for the mudstones within the Chepor Member geological unit.

Three-Dimensional Resistivity and Chargeability Tomography with Expanding Gradient and Pole–Dipole Arrays in a Polymetallic Mine, China

Three-dimensional resistivity/chargeability tomography based on distributed data acquisition technology is likely to provide abundant information for mineral exploration. To realize true 3D tomography, establishing transmitter sources with different injection directions and collecting vector signals at receiver points is necessary. We implemented 3D resistivity/ chargeability tomography to search for new ore bodies in the deep and peripheral areas of Huaniushan, China. A distributed data acquisition system was used to form a vector receiver array in the survey area. First, by using the expanding gradient array composed of 11 pairs of transmitter electrodes, we quickly obtained the 3D distributions of the resistivity and chargeability of the whole area. Based on the electrical structure and geological setting, a NE-striking potential area for mineral exploration was determined. Next, a pole–dipole array was employed to depict the locations and shapes of the potential ore bodies in detail. The results showed that the inversion data for the two arrays corresponded well with the known geological setting and that the ore veins controlled by boreholes were located in the low-resistivity and high-chargeability zone. These results provided data for future mineral evaluation. Further research showed that true 3D tomography has obvious advantages over quasi-3D tomography. The expanding gradient array, characterized by a good signal strength and field efficiency, was suitable for the target determination in the early exploration stage. The pole–dipole array with high spatial resolution can be used for detailed investigations. Choosing a reasonable data acquisition scheme is helpful to improve the spatial resolution and economic efficiency.

Application of joint inversion of Wenner and pole–dipole arrays in limestone exploration

Application of joint inversion of Wenner and pole–dipole arrays in limestone exploration

Landslide investigation using Electrical Resistivity Imaging (ERI) method at Kg. Chuchoh Puteri, Kuala Krai, Kelantan, Malaysia

The possible landslide in Kg. Chuchoh Puteri, Kuala Krai, Kelantan were investigated using the electrical resistivity imaging (ERI) technique. The survey for the collecting of data was conducted along six lines. Each survey line was 200 meters long, with 5 meters between electrodes. ABEM Terrameter LS 1 is used to record all the data and RES2DINV software is used to process it. While conducting the geophysical survey, the relationship between resistivity and conductivity is reciprocal. A pole-dipole array configuration was utilised in survey Lines 1, 2, 4 and 5 and in survey Lines 3 and 6, a Schlumberger array configuration. Survey Lines 2, 3, and 6 are primarily indicated as having a high probability of experiencing a landslide using the pseudosection 2-D profile. The findings reveal varying resistivity at a depth of study between 40 and 80 meters for a survey line length of 200 meters. In general, the resistivity survey's seven pseudosections showed two distinct types of soils: dry residual soil (1–1500 Ωm) and weathered volcanic rocks (>1500 Ωm). Residual soils with varying saturation levels, hard soil and weathered volcanic rock, have dominated the soil profile. These profiles can generally be divided into two (2) zones: thin/thick layers of loose to dense residual soils (10–100 Ωm; Zone A) and thin/thick layers of dense and hard material (> 1000 Ωm).

Groundwater exploration using Electrical Resistivity Imaging (ERI) at Kemahang, Tanah Merah, Kelantan

The electrical resistivity imaging (ERI) method was conducted at Kemahang, Tanah Merah, Kelantan. This study intends to explore the potential for groundwater resources in the study area. The greatest way for locating groundwater is ERI, a technique that doesn’t alter the composition or functionality of the soil. ERI survey is concerned with the resistivity (Ωm) value of subsurface rocks. The Pole-Dipole array was used for this study, and a total of two survey lines were used. Each survey line was 200 m long, with 2.5 m between electrodes. ABEM Terrameter LS Toolbox is used to record all the data, and RES2DINV software is used to process it. All the data are processed in two-dimensional (2D) resistivity profiles will give a better understanding of the geological environment and enable the detection of groundwater. The findings indicate fluctuating resistivity with a range of 1-4000 Ωm and an inquiry depth of roughly 45 m. High resistivity zones of 4000 Ωm indicate values for granitic rock, whereas low resistivity zones of 10-800 Ωm reveal values for the area’s fractured aquifer, which is viewed as a potential water carrying zone (bedrock). Bedrock is found to be around 50 m below the indicated fractured aquifer layer, which is located at a depth of about 25 m. By measuring the depth of the fractured zone for probable zones with low resistivity values, this study provides an idea of the potential groundwater resources.

Identification of Different Shallow Foundations Using 3D Electrical Resistivity Modeling

The electrical resistivity method has been successfully used to detect shallow buried foundations, almost, by using 2D electrode arrays. Basic geometry foundations (e.g., buried walls) have been investigated, although, more complicated foundation designs (e.g., stepped footing, pile group with a pile cap) are widely used in the construction industry. Investigation of these complicated foundation types, and engaging 3D surveys, therefore, are required. Multiple 3D electrical resistivity forward modeling was used to simulate different foundations (isolated simple footing, isolated stepped footing, combined simple footings, and pile group with a pile cap). The generated data sets then inverted using a robust inversion algorithm where RES3DINVx64 was used to perform the inversion process for the 3D models. The results from the 3D inverse modeling, suggest the pole-dipole and dipole-dipole arrays for all the investigated foundations.

Exploration of a Copper Ore Deposit in Elbistan/Turkey Using 2D Inversion of the Time-Domain Induced Polarization Data by Using Unstructured Mesh

We present the results of a direct current (DC) resistivity and time-domain induced polarization (TDIP) survey exploring a copper ore deposit in Elbistan/Turkey. The ore deposit is elongated below a valley and is of disseminated form with sulfide content. DC and IP data were acquired using the pole-dipole array on eight parallel profiles crossing the valley perpendicularly. The length of each profile was 300 m with an inter-profile distance of about 50 m. The data were interpreted by a newly developed 2D DC/TDIP inversion algorithm. The finite element algorithm uses a local smoothness constrained regularization on unstructured meshes. The finite element forward solution, as well as the inverse problem, is solved by an iterative preconditioned conjugate solver. The depth of investigation (DOI) was determined from cumulative sensitivities of the 2D inversion algorithm results. Because of the dissemination of the ore, the 2D inversion of the DC data was ambiguous: However, due to the sulfide content, a strong chargeability anomaly associated with the ore body was detected. We show that chargeability anomalies can generally be detected in the absence or presence of corresponding resistivity anomalies. This highly chargeable structure was confined in lateral direction. Although the lower boundary of the structure could not be resolved by the applied field set-up, a rough estimation of it could be derived at a depth of 90 m using synthetic modeling analyses. The 2D chargeability models are consistent with existing borehole information.

Unearthing Underground Mining–Induced Strata Disturbance by Electrical Resistivity Tomography Interpretation

ABSTRACT The focus of the study was to evaluate the rock strata transformation above an underground mine panel during pre-and-post mining based on an electrical resistivity tomography (ERT) geophysical technique. The data were acquired using two electrode arrays (i.e., pole-dipole and Wenner-Schlumberger [WS]) with electrode spacing of 6 m up to 570 m in length. The resistivity data were digitally processed through RES2DINV software. The formation of fractured rock in the overburden caused by underground mining operations was clearly distinguished by resistivity anomalies observed using the pole-dipole array. Variation in the hydrogeological condition in the strata was also assessed during the pre-and-post mining conditions. The impact of compression and tension generated in the strata as a result of extraction of coal and subsidence in the overburden rock was observed through prominent resistivity variations observed in an inversion modelling of the WS true resistivity profile. The influence of surface topography in the near surface top weathered rock was also distinctly outlined by the resistivity measurements. ERT is a strong tool capable of providing valuable information regarding strata deformation caused by mining.

Assessing the suitable electrical resistivity arrays for characterization of basement aquifers using numerical modeling

Numerical modeling analysis was used to assess the suitable electrical resistivity arrays for the characterization of geological structures, including dyke, horst, graben, sub-vertical, and vertical structures. These geological structures usually make up the aquifers interested in the hydrogeological evaluation of crystalline basement terrains. Six electrode configurations, including Wenner alpha (α), Wenner beta (β), Wenner gamma (γ), Schlumberger array, dipole-dipole array, and pole-dipole array, were used to assess the geological structures for groundwater exploration. The synthetic models of the geological structures were generated using RES2DMOD code, and 5% noise was added to all the models. The generated models were inverted using the RES2DINV code. The results show that the most suitable arrays for dyke and graben structures are Wenner alpha, while Wenner beta is the most suitable for the horst structure. The Schlumberger array was the best for both sub-vertical and vertical structures. This study has demonstrated the efficacy of numerical modeling in assessing the best resistivity arrays for 2D electrical resistivity imaging for groundwater exploration prior to geophysical field investigation.

Manganese ore exploration using electrical resistivity and induced polarization methods in Central Belt, Peninsular Malaysia

ABSTRACTGeophysical survey techniques were carried out to identify the potential zones of manganese ore in Central Peninsular Malaysia. Electrical resistivity tomography and induced polarization (IP) geoelectrical methods have been used to identify the metal distribution and mineralization zones. Five geoelectrical survey profiles were deployed at the proposed site using pole–dipole array in the W–E direction with lengths of 400 m and 800 m. The results of the resistivity and IP inversion indicate the presence of well‐correlated low resistivity (≤ 200 Ωm) and high chargeability zones (≥ 10 ms) embedded in the varied weathered host rock as massive and disseminated ore bodies. The 3‐D maps generated enabled the delineation of the conductive bodies orientation and mineral of interest distribution. Results of the geochemical analysis contributed to validating the site as a potential mineralized zone with a high concentration of manganese. The study suggests further geophysical investigations in the southern segment of the research area to produce a more consistent image of the subsurface structures, and conclusively identifying the extension of mineral deposits for the purpose of ore prospecting to aid drilling operations.

Composite Geoelectrical Investigation to Delineate Groundwater Feasibility in Hard Rock Area of Raipur, Chhattisgarh, India

In hard rock terrains, groundwater movement, migration, and storage occur through subsurface fractures. To assess the fractures and associated water, the authors carried integrated geophysical investigation with Wenner, GRP, Schlumberger, and Pole-Dipole array in the Indian state. The resistivity survey was carried out using a CRM-500 resistivity meter. The analyzed results are also re-verified with the help of IPI2WIN software. Initially, lateral and surface variations of resistivity were plotted by using Wenner and gradient resistivity profiling array. Then the low resistivity points were investigated with Schlumberger and Pole-Dipole array. In interpretation, low resistive zones identified correspond to the possible fractured zones. The results allowed mapping of the weathering zone at depth 12 to 15 m, and deep fracture lies below depth 55.0 m depth. The present study validates that the integrated geophysical survey is a powerful exploration technique to scrutinize and identify water-bearing fractures in the hard rock area.

Evaluation of the 3D Topographic Effect of Homogeneous and Inhomogeneous Media on the Results of 2D Inversion of Electrical Resistivity Tomography Data

This work is devoted to the creation of numerical 3D models for studying 3D topographic effects of homogeneous and inhomogeneous media on the results of 2D inversion. To solve the direct problem, the integral equations method (IEM) was applied to simulate the electric field and calculate the values of apparent resistivity. For the numerical solution of the integral equation, a computational mesh, adapted to the terrain features, was constructed. The calculation of the apparent resistivity of the medium was implemented for a pole-dipole array. Calculations have been performed for a conducting medium with 3D local inhomogeneity and the ground surface topography. The influence of the 3D model with topography, flat ground surface, and immersed inhomogeneity on the results of 2D inversion was estimated. Influencing factors of the 3D model, such as the slope angle of the topography, the resistivity ratio of the inhomogeneity and the host medium, the average size of inhomogeneity and topography, the distance from the inhomogeneity to the measuring line for the medium with and without topography, and the distance between the electrodes of the electrical resistivity tomography (ERT) array, were studied. Based on the research results, recommendations and conclusions that can be useful when conducting geophysical studies by the ERT method are drawn.

Application of crosshole electrical resistivity tomography measurements under the influence of horizontally slotted plastic cased boreholes

ABSTRACTIn this work, we study the performance of cross‐hole electrical resistivity tomography measurements by employing different electrode array configurations in plastic polyvinyl chloride (PVC) cased and horizontally slotted observation boreholes by inserting a multi‐electrode cable directly into the borehole. Preliminary cross‐hole electrical resistivity tomography measurements in PVC cased boreholes related to an underground tunnel construction showed poor data quality. This was attributed to the borehole‐fluid effect caused by the PVC casings. An experimental study was conducted to support this hypothesis by setting up various simulations in a water tank, using different PVC casings with various slot densities, and different electrode array configurations. We conclude that the applicability of various measurement setups depends mainly on the acquisition protocol and, to a lesser extent, on the slot density of the PVC casing. Among the different array configurations considered, the pole–dipole array with the potential measuring electrodes being placed in a separate borehole to the current electrodes provide the most robust and reliable results, even for low slot density PVC casings. Besides, denser borehole slot configurations result in better data quality, though to a different extent for the examined protocols. A minimum slot density criterion of at least six slots/electrode spacing is proposed, regardless of the electrode array. The experimental findings are finally evaluated against real field measurements associated with the construction of an underground tunnel of the new Thessaloniki Metro, verifying the pole–dipole array's superior behaviour for this type of measurement configuration. Finally, for those cases where the aspect ratio (hole depth/hole separation) is limited, we propose a modified borehole‐to‐surface configuration with the current electrodes placed outside the boreholes. The overall results indicate that slotted PVC cased observation boreholes (e.g., conventional piezometers), typically constructed as part of many infrastructure monitoring projects, can be efficiently employed for electrical resistivity tomography mapping, generating a new perspective for geoelectrical prospecting. This measuring approach exhibits a significant advantage. The use of pre‐existing boreholes reduces the overall survey costs, reliability, and effort, while also providing high‐resolution subsurface images, especially in urban environments.

Uncertainty of the 2D Resistivity Survey on the Subsurface Cavities

We examined the uncertainty of the two-dimensional (2D) resistivity method using conceptual cavity models. The experimental cavity study was conducted to validate numerical model results. Spatial resolution and sensitivity to resistivity perturbations were also assessed using checkerboard tests. Conceptual models were simulated to generate synthetic resistivity data for dipole-dipole (DD), pole-dipole (PD), Wenner–Schlumberger (WS), and pole-pole (PP) arrays. The synthetically measured resistivity data were inverted to obtain the geoelectric models. The highest anomaly effect (1.46) and variance (24,400 Ω·m) in resistivity data were recovered by the DD array, whereas the PP array obtained the lowest anomaly effect (0.60) and variance (2401 Ω·m) for the shallowest target cavity set at 2.2 m depth. The anomaly effect and variance showed direct dependency on the quality of the inverted models. The DD array provided the highest model resolution that shows relatively distinct anomaly geometries. In contrast, the PD and WS arrays recovered good resolutions, but it is challenging to determine the correct anomaly geometries with them. The PP array reproduced the lowest resolution with less precise anomaly geometries. Moreover, all the tested arrays showed high sensitivity to the resistivity contrasts at shallow depth. The DD and WS arrays displayed the higher sensitivity to the resistivity perturbations compared to the PD and PP arrays. The inverted models showed a reduction in sensitivity, model resolution, and accuracy at deeper depths, creating ambiguity in resistivity model interpretations. Despite these uncertainties, our modeling specified that two-dimensional resistivity imaging is a potential technique to study subsurface cavities. We inferred that the DD array is the most appropriate for cavity surveys. The PD and WS arrays are adequate, while the PP array is the least suitable for cavity studies.

Groundwater Potential Assessment Using 2-D Resistivity Method In Kluang, Johor (Malaysia)

Sources of clean water are decreasing due to rapid usage, contaminated surface waters, pollution and dry season. The dependence on the existing water source is not enough to fulfil the increasing demand of population in Malaysia. In order to overcome the problem, groundwater source is the most suitable alternative. 2-D resistivity method was carried out in a granitic area of Kluang, Johor to delineate and locate groundwater resource. 5 survey lines were conducted by using ABEM SAS4000 terrameter and electrode selector which were connected to 41 electrodes through lund cables. Pole-dipole array was chosen in this study for deeper penetration. Collected data were processed by using RES2DINV software to produce inversion model which was then exported to Surfer8 software for visualisation and interpretation. The result shows that most of the study area consist of granite with different level of fracturing. Unconfined aquifer was found at depths of 0 to 50 m. Confined aquifers can be seen at two different zones. They exhibit same properties at three parallel lines, R1-R3 and show continuity between them. It is predicted that the aquifers flow in the southwest to northeast direction. The hard rock aquifers are highly recommended to be drilled as they contain a large amount of fresh water for further usage.

Slope Failure Investigation in Weathered Granitic Rock Mass Using Electrical Resistivity Imaging: Case Study in Kg Bukit Selar, Jeli, Kelantan, Malaysia

The slope failure phenomenon is a common natural hazard in Malaysia in which due to the change in slope angle, weathering, heavy rainfall, and overloading. This research is focusing on analyzing the subsurface condition of slope failure in Kg Bukit Selar, Jeli, Kelantan by the electrical resistivity imaging (ERI) method. Geologically, the study area mainly composed of granitic rocks (microgranite and porphyritic granite). A total of five resistivity survey lines using Schlumberger and Pole-Dipole array with a 200m spread was conducted at the failed slope. ABEM Terrameter LS was used to collect field data, and processed by using RES2DINV software. The results were presented in the form of two-dimensional (2D) resistivity profiles providing a view of the subsurface distribution of the granitic rock, geological structures, and water content. The results show that the slope failed due to the presence of groundwater. The findings in this study show that the resistivity survey is a reliable method for slope failure investigation. The slope failures due to seepage problems were successfully being investigated using the ERI method.

LANDSLIDE HAZARD IDENTIFICATION (LHI) BASED ON GEOELECTRICAL MAPPING ANALYSIS (GEM): CASE STUDY FROM LUYANG, KOTA KINABALU, SABAH, MALAYSIA

Landslides are amongst the most damaging natural hazards in Malaysia. The study of landslides has drawn nationwide attention mainly due to increasing awareness of the socio-economic impact of landslides, as well as the increasing pressure of urbanization. Landslide Hazard Identification (LHI) is part of the process used to evaluate if any particular situation, item, thing, etc. may have the potential to cause harm. The description of LHI should include the location, volume (or area), classification and velocity of the potential landslides and any resultant detached material, and the probability of their occurrence within a given period of time. In this paper, we present the results of the measurement for the subsurface resistivity within by using the pole-dipole electrode array and present the 2D view of each resistivity profile. The result presented successfully detect the dominant layer consists of interbedded sandstone and shale of the Crocker Formation with highly weathered. This both layers have high porosity and potential to contain high water content which can trigger landslide to occur. Besides that, there are several boulders zone (weathered to fresh rock) that can be found at the top of the subsurface profile at about 1.5m to 15m in depth. The bedrock layer was estimated to be found at 4m to 32.5m in depth from the original ground and one possible fault line that had been identified. This fault line believed plays a role in the occurrence of landslide in which rock materials have lower strength compared to surrounding rocks. High density of fault means lower stability. Therefore the faut line have been regarded as a critical factor in triggering landslide in the study area. The results of these study findings are expected to be used as uniform guidelines and principles are very useful and have integrity in providing coordination of standards or policies for each planning activities for new development in the future. As a result of the lack of concern for the developer of the concept of Sustainable Development Goals (SDG) or balancing and control of environmental health, the results of this study can also be used as a yardstick to party developers who intend to develop a high ground and hillside in deciding whether to continuing development planning or not.

Geophysical investigation of a weathered terrain for groundwater exploitation: a case study from Huidong County, China

2D electrical resistivity tomography (ERT) coupled with electrical resistivity profiling, induced polarisation, and self-potential (ER-IP-SP) measurements and pumping-test data has been used to acquire subsurface electrical properties for the assessment of groundwater reserves in weathered terrains of Huidong County, China. In this investigation, ERT was performed using a pole-dipole array with 305 measurements, and ER-IP-SP with 127 stations, both along three profiles. A least-squares inversion technique is used for the post processing of the ERT data to generate 2D models of the subsurface geologic units. The following deductions are made based on the 2D ERT modelling. The average depth of fresh basement is generally 10–30 m. Three distinct layers were interpreted, i.e. 5–10 m thick topsoil cover with resistivity <1800 Ωm (above the water table), 5–25 m thick weathered layer with resistivity <900 Ωm (below the water table), and fresh bedrock with resistivity >900 Ωm (below the water table). These layers comprise the 50 m thick overburden revealed by the inverted sections. The ERT models were incorporated with ER-IP-SP to delineate various discontinuities. Groundwater resources enclosed in the weathered/fractured zones were estimated by hydraulic conductivity (K) and transmissivity (T) into three different aquifer zones with specific ranges of T and K (i.e. high, medium, and low yield aquifer). The results suggest that the best potential groundwater resources are contained within fractures/discontinuous zones. The results are well in line with the hydrogeological information available for the investigated area. This geophysical approach is useful to assess the groundwater potential where the weathering has hydrogeological significance.