Soil Resistivity Research Articles

Optimizing Current Injection Technique for Enhancing Resistivity Method

Geo-electrical resistivity methods are widely used in various fields and have significant applications in scientific and practical research. Despite the widespread use of resistivity methods, current injection is a critical step in the process of resistivity methods, and the quality of current injection significantly impacts the accuracy of the resistivity measurements. One primary challenge is optimizing current injection techniques to enhance resistivity methods. The developed current injector model for the resistivity meter instrument enhances performance by increasing the voltage source to 400 Volts, extending measurement coverage. It provides three injection current options, 0.5A, 0.8A, and 1A, for efficient accumulator use, considering electrode distances and estimating earth resistance using Contact Resistance Measurement (CRM) to estimate the earth resistance. CRM mode ensures proper electrode connection before injection, thus improving measurement efficiency. The embedded TTGO LoRa ESP32 SX1276 facilitates wireless communication over 1.5 km, addressing challenges in remote and internet-limited areas. The model demonstrates reliability, validity, and durability in CRM mode and current injection measurement. Regarding reliability, we determine the relative error of the model by carrying out measurements repeatedly. In lab-scale testing, the average Relative Error in CRM mode is 0.65%, and in earth resistance measurement testing, it is 1.58%. These relative errors are below the 2% maximum error applied in the “Supersting”, a commercial resistivity instrument. The model's validity is defined by comparing the model with the measuring instrument; we have absolute error. In lab scale testing, the average Absolute Error in CRM mode is 3.08%, and in earth resistance measurement testing, it is 3.73%. The model's durability is tested by injecting current for a minute. After one minute of current injection, the power resistor component's temperature is stable at 30°C.

Optimizing Current Injection Technique for Enhancing Resistivity Method

Geo-electrical resistivity methods are widely used in various fields and have significant applications in scientific and practical research. Despite the widespread use of resistivity methods, current injection is a critical step in the process of resistivity methods, and the quality of current injection significantly impacts the accuracy of the resistivity measurements. One primary challenge is optimizing current injection techniques to enhance resistivity methods. The developed current injector model for the resistivity meter instrument enhances performance by increasing the voltage source to 400 Volts, extending measurement coverage. It provides three injection current options, 0.5A, 0.8A, and 1A, for efficient accumulator use, considering electrode distances and estimating earth resistance using Contact Resistance Measurement (CRM) to estimate the earth resistance. CRM mode ensures proper electrode connection before injection, thus improving measurement efficiency. The embedded TTGO LoRa ESP32 SX1276 facilitates wireless communication over 1.5 km, addressing challenges in remote and internet-limited areas. The model demonstrates reliability, validity, and durability in CRM mode and current injection measurement. Regarding reliability, we determine the relative error of the model by carrying out measurements repeatedly. In lab-scale testing, the average Relative Error in CRM mode is 0.65%, and in earth resistance measurement testing, it is 1.58%. These relative errors are below the 2% maximum error applied in the “Supersting”, a commercial resistivity instrument. The model's validity is defined by comparing the model with the measuring instrument; we have absolute error. In lab scale testing, the average Absolute Error in CRM mode is 3.08%, and in earth resistance measurement testing, it is 3.73%. The model's durability is tested by injecting current for a minute. After one minute of current injection, the power resistor component's temperature is stable at 30°C.

Heavy Metal Characteristics of Soil and Leachate Resistivity Mapping of Malacca Landfill

Heavy Metal Characteristics of Soil and Leachate Resistivity Mapping of Malacca Landfill

Electroosmotic reinforcement mechanism and laboratory tests of pulsating direct current with a high energy efficiency ratio

Based on the electroosmotic reinforcement mechanism of pulsating direct current (PDC) with a high energy efficiency ratio, the calculation method of PDC electroosmosis drainage rate was verified under different potential gradients using two forms of voltage loading, i.e., constant direct current (CDC) and PDC. The drainage weight and electric current were achieved by laboratory tests, and then the energy efficiency ratio, soil resistivity and contact resistance was calculated. The energy consumption of each test group was analyzed by considering the initial potential gradient. The obtained results show that under the same potential gradient, the difference in soil resistivity and electroosmotic drainage between PDC and CDC is not significant, but there is a significant difference in contact resistance, which leads to low current intensity and high energy efficiency ratio in the PDC test group. The expression of the electroosmotic drainage rate of the PDC is described with the coefficient μ, and then the energy efficiency ratio versus potential gradient curve is calculated, which is in good agreement with the experimental results. The reason for the lower energy consumption of PDC electroosmosis compared to CDC is described in terms of the drainage mechanism of electroosmosis.

Overvoltages caused by direct lightning strokes to a hybrid overhead line

This paper presents an analysis of the overvoltages caused by direct lightning strokes to a hybrid overhead line with 138 kV, 13.8 kV, and 220 V circuits. The primary focus is on medium voltage line overvoltages and their dependence on key parameters, including ground impedance, soil resistivity, stroke current front time, conductor characteristics, lightning channel impedance, insulator capacitance, conductors' sags, and tower surge impedance. Using specific models for the transmission tower and high-voltage insulators, validated through laboratory tests and EMTP simulations, critical currents are determined for varying soil resistivity and impulse impedances. The analysis confirms the line robust performance against stroke-induced backflashovers.

Impulse Characteristics of Soil Treated with Enhancement Materials and Various Moisture Contents

Due to the high mineral contents of additives and enhancement materials (EMs), EMs have become popular in treating soil, which expectedly improves the electrical characteristics of soil. Much of the published work on the effectiveness of EMs is based on investigations at low magnitudes of voltage, current and frequency; however, the study of these EMs under high-impulse conditions has not been widely addressed. In this work, the experimental results of a small-mesh ground electrode without EMs and treated with EMs, where the latter was poured with a controlled amount of water, are presented. The impulse impedance was expected to change appreciably due to the ionic conduction in soil and the use of EMs with a high water content; however, the impulse impedance was found to be weak and dependent on the water content, and the inductive effect was found to be significant at the voltage and current decay times. This indicates that, even though EMs and highly wetted soil can reduce the soil resistivity and relative resistance value, special attention has to be given to the impulse characteristics of the ground electrodes, particularly at tail/decay times.

Analysis of external corrosion protection performance on buried gas pipeline using CIPS and DCVG methods

The present work investigates the effectiveness of external corrosion protection using Close Interval Potential Survey (CIPS) and Direct Current Voltage Gradient (DCVG) on a buried gas pipeline. These surveys were performed on 12” gas pipeline in East Kalimantan. Coating and cathodic protection were the primary corrosion protection on these pipelines. Soil resistivity measurement was conducted every km along the pipeline to obtain the resistivity profile combined with the pH profile. CIPS showed that the Cathodic Protection system protects 79.21 % of the pipeline area. There is no sign of telluric or stray current effect from the result of CIPS. DCVG showed 159 defects that can be divided into three different clusters. There is 6-point coating defects that should be repaired immediately due to the characteristics and category of the defect. The integrated data analysis of CIPS and DCVG showed a correlation which dips pattern on CIPS graph indicating coating defect on DCVG surveyed. Soil resistivity measurement showed that the soil resistivity profile is negligible from KP 0 – 5, while KP 5 – 14 is mildly corrosive. pH measurement showed the acidity level or the soil along the pipeline were neutral. Cathodic protection level could be improved with the increase of cathodic protection current and coating repair along the area with low-level protection.

The use of hydrogels in mixtures to reduce the transient resistance of the soil - grounding device

A method for reducing the resistance of the ground loop for high-resistance soils by using mixtures based on hydrogel is considered as backfill materials. Based on the results of the research, an analysis was made of the effect of mixtures on soil resistivity, the seasonality factor and the resistance of the ground loop at various temperatures and humidity.

Wastewater leakage identification in WWTP and concrete pipelines using integrated geophysical imaging methods

Industry and mining activities covers a broad spectrum of processes that dispose an abundant amount of wastewater. Given the vast array of industries, there are equally large number of heavy metals, organic solvents, and hydrocarbons pollutants associated with its wastewater, posing a great threat to aquifers, especially groundwater. Main contributor of this polluting scheme are from the leakage of underground/surface storage tanks, effluent pipework, industrial sewers, and waste injection system. To ascertain the presence of pollution in the subsoil and groundwater resources, an integrated geophysical method can be the alternative of non-invasive methods. The presence of contaminants in subsoil alters the physical properties of rock formations and decrease pore-water resistance, therefore it can be mapped by geoelectrical resistivity. In this paper, study case was conducted in Medan Industrial Estate, Indonesia, to identify potential leakage under the Wastewater Treatment Plant (WWTP) and its pipework, using Geoelectrical Wenner and Magnetotelluric Method with 5 lines in the interval of 40-60 meters and Magnetotelluric Method throughout the 175 meters of pipework in the production area. Based on the Geoelectrical Method, an anomaly with a low resistivity value was detected within 7 meters of the ground depth. Meanwhile, in the Magnetotelluric Method, a moderate permittivity value was detected that is local and located within 2 meters depth which is where the pipe and the bottom of the WWTP storage tank is located. In conclusion, based on the results obtained from the Geoelectrical and Magnetotelluric Methods that have been carried out in the WWTP area and along the wastewater pipeline leading to the WWTP, no anomalies were found that lead to waste water leakage.

Naive Bayesian classifier and random forest approaches for modeling the electrical resistivity of soils in tropical zones by meteorological variables: case of nine sites in Lomé, Togo

The work combined in this article presents the results of modeling the electrical resistivity of soils based on meteorological data such as geo-referenced coordinates (A), the state of nature the day before (B), the state of nature of the day (C), the ambient temperature (D). A total of 9815 data were sampled over three consecutive years in Lomé, Togo. As methods, we carried out the characterization of the electrical resistivities of the soils measured by Wenner – Schlumberger techniques on nine sites selected in Lomé. Random forests and Naive Bayesian Classifiers are the algorithms used. Certain performance evaluation criteria most commonly encountered in the bibliography are taken into account to evaluate the models. The best result is obtained with random forests and gives MAPE = 17.372%, RMSE = 22.419%, RRMSE = 15.185% and R2 = 70.4%. The result obtained with the naive Bayesian classifier is: MAPE = 24.01%, RMSE = 49.79%, RRMSE = 33.63% and R2 = 37.34%. We deduce from these results that random forests are well suited to predicting the electrical resistivity of soils in tropical areas using meteorological variables. However, it would be good to explore other algorithms to check if the performance will not be better.

Exploration of sustainability of micro grid grounding design in proximity to the pole grounding through experimental measurement of safety parameters

Customarily, while designing the micro grid (MG) grounding the impact of close by grounding is not surmised. Due to which their grounding design becomes more flawed as it results in the fallacious computation of safety parameters, evincing the surplus cost to meet the safety standards. Dynamic seasonal condition, if ignored, makes the grounding design even shoddier. Usually, both these stipulations are not well thought out concurrently, which is the need of the hour. To surmount this, here, a practical case of MG grounding having nearby pole grounding is proposed which is examined in diverse seasons in uniform and three layer soil structures by utilizing finite element method (FEM). Substantiation of the results is done with IEEE standard 80–2013. This article also proposes an experimental setup for the measurement of safety parameters of two groundings in proximity to each other. Moreover, results are corroborated through experimental measurements by building the scaled model. With the contemplation of nearby pole grounding in different seasons, apart from reduction in ground potential rise (GPR) and increase in touch voltage (TV), large deviations in GPR and TV, which otherwise gourd observed, is discovered. Also, with consideration of pole grounding in proximity, a large discrepancy in TV with alteration in resistivity of soil and thickness of soil (concerning grid burial depth) are determined in rainy and freezing seasons.

Evaluation of Physicochemical and Geoelectrical Parameters of Soil and Water around Electronic Dumpsites in Selected Locations of Aba, Nigeria

Electronic waste can be harmful to human health as it contains some heavy metals which alter the wellbeing of people. Aba being a commercial city in Southeastern Nigeria is lying on permeable soil. The indiscriminate disposal of these items makes it expedient for the investigation to be carried out by studying the characteristics of the soil and groundwater quality in order to ascertain the concentration of some of these heavy metals which pollute the water. Resistivities of the soil were determined by employing the vertical electrical sounding method and using some appropriate computer modeling software such as ip2win, surfer12, grapher 8, etc. to interpret the geoelectric sections. Water samples were collected from twenty different locations (BH1 to BH20 and leachate site), then, analyzed using atomic absorption spectrophotometer which revealed the concentration levels of some elements including heavy metals and some compounds such as Al (4.5–40.26 mg/L), As (0.0–3.78 mg/L), Cd (0.0–3.78 mg/L), Cr (0.0–0.543 mg/L), Cu (0.0–21.54 mg/L), Fe (0.15–9.27 mg/L), Pb (0.0–5.604 mg/L), Hg (0.0–2.688 mg/L), Ni (0.0–0.504 mg/L), Ag (0.04–1.2 mg/L), Zn (0.0004–5.2 mg/L), CN (0.84–2.63 mg/L), NH3 (0.004–2.74 mg/L), PO4 (0.3–8.4 mg/L), SO4 (0.0–35 mg/L), etc. The soil resistivities range from 500 Ωm to 1000 Ωm and the depth to water is between 20 m to 40 m. The results revealed that water level is very close to the ground surface and hence, the groundwater is prone to pollution. Also, the percentage concentration of some of the heavy metals is high, which points to a serious threat to life.

Nondestructive testing of seepage in check dams using high-density electrical resistivity tomography based on laboratory test

One of the most significant factors that endanger the safety of check dams is seepage. How to quickly identify the seepage location and pinpoint the seepage path in check dams is directly related to the effectiveness of soil and water conservation measures in the Chinese Loess Plateau. In this study, the improved Miller Soil Box was used to carry out laboratory test of remolded soil, and the effects of moisture content and compactness on soil resistivity were thoroughly examined. On this foundation, the nondestructive testing of seepage was conducted on the Dongmengou check dam based on the different configuration modes of high-density electrical resistivity tomography technology. The laboratory test demonstrates that the soil resistivity and the moisture content exhibit a decreasing power function, while the soil compactness has a negative correlation with the soil resistivity. The interpretation quality of the high-density electrical resistivity tomography technology is significantly improved by the laboratory test, allowing the field test to more precisely detect seepage inside the check dam. As a result, the high-density electrical resistivity tomography technology has good applicability and feasibility in the nondestructive testing of seepage in check dams, and offers a number of benefits, including non-destructiveness, high detection efficiencies and rich data information. It provides an efficient tool for the quick, widespread, and nondestructive detection of dam seepage.

Delineation of Subsurface Migration Pathways of Petroleum Contaminants in Ikarama, Okordia Clan of Bayelsa State, Nigeria

One well-known cause of groundwater contamination in developing nations that produce oil is oil leaks. Oil leaks are typically caused by a variety of circumstances, such as inadequate management and upkeep of oil facilities, equipment failure, and pipeline vandalism by oil criminals. This research evaluates the movement of underground oil contaminants in an oil production field at the Okordia clan's Ikarama hamlet in the Yenagoa Local Government Area in the state of Bayelsa. Schlumberger array was utilized in order to apply the electrical resistivity tomography technique along three (3) VES surrounding the oil spill spot. Values for resistivity were found. In the locations under study, three (3) vertical electrical soundings (VES) were conducted. Comparison of theoretical soil resistivity to measured fluid resistivity for various caption exchange Values of capacity have been researched. The resistivity values, when reversed, ranged from 0.17 m to 146.8 m. The hydrocarbon contamination (oil plumes) is the cause of the high resistivity values (21.54 – 146.8 Ωm) and the low resistivity values (0.1–15.8 Ωm). The 2D resistivity approach is an effective tool for examining pollution caused by hydrocarbon in a coastal environment, as this study has proven.

Research on Lightning Overvoltage Protection of Line-Adjacent Pipelines Based on Solid-State Decoupling

Existing transmission lines and pipelines are frequently crossed and erected in parallel, meaning that if lightning strikes a wire and causes insulator flashovers, the resulting lightning current will spread through the grounding of the tower where the flashover insulator is located. This dispersion of current can lead to overvoltage effects on nearby pipelines. This study performs simulation calculations to analyze the overvoltage experienced by pipelines due to the dispersion of grounding current from the tower. Furthermore, this paper proposes a method for protecting the pipeline from such an overvoltage. Firstly, the lightning transient calculation model of a transmission line tower is constructed using the electromagnetic transient software ATP-EMTP 5.5. The model calculates the effects of lightning peak currents and soil resistivity on the distribution characteristics of lightning current in the tower, specifically in the area where the flashover insulator is located. Subsequently, a calculation model of the tower grounding grid–natural gas pipeline is developed, taking into account the distribution characteristics of lightning current in the tower. This model analyzes the impact of lightning peak currents, soil resistivity, and pipeline spacing on pipeline overvoltage. Finally, the effectiveness of the solid-state decoupler in mitigating lightning overvoltage in the pipeline is verified. The results demonstrate a positive correlation between the lightning current entering the tower grounding grid through the flashover insulator and the lightning current distribution characteristics. The solid-state decoupling device proves to be effective in reducing the voltage of the pipeline insulation layer, and the simulation results provide the optimal laying length of the bare copper wire.

Effect of DC grounding electrode currents on the corrosion interference behavior of cathodic protection of nearby pipelines

When operating a direct current (DC) transmission grounding electrode in single-pole return ground mode, transient currents traverse the soil, generating stray currents. These currents can intensify the corrosion of long-distance transmission pipelines near the grounding electrode, subsequently altering the pipeline’s cathodic protection potential. Previous investigations into the interference of grounding electrodes on pipeline cathodic protection have overlooked the cathodic protection systems themselves. Addressing this gap, we integrated COMSOL’s electrochemical module with its AC/DC module. To corroborate the accuracy of our COMSOL-based models, we devised specific validation experiments. Additionally, we crafted a COMSOL application builder interface to streamline computations. Consequently, we derived a multi-regression function to express the cathodic protection potential of the pipeline under varied factors and executed a regression tree classification for soil resistivity. To pinpoint optimal corrosion protection for pipelines, we simulated the cathodic protection of segmentally isolated pipelines, determining that potential excursions can be notably mitigated. This research offers insights into both disturbance evaluation and protective strategies for DC transmission and pipelines.

A comparative numerical evaluation of linear anode arrangements for enhancing above ground storage tank cathodic protection via mesh grid and concentric ring designs

Cathodic protection as a complementary method is one of the most effective ways to prevent corrosion, along with coating and choosing the suitable material. There are different ways to protect the storage tank bottom. Due to the presence of the geo membrane layer and its effective and pivotal role, the use of mixed metal oxide (MMO) anodes is highly recommended. In the current study, the protection process of the above-ground storage tank bottom is simulated using MMO backfilled wire (concentric rings) and ribbon anodes (mesh grid system). In this regard, several parameters must be considered in reaching the protection criteria. The simulation results show that the effect of the limiting oxygen current density, soil resistivity and the anodic current have the greatest role. Anode depth and the spacing between the anodes are also critical factors if they have large values. Due to the importance of the number of conductor bars and feeding cables, two configurations have been presented for ribbon anodes. These configurations have a direct impact on grid resistance, rectifier size, and related costs. Finally, an economic comparison has been made regarding the use of sacrificial and MMO anodes in the form of ribbon next to wire anodes. The results show that, in the use of ribbon anodes, MMO anodes have better performance than magnesium and zinc sacrificial anodes, and the cost required for MMO linear anodes is far lower than the method of sacrificial ribbon anodes. In the present study, the cost of the MMO linear anode system is approximately 20% of zinc and magnesium sacrificial ribbon anode system cost.

Study and application of coupling relationship between water-salt-resistivity-soil structure in saline soils in arid and semi-arid areas of northwest China

Widespread saline soils in Northwest China pose a serious threat to the region's ability to use infrastructure safely because they are prone to soil structure damage when subjected to external environmental fluctuations, which in turn affects the stability of the foundations for buildings. The non-destructive approach of measuring resistivity can be used to swiftly reflect the subsoil body's state and make assumptions about its safety. However, the electrical resistivity of the underground soil body can be used to quickly identify unstable areas because the resistivity is influenced by the water content, salt content, and structural characteristics of the soil body. To do this, it is necessary to understand the coupling relationship between various factors. In this study, we first constructed samples with various water, salt, and soil structure characteristics, and then used indoor tests, such as soil resistivity measurement and thermogravimetric analysis, to analyze the multiple factors affecting the resistivity characteristics of the soil. The relationship between soil resistivity and actual saline soil diseases in Northwest China was then further discussed in conjunction with the results of the indoor tests and analyses. subsequently, the resistivity and soil properties have been measured in the field at specific locations in Northwest China where railway roadbeds are diseased. The study's findings can theoretically support a deeper comprehension of the law and mechanism of soil resistivity change, as well as provide assistance for building infrastructure in Northwest China.

3D Resistivity Imaging Investigation for Engineering Construction Project Studies at Al-Muthana Airport in Baghdad, Iraq

Engineering project assessment at Al-Muthana Airport in Baghdad, Iraq, has been studied using a 3D electrical resistivity imaging survey. The site investigation is crucial for assessing the future of the region's infrastructures since it reveals the location of buried facilities or weak zones below the surface and measures localized groundwater levels. Wenner-Schlumberger array was used to conduct four parallel 2D electrical resistivity spreads (MU1 to MU4). Each spread line was 100 m in length with 1 m electrode spacing and an average spacing of 9 meters between any two adjacent lines. The depth of the investigation was around 23.8 m. Survey lines were drawn going from northwest to southeast. These spreads were combined to provide a 3D image of a 2700 m2 space.The robust inversion method and the inverse model generated using the standard least-squares method showed horizontal slices identified three zones with resistivity distribution ranging from 2 to 45.5 ohm.m. The first zone, from surface to 3.37 m, had relatively high resistivity of sandy silty clay soil with relatively low moisture content; the second zone, approximately from 3.37 to 12.2 m, had very low resistivity representing groundwater table; and the third zone, from 12.2 to 23.8 m representing high stiffness and density and relatively high resistivity due to gravel presence in the deposits. The second zone highlights potential risk zones for construction projects; as a result, it is advised that the zone surrounding the foundation be filled with a low permeability layer and that the towers be built on deep foundations.

Reducing the risk of missing soil contamination by integrating multi-investigated methods in a retired chrome salt factory

An effective contamination screening process is essential for mitigating the risk of overlooking pollution during site investigations. While Electrical resistivity tomography (ERT) and portable X-ray Fluorescence (XRF) offer quick assessments of contaminated areas, there is a notable gap in research regarding ERT’s application in the unsaturated soil layer, and portable XRF’s use for screening polluted samples in chromium-contaminated sites. This study gathered soil pollution and electrical resistivity data from a decommissioned chrome salt factory, employing drilling, sampling, XRF, and ERT methods. Predominantly, sulfate and chromium emerged as the pollutants, with concentrations ranging from 19.24 to 12700.00 mg/kg for sulfate, 0.65 to 3000.00 mg/kg for Cr(VI), and 12.00 to 27800.00 mg/kg for total Cr, respectively. Polluted hotspots were identified by lower apparent soil resistivity compared to the background levels at corresponding depth. Notably, a significant inverse correlation was observed between sulfate and Cr(VI) concentration and soil resistivity, particularly with sulfate (R2 =0.48) demonstrated through a power function fit at depths ranging from −4 to 0 m. The XRF analysis for total Cr concentration exhibited a significant correlation (Pearson’s r = 0.67) with chemical analysis, confirming 1000 mg/kg as an effective screening threshold. In light of these findings, this study proposes a scientific procedure that integrates drilling, sampling, ERT, and XRF for soil contamination investigation. This framework aims to support similar site assessments, reducing the risk of overlooking contamination.