Geoelectrical Methods Research Articles

Characterization with geoelectrical methods of fissural porosity and flow pattern in physical models of fractured rock masses

Understanding water flow through discontinuities in rock masses is essential for ensuring the safety of engineering works, understanding the transport of contaminants, and directing the prospection and production of water in fractured aquifers. Investigation methods such as boreholes are expensive and not always effective. An alternative can be indirect investigation with electrical geophysical methods, such as Electrical Resistivity (ER) and Streaming Potential (SP), owing to their technical feasibility, low cost, and speed of execution. Although well established, doubts remain about these surveys owing to field limitations. In this sense, simulations in reduced physical models, where the internal and boundary conditions tend to be known, are ideal for testing these surveys. In this study, a rock mass model was developed with vertical fracturing patterns covered by soil; the entire set was saturated, thus reproducing the conditions common to areas of the crystalline basement with a tropical climate. With the use of ER and SP, the objective was to map the preferential flow directions with and without deep tube well influences and estimate fissure porosity. ER results showed an efficiency of 85% in the estimation of porosity, clearly distinguishing the main directions of anisotropy by the fractures. With SP, it was possible to identify flow directions through the fractures and define the geometry of the depression cone caused by pumping a deep tube well. Overall, these findings demonstrate the feasibility of physical models for understanding media with fissural porosity.

Processing of electrical resistivity tomography data using convolutional neural network in ERT-NET architectures

Electrical resistivity tomography (ERT) inversion has emerged as an effective method for predicting resistivity in complex geological structures. In most cases, traditional ERT inversion problems are posed as nonlinear optimization problems. Solving distribution resistivity inversion can be computationally challenging for two reasons: one is the significant cost of software and the other is the issue of local minima. The ERT-NET architecture was developed in this study to learn the parameter regression relationship between geophysical ERT datasets and subsurface models. We developed a novel convolutional neural network (CNN) technique that comprised of a fully connected network (ERT-INET) and a fully convolutional network (ERT-UNET); both train ambiguity information of the inverted resistivity based on processing ERT datasets. We also output our network segmentation of pixel-wise prediction for ERT-INET and structured prediction segmentation. The noise assessments of our network inversion were managed by employing depth of investigation (DOI) and statistical analysis for evaluation performance. The DOI appeared to be effective in conveying the breadth of possibility within our networks. Moreover, the performances are either the synthetic resistivity model or the field resistivity data, both of which have an average of greater than 95%. The inversion results of both architectures are precisely and accurately expressed, containing approximately the ground truth models and thereby also the field observation models. We conclude that these ERT-NET architectures could be one approach to ERT interpretation handling, and we strongly suggest alternatives that promote the geoelectrical method of interpretation.

PROSES PENGAMBILAN DATA DAN PEMANFAATAN GEOLISTRIK METODA 4-D UNTUK PEMETAAN GEOLOGI BAWAH PERMUKAAN

Geoelectricas as a method and tool for exploration has been started since the 1900s.The development of computer technology at this time makes the application of geoelectric method is now becoming more popular.The application of geoelectric methods usually for groundwater exploration but now widely used for mineral exploration and engineering geology.Today's inversion technique uses many geo-electric methods with 3-D configurations. The process of selecting the geoelectric method is important so that we can choose to use it. This research was conducted to utilize 4-D geoelectric method to identify object dynamics: waste seepage, soil density and groundwater. The application of this method (4-D) was identified to be used for monitoring and detecting potential flow of a fluid or sediment.
 Â

Identification of the Distribution and Volume of Iron Sand in the Gura Beach Area Using the Wenner-Schlumberger Configuration Geoelectric Method

The Naniura NRD300 HF tool has been used in research using the Wenner-Schlumberger configuration geoelectric method to determine the direction of iron sand distribution, the volume of iron sand, and the concentration of iron sand in the Gura beach area. The collected measurement results are then processed by the RES2DINV software into a 2 Dimension (2D) cross-section that shows the distribution values of the subsurface layer as shown by a color image. Once saved in (.xyz) format, the RES2DINV software results are processed in RockWork software to create pseudo-3D cross sections. The RES2DINV software's results show that line 1's resistivity value ranges from 39.6 to 1000 Ωm, whereas line 2's resistivity value ranges from 0.16 to 1.7 Ωm. These findings suggest that line 2 has a lower resistivity value than line 1 does. The volume of iron sand processed by RockWork software is 221,000 cubic meters for linek 2 and 273,000 cubic meters for line 1. The distribution of iron sand deposits in the study region is south to north, based on the volume of iron sand in line 1, which is bigger. A method used to determine the composition of the minerals present in a sample is called X-ray fluorescence (XRF). The results of analyzing the Fe content in line 2 are 55.01%, which is higher when compared to the Fe content in line 1, which is 40.5%.

Analisis Struktur Lapisan Tanah Menggunakan Metode Geolistrik Resistivitas Konfigurasi Schlumberger Vertikal di Kompleks Perumahan Dosen Uncen Kali Acai, Kulurahan VIM, Distrik Abepura, Kota Jayapura

Research on the analysis of the structure of the soil layer using the Vertical Schlumberger Geoelectric method in the Lecturer Housing Complex of Uncen Kali Acai, VIM Village, Abepura District, Jayapura City. This study aims to determine the soil layer, determine the location and depth of the soft soil layer, determine the soft and hard soil. Data retrieval using geoelectric resistivity method with vertical Schlumberger configuration. The instrument used for subsurface surveys is the HV 500 AK resistivity meter. Field measurements obtained electric current and voltage values and then calculated the apparent resistivity values obtained from analysis using IP2win software to see the distribution profile, depth, and thickness of the soil layer.After doing research in the field, it can be seen that the subsurface structure at the research site is dominated by soft clay material with a resistivity value of 0.24 -692.00 Ωm. . In addition, there is a layer of hard rock in the form of a mixture of limestone with a resistivity value of 1181.00 - 8319.00 Ωm.. And the types of subsurface rocks found at the research site are clay, sandstone and limestone.

Eksplorasi Batuan Andesit Berdasarkan Interpretasi Data Resistivitas Di Desa Petangis, Kecamatan Batu Engau, Kabupaten Paser

Exploration activities are very important before mining andesite rocks. This research was conducted in Petangis Village, Batu Engau District, Paser Regency using the Wenner-Schlumberger geoelectric resistivity method with 10 tracks, where 7 tracks have a length of 705 meters in an East-West direction and 3 tracks have a length of 235 meters in a North-South direction. The purpose of this study is to identify the resistivity value of andesite rocks and determine the 2D and 3D distribution of andesite rocks based on the obtained resistivity values. Based on the 2D resistivity section results, it was found that in the study area, andesite rocks have resistivity values ranging from 212-460 Ωm with varying depths of 1-52 meters and the 3D modeling results indicate that andesite rocks are predominantly distributed on the East side with an estimated volume of 1.34588e+007 m3.
 Keywords: Andesite, Exploration, Resistivity, Wenner-Schlumberger.

Identifikasi Pencemaran Air Lindi pada Kawasan Asrama di Kampus Universitas Udayana dengan Menggunakan Metode Geolistrik Konfigurasi Wenner

Dormitory land in the Udayana University area is often used as a place to dispose of garbage. Basically leachate contains metal content such as zinc (Zn) and mercury (Hg) which seep into the soil. Identification to determine the presence of leachate at a certain depth, can use the Wenner Configuration Geoelectrical Method. From the data obtained then processed using Res2dinv it was found that the leachate content in the Udayana University Dormitory Area is found at a distance of 33m, 43m, 63m, 83m, from the pile of garbage and a depth of 1.25 - 3.75m below the surface of the pile of garbage for coordinates 115.165240 BT, 8.798640 LS to 115.164955 BT, 8.799100 LS and a distance of 62m, 72m, 82m, from the garbage pile and a depth of 1.25 – 6.38m below the surface of the garbage pile at coordinates 115.165091 BT, 8.798557 LS to 115.164730 BT, 8.799021 LS.

Geotechnical, Geoelectric and Tracing Methods for Earth/Rock-Fill Dam and Embankment Leakage Investigation

Geotechnical, Geoelectric and Tracing Methods for Earth/Rock-Fill Dam and Embankment Leakage Investigation

Shaping the concentration of petroleum hydrocarbon pollution in soil: A machine learning and resistivity-based prediction method

A new method relying on machine learning and resistivity to predict concentrations of petroleum hydrocarbon pollution in soil was proposed as a means of investigation and monitoring. Currently, determining pollutant concentrations in soil is primarily achieved through costly sampling and testing of numerous borehole samples, which carries the risk of further contamination by penetrating the aquifer. Additionally, conventional petroleum hydrocarbon geophysical surveys struggle to establish a correlation between survey results and pollutant concentration. To overcome these limitations, three machine learning models (KNN, RF, and XGBOOST) were combined with the geoelectrical method to predict petroleum hydrocarbon concentrations in the source area. The results demonstrate that the resistivity-based prediction method utilizing machine learning is effective, as validated by R-squared values of 0.91 and 0.94 for the test and validation sets, respectively, and a root mean squared error of 0.19. Furthermore, this study confirmed the feasibility of the approach using actual site data, along with a discussion of its advantages and limitations, establishing it as an inexpensive option to investigate and monitor changes in petroleum hydrocarbon concentration in soil.

Geoelectric Analysis for Potential Slip Plane Interpretation in Labuan Bulan Hill, Salem District, Brebes Regency, Central Java

Landslide is a natural disaster which often occurs in Indonesia. Based on National Disaster Management Agency (BNPB), there were 1,321 landslide incidents which occurred in 2021. Labuan Bulan Hill located on high susceptibility landslide seen from Landslide Susceptibility Zone of Brebes Regency, furthermore, soil tensile cracks presence with 5 - 50 cm width and 15 - 125 cm height at upper slope. In this study, the identification of subsurface lithologies and potential slip plane was carried out using geoelectric survey method with Wenner – Schlumberger configuration. The Wenner – Schlumberger configuration has deeper penetration than other geoelectric survey configurations. Geoelectric surveys are carried out on two lines with 240 m length and 5 m electrode space. Geoelectric line is made parallel and perpendicular with slope direction to estimate subsurface conditions easier with the help of tensile cracks presence in the surface. Results of measurements identified that the upper layer consists of poorly graded silty sand with 285 Ωm – 1700 Ωm resistivity, the second layer is a moderate - highly weathered volcanic breccia with 129 Ωm – 285 Ωm resistivity, and the third layer is fresh – slightly weathered volcanic breccia with 285 Ωm – 1388 Ωm resistivity. A fresh – slightly weathered volcanic breccia layer was identified as potential slip plane with 20 – 30 m depth.

GEOELECTRIC PHASOMETRIC CONTROL OF THE RAILWAY TRACKBED

During the operation of the railway track, various defects and deformations may occur and accumulate in the earth bed and its soil base, which leads to a violation of their bearing capacity. The task of developing new technological methods for monitoring the condition of the ground foundation – roadbed – railway track system is becoming urgent. The article proposes a geoelectric phase-measuring method for monitoring the phase of recorded signals with changes in the load on the ground at the base of the railway track. The control of phase characteristics allows for greater sensitivity, accuracy and noise immunity compared to the control of the amplitude of geoelectric signals. The developed laboratory setup allows simulating various natural processes (changes in soil moisture, suffusion, karst dips, landslides, landslides, and others) and assessing their impact on the railway transport complex. The installation contains a model of the controlled object (a container with soil), generators of probing signals, a subsystem for recording signals in the environment, a subsystem for data processing. The proposed approach makes it possible to detect early geodynamic indicators of deformations of the railway trackbed.

Identification of the Groundwater Layer using the Resistivity Method of the Schlumberger Configuration in the Bumi Harapan Village Area

This research applied the geoelectric method to determine the presence of aquifer layers in Bumi Harapan village. This method can determine the value of subsurface resistivity, and from this value, will know the lithology based on the distribution of subsurface resistivity. The lithology results will be described in the form of resistivity logs to make it easier to find the groundwater layer and its depth. Subsurface lithology obtained structures in the form of topsoil, clayey sand, sandy clay and clay. The layers suspected as groundwater layers are sandy clay and clayey sand. The results of the presence of average groundwater at a depth of 4 - 9 meters with sandy clay and clayey sand in the fourth and fifth layers were also found at a depth of 90 - 100 meters below the ground surface. The results of the resistivity values that are thought to be the groundwater layer are found to be 125 – 317 Ωm. Formation factor in determining the type of soil layer as an estimate of groundwater potential Below the surface. The formation factor in this study was found to be in the range of 1.7-8 with a type of aquifer layer to a medium aquifer.

Groundwater monitoring and specific yield estimation using time-lapse electrical resistivity imaging and machine learning

This paper presents an alternative method for monitoring groundwater levels and estimating specific yields of an unconfined aquifer under different seasonal conditions. The approach employs the Time-Lapse Electrical Resistivity Imaging (TL-ERI) method and machine learning-based time series clustering. A TL-ERI survey was conducted at ten sites (WS01-WS10 sites) throughout the dry and wet seasons, with five-time measurements collected for each site, in the Taichung-Nantou Basin along the Wu River, Central Taiwan. The obtained resistivity raw data was inverted and converted into normalized water content values using Archie’s law, followed by applying the Van Genuchten (VG) model for the Soil Water Characteristic Curve to estimate the Groundwater Level (GWL), and estimated the theoretical specific yield (Sy) by computing the difference between the saturated and residual water contents of the fitted VG model. In addition, the specific yield capacity (Sc), representing the nature of the storage capacity in the aquifer, was also calculated. The results showed that this approach was able to estimate those hydrogeological parameters. The spatial distribution of the GWL reveals that during the dry-wet seasons from February to July, there was a high GWL that extended from southeast to northwest. Conversely, during the wet-dry seasons from July to October, the high GWL shrank, which can be attributed to recharge variations from rainfall events. The determined spatial distribution of Sy and Sc fall within the range of 0.03–0.24 and 0.14–0.25, respectively. To quantitatively establish areas of similar groundwater level changes along with the VG model parameter variations during the study period, a Time series Clustering analysis (TSC) was performed by utilizing Hierarchical Agglomerative Clustering (HAC). The findings suggest that the WS03 site is a promising area for further investigation due to its highest Sc value with a slight change in groundwater levels during the dry and wet seasons. This study brings an advanced development of the geoelectrical method to estimate regional hydrogeological parameters in an area with limited available groundwater observation wells, in different seasonal conditions for groundwater management purposes.

Groundwater aquifer delineation using Poisson’s ratio analysis from microtremor data inversion

To develop new potential wells, in this research study identification and delineation of groundwater aquifer used Poisson's ratio extracted from microtremor inversion data in an area of 240 x 174 m2 with 22 microtremor measurement stations. As a referred station is the former drilled well that is used to determine the location of the well using the geoelectric method. Based on the 2D and 3D modeling of the Poisson's ratio value, it can be delineated the subsurface aquifer and the possible direction of developing new drilling locations.

Soil resistivity measurements to evaluate subsoil salinity in rice production systems in the Vietnam Mekong Delta

AbstractRice is a staple crop in the Vietnam Mekong Delta (VMD) in which more than half of Vietnam's rice is produced. However, rice production in the VMD is threatened by increasing saltwater intrusion due to land subsidence and climate change induced sea level rise. Saltwater intrusion into lowland areas through the canal system or capillary rise of saline water from near surface saline water tables may result in salt accumulation in the topsoil. Therefore, it is important to disentangle the two effects and their relative importance to implement appropriate strategies for water and salinity management for adapting rice production systems of the VMD to climate change. Here, we report on the possibility of using geoelectrical methods to evaluate the potential threat of subsoil salinity to rice production. To evaluate the level of subsoil salinity, we measured soil electrical resistivity using an ARES II to a depth of 40 m in a case study comprising five locations in the VMD. Electrical resistivity measurements were calibrated to soil types, which were identified through evaluating 1 m core sections obtained by drilling down to 40 m depth. The relationship between drilling data and soil resistivity was determined by applying clustering and principal component analysis. Resistivity values smaller than 3 Ω m were clearly identified as indicative for a saline water table. The results show a direct link between the depth of the saline water table and the proximity to the sea, but not to the rice production system (single, double, or triple cropping). This study proved for the first time the applicability of the electrical resistivity tomography method for identifying groundwater tables and evaluating subsoil salinity on an agricultural field scale in the VMD.

3D Modeling of Leachate Distribution Around Zone E of Batu Layang Landfill, Pontianak, West Kalimantan, Indonesia Using the Geoelectrical Method

Open dumping systems as implemented by the Batu Layang landfill in Pontianak City, Indonesia can cause leachate pollution in the environment. The constituent soil condition affects the leachate distribution into the ground. One of the landfill constituents of the soil at the site of the Batu Layang landfill is peat soil, in which organic content (>75%), porosity, and permeability are high. Leachate that seeps below the earth’s surface can cause soil and groundwater contamination. Meanwhile, people around landfills use groundwater for their daily needs and use the land around the landfill to grow papaya, banana, sugarcane, and taro. Therefore it is necessary to prevent and minimize leachate spread. One of the efforts that can be done is to model the leachate distribution. In this study, leachate distribution modeling was done with a geoelectric method, the Wenner configuration, with a smallest electrode distance of 5 m. There were six tracks, with a length of 195 m each. The model obtained from this study was a 3D resistivity section. 3D data processing was done using the inverse distance method. The results showed that a resistivity value ≤10 Ωm identified the soil layer contaminated with leachate. The contaminated soil layers were estimated to be peat, clay, and loamy sand. The leachate distribution is suspected of seeping up to 195 m south of the landfill. The leachate distribution into the soil was estimated from the surface to 33.8 m.

Estimation of Groundwater Potential at Khalid Bin Walid Boarding School Using the Schlumberger Configuration Geoelectric Method

Khalid Bin Walid Islamic Boarding School is one of the Islamic boarding schools in Rokan Hulu Regency. This school is located in a water crisis area with complex groundwater sources. This study aims to determine the potential of groundwater as a reference for drilling wells and to determine the structure of the subsurface layer by using the geoelectrical method. The geoelectrical method is a method that is widely used, and the results are promising, namely, to obtain an overview of the subsurface soil layers and the possibility of groundwater presence. The configuration used in this study is the Schlumberger configuration using the basic principle of current propagating in the earth when injected in all directions and the assumption that the potential of the subsurface rock layer is the same. Data will be collected on four tracks, with a track length of 100-200 m. From the data processing results, it was found that potential sources of groundwater on track 3 with a depth of 13.7–30.3 m with alluvium rocks were suspected. Groundwater on this track can be used as a source of clean water using drilling.

INVESTIGATION OF THE GEOTHERMAL RESOURCE POTENTIAL USING GEOELECTRICAL METHOD WITH THE WENNER CONFIGURATION: A CASE STUDY IN LEBONG REGENCY, INDONESIA

In geothermal reservoirs, hydrothermal distribution is significant. The most widely utilized geothermal reservoirs to date are those of hydrothermal systems, which are geothermal systems where the reservoir contains steam, water, or a mixture of both, depending on the pressure and temperature of the reservoir. One of geophysical method that is enough to map subsurface conditions to determine the hydrothermal distribution is the 2-Dimensional Geoelectric method using the Wenner configuration. This method aims to study the variation of rock resistivity below the earth's surface, resulting in a two-dimensional profile of the subsurface resistivity model used to describe the layered subsurface resistivity structure. The results are in the form of 2-Dimensional modeling of the distribution of hydrothermal manifestations with data processing using pyGIMLI (Python Library for Inversion and Modeling in Geophysics) software. In the study area Pungguk Pedaro Village, Bingin Kuning District, Lebong Regency, the Hulusimpang Formation has a high alteration intensity, as evidenced by the weathering in rocks and the micrographic appearance. The types of stones found in this research area include andesite rocks, including sandy gravel, volcanic breccia, tuff, andesite, basalt, basalt-andesite sand, silty sand, and clay. Or rocks derived from acidic magma.

Underground-caves connectedness preview using the geoelectrical profiling method as an effort to revive natural tourism in “Gua Pandan,” East Lampung Regency

The Covid-19 pandemic has made one of the tourists in the East Lampung regency inactive, namely “Gua Pandan.” Due to its unique location geologically, efforts must be made to revive the area. One of the approaches is applying an indirect method, namely the geophysical method. One of them is the geoelectrical profiling method. Six lines are spread in the study area with a length of 70-105 m. The target is a cave filled with air because it is suitable as a tourist spot. Based on the measurement results, a very high resistivity value of more than 5,000 Ωm is suspected to be an air-filled cave. The cave area that is probably safe is about 120 m long with 1-3 m depth below the ground surface, 2-8 m width, and 2-6 m height. However, a safety assessment is necessary for feasibility so that the cave is worthy of being re-activated as a tourist spot.

Detection of groundwater aquifers using geoelectrical resistivity method (case study : Plupuh Sub-district, Sragen District )

An aquifer is a layer below the ground surface that contains groundwater. Inside the earth there are unconfined aquifers and confined aquifers, where unconfined aquifers are located near the surface while confined aquifers are located very deep beneath the earth. This study aims to find the location, depth, and thickness of aquifers that have the potential to contain large amounts of groundwater. The instrument used in this research is a resistivity meter OYO Model 2119C Mc OHM-EL, with a Schlumberger configuration with a current electrode length of AB/2 to 350 meters. Data acquisition were carried out in the Plupuh sub-district, Sragen district as many as 5 sounding points, and data processing using IP2win software. Based on the interpretation of resistivity geoelectrical data, it can be concluded that the area has the potential to have a lot of groundwater content, for unconfined aquifers at the TS1 sounding point with a depth of 7.7 meters to 19.2 meters with a thickness of 11.5 meters. and TS4 with a depth of 15.4 meters to 30 meters with a layer thickness of 14.6 meters. This aquifer layer is dominated by sand layer lithology, while the confined aquifer layer is located around TS1 and TS2. The two sounding points are located in the east and northeast of the research area. TS1 was detected at a depth of 39.9 meters to 110 meters with a layer thickness of 60.1 meters and TS2 was at a depth of 40.2 meters to 66.5 meters and 80.2 meters to 139.7 meters with a thickness of 84.8 meters. This aquifer layer is dominated by the gravel sand layer in TS1 and the sand layer in TS2.