Search

This study explores the comprehensive approach of utilizing physiographical and geophysical electrical resistivity tomography (ERT) investigation to evaluate and address the challenges associated with abandoned, unplanned water-filled galleries in Chasnala Colliery, located in Jharkhand, India. The integrated methodologies facilitate a thorough examination of subsurface conditions, encompassing factors such as geological stability, hydrological fluctuations, and environmental considerations. Utilizing physiographical analysis is of utmost importance in identifying locations with potential risks and developing appropriate site-specific reclamation procedures in the study area. The ERT analysis has successfully confirmed the findings of the physiographical study, revealing the presence of five distinct underground galleries, namely, GL1, GL2, GL3, GL4, and GL5, that are likely submerged in water. These galleries establish connections between the underground spaces and the groundwater, as indicated by their low resistivity values of ~50 Ωm or less. The resistivity measurements exhibit variations that can be attributed to fluctuations in the underground water content. The Wenner, Schlumberger, and dipole–dipole arrays have adeptly discerned the existence of water-filled underground galleries with commendable accuracy. However, the joint array configuration stands out as the pre-eminent choice among these standards due to its unparalleled technical robustness. The findings concurred with the notable correlation between water-filled galleries’ spatial arrangement and shallow groundwater level. The integration of physiographical and ERT data improves the precision of subsurface characterization, facilitating informed decision-making for efficient water management and site rehabilitation in the context of opencast mining. [ABSTRACT FROM AUTHOR]

In many cases, the lateral extension of economically valuable mineral deposits is linked to fractures. Knowing the characteristics of these tectonic structures is crucial for determining the continuity of mineralization in the subsoil and, consequently, for planning their exploitation. To address this challenge, a multidisciplinary study was carried out using various geophysical techniques and direct field observations to analyze the effectiveness of each technique in the investigation of fractures. For this purpose, the mining district of Linares-La Carolina in southeastern Spain, known for hosting Philonian deposits of galena (PbS), was chosen. At the southern boundary of this mining district, the seams stopped being exploited when they lost their continuity due to the presence of a regional normal fault. This fault zone was responsible for hiding the seams under a thick sedimentary cover. Detailed geological mapping allowed us to deduce the presence of two fracture systems. The geophysical techniques of electrical resistivity tomography and the time domain electromagnetic method were used, allowing us to identify the positions and the vertical displacement of these faults. Furthermore, using magnetometry, the presence of a third system of fractures was deduced. The results showed that this multidisciplinary analysis provides information of interest concerning the complex structure that configures the limits of this mining district. [ABSTRACT FROM AUTHOR]

This article deals with the issue of diagnostics of the physical condition of earthen dams, taking into account seasonal changes in the water level of hydraulic structures using electrical exploration methods. The simplicity of the method, the accuracy of measurements of geophysical parameters, and the availability of software packages for the processing, interpretation, and visualization were the basis for the choice of method. The method of electrical resistivity and self-potential was chosen. The methodology, technique, technology of field surveys, processing, and geological interpretation of the study results are given. A comparative analysis of the obtained geophysical parameters of seasonal measurements is given. The research results are given in the form of sections of the resistivity model and self-potential isolines. [ABSTRACT FROM AUTHOR]

This study evaluates the impact of seepage on the integrity of artificial levees in low-lying regions, with a particular focus on Hungary, where levees built over a century ago lack comprehensive construction documentation, complicating current assessments of their effectiveness. Advanced geophysical methods – electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) – were applied in a controlled tank experiment designed to simulate varied flood conditions along a 37-m levee section. The three-dimensional (3D) ERT profiles successfully delineated seepage pathways as the tank filled, while the 3D GPR profiles indicated areas of increased amplitude, corresponding to seepage zones and the water table. Validation through drilling confirmed the geophysical findings, underscoring the accuracy of ERT and GPR in non-destructively identifying subsurface features and seepage channels. The results highlight the applicability of these methods for evaluating levee integrity and seepage dynamics, offering a reliable approach for flood risk assessment in Hungary and similar flood-prone areas worldwide.

Ponds are a unique agricultural irrigation method with a long history in the Taoyuan area. However, most of them lack accurate spatial information, such as water depth, water surface area, and effective water storage capacity. In this study, the water depth of pond was measured using an unmanned surface vehicle, which has the advantage of being able to operate in shallow waters and in areas that are inaccessible to manned boats. The results show that it can rapidly provide 3D point cloud and an underwater 50 cm gridded digital elevation model with an accuracy of 6.7 cm, which can be used to identify structural defects at the pond bed and the embankment and to accurately estimate the water surface area and effective water storage capacity. The nests with diameters of 30 to 70 cm dug by male tilapia to attract female tilapia for spawning can also be found. In addition, the ground-penetrating radar and electrical resistivity tomography were carried out to successfully investigate the electricity-related properties of the internal structure of the embankment and the leakage locations of pond. In conjunction with the maintenance experience of the Taoyuan Management Office, a risk reference index was proposed for the safety management.

Abstract Applying the electrical resistivity tomography (ERT) technique in detecting very near-surface targets is quite challenging in geophysical investigation, especially in civil and environmental engineering for adequate planning and designing of structural foundations, contributing to the overall safety and efficiency of construction projects. However, locating the exact position and depth of underground targets such as faults, underground utilities, and contaminants is more challenging. Therefore, this study is aimed at examining the geophysical response of various buried targets and evaluating the ability of ERT to detect buried targets in terms of locations and depths of occurrence in the context of engineering investigation and environmental studies. A laboratory test was conducted on the targets to determine their electrical conductivity and resistivity before burial. The two-dimensional (2D) ERT survey was performed on thirteen targets buried at the site using both Wenner and dipole–dipole (DD) arrays. Both arrays captured the metallic targets with a low electrical resistivity contrast (

The design of tailings dams has improved significantly in recent decades due to experience and advances in applied research. However, there are still several environmental and geomechanical uncertainties associated with the response of these structures. Failures on the wall of tailings dams are well documented, where the most common causes are related to the action of water overtopping, slope instability, seepage, and foundation failure. Measuring the humidity or the saturation level at tailings dam walls has become a must do in the recent years. Resistivity monitoring using electrical resistivity tomography (ERT) techniques has proven to be one of the tools that provide good subsurface characterization for internal erosion detection and seepage assessment to evaluate potential environmental risks and the physical stability of tailings dams. Also, the integrated techniques of geotechnical, geophysical, and geochemical data have been used to correlate, coordinate, and improve the characterization. In this research, a procedure to guide us to a new methodology of acquiring and monitoring humidity content is presented, in which 2D electrical resistivity tomography (ERT) profiles are linked to the degree of soil saturation, using moisture sensors installed in a nearby well. The ERT profiles provide a 2D resistivity profile, and the moisture sensors can measure resistivity and volumetric water content (VWC) at a given installation depth. This second measure (VWC), with a defined total porosity, can be combined with Archie's empirical law to obtain the degree of saturation, allowing the possibility to create remote monitoring suitable for mining operations without excessive laboratory testing. [ABSTRACT FROM AUTHOR]

This study is conducted within the Gambia River Basin Development Organization Energy Project (OMVG) framework. The construction of a high voltage interconnection network fed by a hydropower station to supply electricity to OMVG Member States was done on stable ground. During the installation pits for the pylons in Labé Prefecture, Republic of Guinea, cavities were discovered in the geological formations during the initial planned route. Structurally, the study area is bounded by two major faults to the east and west of northeast direction. The geomorphology is made up of a central plateau, intermountain depressions, piedmont plains, talwegs, and glacis. Geological investigations were obtained by a geophysical Two-dimensional Electrical Resistivity Tomography (ERT) method. The results show that the synthetic lithological profile from top to base was sandy-clayey soil, hard cuirass, and a layer of gravel followed by a mottled zone comprising an indurated part and an imbibed part just before the source rock. The cavities were observed probably because of the dissolution of certain minerals constituting the weathering crust due to the infiltration, underground waters, and the seasonal variation in the level of the surface watercourses. Geophysical results showed a very good agreement with the visual observations. [ABSTRACT FROM AUTHOR]

Abstract—The paper discusses anomalies that are observed in the electric fields above hearth deposits. Hearths are important objects for archaeological studies and are traditionally detected by the positive anomaly in magnetic induction. However, magnetic measurements are not available on every archaeological site, and burning sites are not the only sources of positive magnetic anomalies. In the 1960s, it was established that the hearths can be detected using the induced polarization method (IP), but the technique has not been developed because of the imperfection of equipment at that time. Currently, multi-electrode multichannel electromagnetic prospecting systems allow prompt assessment of the distribution of electrical properties of the object and reconstructruction of its three-dimensional geoelectric structure. In this study, we examined geoelectric anomalies from a hearth, elucidated their nature, and evaluated the possibility of using electrical resistivity tomography (ERT) method to search for such objects. By the example of the fieldwork and laboratory experiments it is shown that hearths create intense anomaly of induced polarization and are distinguished by a very low electrical resistivities. It is established that the boundaries of the burning sites are clearly expressed in the maps of normalized chargeability. To study the nature of the observed geoelectrical anomalies, we carried out X-ray phase analysis and measurements of induced polarization, electrical resistivity, and magnetic susceptibility. The results have shown that the anomaly of low electrical resistivity and the polarizability anomaly are caused by the presence in hearth material of X-ray amorphous carbon in the form of soot, but not magnetite. Application of electrical resistivity tomography combind with induced polarization measurements is recommended in the search for fireplaces in archaeological prospecting. [ABSTRACT FROM AUTHOR]

In 2020, in the caldera of Uzon volcano (Kamchatka Peninsula), electrical prospecting studies were carried out using the electrotomography method within the eastern thermal field near Shaman geyser. The geoelectric section is divided into three zones according to the level of electrical resistivity: relatively high-resistivity cold zones at the edges and a relatively low-resistivity hot zone in the center. The hot zone, situated at a depth of 5–20 m and hosting the Shaman geyser, is distinguished by anomalously low resistivity (less than 0.5 Ω m), which indicates the highest fracturing and saturation of rocks with fluid. Resistivity monitoring was carried out above the geyser using an Omega-48 electrical tomography station and two cables with lengths of 235 and 47 m. The first cable provided a survey depth of 60 m; the second, ∼12 m. Four phases of the geyser's operation are distinguished on the difference geoelectric sections, constructed from the monitoring results: filling, outpouring, spouting, and steaming in the form of alternating positive and negative electric field anomalies. The channel to the geyser was found from the results of areal measurements. [ABSTRACT FROM AUTHOR]

Determining soil hydraulic properties is complex, posing ongoing challenges in managing subsurface and agricultural practices. Electrical resistivity tomography (ERT) is an appealing geophysical method to monitor the subsurface due to its non‐invasive, easy‐to‐apply and cost‐effective nature. However, obtaining geoelectrical tomograms from raw measurements requires the inversion of an ill‐posed problem, which causes smoothing of the actual structure. Furthermore, the spatial resolution is determined from the distances in the electrode placement, thus inherently upscaling the obtained structure. This study explores the applicability of physics‐informed neural networks (PINNs) for upscaling permeability and petrophysical relations and monitoring water dynamics at heterogeneous soils using time‐lapse geoelectrical data. High‐resolution numerical simulations mimicking water infiltration were used as benchmarks. Synthetic ERT surveys with electrode spacing 10 times larger than the numerical model resolution were conducted to provide 2D electrical tomograms. The tomograms were fed to a PINNs system to obtain the permeability, petrophysical relations, and water content maps. An additional PINNs system incorporating water content measurements was trained to examine measurement sensitivity. Results have shown that the PINNs system could produce reliable results regarding the upscaled permeability and petrophysical relations fields. Water dynamics at the subsurface was accurately predicted with an average error of ∼3%. Adding water content measurements to PINNs training improved the system outcomes, mainly at the ERT low sensitivity zones. The PINNs system reduced water saturation errors by more than 30% compared to the common practice of directly translating the geoelectrical tomograms to water saturations using known, homogeneous petrophysical relations. Key Points: Physics‐informed neural networks were applied for simultaneously upscaling heterogeneous soil physical propertiesTraining data relied on inverted 2D geoelectrical tomogramsThe PINNs system was able to reproduce the upscaled water saturation maps during an infiltration scenario [ABSTRACT FROM AUTHOR]

Although numerous recent studies have explored the relationship between permafrost degradation and rock slope failure, there is still a need for in‐depth investigations to develop relevant hazard assessment approaches. We investigate the predisposing, triggering and propagation processes of a rock avalanche (c. 225,000 m3) that occurred in Vallon d'Étache (France) on 18 June 2020, whose scar was coated by ice and water. Weather records and energy balance models show that the rock avalanche occurred right after the warmest spring and winter since at least 1985, but also right after the spring with the highest water supply anomaly (snowmelt and rainfall). Measured ground surface temperature and geoelectrical surveys reveal that relatively ice‐rich permafrost could exist in the NW face (release area) while it is inexistent below the SE face, contradicting certain permafrost maps. Heat transfer simulations suggest that the rock avalanche occurred during a transition from cold to warm permafrost conditions at failure depth (30 m), with a temperature increase of up to 0.6°C per decade since 2012 (when considering potential snow cover effect), and current temperature ranging between −3 and −1°C, depending on the applied model forcing. This warming certainly contributed to predispose slope to failure. In addition, the shift towards warm permafrost and water infiltration potentially enhancing permafrost degradation along fractures through heat advection or favouring the development of high hydrostatic pressures may have played as triggering factors. Finally, propagation simulations show that the rock avalanche involved several phases with different rheological properties due to the incorporation of snow and material segregation within the deposit. These new insights at various scales highlight the complexity of the triggering and propagation processes of rock slope failure occurring in high mountains, a significant part of which can be linked to snow effects on ground temperature, water supply and rheological properties. [ABSTRACT FROM AUTHOR]

In this work, electrical resistivity tomography was carried out together with physical hydrogeology techniques to evaluate the karst aquifer in the northwest region of the Yucatán Peninsula in a study area near the western edge of the Ring of Cenotes of the Chicxulub Crater. In addition, based on a systematic compilation of open-access data of water levels reported for the peninsular aquifer, maps of groundwater isolines and groundwater flows were generated using IDW interpolation, Empirical Bayesian Kriging, and the Flow Net method. From these results, a shallow aquifer is observed, with the presence of heterogeneities such as possible dissolution conduits and/or flooded caverns, approximately 20 m below ground level, formed by the dissolution processes of limestone rocks. On a regional scale, the geomorphological influence of the Ring of Cenotes on groundwater flows was observed. In general, the flow directions observed from these maps coincide with those conceptualized for this region of the peninsular aquifer. Nevertheless, some differences were observed depending on the interpolation method used. Our results contribute to hydrogeological studies carried out in the periphery of this ring, where the vulnerability of the aquifer to anthropogenic contamination has been highlighted due to the intrinsic features of the karst environment. [ABSTRACT FROM AUTHOR]

The diagnosis and monitoring of contaminated sites have become progressively critical. The effectiveness of electrical resistivity tomography (ERT) has been demonstrated in the assessment of contaminated sites, and its resolution can be significantly improved by array optimization. Gradient array involves the deployment of multiple electrodes in an array configuration to measure the variation in electrical potential across the subsurface, whereas there are some improved arrays which can often provide more accurate measurements. This study investigates the conventional gradient and improved Compare Resolution protocol to identify an abandoned quarry pit where pharmaceutical wastes were dumped. The acquired results were subsequently validated with borehole sampling. The results obtained from the gradient protocol revealed the presence of low-resistivity area. Nevertheless, it is difficult to define the range of the contamination plume area. The results from the optimized array illustrated that the maximum lateral contamination range in the vertical direction appears at a depth of 9 m. A portion of the contaminated area shown in the profile is confined by bedrock. Considering the high cost, only four locations are chosen for drilling to collect samples. The findings revealed that low resistivity corresponds to contamination of inorganic substances. The resistivity and drilling results further clarify that the site has a three-layer structure. The spatial variability of the contaminated site has been ascertained by the high-resolution ERT, and further identify four contaminant sources. This study proves the effectiveness of the ERT method to avoid the drawbacks of costly drilling in bedrock and accomplishes an efficient assessment of contamination. [ABSTRACT FROM AUTHOR]

The construction of dam is important for many reasons. Prior to construction, it is essential to assess the dam's base reservoir to identify any subsurface cavities. This study was conducted along nine electrical resistivity (ERT) profiles and eight induced polarization (IP) profiles, which are traditional ERT profiles, trending SW to NE direction in the reservoir part of the failed Chaq-Chaq dam NW of Sulaimaniyah city. The aim of this study was to delineate subsurface layers, underground features, determine the depth to bedrock, and investigate indications of the causes of collapse of the constructed Chaq-Chaq dam. The Res2Dinvx64 program used in the inversion method to obtain true 2D resistivity sections using a Schlumberger-Wenner array, which is highly sensitive to changes in resistivity both vertically and laterally. Based on the resistivity values, it was found that the area consists of three geological layers; the first layer consists of soil, while the second layer consists of rock fragments, the interface between them has disappeared because the first layer is thin, and the third layer is specified as consolidated and cohesive limestone of the Kometan Formation. The surface of the Kometan limestones is irregular due to weathering and faulting resulting from tectonic movements leading to the collapse of the area and later filled with sediments of recent deposition. The IP method was only used to distinguish clay and water. According to IP values, water is present in the subsurface of the study area. According to the ERT sections, a sinkhole with a depth range of (15-39 m) was encountered at the beginning of most of the profiles. The occurrence of subsurface sinkholes and cavities in the fractured limestone of the Kometan Formation, especially in the western part of the dam region, is considered to be a contributing factor to the collapse of the dam when it is filled with water and subjected to the water pressure. [ABSTRACT FROM AUTHOR]

The Bídnice hill near Litoměřice, Czech Republic, has been recognized as a volcanic structure during a survey for a new railway connection between Prague and Dresden, where after several campaigns of combined geophysical survey, it has been concluded, that Bídnice is actually a deeply eroded peanut-shaped maar-diatreme volcano forming a positive morphology. The reason for the higher resistance of the disintegrated rock in the diatreme fill against the erosion when compared to surrounding country rocks was the main question of our presented research. While other positive-morphology diatremes in the region are mostly associated with high-viscosity differentiated alkaline rocks (namely phonolites), the Bídnice diatreme comprises intrusions of basic rock (SiO2 ca 38 wt. %), classified as olivine nephelinite. From the geophysical survey of the internal structure, comprising magnetometry and electrical resistivity tomography, a spoon-like subsurface intrusions of the olivine nephelinite were found. A smaller outcrop of the intrusive system penetrating the diatreme provided a K-Ar age of 27.06 ± 0.57 Ma (Oligocene). The results of the geophysical survey were then used to create a 3D geological model to better understand and interpret the geological setting. A system of coherent sills, even with a rather low thickness in the case of low-viscosity (ultra)mafic rocks, may be responsible for the reinforcement of the diatreme leading in slower erosion, and therefore resulting in the significant positive topography of eroded maar-diatreme volcano. In addition, sub-horizontal intrusions provide more homogeneous reinforcement of the diatreme against erosion compared to subvertical dykes, those would be exposed by the selective erosion in the form of small ridges. [ABSTRACT FROM AUTHOR]

Parwan Gravity Dam is under construction stage in the Jhalawar district of Rajasthan, India. A thin sub-vertical surficial fracture trending N 75°W to S 75°E has been observed in the foundation area of the dam. Geophysical techniques such as electrical resistivity tomography (ERT), seismic refraction tomography (SRT), and multichannel analysis of surface waves (MASW) are utilized extensively in the field of civil engineering, exploration geophysics for the assessment and construction of large-scale infrastructures such as dams. These methods provide critical information about the subsurface conditions without the need of extensive drilling and excavation. The combination of electrical resistivity tomography (ERT), seismic refraction (SR), and multichannel analysis of surface waves (MASW) techniques with the different acquisition parameters have been used to image the extent of shallow subsurface geological structures. Various geophysical Surveys have been carried out along several profiles in the longitudinal direction and along the transverse direction to the fault axis. A total of 13 refraction and resistivity profiles were conducted of which 9 were transverse profiles and 4 were longitudinal profiles. A total of nine MASW profiles were conducted of which 8 are transverse profiles and 1 is a longitudinal profile. In this paper, the subsurface distribution of seismic wave velocity and electrical resistivity have been studied to identify any possible anomalous zone in bedrock and to detect the downward extension of surface fracture of brittle fault using the afore mentioned methods. The vertical and lateral extent of the surface fracture of the fault has been investigated by the analysis of these survey results. The analysis of the results indicates that a very tight and narrow fracture is present in the shallow subsurface. [ABSTRACT FROM AUTHOR]

This paper examines the theoretical foundations of electrical resistivity tomography (ERT) technology, followed by the finite element analysis method, for the positive problem and the linear back-projection (LBP) procedure for the inverse problem. The conductivity distribution image of the modeled concrete is then reconstructed, which includes one circular aggregate and the surrounding mortar. It is discovered that the conductivity obtained can be used to find the inclusive aggregate, mortar, and interfacial transition zone (ITZ). Natural aggregate and mortar have conductivities of 0.046 ms/cm and 0.115 ms/cm, respectively. Additionally, the conductivity of the ITZ, which is always regarded as the initial damage, is about 0.081 ms/cm. ERT is a cost-effective and readily available technique for determining the initial distribution of the aggregate and related ITZ. Therefore, ERT is a promising tool for determining inclusions and initial damage in concrete. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of removing 3D effects as one of the most challenging problems related to 2D electrical resistivity tomography (ERT) monitoring of embankment structures. When processing 2D ERT monitoring data measured along linear profiles, it is fundamental to estimate and correct the distortions introduced by the non-uniform 3D geometry of the embankment. Here, I adopt an iterative 3D correction plus 2D inversion procedure to correct the 3D effects and I test the validity of the proposed algorithm using both synthetic and real data. The modelled embankment is inspired by a critical section of the Parma River levee in Colorno (PR), Italy, where a permanent ERT monitoring system has been in operation since November 2018. For each model of the embankment, reference synthetic data were produced in Res2dmod and Res3dmod for the corresponding 2D and 3D models. Using the reference synthetic data, reference 3D effects were calculated to be compared with 3D effects estimated by the proposed algorithm at each iteration. The results of the synthetic tests showed that even in the absence of a priori information, the proposed algorithm for correcting 3D effects converges rapidly to ideal corrections. Having validated the proposed algorithm through synthetic tests, the method was applied to the ERT monitoring data in the study site to remove 3D effects. Two real datasets from the study site, taken after dry and rainy periods, are discussed here. The results showed that 3D effects cause about ±50% changes in the inverted resistivity images for both periods. This is a critical artifact considering that the final objective of ERT monitoring data for such studies is to produce water content maps to be integrated in alarm systems for hydrogeological risk mitigation. The proposed algorithm to remove 3D effects is thus a rapid and validated solution to satisfy near-real-time data processing and to produce reliable results. [ABSTRACT FROM AUTHOR]

• Electrical resistivity tomography, a new approach for detecting smouldering fires. • A region of R / R o ≥ 50 % corresponds to smouldering hotspots. • Increase in resistivity at smouldering hotspots is attributed to drop in moisture. • ERT can work well for material having moisture content as high as 50%. • ERT technology can be applied for silos and pile storage of organic material. Incidents of waste and biofuel fires are common at all stages of the waste recycling chain and have grave implications for business, employees, firefighters, society, and environment. An early detection of waste and biofuel fires in the smouldering stage could save precious lives, resources, and our environment. Existing fire detection methodologies e.g. handheld temperature sensors, IR cameras, gas sensors, and video and satellite-based monitoring techniques have inherent limitations to efficiently detect smouldering fires. An attempt was made to explore the potential of electrical resistivity tomography (ERT) as an alternate tool to address the problem. In the experiments an externally powered resistive wire was employed to initiate the smouldering fire inside the test material (wood pellets, wood shavings, wood fines). Time series of ERT that followed the initiation and development of smouldering were recorded using an automated monitoring instrument setup. The actual geometry of the experimental sample container and electrode setup was integrated in the 3D finite element method (FEM) model grid to perform inverse numerical modelling (inversion) and to develop resistivity tomographic images. The study shows a sharp increase in ratio of resistivity (R / R o ≥ 50 %) in the test material in the region of smouldering hotspot and demonstrates the potential use of ERT technique for the detection of smouldering hotspots in silos and pile storage of organic material such as wood-based fuels, wood waste, coal, municipal solid waste (MSW), recyclables etc. More research is however required for enabling the use of this technique at the practical scale for different storage conditions. [ABSTRACT FROM AUTHOR]

Underground galleries possess random subsidence threats if they are not treated well. Threats even become multifold when these galleries are located somewhere in the vicinity of the railway tracks. So, checking the stable ground formation or the health of the subsurface formation near railway tracks and mapping the galleries are very important tasks for the sake of the environment, economy and lives. Galleries under the present study are associated with the coal seam-X and seam-XA of the Jogidih Colliery of Jharia Coalfield. Seven electrical resistivity tomography (ERT) profiles and magnetic surveys were performed at a side of the railway track to characterize the subsurface formation near railway tracks and to detect the gallery and its extension. Both ERT and magnetic data analysis suggest the presence of some galleries at a certain distance from the railway tracks. Moreover, combined analysis of ERT and magnetic data suggests that ground within ~20 m from the railway tracks is found to be stable with homogeneous compact formation. [ABSTRACT FROM AUTHOR]

Rock quality designation (RQD) is a standard technique in mining and geotechnical investigation for quantifying the quality and degree of jointing of the rock mass. However, the need for expeditious and inexpensive geotechnical site characterization is the prime motivation for modifying RQD. This research work integrates 2D Electrical Resistivity Tomography (2D ERT) and Unmanned Aerial Vehicle (UAV) conducted at Site 1 and Site 2. The UAV survey was performed to calculate RQD on the rock surface using volumetric Joint Counts (Jv) at Sites 1 and 2. A 2D ERT survey was conducted to obtain the corresponding subsurface resistivity values. Using k-nearest neighbours (k-NN), resistivity values were assigned to various RQD indices such as very poor rocks (<350 Xm), poor rock (350-1150 Xm), fair rock (1150-1850 Xm), good rock (1850-2500 Xm) and >2500 Xm excellent rock. Based on the established correlation of RQD and resistivity, the subsurface rock mass quality at Site 1 was predominantly good and excellent rock, while at Site 2, poor rock was significantly reported. This research concluded that rock mass characterization using RQD is more rapid and inexpensive than the direct or indirect calculation of RQD. The combined 2D ERT and UAV deployed in this research study provide an environmentally non-destructive approach for slope stability assessment. [ABSTRACT FROM AUTHOR]

Electrical resistivity tomography (ERT) is a potential-based method for detecting internal erosion in the core of embankment dams using the electrodes installed outside. This study aims at evaluating the practical capability of ERT monitoring for detecting internal defects in embankment dams. A test embankment dam with in-built well-defined defects was built in Älvkarleby, Sweden, to assess different monitoring systems including ERT and the defect locations were unknown to the monitoring teams. Between 7500 and 14,000 ERT data points were acquired daily, which were used to create the distribution of electrical resistivity models of the dam using 3D time-lapse inversion. The inversion models revealed a layered resistivity structure in the core that might be related to variations in water content or unintentional variations in material properties. Several anomalous zones that were not associated with the defects were detected, which might be caused by unintentional variations in material properties, temperature, water content, or other installations. The results located two out of five defects in the core, horizontal and vertical crushed rock zones, with a slight location shift for the horizontal zone. The concrete block defect in the core was indicated, although not as distinctly and with a lateral shift. The two remaining defects in the core, a crushed rock zone at the abutment and a wooden block and a crushed rock zone in the filter, were not discovered. The results cannot be used to fully evaluate the capability of ERT in detecting internal erosion under typical Swedish conditions due to limited seepage associated with the defects. Furthermore, scale effects need to be considered for larger dams. [ABSTRACT FROM AUTHOR]

Electrical resistivity tomography (ERT) has turned out to be one of the most applied and user-friendly geophysical methods in geotechnical and geoenvironmental research. ERT is an emerging technology that is becoming popular nowadays for investigating subsurface conditions. Multiple attributes of the technology using various electrode configurations significantly reduce measurement time and are suitable for applications even in hardly accessible mountain areas. It is a noninvasive test for subsurface characterization and a very sensitive method used to determine geophysical properties, i.e., structural integrity, water content, fluid composition, etc. This paper aimed to elucidate the ERT technique's main features and applications in geotechnical and geoenvironmental engineering through four case studies. The first case study investigated the possible flow paths and areas of moisture accumulation after leachate recirculation in a bioreactor landfill. The second case study attempted to determine the moisture variation along highway pavement. The third case study explored the slope failure investigation by ERT. The fourth case study demonstrated the efficiency of the ERT method in the landfill evapotranspiration (ET) cover to investigate moisture variation on a broader scale and performance monitoring. In all of the four cases, ERT exhibited promising performance. [ABSTRACT FROM AUTHOR]

After degradation of permafrost, the periodic freezing and melting in thawing areas will seriously damage the stability of oil pipelines. The 2D and 3D electrical resistivity tomography (ERT) are used respectively to detect the distribution and development status of permafrost in the buried area of crude oil pipelines. To further study the effectiveness of different exploration modes of ERT and resistivity response characteristics of permafrost, firstly, three models for unthawed, half-thawed and through-thawed permafrost are established in the space beneath the pipeline, and Earthlmager 2D and Earthlmager 3D software are applied for the forward modeling of finite element method and smoothness constrained least-squares inversion. On the basis of numerical simulation results, then, the resistivity response characteristics and differences of inversion results between the three models are compared and the exploration effects of 2D and 3D ERT are summarized. Finally, the results are further verified by exploration practice. The results show that the ERT is an effective method in permafrost survey. The detection effect of 2D ERT on the unthawed and through-thawed permafrost is better than on half-thawed permafrost. The data collected by 3D ERT is more abundant, the display of object morphology is more intuitive and precise, and the inversion results are closer to the theoretical model, which is suitable for permafrost of various melting states. The field examples further verify the numerical simulation results, and the application of 3D ERT also provides a new idea in the field of permafrost fine detection. [ABSTRACT FROM AUTHOR]

Quantitative estimates of hydrological state variables using electrical or electromagnetic geophysical methods are systematically biased by overlooked heterogeneity below the spatial scale resolved by the method. We generalize the high‐salinity asymptotic limit of electrical conduction in porous media at the continuous (e.g., Darcy) scale, by introducing a new petrophysical parameter, the mixing factor M, which accounts for the effect of fluid conductivity heterogeneity on the equivalent electrical conductivity tensor; it is expressed in terms of the volume‐average of the product of mean‐removed fluid conductivity and electric fields. We investigate the behavior of M for static and evolving fluid conductivity scenarios. Considering 2‐D ergodic log‐normal random fields of fluid conductivity, we demonstrate, in absence of surface conductivity, that observing the components of the M‐tensor allows univocally determining the variance and anisotropy of the field. Further, time‐series of the M‐tensor under diffusion‐limited mixing allows distinguishing between different characteristic temporal scales of diffusion, which are directly related to the initial integral scales of the salinity field. Under advective‐diffusive transport and for a pulse injection, the time‐series of M have a strong dependence on the Péclet number. Since M is defined in the absence of surface conductivity, we investigate how to correct measurements for surface conductivity effects. The parameter M provides conceptual understanding about the impact of saline heterogeneity on electrical measurements. Further work will investigate how it can be incorporated into hydrogeophysical inverse formulations and interpretative frameworks. Plain Language Summary: Electrical and electromagnetic geophysical methods provide information about the spatio‐temporal distribution of average electrical conductivity of porous media. This property is affected by the transport of electrically conductive solutes, which unfolds over a wide range of spatial scales. However, when translating electrical data into solute concentration, almost all studies to date have ignored solute heterogeneity below the averaging volume inherent to geophysical measurements or modeling, leading to unphysical results. We introduce the mixing factor M, an electrical parameter that links small‐scale solute heterogeneity and average electrical conductivity, via a closed‐form expression depending on the small‐scale features of electric and solute concentration fields. We show that observation of the M‐tensor allows recovering the variance and anisotropy of the solute field in a time‐static setting. For diffusion‐limited transport, the time‐series of M help distinguishing the initial length scales of the fields, whereas for advective‐diffusive transport, these data help distinguishing the Peclet number. The presented framework helps to decode information about solute heterogeneity that is contained in geoelectrical measurements, while also avoid making biased hydrological estimates. Future venues of research will investigate how to incorporate M in available (hydro)geophysical modeling workflows. Key Points: Petrophysical parameter generalizing the high‐salinity limit of electrical conduction for heterogeneous fluid conductivity in porous mediaFormal expression for M provides framework to interpret impact of small‐scale fluid conductivity heterogeneity on electrical measurementsThe mixing factor M depends on geostatistical properties of solute concentration fields and thus on transport characteristics [ABSTRACT FROM AUTHOR]

Geothermal energy systems, such as heat pumps relying on aquifers, use renewable sources of energy that are accessible in urban areas. It is necessary to characterize the subsurface hydraulic properties prior to the installation of such systems. In this context, a heat‐tracing experiment is a typical field test that can help with the characterization of the subsurface. During a heat‐tracing experiment, monitoring with downhole temperature sensors, water‐level pressure transducers and electrical resistivity tomography (ERT) can be used to help characterize the hydrogeological properties. Previous monitoring tools have shortcomings, such as low‐resolution data and over‐smoothing; thus, they fail to reproduce the heterogeneity of hydrogeological properties. Ensemble Kalman filter (EnKF) is a promising tool that can overcome the over‐smoothing problem to replicate the hydrogeological property heterogeneity. In this work, we proposed a new procedure to assimilate time‐lapse cross‐borehole ERT data into a numerical model of groundwater flow and heat transfer, where the groundwater is extracted and heated water is reinjected into an unconfined sandy‐gravel aquifer. The finite element model (FEFLOW 7.3) of groundwater flow and heat transfer is integrated with petrophysical relationship and electrical forward modelling (ResIPy) to estimate cross‐borehole ERT measurements. Then, the estimated apparent resistivity is assimilated to update the hydraulic conductivity model using EnKF. The results of the application of the proposed approach to an experimental site located in Quebec City (Canada) demonstrate that the heterogeneity of K is correctly reproduced as the updated K model is reasonably consistent with the lithological log. In addition, the proposed approach was able to replicate the cross‐borehole ERT field and temperature measurements. The comparison between prior and posterior distribution of K with slug test results shows that the EnKF made the final (assimilated) distribution of K move towards K values inferred with slug tests. [ABSTRACT FROM AUTHOR]

Access to groundwater for use in semi-arid regions is costly due to consistent failures in borehole drilling programs attributable to either a survey not carried out before drilling or incorrectly interpreted geophysical results. Thus, this study aims at delineating the geometry of the shallow weathered crystalline basement aquifer of the Vea catchment, northern Ghana, to aid in the assessment of its groundwater storage potential. Integrated electromagnetic and electrical resistivity surveys within the study area and borehole logs were integrated to delineate the aquifer zones of the study area. The study results revealed the interface between the bedrock and the overlying weathered subsurface as the most transmissive aquifer zone, with the saturated weathered subsurface making up 90% of the total volume of aquifers in the subsurface. The aquifer material in this zone predominantly includes varying proportions of sandy clay and weathered granite, with apparent resistivity ranging from 100 to 500 Ωm in the subsurface. Also, the results indicated that the weathered bedrock interface is irregular, and the water strike zone of the shallow aquifer in the weathered zone mimics the water table and the landscape of the area. Therefore, the study findings could improve the success rate of borehole drilling within the catchment and similar geological terrains. [ABSTRACT FROM AUTHOR]

Electrical resistivity tomography (ERT) has turned out to be one of the most applied and user-friendly geophysical methods in geotechnical and geoenvironmental research. ERT is an emerging technology that is becoming popular nowadays for investigating subsurface conditions. Multiple attributes of the technology using various electrode configurations significantly reduce measurement time and are suitable for applications even in hardly accessible mountain areas. It is a noninvasive test for subsurface characterization and a very sensitive method used to determine geophysical properties, i.e., structural integrity, water content, fluid composition, etc. This paper aimed to elucidate the ERT technique’s main features and applications in geotechnical and geoenvironmental engineering through four case studies. The first case study investigated the possible flow paths and areas of moisture accumulation after leachate recirculation in a bioreactor landfill. The second case study attempted to determine the moisture variation along highway pavement. The third case study explored the slope failure investigation by ERT. The fourth case study demonstrated the efficiency of the ERT method in the landfill evapotranspiration (ET) cover to investigate moisture variation on a broader scale and performance monitoring. In all of the four cases, ERT exhibited promising performance.

Finding out the specific location of the fault structure is of great significance for the engineering site selection and stability evaluation. Electrical resistivity tomography and acoustic logging are geophysical methods widely used in detecting fracture structures. Although electrical resistivity tomography is sensitive to low resistance bodies and has a large detection range, it is difficult to accurately delineate the boundary position of geological bodies because of its limited resolution. Acoustic logging can identify strata accurately, but its lateral detection range is limited. This study combined the advantages of the two methods in fault structure detection to improve the precision of geological body delineation. Firstly, the correlation between the resistivity of rock before and after fracture and the change of acoustic wave velocity was proved by physical property experiments. Then the case analysis of the resistivity and acoustic wave velocity characteristics of the fault structure and their combined application in the detection process was conducted. Finally, the depth correction of the inversion result of the electrical resistivity tomography was carried out using the acoustic logging data; and the three-dimensional distribution position of the fault structure in the underground space was obtained. Theresults show that the resistivity and acoustic wave velocity of the rock after fracture are lower than those before fracture. The fracture zone of the fault structure exists in the inversion section of the electrical resistivity tomography with a low resistivity anomaly region. On the wave velocity curve, the wave velocity value in the fracture zone decreases significantly. The combined detection mode of the two methods could provide a guidance for the delineation of the specific location of the fracture structure. The drilling results also verified that the inversion results of the electrical resistivity tomography corrected by acoustic logging data are more consistent with the actual geological conditions than those without correction.

Abstract The Ningdong coalfield has played a pivotal role in advancing local economic development and meeting national energy. Nevertheless, mining operations have engendered ecological challenges encompassing subterranean water depletion, land desertification, and ground subsidence, primarily stemming from the disruption of coal seam roof strata. Consequently, the local ecosystem has incurred substantial harm. Water-preserved coal mining presently constitutes the pivotal technology in mitigating this problem. The primary challenge of this technique lies in identifying critical aquifer layers and understanding the heights of water-conducting fracture zones. To obtain a precise comprehension of the seepage patterns within the upper coal seam aquifer during mining, delineate the extent of water-conducting fracture zones, non-invasive geophysical techniques such as time-lapse electrical resistivity tomography (TL-ERT), magnetic resonance sounding (MRS), and spontaneous potential (SP) have been employed to monitor alterations within the shallow coalfield’s aquifer throughout the mining process in the Ningdong coalfield. By conducting meticulous examinations of fluctuations in resistivity, moisture content, and self-potential within the superjacent strata during coal seam extraction, the predominant underground water infiltration strata were ascertained, concurrently enabling the estimation of the development elevation of water-conducting fracture zones. This outcome furnishes a geophysical underpinning for endeavors concerning local water-preserved coal mining and ecological rehabilitation.

[Objective] The subsurface freshwater lens of coral islands is an important resource necessary to maintain the production and living of islanders and ecological conservation. Accurately identifying the morphology of subsurface freshwater lenses on coral islands and revealing the mechanism of subsurface freshwater recharge are important bases for the assessment of groundwater resources on reefs, and are crucial for improving the management of groundwater resources on coral islands. [Methods] Taking Dong Island as the research object, this study combined with hydrogeological survey and high-density resistivity method to identify the distribution of freshwater lenses near sand barriers, and describe the brackish water interface. [Results] The results show that the freshwater lenses on the northwestern and southern parts of the island were relatively developed, and the thickness of the freshwater lenses below the sand dikes was 3-7 m. In the southeast of the island, there were also freshwater lenses developed in the higher terrain, but the thickness was thinner than in the sand barriers, and there was even no fresh groundwater in some local areas. [Conclusion] The development of freshwater lenses in Dong Island is associated with the distribution of topography and vegetation, and the water consumption by evapotranspiration of vegetation is the main factor that causes the thinner freshwater lenses in the low-lying land on the island.

Instability of slopes, embankments, and cuttings on the railway network is increasingly prevalent globally. Monitoring vulnerable infrastructure aids in geotechnical asset management, and improvements to transport safety and efficiency. Here, we examine the use of a novel, near-real-time Electrical Resistivity Tomography (ERT) monitoring system for assessing the stability of a railway cutting in Leicestershire, United Kingdom. In 2015, an ERT monitoring system was installed across a relict landslide (grassed) and an area of more stable ground on either side (wooded), to monitor changes in electrical resistivity through time and space, and to assess the influence of different types of vegetation on the stability of transportation infrastructure. Two years of 4-Dimensional ERT monitoring results are presented here, and petrophysical relationships developed in the laboratory are applied to calibrate the resistivity models in order to provide an insight into hydrogeological pathways within a railway cutting. The influence of vegetation type on subsurface moisture pathways and on slope stability is also assessed – here we find that seasonal subsurface changes in moisture content and soil suction are exacerbated by the presence of trees (wooded area). This results in shrink-swell behaviour of the clays comprising the railway cutting, resulting in fissuring and a reduction in shear strength, leading to instability. As such, it is proposed that on slopes comprised of expansive soils, grassed slopes are beneficial for stability. Insights into the use of 4-D ERT for monitoring railway infrastructure gained from this study may be applied to the monitoring of critical geotechnical assets elsewhere.

This paper presents the design, implementation, and evaluation of VR-EX, a combination of a virtual field trip and a serious game in immersive virtual reality. The application's purpose is the communication of research conducted in the Mont Terri underground research laboratory in Switzerland. VR-EX enables users to actively attend electrical resistivity tomography measurements within a geological experiment, from planning to execution to analysis of the results, and in this way implements an active and playful learning approach. The work conducted in underground research laboratories has a high relevance for society as it contributes to research on the final disposal of nuclear waste. Therefore, the active communication of research methodology and results is crucial to increase understanding of scientific processes and boost interest. VR-EX was evaluated in a user study with 35 participants to measure its overall quality and its effectiveness of the knowledge transfer. Taking the evaluation's qualitative results into account, the application was improved in an iterative process. Overall, the results prove the good quality of the application and its high effectiveness in terms of knowledge transfer. The reported high engagement, joy, and immersion indicate the benefits of employing immersive virtual reality for vivid science communication. [ABSTRACT FROM AUTHOR]

We applied an interdisciplinary approach to analyze the late Quaternary activity of the Sava Fault in the Slovenian Southern Alps. The Sava Fault is an active strike-slip fault, and part of the Periadriatic Fault System that accommodated the convergence of Adria and Europe. It is one of the longest faults in the Southern Alps. Using high-resolution digital elevation models from lidar and photogrammetric surveys, we were able to overcome the challenges of assessing fault activity in a region with intense surface processes, dense vegetation, and relatively low fault slip rates. By integrating remote sensing analysis, geomorphological mapping, structural geological investigations, and near-surface geophysics (electrical resistivity tomography and ground penetrating radar), we were able to find subtle geomorphological indicators, detect near-surface deformation, and show distributed surface deformation and a complex fault pattern. Using optically stimulated luminescence dating, we tentatively estimated a slip rate of 1.8 ± 0.4 mm/a for the last 27 ka, which exceeds previous estimates and suggests temporal variability in fault behavior. Our study highlights the importance of modern high-resolution remote sensing techniques and interdisciplinary approaches in detecting tectonic deformation in relatively low-strain rate environments with intense surface processes. We show that slip rates can vary significantly depending on the studied time window. This is a critical piece of information since slip rates are a key input parameter for seismic hazard studies. [ABSTRACT FROM AUTHOR]

In Chad, hard-rock aquifers are the main source of drinking water for the population located on basement areas. In these basement aquifers, and in particular those of the Guéra region, water drilling failure rates remain high despite research on one- and two-dimensional electrical resistivity techniques and lineaments as a means to improve access to the resource, mainly because these techniques are only used on an observational and structural basis to locate fractures. This study combines electrical resistivity tomography (ERT) with geology, hydrogeology and geomorphology, in order to characterise the structure and geometry of the aquifer system, assess borehole productivity and determine the factors controlling it. After validating the large dataset and its representativeness, 315 high- and low-yield wells, of which 41 have complete geophysical datasets, were selected. This large dataset allows a multi-parameter approach to (1) better characterise each facies according to its electrical resistivity and (2) clearly identify the main formations constituting the local conceptual hydrogeological model. The most suitable areas for productive boreholes are characterised by the presence of an overburden of <20 m depth, well-developed weathered and fractured horizons of granites and biotite granites (preferably) containing little or no clay, and a nearby drainage network. The most substantial flow rates are found in the first 30 m of the fissured horizon, below the base of the alterites. The experience gained from the present study will guide future analysis of ERT sections in order to reduce the probability of drilling dry wells. [ABSTRACT FROM AUTHOR]

Copyright of Revue Française de Géotechnique is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The growth of the geothermal industry demands the constant search of techniques with the aim of reducing exploration efforts whilst minimizing subsurface uncertainty. The exploration of geothermal resources is fundamental from the exploitation point of view, especially in those regions where this energy is not as widespread as the rest of renewable sources. This research shows how geoelectrical methods can contribute to the investigation and characterization of medium–low enthalpy geothermal resources until about 800 m of depth. A 2000 m long electrical-resistivity tomography profile was performed in a region of Southern Spain with previous evidence of moderate geothermal potential. Results of this geophysical campaign (together with a preliminary geological characterization) allowed for the obtainment of a 2D profile and a pseudo-3D model with extensive information about the subsoil in terms of geological composition and formations. The interpretation of geophysical results denotes the existence of a potential formation constituted by carbonate materials with thickness greater than 300 m, crossing different fractures. Once the ideal location for the geothermal exploitation is defined, the research evaluates the contribution of the possible energy source, deducing that the energy extraction in the potential fracturing area would be double that of the one in the vicinity of the site. [ABSTRACT FROM AUTHOR]

Assessment of subsoil corrosivity was conducted within the University of Cross River State, Calabar, Calabar Campus, Southern Nigeria. The study employed electrical resistivity methods. The results from vertical electrical sounding revealed that the topsoil of VES1 and VES3 was slightly corrosive at depths of 2.20m and 0.70m while that of VES2 and VES4 were practically non-corrosive at depths 0.60m and 1.00m. The electrical resistivity tomography across the VES2 and VES4 showed a low resistivity at horizontal distances between 5.0m and 10.0m at a depth of 3.75m, indicating very strongly corrosive. Other areas of the profile with resistivity from 19.0 Ώm to 38.0 Ώm at a depth of between 6.38m and 19.8m indicate moderately corrosive and 75.0 Ώm which is slightly corrosive. A resistivity of 148.0Ώm to >580Ώm at the top layer indicates practically non-corrosive at depths 6.38m and 19.4m. Hence, metallic pipes should be buried at depth 3.0m. [ABSTRACT FROM AUTHOR]

Accurate characterization and monitoring strategies are essential for designing and implementing remedial programs for sites polluted with dense non-aqueous phase liquids (DNAPLs). Electrical resistivity tomography (ERT) is a widely used geophysical technique for mapping subsurface features and processes of interest, and exhibits desirable characteristics for DNAPL sites due to its ability to gather large volumes of continuous subsurface information in a non-invasive, cost-effective and time-efficient manner. However, ERT measured only from the surface suffers from poor imaging quality with depth. Enhanced ERT imaging can be obtained via electrodes deployed on the surface and within horizontal boreholes, but so far it has only been investigated for 2-D imaging. This study evaluates the potential of 3-D surface-to-horizontal borehole (S2HB) ERT configurations for imaging 3-D DNAPL source zones. Laboratory tank experiments were first conducted with a 3-D S2HB ERT configuration, which consisted of a surface grid and a single borehole line of electrodes, being used to monitor DNAPL migration within porous media. Results demonstrate that 3-D S2HB ERT with a single borehole provides improved sensitivity at depth, and therefore enhanced imaging compared to conventional 3-D surface ERT. Further tank experiments were performed to assess the performance of single borehole S2HB ERT when (i) the distance between surface and borehole is increased, and (ii) additional horizontal boreholes are included. The S2HB ERT with a single borehole significantly outperforms surface ERT at larger depths, and performs comparably to S2HB ERT using multiple boreholes. This study suggests that 3-D S2HB ERT with a single borehole can provide the enhanced imaging ability needed to map DNAPLs, while also being relatively practical for implementation at field sites. [ABSTRACT FROM AUTHOR]

The Ningdong coalfield has played a pivotal role in advancing local economic development and meeting national energy. Nevertheless, mining operations have engendered ecological challenges encompassing subterranean water depletion, land desertification, and ground subsidence, primarily stemming from the disruption of coal seam roof strata. Consequently, the local ecosystem has incurred substantial harm. Water-preserved coal mining presently constitutes the pivotal technology in mitigating this problem. The primary challenge of this technique lies in identifying critical aquifer layers and understanding the heights of water-conducting fracture zones. To obtain a precise comprehension of the seepage patterns within the upper coal seam aquifer during mining, delineate the extent of water-conducting fracture zones, non-invasive geophysical techniques such as time-lapse electrical resistivity tomography (TL-ERT), magnetic resonance sounding (MRS), and spontaneous potential (SP) have been employed to monitor alterations within the shallow coalfield's aquifer throughout the mining process in the Ningdong coalfield. By conducting meticulous examinations of fluctuations in resistivity, moisture content, and self-potential within the superjacent strata during coal seam extraction, the predominant underground water infiltration strata were ascertained, concurrently enabling the estimation of the development elevation of water-conducting fracture zones. This outcome furnishes a geophysical underpinning for endeavors concerning local water-preserved coal mining and ecological rehabilitation. [ABSTRACT FROM AUTHOR]

The direction of drilling wells in the plateau slope area is toward finding local favorable water-rich blocks, which are relative groundwater accumulation areas under the control of structure, lithology, and landform. These areas often have obvious geological boundary conditions (such as the presence of a water resisting layer in the vertical direction, the development of a fault fracture zone in the plane), and their corresponding physical boundary often has a relatively low or high resistivity to the surrounding rock. In this paper, the comprehensive geophysical method is used to study the application of water prospecting in the plateau slope of Shuangnuo village, Fuyuan, Yunnan Province. First, according to the hydrogeological conditions (the development of a fault fracture zone and clastic rock is unknown), the plane distribution range and vertical development of the low-resistivity abnormal fault fracture zone are determined using the electrical resistivity tomography (less than 100 m) and audio magnetotelluric methods (100–500 m). Vertically, the development depth and thickness of the clastic rock aquifuge (P1l) are determined using the audio frequency magnetotelluric method, which provides a basis for the maximum depth of the borehole layout. The combination of the electrical resistivity tomography and audio frequency magnetotelluric methods can delineate the favorable water-rich block in the study area well and verify that the study area has the prerequisite to become a water prospecting target. To determine the best location of the borehole layout, a combination of the composite profiling, microtremor horizontal-to-vertical spectral ratio (HVSR), apparent resistivity sounding, and K-reflection coefficient methods are carried out in the favorable water-rich block, which delineated by the electrical resistivity tomography and audio frequency magnetotelluric methods. The optimal borehole layout location is determined through the synchronous low resistivity anomaly of the composite profiling method, and the synchronous low resistivity anomaly is determined as a karst fracture zone (qualitative determination) in combination with the HVSR high-value anomaly of the microtremor method. The development depth of the karst fracture zone is finally determined by using the apparent resistivity sounding and K curves. This study reveals that the depth of the drilled hole is 243.5 m, and the water inflow is 144.3 m3/ day, successfully solving the serious water shortage problem in the local area. The case study results show that the combination of geophysical prospecting methods, namely, the electrical resistivity tomography, audio frequency magnetotelluric, composite profiling, microtremor, apparent resistivity sounding, and k-reflection coefficient methods, is effective for water exploration in the plateau slope zone. [ABSTRACT FROM AUTHOR]

The escarpments of sub-horizontally deposited rocks represent regional centres of geomorphological activity whose evolution is controlled by the occurrence of different types of slope processes. Surprisingly, historical landslide activity on escarpments of Cretaceous rocks has not yet been studied in detail at the regional level using precise absolute dating methods. In this study, dendrogeomorphic methods including sparse dating with seasonal accuracy were used to determine the activity of flow-like landslides that model the eastern margin of the Bohemian Cretaceous Basin. Geophysical ERT (electrical resistivity tomography) measurements and grain size analysis of the landslide material revealed high saturation of the landslide body with groundwater and a high content of fine-grained fraction, which potentially slows down the infiltration of water into the landslide body, thus moving mainly in its near-surface part. Dendrogeomorphic dating (of 177 Picea abies (L.) Karst. individuals) revealed 7 years of landslide activity in the five landslides studied. The dated movements appear to have a low-magnitude character as indicated by the structure, intensity and duration of the dated growth disturbances. In addition, the dated movements have the character of secondary post-failure movements within up to three generations of older landslide bodies. Dating with seasonal accuracy specified their occurrence to the period July to August. This study represents the first use of dendrogeomorphic methods to characterise landslide movements in a Cretaceous escarpment setting, providing a new perspective on this globally widespread phenomenon. [ABSTRACT FROM AUTHOR]