Electrical Resistivity Tomography Method Research Articles

Detection of subsurface cavities in the structurally bounded Labe prefecture area, Republic of Guinea using two-dimensional electrical resistivity tomography (ERT)

ABSTRACT 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.

Electrical Resistivity Tomography Investigation of Permafrost Conditions in a Thermokarst Site in Fairbanks, Alaska

<abstract> <p>The degradation of permafrost poses severe environmental threats to communities in cold regions. As near-surface permafrost warms, extensive topographic variability is prevalent in the Arctic and Sub-Arctic communities. Geologic hazards such as thermokarst are formed due to varying rates of permafrost degradation, resulting in ground subsidence. This gradual subsidence or abrupt collapse of the earth causes a danger to existing infrastructure and the economic activities of communities in cold regions. Understanding the causes of thermokarst development and its dynamics requires imaging its underground morpho-structures and characterizing the surface and subsurface controls. In this study, we conducted a two-dimensional (2D) electrical resistivity tomography (ERT) survey to characterize the permafrost conditions in a thermokarst prone site located in Fairbanks, Alaska. To increase the reliability in the interpretability of the ERT data, borehole data and the depth-of-investigation (DOI) methods were applied. By using the 2D and three-dimensional (3D) ERT methods, we gained valuable information on the spatial variability of transient processes, such as the movement of freezing and thawing fronts. Resistivity imaging across the site exhibited distinct variations in permafrost conditions, with both low and high resistive anomalies observed along the transects. These anomalies, representing taliks and ice wedges, were characterized by resistivity values ranging from 50 Ωm and above 700 Ωm, respectively. The results from this study showed the effectiveness of ERT to characterize permafrost conditions and thermokarst subsurface morpho-structures. The insights gained from this research contribute to a better understanding of the causes and dynamics of thermokarst, which can be instrumental for engineers in developing feasible remedial measures.</p> </abstract>

Landslide assessment through integrated geoelectrical and seismic methods: A case study in Thungsong site, southern Thailand

Many landslides can cause significant damage to infrastructure, property, and human life. To study landslide structure and processes, geophysical techniques are most productive when employed in combination with other survey and monitoring tools, such as intrusive sampling. Here, the integration of electrical resistivity tomography (ERT) and seismic refraction tomography (SRT) methods is used to assess landslides in Thungsong district, Nakhon Si Thammarat, the south of Thailand, where is a hilly and seasons of prolonged rainfall region. The 2D cross-plot analysis of P-wave velocity and resistivity values obtained by these two methods is introduced to identify potential landslide-prone zones in this region. The results of the 2D cross-plot model reveal detailed image of the subsurface conditions, highlighting areas of low P-wave velocity (lower than 600 m/s) and low resistivity (lower than 600 Ωm). These areas are indicative of weak zone and are potential to be sliding materials. Moreover, an intrusive sampling data from boreholes is also used for the calibration and validation geophysical data with geological data. This can improve the accuracy of landslide assessment and develop effective mitigation strategies to reduce the risk of landslides in this area. In addition of the 2D cross-plot, the volume of sliding material is also determined from the difference of the surface and slipping plane elevations. The volume calculation of sliding material is roughly 33447.76 m3. This approach provides a preliminary tool for landslide studies and monitoring landslides in this region, thus enabling an improved understanding of slope failure processes in this context, and the basis of a landslide mitigation strategy in the future.

Using electrical resistivity tomography method to investigate fresh groundwater lenses on Dong Island, China

Using electrical resistivity tomography method to investigate fresh groundwater lenses on Dong Island, China

Two-Dimensional Resistivity Modeling of Seawater Intrusion Along the West Flood Canal, Semarang

The northern coastal area of Semarang City has significant problems with a decrease in groundwater quality due to seawater intrusion. Increasing groundwater extraction and subsidence due to the city growth worsen the condition. It is necessary to collect information on the contaminated location to develop a strategy to decrease the spreading of seawater intrusion. This study aims to identify the presence of seawater intrusion zones in groundwater and estimate the spread distance of seawater intrusion to the land. We applied the electrical resistivity tomography method to obtain the image of the subsurface. A geo-electric survey with a dipole-dipole multi-electrode configuration was completed along the West Flood Canal. The subsurface model result indicated that the identified seawater intrusion zone is associated with a low resistivity value of less than 3 Ohm.m. The zone is about 0 - 70 meters deep near the coast and is thinning to about 2600 meters to the south. The result confirms that seawater has penetrated long distances to the land.

Time-Lapse Geophysical Measurements for Monitoring Coastal Groundwater Dynamics in an Unconfined Aquifer.

The coastal zone, which is the interface between land and sea, is hydrodynamically very active due to the complex interactions of various hydrological controls and variable-density fluids. These forces vary over time, resulting in a state of dynamic equilibrium in the system. The major hydrological processes in coastal aquifer systems are salt water intrusion and submarine groundwater discharge, which are interdependent. Monitoring these complex processes is crucial for sustainable coastal zone management but poses a significant research challenge. In this study, we demonstrate the effectiveness of non-invasive geophysical techniques, specifically the time-lapse electrical resistivity imaging method, in conjunction with groundwater monitoring, for monitoring coastal groundwater dynamics in an unconfined aquifer at varying time scales and hydrogeological settings present at formerly glaciated sites worldwide. We generated two-dimensional baseline salt water intrusion maps for the test site, located on the coast of Rhode Island, USA. The time-lapse electrical resistivity survey method enables the rapid estimation of fresh groundwater discharge. Our approach offers insight into the mechanisms and seasonably variable salt water-freshwater interactions in unconfined heterogeneous aquifers. Although the results are site-specific, their implications are broad and may stimulate other studies related to sea to land pollution (sea water intrusion) and land to sea pollution (groundwater discharge) in heterogeneous coastal aquifer settings.

Study on Resistivity Imaging of Urban Landfill Leachate Channel Using 3D Electrical Resistivity Tomography with Annular Electrode Configuration

Urban garbage landfills are distributed mostly in a nearly circular shape with complex internal and external environments. The conditions on the top of the landfills are not conducive to the layout of electrical measuring lines and electrodes, resulting in difficulties in using the conventional linear or rectangular mesh high density electrical surveying system to achieve good results for the detection of leachate channel under the garbage body. This paper proposed 3D electrical resistivity tomography (ERT) method by annular electrode configuration with electrodes placed around the landfill. Through numerical simulation and indoor physical simulation experiments, we have discussed the feasibility and effectiveness of this method for circling the pollution range and channel location of landfill leachate. The study shows that the 3D ERT method with annular electrode configuration can effectively detect the spatial location and extension of garbage leachate channel, reflect the leakage of garbage leachate in landfills, and thus provide technical support for the fine detection of garbage leachate channel.

An attempt to use convolutional neural network to recover layered-earth structure from electrical resistivity tomography survey

The Electrical Resistivity Tomography (ERT) method is a geophysical prospecting technique for determining subsurface structure in terms of electrical resistivity distribution. Direct current is injected into the ground through a pair of electrodes, and the potential difference is measured using another pair of electrodes. The estimated resistivity model of the subsurface is then obtained using a mathematical optimization algorithm called the inversion algorithm, which incorporates multiple measured potential differences from different electrode configurations as the input data. The inverted resistivity model serves as a resource for the interpretation process of the survey. Specialists employ the model and the prior geological information in the area to extract the subsurface geological structure under the data measurement profile. The inverted model can be treated as a two-dimensional image in which each element represents resistivity. The image can be visualized as a blurred or distorted version of the actual resistivity image of the subsurface. We, therefore, developed a post-inversion image enhancement code using a neural network aiming to recover the true subsurface model with predetermined features. We employed the convolutional neural network (CNN) that uses the inverted models as input and returns an enhanced model as output. We tested our developed neural network with a case study that utilized the proposed method to recover the layered earth structure which is often found in real surveys. The electrode spacing was 5 meters in the Schlumberger array configuration. The true subsurface resistivity models of training data and validating data for evaluating the neural network were randomly generated based on the predetermined feature of the layered structure. We then generated their respective inverted models from those data through simulated inversion routine. As a result, 94.75% of the enhanced models in the validation dataset exhibited a lower loss metric compared to the original inverted models in the same validation dataset. We also applied the proposed method to practical field data to recover the subsurface layers and compared them with stratigraphic information from a borehole in each area. The result showed that the proposed method gives well-resolved structures in the enhancement process after the typical inversion.

Coastal vulnerability assessment using electrical resistivity tomography in Padang Betuah, Central Bengkulu

<span>Abrasion disaster in the coastal area of Padang Betuah Beach has a high level of abrasion in Central Bengkulu. The local community utilizes abrasion in the coastal area as a tourist attraction and becomes local revenue in the research location. The location that becomes a tourist attraction is decreasing because the coastal area’s land has been abraded. After conducting research using the electrical resistivity tomography (ERT) method in 2D and 3D, it was found that claystone dominated the coastal area at the research location with a resistivity value of 16-200 Ωm at a depth of 15-20 m. The coastal area in Padang Betuah Beach is composed of clay shale rocks (207-220 Ωm), and the depth is 2-14.8 m. Clay shale rocks are not abraded in stones with resistivity values >250 Ωm. This is caused by clay shale, which has low porosity, so it has a compact rock density. Seawater is identified at a depth of 21-63 m with a resistivity value of 2</span><span lang="IN">.</span><span>225-10</span><span lang="IN">.</span><span>2 Ωm. The depth of seawater determined follows the average height of the cliffs in the research location. The abrasion process can be slowed down by making jetties, water breakers, and mangrove cultivation.</span>

Forward Modeling Analysis of Cross-hole Resistivity Tomography (ERT) Using Unstructured Grids

The cross-hole electrical resistivity tomography (ERT) method has advantages in obtaining deep geological information and can accurately image complex underground structures. However, it is usually difficult to fit complex boundaries using structured grids in the modeling process. The accuracy of forward modeling is affected by the meshing of the model. The unstructured grids may describe the irregular complex model more effectively. Therefore, we study cross-hole ERT forward modeling, using unstructured grids to analyze the forward characteristics of complex underground structures. The effectiveness of the unstructured grids in cross-hole ERT has been revealed in this work.

Application of electrical resistivity tomography and geotechnical techniques for identification and characterization of collapsible soils in Bafoussam (Western, Cameroon)

Road failure catastrophes have increased in frequency in the West Cameroon area. The collapsed soil characteristics that contribute to these phenomena in Bafoussam have been investigated using the geophysical investigation combined with geotechnical tests. The result of electrical resistivity tomography shows water conditions and heterogeneity of road foundation materials: resistivity values higher than 200 Ωm indicate dry materials, values between 30 and 200 Ωm define wet materials, and values lower than 30 Ωm indicate the very wet or water-saturated materials. These water-saturated materials can therefore move, bounded by a sliding surface of high-resistivity materials. Geotechnical properties analysis shows that these materials are clayey-sensitive water (64% clay fraction; A-7-6), very plastic (liquid limit: 46–63% plasticity limit: 29–39%), compressible, with high porosity (e > 0.8), low shear strength, and high friction angle (24–37°). The quality of foundation materials associated with high slopes (> 40°) and heavy rainfall in wet seasons (July–October) means that seepage water is the main factor responsible for the mass movement observed on the road of Western Cameroon. The construction or rehabilitation of these roads should be carried out in compliance with the natural conditions of the project site.Article highlights- 2D Electrical Resistivity Tomography method is able to determine the nature, subsurface structure and water conditions of road foundation soils.- Geotechnical test can be used to define the physical and mechanical properties of road foundation soils.- These two techniques complement each other to understand the mass movement observed on two sections of road failures caused by seepage water.

Landslide ground model development through integrated geoelectrical and seismic imaging in Thungsong district, Nakhon Si Thammarat, Thailand

A ground model of a shallow landslide in rainfall-induced slope failure of Thungsong, Nakhon Si Thammarat, southern Thailand is developed through an integrated geophysical approach, utilising electrical resistivity tomography and P-wave seismic refraction tomography (SRT) methods. Those two methods were applied to assess landslide structure and study deformation mechanisms along four profiles. Beside the four profiles there is another profile, which was acquired near an borehole and used for the calibration with geological data. Our results show subsurface structures in terms of the ground model used to determine stratigraphic layers, zones of saturation or groundwater table, and significant differences between the landslide slip material and the underlying bedrock. The clay-rich zones (resistivity less than 500 Ωm) in the colluvium on the relatively steep slope, show enhanced potential for landslides. This silty clay plays an important role for landslide activation in this site. Moreover, a combination of steep slopes, shallow basement rocks overlain by clay-rich colluvium, and seasonally high rain fall leads to landslides in the region. The ground model produced by geophysical imaging for this region achieves a comprehensive understanding of the structure and lithology of a complex landslide system and overcomes the limitations of remote-sensing data or isolated intrusive sampling techniques alone.

Electrical resistivity tomography through reinforced concrete floor

AbstractThe electrical resistivity tomography (ERT) method is often challenged by the presence of reinforced concrete (RC) in urban and industrial environments, because the embedded metallic wire mesh can severely distort the distribution of subsurface currents. We investigate one typical scenario in real applications, in which an RC floor overlays the natural topsoil or rock. Our synthetic forward simulations show that the embedded wire mesh behaves like a local good conductor in data of small source‐receiver separations and acts like an equal‐potential object that keeps the potential from decaying at large source‐receiver separations. Routine ERT inversions that ignore the RC cannot work properly because the thin and highly conductive wire mesh may be manifested as large uninterpretable low‐resistivity anomalies in the imaging results. Two remedies are adopted to improve the ERT resolution in such cases. First, we find a top layer with high conductivity in our model to adequately represent the wire mesh; then, we initiate the inversion with the top‐layer model as the starting and reference model. This warm‐start approach overcomes the difficulty of recovering the large conductivity contrast between metallic objects and regular earth materials. Second, underground electrodes are added to the survey array, so more information from depth can be obtained to fight against the dominance of current channelling in the wire mesh. Finally, our strategies are used to invert a real ERT dataset from an indoor manufacturing plant, where RC covers the entire floor of the building and electrodes are in contact with the soil through open holes in the floor. Our simulation and field data inversion verify our findings and demonstrate the effectiveness of our solutions in improving the resolution of ERT when the survey is carried out over RC floor in urban and industrial environments.

New Insights from Geophysical, Hydrogeological and Borehole Data into the Deep Structure of the Louta Phosphatic Deposit (Gantour Basin, Morocco): Mining Implications

The Gantour Phosphatic Basin (GPB) is formed by a sedimentary series of Maastrichtian to the Eocene age, which consists of alternating phosphate layers and sterile levels. This series outcrops in the northern part of the basin, where it is exploited in open-pit mines. The exploration methodology employed by the Office Chérifien des Phosphates (OCP) group to investigate the GPB is based on direct recognition with boreholes drilled on a 500 × 500 m grid. This research is concerned with the compilation and analysis of data collected during several drilling campaigns conducted on the central segment of the GPB, namely the Louta deposit. This research also includes acquiring, processing, and interpreting new geophysical and hydrogeological data. Its main objective is to provide a better understanding of the deep structure of the phosphatic series. Therefore, the present study was carried out according to a multidisciplinary approach that comprises three parts. (i) The first one involves geological modeling of the exploration borehole data using Datamine Studio RM software (version 1.4), developed by Datamine Corporate Ltd., (Bristol, United Kingdom). It results in establishing a series of geological cross-sections that display a detailed view of the deep structure of the phosphatic series and its lateral variations. (ii) The second part is related to the hydrogeological study, whose purpose was to elaborate on an accurate and updated piezometric map of the study area. The new map helps understand the groundwater flow in the Louta deposit. Furthermore, the superimposition of the piezometric level with the geological sections throws light on the flooded volume of phosphate in this deposit. (iii) The third part of the study focuses on implementing the Electrical Resistivity Tomography (ERT) method. The interpretation of the recorded geoelectrical data not only highlights the main features controlling the mode and the proportion of the phosphate series deepening under the Plio-Quaternary cover but also confirms the evolution of the overall structure of the studied area. The obtained 2D ERT models generally corroborate the cross-sections produced by geological modeling. They also correlate with the information provided by the hydrogeological study. Such information will help guide future hydrogeological and mining extraction planning in the studied area.

Geophysical and Geochemical Pilot Study to Characterize the Dam Foundation Rock and Source of Seepage in Part of Pensacola Dam in Oklahoma

Pensacola Dam, operated by the Grand River Dam Authority (GRDA), is a multiple-arch buttress dam constructed in 1940. The dam has little or no existing geophysical reports on the integrity of the dam foundation rock and even less knowledge at depth. Visual inspection indicated evidence of seepage at some arches of the dam. As a pilot study, we conducted a suite of geophysical surveys inside two arches (Arch-16 and Arch-17) and a part of the downstream berm to characterize the dam foundation rock, delineate seepage zones, and identify the most appropriate geophysical methods for temporal monitoring of the dam’s conditions. The geophysical methods included electrical resistivity tomography (ERT), self-potential (SP), multichannel analysis of surface waves (MASW), compressional (P)-wave refraction, and shear (S)-wave reflection. Water samples were collected for geochemical analysis to investigate the source of the seepage flow inside Arch-16. The geophysical results characterized the dam foundation rock into an unsaturated limestone and chert overlying a water-saturated limestone and chert. The ERT profiles indicated that groundwater is rising inside the arches and significantly dropping under the downstream berm, which can be due to the uplift pressure beneath the dam base. Zones of high seepage potential were detected near the buttress walls of the two surveyed arches, which may be related to previous blasting, excavation of the dam foundation, concrete placement, or improper grouting. The geochemical analysis of water samples taken from the artesian wells inside Arch-16 and the Grand Lake revealed different chemical compositions, suggesting that the source of water could be a mixture of groundwater and lake water or lake water interacting with rock and reaching the surface through fractures; however, more sampling and further analysis are required to ascertain the source of the seeps. This study showed that the ERT, SP, and S-wave reflection methods have effectively characterized the dam foundation rock and seepage zones beneath the arches. The study provided a better understanding of the conditions of the dam foundation rock, evaluated the utilized geophysical methods, and determined the optimum geophysical methods that can be used for the characterization and monitoring of the subsurface conditions along the entire length of the dam. In this study, we have demonstrated that the integration of effective geophysical surveys and geochemical analysis yielded optimum results in solving a complex dam safety problem. This strategy promotes the best practice for dam safety investigation.

Using Electrical Resistivity Tomography Method to Determine the Inner 3D Geometry and the Main Runoff Directions of the Large Active Landslide of Pie de Cuesta in the Vítor Valley (Peru)

Pie de Cuesta is a large landslide with a planar area of 1 km2 located in the Vítor district, in the Arequipa department (Peru), and constitutes an active phenomenon. It belongs to the rotational/translational type, which concerns cases that are very susceptible to reactivation because any change in the water content or removal of the lower part can lead to a new instability. In this context, a previous geological study has been decisive in recognizing the lithologies present and understanding their behavior when they are saturated. But it is also necessary to know the inner “landslide geometry” in order to gusset a geotechnical diagnosis. The present study shows how the deep electrical profiles (ERT, electrical resistivity tomography method), supported by two Vp seismic refraction tomography lines (SVP), have been used to create a 3D cognitive model that would allow the identification of the inner landslide structure: the 3D rupture surface, the volume of the sliding mass infiltration sectors or fractures, and the preferred runoff directions. Moreover, on large landsides, placing the geophysical profiles is a crucial aspect because it greatly depends on the accessibility of the area and the availability of the physical space required. In our case, we need to extend profiles up to 1100 m long in order to obtain data at greater depths since this landslide is approximately 200 m tall. Based on the geophysical results and geologic information, the 3D final model of the inner structure of this landslide is presented. Additionally, the main runoff water directions and the volume of 90.5 Hm3 of the sliding mass are also estimated.

Lithology Of Geothermal Potential Areas Using The Electrical Resistivity Tomography (ERT) Method

The rock lithology of the potential hydrothermal area has been studied using Electrical Resistivity Tomography (ERT) in Pungguk Pedaro Village, Bingin Kuning District, Lebong Regency. Field data acquisition uses a stretch length of 480 meters with the MAE X612-EM Geoelectric tool that forms a straight line. ERT method, using Res2dinvx64 software. This study aims to determine the subsurface conditions of the potential hydrothermal area and the characteristics of the rocks that make up the hydrothermal area. The results of this study can be concluded that Pungguk Pedaro Village is dominated by Clay, Sandstone, Sandy Gravel, Andesite, Basalt, and Granite rocks. Line 1 has no potential for hydrothermal distribution because there has been a mixture of hydrothermal water with mountain water, so only groundwater is obtained on this line.

DETERMINATION OF OPTIMAL OBSERVATION NETWORK PARAMETERS FOR MAPPING PALEOCHANNEL BY THE ELECTRICAL RESISTIVITY TOMOGRAPHY METHOD BASED ON NUMERICAL AND PHYSICAL MODELING

Link for citation: Osipova P.S., Olenchenko V.V., Chekryzhov A.V. Determination of optimal observation network parameters for mapping paleochannel by the electrical resistivity tomography method based on numerical and physical modeling. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 10, рр. 232-242. In Rus. The relevance of the study is explained by the need to determine the methodological features of applying the electrical resistivity tomography method to map paleochannels when prospecting for placer gold. The main aim: to determine the necessary and enough parameters of the observation network for paleochannel mapping based on numerical and physical modeling. Object: electrical fields on the physical and numerical model of the paleochannel. Methods: electrical resistivity tomography, physical experiment, numerical simulation. Results. Electrical soundings by electrical tomography were carried out on a physical model of a river valley. In addition, a numerical experiment was performed on a three-dimensional model of a river valley fragment with a paleochannel. The unit of the survey scale is the distance between two electrodes, which in the experiment is 1 cm and is equivalent to 5 m in real field studies. The distance between the profiles varied from 2 to 12 cm with a step of 2 cm, which corresponds to different survey scales. In accordance with geological concepts, the authors formed a model of a river valley with a segmentally gently stage of channel formation. Three-dimensional inversion was carried out for the data set obtained at the maximum density of the observation network, and then for the data sparse to the desired scale. On the resistivity map, the paleochannel is recognized by a ribbon-shaped high-resistivity anomaly. The analysis of the maps showed that to determine the shape of the paleochannel in plan, it is necessary to use the observation network scale of 1:3000, at which the distance between the profiles is 30 m. The physical experiment results were confirmed by mathematical modeling. The scale should be reduced to 1:5000 with detailing in individual areas to improve the economic efficiency of geophysical research.

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

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

Geophysical investigation of pavement failure along Jonathan by-pass - Akansoko and Atimbo - Parliamentary roads in Calabar Metropolis Cross River State, Nigeria

This study examined pavement failure in some roads in Calabar Metropolis using electrical resistivity tomography method. Seven (7) measurements were taken at the natural soil opposite the failed and stable segments of the road with the aid of Wenner electrode configuration at spacing of 5.0, 10.0, 15.0, 20.0, 25.0, 30.0 and 35.0m with spread length of 105m. The findings of this study revealed that along Jonathan by- pass – Lafarge – Akansoko road, low resistivity values were 8.0Ωm – 73.0Ωm at Akansoko a stable segment; 6.0Ωm - 17.0Ωm at Ukwua Itiat and 30.0Ωm - 94.0Ωm at Idundu market a failed segment. Along Atimbo - Jonathan – Parliamentary road, moderate/high electrical resistivity values in the range 331.0 Ωm – 1018.0 Ωm across the profile was obtained at Federal Government Girls’ College by airport a control segment; 26.0 Ωm – 68.0 Ωm at opposite rice seedling site a failed segment and 49.0 Ωm – 74.0 Ωm at Message point Assembly Church. These results showed that the remote cause of road failure in the area is clay/shale/weathered geologic materials with low resistivity values. It was recommended that detailed geophysical investigation should always be conducted on any proposed site for road construction and/or rehabilitation before embarking on the project.