A Successful Mixed Land-Underwater 3D Resistivity Survey In An Extremely Challenging Environment In Amazônia

Castilho, Guilherme P.; Maia, Daniel F. S.

doi:10.3997/2214-4609-pdb.177.41

Cited by 6 publications

(6 citation statements)

References 2 publications

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“…Examples are imaging of sinkholes [3], cavities [4], landslides [5]. It is also one of the most widely used near-surface geophysical survey for civil engineering applications [6]. Other more recent applications can be found in [1].…”

Section: Principles Of Ertmentioning

confidence: 99%

Geo-Electrical Detection of Impermeable Membranes in the Subsurface

et al. 2022

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In this paper, we have investigate looking ahead capabilities of electrical resistivity tomography (ERT) for a soil penetrating tool with electrodes. In our case study, the desired detection resolution (10 to 20 cm at a depth of at least 6 m) was much higher than what can be achieved from classical surface ERT measurements. Therefore, we designed a logging-type tool, that can be pushed into the ground. Our target was a buried PVC membrane which acts as an electrical insulator. In this phase, we performed numerical simulations and laboratory measurements. The methodology is based on a two-step approach. First, we calculate the background resistivity of the tool’s path is determined by inversion of near-looking electrode configurations. Next, the theoretical response (kernel) of the far-looking configurations is calculated for different membrane positions. The root mean square (RMS) error between the kernel and the measurements is minimized to detect the membrane. If the membrane is within sensing reach, the RMS has a minimum for the kernel corresponding to the true membrane position. If no minimum in RMS is found, the membrane is not within sensing reach and the tool can be pushed closer to the membrane. The laboratory tests comprised measurements in a tank filled with either water or saturated sand or saturated sand with clay slabs and chunks. The laboratory results were successful in pinpointing the position of the membrane with an accuracy of 10 to 20 cm, depending on the dimension of the tool and the distance from the membrane.

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Section: Principles Of Ertmentioning

confidence: 99%

Geo-Electrical Detection of Impermeable Membranes in the Subsurface

et al. 2022

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“…In general, surveys in water-covered areas include conventional surveys using a multi-electrode resistivity system where part of the survey line crosses a river or a lake, and surveys conducted entirely within a water-covered environment. In applications in seas and rivers, this method has been performed both with fixed electrodes placed on the water surface or on the seabed and riverbed [23][24][25][26][27][28][29] or by dragging the electric cable on the water surface with the aid of ships or boats [30,31]. In the first case, usually, the cable is weighted in order to allow direct contact with the marine sediments.…”

Section: Introductionmentioning

confidence: 99%

“…Usually, streamer electrodes can be made of steel or graphite; however, the latter are more fragile but more resistant to saltwater corrosion [24]. Less common are electrical resistivity measurements in water-covered areas such as wetlands, ponds, and lakes [31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

ERT and GPR Prospecting Applied to Unsaturated and Subwater Analogue Archaeological Site in a Full Scale Laboratory

et al. 2022

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Geophysical techniques are widely applied in the archaeological field to highlight variations of the physical behaviour of the subsoil due to the presence of ancient and buried remains., Considerable efforts are required to understand the complexity of the relationship between archaeological features and their geophysical response where saturated conditions occur. In the case of lacustrine and wetland scenarios, geophysical contrasts or electromagnetic signal attenuation effects drastically reduce the capabilities of the geophysical methodologies for the detection of structures in such conditions. To identify the capability of the electrical and electromagnetic methods in different water-saturated scenarios, an experimental activity was performed at the Hydrogeosite CNR laboratory. The test allowed us to analyze the limits and potentialities of an innovative approach based on the combined use of the ground-penetrating radar and 2D and 3D electrical resistivity tomographies. Results showed the effectiveness of the ground-penetrating radar for detecting archaeological remains also in quasi-saturated and underwater scenarios despite the em signal attenuation phenomena; whilst the results obtained involving the resistivity tomographies offered a new perspective for the archaeological purposes due to the use of the loop–loop shaped array. Moreover, the radar signal attenuation, resolution and depth of investigation do not allow to fully characterize the archaeological site as in the case of the scenarios with a limited geophysical contrast (i.e., water-saturated and arid scenarios). The experimental tests show that these limits can be only partially mitigated through the integration of the geophysical methodologies and further efforts are necessary for improving the results obtainable with an integrated use of the adopted geophysical methodologies.

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“…When using a floating electrode array, two different measurement procedures can be adopted. First, a moving electrode cable can be towed on the water surface by a vessel (Kwon et al, 2005; Day‐Lewis et al, 2006; Castilho and Maia, 2008; Cardenas et al, 2010; Colombero et al, 2014). As with aquatic ERT surveys, the towed array is used when measuring continual vertical electrical sounding (CVES) as reported by e.g.…”

Section: Introductionmentioning

confidence: 99%

Landslide‐dammed lake sediment volume calculation using waterborne ERT and SONAR profiling

Hartvich

Tábořík

Šobr

et al. 2020

Earth Surf Processes Landf

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Lake sediment volume calculation is a challenging task, namely in cases when detailed drilling is complicated, expensive, or impossible, information on the pre-sedimentation surface unavailable, and record of siltation rate non-existent or too short. This study shows how waterborne, non-invasive geophysical survey, such as electrical resistivity tomography (ERT) can be very effective in acquiring the missing data, namely when combined with sound navigation ranging (SONAR) water depth measurements and supported by information from auxiliary sources. However, ERT surveying in water environment requires specific approaches, as we illustrate on the case of the Mladotice lake study. The lake was created after a landslide in May 1872, and since its formation, the depth has gradually decreased due to sedimentation. We have reconstructed the original surface, calculated the sediment volume, and compiled information on sedimentation to estimate its remaining life span. To achieve this, we measured nine waterborne ERT profiles across the lake. To reach the necessary depth, all ERT profiles were extended on land and crossed the lake using custom-built flotation pads. ERT profiling was combined with SONAR depth measurements, historical bathymetric surveys, borehole core analysis, sediment flux measurements, volumetric calculations, and water conductivity probing. The study has achieved three main results. First, practical applicability and advantages of stationary waterborne ERT profiling in combination with bathymetric sounding were demonstrated. Second, the original lake volume and accumulated sediment was calculated. We estimate that the volume of lake sediment is 187000 m 3 , two-thirds of the original lake volume (over 275000 m 3). Finally, based on three volumetric data sets from 1972, 2003, and 2017, and recent monitoring of the sediment inflow, we propose scenarios of lake filling and its future development. Most interestingly, the sedimentation rate has decreased significantly in the last 20years, suggesting that the lake may survive much longer than hitherto expected.

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A Successful Mixed Land-Underwater 3D Resistivity Survey In An Extremely Challenging Environment In Amazônia

Cited by 6 publications

References 2 publications

Geo-Electrical Detection of Impermeable Membranes in the Subsurface

Geo-Electrical Detection of Impermeable Membranes in the Subsurface

ERT and GPR Prospecting Applied to Unsaturated and Subwater Analogue Archaeological Site in a Full Scale Laboratory

Landslide‐dammed lake sediment volume calculation using waterborne ERT and SONAR profiling

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