Optimization of Array Configurations and Panel Combinations for the Detection and Imaging of Abandoned Mineshafts using 3D Cross-Hole Electrical Resistivity Tomography

Wilkinson, Paul; Chambers, Jonathan; Meldrum, Philip; Ogilvy, R.D.; Caunt, S.

doi:10.2113/jeeg11.3.213

Cited by 48 publications

(60 citation statements)

References 20 publications

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“…The measurement scheme comprised many sets of four-electrode measurements, in which the current flow and potential measurements are crosshole. In general, these provide better signal-to-noise characteristics and greater image resolution than configurations with in-hole current flow and potential measurements (Bing and Greenhalgh, 2000;Wilkinson et al, 2006;. To provide sufficient image resolution in crosshole ERT, it is important that the aspect ratio of the panel (borehole spacing / depth) is < 0.75 (LaBrecque et al, 1996).…”

Section: Data Acquisitionmentioning

confidence: 99%

High-resolution Electrical Resistivity Tomography monitoring of a tracer test in a confined aquifer

Wilkinson

Meldrum

Kuras

et al. 2010

Journal of Applied Geophysics

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A permanent geoelectrical subsurface imaging system has been installed at a contaminated land site to monitor changes in groundwater quality after the completion of a remediation programme. Since the resistivities of earth materials are sensitive to the presence of contaminants and their break-down products, 4-dimensional resistivity imaging can act as a surrogate monitoring technology for tracking and visualising changes in contaminant concentrations at much higher spatial and temporal resolution than manual intrusive investigations. The test site, a municipal car-park built on a former gas-works, had been polluted by a range of polycyclic aromatic hydrocarbons and dissolved phase contaminants. It was designated statutory contaminated land under Part IIA of the UK Environmental Protection Act due to the risk of polluting an underlying minor aquifer. Resistivity monitoring zones were established on the boundaries of the site by installing vertical electrode arrays in purpose-drilled boreholes. After a year of monitoring data had been collected, a tracer test was performed to investigate groundwater flow velocity and to demonstrate rapid volumetric monitoring of natural attenuation processes. A saline tracer was injected into the confined aquifer, and its motion and evolution were visualised directly in high-resolution tomographic images in near real-time. Breakthrough curves were calculated from independent resistivity measurements, and the estimated seepage velocities from the monitoring images and the breakthrough curves were found to be in good agreement with each other and with estimates based on the piezometric gradient and assumed material parameters.

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Section: Data Acquisitionmentioning

confidence: 99%

High-resolution Electrical Resistivity Tomography monitoring of a tracer test in a confined aquifer

Wilkinson

Meldrum

Kuras

et al. 2010

Journal of Applied Geophysics

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“…The resolution of surveys carried out with electrodes on the ground surface decreases rapidly with depth. Cross-borehole surveys have been carried out to improve the resolution across the entire depth range of interest (Slater et al 2000;Wilkinson et al 2006a;Chambers et al 2010).…”

Section: Introductionmentioning

confidence: 99%

“…There have been many significant developments in algorithms to automatically select arrays to maximize the resolution of the inversion model for linear surface arrays and cross-borehole surveys (Stummer et al 2004;Wilkinson et al 2006aWilkinson et al , 2006bLoke et al 2010a;Nenna et al 2011;Hagrey 2012). A non-linear method that calculates the model resolution (the 'Compare R' method) by Wilkinson et al (2006b) proved to be the best method (Loke et al 2010a).…”

Section: Introductionmentioning

confidence: 99%

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Optimized arrays for 2D cross‐borehole electrical tomography surveys

Loke¹,

Wilkinson

Chambers

et al. 2013

Geophysical Prospecting

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The use of optimized arrays generated using the 'Compare R' method for cross-borehole resistivity measurements is examined in this paper. We compare the performances of two array optimization algorithms, one that maximizes the model resolution and another that minimizes the point spread value. Although both algorithms give similar results, the model resolution maximization algorithm is several times faster. A study of the point spread function plots for a cross-borehole survey shows that the model resolution within the central zone surrounded by the borehole electrodes is much higher than near the bottom end of the boreholes. Tests with synthetic and experimental data show that the optimized arrays generated by the 'Compare R' method have significantly better resolution that a 'standard' measurement sequence used in previous surveys. The resolution of the optimized arrays is less if arrays with both current (or both potential) electrodes in the same borehole are excluded. However, they are still better than the 'standard' arrays.

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“…However, in very complex areas, the 2-D inversion model can suffer from artefacts due to structures outside the survey line (Johansson et al, 2007). A 3-D survey and inversion model is required to obtain sufficiently accurate results (Wilkinson et al, 2006;Chambers et al, 2006;Legault et al, 2008). In some areas, repeated 3-D surveys are carried out to detect temporal changes of the subsurface (Rosqvist et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Constrained Time-lapse Inversion of 3-D Resistivity Surveys Data

Loke¹,

Dahlin²,

Leroux³

2011

Proceedings

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SUMMARYThree-dimensional surveys and inversion models are required to accurately resolve structures in areas with very complex geology where 2-D models might suffer from artefacts. 3-D data sets collected at different times are inverted simultaneously using a least-squares methodology that uses roughness filters in both the space and time domains. The spatial roughness filter constrains the model resistivity to vary smoothly in the x, y and z directions. A temporal roughness filter is also applied that minimizes changes in the resistivity between successive temporal inversion models. This method can accurately resolve temporal changes in the resistivity even in the presence of noise. The use of the L1 and L2 norm constraints for the temporal roughness filter are examined using a synthetic model. The L1 norm temporal constraint produces significantly more accurate results when the resistivity changes abruptly with time. A test with field data from a landfill site with methane gas accumulation shows near surface resistivity changes that are probably due to surface temperature variations. The temperature variations cause changes in the gas volume and moisture content in the near surface landfill materials.

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Optimization of Array Configurations and Panel Combinations for the Detection and Imaging of Abandoned Mineshafts using 3D Cross-Hole Electrical Resistivity Tomography

Cited by 48 publications

References 20 publications

High-resolution Electrical Resistivity Tomography monitoring of a tracer test in a confined aquifer

High-resolution Electrical Resistivity Tomography monitoring of a tracer test in a confined aquifer

Optimized arrays for 2D cross‐borehole electrical tomography surveys

Constrained Time-lapse Inversion of 3-D Resistivity Surveys Data

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