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Subsurface exploration for foundation design
Published in An-Bin Huang, Hai-Sui Yu, Foundation Engineering Analysis and Design, 2017
The basis for making an electrical sounding, irrespective of the electrode array used, is that the farther away from a current source the measurement of the potential, or the potential difference is made, the deeper the probing will be. Typically, a maximum electrode spacing of three or more times the depth of interest is necessary to assure that sufficient data are gathered.
Use of time-lapse 2D and 3D geoelectrical inverse models for monitoring acid mine drainage -a case study
Published in Soil and Sediment Contamination: An International Journal, 2023
Behshad Jodeiri Shokri, Foojan Shafaei, Faramarz Doulati Ardejani, Ali Mirzaghorbanali, Shima Entezam
In general, traditional geoelectrical surveys are carried out with a specified electrode array, which consists of two current and two potential electrodes, to recover the apparent resistivity distribution of the earth materials in the subsurface layers (Edwards 1977). Electrode arrays such as Wenner, Schlumberger, Pole-Dipole, and Dipole-Dipole are conventional configurations (Dahlin and Zhou 2004). The selection of the array’s type depends on the required spatial resolution, the observed model resistivity, and maximum depth penetration (Loke et al. 2013). the Dipole-Dipole array is considered as the best choice for locating vertical and dipping structures due to its high image resolution. Besides, it is best suited to mapping lateral resistivity changes. The Dipole-Dipole has relatively high anomaly effects. As a result, it may be risky because of noise contamination. Hence, it often produces lower signal-to-noise ratios in the surveys (Milsom and Eriksen 2011). The Dipole-Dipole has symmetric electrode configurations for regular and reciprocal measurements that provide better data quality control to delineate the location of 3D geological bodies (Dahlin and Zhou 2004). This configuration can also be employed to build 2.5D resistivity models by combining parallel 2D surveys (Zhdanov 2009). A complete 3D survey requires placing electrodes in a 2D grid with measurements in different directions (Loke et al. 2013). 4D measurements refer to high temporal resolution. In 3D time-lapse surveys, the change of resistivity in both space and time is measured. Indeed, measurements are repeated after a few days/months/years using the same 2D survey line or 3D survey grid (Loke et al. 2013; Loke and Dahlin 2011).