121 6. Borehole electrical panels:an experiment that enables radial investigation around boreholes (Habert et al., 2006). Today, this method has been adapted and is commonly used in geotechnical applications to measure the diameter of jet grouting columns (Frappin et al., 2001; Frappin, 2011). At the HES site, a similar method was used, involving transmitting and receiving electrodes placed within the borehole to measure variations in electrical potential. Data processing focused exclusively on apparent resistivity values. As part of the KARST’OGENE project, vertical electrical panels were incorporated to assess the detectability of karst horizons by comparing the results with existing data. The vertical electrical panels were performed using the following equipment: • a 132-meter cable lowered to the desired depth in the boreholes, holding 32 electrodes spaced at 1-meter intervals. • an ABEM Terrameter LS2 resistivity meter. A Wenner-Schlumberger measurement protocol was used from the bottom to the top of the open-hole sections of the boreholes, with offsets of 15 m for each rollalong measurement performed. For each measurement, one set of 4 electrodes out of the 32 is used. Two electrodes are used for current injections (A and B), and two for measuring the electrical (a) (b) Figure 2 View of measurement equipment. (a) Electrode on measuring cable, (b) ABEM Terrameter LS2 resistivity meter.
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