Improving the galvanic contact resistance for geoelectrical measurements in debris areas: A case study

Abstract

This paper aims to test, in a quantitative way, the different approaches that can be applied to improve the contact resistance problem in a debris environment for the acquisition of electrical resistivity tomography. We collected various datasets on the same investigation line in a blocky ground surface of a landslide deposit, using different coupling systems: single electrodes placed between the boulders, adding extra electrodes in parallel and drilled single electrodes inside the blocks. We performed the measurements in natural dry conditions, then we added salt water nearby the electrodes hammered among the boulders and we filled the drilled holes with a conductive carbomer‐based gel. The results clearly demonstrate that using salt water significantly reduces the contact resistances, but also that, if salt water is not available, we can collect a good quality dataset in dry conditions by connecting more electrodes in parallel. Drilling the electrodes directly inside the boulders decreases the data quality but, if necessary, we demonstrate that the use of a commercial carbon polymer gel can provide a marked improvement in contact resistances.

Combining Ground Penetrating Radar and Frequency Domain Electromagnetic Surveys to Characterize the Structure of the Calderone Glacieret (Gran Sasso d’Italia, Italy)

“…In these periglacial landforms, the GPR technique is, in fact, more complicated to apply since the coarse-blocky surface hinders data acquisition and enhances the problem of signal scattering. However, the FDEM method is not affected by these problems and does not need good galvanic contact with the surface as required by the ERT method [30]. Moreover, the logistic effort of the FDEM investigation is much lower in comparison to the ERT surveys and can represent a reliable preliminary investigation tool to evaluate the subsoil structure.…”

Characterization of a Contaminated Site Using Hydro-Geophysical Methods: From Large-Scale ERT Surface Investigations to Detailed ERT and GPR Cross-Hole Monitoring

“…Once a reciprocal error threshold value is defined, all the quadrupoles with higher values are filtered out and not considered during the inversion process. Highquality ERT datasets have reciprocal errors of lower than 5%, while low-quality datasets have values as high as 20%, typically when the galvanic contact between electrodes and the ground surface is poor [20].…”

Brief communication: Mountain permafrost acts as an aquiclude during an infiltration experiment monitored with ERT time-lapse measurements

“…The error is usually high in rock glacier environments, due to the high contact resistances between electrodes and boulders (Hauck & Kneisell, 2008). To partially overcome this problem, and increase the amount of injected current (Pavoni et al, 2022), we inserted the electrodes between the boulders using sponges soaked with saltwater (Fig. 2A).…”