GNGTS 2018 - 37° Convegno Nazionale

694 GNGTS 2018 S essione 3.2 resistivity values are reflecting this characteristic. For this reason it is really important to select an appropriate sampling frequency to perform high speed resistivity measurements. Conclusions. Although 2D ERT profiles along earthen embankments provide a reasonable layout to study the internal conditions of these structures, 2D profiles are significantly affected by 3D effects arising from the geometry of the embankment. Buried electrodes also play an important role in measurements of apparent resistivities, especially in the shallow part of the investigated area. Analytical modelling was performed to quantify this effect and remove this influence, transforming the data as they were measured with surface electrodes. We used a correction strategy developed by the authors to correct raw data obtained along the river levees and the results show that ERT data are considerably changed after being processed for the effects of 3D geometry and buried electrodes. The correction graphs show that the measured resistivity values are highly amplified with the depth due to 3D geometry of levees. The correction strategy is reasonably removing such effects but it is still an interesting area of research to be well developed to accurately correct these effects. Acknowledgments. The research was partially funded by Fondazione Cariplo, grant n° 2016-0785. Authors are grateful to Annachiara Fasulo for her collaboration in performing laboratory tests and doing the forward modelling. References Arosio D., HojatA., IvanovV. I., LokeM. H., Longoni L., Papini M., Tresoldi G. and Zanzi L.; 2018: A laboratory experience to assess the 3D effects on 2D ERT monitoring of river levees . In: 24 th European Meeting of Environmental and Engineering Geophysics, Porto, DOI: 10.3997/2214-4609.201802628. Arosio D., Munda S., Tresoldi G., Papini M., Longoni L. and Zanzi L.; 2017: A customized resistivity system for monitoring saturation and seepage in earthen levees: installation and validation . Open Geosci., 9 , 457-467. Dahlin T., Johansson S., Sjödahl P. and Loke M. H.; 2008: Resistivity monitoring for leakage and internal erosion detection at Hällby embankment dam . J. of Appl. Geophys., 65 (3), 155-164. Jomard H., Lebourg T., Guglielmi Y. and Tric E.; 2010: E lectrical imaging of sliding geometry and fluids associated with a deep seated landslide (La Clapière, France) . Earth Surf. Process. Landforms, 35 , 588–599. Kuras O., Pritchard J. D., Meldrum P. I., Chambers J. E., Wilkinson P. B., Ogilvy R. D. and Wealthall G. P.; 2009: Monitoring hydraulic processes with automated time-lapse electrical resistivity tomography (ALERT) . Comptes Rendus Geosci., 341 , 10, 868-885. Loperte A., Soldovieri F., Palombo A., Santini F. and Lapenna V.; 2016: An integrated geophysical approach for water infiltration detection and characterization at Monte Cotugno rock-fill dam (southern Italy) . Eng. Geo., 211 , 162–170. Perri M. T., Boaga J., Bersan S., Cassiani G., Cola S. and Deiana R.; 2014: River embankment characterization: The joint use of geophysical and geothecnical techniques . J. of Appl. Geophys., 110, 5-22. Sjödahl P., Dhalin T. and Zhou B.; 2002: 2.5D resistivity modeling of embankment dams to assess influence from geometry and material properties . Geophys., 71 , 3, G107-G114. Supper R., Romer A., Kreuzer G., Jochum B., Ottowitz D., Ita A. and Kauer S.; 2012: The GEOMON 4D electrical monitoring system: current state and future developments. Instrumentation and data acquisition technology . Procedings of GELMON 2011, Berichte Geol. B.-A, 93, 23-26, ISSN 1017 – 8880. Tresoldi G., Arosio D., Hojat A., Longoni L., Papini M. and Zanzi L.; 2018: Tech-Levee-Watch: experimenting an integrated geophysical system for stability assessment of levees. ROL della SGI, DOI: 10.3301/ROL.2018.49.