DIFFERENT TECHNIQUES FOR THE ASSESMENT OF GEOELECTRICAL DATA ERRORS TO IMPROVE THE ELECTRICAL IMAGES OBTAINED AT AN INDUSTRIAL PLANT

MARTINELLI, PATRICIA; OSELLA, A.,; DE LA VEGA, MATIAS; PINIO,A.

NEAR SURFACE GEOPHYSICS

EUROPEAN ASSOC GEOSCIENTISTS & ENGINEERS

Lugar: Houten (Holanda); Año: 2018 vol. 16 p. 238 - 256

1569-4445

ABSTRACTThe objective of our work was to characterize bases of columns belonging to an industrial plant. We have to design a proper methodology for characterizing these structures, in a place with limitations in the availability of space and time for the deployment of sensors, and with other environmental constraints, such as high electromagnetic noise level, soil vibrations due to operating machines, and complex soil composition. In particular, the floor had a stainless steel cover about 1 cm thick, below which there was first a layer of concrete about 30 cm thick and then, clay material used to absorb the oils of the machines. Finally, there was the natural soil where the column bases stand.Given these characteristics, we performed dipole-dipole geoelectric profiles. Holes were drilled through the metallic cover and the concrete layer, with fixed spacings, to insert the electrodes. Because of this and the space and time restrictions, only one profile could be performed for each column. Since we knew the data could contain high noise levels and other errors negatively impacting in their quality, and also because there was a limitation to the length of the profiles, we optimized the measurement configuration by jointly using several electrode apertures, to guarantee the best possible resolution and sufficient penetration depth. One way to obtain adequate error estimations is by performing direct and reciprocal measurements, though this procedure is only applicable to certain configurations, such as dipole-dipole. For each profile, we performed these measurements, and also, as an alternative technique, we carried out a second set of direct measurements, after reinstalling the electrodes. The advantage of this last procedure is that it can be applied with other configurations, like Wenner and Wenner-Schlumberger. Then, for each profile, we performed 2D inversions of the three dipole-dipole datasets separately, without considering data errors. Besides, we inverted the datasets obtained by combining the first direct and the reciprocal measurements, and the first and second direct measurements, considering the error estimations corresponding to each case. In addition, numerical simulations were made, combining direct 3D modeling with 2D inversions.From the results of the study, we can conclude that making reciprocal measurements or a second set of direct measurements is a fundamental methodology for the adequate management of data collected in environmentally complex urban sites. In our study this, together with numerical simulations, allowed obtaining a reliable interpretation of the anomalies observed in the electrical images.