Imaging of buried 3D objects by using electrical profiling methods with GPR and 3D geoelectrical measurements

摘要

Detection of near-surface buried objects is usually carried out along one or more survey lines and processed by 2D inversion algorithms. Problems arise if the target is three dimensional. The effect of the 3D objects near the profile strongly depends on the type of the electrode array, and the three-dimensional object located beneath the survey line is also mapped differently to the 2D plane. The indications of 3D objects on a 2D resistivity section depend on each electrode configuration. Theoretical calculations above 3D objects have been carried out in order to examine the problems arising from 2D inversion in the cases of four different electrode arrays (pole-pole, dipole-dipole, equatorial dipole, Wenner alpha). The results of the modelling processes give some useful information which can make it possible to rank the examined arrays from the point of sensitivity for 3D effects and the quality of imaging the object. Test measurements have been carried out in order to prove the conclusions of the theoretical investigations. Two perpendicular survey lines have been measured above a buried cellar using dipole-dipole, pole-pole and Wenner arrays. The 2D pseudosections were compared with the results of the GPR and 3D geoelectric measurements.