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Pole-pole Electrical Resistivity Survey in Near-surface and Conductive Grounds

ABSTRACT The negative potential frequently encountered in dipole-dipole survey is rare in pole-pole survey where the potential growing with the distance is essentially equivalent to the negative potential of dipole-dipole survey. The chief reason why the negative values are common in dipole-dipole survey is said to be poor S/N ratio of dipole-dipole measurements by other investigators. But the present authers highly suspect that shallow, conductive, heterogeneous, structurally irregular ground, which is typical in waste disposal sites, have better chances to contain conductive channels favorable for generating the negative potentials. Smaller electrode spacing of pole-pole survey enhances the spatial resolution in upper part of the ground but this resolution does not persist in deeper parts. To achieve enhanced resolution further in depth, use of other configurations, e.g., dipole-dipole or pole-dipole is recommended. The larger the movable electrodes spacing of pole-pole survey is, the more the depth of some targets is likely to be over-estimated, or vice versa. In spite of poor spatial resolution, however, pole-pole survey is an attractive means of reconnaissance survey. It is field work efficient, yield better S/N ratio measurements, and its detectability of targets is comparable, if not better, to other survey methods. In particular, pole-pole survey is preferred in shallow conductive ground in case the measurements using other electrode configurations are not viable owing to poor S/N ratio. Other investigators also point out this fact in their theoretical study.