Substantiation for a new non-contact measurement technique in electrical resistance surveys

Abstract

Background. Methods for electrical resistance surveys include those of electrical sounding and electrical profiling with various arrays. Measurements were originally carried out at direct current, although low-frequency alternating current was used later. In the case of direct current, the sole sources of the primary electric field in these methods comprise the charges of the A, B current electrodes, with the measured value being the electric field voltage E equal to the potential difference ΔUMN in the MN line with the measuring electrodes M, N. According to the measurement results, the apparent electrical resistivity is determined, which is convenient for interpreting the measurement results ρк. However, in some cases, e.g., when conducting measurements in permafrost areas, it can be difficult to ensure reliable grounding of the electrodes. Therefore, half a century ago, research was initiated to substantiate the possibility of contactless measurements in the method of electrical profiling with the alternating current I in the AB line. Until recently, the technique of non-contact measurements and interpretation of the results obtained has been based on approximate approaches, rather than on a strict solution of the forward problem of electrodynamics.Aim. Objective substantiation of the non-contact measurement technique based on the solution of a forward electrodynamics problem.Materials and methods. The data obtained by mathematical simulation were analyzed.Results. The results of calculations for a model corresponding to the possible conditions for contactless measurements in electrical exploration by the resistance method are presented. A case is considered when a generator line AB of a harmonically varying current I is located in the air, at a height h above a homogeneous conducting half-space with a specific electrical ρ2.Conclusion. In comparison with the method currently used for non-contact measurements, it seems more effective to determine the apparent electrical resistivity from the reactive component of the electric field voltage E in the measuring line MN that varies in phase with the current I in the generator line AB.