Effect Of The Soil On The Metal Detector Signature Of A Buried Mine

This paper analyzes the effect of the soil on the response of a metal detector (MD). The total response is first decomposed in a direct coupling between the transmitter and the receiver, the mine contribution and the soil contribution. The mine contribution is further related to its free space signature by introducting a number of transfer functions (TFs). Those TFs characterize the effect of the soil on the field propagation, from the transmit coil to the mine and back to the receiver, and on the mine signature. The expressions derived are quite general. However the TFs and other quantities of interest can only be computed if the scattering problem has been solved. For this it is usually necessary to resort to numerical techniques. Such techniques are computationally expensive, especially to analyze the various effects of the soil as they require to compute the solution for a large set of parameters. Therefore, we propose to model a buried mine by a multilayered sphere. From outside to inside, the layers represent the air, the soil, the mine explosive and the mine metallic content. Further, the analytic solution for such a multilayered sphere is used to compute the mine and soil responses, the mine free space signature and the various TFs as a function of the parameters of interest such as the soil electromagnetic (EM) properties or the mine depth. Finally, the validity domain of a number of practical approximations is discussed.