Theoretical fundaments to obtain complex permittivity and resistivity in CR method.

LUCUY, ALBERTO; BONGIOVANNI, MARÍA VICTORIA; GRÜNHUT, VIVIAN; OSELLA, ANA

La Haya

Congreso; Near Surface'19 Conference & Exhibition; 2019

European Association of Geoscientists and Engineers

The resistive capacitive contact (CR)method is a non-intrusive geophysical technique that allows to characterize thesubsoil, by means of electrical images. It is based on the capacitive couplingbetween the sensors (dielectric plates) and the ground, and is applied inenvironments where galvanic contact cannot be achieved or where high contactimpedances result in poor data quality (soil contamination and aquifers, mininginvestigations, archaeological surveys, etc.) Two of the most importantproperties of the terrain are the resistivity and dielectric permittivity.There are several models that interpret how the electromagnetic signalpropagates in terms of the conductivity and polarization of the charges underthe action of an electric field. In general, most of the works focus on thephenomenon of polarization (either electronic, ionic, dipolar or by migrationof accumulated particles along a separation interface (Bourdi and Rhazi, 2008)). Whena time-varying electric field is applied on a surface with a sufficiently highfrequency for there to be a considerable relaxation time, not only a complexsusceptibility but also a complex conductivity are generated and therefore, acomplex resistivity.The purpose of this work is to analyzethe behavior of the electromagnetic signal on a soil, with relatively high frequencies,and to link the complex conductivity and resistivity through the tangent oflosses, as a function of a scale factor and a phase shift between the emitted andreceived signal. Through an adequate description of the physical principlesinvolved, a theoretical formulation will be developed.