Coarse-Grained Geomaterials Characterization Using the High-Frequency Electromagnetic Induction Technique

Electromagnetic induction (EMI) technique has been used in the large-scale geological mapping investigation; however, few studies have associated small-scale EMI responses and soil pore characteristics. We developed a simple theoretical framework to interpret EMI responses of geomaterials and used a parametric study to show the dependency of high-frequency electromagnetic induction (HFEMI) signals on the electrical conductivity and the associated soil pore characteristics. A series of EMI tests were performed on geomaterials with varying water contents, void ratios, and porewater salinities. Results showed the salient dependence of HFEMI signals on the frequency, water content, void ratio, and porewater salinity. Additionally, it was found that the low-frequency noise might affect the data interpretation of frequency-dependent EMI signals, and the log-log plotting could identify the actual materials’ responses in the high-frequency domain. The association between EMI responses and soil properties was explained by the underlying soil electrical conduction phenomenon. A semiempirical equation was derived to interpret soil electrical conductivity from the EMI spectrum, and a good correlation was found between frequency-dependent EMI quadrature signals and soil properties. This study highlights the considerable potential of adopting the HFEMI technique for nonintrusive geomaterials characterization and proposes a systematic methodology for performing EMI screening to obtain reliable EMI signals for geotechnical evaluation.