Analysis of geomaterials using frequency-modulated continuous wave radar in the K-band

In this paper we present the preliminary findings from an investigation into Frequency Modulated Continuous Wave (FMCW) sensing of geomaterial mechanical properties. The authors believe this study’s results represent frontier research in the application of FMCW sensing for geomaterial analysis. Accurate modelling of the response to deformation requires an understanding of in situ rock characteristics and phenomena, such as fluid phase distributions with time and evolving pore geometry. Due to the difficulty in assessing properties inside a solid rock sample, the intrinsic rock parameters and the operative deformation mechanisms and their parameters are typically inferred from post failure analysis by slicing the sample. In this research we introduce the theory of FMCW sensing and results based on analysis of return signal amplitude and phase over a frequency bandwidth of 24 – 25.5 GHz, the K-Band. Variations in return signals between samples are due to a combination of radiation backscatter, transmission and dispersion. Geomaterial samples analysed are: Darney, Doddington, Lazonby, Locharbriggs and Red St. Bees Sandstones, Cotswold Gold Oolitic Limestone and Great Tew Ferruginous Ironstone, with results indicating that, in the K-Band, calculated values for relative permittivity utilising free-space radiation transmission data give results that reflect known material types when taking into account compositional impurities. These preliminary experimental results support the sensitivity of the FMCW sensing modality to variances in geomaterial properties.