Full-wave characterization of EM transmission and propagation in TBM environment, a temporal and spectral GPR study

Details of the temporal and spectral study on the transmission and propagation of EM wave in a 3D-volume model for tunnel boring machine (TBM) environment using near-field power (NFP) approach are reported herewith. Typical TBM´s common underground deposits (sand, silt, clay, limestone, granite) with different degrees of wetness (varying from 0% to 20%) are investigated using full-wave electromagnetic method. The NFP´s data, taken at predefined calibrated reference plane, revealed clear physical insights and provided accurate information to key ground penetrating radar (GPR) design parameters and the logical arrangement of the antennas, especially when the sensor system is tailored for specific application to as in TBM environment. We also detected several numerical irregular-behaviors (high-spectra had less attenuation than low-spectra) displayed by different host-media, these phenomena are coincided with which Prof. Peter [1994] experimentally reported two decades ago, but he found no answer for this retrospect at that time. These irregularities are mysterious to all principal GPR designers and geo-researchers. In view of interaction of super wideband (SWB) antenna and media, these mysteries are now identified and clarified through full-wave analysis of the transmit-propagation chain. Detailed analysis and numerical results will be explained in details and demonstrated in the full paper and during the conference presentation.