Cross-Hole Radar Fractures Detection of Tunnel Side Wall Based on Full Waveform Inversion and Reverse Time Migration

• Published in: Geotechnical and geological engineering 2022-03, Vol.40 (3), p.1225-1236
• Main Authors: Sun, Fahe, Wang, Jiaxing, Ma, Chuanyi, Li, Wenhan, Zhang, Fengkai, Fan, Kerui
• Format: Article
• Language: English
• Subjects: Civil Engineering; Data analysis; Data processing; Detection; Earth and Environmental Science; Earth Sciences; Fractures; Geophysical data; Geophysical exploration; Geophysics; Geotechnical Engineering & Applied Earth Sciences; Hydrogeology; Image resolution; Imaging techniques; Mathematical models; Methods; Original Paper; Permittivity; Position (location); Radar; Radar detection; Terrestrial Pollution; Tunnels; Waste Management/Waste Technology; Waveforms
• ISSN: 0960-3182; 1573-1529
• DOI: 10.1007/s10706-021-01956-z

Cross-hole radar is a method for geophysical exploration of geological conditions between two holes that can meet the need for refined detection of fractures. Full waveform inversion and reverse time migration are usually used in geophysical data processing and imaging. Full waveform inversion can invert the high-resolution relative permittivity image of the underground using the full-amplitude and phase information of the radar wave. Reverse time migration can migrate each reflection point in the radar record to its original position, thereby reflecting the real location of the underground interface. In this paper, we combined these two methods to achieve the purpose of refined detection of cross-hole radar for fractures in the tunnel side wall. Through several numerical simulation examples, we found that when there is a certain degree of electrical difference between the fractures and the surrounding rock, full waveform inversion can accurately reflect the distribution of the fractures and the relative permittivity value. Reverse time migration is more prominent in the description of the low-angle fractures interface, which facilitates the accurate division of the fracture. The combination approach of the two methods can accurately reflect the information of fractures in the wall, but the imaging effect for high-angle fractures is not ideal. The engineering data processing results of the cross-hole radar measured on the tunnel side wall of the Yinsong, Jilin, China prove the reliability of the method.