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Rayleigh-to-shear wave conversion at the tunnel face - from 3D-FD modeling to ahead-of-drill exploration

Bohlen, Thomas; Lorang, Ullrich; Rabbel, Wolfgang; Müller, Christof; Giese, Rüdiger; Lüth, Stefan; Jetschny, Stefan


For a safe tunnel excavation it is important to predict lithological and structural heterogeneities ahead of the construction. conventional tunnel seismic prediction systems utilize body waves (P- and S-waves) that are directly generated at the tunnel walls or near the cutter head of the tunnel boring machine (TBM). In this work we propose a new prediction strategy that has been discovered by 3-D elastic finite-difference (FD) modeling: Rayleigh waves arriving at the front face are converted into high amplitude S-waves propagating further ahead. Reflected or backscattered S-waves are converted back into Rayleigh waves which can be recorded along the side walls. We name these waves RSSR waves. In our approach the front face acts as a S-wave transceiver. One technical advantage is that both the sources and the receivers may be placed behind the cutter head of the TBM. The modeling reveals that the RSSR waves exhibit significantly higher amplitudes than the directly reflected body waves. The excavation damage zone causes dispersion of the RSSR wave leading to multi-modal reflection response. For the detection of geological interfaces ahead RSSR waves recorded along the side walls are corrected for dispersion and stacked. ... mehr

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DOI: 10.5445/IR/1000028811
Cover der Publikation
Zugehörige Institution(en) am KIT Geophysikalisches Institut (GPI)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2007
Sprache Englisch
Identifikator ISSN: 0016-8033
KITopen-ID: 1000028811
Erschienen in Geophysics
Verlag Society of Exploration Geophysicists (SEG)
Band 72
Heft 6
Seiten T67-T79
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