Print Email Facebook Twitter Looking ahead of a tunnel boring machine with 2-D SH full waveform inversion Title Looking ahead of a tunnel boring machine with 2-D SH full waveform inversion Author Pisupati, P.B. Mulder, W.A. Drijkoningen, G.G. Reijnen, R. Faculty Civil Engineering and Geosciences Department Geoscience & Engineering Date 2015-06-01 Abstract In the near-surface with unconsolidated soils, shear properties can be well imaged, sometimes better than P-wave properties. To facilitate ground prediction ahead of a tunnel boring machine (TBM), active ‘surveys’ with shear-wave vibrators are carried out during boring. In such surveys, only a few shear-wave vibrators can be placed in front of the machine’s cutter head. The vibrators inject a force in the direction perpendicular to the drilling path. We use a vibrator that is capable of exciting low frequencies. Therefore, a full waveform inversion (FWI) approach can be used, which would make the imaging more automatic. Imaging with conventional migration methods suffers from artifacts caused by incomplete aperture and inadequate velocity analysis. In this abstract, we examine the potential of 2-D SH FWI to reconstruct anomalies. In contrast to FWI for hydrocarbon exploration, we have access to reliable low frequencies in the data and are working in the near-field regime. The very limited maximum offset causes diving waves to be absent. This lack of aperture makes it difficult to reconstruct the shear-wave velocity away from the source-receiver array even in the presence of low frequencies. Our study shows that FWI with SH waves should offer a valuable lookahead capability. To reference this document use: http://resolver.tudelft.nl/uuid:64f3c9b5-04f6-4cf9-aa58-1b9364c3e4e5 Publisher EAGE Source 77th EAGE Conference and Exhibition 2015, Madrid, Spain, 1-4- June 2015 Part of collection Institutional Repository Document type conference paper Rights (c) 2015 The Author(s) Files PDF 317030.pdf 621.59 KB Close viewer /islandora/object/uuid:64f3c9b5-04f6-4cf9-aa58-1b9364c3e4e5/datastream/OBJ/view