Institut für Geophysik > AG > Seismik > Projekte > OnSITE - On-line seismic imaging for tunnel seismic exploration

OnSITE - On-line seismic imaging for tunnel seismic exploration


This project is part of the project OnSITE coordinated by the GeoForschungsZentrum (GFZ) Potsdam. It is funded by the BMBF within the programe Geotechnologien. Project Duration: 1. August 2006 - 31.Juli 2009.
Work group

Denise De Nil
Stefan Jetschny
Thomas Bohlen

 

Objectives

Work Package 2.1
Seismic Prediction ahead of tunnel construction using Rayleigh-beams (Ray)

For deep underground excavations online seismic exploration ahead of a tunnel should become an essential component of the excavation plan to increase the safety and efficiency of the tunneling operation. We propose to develop a new forward looking seismic imaging technique which uses body waves (compressional waves and shear waves) radiating directly forward into the direction of drilling. These waves are efficiently generated by conversion of high amplitude Rayleigh waves arriving at the front tunnel face after they were generated by a seismic source located behind the tunnel boring machine (TBM). The front tunnel face in this case acts like a source emitting body waves into forward directions (Figure 1). We call these waves “Rayleigh-beams”. Major goals of this project are (1) to develop efficient processing techniques to reduce the high amplitude monocromatic noise often observed in tunnel seismic data, (2) to use beam-forming techniques to illuminate specific direction behind the tunnel front face, and (3) to implement new imaging algorithms in an efficient way allowing online prediction of geological heterogeneities ahead of the tunnel construction

 
Finite-Difference simulation of Rayleigh-beams. a) Rayleigh waves (denoted by R) are excited by a hammer and travel along and around the tunnel. When they arrive at the front face they are converted into body waves. We name these waves Rayleigh-beams since beam forming can be applied to direct the converted waves into specific directions. b) Seismograms recorded by the geophones shown in a), R = direct Rayleigh waves, R-R = reflected Rayleigh wave at the front face, R-S-R = S-wave reflection at the interface at Y=55m and converted back into a Rayleigh wave. Note the high amplitudes of the reflected event.

Recent Publications

Peer reviewed papers

Jetschny, S., Bohlen, T., De Nil, D., 2008, On the propagation characteristics of tunnel surface-waves for seismic prediction, submitted for publication in Geophysical Prospecting.

Lüth, S., Rechlins, A., Giese, R., Tzavaris, J., Groß, K., Buske, S., Jetschny, S., De Nil, D., Bohlen, T., 2008 ,Seismic prediction ahead of a tunnel face - Modeling, field surveys, geotechnical interpretation, submitted for publication in the International Journal of the Japanese Committee for Rock Mechanics.

Bohlen, T., Lorang, U., Rabbel, W., Müller, C., Giese, R., Lüth, S., Jetschny, S., 2007, Rayleigh-to-shear wave conversion at the tunnel face - from 3D-FD modeling to ahead-of-drill exploration, Geophysics, 72, No. 6, T67-T79 (pdf)

Lüth, S., Giese, R., Otto, P., Krüger, K., Mileitz, S., Bohlen, T., Dickmann, T., 2007, Seismic investigations of the Piora Basin using S-wave conversions at the tunnel face of the Piora adit (Gotthard Base Tunnel), Int. J. Rock Mech. Mining Sc., doi:10.1016/j.ijrmms.2007.03.003

Reviewed expanded abstracts presented at EAGE and SAGEEP

Jetschny, S., Bohlen, T., De Nil. D., 2008, On the propagation characteristics of tunnel surface-waves, provisionally accepted for oral presentation in the special session "Cavities and Tunnels" of the 22nd Annual Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP) to be held in Fort Worth, Texas, 29 March - 2 April, 2009.

Jetschny, S., et al., 2008, Seismic prediction ahead of tunnel construction using Rayleigh-waves, 70th EAGE Conference and Exhibition in Rome, Italy (1.0 MB - pdf)

Talks and posters at other conferences

Denise De Nil, Daniel Köhn, Stefan Jetschny and Thomas Bohlen (2008), Beamforming with RSSR-waves for imaging structures ahead of a tunnel face, 68th annual meeting of the Deutsche Geophysikalische Gesellschaft in Freiberg, Germany.

Jetschny, S., Bohlen, T., De Nil, D., 2008, Imaging of geological structures ahead of the tunnel by interpretation of RSSR-wave polarization, 68th Annual Meeting of the Deutsche Geophysikalische Gesellschaft in Freiberg, Germany.

Jetschny, S., et al., 2008, Imaging of geological structures ahead of tunnel constructions, 3rd OnSITE workshop, 12.03.2008, oral presentation (18 MB - pdf)

Denise De Nil and Thomas Bohlen (2007),Towards beamforming of Rayleigh-to-body converted waves for seismic imaging ahead of tunnel construction, 67th annual meeting of the Deutsche Geophysikalische Gesellschaft in Aachen, Germany (pdf)

Jetschny, S., et al., 2007, On the nature of tunnel surface-waves, 67th annual meeting of the Deutsche Geophysikalische Gesellschaft in Aachen, Germany (pdf)

Jetschny, S., et al., 2007, On the propagation characteristics of tunnel surface-waves, AGU Fall Meeting 2007 in San Francisco (1.5 MB - pdf)

 

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