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High Resolution Seismic Profiling for Tunnel Engineering at Olkiluoto, Finland
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Near Surface 2009 - 15th EAGE European Meeting of Environmental and Engineering Geophysics, Sep 2009, cp-134-00021
- ISBN: 978-90-73781-72-6
Abstract
The ONKALO tunnel is the underground rock characterisation facility being built for rock characterisation for the final disposal of spent nuclear fuel at Olkiluoto, in Finland. The bedrock is studied, during the construction phase, by geology, geophysics, hydro-geology and geochemistry and rock mechanics. The research is meant to help ensure the suitability of the bedrock for the final disposal. A pilot test of high resolution seismic was done, consisting of reflection imaging ahead and aside of the tunnel and refraction imaging along the same line, 100m long, with sources stations spaced at 1m. Refraction imaging was done from two groups of 10 shots, recorded by the 100m long receiver array. Fractures making an angle of 30° or more with the tunnel axis were imaged several tens of meters away. Vertical fractures perpendicular to the tunnel could also be imaged, but only in the vicinity of the tunnel. Gently dipping fractures were imaged below and above. With only one line along the wall, it may not be possible to resolve between the above–below locations.