Engineering Geophysics in China ? the TST tunnel geological prediction technique

Abstract

Currently there are several seismic based tunnel geological prediction techniques, but these have three major deficiencies i.e. they do not differentiate the reflected waves from individual directions and assume that all the waves come from the front tunnel face, they are unable to accurately derive rock velocity in the front tunnel face and need manual input of velocity or use of side rock velocity as a substitute, they are unable to separate P-wave and S-wave correctly. As a result these techniques cannot be accurate and reliable. A new tunnel geological prediction technique, TST (Tunnel Seismic Tomography), is introduced.. TST utilizes spatial observation, F-K filtering and velocity scanning t overcome all these deficiencies. Spatial observation and velocity scanning in TST provides precise velocity distributions and enables accurate location of geological structure. F-K filtering function eliminates all waves but those ahead of the tunnel face and ensures a precisely migrated image of the geological conditions ahead of the tunnel face.