Seismic imaging ahead of a tunnel face with three-component geophones

The present paper proposes an accurate imaging technique for looking ahead of a tunnel face using three-component geophones with tunnel blasting and TBM vibrations as seismic sources. Its procedure is as follows: (1) using three-component receivers set on the tunnel walls, record the seismic signal from the reflectors ahead of the tunnel face; (2) detect the direction of incidence of the reflected wave and (3) by weighting according to the direction of incidence of the reflected wave, image the reflector planes using the equi-travel time plane. The proposed technique is applied to datasets collected at an actual drilling operation site, and the results agreed with the geological observation of the walls after the drilling of the tunnel. (C) 2001 Elsevier Science Ltd. All rights reserved.