Abstract
Assessing and accurately predicting geological conditions ahead of a tunnel face are important in constructing mountain tunnels reasonably and safely. The authors have developed a new type of seismic tomography technique between tunnel and ground surface using a precise time synchronization wireless system with GPS, a vibration of blasting excavation and an automatic data acquisition system. This system enable to illustrate P-wave velocity contour ahead of a tunnel face without stopping an excavation. Based on its velocity distribution, not only a location but also a velocity value of geological change can be evaluated. This paper presents that details of each development and an actual employment of new technique to a construction site.
