Design for a mountain tunnel is based on the results of preliminary surveys carried out on the surface above the planned tunnel route. At that time, one of the most useful surveys is seismic exploration by seismic-refraction, which is carried out along the entire tunnel. However, when tunnel is deep under the ground, the precision of the survey usually decreases. And excavation generally damages rock mass near tunnel, which called excavation damage zone (EDZ). The extent of this zone depends on geological structure, excavation method, overburden, and numerous other parameters. And so it is important to carry out seismic exploration within the tunnel as construction progresses, and to verify the seismic velocity of rock mass near the tunnel. Accordingly, there is considerable interest in the development of a seismic-wave exploration system that enables accurate and safe measurements to be taken within the tunnel as it is being driven.
We are developing the Tunnel Face Tester (TFT), which measures seismic waves occurred by tunnel excavation blasting. In this study, we examine the estimation of the EDZ using TFT survey system. This paper discusses the seismic velocity of rock mass near tunnel, and the results of in-site measurements.
