Use of Seismic Interferometry for Geological Surveying Ahead of the Tunnel Face

In general, the seismic survey of a tunnel excavation requires careful arrangement of seismic sources and receivers, which causes interruption of tunnel excavation work. However, when blasting is used for excavating the tunnel, the blasts themselves can be used as the seismic survey source, and it becomes possible to continuously evaluate the geological features ahead of tunnel. We called this method -the Seismic While Excavating using SSRT method (SWE-SSRT). Recently, research has focused on the seismic interferometry method as this does not need a strong single seismic source and can utilize non-blast construction noises. The seismic noises of the tunnel construction could be adopted as a seismic source for the geological survey ahead of a tunnel face. And seismic interferometry is useful for SWE-SSRT as it requires fewer, less-complicated measuring devices. In this paper, we carried out numerical analysis of an acoustic field simulating both single and multiple-steps blasting. The result shows that the seismic interferometry for SWE-SSRT could have applicability to the survey ahead of a tunnel face.