Non-open-cut tunnel construction technology and monitoring system for railway underpass

In this paper, authors describe the history of underpass construction in Japan and suggest a stability evaluation method using seismic prospecting. Ground destabilization around excavation face causes track settlement. It is required to develop a real time stability evaluation method during excavation. First, we executed trapdoor tests and validated the change of elastic wave velocity ratio when the area around excavation face became unstable. Second, we executed excavating test in embankment buried a steel pipe used in real underpass construction and confirmed the same tendency. As a result, we clarified that destabilization of around excavation face caused by excavation is detected by focusing on the elastic wave velocity ratio.