2011 年 6 巻 1 号 p. 23-31
This paper describes the tunnel seismic reflection survey which has been developed by the authors in order to three-dimensionally detect geological conditions such as faults, fractured zones and geological boundaries ahead of a tunnel face using reflected seismic waves. In addition, the applicability and the accuracy of a result of this system have been validated by comparing with geological observation results at a tunnel face and the result of the drill logging system. This surveying system is called Three-dimensional Seismic Reflector Tracing System (TRT). TRT creates a 3-D isometric map of geological structures 100-150 m ahead a tunnel face and up to 30 m around a tunnel alignment. Kajima has applied TRT to about 100 times since its introduction in February 1999 to predict rock conditions ahead of tunnel faces. The images produced by TRT have been used satisfactorily to manage the risk caused by encountering unforeseen geological conditions.
