Evaluation of geological conditions ahead of TBM tunnel using wireless seismic reflector tracing system

The purpose of our work was to develop a new survey system which can evaluate a geological condition ahead of a TBM tunnel face accurately and rapidly, and to apply this system to an actual tunnel site to verify its effectiveness. The authors have compared their new wireless seismic reflector tracing system with the conventional system. The results showed that the wireless system made it possible to conduct the survey with optimal positioning of sources and receivers even in narrow and crowded TBM tunnels, and that coupling noise was eliminated, thereby allowing more accurate exploration. Furthermore, it is confirmed that it would greatly reduce the time and effort required for preparation and removal work, allowing more economical surveys.