Tunnel boring machine is one of the accepted methods for infrastructural projects for tunnel ventilation or surge shaft in hydroelectric power projects. It is also a widely used technology in the installation of production and ventilation shafts and ore passes for mines. For large diameter inclined shaft boring, there are two solutions: Full-face blind shaft boring machine (FM) and Shaft reaming machine (RM) . In the latter case the excavated muck falls through the pilot hole to a lower level. The pilot hole of a small diameter can be also excavated with a raise-boring machine. Through the careful and comprehensive discussion, a RM was found to be appropriate for our target project (Omarugawa hydroelectric power project) . In the development process, very valuable data taken in former Kazunogawa hydroelectric power project were carefully examined and necessary modifications were done to a new machine for Omarugawa. Special care was taken in designing the cutterhead to optimize the shape for best cutting efficiency and muck removal performance.
1. Open type cutterhead for lightweight machine and easy access to machine parts and tunnel wall.
2. Cone-shape cutterhead for optimum disc cutter arrangement, good face stability and efficient muck removal.
3. Two vertical supports in pilot and reamed shafts for flexible direction control and excellent maneuverability.
Finally, it should be noted that the developed machine had successfully completed the inclined shaft without significant troubles.