ABSTRACT
The Takatoriyama Tunnel in Japan is a twin tunnel approximately 3.9 km long with two lanes in each direction. The boring system is a full-face excavation with the use of a computer-controlled drilling jumbo, blasting and an automated shotcreting machine. The geometry for the surface bored through blasting without support and the geometry of the surface of the shotcreted side wall are measured from the cutting face with a laser scanner. The blasting pattern will be corrected with reference to the difference from the planned excavation face, and the difference determined from the planned shotcrete surface, then shotcrete will be placed on overbreaks to smooth the concrete surface. The face will be a hemisphere, an excellent face shape, and efficient in forming a sturdy ground arch. For weak ground, the support structure will be ring shaped. By closing the full face earlier, the project will establish mechanical stability.
