Takatoriyama tunnel has 2-lane cross section and is bisected 511m of mountain area and 732m of urban area. In the urban part, there is a large intersection where main tunnel (170m²), meets a ventilation duct tunnel (110m²). The construction works were successfully carried out based on observational construction method and 3-dimensional analysis. Umbrella method which injecting long steel pipe around top heading of tunnel before cutting and the side drift tunneling method were adapted.
In this paper, the authors discuss the design methodology they adapted to the large intersection and evaluate the effect.