| 摘要 |
PROBLEM TO BE SOLVED: To improve efficiency of starting work. SOLUTION: A starting shaft 10 is provided with a reinforced concrete wall 12 whose cross sectional shape is a closed polygon. After the wall body 12 is constructed, the inside is excavated and a bottom slab is constructed. A ground improvement section 16 is formed at the outside face of the entrance 14 of a tunnel by a freezing method or the like. Thereafter, the entrance 14 of the tunnel is broken and a shield machine is advanced from the position toward an arrival shaft. An auter periphery is formed at the entrance 14 and a hollow steel box 18 is embedded to prevent placed concrete from intruding inside.
|
