1. Construction of tunnels
of desired cross section by
combining various circular sections
Vertical or horizontal connection of multiple circular sections
are effective in congested underground spaces.
2. Use of structurally stable circular shapes
Tunnels are basically constructed using multiple circular cross
sections. Mechanical advantage of a circular shape contributes to
structural stability of tunnels.
3. Adoption of closed slurry shield or earth pressure
balance shield tunneling
Either closed slurry shield or earth pressure balanced shield tunneling
can be adopted.
The Multi-circular-Face Shield Method places cutter heads attached
to shield machines at different longitudinal points and overlaps
them for driving tunnels of various cross sections.
It enables excavation of tunnels of cross section with width longer
or shorter than height.
Tunnels of desirable cross section therefore can be excavated where
only limited land is available or underground space is congested
Tunnel cross sections fit for the construction condition or tunnel
use can be provided efficiently.
Flexible choice of tunnel route
Connecting double or triple circular sections, or sections
of different cross sections vertically or horizontally could offer
tunnels of diverse cross section other than a circular section.
This enables simultaneous construction of upper and lower tunnels
at a site with limited land under a narrow road by vertically connecting
tunnel cross sections occupying a small area. Even in cases under
restrictions on vertical space due to existing structures, a multi-circular-face
shield method using horizontally connected cross sections can be
adopted for tunnel driving.
|| 1. Horizontal double circular
|Construction of the Kyobashi Tunnel on the
metropolitan railway line
(cross section: 12.19 m wide and 7.12 m high)
2. Horizontal triple circular shield tunneling
|Construction of Osaka Business Park station
municipal subway line No. 7
(cross section: 17.3 m wide and 7.8 m high)
|Construction in the Iidabashi
station work section in a loop on subway line No. 12
(cross section: 17.44 m wide and 8.846 m high)