1. Occupation of small space
The method provides a more economical shape with smaller unnecessary
space in the flat cross section in railway and highway tunnels than
circular shield tunneling methods.
2. Construction of tunnels of vertical and horizontal Double
circular cross sections
Flexible design is possible according to the surrounding environment
and other conditions because combinations of tunnels can be constructed
of horizontal and vertical Double circular cross sections.
3. Positioning of cutters in the same plane
Cutters of different shield machines in the same plane make cutting
torques to balance and facilitate the control of driving of the shield
machines.
4. Reduction of total cost
 Selecting
an economical cross section enables the reduction of space occupied
by shield machine and of construction depth, which leads to reduction
of total cost.
The Dot Tunneling Method is applied for an earth pressure shield
machine with interlocking spoke-equipped multiple cutters that are
positioned in the same plane to construct tunnels of double or triple
cross sections.
1. Synchronous control of cutters
Adjacent cutters rotate in the opposite directions to avoid touching
or smashing one another and are thus controlled synchronously.
2. Rolling control
Rolling of the shield machine is controlled by component force of
thrusting jack by shifting along the circumference of the machine,
and rolling control jacks placed on the longer sides of the machine.
▲zoom
3. Erector
The DOT shield machine is equipped with cantilever-arm-type
erector to erect joint and panel segments, so it provides wide working
space. |
|
DOT shield tunneling in the Rijo section of the
Hiroshima Astram line (new transportation system) 
Cross section: 10.69 m wide and 6.09 m high
Length: 850 m
Overburden: 8.3 to 5.0 m
Soil type: Silty sand, silt and clay
Construction of a curved section of the Hiroshima Astram
line (new transportation system) (radius: 135 m)
Phase-3 construction of Kikuta-gawa main sewer No. 2
in Narashino City
Cross section: 7.65 m wide and 4.45 m high
Length: Upstream: 117 m
Downstream: 586 m
Total: 703 m
Overburden: 9.9 to 2.15 m
Soil type: Fine sand, cohesive soil and humus
Construction of a utility conduit in the Ariake-kita district in
the Tokyo metropolitan area
Cross section: 15.86 m wide and 9.36 m high
Length: 249 m
Overburden: 13.5 to 17.5 m
Soil type: Diluvial cohesive soil and gravel in buried terrace
Construction of the Chayagasaka section of Nagoya
municipal subway line No. 4
Cross section: 11.12 m wide and 6.52 m high
Length: 1,007 m
Overburden: 11.5 to 32.1 m
Soil type: Sand and cohesive soil |
