| 1. |
Excavation of tunnels of arbitrary
cross section |
Selecting the cutter shape similar to excavation face enables the
excavation of tunnels of any cross section.
| 2. |
Appropriate for excavating tunnels
of large cross section |
A cutter with short turning radius requires low torque
at the cutterhead. Multiple drive motors can be integrated into a
compact unit. Thus, the shield tunneling machine can be assembled,
dismantled and transported easily. The effect is greater for larger
shield machines.
| 3. |
Long-distance excavation |
A cutter with short turning radius means short
bit sliding distance and reduces bit wear. Thus, tunnels can be
excavated the length about three times that by conventional machines.
| 4. |
Additive injection from within the
shield machine for full-face stabilization |
The cutterhead drive motor is small enough to
enable full-face soil stabilization from within the shield machine.
Soil in curved sections or in the vicinity of the tunnel can be
stabilized from within the machine.
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| 1. |
Principle of excavation |
Supporting the cutter frame eccentrically at the ends of multiple
crank shafts, and rotating the shafts in the same direction cause
the cutter to move in a circle along the inside perimeter of tunnel
cross section and create a cross section with a shape similar to the
cutter.
For stability the face, the EPB(earth pressure balanced)
method is basically employed that produced good results, for round
shield machines and is highly reliable.
During excavation, the rate of shield advance and
rotational speed of the screw conveyor are adjusted to match muddy
soil pressure to the combined total of earth and water pressures.
The cross-roof bit unique to this method enables
cutting in all directions with the rake and relief angles being
equal to each other.
Cross-roof bit
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