Because segments are integrated into one piece by
introducing prestress, joint metals can be eliminated. Also, the volume
of reinforcement to obtain the same bending performance can be largely
reduced as compared with reinforced concrete structures.
Cracking in the concrete can be suppressed by introducing
prestress. Furthermore, a segment that has excellent smoothness and
water-tightness with small deformation of the lining ring during assembly
can be achieved because radial joint gaps are very small.
For tunnels subjected to high internal water pressure,
concrete can be held in a fully compressed state by introducing
prestress, ensuring stability and water-tightness.
|| Resistance to internal pressure
The segment has an interior with little roughness
and no metal on the surface. It is highly water-tight, and cracking
can be suppressed by prestressing. It is thus suitable for a single-pass
structure without secondary concrete lining.
By using unbonded prestressing strands in the
tunnel longitudinal direction, earthquake resistance can be improved
such that the lining structure retains pliability and follows underground
deformation during an earthquake.
Segments are assembled without any bolts; only fastening
with a shield jack is required. As a result, buildability can be improved
and automatic assembly can be easily implemented.
The P&PCSL provides a lining
ring of post-tensioned prestressed concrete structure by assembling
a segmented concrete ring , giving it tension, and fastening it
by inserting a prestressing single strand into the sheath that has
already been embedded in the precast concrete segment.
Because an unbonded prestressing strand with low friction loss
between the prestressing steel and sheath is used for the prestressing
strand, sufficient prestress can be introduced by applying tension
to only one position on the whole circumference. Furthermore, by
using a combined anchoring device made of cast iron that has the
tension side and fixing side integrated into one piece (X anchor)
by embedding it in the segment, the reinforcement in the segment
can be simplified and buildability of tensioning can be improved.
|On'chigawa-Higashi Trunk Line
of Sewage System in Lower Stream of Neyagawa Basin, Sewage Pipe
(Lining Outer Diameter: 2,950 mm)
||Yao-Hiraoka Trunk Line of Sewage
System in Lower Stream of Neyagawa Basin, Sewage Pipe Construction
(Lining Outer Diameter: 3,550 mm)
|Shitanoya Trunk Line of Yokohama
City Northern Treatment District Construction Work
(Lining Outer Diameter: 2,750 mm)
||Midorigaoka Rainwater Trunk Line
of Sagamihara City Public Drain Construction Work
(Lining Outer Diameter: 3,120 mm)