JPS6375298A - Method of prestress introduction construction in shield tunnel - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application of the Invention The present invention relates to a construction method for introducing prestress into segments in a shield tunnel.

``Prior Art, Problems to be Solved by the Invention'' In general, concrete segments in shield tunnels are boxed out in both the ring direction and the axial direction, and are then fastened together using joint fittings at these portions.

By the way, large external forces (axial force, bending moment, shearing force) and high water pressure act on segment rings in undersea tunnels, etc., but when using fittings that can accommodate these external forces during construction, the box cutouts must be large and deep. For this reason, the box cutout portion inevitably becomes an extremely disadvantageous element in terms of strength against external forces.

In addition, there is a risk of water leaking from the joint fittings and segment joint surfaces due to high water pressure.

On the other hand, a method of introducing prestress into conventional concrete segments is also known, but at present we have not yet developed a practical method of introducing prestress that can cope with large external forces and high water pressure.

"Means for Solving the Problems" In order to solve the above-mentioned conventional problems, the present invention inserts a plurality of steel stranded wires into the segment ring in the front and back width direction, and rotates each wire around the entire circumference of the ring. It is tightened and fixed in one place, which reduces the need for tension box removal parts, fixing hardware, and tension fixing work.In addition, each tension box removal part is placed at an even position in the ring direction, and when tensioning is performed, the prestress is not biased and the tension is fixed all the way in the ring direction. Prestressing can be introduced evenly around the circumference, ensuring water-tightness against high water pressure, and the joint fittings used in conjunction with it are made smaller to reduce boxing defects and adapt to large external forces. This is a proposal for an introduction method.

"Embodiments" Below, embodiments of the present invention shown in the drawings will be described.
The figure shows a case in which a -ring is constructed using eight arc plate-shaped concrete segments 1. Each segment l has eight wooden rings arranged along the arc at predetermined intervals in the front and back lJ force direction. The direction sheath 2 is embedded symmetrically with respect to the center of the front and rear widths.

And, on the inner surface of each segment l constituting the above-mentioned ring, one tension box extraction part 3 is provided which opens any one of the eight ring-direction sheaths 2 without overlapping. When a segment ring is constituted by segments l, each tension box extraction part 3 or each ring direction sheath 2 is arranged at different positions at predetermined intervals in the ring direction (positions dividing the entire circumference into 8). has been done.

Further, an axial sheath 4 is embedded in each segment 1 in the longitudinal width direction thereof.

When constructing a shield tunnel using segment 1 with the above configuration, the segments are located symmetrically with respect to the center as shown in FIG. 3 (A: A', B: B', c: c', D: D
' ) Remove the tension box extraction part 3 of the ring direction sheath 2.2 from the first
As shown in the figure, the segment rings should be positioned symmetrically with respect to the center O (AGE, B:F, C:G, D:H).
) They are combined to form a segment ring in which tension box cutouts 3 are evenly distributed around the entire circumference, and construction is carried out in parallel to introduce prestress for each of these segment rings.

First, a PC steel stranded wire 6 is inserted all around the ring-direction sheath 2 connected to the segment ring in each tension box extraction part 3 by the bush-through machine 5.

In this case, the ring direction sheath 2 between each segment 1.1
．． As shown in Fig. 6, the opening end of the sheath 2 in the ring direction is shaped like a trumpet so that the PC steel stranded wire 6 can be inserted smoothly even if the mutual sheath openings are slightly misaligned at the abutting surfaces of the sheaths 2 and 2. It is preferable to use a bell-mouth type sheath.

Next, using two jacks, the PC steel stranded wire 6 is simultaneously placed in the tension box extraction parts 3, 3 located at symmetrical positions.
The ring is tensioned, and each end is fixed to the front metal fitting 7. In the illustrated embodiment, tensioning and fixing work is performed four times in total at each symmetrical position for one ring. By doing this, it becomes possible to introduce prestress, which is reduced due to friction in areas far from the tensioned position, evenly in the ring direction and in the front-rear direction.

In this case, the amount of prestress introduced is preferably a value that does not open the joint surface (no tensile stress is generated on the outside of the joint surface) because the main purpose is to stop water, and it is desirable that the amount of prestress introduced is a value that does not cause the segment to become noticeable during assembly. By introducing the amount, it is possible to downsize the joint fittings during assembly.

After fixation, the cloud tube 8.8' and the air at the top end are connected to the left and right openings of the ring direction sheath 2 in each tension box extraction part 3.
Cloud extraction pipe 9f: After setting, non-shrinkage concrete 10 is filled in the tension box extraction part 3, and grout is injected into the ring direction sheath 2 from the grout pipes 8, 8'.

During this grout injection work, from the grout pipe 8.8' set at the position of each tension box extraction part 3, start from one of the grout pipes 8, which is located further away from the top end of the ring (the injection path is longer). After confirming that grout of the same quality as the injected grout has leaked from the air grouting pipe 9, it is injected into the other grouting pipe 8.

To introduce prestress in the axial direction, as shown in FIG.
' uses a segment with a fixed metal fitting 12 fixed to its tip.

The fixing hardware 12 is made of a channel steel material having a groove filled with concrete 13 on the segment tip side, as shown in Fig. 7.8.9. A recess 14 opened on the peripheral surface side is provided, and a through hole 15 through which the PC steel stranded wire 11 is inserted is provided in the solid end surface of the recess 14 so as to communicate with the opening of the axial sheath 4 .

Then, insert the PC steel stranded wire 11 into the axial sheath 4 that communicates between the segments 1.1 and 1 of the -span, fix the fixed side with the fixing bracket 16, and attach the seal cap 17. Using the jack 18, the PC steel strands 11 at symmetrical positions with respect to the center O of the ring are tensioned with the required prestress introducing force.

In this case, the amount of prestress introduced is preferably a value that does not cause tensile stress on the outside of the joint surface, as in the ring direction.

After the PC steel stranded wires 11 at other symmetrical positions are tensioned and fixed one after another in this way, TALLAUDE is injected into each axial sheath 4, and the tension side end is fixed with the fixing fitting 19 and the seal cap 17 Further, a sealing gasket 20 made of rubber or the like is attached, and the end surface of the fixed hardware 12 of the fixed side segment 1' to be assembled in the next step is closely sealed to this.

In this way, by introducing prestress in the axial direction as well, seismic strength and resistance to subsidence can be improved.

In addition, in the above construction method, the number of segments that make up the segment ring can be set arbitrarily according to the design, and the positions where tension is applied simultaneously when introducing prestress in the ring direction are not necessarily exactly symmetrical positions, but almost symmetrical positions. It is sufficient if the positional relationship is as follows.

"Effects of the Invention" As described above, according to the present invention, a plurality of ring-direction sheaths communicating with each other are provided in a plurality of arcuate plate-shaped segments constituting a segment ring at predetermined intervals in the longitudinal width direction of the segments, and the ring is constituted. For each ring direction sheath, one tension box extraction part is arranged in the segment at an equal position in the ring direction, and a PC steel strand is fed into each of the ring direction sheaths at each tension box extraction part to form a ring. By inserting the PC steel strands around the entire circumference and sequentially and simultaneously tension-fixing the PC steel strands in the two tension-box extraction parts located at symmetrical positions on the inner surface of the ring, the tension-box extraction, fixing hardware, and tension-fixing work can be reduced. In addition, since the tensioning box openings are arranged at equal positions in the ring direction, prestress can be uniformly introduced all around the ring direction during tensioning without being biased.

This not only ensures watertightness against high water pressure, but also allows the fittings to be made smaller to withstand large external forces, thereby reducing box breakage and maintaining the necessary strength against large external forces. .

[Brief explanation of the drawing]

FIG. 1 is a front view showing a segment ring constructed according to the present invention, FIG. 2 is a side view of the same, FIG. 3 is a vertical cross-sectional side view of the segment used in the present invention, and FIG. 4 is a cross-sectional front view showing a fixed state. Figure 5 is a front view of the segment ring showing the state at the time of cloud injection, Figure 6 is a partial sectional view showing the abutting shape 5g of the sheath in the ring direction, and Figure 7 is the inner surface of the tunnel showing the state of introducing prestress in the sleeve direction. FIG. 8 is a side plan view of the fixing hardware as seen from the side, and FIG. 9 is a partial longitudinal sectional front view of the fixing hardware. l...Concrete segment, 2.2...Ring direction sheath, 3...Tension box extraction part, 4...Axial direction sheath, 6.
11...PC steel stranded wire. Patent applicant: Maeda Construction Industry Co., Ltd. +7 Agent: Minoru Fujii:)
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Claims (1)

[Scope of Claims] 1) A plurality of ring-direction sheaths that communicate with each other are provided in a plurality of arcuate plate-like segments constituting a segment ring at predetermined intervals in the longitudinal width direction of the segments, One tension box extraction part is arranged in each sheath at an equal position in the ring direction, and each of the tension box extraction parts has a P in the sheath in the ring direction.
A stranded C steel wire is fed and inserted all around the ring, and the stranded PC steel wire is sequentially and simultaneously tensioned and fixed in two tension box cutout portions located at mutually symmetrical positions with respect to the center of the ring. Prestress introduction method for shield tunnels. 2) The method for introducing prestress in a shield tunnel according to claim 1, wherein the ring direction sheath is a bellmouth type sheath.