JPS6245378B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an in-sheath grouting method in which cement milk is injected into the sheath during construction of a breast-stressed concrete structure using a post-tensioning method.

When applying prestress to a concrete structure (for example, a bridge girder, etc.) using the post-tensioning method, as illustrated in Figure 1, a sheath 2 is buried in the concrete 1 of the structure in advance, and the concrete 1 is hardened. After that, the PC steel material 3 passed through the sheath 2 is tensioned, and its ends are connected to the female cone 4 and male cone 5.
After fixing the grout pipe 7 to the concrete 1 through a fixing device consisting of a fixing device and imparting prestress to the concrete 1, the grout pipe 7 is inserted through the through hole 6 of the male cone 5, sealed with mortar 8, and then the grout pipe 7 Cement milk is injected into the sheath 2 through the tube.

In Fig. 1, the grout pipe 7 consists only of a hose 7', and the tip of the hose 7' is inserted directly into the through hole 6, but an injection nozzle is attached to the tip of the hose 7' to grout. It is also possible to construct a tube 7 and insert the tip of this injection nozzle.

In either case, the cement milk ejected from the opening at the tip of the grout pipe 7 fills the cross section of the sheath 2 and flows forward, eventually reaching the other end of the sheath 2.
The air near the tip of the grout pipe 7 is caught between the cement milk and the fixing tool and has no place to escape, and the air stays at this part under high pressure, which may prevent the cement milk from circulating to this part.

The present invention has been made in view of the above-mentioned circumstances, and is made by inserting a grout pipe having a ventilation gap, which serves as an escape route for the air, in the peripheral wall of at least the tip thereof, into a grout hole provided in a fixture of prestressing steel material. At this time, if you grout with the ventilation gap open, cement milk will flow back into the ventilation gap, so grouting should be done with the ventilation gap closed, and just before the work is finished, open it. The part where the tip of the grout pipe is located is communicated with the atmosphere to allow the air to escape.

The present invention will be explained in more detail below.

2 and 3, the grout pipe 7 is connected to the hose 7'.
FIG. 2 is a cross-sectional view of the hose 7' in the case where the hose 7' is constructed with only two layers, and in FIG. Further, in FIG. 3, there are a number of holes 1 in the tube wall 12 of the hose 7'.
3 is provided.

In the case of Fig. 2, the inner tube 9 and the outer tube 10 can be made of ordinary tubes, but in particular, the inner tube 9 is made of a rubber hose with uneven outer surfaces, and the outer tube 10 is made of heat-shrinkable resin. The use of a tube is advantageous in terms of both the integrity of the inner and outer tubes and the formation of gaps. Also, in the case of Figure 3,
The holes 13 can be formed by burying thin tubes, or fibers such as twine having ventilation gaps may be buried at the positions of the holes 13.

The gaps 11 and holes 13 are continuous from the front end to the rear end of the hose 7', and when the hose 7' is used as the grout pipe 7 to carry out the present invention, the embodiment shown in FIG. 1 is used. After setting the hose 7', the gap 11 and hole 13 are closed by means such as tying the middle of the hose 7' with a string, and in this state, cement milk is injected into the sheath through the hose 7'. Immediately before work, the blockage is released.

Figure 4 shows the injection nozzle 14 at the end of the hose 7'.
The injection nozzle 14 has an inner and outer double pipe structure at its tip, and a gap 17 is formed between the inner pipe 15 and the outer pipe 16. When the injection nozzle 14 is inserted into the grout hole of the fixing device (the through hole 6 in Fig. 1), the tip of the outer tube 16 is located just behind the fixing device, and the inner tube 15 is located several centimeters further.
It is long and protrudes forward.

An air vent pipe 18 communicating with the gap 17 is attached to a part of the peripheral wall of the outer tube 16, and a valve 19 is provided near the open end of the air vent pipe 18.

Therefore, when carrying out the present invention using this grout pipe 7, it is necessary to close the ventilation gap 17,
Opening is performed by operating the valve 19.

As is clear from the above description, in the present invention,
Insert a grout pipe with a ventilation gap in at least the peripheral wall of the tip part into the grout hole provided in the fixing tool of the PC steel material, grout the inside of the sheath with the ventilation gap closed, and close the ventilation gap immediately before finishing the work. The opening of the grout pipe allows the part where the tip of the grout pipe is located to communicate with the atmosphere, so the high pressure air trapped in the part where the tip of the grout pipe is located is removed without causing a backflow phenomenon of the grout material. It is possible to vent to the atmosphere and perform a complete grouting operation in which the cement milk is evenly distributed throughout the injection area.

The above explanation is for the case where grouting is performed by inserting the grout tube into the grout hole provided in the fixing device of the prestressed steel material, but the same applies when grouting is performed by inserting the grout tube into the outlet that runs halfway through the sheath. The present invention is also effective in this case.

[Brief explanation of the drawing]

Fig. 1 is a sectional view for explaining the present invention, Fig. 2 is a sectional view of an example of a grout tube used in carrying out the present invention, Fig. 3 is a sectional view of another example, and Fig. 4 is a sectional view of another example. FIG. 3 is a cross-sectional view of a grout pipe equipped with a nozzle. In addition, in the figure, 1: concrete, 2: sheath,
3: PC steel material.

Claims (1)

[Claims] 1. Insert a grout pipe with a ventilation gap in at least the peripheral wall of the tip end into a grout hole provided in a fixing device of the PC steel material or into an outlet that leads halfway through the sheath, and grout into the sheath with the ventilation gap closed. . An in-sheath grouting method, characterized in that the ventilation gap is opened immediately before the end of the work, and the part where the tip of the grout pipe is located is communicated with the atmosphere.