JPH0132332B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a construction method and a removal anchor that make it possible to remove tension members when unnecessary.

(b) Background of the technology Due to their nature, anchors must be installed at a distance from the structure, and their presence may interfere with the construction work of other structures, or their installation is only allowed during construction work. This often has to be removed.

For this reason, it is expected to develop an anchor that can be easily removed when unnecessary, and whose construction is not complicated by making removal easy.

(c) Conventional technology and problems Conventionally, when constructing an anchor, a steel rod whose surface was coated with grease or the like to form a surface film was temporarily buried inside the anchor, and when the anchor was no longer needed, it was buried. The anchor was pulled out and gunpowder was poured into the hole left behind to destroy the anchor, or water, oil, etc. were injected under pressure to split the anchor, and the tensile material was pulled out and removed. −8251).

However, when injecting water, oil, etc. under pressure, this method does not destroy the entire length at the same time, and the hardenable material is locally destroyed and the fluid such as water, oil, etc. It was not possible to destroy it along its entire length because it leaked from that part and the pressure decreased. In addition, the temporarily buried steel rod must first be pulled out, but the steel rod may become fixed to the anchor due to the surface film, and it is difficult to say that it can be easily removed.

The example shown in FIGS. 8 and 9 is an improved version of this means that is currently most commonly used (Japanese Patent Publication No. 54-22007).

This example is characterized by using a hollow material a.

The anchor is formed by pouring a hardening material d such as mortar cement into a hole c dug in the ground b. The tensile material e, which is directly or indirectly connected to the earth burial or structure, is a prestressed steel rod or steel cable, and is placed in the hole c before placing the hardenable material d, or the hardenable material It is installed by inserting it into the curable material d after the casting of d and before its hardening. The hollow member a is installed by the same means as the tensile member e. A plug f is provided at the lower end of the hollow member a to prevent the curable material d from flowing into the hollow member a. The tensile material e and the hollow material a are generally installed at the same depth in the created hole c, but due to the anchoring strength of the curable material d, the hollow material a is shallower than the tensile material e. In some cases, you can get away with it.

In order to remove this anchor, a disabling measure such as gunpowder is put into the hollow member a and the hardenable material d is destroyed by explosion or the like, and the hardenable material d
The fixing force of the tensile material e is reduced, and the tensile material e is pulled out and removed using jacks or the like.

According to this method, the work of pulling out the temporarily buried PC steel rod is omitted, and there is an advantage that the removal work can be performed extremely easily.

However, since gunpowder or the like is used to reduce the fixing force of the curable material d to the tensile material e, the work is dangerous, and the tensile material e may be damaged when the curable material d is destroyed. This sometimes made it difficult to completely pull out the tensile material e.

(d) Purpose of the Invention The present invention has been made in view of the problems of the conventional examples described above, and its purpose is to replace the method of destroying the anchor body and removing the tensile material. The purpose of this method is to remove the tensile material by peeling it off while twisting it toward a cavity formed in the center of the anchor body.

(E) Structure of the Invention In order to achieve the above object, the present invention creates an anchor body by disposing a plurality of tensile members in a hole dug in the ground and casting a hardening material, Further, a cavity is formed in the anchor body at the time of creating the anchor body or removing the tension member, and a cavity is formed parallel to the tension member and closer to the center than the tension member, and when removing the tension member, the tension member is After being pulled in the direction of the cavity and bundled, the tensile material is twisted and peeled off.

(f) Embodiments of the invention Examples of the invention will be described below with reference to FIGS. 1 to 6.

First, as shown in FIG. 7, for example, several steel wires (12.7 mm diameter, 4 to 8 wires, 12.7 mm diameter) are placed around a polyethylene synthetic fiber rope (about 500 mm diameter) 1 to be used as a temporary burial structure. , but in this example, there are 6)
A tensile structure 4 is prepared in which the tension structures 2 are arranged at regular intervals and fixed with tape 3 at arbitrary intervals. This tensile structure 4 is inserted into a hole 5 drilled at a predetermined depth and casting angle in the same manner as in normal anchor construction, and a cement paste made of, for example, early strength cement is injected as a hardening material 6. , 1st
The anchor body 7 is shown in FIGS.

Next, steel wire 2 is attached from the anchor constructed in this way.
The following describes the process when it becomes necessary to remove.

First, the polyethylene synthetic fiber rope 1 buried in the center of the anchor body 7 is pulled out. Since the polyethylene synthetic fiber rope 1 does not adhere to the curable material 6 and the steel wire 2,
When pulled, the synthetic fiber rope itself can stretch by several tens of percent and become smaller in diameter, so it can be easily pulled and removed during removal, and no debris remains in the formed cavity. As a result, a cavity 8 is formed in the center of the anchor body 7 in parallel with the steel wire 2, as shown in FIG. The steel wire 2 is present around the side wall of the cavity 8.

In the state shown in FIG. 3, in order to peel off the adhesion between the steel wire 2 and the hardenable material 6 and remove the steel wire 2, the steel wire 2 is pulled toward the cavity 8 located in the center. The adhesion between the steel wire 2 and the curable material 6 can be peeled off with a small force.

In order to generate such a force that moves the steel wire 2 in the radial direction of the cavity 8, several steel wires 2 are twisted into one bundle as shown in FIGS. 4 and 5. In this way, the steel wire 2 can generate a force at the end 7a of the anchor body 7 to be drawn toward the cavity 8. Further, by twisting, the force increases, and the steel wire 2 and the hardenable material 6 at the end 7a of the anchor body 7 come to separate.
If this state continues, the peeling due to twisting will progress in the depth direction as shown in FIG. 6, and will eventually reach the end of the steel wire 2, and all peeling will be completed.
In this way, all the steel wires 2 can be pulled out.

In the above embodiment, the polyethylene synthetic fiber rope 1 was used as a temporary burial body when constructing the anchor, but the present invention is not limited to this. Any small material may be used. Furthermore, a synthetic resin foam may be used as the temporary buried body. Although it is difficult for synthetic resin foams to form complete cavities like the above-mentioned polyethylene-based synthetic fiber ropes, they are extremely easily destroyed by the tensile material being twisted, and the tensile material progresses in the depth direction. There is no problem in carrying out the present invention. Furthermore, the present invention can also be applied to ordinary anchors in which a cavity is formed in the center of the anchor body using a drilling machine or the like during removal.

(G) Effects of the Invention As explained above, according to the present invention, the tensile material is easily peeled off from the curable material by simply being twisted toward the center of the cavity during removal, so the anchor body is destroyed and the tensile material is removed. Compared to the construction method that removes the tensile materials, the tensile materials can be recovered safely and reliably, and the removal work of the tensile materials becomes easier.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of the removal anchor according to the present invention, Fig. 2 is a plan view thereof, Fig. 3 is a longitudinal cross-sectional view showing the state in which the temporary buried body has been removed, and Fig. 4 shows the state in which the tension member is twisted. 5 is a plan view of FIG. 4, FIG. 6 is a longitudinal sectional view showing the state of peeling of the tensile material,
FIG. 7 is an end view of the tensile structure in this example,
FIG. 8 is a plan view of a conventional removal anchor, and FIG. 9 is a longitudinal sectional view thereof. 1... Polyethylene synthetic fiber rope (temporary burial body), 2... Steel wire (tensile material), 3... Tape,
4... Tensile structure, 5... Creation hole, 6... Curable material, 7... Anchor trunk body, 8... Cavity.

Claims (1)

[Claims] 1. A plurality of tensile materials are placed in a hole dug in the ground, and a hardening material is cast to create an anchor body, and the anchor body is filled with the tensile material at the time of constructing the anchor body or the tensile material is placed in the anchor body. At the time of removal, a cavity is formed parallel to the tensile material and closer to the center than the tensile material, and when the tensile material is removed, the tensile material is pulled toward the cavity and bundled, and then peeled off while twisting the tensile material. A tensile material removal method characterized by