JPS6332931B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for fixing earth retaining anchors used in civil engineering work such as subways, roads, tunnels, etc., or in construction work, and a method for recovering the same.

Generally, the steel portion of earth retaining anchors used in underground civil engineering or architectural construction work is recovered when their function as an anchor is completed. This is to ensure that by removing the steel part from the ground after using the anchor, it will not become a hindrance when underground construction is to be carried out at the same location in the future. Therefore, the earth retaining anchor must be fixed in advance with consideration for recovery. However, although the earth retaining anchor will eventually be recovered, while it is anchored in the ground it must function well as an anchor, and it must also be anchored firmly enough in the ground so that it cannot be easily pulled out. must be allowed to do so. On the other hand, when recovering it, it is desired that it can be pulled out as easily as possible, contrary to the case of fixing. This is a completely contradictory request, but in order to meet such a request,
Various inventions have been made regarding methods for fixing and recovering earth retaining anchors.

For example, in the method shown in FIG. 1a, the outermost periphery of a retaining anchor 1 made of a plurality of tensile steel members is covered in advance with a resin 2 using double-sided adhesive tape or the like. When recovering, electricity is applied to the anchor 1 through the lead wire 4 embedded in advance at the time of fixing, and the anchor 1 itself generates heat to heat the resin 2. As a result, the adhesive force of the resin 2 is reduced, and the tensile frictional resistance acting between the anchor 1 and the surrounding grout material 3 is reduced, so that the anchor 1 can be easily pulled out. Become.

Note that 5 indicates the earth retaining wall and 6 indicates the ground, which is common to other figures.

However, in the method shown here, first, since the resin 2 is interposed between the outermost side of the anchor 1 and the grout material 3, the anchor 1
The fixing force of is not a frictional resistance force obtained by acting directly between the steel material and the grout material 3, but is obtained by acting between the steel material and the resin 2 and between the resin 2 and the grout material 3. Since the frictional resistance force is caused by the frictional resistance force acting serially (or logically) on each other, there is a possibility that the frictional force between the steel material and the resin 2 or between the resin 2 and the grout material 3 If the frictional resistance force acting on one of the anchors 1 and grout 3 were to decrease, the total frictional resistance force acting between the anchor 1 and the grout 3 would be equal to the frictional resistance force of the decreased one. It will be dragged down and lowered. That is, the fixing force of the anchor 1 becomes unstable. Furthermore, when recovering, the anchor 1 is energized through the lead wire 4, but if the anchor 1 is a collection of a plurality of steel materials,
A problem arises in that it is difficult to cause the anchor 1 to generate sufficient heat to reduce the adhesive strength of the resin 2, etc., even if a large current is passed, since the current is divided into each steel material. Further, in order to pass the large current, it was necessary to prepare and lay a separate lead wire 4 in advance, which was a hassle.

In addition, the method shown in FIG. 1b involves applying a thick layer of resin 7 that functions as an adhesive to the outer periphery of the tip of the anchor 1 in advance, and embedding the resin 7 with a resistance wire 8 wrapped therein. By applying electricity to the resistance wire 8, the resin 7 is heated and its adhesive force is reduced, thereby reducing the frictional force acting between the anchor 1 and the grout material 3, making it easier to pull out. be. In this case as well, as described in FIG. 1a, since the anchor 1 and the grout material 3 are not directly frictionally engaged, a problem arises in that it is difficult to obtain a sufficient fixing force.
Further, in this case, the resistance wire 8 must be wrapped in advance while being embedded in the resin 7, which is a lot of troublesome work.

Furthermore, the method shown in FIG. 1c is similar to FIGS.
This method does not use electric heating means, unlike the case of
d, 1e, 1f, and 1g, and by surrounding one steel material 1a in the steel material bundle in advance with edge cutting material 9 that reduces frictional resistance against force in the tensile direction, Only the steel material 1a is left in a state where it is easy to pull out. When recovering, the steel material 1a that is easy to pull out is first pulled out, and then the other steel materials 1b to 1g, which are easier to pull out due to the gaps left behind after being pulled out, are pulled out and removed. In this case, since the outside of the anchor 1 is in direct contact with the grout material, a relatively stable frictional locking state can be obtained in that respect. Since the steel material 9 makes it easier to pull out, even though the steel material 1a increases the cross-sectional area of the anchor 1, it does not contribute to increasing the tensile resistance of the anchor 1 at all. Rather, the tensile resistance per unit cross section of the anchor 1 was reduced.

This invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide stable fixing force in the fixing state, while also being able to be easily recovered. Moreover, it is an object of the present invention to provide a method for fixing and recovering earth retaining anchors, which can minimize troublesome or troublesome preparation work prior to using the anchor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 2 shows the anchorage and recovery state of the earth retaining anchor 10 according to the present invention.
It is inserted loosely into an anchor hole 11 provided therein, and the gap between the anchor hole 11 and the anchor 10 is filled with a grout material 12 made of mortar, cement paste, etc. to form an anchor body 13. ing. The grout material 12 hardens over time after being filled, and forms a strong friction locking state with the anchor 10 after hardening is completed. As a result, the tensile force (arrow P) from the earth retaining wall 5 and the anchor head 10' is transmitted to the entire anchor body 13 via the anchor 10, and between the ground 6 and the anchor body 13, The anchor trunk body 13 is fixed without moving due to the applied frictional force,
This allows the earth retaining wall 5 to be held by the anchor 10.

Here, as shown in detail in FIG. 3, the anchor 10 includes a plurality of tensile steel members 10a, 10b,
It is composed of bundles of 10c, 10d, 10e, 10f, and 10g. Furthermore, each steel material is constituted by, for example, a strand formed by twisting a plurality of steel cables. Here, at least one of the steel bundles constituting the anchor 10, seven steel members 1 in the embodiment
One steel material 10a located at the center of 0a to 10g
is coated with resin 14, and this coated steel material 10
a to other steel materials 10b to 10b by using the resin 14.
10g, and the coated steel material 10a and the other steel materials 10b to 10g are made to resist the force P in the tensile direction by frictional force via the resin 14. Furthermore, the tip portion 10A of the coated steel material 10a is attached to another steel material 10b.
At least one piece of 10g, steel material 10e in the example
It is electrically connected to the tip end 10E of. This connection is made by using a highly conductive fastening metal fitting 1 as shown in the figure.
5, the tips of each steel material 10a, 10e 1
It can be formed by tightly connecting 0A and 10E to each other. Therefore, the anchor 10 has the following characteristics:
Before being inserted, it is assembled in the state shown in FIG. 3. At this time, in order to cover the steel material 10a with the resin 14, the resin may be applied or wrapped in a tape shape. In addition, as the resin, the above-mentioned steel material 10a and other steel materials 10b to
10g and 10 g to mutually produce a frictional resistance force against a force in the tensile direction, and the frictional resistance force is obtained by a simple frictional effect, an adhesive effect, or the like. As the resin 14, a thermoplastic resin having a relatively low softening temperature and a clear softening point, or a thermosetting resin that easily undergoes plastic deformation or destruction when heated is used.

It is to be noted that it is advantageous to use only one steel material coated with the resin 14, as is done in the embodiment, in that heat generation, which will be described later, can be performed effectively.

Now, once the earth retaining anchor 10 is fixed and its use is over, it must be pulled out and recovered, but when recovering it,
First, as shown in FIG. 2, a power source E is used to connect the base end of the covered steel material 10a and
By passing current between the base end portion of another steel material 10e that is electrically connected to each other at the tip end, the steel material 10a itself generates heat, and the frictional resistance acting through the resin 14 is reduced. After that, the coated steel material 10a is pulled out, and then the other steel materials 10b to 10g are pulled out and removed.

In the example, one steel material 10a located at the center of the steel materials 10a to 10g is coated with resin, but the present invention is not limited to this. For example, when the number of steel materials is particularly large, two steel materials may be coated. The above steel materials (not all of the tensile steel materials) may be coated,
Further, the position of the covered steel material does not have to be limited to the center.

The earth retaining anchor 10 can be anchored and retrieved as described above, but what should be noted here is that first, in the anchored state,
Since the anchor 10 is in direct contact with the grout material 12, the frictional resistance between them can be made very stable and strong, and furthermore, the anchor 1
Since the steel materials 10a to 10g constituting the anchor 10, including the coated steel material 10a, are mutually resisted by frictional force against the force in the tensile direction, all the steel materials 10a to 10g increase the tensile resistance of the anchor 10. This contributes to maintaining the tensile resistance per unit cross-sectional area of the anchor 10, thereby ensuring stable anchoring force. On the other hand, when recovering the anchor 10, at least the current flowing through the coated steel material 10a is electrically insulated and isolated by the resin 14.
The current is not shunted to other steel materials, and the current is concentrated on the coated steel material 10a and the resin 1
4 can be heated efficiently.

Therefore, the coated steel material 10a, after the start of energization,
You'll be able to pull it out easily early on.

As described above, according to the method for fixing and recovering earth retaining anchors according to the present invention, the preparation work for fixing the anchor is not so troublesome compared to the conventional method, and the anchoring state is strong and stable. A fixed state can be obtained, and on the other hand, the recovery can be carried out simply and quickly as described above.

[Brief explanation of the drawing]

Figures 1a, b, and c are cross-sectional views showing the conventional anchorage and recovery method for earth retaining anchors, respectively;
FIG. 2 is a sectional view showing a state in which the earth retaining anchor according to the present invention is fixed and recovered, and FIG. 3 is a perspective view showing only the anchor portion thereof. 5... Earth retaining wall, 6... Ground, 10... Earth retaining anchor, 10a... Covered steel material, 10b to 10g...
Steel material, 11... Anchor hole, 12... Grout material, 13... Anchor body, 14... Non-heat resistant resin, 15... Good conductive fastening hardware, E... Power supply, P... Tensile direction The power of.

Claims (1)

[Claims] 1. An earth retaining anchor is constructed of a bundle of multiple tensile steel materials, and at least one steel material located inside the steel material bundle is coated with a resin, and this coated steel material is bonded to other steel materials using the resin. The coated steel material and the other steel material are made to resist the force in the tensile direction by frictional force through the resin, and the tip of the coated steel material is electrically isolated from the other steel material by at least one of the other steel materials. The earth retaining anchor thus configured is electrically connected to the tip of the book and fixed in the ground via grout. Electricity is passed between the coated steel material and the proximal end of another steel material that is electrically connected to each other at the distal end, thereby causing the steel material itself to generate heat. A method for fixing and recovering earth retaining anchors, which comprises reducing the frictional resistance acting through the resin, then pulling out the coated steel material, and then pulling out and removing other steel materials.