JPS63184613A - Removing work of pc steel strand of earth anchor - Google Patents

Abstract

PURPOSE:To greatly reduce separating actions by a method in which an oil pressure is applied to a center-hole jack, a steel bar chuck is extended, PC steel strand is separated from cement mortar wall, and the bonding position is retracted. CONSTITUTION:When removing work is ready, oil pressures are applied to a center-hole jack 14, a steel bar chuck 15 is extended, and PC steel strand 2 is separated from a cement mortar wall 3 and the bonding position is retracted. When the jack 14 is completely extended, oil pressure is removed and the chuck 15 is restored to the original position. Oil pressure in the opposite direction is removed, and oil pressure is applied from the forward direction to extend the chuck 15. PC strand can thus be removed completely even when they are driven in great numbers.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a PC for earth anchors used in temporary mountain retaining works.
This invention relates to a method for removing PC steel strands of an earth anchor, in which the steel strands are removed from the inside of the anchor to the ground when the anchor is no longer needed.

[Conventional technology]

If you leave the earth anchor buried in the ground even after use, if another building or civil engineering work is done in the vicinity of the ground anchor in the future, the P in the anchor will be damaged.
C-steel strands often become obstacles to construction work.

Therefore, in recent years, many methods have been implemented and proposed to remove cotton from used PC steel. Typical construction methods include the thermocrusher construction method, free gripping construction method, and sliding wedge construction method.

[Problem that the invention seeks to solve]

However, many of the removal methods currently in use are
Because the removal methods have some drawbacks: - When tens to hundreds of earth anchors are driven in the field, some of them become irremovable, making it extremely difficult to remove every single one of the PC steel strands. It becomes difficult. Furthermore, there are methods that require a long time to remove and are costly.

Therefore, an object of the present invention is to provide a removal method that solves the above problems.

[Means for solving problems]

In order to achieve the above object, the present invention arranges a core material made of a physically and chemically removable material at the center of the earth anchor, and provides appropriate longitudinal grooves on the outer periphery of this core material to arrange PC4jl stranded wires. After binding and assembling the anchor, inserting it into the borehole and filling it with cement mortar and solidifying it, use it as an anchor. When removing the PCJliil stranded wire after use, part or all of the core material is physically and chemically removed to make the PC steel strands protrude into the cavity, and then
A wire stranded from PCffA is passed through the vicinity of the center of the force applying body, and while being pushed into the above-mentioned cavity, tension is simultaneously applied to the wire stranded from PCffA to draw the wire stranded from PCffA to the center of the cavity and removed.

In the present invention, physical and chemical removal refers to the following.

In other words, the core material ■ Remove by dissolving with some kind of solvent.

■ Apply heat to dissolve and disappear.

■ Ignite and burn down.

■ Physically remove by cutting with boring etc.

It refers to things, etc.

Examples of materials that satisfy any of the above requirements include expanded polystyrene, rubber, and cardboard.

Additionally, the tension applied to the PCI strand can be applied at the same time as the force is pushed in, for example, by installing a reaction force device between the PC steel strand and the force applying body and operating the jack provided in the device. .

If a rotational force or an impact force is applied at the same time when pushing the force applying body, the peeling force of the PCE stranded wire can be increased with a small amount of force.

[For production]

If the PCli strands are arranged in the longitudinal groove of the core material, some of the PCli strands will protrude into the cavity when the core material is removed, and the PC steel will exert an action force that causes the cotton to peel off from the cement mortar wall. is significantly reduced.

In addition, a space is created by the force applying body to draw the PC steel stranded wire near the center of the anchor.

The core material used to create such spaces is generally inexpensive, so the cost of earth anchors can be reduced, and since conventional equipment such as jacks can be used, removal costs can be reduced. .

Therefore, in the present invention, a core material that can be lost or removed is placed inside the earth anchor, and removed by the various methods described above during anchor removal work.

Next, the PC steel stranded wire exposed as a non-fixed part is passed near the center of the force applying body, and is inserted into the cavity above the fixed part. After that, in the above ground part, a reaction force device is installed between the PC steel stranded wire and the push rod that applies the force to the force applying body,
Add force by jerking. 'With this applied force, a pulling force acts on the PCI stranded wire and a pushing force acts on the pushing rod, so that the force applying body is pushed into the cavity of the fixing section. At this time, part of the tensile force becomes a centripetal force and draws the PCa strands near the center of the anchor. While the centripetal force is greater than the adhesion force of the cement mortar, the PC steel strands are peeled off from the cement mortar wall, and the adhesion position retreats until a new balance is established.

By the way, the stroke of the jack cannot generally be said to be long compared to the length of the anchor fixed portion. Therefore, when the jack is fully extended, it is necessary to return it and move it forward.However, this kind of repetition is generally done using a one-way wedge, so it does not take much time to reset, which speeds up the work. It is not a hindering factor.

Moreover, in addition to the above-mentioned tensile force, a rotational force may be applied to the force applying body. The rotational force is a force that pulls the PC steel strands to the center of the torsion anchor at the center of the cavity, so a large peeling force can be obtained with a small tensile force, further speeding up the work. Also,
When this rotational force is applied through rocking, an impact force is generated, so
It will be even more advantageous.

〔Example〕

Examples will be described below with reference to the drawings.

The figure shows the structure of the earth anchor and removal device used in the present invention, and the order of explanation will be first to describe the earth anchor and then to the removal device.

Earth anchor A1, especially what is called a removable anchor, is composed of a fixed part a and a free length part like a general anchor, as shown in Fig. 7, but it differs from a permanent anchor in that it is removed after a certain role has been fulfilled. The purpose is to remove all the PC steel stranded wires attached to the anchorage part a so as not to interfere with other buildings. Since this removal and the fixation of the PC steel strands are contradictory factors, even a minor defect may cause the intended purpose to not be achieved, and some ground anchors may not be able to be removed. . Many of the failures of conventional removal methods are due to the complexity of their mechanisms.

In the present invention, a core material 1 made of a physically and chemically removable material is placed at the center of the earth anchor, and a required number of PCI 4 stranded wires 2. . . ., it is structurally simple, and the method is also simple, so there is no such fear as mentioned above.

The core material 1 may be any material that can be removed physically or chemically, but when it is removed, PC! iii Materials that cause excessive damage to the stranded wire 2 are less preferred.

Chemically removable materials include those that dissolve in certain solutions or heat, and those that are destroyed by ignition, and physically removable materials include those that can be cut or crushed. .

A typical material that meets these requirements is Styrofoam, but this type of material is inexpensive, so
It also has the effect of reducing anchor costs. In the present invention, this kind of material is used to form the core material 1 in FIGS. 8 to 1.
As shown in Figure 0, it is formed into a cylindrical shape, and has a plurality of vertical grooves 1a on the outer periphery.
..., but it is not limited to this shape, and as shown in Figures 12 and 13, it can be formed into a rectangular or rectangular shape, with the required vertical length on the four sides. Grooves 1a, . . . may also be formed. Further, as shown in FIG. 11, the inside of the core material 1 may be made hollow 1b, or it may be made solid as shown in FIGS. 12 and 13.

In any case, the vertical grooves 1a, . . . have PC steel stranded wires 2. . . , fit it in, and tie it with spacers 4 and binding wires 5 to prevent it from coming apart to complete the fixing part a. Vertical groove 1
As mentioned above, a has the effect of making assembly easier, but its original purpose is to remove pca+stranded wire 2 when core material 1 is removed.
．． ... to protrude into the cavity and reduce the adhesion of cement mortar.

The free length part is a PC steel stranded wire extending from the fixed part a2.・
The purpose is to leave the elongation of ... in a free state and transmit the anchor load obtained at the anchorage part a to the ground, and other things remain unchanged, so generally the configuration is almost the same as that of the anchorage part a. Often configured. In the embodiment as well, in order to serve as an assembly spacer and to form a connected cavity up to the anchoring part a, a core material 1 of the same shape is placed at the center of the anchor,
PC steel stranded wire to be fitted into the vertical grooves la,... 2. ... is covered with an oil-based sheath 6 or the like to break off the adhesive force of the cement mortar 3, and then tied with a binding wire 5.

Next, a method for assembling and driving the anchor will be explained. Since the core material 1 is generally manufactured in a factory, if it is too long, it will cost a lot in terms of equipment and will often be wasted. Therefore, we decided on a standard length of 1 m and connected them with adhesive to obtain the specified length. The core material 1 may be solid, but when the cavity 1b is provided as in the embodiment, it is provided with a lid, and the cement mortar 3 is attached to the cavity 1b.
It is desirable to prevent it from flowing into the

Next, stranded PC steel wire 2. which can obtain sufficient design strength.・
... to the required number and length, arrange them along the longitudinal grooves 1a, ... of the core material 1 to be joined, and attach the anchors A.
Assemble. When assembling fixing part a, P(Jl
More cotton 2. . . are bound using spacers 4 and binding wires 5 to prevent them from coming apart, and after covering the entire free length with an oil-based sheath 6, they are tied using binding wires 5.

When the assembly is completed, earth anchor A is then driven in the same manner as before, but first, a bore hole 7 of a predetermined length is drilled at the retaining location of the retaining wall using a drilling machine, and anchor A is installed. Insert into hole 7.

After insertion, use a pouring machine to apply cement mortar 3 to 6
The material is injected under a pressure of kgf/am' from the bottom of the borehole 3 toward the opening, and allowed to cure for 3 to 8 days. After curing, use a tension jack to tighten PCB1ii.
l stranded wire 2. It is anchored to the retaining wall using an anchor head and wedge while applying a predetermined tension to...

By the way, compared to conventional earth anchors, the adhesion force of the cement mortar 3 may be somewhat reduced at the part that corresponds to the core material 1, but this reduction can be compensated for by lengthening the anchoring part a. Can be done.

When the earth anchor A finishes its role as a mount and the fixed part is dismantled from the wall, the PC steel stranded wire 2°... is removed at the same time. In the present invention, first, the core material 1 is removed. When polystyrene foam is used as the core material 1 as in the embodiment, it can be melted with a solution or heat, burnt out by combustion, or removed by boring or the like. Although any method may be selected, a physical removal method using boring will be described here.

Since the boring machine used for cutting is a styrofoam core material 1 that is very easy to cut, a simple machine such as a manual auger or a manual percussion drilling machine can be used.

These machines are placed at the center of the earth anchor A, and the rod is lowered to drill a hole in the core material 1. If shavings accumulate in the hole, pour water or blow compressed air to float them up and discharge them outside the hole while continuing boring. When such a method is adopted, a portion of the core material L that cannot be completely removed generally remains inside the earth anchor A, but the PC steel stranded wire 2.・・・
・If it does not interfere with the removal work, leave it as is.

If the earth anchor becomes a problem for a long time, remove it by flowing or inserting a solution or a heat source such as electric heat into the hole to melt it, or by igniting it and burning it out.

After forming a cavity in earth anchor A in this way,
PC steel strands 2. protrude into the cavity using the removal device seen in Figure 1a. ... will be removed.

In the present invention, the PC steel strands 2. ... while applying tension to the PC steel stranded wire 2. . . to the center of the cavity and remove it. Therefore, at least the removal device 10 used in the present invention includes a force applying body 11 that draws the PC steel stranded wire 2, . A push rod 12 that can push the body 11 into the cavity, and a PCfi stranded wire 2.・・・
・Tension is applied to the force applying body 11 via the pushing rod 12 at the same time.
It is constituted by a reaction force device 13 that applies a pushing force to.

In the following, the force applying body 11 has a size that can be inserted into the cavity, and there is a PC&'4 stranded wire 2.・
It is provided with through holes 11a, . . . through which the . The plurality of through holes 11a, . . . are arranged in a balanced manner so that unbalanced force does not act on the force applying body 11.

Since the center hole jack 14 is well known, only its outline will be described.Generally, a hydraulic drive is adopted, and a steel rod to be applied can freely move in and out of the center. Further, the steel bar chuck 15 is originally a one-way chuck provided in the hole jack 14, and its biting direction can generally be freely changed by rearranging the chuck.

The reaction force girder 16 used here is 2 degrees from the PCB...
Any structure may be used as long as it is arranged in a well-balanced manner and allows the push rod 12 to move in and out freely. Such a reaction beam 16 can also be constructed using two channel members 16a, 16a, as shown in FIG. 1b.

In the illustrated example, two channel members 16a, 16a are arranged back to back with a certain distance between them, and a pad 16b is provided at the end to prevent them from separating.

We are trying to bridge the ... and integrate them by means such as welding.

Using this reaction force girder 16, connect the PC1i4 to the wire 2. ..., insert the push rod 12 into the center of the gap 16c created between the channels, and then insert the PClli stranded wire 2
．． After distributing the ... to the left and right in a well-balanced manner, insert the wedge-shaped fixing tool 1 into the gap 16c on the back side of the reaction force girder 16.
7. ...put it in your mouth.

Next, the removal of the PC steel stranded wire 2° using the removing device 10 will be explained.

First, the core material 1 is removed by the method described above, and a cavity S is created inside the earth anchor 4 as shown in FIGS. 2 to 6, and then all the PCA+ stranded wires 2.
... is the through hole 11a of the force applying body 17.

... and insert the force applying body 11 into the cavity S using the push rod 12 to a depth that can be inserted manually. Next, while the steel bar chuck 15 is kept retracted in the above-ground part, the center hole jack 14 is passed through the push rod 12 with the chuck 15 at the top, and the reaction force girder 16 is superimposed on the center hole jack 14. Next, PC steel stranded wire 2. . . are distributed to the left and right in a well-balanced manner and passed through the gap 16c, and then the fixing tool 17. ... and fix it on the reaction force girder 16.

When preparations are completed as described above, hydraulic pressure is applied to the center hole jack 14 to extend the steel bar chuck 15. At this time, the tension is applied to the pcm twisted wire 2 via the reaction force girder 16.
．． ..., and on the other hand, a pushing force opposite to the tension acts on the force applying body 11 via the pushing rod 12. PC steel stranded wire 2. Since there is almost no elongation even if tension is applied to . P passing through the through holes 11a, . . . of the force applying body 11
C steel stranded wire 2. ... passes near the center of the cavity S and leads to the reaction force girder 16, so the PC steel stranded wire 2. A part of the tension acting on the PCE stranded wire 2. ... acts as a centripetal force that draws the wires 2. to the center of the cavity S, and the PC steel strands 2. ... peels off from the cement mortar wall 3, and the adhesion position retreats.

When the jack 14 is fully extended in this manner, the hydraulic pressure is removed and hydraulic pressure is applied from the opposite direction to pull the steel bar chuck 15, which acts only in one direction, back to its original position.

Next, the hydraulic pressure in the opposite direction is removed, and hydraulic pressure is applied in the forward direction to extend the needle bar chuck 15 as described above. Repeat this procedure until the remaining length of the push rod 12 becomes shorter.
Add a new push rod 12 and continue the above procedure. When the force-applying body 11 reaches the deepest part of the cavity S in this way, its movement is restricted, so the line 2. Excessive tension acts on..., and PCE from cement mortar wall 3
4 strands 2. ... is removed.

When applying rotational force in addition to the pushing force, a handle H is attached to the rear end of the pushing rod 12 and rotated manually. If the application of this rotational force is slowed down, the force applying body 11
It is also possible to apply impact force to In addition to the pushing force, when rotational force and impact force are applied, a large tension is generated in the PC steel stranded wire 2.
．． It acts on... and peels off easily.

〔Effect of the invention〕

As explained above, the present invention has the following effects.

■ The removable anchor of the present invention is simple both in terms of structure and method;
All CI stranded wires can be removed from the site.

■ Since the core material to be removed is a material that is easy to physically and chemically remove, such as expanded polystyrene, both material costs and removal costs are low.

■ Also, since a large removal force is not required to remove the PC steel strands, it is also an excellent method for removing long earth anchors, speeding up the work.

[Brief explanation of the drawing]

FIG. 1a is a cross-sectional view of the earth anchor and removal device showing removal of PCJ4 strands using the present invention;
Figure 1b is a perspective view of the reaction girder, and Figure 2 is from ■-■ in Figure 1a.
3 is a sectional view taken along mm-m in FIG. 1a, FIG. 4 is a sectional view along TV-rV in FIG. 1a, and FIG. 5 is taken along V-V in FIG.
6 is a sectional view taken along line Vl-VI in FIG. 1a, FIG. 7 is a sectional view of the earth anchor used in the present invention, FIG. IX-IX in Figure 7
10 is a sectional view taken along the line XX in FIG. 7, and FIGS. 11 to 13 are sectional views of the anchor fixing portion showing other examples of use. A... Earth anchor, a... Fixing part, b... Fixing part, 1... Core material, 1a... Vertical groove, 2... PCI
Stranded wire, 3... Cement mortar, 4... Spacer, 5... Binding wire, 7... Boring hole, 10...
-Removal device, 11...Applying body, lla...Through hole, 1
2... Push rod, 13... Reaction force device, 14... Center hole jack, 15... Steel bar chuck, 16...
...Reaction force girder, 16a...Channel material, 16b...
Pad, 16c...Gap, 17...Fixer, S...
-Handle with hollow core material removed. Patent applicant Nippon Soil Kogyo Co., Ltd. Earthtic Co., Ltd. Figure 11 Figure 12 Figure 13

Claims (1)

[Claims] (1) A core material made of physically and chemically removable material is placed in the center of the earth anchor, an appropriate vertical groove is provided on the outer periphery of the core material, PC steel strands are arranged, and the wires are tied together and anchored. After assembling and inserting it into the borehole and filling it with cement mortar and solidifying it, it is used as an anchor, and after use, the PC
When removing the steel strands, part or all of the core material is physically and chemically removed to make the PC steel strands protrude into the cavity, and then the PC steel strands are placed near the center of the load body. A method for removing a PC steel stranded wire from an earth anchor, characterized in that the PC steel stranded wire is pulled through the center of the cavity and removed by simultaneously applying tension to the PC steel stranded wire while pushing it into the cavity.