JPH0280713A - Removal anchor method - Google Patents

Abstract

PURPOSE:To increase strength of adhesion and to improve economy in execution of work by inserting anchor cables, wrapped with a corrugated sheath, into an anchor hole, and by injecting external and internal fixatives therein. CONSTITUTION:Anchor cables, wrapped with a corrugated sheath 12, are inserted into an anchor hole 15. Then external fixative 16 is injected between the anchor hole 15 and the corrugated sheath 12, and internal fixative 17 is pressure-injected to the inside of the corrugated sheath 12. At the injection, the pressure applied to the internal fixative 17 is concentrated to the center of a center core 1, thereby area of adhesion is enlarged and the strength of adhesion is increased. After the lapse of a fixed curing time, tension is given to a prestressing steel 5 and the steel is anchored. Then, an anchor anchoring the anchor cables is removed and only the center core is pulled out. After this, a set of prestressing steels 5 is detached from the internal fixative 17 and is pulled out.

Description

[Detailed description of the invention] <Industrial application field> The present invention is used for earth retaining work, construction of retaining walls of ports, etc.
Regarding removal anchor construction method.

<Prior art> Currently, as a removal anchor, there is a core-type removal anchor in which a prestressed steel material is placed on the outer periphery of a rod-shaped body called a center core, and the prestressed steel material is easily removed after the center core is extracted during anchor removal. .

The structure of the conventional core-type removable anchor will be briefly described based on a partial cross-sectional view of the anchoring length portion of the conventional core-type removable anchor shown in FIG.

That is, a center core b having a plurality of grooves a is located at the center of the fixing body, and a core cover C covers the surface of the center core b.

A PC steel material d for core removal is inserted into the center hole of the center core b and fixed with resin.

In each groove a of the center core b, there are two P for fixing.
C steel material e is housed, and its outer periphery is restrained with binding tape or the like.

<Problems to be Solved by the Invention><B> When the fixing material i is injected into the anchor hole g, the fixing material l is difficult to enter into the gap between the PC steel material e for fixing, and the groove a and the PC A gap j is formed between the steel material e and the steel material e.

Therefore, the existence of the gap j is a major factor that inhibits the improvement in the strength of the anchor, which is determined by the adhesion area of the anchoring material i and the PC steel material e.

<Opening> As a method for injecting the fixing material i into the gap j, a method of pressurizing and injecting the fixing material i can be considered.

However, as the injection pressure of the fixing material i increases, the degree of penetration into cracks in the anchor hole g and geologically weak areas increases, so it is still difficult to make the fixing material i penetrate into the gap j.

Therefore, this method only wastes the fixing material i and is not suitable for practical use.

<Objective of the present invention> The present invention has been made to solve the above-mentioned problems.It increases the adhesion area and adhesion strength between the PC steel material and the anchor material while suppressing wastage of the anchor material, thereby increasing the proof stress of the anchor. You can improve your
The purpose is to provide a removal anchor construction method.

<Structure of the Present Invention> An embodiment of the present invention will be described below, and its basic structure will be explained using a core type removable anchor as an example.

<A> Center core (Fig. 1, Fig. 3) Center core 1
has a plurality of continuous grooves 2 on the circumferential surface, similar to the conventional type.

The center core l is made of synthetic resin because it forms a hollow hole that is effective for cutting the adhesion edge of the PC steel material for fixing when removed.

The surface of the center core 1 is covered with a core cover 3 by applying a grease-like lubricant.

A PC steel material 4 for core extraction is inserted into the center hole of the center core 1 and bonded with resin.

The center core 1 is installed in the range of the fixing length part.

<Exposure> PC steel material (FIGS. 1.2 and 4) As the PC steel material 5 for fixing, stranded PC steel wires are used, and two wires are arranged in each groove 2 of the center core 1.

The 5 groups of PC steel materials for fixing are restrained using binding tape 6, spacers 7, and the like.

A cleaning hose is located inwardly of the five groups of PC steel materials over the range of the free length in a removable state.

<C> Tube (Fig. 1.2) A cylindrical tube 9 is sheathed over the free length of the fixing PC steel material 5.

A boundary seal 10 is formed at the boundary with the fixing length by injecting asphalt or the like to prevent the fixing material from entering.

<2> Injection hose (Fig. 2) Only one of the eight PC steel members 5 is replaced with an injection hose 11.

The injection hose 11 is a hose for injecting the fixing material into the corrugated sheath 12, and the tip of the injection hose 11 is opened at the tip of the fixing length.

<E> Corrugate sheath (Fig. 1) The corrugate sheath 12 is a cylindrical body that covers the entire length of the anchor.

After the tip of the corrugated sheath 12 is sealed with a water stop material 13, an end cap 14 is attached.

<Effect> Next, the construction method of the removal anchor will be explained.

[Anchor fixing procedure] (Fig. 1.2.4) <A> Anchor cable insertion An anchor cable covered with a corrugated sheath 12 is inserted into the anchor hole 15.

<Port> Injection of fixing material An external fixing material 16 such as cement paste is placed between the anchor hole 15 and the corrugated sheath 12 over the range of the fixing length.
inject.

Next, insert the corrugated sheath 1 from the base end of the injection hose 11.
The internal fixing material 17 is injected into 2 under pressure.

Then, as shown in FIG. 4, the pressurizing force of the internal anchoring material 17 in the anchoring length section acts to expand toward the hole wall side of the anchor hole 15, but since it is restrained by the corrugated sheath 12, the center core 1 Concentrate towards the center.

Therefore, the internal fixing material easily goes around the back side of each PC steel material 5 for fixing, and the adhesion area of the PC steel material 5 and the internal fixing material 17 is increased compared to the conventional case.

Further, the adhesion area between each of the fixing PC steel materials 5 and the internal fixing material 17 increases, and the adhesion strength also increases due to the pressing force of the internal fixing material 17.

Further, if a gap exists between the center core 1 and the core cover 3, since the core cover 3 is pushed toward the center of the center core 1, this gap can be eliminated and the two can be brought into close contact.

The pressing force of the internal fixing material 17 acting on the PC steel material 5 can be applied artificially by injection pressure from the injection hose 11, or by using the gravity of the internal fixing material 17.

The former method is suitable for upward-facing anchors, and the latter method is suitable for downward-facing anchors.

<C> After cleaning the inside of the tube 9 using the free length cleaning hose, the inside of the tube 9 is filled with anti-rust oil.

Then pull out the cleaning hose.

<2> Tensioning and Fixing After a predetermined curing period, the base end of the PC steel material 5 is tensioned and fixed using a tensioning jack.

The tensioning method and fixing method of the PC steel material 5 are the same as the conventional method.

[Anchor removal procedure] <A> Pulling out the center core (Fig. 5) Remove the fixing device that fixes the anchor cable and release the fixation of the PC steel material 5.

Next, the PC for core extraction exposed outside the anchor hole 15
A pulling force is applied to the steel material 4 to pull out only the center core 1.

A hollow hole 18 having the same shape as the center core 1 is formed in the fixing length portion after the center core 1 is pulled out.

<Opening> Pulling out the PC steel material (Fig. 6) Applying a pulling force to the base end of each PC steel material 5, attach the internal fixing material 17.
Cut out the edges of 5 groups of PC steel materials and pull them out.

Since the 5th group of PC steel materials has lost the center core 1 which is the supporting member, the extraction force acts in the convergence direction and the internal anchoring material 1 is easily removed.
You can divorce from 7.

<Other embodiments> The corrugated sheath 12 may be provided only over the fixing length portion.

Further, instead of the corrugated sheath 12, a sheath having the same diameter and no unevenness may be used.

Furthermore, if the injection #≠claw chip 11 for injection of the internal fixing material 17 is disposed between the PC steel material 5 for fixing and the corrugated sheath 12, the PC steel material 5 can be prevented from missing.

<Effects of the Present Invention> Since the present invention is as described above, the following effects can be obtained.

<A> In the core type removable anchor, the presence of the corrugated sheath restricts the direction in which the pressing force of the fixing material filled inside the sheath acts in the axial direction of the anchor, so the PC steel material for fixing This makes it easier for the fixing material to go around to the back side.

Therefore, the adhesion area and adhesion strength of the fixing material and the PC steel material for fixing are increased, and the yield strength of the anchor is improved.

<Exposure> In the case of core-type removable anchors, even if there is a gap between the center core and the core cover that covers it, the pressure of the fixing material acts in the direction to eliminate the gap, so the adhesion between the two is maintained. I can figure it out.

<C> Since the fixing material filled inside the sheath can be prevented from leaking and penetrating into the wall of the anchor hole, a good anchor grout can be ensured and the economical efficiency of construction can be improved.

<2> The sheath exhibits a rust prevention function.

Therefore, it can fully respond to the recent trend of lengthening the temporary installation period of anchors.

<E> It is easy to apply to known removable anchor construction methods.

(f) Splitting of the cured fixing material can be suppressed.

[Brief explanation of the drawing]

Fig. 1: An explanatory view of one embodiment of the present invention, which is a longitudinal cross-sectional view of a core type removable anchor Fig. 2: A cross-sectional view taken along ■-■ in Fig. 1 Fig. 3: A perspective view of an anchor cable Fig. 4 Figure: Partial enlarged view of the fixing length part during fixing No. 5.6
Figure: Explanatory diagram when removing the anchor Figure 7: Partially enlarged view of the fixed length of the conventional removal anchor■

Claims (1)

[Claims] (1) Fabricate an anchor by covering at least the length of the fixation length with a sheath, insert the anchor into the anchor hole, fill the inside and outside of the sheath with a fixing material, and fix it in the sheath. A removal anchor method in which the pressure of the anchoring material is applied in the axial direction of the anchor when filling with material, and then the anchor is tightened and fixed.