JPH042137B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a removable anchor construction method.

<Conventional technology> A structure that integrates the ground or bedrock by drilling a hole in the ground or bedrock, fixing one end of a PC steel wire inside the hole, and pulling the free end with strong force. An anchor exists.

For such anchors, it is important that the PC steel wire has an anchoring part where it is integrated with the ground or bedrock, and a free length part where it can be stretched sufficiently.

However, the following problems exist in the actual anchor structure.

<B> Cement paste, etc. from the fixing section may penetrate into the free length section through the twisting of the steel wire.

<B> Cement paste for anchoring has a fairly high strength, so if this cement paste invades the free length and restricts the extension of the PC steel wire, its function as an anchor will be greatly reduced. I end up.

<C> These problems described above are the same in the case of removable anchors.

For removable anchors, a major focus is on how to reliably remove the PC steel wire.

The conventional removable anchor construction method was published in Japanese Patent Publication No. 58
As disclosed in JP-A-110717 and JP-A-51-133903, a core material coated with a peelable film and having a circular cross section is placed in the center of a plurality of PC steel wires, and this core material Remove the chisel and connect it to the PC.
This method involves forming a cavity in the center of the steel wire and then removing the PC steel wire.

However, in this type of removal anchor method, the entire circumferential surface of each PC steel wire adheres to the consolidated material and the adhesion resistance is large, so a large pulling force is required to remove the tension material, and it is difficult to remove the tension material. If you try to pull it out, there is a risk that the tension material will break in the middle.

<Objective of the present invention> The present invention was made to improve the above points, and provides a construction method for a removable anchor that can reliably secure a free length that is important in terms of structure and strength. The purpose is to

Furthermore, the present invention provides a removable anchor that can easily and effectively create a hollow hole inside a PC steel wire arranged in a substantially cylindrical shape, and that does not require a large force to edge the tendon. The purpose is to provide

<Configuration of the present invention> Next, an example will be described.

<B> Drilling An anchor hole A is drilled into the ground or bedrock by a known method.

<B> Structure of the anchor body The anchor body is made by bundling a plurality of PC steel wires 1 and positioning the hollow hole forming material 6 in the center thereof.

The hollow hole forming material 6 is not provided over the entire length of the PC steel wire 1, but is positioned at the center of the PC steel wire 1 constituting the fixed length portion.

Then, the free end side of the first group of PC steel wires is covered with a sheath 2.
be located within.

That is, the sheath 2 is positioned so as to cover only the free length of the anchor body, and the sheath 2
The terminal end of the hollow hole forming member 6 is fixed to the first group of PC steel wires by the boundary seal portion 3 while covering the end of the hollow hole forming member 6.

This boundary seal portion 3 is formed of a flexible material such as urethane resin.

<C> Hollow hole forming material (Fig. 2) The hollow hole forming material 6 is a prismatic body made of, for example, vinyl chloride, and PC is coated on the four longitudinal sides of the hollow hole forming material 6.
A protrusion 7 is used to form a groove into which the steel wire 1 is inserted.
Set up.

Further, the outer circumferential surface of the hollow hole forming material 6 is coated with a lubricant such as grease and then covered with a thin outer circumferential film 8.

Further, a drawn steel material 9 made of PC steel wire or the like is positioned in the longitudinal direction of the central portion of the hollow hole forming material 6.

The outer periphery of the drawn steel material 9 is filled with resin S or the like to fix the drawn steel material 9 in the hollow hole forming material 6.

<D> Cleaning Hose In addition to the above structure, in the anchor used in the method of the present invention, a cleaning hose 4 and a seal inspection cord 5 for checking the seal condition are located in the free length.

The cleaning hose 4 is a hollow tube made of synthetic resin, for example.

On the other hand, the seal inspection cord 5 is simply a string-like body made of fiber or synthetic resin having sufficient strength.

The tips of the cleaning hose 4 and the seal inspection cord 5 are located on the free end side near the boundary seal portion 3.

<E> Inserting the anchor Fill the drilled anchor hole A with cement milk, etc., and insert the anchor body.

Alternatively, if a grout hose is placed inside the anchor body and its tip is exposed outside from the tip of the anchor body, cement paste can be filled from the grout hose into the empty hole. can.

As a result, as shown in FIG. 4, of the outer circumferential surface of the PC steel wire 1 exposed at the fixing length part, the circumferential surface excluding the surface that is accommodated in the groove of the hollow hole forming member 6 and in contact with the outer circumferential film 8 is Adheres with cement paste.

Anchor strength adheres with cement paste
This is secured by a part of the circumferential surface of the PC steel wire 1.

In this case, as described above, the boundary seal portion 3
There is a possibility that the cement paste will enter the space within the sheath 2 through it.

This is because torsion valleys are continuously formed on the outer periphery of the PC steel wire 1, and it is difficult to sufficiently fill the contact portions of the PC steel wires 1 with a sealing material such as urethane resin.

In this case, the presence or absence of cement paste intrusion is determined by
By pulling out the seal inspection code 5,
This can be determined by whether or not cement paste is attached to the tip.

<F> Water washing process When it is determined that cement paste has entered, pressurized water is supplied into the sheath 2 from the outer end of the cleaning hose 4.

As a result, the cement paste and the like that have entered from the boundary seal portion 3 are washed away and removed from the sheath 2 before they harden.

<G> Anchor fixation After washing with water is completed, pull out the cleaning hose 4 from inside the sheath 2 and caulk the mouth of the sheath 2.

Thereafter, when curing is completed after a certain period of time has elapsed, tensile force is introduced from the outside to finish fixing the anchor.

<H> Removal of tendons After anchor work is completed, remove the anchors.

For this purpose, first, the hollow hole forming material 6 is removed from the anchor as shown in FIG.

Since the hollow hole forming material 6 is edged from the grout material in the hole by the outer circumferential film 8, it is not restrained by the hardened grout material and can be peeled off and easily pulled out.

Therefore, a tensile force is applied to the drawn steel material 9 of the hollow hole forming material 6.

Since this drawn steel material 9 is integrally bonded to the surrounding hollow hole forming material 6 by the range S or the like, the hollow hole forming material 6 and the other hollow hole forming material 6 slip out from inside the outer peripheral coating 8.

At this time, since a lubricant such as grease is applied between the outer peripheral film 8 and the hollow hole forming material 6, the hollow hole forming material 6 can be smoothly extracted.

When the hollow hole forming material 6 is removed, a hollow hole with a large cross section surrounded by the outer peripheral coating 8 of the hollow hole forming material 6 and the plurality of PC steel wires 1 is formed.

Therefore, since the inner sides of the PC steel wire 1 and the outer peripheral coating 8 are hollow holes, the edges of the PC steel wire 1 can be easily cut and removed.

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

<B> Since a complete space can be secured in the free length, the designed tensile force can be introduced into the PC steel wire group.

<B> The state in which sufficient elongation in the free length portion is ensured can also be determined by a tensile test.

This test is a test method in which a tensile force is applied to a group of PC steel wires that gradually increases over time, and then the tensile force is decreased until it returns to zero.

With conventional anchors, even the free length was constrained, so the test results drew a hysteresis curve and were significantly different from the values determined by the calculation formula.

However, the test results obtained using the construction method of the present invention were straight lines almost in accordance with Hook's law, and the results once again made us aware of the great influence of restraint by the cement paste on the free length.

<C> The entire circumference of the PC steel wire at the anchor length is not attached to the anchoring material, but a portion of the circumferential surface of the PC steel wire is attached to the anchoring material to the extent that the anchor strength is not impaired. The adhesion area is set small.

Therefore, compared to the case where the entire circumferential surface of the PC steel wire is attached to the consolidation material, the force required to pull out the PC steel wire is smaller, and the accident of breaking the PC steel wire can be avoided, making it easier and more reliable to Steel wire can be removed.

<d> Conventionally, the anchors used in the removable anchor method have had drawbacks such as a complicated structure and increased diameter and weight.

The anchor of the present invention has a very simple structure for removal and is therefore convenient to handle.

[Brief explanation of drawings]

Figure 1: A diagram showing an example of the structure of the anchor used in the construction method of the present invention, Figures 2 and 3: Explanatory diagram when the hollow hole forming material is pulled out, Figure 4: - of Figure 1
Line sectional view, FIG. 5: - line sectional view of FIG.

Claims (1)

[Claims] 1. In a removable anchor construction method in which the tendons are pulled out after removing a hollow hole-forming member located at the center of a plurality of tendons, the method has a groove for accommodating tendons along the longitudinal direction of the circumferential surface. At the same time, a hollow hole-forming material formed by coating the entire circumference with a removable film is installed over the range of the anchor length, and the boundary with the anchor length is sealed to cover the free length of the tendon. Assemble the anchor by covering the spanning sheath and positioning the cleaning hose at the center of the tension member over the range of the free length, inserting the anchor into the anchor hole, and cleaning the circumferential surface of the tension member exposed in the anchorage length. The surrounding surface, excluding the surface in contact with the outer membrane, is attached to the solidifying material in the anchor hole, and the inside of the free length of the anchor is cleaned with a cleaning hose to secure a space. The hollow pore forming material is extracted while insulated from the binder, and then tension is applied to the tension material to peel and remove the peripheral surface of the tension material, excluding the contact surface with the outer peripheral film, from the grout material. , removable anchor method.