JPH09143991A - Ground anchor construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of large stress locally in an anchor body and preclude initiation of detrimental crazing. SOLUTION: A PC steel wire 4 is inserted into a cylinder 6 filled with grout 7 to form a fixing material, which is inserted into an anchor hole 1. Grout 2 is put fully in this anchor hole 1 and left hardening, and the tail of PC wire 4 led out from the opening 1a of the anchor hole 1 is tightened and fixed. A plurality of PC wires 4 having differently long fixation parts 16 are inserted in the cylinder 6, and at least one of them is folded in U-shape.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a ground anchor construction method.

[0002]

2. Description of the Related Art Generally, in a tension type ground anchor method, as shown in FIG. 8, a tension member 22 is inserted into a grout 21 in an anchor hole 20 and, after the grout 21 is hardened, an opening portion of the anchor hole 20 is formed. The rear end portion of the tension member 22 led out from 20a is tensioned and fixed by a predetermined tension force. This ground anchor method is a tension material 2
The tensile stress near the boundary between the free length portion 23 and the fixing length portion 24 of No. 2 was large.

[0003]

However, there is a drawback that harmful cracks are generated in the anchor body in the portion where the tensile stress is large, and the anticorrosive effect on the tension member of the grout is lost.

The present invention has been made in view of the above problems, and an object of the present invention is to prevent a large stress from being locally generated in the anchor body so as to average the stress over the entire length and to be harmful to the anchor body. It is to prevent cracks from occurring.

[0005]

[Means for Solving the Problems] A means for solving the above problems is to insert a fixing material formed by inserting a PC steel wire into a cylinder filled with grout into an anchor hole, and insert the fixing material into the anchor hole. In the ground anchor construction method in which the rear end of the PC steel wire led out from the opening of the anchor hole is tensioned and fixed after filling the grout and hardening it,
It is assumed that a plurality of PC steel wires having different fixing lengths are inserted into the cylindrical body and at least one of them is bent in a U-turn shape, and the PC steel wire has a plurality of side wires around the core wire. Which is a twisted PC steel wire, a synthetic resin-based coating inner layer is formed on the outer circumference of the core wire and the side wire, and a coated middle-layer cylinder and a coating outer-layer cylinder are formed on the outer circumference of the coating inner layer,
A lubricant is interposed between the coated middle-layer cylinder and the coated outer-layer cylinder, the cylindrical body is formed by spirally winding a wire rod, and the cylindrical body is formed of synthetic resin, and the outer peripheral surface thereof is formed. It is assumed that the spiral groove is formed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of the ground anchor construction method of the present invention, and (1) of FIG. 2 is A of FIG.
-A line sectional view, (2) is the same BB line sectional view, (1) of FIG. 3 is a front view of PC steel wire, (2) is CC line sectional view of (1), (3) Is a sectional view taken along the line D-D, and FIGS. 4 and 5 are sectional views of the fixing material.

In the ground anchor construction method of the present invention, the fixing material 3 is inserted into the grout 2 in the anchor hole 1 and after the grout 2 is hardened, the opening 1a of the anchor hole 1 is formed.
The PC steel wire 4 of the fixing material 3 led out from the outside is tensioned and fixed by a predetermined tension force.

In the fixing material 3, a grout 7 is filled in a cylindrical body 6 in which a steel wire 5 is closely contacted without a gap and is spirally wound, and a tip of a PC steel wire 4a bent in a U-turn shape on the grout 7. And a tip portion of the other six PC steel wires 4b are inserted and formed, and these PC steel wires 4a and 4b are bound by a spacer 8.

As shown in FIG. 3, the PC steel wire 4 is a coated middle layer tube made of synthetic resin by a synthetic resin extrusion molding means on a PC steel stranded wire 11 in which a plurality of side wires 10 are twisted around a core wire 9. 12 and a coated outer layer tube 13 are provided, a lubricant 14 such as grease is interposed between the coated middle layer tube 12 and the coated outer layer tube 13, and a synthetic resin powder paint is applied to each outer periphery of the core wire 9 and the side wire 10. The coating inner layer 15 is formed by fusion and adhesion.

Further, a fixing long portion 16 is formed at the tip of each of the PC steel wires 4a and 4b, in which the coated middle layer cylinder 12, the coated outer layer cylinder 13 and the lubricant 14 are peeled off to expose the coated inner layer 15.

Since the core wire 9 and the side wire 10 of the fixing long portion 16 are completely rust-proofed by the coating inner layer 15, no rust is generated, and the adhesion with the grout 7 is stronger than that of a bare PC steel wire. Exert.

The fixing long portion 16 is formed so that the U-turn-shaped PC steel wire 4a is the shortest, and the remaining six PC steel wires 4b are a little longer than the U-turn-shaped PC steel wire 4a in pairs. Has been formed. (1) of FIG. 7 is a conceptual diagram of the PC steel wire 4, and the PC steel wires 4b other than the U-turn-shaped PC steel wire 4a are present in pairs.

Further, (2) of the figure shows a stress distribution diagram of the anchor body 18 with respect to the muscle tension of the PC steel wire 4, showing the PC steel wire 4b having a long adhesion portion in order from the top. There is. In both cases, the largest compressive force (+) and tensile force (-) act on the boundary between the coating portion and the adhesion portion, and the largest compressive force ( +) Occurs.

In this way, the boundary between the fixing long portion 16 and the free length portion 17, that is, the boundary between the covering portion and the adhering portion is formed at the anchor body 1.
8 is dispersed and arranged, the tensile stress can be dispersed over the entire length of the anchor body 18 as shown in (3) of FIG.

When each of the PC steel wires 4a and 4b is tensioned by a predetermined tension force, the tubular body 6 in the free length portion 17 expands outward by the Poisson's ratio, so that the pullout resistance from the anchor body 18 increases.

As the grout 7 in the cylindrical body 6, a resin-based grout in which a thermosetting synthetic resin such as an epoxy resin, a vinyl ester resin or a polyester resin is mixed is used, and the grout 7 is restrained by the cylindrical body 6. Strength increases as a result.

In FIG. 7, the cylindrical body 6 is integrally formed of synthetic resin, and a spiral concave groove 19 is provided on the outer surface thereof, and the outer surface is formed in an uneven shape. As a result, the anchor body 1
The fixing force with No. 8 becomes stronger, and the pull-out resistance further increases.

In an example of the form of this embodiment,
One of the PC steel wires 4 is a U-turn-shaped PC steel wire 4a, but if necessary, for example, if the length of the fixing long portion 16 of the PC steel wire 4 is insufficient, two, three, or all. You can also make a U-turn.

[0019]

EFFECTS OF THE INVENTION A plurality of PC steel wires having different fixing lengths are inserted into a cylinder filled with grout, and at least one of them is bent in a U-turn shape, so that tensile stress is reduced. Since it can be dispersed over the entire length of the anchor body, cracking can be prevented.

By inserting a plurality of PC steel wires having different fixing lengths into the cylinder and bending at least one of them into a U-turn, a U-turn of the U-turn PC steel wire is formed. A compressive stress can be generated in the part.

The PC steel wire is a PC steel stranded wire in which a plurality of side wires are twisted around a core wire, and a synthetic resin-based coating inner layer is formed on the outer circumference of the core wire and the side wire, and a coating middle layer is formed on the outer circumference of the coating inner layer. By forming the cylinder and the coated outer layer cylinder and interposing the lubricant between the coated middle layer cylinder and the coated outer layer cylinder, the coated middle layer cylinder is made of a material that does not weld to the inner coating layer and is easily peeled off. Further, the peeling work of the tip portion becomes easy, and the fixing long portion can be easily formed.

The PC steel wire has a fixing long portion formed by separating the coated middle layer cylinder and the coated outer layer cylinder at the tip portion, and the fixing long portion is substantially completely rust-proofed by the coating inner layer. It is possible to improve the quality without generating rust on the wire and also to improve the adhesion with the grout.

Since the tubular body is formed by spirally winding the wire rod, the adhesive strength between the anchor hole and the grout can be increased.

The cylindrical body is made of synthetic resin, and the concave groove is spirally formed on the outer peripheral surface, so that the waterproof performance can be improved and the adhesion strength between the anchor hole and the grout can be increased. it can.

[0025]

[Brief description of the drawings]

FIG. 1 is a sectional view of a ground anchor method.

2A is a sectional view taken along line AA of FIG. 1, and FIG.
FIG. 4 is a cross-sectional view taken along line B.

3 (1) is a front view of a PC steel wire, (2) is a sectional view taken along the line CC of (1), and (3) is a sectional view taken along the line D-D.

FIG. 4 is a sectional view of a fixing material.

FIG. 5 is a sectional view of a fixing material.

FIG. 6 is a front view of a U-turn PC steel wire and another PC steel wire.

7 (1) is a conceptual diagram of a PC steel wire, FIG. 7 (2) is a stress distribution diagram of the anchor body with respect to the muscle tension of the PC steel wire, and FIG.

FIG. 8 is a cross-sectional view of another fixing material.

FIG. 9 is a sectional view of a conventional ground anchor method.

[Explanation of symbols]

 1 Anchor hole 2, 7 Grout 3 Fixing material 4 PC steel wire 5 Steel wire 6 Cylindrical body 8 Spacer 9 Core wire 10 Side wire 11 PC steel stranded wire 12 Coated middle layer cylinder 13 Coated outer layer cylinder 14 Lubricant 15 Coated inner layer 16 Anchored long section 17 Long part 18 Anchor body 19 Recessed groove

Claims (4)

[Claims] 1. A fixing material formed by inserting a PC steel wire into a cylinder filled with grout is inserted into an anchor hole, and the anchor hole is filled with grout. After hardening, the anchor hole is opened. In the ground anchor construction method in which the rear end of the PC steel wire led out to the outside is tensioned and fixed, a plurality of PC steel wires having different fixing lengths are inserted into the cylinder, and at least one of them is inserted. A ground anchor construction method characterized in that the book is bent in a U-turn shape. 2. The PC steel wire is a PC steel stranded wire in which a plurality of side wires are twisted around a core wire, and a synthetic resin-based coating inner layer is formed on the outer circumference of the core wire and the side wire. The ground anchor construction method according to claim 1, wherein a coated middle-layer cylinder and a coated outer-layer cylinder are formed on the core, and a lubricant is interposed between the coated middle-layer cylinder and the coated outer-layer cylinder. 3. The ground anchor construction method according to claim 1, wherein the cylindrical body is formed by winding a wire rod in a spiral shape. 4. The ground anchor construction method according to claim 1, wherein the cylindrical body is formed of synthetic resin, and a spiral groove is formed on an outer peripheral surface of the cylindrical body.