JP6779551B1 - Crimping grip and short anchor using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a short anchor in which the diameter of an anchor hole can be reduced, the total length can be easily changed, and a required elongation amount can be easily secured even with a short length, and a crimping grip used for the short anchor. SOLUTION: This is a crimping grip 1 for an unbonded PC steel stranded wire 5 having a synthetic resin coating, and the crimping grip has a cylindrical crimping sleeve 3 and a cylindrical shape, and a blade is formed on the inner and outer peripheral surfaces. The crimping sleeve is composed of an insert 4 to be inserted into a crimping sleeve, and the crimping sleeve forms an insert storage portion 3a on one side and a synthetic resin coating uptake portion 3b on the other side in the direction of the central axis. It is assumed that the covering intake portion has a radial thickness dimension smaller than the radial thickness dimension of the insert housing portion over the entire length in the central axis direction. [Selection diagram] Fig. 3

Description

The present invention relates to a crimping grip that crimps to the tip of a single unbonded PC steel stranded wire, and a short anchor that uses a tension material crimped by the crimping grip.

Lock bolts have the advantage of being easy to install and inexpensive because they are fixed by tightening nuts without introducing tension. Many rock bolts are inserted into the ground with a relatively short length, and as a countermeasure against collapse when small to medium scale collapse is predicted, or when excavating a cut slope at a steeper slope than the standard slope. Used as a surface stabilization measure.

The ground anchor uses a PC tension material to form a free length part and a fixing length part to introduce prestress. As the tension material, a so-called single unbonded PC steel stranded wire in which the outer peripheral surface of the PC steel stranded wire is coated with a synthetic resin is generally used. There are roughly two types of methods for fixing the end of the PC steel stranded wire to the member: the wedge method and the crimping grip method. Compared to rock bolts, ground anchors have the advantages that the PC steel stranded wire can easily accommodate any length, and that tension is fixed and prestress can be introduced. On the other hand, since the ground anchor requires equipment for driving the jack for tension fixing, it takes more time and effort than the lock bolt for fixing by tightening the nut.

The conventional compression type anchor is disclosed in Patent Document 1 below. In the compression type anchor described in Patent Document 1, a plurality of anchors are arranged at different depth positions in anchor bodies provided in anchor holes drilled in the ground, and tension is applied to each anchor body. A so-called U, which is an earth anchor in which a material is U-turned and wound, and its end is tension-fixed outside the opening of the anchor hole, and a reinforcing body is arranged between the fixed bodies. Turn compression distributed anchor. Each tension material is a so-called unbonded cable in which a steel wire is slidably inserted into a synthetic resin sheath via grease or the like. The anchored body shown in Patent Document 1 is also called a load-bearing body.

Further, a conventional tension type anchor is disclosed in Patent Document 2. FIG. 1 of Cited Document 2 shows a tensile dispersion type anchor, and FIG. 2 shows a conventional tension type anchor.

Japanese Patent No. 2651315 Japanese Patent No. 2655820

In the case of a ground anchor, the tip of the anchor is fixed to a predetermined depth in the ground, the tension material is tensioned by the anchor head placed outside the ground and fixed with a fixing tool, and prestress is introduced into the ground. Become. The anchor head is a tension end and the anchor tip is a fixed end, which is similar to a conventional PC structure.

Since the conventional PC structure is made of concrete, the completed PC structure is hardly deformed except for the factor of external force. On the other hand, in the case of ground anchors, the soft ground on the back of the anchor head causes minute deformation of the ground due to various unspecified factors such as loosening and runoff of the ground even after the anchor is installed. May be reduced or lost. Therefore, the current ground anchor design and construction standards stipulate that the ground anchor should be provided with a free length portion and a fixing length portion, respectively, and the free length portion should be 4 m or more. As a result, the tension material of the ground anchor can secure the required amount of elongation.

For example, if the same tension force is introduced into the A tension material and the B tension material, and the elongation amount of the A tension material is 1 mm and the elongation amount of the B tension material is 10 mm, the soft ground on the back of the anchor head shrinks and deforms by 1 mm. , The tension of A tension material is completely eliminated, but the tension of B tension material is reduced by only 1/10. For this reason, the greater the amount of elongation of the tension material, the easier it is for the ground anchor to obtain health and stability.

Although not described in the specification of Patent Document 2 because it is obvious, in the conventional tension type anchor, as shown in FIGS. 1 and 2 of Patent Document 2, the free length from the anchor head to a predetermined length A portion is provided, and the portion from the tip to the tip of the anchor is used as the fixing length portion. Here, the free length portion is a portion in which the diameter of the tension steel material is thickly expressed in the figure of Patent Document 2, and means an unbonded portion having a PE coating. Further, the fixing long portion is a portion in which the diameter of the tension steel material is expressed in a thin manner in the drawing, and means a portion of the PC steel material from which the PE coating is cut off. In such a tension type anchor, the length of the unbonded portion having the PE coating is longer than a predetermined standard so that a predetermined amount of elongation due to the tension force of the tension steel material can be obtained. As a result, the conventional tension type anchor has a problem that the total length of the anchor becomes long, which is uneconomical.

In the conventional compression type anchor, as shown in paragraph 0008 of Patent Document 1 and FIGS. 1, 2, 8, 9, and 10, an unbonded cable coated with a synthetic resin is U-turned to a fixing body (load bearing body). The tension is fixed at the wrapping and anchor head. In this case, the tension material is in an unbonded state over the entire length of the anchor, and the anchor fixing force in the ground is due to the fixing force (supporting pressure + adhesion) between the anchoring body (load bearing body) and the grout. If the free length portion is provided at 4 m or more according to the current design standard, the amount of elongation exceeding the standard can be obtained, so that the health and stability of the anchor are ensured. However, the conventional compression type anchor has a problem that the diameter of the anchor hole becomes large, which is uneconomical.

The above-mentioned lock bolt is a mechanism that simply stops slipping on the slope by the shear resistance (dowel action) of the bolt, and tension force cannot be introduced. Therefore, since the lock bolt is not unbonded, there is a problem that a free length portion cannot be provided, and because a steel bar is used, there is a problem that the length cannot be easily adjusted, and the applicable range is very narrow.

Therefore, the present invention provides a short anchor in which the diameter of the anchor hole can be reduced, the total length can be easily changed, and the required elongation amount can be easily secured even with a short length, and a crimping grip used for the short anchor. The purpose is to do.

The first aspect of the present invention is
A crimping grip for unbonded PC steel stranded wire with a synthetic resin coating.
The crimping grip comprises a cylindrical crimping sleeve and an insert that is cylindrical and has a blade formed on the inner and outer peripheral surfaces and is inserted into the crimping sleeve.
The crimp sleeve has an insert storage portion on one side and a synthetic resin coating capture portion on the other side in the direction of the central axis.
The crimp grip is characterized in that the synthetic resin coating take-in portion has a radial thickness dimension smaller than the radial thickness dimension of the insert storage portion over the entire length in the central axis direction.

The second aspect of the present invention is
A feature is that a taper is formed on the outer peripheral portion of the synthetic resin coating take-in portion in the direction of the central axis from the insert storage portion side toward the end surface on the opposite side of the insert storage portion. This is the crimping grip of the first aspect.

A third aspect of the present invention is
The crimping grip of the first aspect is characterized in that the inner diameter of the synthetic resin coating uptake portion is larger than the inner diameter of the insert storage portion.

A fourth aspect of the present invention is
Unbonded PC steel stranded wire with synthetic resin coating and
A crimping grip according to any one of the first to third aspects crimped to the end of the unbonded PC steel stranded wire.
A bottomed cylindrical tip cap into which the crimp grip is inserted,
A short anchor having a tubular shape, through which the unbonded PC steel stranded wire penetrates, and a load-bearing body arranged adjacent to the tip cap.
A female screw portion is formed on the inner peripheral portion of the tip cap on the load-bearing body side.
A male screw portion is formed on the outer peripheral portion of the load-bearing body on the tip cap side.
The tip cap and the load-bearing body are integrated by screwing the female screw portion and the male screw portion.
The crimping grip and the male screw portion come into contact with each other so as to be able to transmit stress in the central axis direction.
It is a short anchor characterized in that the unbonded PC steel stranded wire extends to the anchor head.

A fifth aspect of the present invention is
This is a short anchor according to a fourth aspect, characterized in that a spiral protrusion is formed on the outer peripheral surface of the load-bearing body.

According to the present invention, the following effects can be obtained.
(1) By incorporating a crimping grip in the tip cap screwed to the load-bearing body, it is possible to anchor (fix) to the ground without providing a conventional screw rod, and the crimping grip is rust-proof and corrosion-proof. It is the fixed end of a durable compression anchor.
(2) While the conventional U-turn compression type anchor needs to be formed of a plurality of (even) unbonded PC steel stranded wires, it becomes possible to form a compression type anchor with a single unbonded PC steel stranded wire. ..
(3) Since the anchor is formed with the synthetic resin coating on the entire length, it is easy to secure the amount of elongation even when the total length is short, and the health and stability can be improved.
(4) Even if the crimping sleeve is crimped to the end of the PC steel stranded wire with the PC steel stranded wire having the synthetic resin coating still attached, the coating is not damaged by the crimping process, and the crimping sleeve and the coating are separated. Adhesion provides water-stopping performance. In addition, it is not necessary to apply rust preventive treatment to the joint of the crimping grip, and the labor and cost of construction can be reduced.
(5) Since the PC steel stranded wire is supplied by winding, it is easy to cut it to an arbitrary length. For this reason, in a factory, it is possible to easily manufacture a tension material having an arbitrary length by cutting a PC steel stranded wire to a required length corresponding to a construction site and integrating a crimping grip and a PC steel stranded wire by crimping. it can.
(6) By crimping the anchor head with a crimping grip that attaches a screw rod to the head of the tension material, a nut is tightened using an inexpensive PC steel stranded wire in the same way as a conventional lock bolt. You will be able to fix the tension by the method of fixing the tension. As a result, the manufacturing cost of the tension fixing tool is low, the construction is easy, and the cost can be reduced.

It is a figure which shows the crimping grip which concerns on 1st Embodiment of this application, and the tip part of the short anchor using the crimping grip. (A) is a cross-sectional view of the crimping sleeve, (b) is a side view of the crimping sleeve, (c) is a side view of the insert, (d) is a cross-sectional view of the short anchor end before crimping the crimping grip, (e). ) Is a cross-sectional view of an unbonded PC steel stranded wire, (f) is a side view of the short anchor end before crimping the crimp grip, and (g) is a cross-sectional view of the short anchor end after crimping the crimp grip. h) is a side view of the end of the short anchor after crimping the crimping grip. It is a figure which shows the crimping grip which concerns on 2nd Embodiment of this application, and the tip part of the short anchor. (A) is a cross-sectional view of the crimping sleeve, (b) is a side view of the crimping sleeve, (c) is a side view of the insert, (d) is a cross-sectional view of the short anchor end before crimping the crimping grip, (e). ) Is a cross-sectional view of an unbonded PC steel stranded wire, (f) is a side view of the short anchor end before crimping the crimp grip, and (g) is a cross-sectional view of the short anchor end after crimping the crimp grip. h) is a side view of the end of the short anchor after crimping the crimping grip. It is a figure which shows the short anchor using the crimping grip which concerns on 1st Embodiment or 2nd Embodiment of this application. (A) is a cross-sectional view of the short anchor, (b) is a side view of the short anchor, (c) is a cross-sectional view of the load-bearing body, (d) is a side view of the load-bearing body, and (e) is a cross-sectional view of the tip cap. (F) is a side view of the tip cap. It is sectional drawing of the PC steel stranded wire. (A) is a cross-sectional view of an unbonded PC steel stranded wire, and (b) is a cross-sectional view of an all-wire coated PC steel stranded wire. It is a figure which shows the state which installed the short anchor using the crimping grip which concerns on 1st Embodiment or 2nd Embodiment of this application on the ground. (A) is a side view of the first embodiment of the present application, and (b) is a side view of the second embodiment of the present application. It is a side view which shows the example which used the short anchor which used the crimping grip which concerns on 1st Example of this application for slope reinforcement.

The applicant of the present application, in Japanese Patent Application No. 2019-161865 (hereinafter referred to as "Patent Application 1"), introduces a tension force into the PC steel stranded wire and can fix it with a nut like a lock bolt. Is proposing. Further, in Japanese Patent Application No. 2020-27155 (hereinafter referred to as "Patent Application 2"), the applicant of the present application proposes a crimping grip with a screw rod exclusively for PC steel stranded wire (single unbonded) having a synthetic resin coating. There is.

FIG. 4 of Patent Application 1 shows a tension material in which crimp grips with screw rods are crimp-fixed to both ends of a PC steel stranded wire. One of these pair of crimping grips with screw rods has a longer screw rod portion than the other. As for the tension material described in Patent Application 1, as shown in FIG. 4 of Patent Application 1, a crimping grip side with a long screw rod is arranged on the anchor head side, and the crimping grip with a screw rod is used. A nut and an anchor plate can be attached as a fixing tool for tension fixing. Further, a nut and an anchor plate can be attached to a crimping grip with a short screw rod portion arranged on the tip end side of the anchor to serve as a load bearing body. With this configuration, it becomes a tensioning material that can be used for a compression type anchor (paragraph 0012 of Patent Application 1).

The tension material described in Patent Application 1 can be nut-fixed by using a PC steel stranded wire without introducing a tension force as in the case of a conventional lock bolt. However, when introducing a tension force, it is necessary to provide a free length portion, so that there is a problem that the tension material described in Patent Document 1 cannot be applied.

The invention described in Patent Application 2 is proposed as solving the above-mentioned problem of Patent Application 1. FIGS. 5 and 6 of Patent Application 2 show an application example of a tension type anchor used by cutting off the PE coating at the tip of an unbonded PC steel stranded wire. However, in this case, not only is there a problem that it takes time to cut off the PE coating, but also a predetermined anchor length is required to secure the amount of elongation, so that the depth of drilling can be secured and the tension material can be used. It takes time and cost to install and fill the grout.

An example in which a fixing body (load-bearing body) is provided at the tip of the anchor and applied to a compression type anchor is the same as that already shown in FIG. 4 of Patent Application 1, and is therefore omitted in Patent Application 2. There is. When applying patent application 2 to a compression type anchor using the crimping grip with a screw rod shown in FIG. 4 of patent application 1 as a load bearing body, it is necessary to attach a nut and an anchor plate, and the screw rod is integrated with the crimping grip. Since it is necessary to form the surface, it takes time and cost.

As a rust preventive treatment method for steel parts, a method of galvanizing the surface is generally the cheapest and easiest method. However, if the processed crimping grip is subjected to high temperature and plated, it will thermally expand and adversely affect the performance of crimping to the PC steel stranded wire. Therefore, even if the anchor described in Patent Application 2 is attached with a crimping grip with a screw rod shown in FIG. 4 of Patent Application 1 as a load-bearing body, galvanized coating cannot be adopted and a special rust preventive treatment is applied. The cost increases because it is required. On the other hand, since muddy water, slime, etc. at the deepest part of the anchor hole into which the tension material is inserted cannot be completely cleaned and removed, it can be said that the tip of the tension material needs to be particularly rust-proofed. ..

From the above, it is difficult to use the crimping grip with a screw rod disclosed as a load-bearing body in Patent Application 1 by attaching it to the tip of the tension material in Patent Application 2. The crimping grip and the short anchor according to the embodiment of the present application also solve these problems.

(First Embodiment)
Hereinafter, the crimping grip 1 according to the first embodiment of the present application will be described with reference to the drawings. FIG. 1 is a diagram showing a crimping grip 1 and a tip portion of a short anchor 2 using the crimping grip 1 according to the first embodiment of the present application.

The crimping grip 1 includes a cylindrical crimping sleeve 3 and an insert 4 inserted into the hollow portion of the crimping sleeve 3. FIG. 1A shows a cross section of the crimping sleeve 3 cut in the central axis direction, and FIG. 1B shows a side surface of the crimping sleeve 3 viewed from a direction perpendicular to the central axis direction.

The crimp sleeve 3 has an insert storage portion 3a on one side (left side when facing FIG. 1) and a synthetic resin coating intake portion 3b on the other side (right side when facing FIG. 1) in the direction of the central axis.

As shown in FIG. 1 (c), the insert 4 has a cylindrical shape shorter than that of the crimp sleeve 3. The insert 4 has a pair of slit portions 4a extending in the central axis direction. The pair of slit portions 4a are formed at positions facing each other in the radial direction of the insert 4. Each of the pair of slit portions 4a is open to the side adjacent to the synthetic resin coating uptake portion 3b when the insert 4 is arranged in the crimp sleeve 3. Each of the pair of slit portions 4a extends to substantially the center of the insert 4 in the central axis direction. The inner and outer peripheral surfaces of the insert 4 are uneven surfaces in which a plurality of non-slip blades protruding in an annular shape are formed at equal intervals in the direction of the central axis of the insert 4.

The insert storage portion 3a of the crimp sleeve 3 has substantially the same length as the insert 4 in the central axis direction. The synthetic resin coating uptake portion 3b is formed over a predetermined length in the direction of the central axis of the insert 4.

In the first embodiment, the inner diameter R1 of the synthetic resin coating uptake portion 3b has the same diameter as the inner diameter R2 of the insert storage portion 3a, and the insert is inserted into the outer peripheral portion of the synthetic resin coating uptake portion 3b in the central axis direction. A taper 3b1 whose diameter decreases from the storage portion 3a side toward the end surface on the side opposite to the insert storage portion 3a is formed over the entire length.

As shown in FIGS. 1 (d) and 1 (f), when the crimp sleeve 3 is crimped through a die (not shown) with the end of the unbonded PC steel stranded wire 5 inserted in the crimp grip 1, FIG. As shown in (g), the insert housing portion 3a is thinly plastically deformed to a predetermined inner diameter, and the inner insert 4 is the end portion 5b (bare wire) of the unbonded PC steel stranded wire 5 from which the synthetic resin coating 5a has been removed. The surface of the crimping sleeve 3 and the end portion 5b of the unbonded PC steel stranded wire 5 are firmly bonded to each other. As described above, by forming the taper 3b1 on the outer peripheral portion of the synthetic resin coating uptake portion 3b, the synthetic resin coating uptake portion 3b is more than the crimping force received by the insert storage portion 3a when crimping through the die. The crimping force received is smaller. As a result, after the crimping sleeve 3 is crimped, the synthetic resin coating 5a in the synthetic resin coating uptake portion 3b is not damaged and is appropriately deformed to the extent that it adheres to the crimping sleeve 3, and the open end of the crimping sleeve 3 is formed. Water can be stopped between the portion and the unbonded PC steel stranded wire 5. The angle of the taper 3b1 can be determined according to the outer diameter and thickness of the synthetic resin coating 5a.

(Second Embodiment)
Next, the crimping grip 1 according to the second embodiment of the present application will be described with reference to FIG. Since the crimping grip 1 according to the second embodiment is common to the crimping grip 1 according to the first embodiment in many respects, the parts corresponding to the parts described with reference numerals in the first embodiment are used. Is designated by the same reference numerals as those in the first embodiment, and the description overlapping with the first embodiment will be omitted.

In the second embodiment, the taper 3b1 is not formed on the outer peripheral portion of the synthetic resin coating uptake portion 3b, and the inner diameter R1 of the synthetic resin coating uptake portion 3b is formed larger than the inner diameter R2 of the insert storage portion 3a. The specific sizes of the inner diameters R1 and R2 are appropriately determined according to the outer diameter and thickness of the synthetic resin coating 5a to be taken in. The inner diameter R1 of the synthetic resin coating uptake portion 3b has a size that allows the synthetic resin coating 5a to be inserted before the crimping process, and is crimped through a die (not shown) according to the same principle as in the first embodiment. At this time, the crimping force received by the synthetic resin coating take-in portion 3b is smaller than the crimping force received by the insert storage portion 3a, the synthetic resin coating 5a adheres to the crimping sleeve 3 after the crimping process, and the synthetic resin coating 5a is damaged. Set so that there is nothing to do.

By configuring the crimping sleeve 3 in this way, when the crimping sleeve 3 is crimped through a die, the insert 4 bites the end portion 5b of the unbonded PC steel stranded wire 5 from which the synthetic resin coating 5a has been removed, and the crimping grip. 1 and the unbonded PC steel stranded wire 5 are firmly bonded to each other, and the synthetic resin coating taking-in portion 3b having a large inner diameter R1 deforms the synthetic resin coating 5a to the extent that it adheres to the crimp sleeve 3 and crimps the resin. Water can be stopped between the end of the sleeve 3 and the synthetic resin coating 5a. As a result, according to the second embodiment, the same effect as that of the first embodiment can be obtained. According to the first embodiment and the second embodiment described above, the synthetic resin coating uptake portion 3b has a radial thickness smaller than the radial thickness dimension of the insert storage portion 3a over the entire length in the central axis direction. It can be seen that it is sufficient to have dimensions.

(First Example)
FIG. 3 is a diagram showing a first embodiment of a short anchor 2 using a crimping grip according to the first embodiment or the second embodiment of the present application. FIG. 3A is a cross-sectional view showing a cross section obtained by cutting a part of the components of the short anchor 2 in the longitudinal direction. FIG. 3B is a side view of the short anchor 2. FIG. 3C is a cross-sectional view showing a cross section of the load-bearing body 7 cut in the longitudinal direction. FIG. 3D is a side view of the load bearing body 7. FIG. 3E is a cross-sectional view showing a cross section of the tip cap 8 cut in the longitudinal direction. FIG. 3 (f) is a side view of the tip cap 8.

The short anchor 2 has a load-bearing body 7 and a tip cap 8 arranged adjacent to the load-bearing body 7. As shown in FIGS. 3 (c) and 3 (d), the load-bearing body 7 has a tubular shape and has a spiral protrusion 7a on the outer peripheral portion. Further, at the end of the load-bearing body 7 on the tip cap 8 side, a male screw portion 7b having a smaller outer diameter than the other portions and having a thread groove formed on the outer peripheral portion is formed. The male screw portion 7b comes into contact with the crimping grip 1 so as to be able to transmit stress in the central axis direction. The unbonded PC steel stranded wire 5 is passed through the load-bearing body 7 inside.

As shown in FIGS. 3 (e) and 3 (f), the tip cap 8 has a bottomed cylindrical shape, and has a female screw portion 8a having a thread groove formed on the inner peripheral surface of the end portion on the load bearing body 7 side. Have. Inside the tip cap 8, the crimping grip 1 and the tip of the unbonded PC steel stranded wire 5 crimped by the crimping grip 1 are inserted. The male screw portion 7b of the load bearing body 7 and the female screw portion 8a of the tip cap 8 are screwed together, and the load bearing body 7 and the tip cap 8 are integrated. As a result, the crimping grip 1 is rust-proof and corrosion-proof, and can be used as a fixed end of a durable compression type anchor.

The unbonded PC steel stranded wire 5 extends to the anchor head. In the longitudinal direction, a crimping grip 9 with a screw rod is crimped to the end of the unbonded PC steel stranded wire 5 on the side opposite to the crimping grip 1 (anchor head side). The crimping grip 9 with a screw rod has a bottomed cylindrical crimping sleeve 9a, an insert 9b interposed between the crimping sleeve 9a and the unbonded PC steel stranded wire 5, and a screw rod 9c extending from the bottom of the crimping sleeve 9a. .. The crimp sleeve 9a and the insert 9b of the crimp grip 9 with a screw rod are the same as the crimp sleeve 3 and the insert 4 of the crimp grip 1 of the first or second embodiment, except that the crimp sleeve 9a has a bottom. Can be configured in. An anchor plate 10 having a hole 10a formed therein is fitted onto the screw rod 9c, and a nut 11 is screwed onto the tip side of the screw rod 9c with respect to the anchor plate 10.

FIG. 4A is a cross-sectional view of the unbonded PC steel stranded wire 5, and FIG. 4B is a cross-sectional view of the all-wire coated PC steel stranded wire. The unbonded PC steel stranded wire 5 shown in FIG. 4A has, for example, a polyethylene synthetic resin coating (PE coating) 5a on the outer circumference of the 7 stranded PC steel stranded wire (bare wire) having 7 strands 5c. Giving. The gap between the wire 5c and the synthetic resin coating 5a is filled with grease or wax as a filler. In the all-strand-coated PC steel stranded wire 12 shown in FIG. 4 (b), the resin coating 12a is applied to each of the seven PC steel stranded wire 12c. In the short anchor 2 of the present application, the unbonded PC steel stranded wire 5 shown in FIG. 4A is used.

FIG. 5A is a side view showing a state in which the first embodiment of the short anchor 2 using the crimping grip 1 according to the first embodiment or the second embodiment of the present application is installed on the ground.

The short anchor 2 is inserted into the anchor hole 13 in which a portion other than the head is drilled in the ground. The injection material (PC grout) 14 is injected into the gap between the short anchor 2 and the anchor hole 13. As the injection material 14, a known cement-based injection material or synthetic resin-based injection material can be used. The injection material 14 is injected in a liquid state and then cured in the pores. A pressure receiving plate 15 is arranged between the ground surface and the anchor plate 10. A screwed washer 16 may be arranged between the anchor plate 10 and the nut 11.

After the injection material 14 is cured, a tension force is introduced into the short anchor 2. By introducing a tension force into the short anchor 2, the unbonded PC steel stranded wire 5 is stretched by a predetermined length due to elastic deformation. In that state, the nut 11 is tightened and fixed.

After the tension of the short anchor 2 is fixed, the head of the short anchor 2 is subjected to anticorrosion treatment. The anticorrosion treatment is performed, for example, by attaching a head cap 17 covering the screw rod 9c, the nut 11 and the screwed washer 16 of the crimping grip 9 with a screw rod to the anchor plate 10 and injecting a food-proof material into the head cap 17. ..

According to the first embodiment, since the short anchor 2 remains coated with the synthetic resin over almost the entire length, it is easy to secure a sufficient amount of elongation even when the total length is short, and the soundness and safety are achieved. It can be a ground anchor having. In the tension type ground anchor, the anchor free length part and the anchor fixing length part are arranged at different positions in the longitudinal direction, and the anchor free length part is in an unbonded state and the anchor fixing length part is in a bonded (bare wire) state. .. On the other hand, the short anchor 2 of the first embodiment is a compression type anchor, and the portion of the unbonded PC steel stranded wire 5 arranged inside the load-bearing body 7 forming a part of the anchor fixing long portion also extends. .. That is, as shown in FIG. 5A, the anchor free length portion and the anchor fixing length portion are wrapped. As a result, the short anchor 2 can easily secure a sufficient amount of elongation even if the total length is shortened.

FIG. 6 is a side view showing an example in which the short anchor 2 according to the first embodiment is used for slope reinforcement. As shown in FIG. 6, the slip surface S is generally located shallower from the slope as it goes down. Therefore, in particular, the ground anchor placed at a low position can be fixed to the hard ground at the back of the slip surface S even if it is relatively short. However, in the conventional ground anchor, the total length must be increased in order to secure sufficient elongation of the tension material. On the other hand, according to the short anchor 2 according to the first embodiment, even if the total length is shortened, sufficient elongation of the unbonded PC steel stranded wire 5 can be ensured. As a result, the amount of unbonded PC steel stranded wire 5 used is reduced, the depth of drilling is shallower, and the amount of injection material 14 is also reduced, so that the labor and cost of construction can be reduced.

Further, according to the short anchor 2 of the first embodiment, the anchor cross section can be formed by a single unbonded PC steel stranded wire as in the lock bolt, the drilling diameter is reduced, and the amount of the injection material 14 is also increased. Since it can be reduced, the labor and cost of construction can be reduced.

Further, according to the short anchor 2 according to the first embodiment, the crimping grip 1 is covered with the tip cap 8, the tip cap 8 is integrated with the load bearing body 7, and the injection material 14 is inside the load bearing body 7. Since it penetrates, it is possible to prevent corrosion of the crimping grip 1.

(Second Example)
FIG. 5B is a side view showing a second embodiment of the short anchor 2 using the crimping grip 1 according to the first embodiment or the second embodiment of the present application. Since the second embodiment is common to the first embodiment in many respects, the same reference numerals as those of the first embodiment are used for the parts corresponding to the parts described with reference numerals in the first embodiment. It will be added and duplicate explanations will be omitted.

In the second embodiment, the wedge 18 and the anchor head 19 are used instead of the crimping grip 9 with a screw rod, the nut 11 and the washer 16 with a screw of the first embodiment. Also in the second embodiment, the same effect as that of the first embodiment can be obtained.

1 Crimping grip 2 Short anchor 3 Crimping sleeve 3a Insert storage part 3b Synthetic resin coating Incorporating part 3b 1 Tapered part 4 Insert 4a Slit part 5 Unbonded PC steel stranded wire 5a Synthetic resin coating 5b End 5c Wire 7 Load-bearing body 7a Protrusion 7b Male screw part 8 Tip cap 8a Female screw part 9 Crimping grip with screw rod 9a Crimping sleeve 9b Insert 9c Screw rod 10 Anchor plate 10a Hole 11 Nut 12 Full wire coating type PC steel Strand 12a Resin coating 12c Wire 13 Anchor Hole 14 Injection material 15 Pressure receiving plate 16 Screwed washer 17 Head cap 18 Wedge 19 Anchor head R1 Inner diameter of synthetic resin coating intake part R2 Inner diameter of insert storage part S Sliding surface

Claims (5)

A crimping grip for unbonded PC steel stranded wire with a synthetic resin coating.
The crimping grip comprises a cylindrical crimping sleeve and an insert that is cylindrical and has a blade formed on the inner and outer peripheral surfaces and is inserted into the crimping sleeve.
The crimp sleeve has an insert storage portion on one side and a synthetic resin coating capture portion on the other side in the direction of the central axis.
A crimping grip characterized in that the synthetic resin coating take-in portion has a radial thickness dimension smaller than the radial thickness dimension of the insert storage portion over the entire length in the central axis direction. A feature is that a taper is formed on the outer peripheral portion of the synthetic resin coating take-in portion in the direction of the central axis from the insert storage portion side toward the end surface on the opposite side of the insert storage portion. The crimping grip according to claim 1. The crimping grip according to claim 1, wherein the inner diameter of the synthetic resin-coated intake portion is larger than the inner diameter of the insert storage portion. Unbonded PC steel stranded wire with synthetic resin coating and
The crimping grip according to any one of claims 1 to 3, which is crimped to the end of the unbonded PC steel stranded wire.
A bottomed cylindrical tip cap into which the crimp grip is inserted,
A short anchor having a tubular shape, through which the unbonded PC steel stranded wire penetrates, and a load-bearing body arranged adjacent to the tip cap.
A female screw portion is formed on the inner peripheral portion of the tip cap on the load-bearing body side.
A male screw portion is formed on the outer peripheral portion of the load-bearing body on the tip cap side.
The tip cap and the load-bearing body are integrated by screwing the female screw portion and the male screw portion.
The crimping grip and the male screw portion come into contact with each other so as to be able to transmit stress in the central axis direction.
A short anchor characterized in that the unbonded PC steel stranded wire extends to the anchor head. The short anchor according to claim 4, wherein a spiral protrusion is formed on the outer peripheral surface of the load-bearing body.

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