JP3616321B2 - Ground anchor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ground anchor that transmits an unbonded tensile material to an unbonded tensile material through a fixed pedestal at the tip of a load-bearing body through which an unbonded tensile material is penetrated and to which a supporting rod and a reinforcing rod are attached. It is.
[0002]
In addition, the twist of the uncurtain don is twisted inside the sheath pipe, which serves as an anti-corrosion for unbonded type PC steel (PC steel wire, PC steel bar, PC steel strand) and serves as a grout injection tube for anchoring the anchor body. The present invention relates to a grouting method using a star-shaped injection spacer or a strand center riser to prevent and increase the injection efficiency.
[0003]
Furthermore, in order to prevent or restore landslides and slope disasters, the ground anchor method that responds to social demands that are highly reliable and economical is desired. This will expand the scope of use in disaster-related projects.
[0004]
[Prior art]
The anchors to be anchored are the bedrock, sand layer, gravel layer, loam layer, Dotan layer, etc., and the above-mentioned PC steel material is used for the anchor cable. It is called the construction method and is used as an anchor to stabilize structures such as slip prevention, slope failure prevention, retaining wall / holding fall prevention, and prevention of floating underground structures.
[0005]
For fixing the general anchor body to the target ground, a grout material such as cement milk is injected, adhered to the hole wall and the anchor body, and supported by the peripheral friction resistance. In addition, as the fixing / support mechanism, there are a hole expansion support type and a tip compression type in the ground to be fixed, and in the technology previously provided by the applicant, a fixing mechanism using both peripheral friction resistance and tip compression force is used. It is what you have.
[0006]
For example, as shown in FIG. 8, the anchor fixing method is as follows. The bearing plate (b) is attached to the end of an unbonded type tensile material (a), and the anchor plate (c) is excavated in the ground. Insert and fix the anchor length of the anchor hole at the back of the anchor hole with anchor grout (cement milk, mortar, etc.), wait for the curing material to harden, and give tension to the free length It will be established.
In this fixing method, when the tension member (a) is tensioned, a pulling force acts on the tension member (a). Therefore, the anchor housing (d) is compressed in the anchor axial direction, and at the same time, the anchor hole (c ) In the direction of expanding the diameter. Accordingly, cracks (e) may occur in the anchor housing (d), and the anchor strength is reduced, and at the same time, the tensile material (a) is corroded by the ingress of groundwater or the like.
[0007]
Therefore, the applicant of the present application previously solved the above problem by providing a reinforcing bar etc. on the ground anchor according to Japanese Patent No. 2120240. The outline of the patent is as follows.
The method of anchoring anchors on the stable ground and tensioning them via a tensile material such as PC steel wire is called the ground anchor method for disaster prevention work on landslides and collapse risk slopes and for structural stability.
Regarding anchor anchorage, the frictional resistance between the anchor body and the grout material such as cement milk, and the frictional resistance between the grout material and the hole wall of the stable side ground drilled by boring, etc. It should be greater than the tension.
[0008]
When the anchor is tensioned, the anchor body is compressed in the axial direction, and a force that expands in the hole wall direction acts. At this time, cracks may occur in the grout material, and the proof stress of the anchor body is reduced.
[0009]
In order to prevent the occurrence of such cracks, rebar rods consisting of horizontal bars positioned in the axial direction of the uncurtain dong and spiral bars positioned in the circumferential direction of the uncurtain dong are attached to the anchor body, and the grouting material is reinforced concrete. It is strengthened, and stress is transmitted through a bearing plate attached to one end of an unbonded tensile material.
[0010]
This is because the load concentrated on the anchor tip can be distributed to the upper part, so that extremely stable fixing can be obtained. The steel material to be used was able to exhibit excellent performance as a permanent anchor by being rust-proofed twice or more by a corrosion protection material such as polyethylene pipe, waterproof seal, and grout material.
[0011]
[Problems to be solved by the invention]
In the anchor fixing method, when the PC steel group is tensioned, a pulling force acts on the PC steel group, so that the anchor housing is compressed in the anchor axial direction and at the same time expands in the direction of expanding the anchor hole. . Therefore, cracks may occur in the anchor housing, and the anchor strength is reduced. At the same time, the PC steel group is corroded by the intrusion of groundwater or the like.
[0012]
However, even in the above-mentioned patents, anchors that are underground structures often change the ground strength of the anchorage ground depending on complex geological and hydrological conditions, and the ground strength of the hole wall at the anchoring position is too weak. The injected grout material may be caused to flow by the flow of groundwater, or may be thinned to obtain a predetermined strength, and the anchor body may buckle or come out. In addition, it is not practical to correctly determine changes in geological and hydrological conditions because the geological survey costs are enormous.
[0013]
For this reason, depending on the strength of the ground strength of the hole wall at the fixing position, if the stress received by the anchor body is distributed in the upper direction of the anchor body and received as a frictional resistance force on the peripheral surface of the hole wall, the hole wall is distorted and the anchor body is It is possible to prevent the anchor body from buckling out and breaking the hole wall.
[0014]
In addition, as for the injection grout material for anchor anchorage, it is common to just replace the water in the hole with grout material or to inject the grout material little by little with a thin injection tube, but in the vicinity of the fixing ground In order for the grout material to be filled in the target position without being diluted with ground water or the like, it is desired that the grout material in the injection pipe should be smoothly flowed so that the grout material can be reliably filled in the injection target position.
[0015]
[Means for Solving the Problems]
Therefore, the present invention is provided to solve the conventional problems and achieve the object of the invention. That is, in the first ground anchor of the present invention, a fixing bracket and a supporting rod that transmit and distribute a load to the grouting material by unevenness on the outer peripheral surface, and a supporting plate that supports the grouting material by connecting to the supporting rod. The reinforcing rod is surrounded by a supporting rod and fixed by a supporting plate so that the grout material does not expand and break.
The second aspect of the present invention is the ground anchor according to the first aspect of the present invention, wherein a double line is used to secure a continuous star-shaped injection cross section in the sheath pipe that uses the anticorrosion covering the tensile material and the grout material together with the injection pipe. It is provided with a star-shaped injection spacer made of steel or other material to be sandwiched between the two.
According to a third aspect of the present invention, in the ground anchor according to the first aspect of the present invention , a single wire tension material is positioned at the center of the sheath pipe for injection, and is made of a steel material or other material that holds the tension material at the center in the sheath pipe. A strand center riser is provided.
[0016]
In order to prevent buckling and pulling out of the anchor body due to the strength of the ground of the anchoring ground, the anchor body tip (fixed pedestal, fixing bracket) where the stress in the hole wall direction of the anchor hole concentrates normally is a steel material. The anchor body does not buckle even if the hole wall is weak.
[0017]
As a result, if the strength of the fixing part hole wall is weak, the tension stress is shared and transmitted in the upper part of the anchor body. The structure is connected to a fixing bracket with sufficient strength and surrounded by the above-mentioned rebar rods, which adds to the effect of frictional anchors and prevents compression failure of the grout material, and encounters complex geological changes in the anchoring ground. Even so, the desired anchor tension can be obtained and the ground anchor can be maintained over a long period of time.
[0018]
As a method of injecting grout material for anchor anchorage, a sheath pipe made of polyethylene pipe or the like, which is also intended to prevent corrosion of unbonded PC steel, is used as an injection tube. The cross-sectional area can be increased, the injection efficiency is increased, and the strength of the grout material can be prevented from being lowered due to dilution of the grout material at the fixing position due to the flow of water in the pores. However, if a plurality of tensile materials are twisted or crossed in the sheath, there is a concern that the flow of the grout material may be vortexed, or the flow rate may be disturbed and blocked.
[0019]
By inserting a star-shaped injection spacer evenly between multiple tension members at the required intervals, the actual injection cross-section forms a continuous star-shaped cross-section in the form of a uniform column, and there is no hindrance to grout flow, and the purpose of grout injection Is achieved. When the tensile material is a single wire, the uncurtain dong is held at the center of the sheath pipe by the strand center riser, so that the injection cross-section is similarly stabilized and there is no obstacle to changing the flow rate of the grout material, and stable injection is performed.
[0020]
For uncertainties, the water substitution type grout filling method (common name: dobbling) and low-speed injection using small-diameter injection pipes dilute the grout material due to groundwater flow near the fixed ground. Although there was anxiety that the grout strength could not be obtained, this was solved by the present invention. And according to this invention, even if it encounters the complicated geology and water | moisture conditions of a fixed ground, an anchor body can be fixed reliably and required tension | tensile_strength can be maintained over a long term.
[0021]
【Example】
Reference numeral 1 denotes a fixing bracket, which is a steel cylinder, and has an outer peripheral surface with screws engraved in the opposite direction from the middle to both ends.
Reference numeral 2 denotes a lower support plate, which is connected to the fixture 1 with a screw, and transmits the shared load from the fixture to the load bearing body (support rod, rebar rod) with the support rod 3 and the screw. The rebar rods that are connected and attached to the outer periphery thereof are sandwiched between the upper support plate 9 and fixed. The upper support plate 9 protects the unbonded tensile material, and connects and fixes a sheath pipe disposed around the anchor free length by a material such as polyethylene serving as an injection pipe.
The upper and lower support plates 2 and 9 obtain the displacement in the radial direction by the compressive force by utilizing the fact that the rigidity of the fixing portion is reduced at the front surface, and the load is effectively transmitted to the fixing ground. . The space between the upper and lower bearing plates 2 and 9 (the bearing rod 3 and the reinforcing bar rod are sandwiched) is referred to as a load bearing body.
[0022]
Reference numeral 3 denotes a support rod, which has a material and a cross-sectional area that can sufficiently resist the required pulling force of the anchor at the upper part of the fixture 1.
The bearing rod 3 is provided with fine irregularities on the surface of the steel pipe to enhance the adhesion with the grout material. A reinforcing bar is sandwiched and fixed between the upper support plate 2 and the lower support plate 9 so as to surround the support rod.
[0023]
Reference numeral 4 denotes a bottom cover, 5 denotes a crimping grip, 6 denotes a protrusion provided on the peripheral surface of the fixing metal, 7 denotes a grout material discharge hole, and 8 denotes a fixing base with a through hole for fixing the crimping grip 5.
[0024]
Reference numeral 10 denotes a reinforcing bar rod, which is formed by positioning a plurality of small-diameter horizontal bars in the longitudinal direction of the PC steel material group and winding a constraining bar around the outer periphery of the PC steel group like a small-diameter spiral bar.
The restraint bars may be attached with a plurality of independent ring bars, squares, octagons, ellipses, or other reinforcing materials instead of spiral bars. Further, the housing can be formed using a corrosion-resistant material such as carbon fiber or glass fiber instead of the reinforcing bar.
[0025]
Reference numeral 11 denotes a tensile material made of unbonded PC steel wire, the end of which is passed through the through hole of the fixed base 8, the pressure-bonding grip 5 is pressed, and a tensile force is received by the fixed base.
A star-shaped injection spacer 12 secures a star-shaped columnar cross section that stabilizes the injection efficiency of the anti-corrosion and injection sheath pipe 13 that covers the unbonded type tensile material 11 (an curtain curtain), and includes a plurality of tensile materials 11. In order to prevent torsion in the sheath, the unbonded tensile material 11 is made of steel or other material for evenly constraining the unbonded tensile material 11. Install.
[0026]
Reference numeral 14 denotes a strand center riser. When a single wire unbonded type tensile material 11 is used, it is positioned at the center of the injection sheath pipe 13 to stabilize the injection efficiency and prevent twisting of the tensile material 11 or It has a hollow triangular prism type structure made of other materials.
[0027]
[Example of construction]
In the present invention, the fixing bracket 1 and the support rod 3 in the load bearing body serve as a load transmission shaft, and the outer peripheral surface adheres to the grout material and is supported by the upper and lower bearing plates 2 and 9 provided on the load bearing body. It has a composite structure in which load is transmitted by pressure. The fixing bracket 1 and the support rod 3 have sufficient compressive strength against the axial force distribution at the time of fixing, and in order to ensure a wide peripheral friction resistance even when the strength of the ground G is small, such as soft rock, Sufficient load transmission is possible.
Further, the upper and lower support plates 2 and 9 obtain the displacement in the radial direction by the compression force by utilizing the fact that the rigidity of the fixing portion is reduced at the front surface, and the load is effectively transmitted to the ground. .
Further, in order to prevent splitting fracture of the grout material due to compressive deformation in the radial direction, the grout material on the front surface of the bearing plate is reinforced with the reinforcing bar 10 to increase the strength of the grout material and toughness (stickiness).
By adopting such a complex shape for the anchor body, the front surfaces of the upper and lower bearing plates 2 and 9 are sufficiently covered, and the grout material is excellent in wrapping and filling properties, and adhesion of mud, grease, etc. during anchor body insertion Also, the pullout resistance is surely obtained.
In order to use the sheath pipe 13 that covers the uncurtain dong and protects against rust as an injection pipe, the grout material injection work is simplified by installing the star-shaped injection spacer 12 and the strand center riser 14 in the sheath pipe at appropriate intervals. At the same time, reliable filling of the grout material can be performed. In addition, since the uncurtain dong such as a plurality of PC steel materials covered by the sheath pipe 13 does not twist or cross in the sheath pipe, there is a one-side effect when the tension material 11 made of individual unbonded PC steel wires is in tension. The anchor pulling force is set as designed.
[0028]
【The invention's effect】
Since this invention is the above structure, the following effects are acquired.
(1) The ground anchor is a structure that transmits a load to the ground by applying a compressive force to the tip of the anchoring part. Transferring tensile cracks using the characteristics that the compressive strength of the grout material is extremely large compared to the tensile strength. The risk of progressive destruction due to is avoided.
(2) The fixing bracket base does not cause large displacement or buckling even if the anchorage ground strength is small, disperses stress toward the upper load bearing body, and the load bearing body and the grout material are integrated into the anchorage ground (anchor hole). Since the required anchor tensile force can be obtained by the peripheral frictional resistance force with the wall), the anchor can cope with a wide range of fixed ground conditions.
(3) With normal anchors, when encountering a fixed ground with unpredictable strength, the weak ground will be over-compressed, causing buckling of the anchor body itself or pulling out of the anchor body. Changes may be forced, increasing construction costs and hindering business continuity.
(4) Since the sheath pipe is used as the injection pipe, the grout material is discharged from the grout discharge hole at the bottom of the fixture and filled all over the hole and outside the anchor body. It can be prevented from becoming insufficiently filled with grout material.
(5) The star-shaped injection spacer installed in the sheath pipe prevents twisting of the plurality of tensile materials in the sheath, so that there is no fear of one-sided effect during tension of the tensile material. This single effect has a danger that the tension force concentrates on a part of each tensile material and breaks even if the tension force is smaller than the anchor design load, but this is removed.
[Brief description of the drawings]
FIG. 1 is a front view of a ground anchor according to the present invention.
2 is a central longitudinal sectional view of FIG. 1. FIG.
3 is a cross-sectional view taken along line 3-3 in FIG.
4 is a cross-sectional view for double lines showing another example of FIG. 3; FIG.
5 is a cross-sectional view for single line along line 4-4 in FIG. 1. FIG.
6 is a cross-sectional view for double lines showing another example of FIG. 5;
FIG. 7 is a schematic explanatory view showing a usage state of the ground anchor according to the present invention.
FIG. 8 is a central longitudinal sectional view showing a fixing state of a conventional peripheral friction anchor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixing bracket 2 Lower support plate 3 Supporting rod 4 Bottom cap 5 Crimp grip 6 Protrusion part 7 Grout discharge hole 8 Fixing base 9 Upper support plate 10 Reinforcement rod 11 Tensile material (Unbonded PC steel strand)
12 Star-shaped injection spacer (for double wires)
13 Sheath pipe (with injection hose)
14 Strand center riser (for single wire)

Claims (3)

Fixing bracket that transmits and distributes load to regrout material by unevenness on outer peripheral surface (1) And bearing rod (3) And bearing rod (3) Support plate for supporting grout material by connecting to (2) ・ (9) And support rod to prevent the grout material from expanding and breaking (3) Surrounding bearing plate (2) ・ (9) Reinforced rod fixed by (Ten) The ground anchor characterized by comprising. Steel material to be sandwiched by double-wire tension material (11) to ensure a continuous star-shaped injection cross section in sheath pipe (13) that uses anticorrosion and grout material covering tensile material (11) together with injection tube The ground anchor according to claim 1, further comprising a star-shaped injection spacer (12) made of other materials. A single-wire tension material (11) is positioned at the center of the sheath pipe (13) for injection, and a strand center riser (14) made of steel or other material holding the tension material (11) in the center of the sheath pipe. 2. The ground anchor according to claim 1, which is provided.

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