JP2002105955A - Ground anchor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove such a fear that a crack is brought about because an anchor body is compressed in the direction of the anchor shaft band concurrently expanded in the direction widening the anchor hole as a drawing force acts on the tension member when the tensile member of an unbonding type tensional member is pulled and remove a cause of corrosion of the tensile member caused by both decrease of anchor proof stress and intrusion of the underground water. SOLUTION: The ground anchor is constituted of a tensile member 11 made of an anbonded PC stranded wire, a fixed base 8 attached at one end of the tensile member, a pressure-supporting rod 3 connected to the fixed base 8 in a state that the tensile member is penetrated and increasing the frictional resistant force with the grout member through the fixed metal tool 1, and a cylindrical steel rod cage 10 surrounding the supporting rods and put in between the supporting plates 2, 9 of the upper and lower sections.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load-bearing body having a supporting rod and a reinforcing bar cage, which has an unbonded tension member penetrated therein, and which is tensioned to the unbonded tension member via a fixing pedestal at the tip end thereof. This is related to the ground anchor transmitting the signal.

In addition, unbonded type PC steel (PC steel)
Steel wire, PC steel rod, PC steel stranded wire) To prevent corrosion of the uncurtain don and increase the injection efficiency inside the sheath pipe, which serves as a grout injection pipe for anchoring the anchor body and for preventing corrosion of the anchor rod And a grout injection method using a star injection spacer or a strand centerizer.

Further, in order to prevent or recover from landslides and slope disasters, a ground anchor method that meets social demands that are highly reliable and economical is required. Because it can respond to changes, the range of use in disaster-related businesses is expanded.

[0004]

2. Description of the Related Art An anchor body is fixed to a rock, sand layer, gravel layer, loam layer, earthen layer, etc., and the above-mentioned PC steel material is used as an anchor cable, and the anchor cable is fixed to a structure by applying tension. This is called the ground anchor method, and is used as an anchor to stabilize structures such as preventing slippage, preventing landslides from collapsing, preventing retaining walls and retaining soil from falling, and preventing underground structures from lifting.

[0005] In order to fix the general anchor body to the target ground, grout material such as cement milk is injected, adhered to the hole wall and the anchor body, and supported by the peripheral frictional resistance. In addition, as the fixing / supporting mechanism, there are a pressure-supplying type and a tip-compression type on the ground to be fixed, and the technology previously provided by the applicant employs a fixing mechanism using both the peripheral frictional resistance and the tip-compressing force. Have.

The anchor anchoring method is, for example, as shown in FIG. 8, in which an anchoring plate (b) is attached to an end of a tensile member (a) of an unbond type or the like, and this is excavated in the ground.
(c) Insert the anchor grout (cement milk, mortar, etc.) into the anchoring length at the back of the anchor hole.
After the hardening material is filled, the hardening material is waited for hardening and a tension is applied to the free length portion to fix the free length portion. In this fixing method, when the tension member (a) is tensioned, a pulling force acts on the tension member (a), so that the anchor frame (d) is compressed in the anchor axis direction and the anchor hole (c) ) Expands in the direction to expand the diameter. Therefore, cracks occur in the anchor frame (d).
(e) may occur, and at the same time, the anchor proof strength is reduced, and at the same time, the tensile material (a) is corroded by intrusion of groundwater or the like.

Therefore, the applicant of the present application has previously filed Patent No. 212024.
The above-mentioned problem was solved by providing a steel cage or the like on the ground anchor according to No. 0. The outline of the patent is as follows. Anchors were anchored on the stable ground for disaster prevention work on landslides and collapse danger slopes, and for structural stability.
The method of tensioning through a tensile material such as a PC steel wire is called a ground anchor method. Regarding anchor anchoring, 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., depend on the expected tensile material (uncurtain don). It is only necessary to be larger than the tension.

[0008] When the anchor is tensioned, the anchor body is compressed in the axial direction, and a force acts to expand in the hole wall direction. At this time, cracks may occur in the grout material, and the proof stress of the anchor body is reduced.

In order to prevent the occurrence of such cracks, a reinforcing bar made of a horizontal streak positioned in the axial direction of the uncurtain don and a spiral streak positioned in the circumferential direction of the uncurtain don is attached to the anchor body to form a reinforced concrete shape. The grout material is reinforced, and the stress is transmitted through a support plate attached to one end of an unbonded tensile material.

[0010] This means that the load concentrated on the tip of the anchor can be dispersed also to the upper part, so that extremely stable fixing can be obtained. Excellent performance as a permanent anchor could be exhibited by using a steel material or the like to be rust-proofed more than twice with a corrosion-resistant material such as a polyethylene pipe, a waterproof seal, and a grout material.

[0011]

In the anchor fixing method described above, when the PC steel group is tensioned, a pulling force acts on the PC steel group, so that the anchor body is compressed in the anchor axial direction and at the same time, the anchor body is compressed. The hole expands in a direction to expand the diameter. Therefore, cracks may be generated in the anchor frame, which lowers the anchor strength and causes corrosion of the PC steel group due to intrusion of groundwater or the like.

However, even in the above-mentioned patent, the anchor which is an underground structure has a geological feature in which the ground strength of the anchored ground is complicated.
It often changes depending on the hydrological conditions, the ground strength of the hole wall at the anchoring position is too weak, the grout injected by the groundwater flows, or the grout is thinned and the predetermined strength is not obtained, and the anchor body is seated. May succumb or slip out. Also, judging changes in geological and hydrological conditions correctly makes the geological survey costs enormous and impractical.

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 dispersed in the upper direction of the anchor body and received as the frictional resistance of the peripheral surface of the hole wall, the hole wall may be distorted. It is possible to prevent the anchor body from coming out and the hole wall from breaking and the anchor body from buckling.

[0014] As for the grouting material for fixing the anchor body, it is common to simply replace the water in the hole with the grouting material or to inject the grouting material little by little with a thin filling pipe. In order to be able to fill the grout material at the target position near the anchoring ground without being diluted by groundwater, it is desirable that the grout material in the injection pipe be designed to flow smoothly and that the grout material be reliably filled at the injection target position. .

[0015]

SUMMARY OF THE INVENTION The present invention is provided to solve the conventional problems and to achieve the object of the invention. Part of or all of the tensile material made of unbonded PC steel material corresponding to the anchoring length in the anchor consisting of the anchoring length fixed to the inner part of the anchor hole excavated in the ground and the free length applying tension. Around the shaft, a reinforcing bar cage consisting of a horizontal bar located in the axial direction of the uncurtain don and a restraining bar located in the circumferential direction of the uncurtain don is connected to the fixing bracket pedestal via a grip with the tip of the tensile material crimped It is a ground anchor characterized by doing.

In order to prevent the anchor body from buckling or pulling out due to the strength of the ground strength of the anchoring ground, the anchor body tip portion (fixing pedestal, fixing bracket) where stress is usually concentrated in the direction of the hole wall of the anchor hole. ) Is strengthened by steel material so that the anchor body does not buckle even if the hole wall is weak.

[0017] When the strength of the fixing portion hole wall is low, the tensile stress is transmitted in the upward direction of the anchor body, so that the steel pipe or the like is processed to improve the peripheral friction resistance. Combined with the metal fittings that ensure sufficient strength of the pressure rod and surrounded by the above-mentioned reinforcing cage, the effect of the friction type anchor is added to prevent the grout material from compressive destruction, and the complex geology of the anchored ground Even if a change is encountered, the desired anchor tension is obtained, and the ground anchor can be maintained for a long time.

As a method for injecting the grout material for fixing the anchor body, it is necessary to use a sheath pipe made of a polyethylene pipe or the like, which is also for the purpose of preventing corrosion of the tensile material (uncurtain don) made of unbonded PC steel. It is possible to increase the cross-sectional area of the inside of the tube, thereby increasing the injection efficiency, and to prevent the grout material from decreasing in strength due to dilution of the grout material at the fixing position due to the flow of water in the hole.
However, if a plurality of tensile members are twisted or crossed within the sheath, there is a concern that the flow of the grout material may be swirled, or the flow speed may be disturbed and blockage may occur.

By interposing the star-shaped injection spacer with a plurality of tension members evenly at necessary intervals, the actual injection section forms a star-shaped section continuous in a uniform columnar shape, and there is no obstruction in the flow of the grout material. The purpose of the injection is achieved. When the tension material is a single wire, by holding the uncurtain-don at the center of the sheath pipe by the strand centerizer, the injection cross section is similarly stabilized, and there is no obstacle to change the flow rate of the grout material, so that stable injection is performed.

In the grout filling method of the water displacement in the hole (commonly referred to as "doughing") or the low-speed injection with a small-diameter injection pipe, where the uncertainty is required, the grout material is diluted by groundwater flow near the fixing ground. However, there was a concern that the required grout strength could not be obtained, but this has been solved by the present invention. Further, according to the present invention, even when a complicated geological and moisture condition of the anchoring ground is encountered, the anchor body can be reliably anchored, and the required tension can be maintained for a long time.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference numeral 1 denotes a fixing bracket, which is a steel tubular body, and has a thread formed in the outer peripheral surface in a reverse direction from an intermediate portion to both end portions. Reference numeral 2 denotes a lower supporting plate, which is connected to the fixing bracket 1 with a screw, and transmits a sharing load from the fixing metal to the load-bearing body (bearing rod, reinforced cage) by using a supporting rod 3 and a screw. The steel cage connected and attached to the outer periphery of the cage is sandwiched and fixed between the bearing plate 9 and the upper support plate 9. The upper bearing plate 9 protects the unbonded tensile material from corrosion, and connects and fixes a sheath pipe disposed around the free length of the anchor using a material such as polyethylene as an injection pipe. The upper and lower bearing plates 2.9
Utilizing the fact that the rigidity of the fixing portion is reduced at the front surface, the load is effectively transmitted to the fixing ground by obtaining the displacement in the radial direction due to the compressive force. Upper and lower bearing plates 2.9
The space between the supporting rod 3 and the reinforcing rod cage is referred to as a load-bearing body.

Reference numeral 3 denotes a bearing rod, which has a material and a cross-sectional area at the upper part of the fixing bracket 1 which can sufficiently resist a required pulling force of the anchor. The supporting rod 3 has fine irregularities on the surface of the steel pipe to enhance the adhesion to the grout material. A reinforcing bar is sandwiched and fixed between the upper supporting plate 2 and the lower supporting plate 9 so as to surround the supporting rod.

4 is a bottom cover, 5 is a pressure grip, 6
Denotes a protrusion provided on the peripheral surface of the fixing bracket, 7 denotes a grout material discharge hole, and 8 denotes a fixing pedestal with a through hole for fixing the crimping grip 5.

Reference numeral 10 denotes a reinforcing bar cage, which has a plurality of narrow transverse bars P
It is located in the longitudinal direction of the C steel material group, and is wound around the outer periphery thereof with a restraining bar like a fine spiral bar to be integrated. In addition, instead of spiral muscles,
A plurality of independent ring streaks and reinforcing members such as square, octagonal, and elliptical shapes may be attached. Further, the cage can be formed by using a corrosion-resistant material such as carbon fiber or glass fiber instead of the reinforcing bar.

Reference numeral 11 denotes a tensile member made of unbonded PC steel wire, the end of which is penetrated through the through hole of the fixing base 8 to press the crimping grip 5, and receives a tensile force on the fixing base. 1
Reference numeral 2 denotes a star-shaped injection spacer which secures a star-shaped columnar cross-section for stabilizing the injection efficiency of the sheath pipe 13 for corrosion protection and injection for covering the unbonded tension member 11 (uncurtain don), and a plurality of tension members 11. It is made of steel or other material for uniformly restraining the unbonded tension member 11 in order to prevent twisting in the sheath. The unbonded tension member 11 is sandwiched between a plurality of unbonded tension members 11 at appropriate intervals during assembly of the uncurtain don. Install.

14 is a strand centerizer,
When using a single wire unbonded tensile material 11, it is positioned at the center of the sheath pipe 13 for injection, and is made of a hollow steel triangular prism made of PC steel or another material that stabilizes the injection efficiency and prevents the tensile material 11 from being twisted. It has the structure of

[0027]

[Working example] In the present invention, the fixing bracket 1 and the supporting rod 3 in the load-bearing body serve as a load transmitting shaft, and the outer peripheral surface is attached to the grout material and the upper and lower supporting plates 2 provided on the load-bearing body.・
9 has a composite structure in which the load is transmitted by the bearing force. The fixing bracket 1 and the bearing rod 3 have sufficient compressive strength against the axial force distribution at the time of fixing, and in order to secure a wide peripheral frictional resistance even when the strength of the ground G such as soft rock is small.
A sufficient load can be transmitted in the hole axis direction.
The upper and lower bearing plates 2 and 9 use the fact that the rigidity of the fixing portion is reduced at the front surface to obtain displacement in the radial direction due to the compressive force, and the load is effectively transmitted to the ground. . Furthermore, in order to prevent the splitting fracture of the grout material due to radial compression deformation, the grout material on the front surface of the bearing plate is reinforced by the reinforcing cage 10 to increase the grout material strength and toughness (stickiness). By adopting such a composite shape of the anchor body, the front surfaces of the upper and lower bearing plates 2 and 9 are sufficiently covered, so that the grout material can be easily wrapped and filled, as well as adhesion of mud and grease during insertion of the anchor body. The effect of this also ensures that the pullout resistance is obtained. The grout material injection work is simplified by disposing the star-shaped injection spacer 12 and the strand centerizer 14 at appropriate intervals in the sheath pipe in order to use the sheath pipe 13 that covers the uncurtainer and protects against rust as an injection pipe. At the same time, the grout material can be reliably filled. Further, since the uncurtain don of the plurality of PC steel materials covered with the sheath pipe 13 is prevented from being twisted or crossed in the sheath pipe, the single effect at the time of tension of the tensile material 11 composed of the individual unbonded PC steel strands is reduced. It is prevented and the anchor tension as designed is set.

[0028]

As described above, the present invention has the following advantages. (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, and utilizes the property that the compressive strength of the grout material is extremely large compared to the tensile strength to transfer the tensile crack. Avoids the risk of progressive destruction. (2) The fixing bracket pedestal does not cause large displacement or buckling even if the strength of the anchoring ground is low, disperses stress in the direction of the load-bearing body at the top, and integrates the load-bearing body and grout material into the anchoring ground (anchor hole). The required anchor tensile force can be obtained by the peripheral frictional resistance with the wall), so that the anchor can cope with a wide range of anchoring ground conditions. (3) When a normal anchor encounters a fixed ground with a small strength that cannot be predicted, it compresses the weak ground too much, causing buckling failure of the anchor itself and pulling out of the anchor, etc. Changes may be forced,
The construction cost will increase, which will hinder the continuation of the business. (4) The sheath pipe is used as an injection pipe, and the grout is discharged from the grout discharge hole at the bottom of the fixture and filled all over the hole and the outside of the anchor body. It is installed inside to prevent insufficient filling of grout material. (5) The star-shaped injection spacer installed in the sheath pipe prevents twisting of a plurality of tension members in the sheath, so that there is no fear of one-sided effect when tension members are tensioned. This one-sided effect has a risk that the tension concentrates on a part of the individual tensile member and breaks even under a tension smaller than the anchor design load, but this is eliminated.

[Brief description of the drawings]

FIG. 1 is a front view of a ground anchor according to the present invention.

FIG. 2 is a central longitudinal sectional view of FIG.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 1;

FIG. 4 is a sectional view of another example of FIG. 3 for a double track.

FIG. 5 is a sectional view for a single line along the line 4-4 in FIG. 1;

FIG. 6 is a cross-sectional view showing another example of FIG. 5 for a double track.

FIG. 7 is a schematic explanatory view showing a use state of the ground anchor according to the present invention.

FIG. 8 is a central longitudinal sectional view showing a fixed state of a conventional peripheral friction anchor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fixing bracket 2 lower supporting plate 3 supporting rod 4 bottom cap 5 crimping grip 6 protrusion 7 grout discharge hole 8 fixing pedestal 9 upper supporting plate 10 steel cage 11 tensile material (unbonded PC steel strand) 12 star injection Spacer (for double track) 13 Sheath pipe (for use with injection hose) 14 Strand centerizer (for single track)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tomio Morohashi 4756 Kitahari, Tochio-shi, Niigata F-term in U & M Corporation (reference) 2D041 GA01 GB01 GC02 GC05 GC07 GC14 GD02

Claims (3)

[Claims] An unbonded tension member (11), a fixed pedestal (8) attached to one end of the tension member, and a fixed pedestal connected to the fixed pedestal with the tension member (11) inserted therethrough. Metal fittings
(1), a supporting rod (3) for enhancing the frictional resistance with the grout material, and a cylindrical reinforcing bar cage surrounding the supporting rod and connected to the upper and lower supporting plates (2) and (9). (10) A ground anchor comprising: 2. A steel material for being sandwiched by a double-tracked tension member (11) in a sheath pipe (13) for an anticorrosion and injection tube covering the tension member (11) so as to secure a continuous star-shaped columnar injection cross section. Or star injection spacers made of other materials (12)
The ground anchor according to claim 1, further comprising: 3. A sheath pipe for injecting a single wire tension member (11).
The ground anchor according to claim 1, further comprising a strand centerer (14) made of steel or other material for holding the tension member (11) in the center of the sheath, located at the center of the (13).