JPH112100A - Up-facing ground anchor and method for its constructing and setting in place - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground anchor which can be effectively formed as facing up to the top face of an underground cavity and which will exert a satisfactory durability after execution of works. SOLUTION: An up-facing ground anchor has a packer part 20 which is located at the anchor mouth part in such a condition as inserted into an anchor hole 50 as facing up, expands around a mouth pipe 5 accommodating a PC cable 30, and is put in tight attachment to the wall of anchor hole for holding the PC cable 30 in the hole 50. The arrangement further includes a packer injection pipe 22 laid in the mouth pipe 5 for supplying a grout material to the packer part 20, an internal grout exhaust pipe 32 which is laid in a sheath pipe 11 coupled with the mouth pipe 5 and accommodating the whole PC cable 30 and which is to exhaust the surplus portion of internal grout to outside the hole, and an external grout exhaust pipe 33 which is laid in the sheath pipe 11 and is to exhaust the surplus portion of external grout to outside the hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an upward ground anchor and a method of constructing the same, and more particularly to a ground anchor used for supporting a ground such as a top end of an underground space excavated in various types of ground and a method of constructing the ground anchor. About.

[0002]

2. Description of the Related Art In the field of civil engineering and construction, a ground anchor method connects a portion of a structure in contact with the ground and a stable support portion in the ground with a steel material such as a high-strength cable. This is a supporting method for introducing a large tensile force to the structure to stabilize the structure with respect to the ground. In the construction field, in order to ensure the safety of a building using the ground anchor method, there are legal restrictions when the building is used as a permanent anchor for supporting a building. That is, regarding the permanent support of a building, it is stipulated that a permanent anchor of a type that has been rated by the Japan Building Center be constructed in accordance with its design and construction guidelines.

FIG. 10 is a cross-sectional view showing the overall configuration of a type of permanent anchor (VSL anchor) evaluated by the Building Center of Japan at the time of installation. A permanent anchor cable 60 (hereinafter, referred to as an anchor unit) unitized in advance is inserted into the anchor hole 50 drilled in the rock. The anchor unit 60 is composed of a bundle of PC steel stranded wires (PC cables) housed in a synthetic resin corrugated sheath 61 (hereinafter, referred to as a sheath tube).
The PC cable constituting the anchor unit 60 is provided with spacers 62 attached at predetermined intervals in the longitudinal direction.
Are housed in the sheath tube 61 at predetermined intervals. Further, with respect to the longitudinal direction of the anchor unit 60, a free length portion 70 and a fixing length portion 71 determined from the anchor design are provided.

[0004] As shown, the sheath tube 61 is made of a synthetic resin tube or a stainless steel tube having a spiral corrugated surface on its surface, and the tip of the tube is easily inserted into the anchor hole of the sheath tube. Is attached. On the other hand, at the mouth of the sheath tube 61, a cable end fixed by a wedge system via a support plate 65 mounted on a concrete base 64 and a fixing tool 66 is located. This cable end is covered with a head cap 67 to increase the durability of the cable. Further, the anchor unit 60 is connected to the anchor hole 5.
The outer grout 52 is filled between the sheath tube 61 and the anchor hole wall 51 so as to keep the inside of the sheath tube 61 at zero. Further, the inner grout 53 is filled in the sheath tube 61 so that an anchor effect on the ground 54 can be obtained. Usually, the inside of the sheath tube is filled with grout milk as the inner grout 53, and after a predetermined grout strength is obtained, an anchor body portion is formed in the outer grout 52, and the strength of the outer grout 52 of the anchor body portion is a predetermined strength. When the strength is reached, a predetermined amount of tension is introduced by a tension jack (not shown) at the anchor mouth. At the stage where this tension is introduced, additional grout of the free length portion of the anchor is further performed.

[0005]

Incidentally, the permanent anchors rated by the Japan Building Center are usually designed with a predetermined downward or downward inclination.
For this reason, this type of ground anchor is not allowed to be used for excavating a rocky underground space to permanently support the top arch of the underground space. In other words, the conventional ground anchor is basically used for downward construction, and the ground anchor rated by the Nippon Building Center is also designed to be constructed downward, so that its function is properly exhibited. It was in fact not confirmed.

In order to construct this kind of permanent anchor upward, it is necessary to hold a heavy anchor unit in the anchor hole as it is until the grout solidifies with the heavy anchor unit inserted into the anchor hole. Further, when grouting the inside of the anchor upward, it is necessary to perform a filling operation so that the grout material is completely filled up to the tip (upper end) of the anchor hole.

[0007] Up to now, various upward anchoring techniques for solving these problems have been developed. For example, when the tip of the anchor reaches the inner wall of the anchor hole, the claw attached to the tip of the anchor unit is spread by the operation of a built-in spring or the like, and this claw is locked to the wall of the anchor hole, so that the tip of the anchor unit is Method of fixing the anchor to the bedrock, providing an enlarged portion at the anchor mouth, fixing the blocking holder with a hole-in anchor or resin mortar, and fixing the blocking pipe at the rear end of the anchor inside the cylinder of the blocking pipe holder A method of fixing to a vehicle with bolts has been developed.

However, the method of locking the claw to the hole wall requires an additional locking mechanism and cannot prevent the grout mortar from flowing out from the mouth during injection. In the method using a blocking pipe, it is necessary to provide an enlarged portion at the mouth portion of the anchor, a special bit for widening at the time of drilling, and a bit for an anchor hole of a normal diameter are required, and the setup of the drilling work is troublesome. There is a problem.

In a conventional ground anchor, grouting is performed by filling the grout in the hole sequentially from the distal end portion by extending the injection hose to the distal end portion of the anchor hole. However,
When constructing the ground anchor upward, the grout must gradually fill the hole from the mouth of the anchor upward. Therefore, the mouth of the anchor hole is closed at an early stage. For this reason,
Grout injection work is required while removing air from the anchor holes. That is, along with grout filling,
It is necessary to evacuate the anchor holes.

Similarly, in order to increase the durability of the anchor head portion of the installed ground anchor, it is necessary to fill the anchor head portion with rust preventive oil. It is also necessary to exhaust the inside of the head cap.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to make it possible to carry out safe construction even when constructing a ground anchor upward, and to ensure that grout work and the like can be performed. An object of the present invention is to provide an upward ground anchor and a method for constructing the ground anchor.

[0012]

In order to achieve the above object, the present invention is arranged such that it is located at an anchor mouth while being inserted into an anchor hole, and expands around a mouth tube accommodating a tension member therein, A packer portion that can be in close contact with the anchor hole wall, a packer injection tube housed in the mouth tube for supplying grout material to the packer portion, and a sheath tube that is connected to the mouth tube and houses the entire tension member. An internal grout exhaust pipe that is piped and discharges excess internal grout to the outside of the hole, and an external grout exhaust pipe that is piped inside the sheath pipe and discharges excess external grout to the outside of the hole.

[0013] As a construction method, an anchor unit in which a tension member is accommodated in a sheath tube connecting a mouth tube having a packer portion attached to the periphery of the tube is inserted into an anchor hole drilled upward with respect to the ground. In a state in which a grout material is supplied to the packer portion through a packer injection pipe provided in the mouth pipe and the packer portion is brought into close contact with an anchor hole wall and the anchor unit is held in the anchor hole. Performing internal grouting with the internal grout injection pipe, discharging excess internal grout outside the anchor hole through the internal grout exhaust pipe provided in the sheath pipe, and then using the external grout injection pipe to form the anchor hole wall. An external grout is performed between the sheath tube and the extra grout through an external grout exhaust pipe provided in the sheath tube. The grout component so as to discharge the anchor Anagai, the internal grout is characterized in that to perform the fixing of the anchor head at the stage of reaching a predetermined intensity.

In this case, it is preferable that the inner grout exhaust pipe and the outer grout exhaust pipe are piped to the vicinity of the sheath pipe tip along the tension member.

It is preferable that a rust preventive return pipe communicating with the inside of the anchor hole is provided in a head cap attached to the anchor opening so as to cover the anchor head when the anchor head is fixed.

As a construction method, a rust-preventive material return pipe communicating with the inside of the anchor hole is provided in a head cap attached to cover the anchor head, and the rust-preventive material is filled into the head cap. It is preferable that the return of the rust preventive material from the rust preventive material return pipe be confirmed to check the filling state of the rust preventive material into the anchor hole.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the upward ground anchor of the present invention and a construction method thereof will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing a state at the time of completion of the construction of the upward ground anchor of the present invention. 2 and 3 are partial cross-sectional views shown for explaining the internal configuration of the anchor support packer portion and the expanded state of the packer portion. 4 to 6 are cross-sectional views showing the cross-sectional configuration of the anchor unit of the ground anchor at each cross-sectional line position shown in FIG.

FIG. 1 is an overall sectional view showing the internal configuration of the upward ground anchor in a state where the construction is completed, with a part of the longitudinal direction being omitted. As shown in the figure, the upward ground anchor 1 includes an anchor unit 10 inserted into an anchor hole 50 and an anchor fixing part 40. The anchor unit 10 includes an anchor support packer portion 20 that holds the entire anchor unit 10 in the anchor hole 50 until the outer grout 52 solidifies;
The sheath tube 11 is connected to the anchor support packer unit 20 and has the PC cable 30, the grout injection tube 24, the injection hose 31, and the exhaust hoses 32 and 33 housed therein, and the distal end is closed by the distal end cap 63. Become.
On the other hand, an exhaust pipe 47 to be described later is accommodated in the head cap 67 that covers the anchor head 40.

Among these configurations, the configuration of the anchor support packer section 20 for holding the anchor unit 10 in the anchor hole 50 before injecting the external grout will be described with reference to FIGS. An anchor support packer portion 20 is formed near the anchor mouth 2 of the sheath tube 11 of the upward ground anchor 1 of the present invention. The anchor support packer section 20 includes a water stop area 21 formed inside the mouth pipe 5, a packer injection pipe 22 laid in the water stop area 21, and a cylindrical packer formed at an outer peripheral portion of the mouth pipe 5. And part P.

Of these, the water stop area 21 is accommodated in the mouth pipe 5 of the anchor mouth 2 so as to be kept parallel to the anchor at a predetermined distance in the longitudinal direction of the anchor.
It is formed at a portion sandwiched between two resin seal disks 23. A plurality of circular openings (not shown) are provided in the seal disk 23 in the water stop area 21. By using the circular openings as spacers, a plurality of unbonded PC cables 30, an injection hose, an exhaust hose, and The packer injection tube 22 is held in position in the mouth tube 5. Also,
The seal disk 23 also serves as an end closing plate when the water-stop area 21 is filled with jet cement. The anchor support packer section 20 is assembled at a predetermined position of the mouth pipe 5 in the factory when the PC cable 30 and each injection hose are assembled in advance.

The injection outlet 22a of the packer injection pipe 22 provided in the water stop area 21 is located at the side of the mouth pipe 5 at an intermediate position of the water stop area 21. A check valve valve (not shown) is attached in the path of the packer injection pipe 22 to prevent backflow of grout. The front end outlet 24a of the external grout injection pipe 24 is located at the side of the mouth pipe 5 at the front position of the seal disk 23. A tubular packer P is attached so as to cover the mouth pipe 5 from the outer periphery around the front end position of the external grout injection pipe 24 and the rear end portion of the water stop area 21. The packer P is made of a seamless cylindrical woven cloth, and both ends thereof are fixed to the outer surface of the mouth tube 5 by a heat-shrinkable tube 25 so as to maintain airtightness. Further, a steel band 26 is wound around the outer periphery of the heat shrink tape 25,
The end of the packer is not easily detached from the mouth tube 5. The packer P is made of a dense woven fabric made of thick synthetic fiber, and has a structure in which the grout milk 27 does not leak out even when the grout milk 27 is filled therein. As the packer material, besides cloth, it is also possible to use synthetic resin products such as polyurethane film, etc. It is necessary to.

FIG. 3 shows a packer injection pipe 2
FIG. 4 is a state explanatory view showing a state in which grout milk 27 is filled through the packing 2 and a packer P is expanded. As shown in the figure, when the grout milk 27 is filled in the packer P and the packer portion P expands into a spindle shape, the expanded portion of the packer P comes into close contact with the anchor hole wall 51 and the gap between the hole wall 51 and the packer P is increased. Large friction occurs between them. Thereby, the whole weight of the anchor unit 10 can be held by the anchor hole wall 51.

FIGS. 4 to 6 are sectional views showing the arrangement of the PC cable 30 at the tip of the packer P and the anchor unit 10, and the arrangement of each injection hose and exhaust hose.
As shown in FIGS. 4 and 5, in the present embodiment, eight PC cables 30 are wired so as to be held by the seal disk 23 in the mouth tube 5. In the present embodiment, seven unbonded strands having a predetermined diameter are used as the PC cables 30. Further, the PC cable 30
The inner grout injection hose 31 and the inner grout exhaust hose 3 are located at substantially the center of the cross section of the mouth pipe 5 so as to be surrounded by
2. The pipe is formed in a substantially triangular shape so that the external grout exhaust hose 33 contacts. Further, an outer grout injection pipe 24 having a diameter larger than the diameter of the three hoses is also accommodated in contact with the inner side surface of the mouth pipe 5. The three hoses arranged at the center position are made of pressure-resistant resin hoses, and the outer grout injection pipe 24 and the packer injection pipe 22 use ERW pipes.

FIG. 5 shows grout milk 27 in packer P.
FIG. 9 is a cross-sectional view showing a center position of the packer P that comes into contact with the anchor hole wall 51 in a state where the gas is injected and completely expanded. This cross section also shows the water stopping material 3 filled in the water stopping area 21. In this embodiment, jet cement is used as the water-stopping material 3, but various non-combustible water-stopping materials can be used.

FIG. 6 is a sectional view showing the tip of the packer P. A sheath tube 11 is provided at the tip of a mouth tube (not shown).
A joint collar 28 is provided for coupling with the sheath tube 11, and the sheath tube 11 is mounted outside the joint collar 28. Although the outer grout injection pipe 24 and the packer injection pipe 22 are not extended to this portion, the PC cable 30, the inner grout injection hose 31, the inner grout exhaust hose 32, and the outer grout exhaust hose 33 are sheathed by a spacer (not shown). It is held at a predetermined position inside 11 and extends to the distal end of the sheath tube 11.

Next, the procedure for installing the upward anchor will be described with reference to FIGS. First, FIG. 7A shows a state in which the anchor hole 50 is drilled by a drilling rod 75 mounted on a known drilling device main body (not shown). This drilling device is a known rotary drilling device that drills by rotating the casing pipe,
A rotary percussion type in which a casing pipe is drilled by applying an impact with air pressure or hydraulic pressure can be used. After drilling to a predetermined anchor hole depth by the drilling device, the anchor hole wall 51 is cleaned, and the previously assembled anchor unit 10 is inserted into the anchor hole 50.

The distal end of the PC cable 30 in the anchor unit 10 is wired to the vicinity of the distal end cap 63 in the sheath tube 11 as shown in FIG. The distal end is fixed in the sheath tube 11 by the anchor water stopping material 72. The plurality of PC cables 30, each injection hose, and the exhaust hose are held at predetermined positions in the sheath by the spacer (not shown) as described above.

Next, the anchor unit 10 is completely inserted into the anchor hole 50 by an anchor unit insertion device (not shown). Then, a grout pump is connected to the packer injection pipe 22 in a state where the grout pump is connected to the temporary receiving table (not shown) installed at the anchor mouth 2, and the grout pump is operated to pressurize the grout milk 27 into the packer P. The injection pressure is preferably 0.5 to 1.0 kgf / cm ² . Upon completion of grouting into the packer P, the mouth portion of the anchor hole 50 is securely sealed. In addition, Packer P
Due to the development of the strength of the grout injected into the inside, the anchor unit 10 can stand up in the anchor hole 50 in an upward state (see FIG. 7C). Subsequently, a grout pump is connected to the internal grout injection hose 31 as shown in FIG. Then, the internal grout 53 is gradually performed from the anchor opening 2 into the sheath tube 11 by the operation of the grout pump.

FIG. 8D shows a state in which the inner grout 53 is partially filled in the sheath tube 11. When the upper surface of the internal grout 53 reaches the tip of the internal grout exhaust hose 32, a part of the internal grout 53 is discharged to the outside of the sheath tube 11 through the exhaust hose 32. By confirming the pressure value of the pressure gauge of the grout pump and the return from the exhaust hose 32 in this way, it is possible to confirm whether or not the internal grout has been reliably performed in the sheath tube 11. The pressure injection as the secondary injection is continuously performed. When the injection of the internal grout 53 is completed, the external grout is injected from the external grout injection pipe 24. As the grout surface of the outer grout 52 is injected, as shown in FIG.
As shown in (2), it rises along the hole wall 51, and part of the crack penetrates into the crack on the surface of the hole wall 51. When the injection is completely completed to the upper end of the anchor hole 50, a part of the grout flows into the sheath tube 11 through the communication hole 63a provided in the tip cap 63. Then, a part of the grout is discharged out of the anchor hole as a return through the external grout exhaust hose 33 attached in the sheath tube 11. After confirming this state, the exhaust hose 33 is sealed, and pressurized injection (secondary injection: injection pressure of 1.0 to 2.0 kgf / cm ² ) is continued at a predetermined grout pressure. As a result, the cracks in the rock are surely filled with grout.

Next, the fixing operation of the anchor head 40 will be described. After organizing the hose of the anchor mouth 2, the supporting plate 41 and the fixing plate 42 are attached to the anchor mouth 2. The support plate 41 and the fixing plate 42 are held by a temporary support table (not shown) attached to a mouth portion. When the internal grout reaches a predetermined strength, the tension jack 45 is attached to each PC cable 30 of the fixing plate 42 (see FIG. 9G). The center hole type tension jack 4 is operated by the operation of a hydraulic pump (not shown).
5 is driven to apply a predetermined tension to the PC cable 30. In a state where a predetermined tension is applied, a wedge (wedge) is applied to securely fix the PC cable 30 to the fixing plate 42 portion.

When the tension fixing of the PC cable 30 is completed, as shown in FIG. 1 and FIG.
The head cap 67 is attached so as to cover the entire fixing end of the “0”. The head cap 67 is provided with an exhaust pipe 47 that penetrates through the fixing plate 42 and communicates with the anchor hole and serves as a rust preventive return pipe that also serves as an air vent. A grease nipple 48 is provided on a side surface of the head cap 67, and a grease supply hose 4 from a grease pump 49 is attached to the grease nipple 48.
6 are connected. Then, grease G as a rust preventive is filled in the head cap 67 by applying a predetermined pressure. When the head cap 67 is sufficiently filled with the grease G, a part of the grease G also penetrates into the mouth portion of the sheath tube 11 through the through hole 42a formed in the fixing plate 42. Grease G is filled into the gap between the mouth tubes of the sheath tube 11. At this time, the internal air escapes from the exhaust pipe 47. Thereafter, when the grease G is completely filled in the mouth portion, a part of the grease G is obtained from the exhaust pipe 47 as a return. When this return is confirmed, the exhaust pipe 47 is closed with the closing bolt B, and the head cap 67 and the entire anchor opening 2 are greased.
(See FIG. 9 (i)). Thereby, rust prevention of the anchor head 42 can be achieved. In this way, by using the upward anchor of the present invention, the anchor unit 10 can be securely held in the anchor hole 50 before grouting, and the head cap 67 can be held even in the state where it is installed upward. The used grease can be reliably injected, and the anchor head and the anchor hole opening 2 can be sealed. In addition, high durability can be ensured.

[Brief description of the drawings]

FIG. 1 is an overall cross-sectional view of an embodiment of an upward ground anchor according to the present invention.

FIG. 2 is a partial cross-sectional view showing an anchor supporter (when an anchor hole is inserted).

FIG. 3 is a partial cross-sectional view showing the anchor supporting packer portion (when the packer is expanded).

FIG. 4 is a cross-sectional view of the ground anchor taken along the line IV-IV in FIG. 3;

FIG. 5 is a cross-sectional view of the ground anchor shown along the line VV in FIG. 3;

6 is a cross-sectional view of the ground anchor shown along the line VI-VI of FIG. 3;

FIG. 7 is a construction state diagram (part 1) illustrating the construction order of upward ground anchors.

FIG. 8 is a construction state diagram (part 2) showing the construction order of the upward ground anchors.

FIG. 9 is a construction state diagram (part 3) showing the construction order of upward ground anchors.

FIG. 10 is an overall sectional view showing an example of a configuration of a conventional permanent anchor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upward ground anchor 5 Mouth pipe 10 Anchor unit 11 Sheath pipe 20 Anchor support packer part 22 Packer injection pipe 24 External grout injection pipe 30 PC cable 31 Internal grout injection hose 32 Internal grout exhaust hose 33 External grout exhaust hose 40 Anchor head

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Yamada 2 Tobanshima Construction Co., Ltd., Sanbancho, Chiyoda-ku, Tokyo (72) Inventor Tomoyoshi Shibata 2 Tobanjima Construction, Sanbancho, Chiyoda-ku, Tokyo (72) Inventor Hiroshi Kaku 2 Tobanjima Construction Co., Ltd., Sanbancho, Chiyoda-ku, Tokyo (72) Inventor Kaoru Kobayashi 2 Tobanjima Construction Co., Ltd., Sanbancho, Chiyoda-ku, Tokyo (72) Invention Person Hirotaka Nakahara 2 Sanbancho, Chiyoda-ku, Tokyo Tobishima Construction Co., Ltd. (72) Inventor Kazunobu Matsumoto 2nd Sanbancho, Chiyoda-ku, Tokyo Tobishima Construction Co., Ltd. (72) Inventor Masayuki Tsutsui Chiyoda, Tokyo No. 2, Sanbancho, Ward Tobishima Construction Co., Ltd.

Claims (5)

[Claims] 1. A packer portion which is located at an anchor mouth portion in a state inserted into an anchor hole, expands around a mouth tube accommodating a tension member therein, and can be brought into close contact with an anchor hole wall. A packer injection pipe that is piped into the mouth pipe to supply grout material, and an internal grout that is connected to the mouth pipe and is piped into a sheath pipe that houses the entire tension member, and that discharges excess internal grout outside the hole. An upward ground anchor comprising: an exhaust pipe; and an external grout exhaust pipe that is provided in the sheath pipe and that discharges excess external grout outside the hole. 2. An anchor unit in which a tension member is accommodated in a sheath tube connecting a mouth tube with a packer mounted around the tube is inserted into an anchor hole drilled upward with respect to the ground. A grout material is supplied to the packer part via a packer injection pipe provided in the pipe, the packer part is brought into close contact with the anchor hole wall, and the anchor unit is held in the anchor hole. While performing the internal grout, the excess internal grout is discharged out of the anchor hole through the internal grout exhaust pipe provided in the sheath pipe, and then, the outer grout injection pipe is used to separate the anchor hole wall and the sheath pipe. An external grout is performed in the meantime, and an excess external grout is removed from the anchor hole through an external grout exhaust pipe provided in the sheath pipe. So as to discharge, the construction method of the upward ground anchors the internal grout, characterized in that to perform the fixing of the anchor head at the stage of reaching a predetermined intensity. 3. The upward ground anchor according to claim 1, wherein the inner grout exhaust pipe and the outer grout exhaust pipe are piped along the tension member to near the distal end of the sheath pipe. 4. A rust-preventive material return pipe communicating with the inside of the anchor hole is provided in a head cap attached to an anchor mouth so as to cover the anchor head. Upward ground anchor. 5. A rust-preventive material return pipe communicating with the inside of the anchor hole is provided in a head cap attached so as to cover the anchor head, and the rust-preventive material is filled when the rust-preventive material is filled in the head cap. 3. The method according to claim 2, wherein the return of the rust preventive material from the return pipe is confirmed to check the filling state of the rust preventive material in the anchor hole.