JPH0458853B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention is useful for fixing high-rise buildings or tower-like buildings so that they do not fall down due to earthquakes or strong winds, or for fixing underground buildings in places where the groundwater level is relatively high. Permanent maintenance is carried out to prevent buildings with deep parts from rising to the surface due to groundwater, or to prevent sliding due to uneven earth pressure acting on buildings built on slopes. The method of construction of ground anchors is to use a lightweight and flexible synthetic resin pipe for the free length sheath, which is heavy enough not to float up due to the injection material such as cement milk filled in the drilled part. The present invention relates to a method of constructing a permanent ground anchor, which includes a step of injecting and filling an injection material such as cement milk into the load-bearing body and the free length sheath in order to secure the load-bearing body and the free length sheath.

BACKGROUND ART Conventionally, so-called temporary ground anchors for supporting mountain retaining walls such as sheet piles have already been widely used and have a proven track record (see, for example, the one described in Japanese Patent Publication No. 13686/1986).

However, there is still no practical example of a full-scale permanent ground anchor, and development research is still in progress. Therefore, the reality is that there is no established construction method.

The construction method of a permanent ground anchor described in Japanese Patent Application Laid-Open No. 52-228521 uses a heavy steel pipe for the free length sheath as the structure of the anchor.
This is based on the idea that the tensile steel material disposed in the free length sheath and the load-bearing body is completely isolated from the injection material such as cement milk injected into the drilled hole.

Problems to be Solved by the Invention The assembly of a long permanent ground anchor with a total length of 20 to 30 m is completed by lying horizontally on the ground at the site, and then hung vertically using a retcher, etc. and insert it into the hole.

However, the conventional permanent ground anchor mentioned above has a free length sheath made of steel pipe and is heavy, so not only is it heavy when hanging with a retcher, but the free length sheath, which is over 10 meters long, is heavy. It often bends under its own weight when lifted up. It is not possible to insert a bent free length sheath into a drilled hole, and it is very time consuming and extremely difficult to restore a bent steel pipe (free length sheath) to its original straight state. It is.

Therefore, when hoisting the anchor assembly using a retcher, etc., it is necessary to apply strict reinforcement to prevent the free length sheath from bending, and to work with great care and caution, which saves time and effort in preparation. The problem is that it is a huge burden.

Another problem is that in narrow spaces, it is not possible to keep a long anchor assembly in a straight position, and it is not possible to secure enough space to hang the anchor assembly in a straight position.

Means for Solving the Problems (First Invention) As a means for solving the problems of the above-mentioned prior art, the construction method of a permanent ground anchor according to the present invention first uses a free length sheath as a structure of the ground anchor. As a result, we use a lightweight and highly flexible synthetic resin pipe such as polyethylene, and as a result, we use a free length sheath to compensate for the lack of weight to stabilize against the buoyant force received from the injection material filled in the hole. Injecting material 1 such as cement milk is also placed inside the load-bearing body 11.
5 was injected and filled. More specifically, as a preferred embodiment is shown in FIGS. 1 to 10 of the drawings, (a) a hole 23 of a predetermined depth is excavated in the ground 20 by a hole drill 21 using a casing pipe 22; (b) Assembling the anchor assembly 24 on the ground, temporarily inserting the anchor assembly 24 into the hole 23, and cementing the load-bearing body 11 and the free length sheath 9 made of synthetic resin. After injecting and filling the injection material 15 such as milk, the anchor assembly 24
(c) Injecting and filling the injection material 15 into the hole 23 from the bottom of the hole using the grout hose 25, and then reinstalling the anchor assembly 24 into the hole 23. (d) inserting the pressure head 2 into the upper end of the casing pipe 22;
7 is connected, the injection material 15 is injected under pressure while the casing pipe 22 is pulled up step by step, a fixed portion of a predetermined length is formed in the large diameter root 30, and then the casing pipe 22 is completely pulled out. (e) The tensile steel material 10 protruding above the ground is fixed to the structural frame 16 after introducing a predetermined tension force after construction of the structural frame 16, and is covered with the head cap 1 to perform rust prevention treatment; The structure consists of:

Function At the stage of temporary insertion of the anchor assembly 24, the hole 2
Since the specific gravity of the drilling water in 3 is low, it can be inserted reliably without increasing the weight. This temporary insertion allows the insertion of the anchor assembly 24 to be confirmed, and if the drilling accuracy is poor, the hole can be re-drilled immediately.

Since the injection material 15 is injected into the free length sheath 9 and the load-bearing body 11 in a vertical state in which the anchor assembly 24 is temporarily inserted into the hole 23, the filling performance of the injection material is good.

At the stage of main insertion of anchor assembly 24, hole 2
The anchor assembly 24 also has a free length sheath 9 and a load-bearing body 11 filled with an injection material 15 such as cement milk. Since the weight is increased by filling it with buoyancy, it can be inserted easily and securely without losing buoyancy.

(Second invention) As a means to solve the same problem as above, the construction method of a permanent ground anchor according to this invention includes a common main part that is essential to the structure of the first invention. , so to speak, the step of temporary insertion is omitted, and as the preferred embodiment is shown in FIGS. (b) Injecting and filling the injection material 15 into the hole 23 from the bottom of the hole using the grout hose 25; (c) Assembling on the ground, etc. The anchor assembly 24 suspended by the anchor assembly 24 is inserted into the hole 23 while adding weight by injecting the injection material 15 into the load bearing body 11 and the free length part 9 made of synthetic resin; Pressure head 2 is attached to the upper end of casing pipe 22.
7 is connected, the injection material 15 is injected under pressure while the casing pipe 22 is pulled up step by step, a fixed portion of a predetermined length is formed in the large diameter root 30, and then the casing pipe 22 is completely pulled out. (e) The tensile steel material 10 protruding above the ground is fixed to the structural frame 16 after introducing a predetermined tension force after construction of the structural frame 16, and is covered with the head cap 1 to perform rust prevention treatment; The structure consists of:

Function When inserting the anchor assembly 24 into the hole 23, the injection material 15 is injected to increase the weight, so even if the hole 23 is already filled with the injection material 15 such as cement milk with a high specific gravity, It can be inserted reliably without losing its buoyancy.

In addition, the free length sheath 9 of the anchor assembly 24 can be bent when being lifted up with a retcher, etc., so the free length sheath 9 can be inserted in a suitably curved state, and it can be inserted into narrow spaces. This makes construction easier.

Example Next, illustrated embodiments of the invention will be described.

First, FIGS. 1 to 10 show important process diagrams of the construction method including temporary insertion of the anchor assembly.

FIG. 1 shows a stage in which a hole-drilling machine 21 such as a rotary percution is installed on the ground 20 to be constructed, and a hole 23 for fixing the anchor is drilled using a casing pipe 22.

FIG. 2 shows the stage of temporarily inserting the anchor assembly 24 into the drilled hole 23 (actually the casing pipe 22).

This anchor assembly 24 is made of unbonded PC steel fixed to the tip bearing plate 12 with a crimp grip 13, as shown in FIG. A thick-walled steel tubular load-bearing body 11 having a rim formed on its outer circumferential surface to transmit the tension force transmitted to the tip support plate 12 to the surrounding ground and take a reaction force, and the load-bearing body 11
A thin wall (approximately
4.5mm) consisting of a free length sheath 9 made of a synthetic resin pipe such as polyethylene. The crimp grip 13 at the tip is double rust-proofed by a tip cap 17 fixed to the tip support plate 12 and a rust-preventive filler 18 such as rust-preventive oil injected into the tip cap 17.

This anchor assembly 24 includes a free length sheath 9
Although it is light because it is a synthetic resin pipe, hole 2
3 is still only filled with borehole water of low specific gravity, so it can be temporarily inserted without losing to buoyancy. On the other hand, the anchor assembly 24 is assembled while lying horizontally on the ground, and is then lifted up vertically using a retcher or the like for temporary insertion. Since 9 is a flexible synthetic resin pipe, lifting and temporary insertion work can be easily performed. Furthermore, since the temporary insertion allows the insertion to be confirmed, if the drilling accuracy is poor, the hole can be re-drilled immediately.

Next, FIG. 3 shows that the grout hose 25 is inserted deeply into the anchor assembly 24 temporarily inserted into the hole 23, that is, into the free length sheath 9 and the load bearing body 11, so as to reach the tip bearing plate 12. , injection material 15 such as cement milk from the lower end side of the anchor assembly 24
It shows the stage of injection and filling. Therefore,
The filling property of the injection material 15 is excellent. In addition, this increases the airtightness within the anchor assembly 24, and when the unbonded PC steel strand 10 to be rust-prevented is added with its own unbonded sheath, the free length sheath 9
Alternatively, a triple rust-proof structure is formed by the load-bearing body 11 and the injection material 15. In addition, the weight of the anchor assembly 24 is increased by the injection material 15, so that the insertion operation can be performed without losing buoyancy during the actual insertion later. effective against.

Next, FIG. 4 shows a step in which the anchor assembly 24 is temporarily hung out of the hole 23 after the insertion has been confirmed by the above-mentioned temporary insertion. Furthermore, FIG. 5 shows a step in which the grout hose 25 is inserted into the hole 23 until it almost reaches the bottom of the hole, and the injection material 15 such as cement milk is injected and filled from the bottom side of the hole to replace the drilling water. There is. Therefore, the filling properties of the injection material 15 are excellent, and the replacement with drilling water proceeds smoothly and reliably.

FIG. 6 shows the actual insertion of the anchor assembly 24, which had been suspended vertically with a retcher or the like after temporary insertion, into the hole 23 filled with the injection material 15 as described above. It shows the stages. Hole 2
Since the injection material 15 with a high specific gravity is filled in the anchor assembly 24, a considerably large buoyant force acts on the anchor assembly 24 to be inserted. It has a large weight (weight), so it can be inserted smoothly without losing to buoyancy, and has good workability.

Next, FIG. 7 shows that after the main insertion of the anchor assembly 24 is completed, the pressurizing head 27 is connected to the upper end of the casing pipe 22, and the pressurizing head 27 is connected to the upper end of the casing pipe 22.
Raise it by about 1/2 (about 3 m) of the anchor anchorage length (about the total length of the load-bearing body 11),
The first stage is shown in which the injection material 15 is injected under pressure through the grout hose 28, and the injection pressure forces the ground of the hole wall to expand to form a large-diameter root portion 30.
FIG. 8 shows a stage in which the casing pipe 22 is further pulled up by 1/2 of the fixing length, a second stage of pressurized injection is performed, and the formation of the large-diameter root portion 30 is completed. The load-bearing body 11 takes a reaction force to the surrounding ground through this large-diameter root portion 30.

FIG. 9 shows that the casing pipe 22 has been completely pulled out and the tensile steel material 10 that has been pulled out to the ground is placed on a pedestal 29.
The stage of curing the injection material 15 is shown. Thus, in the case of this permanent ground anchor, the injection material 15 filled into the hole 23 forms the frame and also functions as a rust preventive layer.

FIG. 10 shows the structure frame 1 after curing of the injection material 15.
6 is constructed, a predetermined tension is introduced into the tensile steel material 10, and after it is fixed to the structural frame 16, the head cap 1 is placed over the part that protrudes above the structural frame 16 to perform rust prevention treatment. It shows the stage of development.

Specifically, as shown in FIG. 12, the upper end of the free length sheath 9 is fitted inside the head sheath 7, and the structural frame 16 is cast up to the level of the top of the head sheath 7. .

A gasket 8 is installed at a position on the head sheath 7 corresponding to the upper end of the free length sheath 9, and a head support plate 6 is installed on top of the gasket 8. Therefore, air and water entering the inside of the free length sheath 9 through the gap between the head sheath 7 and the free length sheath 9 are blocked by the gasket 8.

The fixing fitting 4 and the fixing wedge 3 are set on the head bearing pressure plate 6, and a predetermined tension force is applied to the unbonded PC steel stranded wire 10 using a strong hold jack (not shown) using the control setting method of the so-called strong hold method. The PC steel stranded wire 10 is fixed to the fixing fitting 4 by the fixing wedge 3. Thereafter, the space above the injection material 15 in the free length sheath 9 is filled with a rust preventive filler 2 such as rust preventive oil or cement milk through an injection hole (not shown) of the fixing fitting 4, so that the space is completely filled.

The PC steel stranded wire 10 is cut leaving an extra length necessary for re-tensioning, and the tensile steel member 10 and the fixing fitting 4 are covered with a head cap 1.

The head cap 1 has an O-ring 5 on the flange that comes into contact with the head support plate 6, and this is attached to the head support plate 6.
It is fixed with a bolt over the top. Therefore, air or water that attempts to enter the head cap 1 through the gap between the head cap 1 and the head support plate 6 is blocked by the O-ring 5.

Further, a rust-preventing filler 2 such as rust-preventing oil or cement milk is injected into the head cap 1, and the filler is filled to the top of the cap, and the head cap 1 is placed on the head support plate 6. The rust-preventing filler 2 expels the air present in the wire when it is covered, so that the PC steel strands 10 and the fixing fitting 4 are in complete contact only with the rust-preventing filler 2. Therefore, the PC steel stranded wire 1 to be rust-prevented
0 and the fixing metal fitting 4, the effect of double rust prevention by the rust prevention filler 2 and the head cap 1 is shown.

Retensioning of the tensile steel 10 can be carried out at any time by draining the anti-rust filler 2 and removing the head cap 1.

Second Embodiment In FIGS. 13 to 19, most of the construction procedures are the same as in the first embodiment, but the anchor assembly 24 is
This figure shows a key process diagram of a permanent ground anchor construction method that omits the temporary insertion process and thus shortens the construction procedure.

That is, after a hole 23 is drilled in the ground 20 using the casing 22 and the hole drilling machine 21 (FIG. 13), a grout hose 25 is immediately inserted into the hole 23, and a grouting material 15 such as cement milk is poured from the bottom of the hole. was injected and replaced with drilling water (Fig. 14). In other words, in the first embodiment, the process jumps suddenly from the stage shown in FIG. 1 to the stage shown in FIG.

Anchor assembly 24 is then inserted into hole 23, as shown in FIG. The anchor assembly 24 is assembled in advance by lying horizontally on the ground, and the free length sheath 9 and the load bearing body 1 are assembled.
A grout hose 25 (FIG. 11) is inserted into the hole 23 deep enough to reach the tip support plate 12, and the anchor assembly 24 is hung approximately vertically using a retcher or the like and inserted into the hole 23. Along with this insertion work, the load bearing body 11 and the free length sheath 9 are injected and filled with an injection material 15 (FIG. 11) such as cement milk, thereby increasing the weight of the anchor assembly 24 and filling the injection material in the drilled hole section 23. To ensure that the anchor assembly 24 is inserted with good workability in a state where it is not affected by the buoyant force due to the anchor assembly 24.

Upon completion of insertion of anchor assembly 24,
The top end of the injection material 15 injected and filled into the free length sheath 9 almost reaches the head sheath 7 as shown in FIG.
The installation position is approximately the same as that of the

Thereafter, the large-diameter root portion 30 is formed by pressurized injection of the injection material 15, and after curing, the tensile steel material 10 is fixed to the structural frame 16, and the procedure for rust prevention with the head cap 1 is the same as in the first embodiment. be.

Effects of the present invention As described above in conjunction with the embodiments, the method for constructing the permanent ground anchor according to the first and second inventions of this application is to assemble the permanent ground anchor while lying approximately horizontally on the ground. When lifting the anchor assembly 24 with a retcher or the like, the long free length sheath 9 made of synthetic resin can be hung while elastically curving by utilizing its flexibility, making construction easy even in a narrow site. Moreover, when suspended vertically, the free length sheath 9 restores to its original shape and becomes straight, so insertion into the hole 23 is very easy and construction can be performed with high precision and quality.

Further, the method for constructing a permanent ground anchor according to the first invention includes a step of temporary insertion, and the method includes a step of temporarily inserting the anchor assembly 2.
4 can be temporarily inserted into the hole 23 to confirm the insertion.
If the drilling accuracy is poor, the hole can be re-drilled immediately to ensure high quality and accurate construction.

According to the construction method of the ground anchor according to the second invention, the construction period can be shortened by omitting the step of temporary insertion, and the entire anchor assembly 24 at the time of insertion is still filled with the injection material 15. If the upper half of the anchor assembly 24 is curved due to the flexibility of the free length sheath 9 made of synthetic resin, it is possible to insert the anchor assembly 24 in a curved manner. However, it is possible to carry out construction that makes good use of small spaces.

[Brief explanation of the drawing]

Figures 1 to 10 are important process diagrams of the construction method according to the first embodiment of this invention, Figure 11 is an overall structural diagram of the installed permanent ground anchor, and Figure 12 is the structural details of the anchor head. 13 to 19 are important process diagrams of the construction method according to the second embodiment. 22...Casing pipe, 21...Drilling machine,
23... hole, 25... grout hose, 15...
Injection material, 24... Anchor assembly, 27... Pressure head, 30... Large diameter root, 10... Tensile steel material,
9... Free length sheath, 15... Injection material, 7...
Head sheath, 8...Putskin, 6...Head bearing plate, 3...Fixing wedge, 4...Fixing metal fitting, 5...
O-ring, 2... Rust-preventing filler, 1... Head cap, 16... Structural frame (concrete).

Claims (1)

[Claims] 1 (a) Hole drilling machine 21 using casing pipe 22
(b) Assembling an anchor assembly 24 on the ground, temporarily inserting this anchor assembly 24 into the hole 23, and then drilling a hole 23 to a predetermined depth in the ground 20; (c) inserting the grout hose 25 into the hole 23; (d) inserting the pressurizing head 2 into the upper end of the casing pipe 22;
7, and pressurized injection of the injection material 15 while pulling up the casing pipe 22 in stages, forming a fixed portion of a predetermined length in the large diameter root 30, and then pulling out the entire casing pipe 22; (E) After the construction of the structural frame 16, the tensile steel member 10 protruding above the ground is fixed to the structural frame 16 after applying a predetermined tension force thereto, and is then covered with the head cap 1 for rust prevention treatment. A method of constructing a permanent ground anchor characterized by comprising steps. 2 (a) Drilling machine 21 using casing pipe 22
(b) Injecting and filling the injection material 15 into the hole 23 from the bottom of the hole using the grout hose 25; (c) On the ground. The anchor assembly 24 suspended by an assembly retcher or the like is inserted into the hole 23 while adding weight by injecting the injection material 15 into the load-bearing body 11 and the free length sheath 9 made of synthetic resin. (d) A pressurizing head 2 is attached to the upper end of the casing pipe 22.
7 and inject the injection material 15 under pressure while lifting the casing pipe 22 step by step.
(e) The tensile steel member 10 protruding above the ground is subjected to a predetermined tension after the structural frame 16 is constructed. A method of constructing a permanent ground anchor, which is characterized by comprising the steps of introducing the permanent ground anchor, fixing it on the structural frame 16, and then covering the head cap 1 to perform rust prevention treatment.