JPH09287137A - Ground anchor and execution method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground anchor which can securely support an underground structure prior to the excavation of the ground. SOLUTION: A first anchor body having a tensile steel material 11 as a core is constructed at the front end position of a tendon 10 inserted in the anchor hole to anchor the tensile steel material 11 in the ground in advance and form the first anchorage part 20. A sheath 12 covering the tensile steel material 11 is provided to form a specified scope in the longitudinal direction from the first anchorage part 20 as a free length 21 of the anchor. A corrugated sheath 15 is fitted so as to extend without disconnection from the sheath 12 and a sheath 13 is contained in the inside. A second anchor body having the tensile steel material 11 as a core is formed in the corrugated sheath 15. This second anchor body is formed as the second anchorage part 22 for the anchorage end in the ground to retain an introduced prestress in the tensile steel material 11 when a specified tension is introduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground anchor and a construction method therefor, and more particularly to a ground anchor capable of reliably fixing an underground structure or the like by two anchor bodies formed in the ground and the ground anchor. It relates to a construction method for constructing efficiently.

[0002]

2. Description of the Related Art When excavating the surroundings of an underground structure such as an existing pipeline, a ground anchor is often installed to prevent the underground structure exposed on the surface of the ground from being lifted. By the way, the anchor head of the ground anchor is generally fixed on a pedestal or the like on the ground. For this reason, when an anchor anchoring part is provided on a part of the underground structure to support it, the part that will become the anchor anchoring part of the underground structure is excavated until it is exposed to the ground surface, and a ground anchor is constructed. I had to do it. Therefore, in the process of excavating the underground structure, the structure is temporarily placed in an unsupported state, the member stress becomes excessive, and the structure may be destroyed.

In order to solve this problem, the applicant has created two anchor anchoring portions in the ground, and is capable of introducing a predetermined anchor tension force between these two anchor anchoring portions. The construction method is proposed (refer to Japanese Patent Application No. 8-40463).

A construction method of this ground anchor will be described with reference to FIG. First, as shown in FIG. 5A, the anchor hole 1 having a depth corresponding to the designed anchor length.
The hole 30 is drilled while protecting the hole wall with the casing pipe 131. Then, the inside of the casing pipe 131 is washed with water, and the sheaths 112, 113 are placed at predetermined positions on the tensile steel material 111.
The tendon 110 fixed to the casing pipe 131
It is inserted inside (see FIG. 5 (b)). At this time, the sheath 11
A known cloth packer 115 in a folded state is mounted on the anchor mouth side of No. 2. From this state, primary injection and secondary injection as "first-stage injection" are performed. First, primary injection is performed to fill the grout material into the casing pipe 131. Further, a predetermined number of casing pipes 131 are pulled out, a pressure head 133 is attached to the mouth of the casing, and a secondary injection (head pressure) is performed by a pump (not shown).
I do. Thereby, the first fixing long portion 12 at the tip of the anchor
An anchor body is created at 0 (see FIG. 5 (c)).

Then, the casing pipe 131 is sequentially withdrawn (primary withdrawal) while the grout is injected around the sheath 112 without pressure. When the casing pipe 131 is pulled out to the hole mouth side end position of the sheath 112, cement milk is injected under pressure into the cloth packer 115 to close the anchor hole 130 (see FIG. 5D). After the blockage, the casing pipe on the mouth side of the cloth packer 115 is washed with water to remove the slime, the hole wall, and stains on the surface of the tensile steel material 111. And the first fixing part 1 at the tip of the anchor
A predetermined curing period is given until the strength of the anchor body is exhibited. Then, the casing pipe 131 is pulled out (secondary pulling out), and the sheath 112 is subjected to “second-stage injection”.
The second anchor body 122 is formed by injecting pressure into the anchor hole between the sheath 113 and the sheath 113 to form a second anchor body. Further, non-pressure injection is performed around the sheath 113. As a result, the grout injection of the anchor hole 130 up to the ground surface position is performed to form the surplus free length portion 123.
(See FIG. 5 (e)). Once this grout injection is complete,
A predetermined tension force is introduced into the anchor by the tension jack 141 to perform tension (see FIG. 5 (f)). Further, after a predetermined curing period, the tension jack 141 is removed and the surplus anchor length exposed on the ground is cut (Fig. 2).
(G)). By constructing the ground anchor according to the above procedure, it is possible to safely excavate the natural ground portion 143 corresponding to the surplus free length portion 123 shown in FIG. 5G after a predetermined curing period after grout injection and anchor tension work. It is possible to reliably prevent the floating of an underground structure (not shown) and the like by the properly arranged ground anchors.

[0006]

By the way, in order to surely form the above-mentioned second fixing long portion in the ground, it is necessary to surely perform the packer injection located in the middle of the anchor. Furthermore, to ensure that the second fixing long portion is formed,
It is also necessary to completely remove stains and the like on the surface of the tensile steel material.
Therefore, it is necessary to thoroughly wash the casing pipe with water. As described above, among the series of steps shown in FIG. 5, the step shown in FIG. 5D is an important step in the construction quality of the ground anchor. However, each work of the process shown in FIG. 5 (d) described above is a remote work in a thin casing pipe, and it is difficult to confirm whether or not the work is reliably performed. For this reason, it has become a bottleneck for maintaining the quality of ground anchor construction. In addition, in this construction procedure, the casing is pulled out after the second injection, but if it takes time to pull out the casing pipe, the grout may solidify, which may make it difficult to pull out the casing pipe. Further, there is a problem that the preparation for the tensioning work of the next process and the casing pulling-out work are congested on the aboveground part.

Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technique and to make it possible to reliably provide two anchor anchoring portions in the ground, and an efficient ground anchor. It is to provide a construction method that enables good construction.

[0008]

In order to achieve the above object, a tensile steel material inserted into an anchor hole drilled in the ground and a fixing material injected into the anchor hole using the tensile steel material as a core material. A first anchoring length portion composed of a first anchor body formed at the tip end position of the tensile steel material by
Of the tensile steel material from the fixing length portion to the anchor hole opening portion to form a free length portion of the anchor by covering a predetermined range in the longitudinal direction of the tensile steel material; A second anchor body which is provided at a predetermined position and surrounds a predetermined range in the longitudinal direction of the tensile steel material, and a second anchor body formed by a fixing material injected into the insulating tube using the tensile steel material as a core material. A fixing length part, and when a predetermined tension is introduced into the tensile steel material, the tension is held between the first fixing length part and the second fixing length part located in the ground. It is characterized by doing so.

At this time, it is preferable to form an extra free length portion between the second fixing length portion and the anchor hole opening portion.

When the above-mentioned ground anchor is constructed, an anchor hole is drilled in the ground and the inside of the anchor hole is
In the anchor hole, insert a tendon to which at least a barrier coating for covering a predetermined area in the longitudinal direction of the tensile steel material and an insulating pipe adjacent to the barrier coating and surrounding a predetermined area in the longitudinal direction of the tensile steel material are attached. The first anchor is formed into a first fixing length portion by using the tip position of the tensile steel as a core material, and the tip is fixed to the first fixing length portion. A predetermined tension is introduced into the tensile steel material, the tension state is maintained and a second injection is performed into the insulating pipe, and a second anchor body having the tensile steel material as a core material is formed in a predetermined range in the insulating pipe. A second fixing length portion, and the tension introduced into the tensile steel material is held between the first fixing length portion and the second fixing length portion.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, one embodiment of the construction of a ground anchor and the construction method thereof according to the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a tendon 10 of a ground anchor 1 used in the present invention (in this specification, a unit in which a predetermined number of anchor tension members of a predetermined length are bundled and inserted into an anchor hole is called a tendon. ) And a cross section of the ground anchor 1 in the state where the tendon 10 is installed in the ground (hereinafter, the anchor completed in the ground is referred to as the ground anchor 1, and the state of the tension member unit is referred to as the tendon 10).

The tendon 10 shown in FIG. 1 (a) comprises a tensile steel material 11 having an anchor length of a predetermined length, and a sheath as a shield covering body in which the tensile steel material 11 is inserted and fixed at a predetermined position. 12, 13 and a corrugated sheath 15 as an insulating tube having a length from the end of the sheath 12 to the anchor mouth and accommodating the sheath 13, and a hose for supplying a fixing material into the corrugated sheath 15. Group 1
It is composed of 6 and 18. Of these, tensile steel 11
The number of steel wires and the cross-sectional area of the steel wire are designed in such a range that the designed anchor force does not exceed the allowable anchor tensile force. For the tensile steel material 11, PC steel wire, deformed PC steel wire, PC steel stranded wire,
Various wire rods and rods having high durability such as PC steel rods can be used. In addition, in the present embodiment, the sheaths 12 and 13 are used as the barrier coatings. This sheath 1
2 and 13 are the grout material and the tendon 10 when the grout material is filled in the anchor hole into which the tendon 10 is inserted.
It plays a role of cutting the edge of and holding the unbonded state.
Constituting No. 3. The sheaths 12 and 13 are made of a synthetic resin tube such as polyester, and rust preventive oil or the like is filled in the sheaths. Thereby, the tensile steel material 11 inserted in the sheath position functions as an unbond member. Although not shown in the figure, instead of the sheaths 12 and 13, grease having a sufficiently high viscosity is applied to the surface of the tensile steel material 11 to a predetermined thickness, and the periphery thereof is covered with an anticorrosion tape to cover the structure. May be

Further, a corrugated sheath 15, which is an insulating tube, is attached to the mouth side of the sheath 12. The corrugated sheath 15 is a known steel pipe whose surface is corrugated along the longitudinal direction of the pipe. Corrugated sheath 1
The diameter of 5 is set so that a sheath 13 and a fixing material supply hose 16 described later can be housed therein. As shown in FIG. 1A, the entire length reaches the mouth of the sheath 13, and the corrugated sheath 15 is provided with water-stop caulking 17 at both ends. Further, a fixing material supply hose 16 is inserted from the mouth side to the inside of the corrugated sheath 15. The fixing material supply hose 16 is a supply hose for filling the corrugated sheath 15 with cement milk as a fixing material. Further, a fixing material discharge hose 18 is inserted at the mouth of the corrugated sheath 15. From the fixing material discharge hose 18, the corrugated sheath 15
The return liquid filled with cement milk is discharged. By measuring the specific gravity of this return liquid, it can be confirmed whether or not the cement milk is reliably filled in the corrugated sheath 15. As the insulating pipe, a corrugated sheath 15 may be replaced by a spiral steel pipe having a convex flange formed around the outer peripheral surface thereof. In addition, the fixing material discharge hose 18 is omitted without providing the water blocking caulk 17 on the ground, and the fixing material is filled into the corrugated sheath 15 by the fixing material supply hose 16.
It is also possible to overflow the corrugated sheath 15 from the mouth to a pit provided by excavating it above the ground, and check the density of the fixing material at the pit position.

In the corrugated sheath 15, a sheath 13 as a second barrier coating is housed in a state of being attached to the tensile steel material 11. The sheath length of the sheath 13 is
As shown in FIG. 1B, after the ground anchor 1 is constructed, the ground excavation work is set to correspond to the rock depth of the excavated portion removed from the ground to the excavator.

Next, the construction of the ground anchor 1 constructed in the ground will be described with reference to FIG. 1 (b).
Cement-based grout as a fixing material is pressure-injected into the anchor hole around the tip of the ground anchor 1 to form an anchor body using the tensile steel material 11 as a core material. This anchor body functions as the first fixing unit 20. Further, grout material is injected without pressure into the anchor holes around the sheath 12 and the corrugated sheath 15 as the barrier coating. As a result, the natural ground, the sheath 12, and the corrugated sheath 15 are integrated. At this time, sheath 1
The tensile steel material 11 and the ground in 2 are reliably cut off and the edges are cut, and the unbonded state is maintained. As a result, the anchor free length portion 21 is formed at the position of the sheath 12. A second fixing length portion 22 is formed in the portion of the corrugated sheath 15 between the water blocking caulking 17 and the sheath 13 where the tensile steel material 11 is exposed. This second fixing portion 22
Is the tensile steel material 11 when the corrugated sheath 15 is empty.
Cement milk is injected in a tense state to form a predetermined anchor body. In addition, cement milk is also injected between the sheath 13 and the corrugated sheath 15 around the sheath 13 in order to integrate them. This portion becomes an extra free length portion 23 between the second fixing length portion 22 in the corrugated sheath 15 and the ground surface. In this surplus free length portion 23, since the edge between the cement milk and the tensile steel material 11 is cut, the corrugated sheath 15 is removed to solidify the cement milk portion in the excavation work from the ground to the excavator having a predetermined depth. The tensile steel material 11 can be easily removed by crushing.

It is preferable that the fixing material for forming the anchor body portion is blended so that the compressive strength of the mortar or cement paste is equal to or higher than a predetermined designed strength when the anchor is tensioned and when the design ground load is applied. Also,
In the first fixing length portion 20 and the second fixing length portion 22, the tensile steel material 1
Since the No. 1 and the fixing material directly adhere to each other, it is important to set the grout strength so that a predetermined adhesion strength can be exerted in this portion and to improve the ground of the surrounding ground.

Next, the ground anchor 1 shown in FIG.
A procedure for constructing the ground will be described with reference to FIG. First, as shown in FIG. 4A, an anchor hole 30 corresponding to the designed anchor length is drilled in the ground. The anchor holes 30 are drilled using a drilling machine (not shown) mounted on a crawler type base machine installed on the ground. With this boring machine, the boring rod is press-fitted into the ground by applying rotation and pushing force to the casing pipe 31 having the rod housed therein, and an anchor hole 30 of a predetermined length whose bore wall is supported by the casing pipe 31 is formed. To construct. The diameter of the casing pipe 31 is preferably set to a diameter suitable for the number of designed anchors and the cross-sectional area.

In drilling the anchor hole 30, when drilling the anchor hole 30 to a position deeper than the groundwater level,
In order to prevent the groundwater from flowing backward and the ground to be disturbed, it is preferable to take a predetermined countermeasure work as the pressure-reduced drilling hole. For example, using a Kronen bit that can prevent backflow of groundwater, a bit with a check valve, or drilling with a check valve at the mouth of the anchor hole 30,
It is preferable to prevent the spouting of groundwater from the hole mouth. When the anchor hole 30 is drilled to a predetermined depth, the inside of the anchor hole 30 is washed with water to remove the earth and sand remaining on the hole bottom and the slime adhering to the hole wall.

Next, as shown in FIG. 2B, the sheath 12 and the corrugated sheath 1 are provided at predetermined positions of the tensile steel material 11.
5 is attached to the tendon 10 (as an example, FIG.
(See (a)) is inserted into the anchor hole 30. Subsequently, as "first-stage injection", grout material as a fixing material is filled in the casing pipe 31 (primary injection). Further, in this state, a casing pulling jack (not shown) is arranged at the anchor base position to pull out the casing pipe 31. After removing a predetermined number of casing pipes 31, a pressure head 33 is attached to the rear end of the casing extracting jack, and a secondary injection is performed by a pump (not shown) at a pressure P = ² to 5 kgf / cm ² . As a result, an anchor body is formed in the first fixing long portion 20 at the anchor tip position (see FIG. 2 (c)).

Next, the sheath 12 and the corrugated sheath 1
While grouting around 5, casing pipe 3
Pull out 1 sequentially. For the grout injection of this portion, either the pressure injection or the non-pressure injection may be selected depending on the soil quality. A curing period of about 1 day is allowed until the casing pipe 31 is completely pulled out and the grout injected into the anchor hole reaches a predetermined strength. Then, the tension jack 41 is installed at the anchor hole on the ground. A predetermined tension force is introduced to the tendon 10 whose one end is fixed to the first fixing length portion 20 by the tension jack 41 to perform anchor tension (see FIG. 2D). Furthermore, “second-stage injection” is performed in which the corrugated sheath 15 is filled with cement milk. As a result, the second fixing long portion 22 is formed in the corrugated sheath 15. Further, the surplus free length portion 23 is formed by injecting also around the sheath 13 in the corrugated sheath 15 and performing grout injection of the anchor hole 30 up to the ground surface position. After a predetermined curing period, the tension jack 41 is removed, and the excess anchor length exposed on the ground is cut (see FIG. 2 (e)), and the ground portion 43 corresponding to the surplus free length 23 is removed. Drilling can be done. At this time, the tensile force introduced to the ground anchor 1 can securely hold the underground structure on the ground.

Next, another embodiment of the ground anchor of the present invention and its construction method will be described with reference to FIGS. FIG. 3A shows a tendon 10 having a configuration in which the surplus free length portion is set to be sufficiently long as compared with the tendon 10 shown in FIG. 1A. As with the tendon 10 shown in FIG. 1A, the tendon 10 covers a tensile steel material 11 having an anchor length of a predetermined length and a predetermined range in the longitudinal direction from the tip of the tensile steel material 11 in an unbonded state. A sheath 12 as a blocking cover, a corrugated sheath 15 as an insulating pipe that covers a tensile steel material 11 in a predetermined range in the longitudinal direction corresponding to the second anchoring long portion of the ground anchor 1 (see FIG. 3B), and this corrugate It is composed of a group of hoses 16 and 18 for supplying a fixing material into the sheath 15, and a sheath 13 as a barrier coating for covering the tensile steel material 11 from the end of the corrugated sheath 15 to the anchor mouth position in an unbonded state. ing.

The sheath 12 has the same structure as that of the embodiment shown in FIG. Further, the corrugated sheath 15 may be made of the same material as that shown in FIG. 1 except that the overall length is short. On the other hand, in the present embodiment, FIG.
As shown in (b), tendon 1
The grout material is filled up to the mouth of the anchor hole in which 0 is accommodated at a predetermined pressure. For this reason, in the fixing material supply hose 16 and the fixing material discharge hose 18 whose tip ends are housed inside the corrugated sheath 15, the intermediate parts of the hose passing through the grout are exposed to pressure. Therefore, a pressure resistant hose that does not block the pipe even with a predetermined external pressure is used. Further, the waterproof coking 17 also has a sufficient pressure resistant structure.

Here, a procedure for constructing the ground anchor 1 shown in FIG. 3B will be briefly described. In addition, since the overall flow of the construction is the same as that of FIGS. 2 (a) to (e),
A characteristic part of this embodiment will be described. As described above, in the present embodiment, the first-stage injection is performed on the entire anchor hole. At this time, the respective portions covered with the sheaths 12 and 13 and the corrugated sheath 15 are in an unbonded state by being reliably cut with the injected grout material. Cement milk as a fixing material is injected into the corrugated sheath 15 while curing the first fixing long portion as the distal anchor body until a predetermined strength is obtained and then tensioning and maintaining the tension state. And a second fixing long portion is formed. When the fixing material in the corrugated sheath 15 reaches a predetermined strength, a tension jack on the ground (not shown)
And remove the extra length of the anchor. Then, it is possible to sequentially excavate the ground portion 43 having the sufficiently long surplus free length portion 23 according to the construction stage. in this way,
According to the tendon 10 configured as shown in FIG.
After the construction of the ground anchor, when the ground portion 43 to be excavated from the ground is deep, the construction range of the corrugated sheath 15 as an insulating pipe can be suppressed to the minimum limit.
It is possible to significantly shorten the work process of the "second injection" performed in the corrugated sheath 15 described above.

FIG. 4 (a) shows a tendon 10 having a structure in which the sheath 13 contained in the tendon 10 shown in FIG. 1 (a) is omitted. As shown in the figure, this tendon 10 has a corrugated sheath 15
An intermediate water stopping caulk 19 is provided at a predetermined position therein. The position of the water blocking caulking 19 corresponds to the upper end position of the second fixing long portion 22 shown in FIG. 4B. That is, the second fixing long portion 22 is formed in the corrugated sheath 15 sandwiched between the water blocking caulking 17 located at the lower end of the corrugated sheath 15 and the intermediate water blocking caulking 19. As in FIG. 3A, the fixing material supply hose 16 and the fixing material discharge hose 18 are provided in the portion surrounded by the waterproof cokings 17 and 19 in the corrugated sheath 15.
Has been led. Tendon 10 having such a configuration
A procedure for constructing the ground anchor 1 (see FIG. 4B) using is briefly described. The overall flow of construction is the same as that of FIG. 2A to FIG. 2E as in the case of the type of FIG. 3, so a characteristic part of the present embodiment will be described. As described above, in the present embodiment, the first-stage injection is performed on the entire anchor hole. At this time, the grout material is filled around the tip tensile steel 11, the material sheath 12 and the corrugated sheath 15 in the anchor hole, and the sheath 12 and each part of the tensile steel material 11 covered with the corrugated sheath 15 correspond to the injected grout material. The edges are surely cut off to be in an unbonded state. The first fixing long portion 11 as the tip anchor body is cured until a predetermined strength is obtained, and then tensioned. Further, while maintaining the tension state of the tensile steel material 11, cement milk as a fixing material is injected into the corrugated sheath 15 by the fixing material supply hose 16 into the portion partitioned by the waterproof cokings 17 and 19, and the corrugated sheath 15 is supplied with the cement milk. The second fixing length portion 22 is formed. In order to surely form the second fixing length portion 22, it is preferable to confirm the concentration of the return liquid from the fixing material discharge hose 18. At this time, it is preferable that the upper space 25 above the intermediate water-stop caulking 19 of the corrugated sheath 15 be kept hollow or filled with fresh water.

When the fixing material in the corrugated sheath 15 has reached a predetermined strength, the tension jack (not shown) on the ground is removed and the surplus anchor length is cut. After that, the natural ground portion 43 as the surplus free length portion can be excavated according to the construction stage. In order to prevent the corrosion of the tensile steel material 11 in the upper space 25 of the corrugated sheath 15, the grout material may be injected into the upper space 25 without pressure before cutting the extra anchor length.

As the underground structure applicable to prevent rebound (lifting) at the time of excavating the surrounding ground by the ground anchor described above, existing pipelines, new large section tunnels, bottom retaining works for mountain retaining, etc. Various structures may be mentioned. Further, in the accompanying drawings, a ground anchor constructed vertically downward is illustrated, but it is also applicable to a ground anchor constructed diagonally at a predetermined angle such as construction on a slope. There is no end.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a structure of a ground anchor according to the present invention.

FIG. 2 is a construction sequence explanatory diagram showing a construction flow of the ground anchor shown in FIG.

FIG. 3 is an explanatory view showing another embodiment of the structure of the ground anchor.

FIG. 4 is an explanatory view showing another embodiment of the structure of the ground anchor.

FIG. 5 is a construction sequence explanatory view showing a construction flow of a conventional ground anchor.

[Explanation of symbols]

 1 Ground Anchor 10 Tendon 11 Tensile Steel Material 12,13 Sheath 15 Corrugated Sheath 17,19 Water-stop Caulking 20 First Fixation Length 21 Free Length 22 Second Fixation Length 23 Surplus Free Length

Front page continued (72) Inventor Yuko Kawarai 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation

Claims (3)

[Claims] 1. A tensile steel material inserted into an anchor hole drilled in the ground, and a fixing material injected into the anchor hole using the tensile steel material as a core material at a tip position of the tensile steel material. 1
A first anchoring long portion composed of the anchor body, and a barrier coating which covers a predetermined range in the longitudinal direction of the tensile steel material from the first anchoring length portion to the anchor hole mouth portion to form an anchor free length portion. An insulating pipe that is provided at a position separated from the first fixing length portion by the amount of the barrier coating and surrounds a predetermined range in the longitudinal direction of the tensile steel material, and is injected into the insulating pipe with the tensile steel material as a core material. A second anchoring length portion composed of a second anchor body formed of a anchoring material, and when a predetermined tension is introduced into the tensile steel material, the tensioner is located within the natural ground. A ground anchor characterized in that it is held between a long portion and the second fixing long portion. 2. The ground anchor according to claim 1, wherein a surplus free length portion is formed between the second fixing length portion and the anchor hole opening portion. 3. An anchor hole is drilled in the ground, and a barrier coating for covering at least a predetermined area in the longitudinal direction of the tensile steel is provided in the anchor hole and a longitudinal direction of the tensile steel adjacent to the barrier coating. Inserting a tendon attached with an insulating pipe surrounding a predetermined range, performing a first-stage injection into the anchor hole, and forming a first anchor body using the tip position of the tensile steel material as a core material to form a first anchor body.
A predetermined tension is applied to the tensile steel material in a state where the tip is fixed to the first fixing length portion, and the second tension injection is performed into the insulating pipe while maintaining this tension state, A second anchor body having the tensile steel material as a core material is formed in a predetermined range in the insulating pipe to form a second fixing length portion, and the tension introduced into the tensile steel material is applied to the first fixing length portion and the second fixing length portion.
The method for constructing a ground anchor is characterized in that it is held between the fixing long portions of the.