JPH10131183A - Construction method for pulling-out underground cylindrical-body and split ring used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To pull out a steel bar and a stranded steel wire by applying tension by a method wherein split rings are connected and a ring body is assembled, the ring bodies are superposed and coupled vertically and a cylindrical body is built up, pressure is applied from an upper section while excavating the inside and the cylindrical body is pressed into a ground, and a solid-drawn-steel bar or the stranded steel wire is arranged beforehand to the ring body or the cylindrical body after the execution of works. SOLUTION: The split ring is called a segment piece 1 made of steel, and a frame body is constituted by welding joint plates at both end sections of a pair of curved main girders 3. A skin plate 9 is lined over the outside of the main girders 3, the joint plates, vertical ribs and intermediate main girders 8 and a stiffening plate 11 over the inside of the vertical ribs. A ring body is manufactured by connecting the segment pieces 1 made of steel in the circumferenetial direction, a cylindrical body is prepared by coupling the segment pieces 1 in the axial direction, and a cutting edge section 19 is installed at the lower edge of the ring body at a lowermost end. Steel bars 22 are mounted on the top plate 20 of the cutting edge section 19 and a plurality of other main girders 3 and other intermediate main girders 8. The steel bars 22 are drawn by pulling the steel bars 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of assembling a segment or a split ring having a structure similar thereto, and press-fitting the segment into the ground while expanding the segment to construct a cylindrical retaining wall in the ground. The present invention relates to a method of removing a tubular body by pulling it out from the ground after finishing.

[0002]

2. Description of the Related Art Conventionally, a circular ring body is assembled by connecting steel segments or split rings having a structure similar thereto in the circumferential direction of the ring, and the ring bodies are stacked and connected and added to form a cylindrical body. There is a technology for building structures such as tunnels and shafts underground by pressing a cylinder into the ground.

[0003] It has been proposed that this technique be further used for the construction of earth retaining walls at the time of seismic reinforcement of piers such as expressways, railway bridges, and overpasses. That is, for the seismic reinforcement of this pier, a cylindrical body assembled by connecting the split rings at a predetermined distance around the pier is pressed into the ground with a hydraulic jack or the like, and constructed as a retaining wall, and this pier and the retaining wall are constructed. After excavation of the bridge, the pier is reinforced with steel plate, concrete, carbon fiber sheet, or the like, using the space formed by the excavation as a working space.

[0004] After the construction for the reinforcing work is completed, it may be necessary to pull out the retaining wall, for example, for reuse. Although there is no example in the case of a split ring, pulling is commonly used for retaining walls such as steel sheet piles.

[0005]

However, pulling out the entire retaining wall by pulling the uppermost split ring requires a large pulling force on the entire retaining wall because the lower split ring is strongly captured in the ground. Will be added. Therefore, each split ring needs to have a strength that can withstand not only a large compressive force at the time of press-fitting but also a large tensile force. In addition, it is necessary to perform special reinforcement for pulling out. Particularly, when the ring members are connected by bolts, the tensile strength becomes a problem.

The present invention has been made in order to solve the above-mentioned problems, and an underground cylindrical body drawing method capable of performing drawing without requiring strength to withstand a large tensile force.
It is another object of the present invention to provide a split ring used in this method.

[0007]

Means for Solving the Problems In order to achieve the above objects, the following invention has been made. A first invention connects a split ring in a ring circumferential direction to assemble a ring body,
A ring-shaped blade installed along the lower edge of the lowermost ring by applying pressure from above the cylinder while excavating the inside of the cylinder and connecting the ring bodies vertically An underground cylindrical body drawing method in which the cylindrical body is pressed into the ground from the mouth portion, thereby constructing an earth retaining wall by the cylindrical body in the ground, and pulling out and removing the cylindrical body from the ground after completing the predetermined construction. A grounding method characterized in that a steel rod or a stranded steel wire for drawing is previously attached or arranged on a split ring, ring body, or cylindrical body, and the steel rod or the stranded steel wire is pulled out by applying tension. This is a method of pulling out the middle cylinder.

[0008] Since a steel rod or a stranded steel wire for drawing is previously attached or arranged on a split ring, a ring body or a cylindrical body, the tubular body is easily removed from the steel rod or the stranded steel after a predetermined construction is completed. Construction can be completed safely and quickly because the wire can be pulled out by applying tension.

According to a second aspect of the present invention, there is provided a split ring for use in the underground cylindrical body drawing method according to claim 1, wherein the steel is used to pull out the cylindrical body from a cutting edge portion installed along a lower end edge of the split ring. This is a split ring used in an underground cylindrical body drawing method, wherein a rod or a stranded steel wire is attached. Since a steel rod or a stranded steel wire for pulling out the cylindrical body is attached to the cutting edge of the lower edge of the split ring,
The work of pulling out the cylinder from the lowermost part is easy.

In a third aspect of the present invention, the blade opening portion is curved in a ring shape along a lower end edge of the split ring, and has a triangular space in a radial cross section. When,
The strength member, which is surrounded by an outer plate and an inner plate that extend downward from the inner and outer ends of the top plate and are joined at an acute angle and joined to each other, and to which the steel bar or the stranded steel wire is attached, is the top plate. This is a split ring used in the middle cylinder body drawing method. By attaching the above steel rod or twisted steel wire to the top plate at the cutting edge, pull out the cylinder from the bottom, apply only compressive stress to the middle and upper components of the cylinder, and pull out without applying tensile force It becomes possible.

According to a fourth aspect of the present invention, the steel rod is a PC steel rod, and the stranded steel wire is a stranded PC steel wire, or a hard steel wire or a stranded hard steel wire having a strength equal to or higher than these. The top plate is reinforced so as to function as an anchor plate, and the steel bar or the stranded steel wire is attached to the top plate through a coupler. It is a split ring. PC steel rod, twisted PC
Since the strength of a steel wire or a hard steel wire or a twisted hard steel wire having a strength equal to or higher than these is about 100 kg / mm ² , there is no breakage when the cylindrical body is pulled up.

According to a fifth aspect of the present invention, the steel rod or the stranded steel wire is mounted not only on the top plate surrounding the triangular space of the cutting edge but also at a predetermined interval above the top plate. This is a split ring used in an underground cylindrical body drawing method, which is also performed on a main girder. By attaching the steel bar or the stranded steel wire not only to the top plate at the cutting edge but also to the main girder present at a predetermined interval above the top plate, sufficient lifting strength is obtained. Can be secured. However, it should be attached only to the top plate at the cutting edge, and the main girder should be about a steel rod or twisted steel wire guide.
Pulling out from the bottom is preferable.

A sixth aspect of the present invention is a split ring used in an underground cylindrical body drawing method, wherein the coupler uses a PC nut embedded in a top plate. P
The use of the C nut facilitates attachment of a steel rod or a twisted steel wire.

A seventh invention is characterized in that the top plate is reinforced by increasing the thickness of the top plate, providing a reinforcing material on the top plate, or performing both of them. This is a split ring used in the underground cylindrical body drawing method. The top plate can be easily reinforced by increasing the thickness of the top plate and providing a reinforcing material on the top plate.

An eighth invention is the split ring according to any one of claims 2 to 7, wherein the cutting edge portion is made of a wear-resistant steel plate. Since the cutting edge is made of a wear-resistant steel plate, it is possible to realize an extension of the life of the cutting edge which meets the purpose of the present invention of providing a retaining wall that can be used repeatedly.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In this embodiment, the split ring is called a steel segment piece 1 as shown in FIG. That is, in the steel segment piece 1, a pair of parallel straight joint plates 5 are welded to both ends of the pair of parallel curved main girders 3 to form a frame.

Further, a plurality of parallel vertical ribs 7 are provided on the frame body in a direction perpendicular to the pair of main girders 3 and the middle main girder 8, and a plurality of parallel ribs 7 are provided on the pair of joint plates 5. A reinforcing plate called a middle main girder 8 is provided, and the main girder 3, the joint plate 5, the vertical rib 7, and the skin plate 9
Are stretched to form a steel segment piece 1. Note that, inside the vertical ribs 7, a backing plate 11 is partially stretched in the center of the steel segment piece 1, and a heavy equipment for excavation described later contacts the vertical ribs to set the excavation position by recoil or the like. To prevent distraction. In addition, the number of the middle main girder is usually 0 or 1 sheet, but a plurality of sheets can be used.

The steel segment piece 1 as such a split ring is connected in the circumferential direction of the ring to form a ring body 1.
Assembled as a three-piece steel segment (FIG. 1)
3). The ring body 13 is overlapped in the axial direction and connected to form the cylindrical body 1.
5 (see FIG. 6). Therefore, each digit 2,
5 has a bolt hole 17 (FIG. 14) for connection.

The ring member (steel segment) 13 at the lowermost end of the plurality of ring members to be stacked is provided with this ring member 1.
A ring-shaped blade opening 19 is installed along the lower edge of the third blade 3 (FIGS. 13 and 14). FIGS. 1 and 2 show a longitudinal sectional view of the blade opening 19. That is, the outer plate 21 and the inner plate 23 extend downward from the inner and outer peripheral ends of the top plate 20 disposed along the lower end edge of the steel segment piece 1 constituting the lowermost ring body. You.

The outer plate 21 and the inner plate 23 are curved in a ring shape, and their leading edges (lower ends in FIG. 1A) are butted at an acute angle and joined by welding or the like. The welded outer plate 21 and inner plate 23 form a space 25 having a triangular cross section inside. The blade opening is pressed into the ground and may come into contact with foreign matters such as boulders, so that the blade is easily worn or worn. Therefore, it is desirable that the blade opening is made of a wear-resistant steel plate. As the wear-resistant steel sheet, a commercially available wear-resistant steel sheet, for example, NK-EH3
00R, 400A, 500A (trade name) and the like can be used.

This space 25 is sealed in some way. For example, sealing is performed by sufficient welding or sufficient bolting through packing or the like.

The pipe 29 is made of each steel segment piece 1
Is connected to a large pipe (not shown) passing through the inside. This pipe is divided in the vertical direction for each steel segment piece 1, and the divided portions are connected using a joint. The top of the pipe is connected to the pump on the ground,
A ground injection agent for stopping water or reducing peripheral friction is pumped, and the injection agent is injected into the ground from a nozzle 33 having an injection agent discharge function by increasing the internal pressure while being sealed.

The oblique side of the triangle of the cross section of the space 25 is constituted by the inner plate 23, and the other long side is constituted by the outer plate 21. The inner surface at the end of the outer plate 21 is located on the inner surface at the end of the inner plate 23, and welding is performed. A notch 31 is formed on the inner surface of the distal end of the outer plate 21, and a portion of the notch 31 is not welded, and a nozzle 33 as an injection port is formed.

The top plate 20 which is a strength member surrounding the space 25 of the blade opening 19, and the main girder 3 and the middle main girder 8 which are located above the top plate 20 at a predetermined interval, are vertically aligned. A steel bar 22 for extraction is attached so as to penetrate in the direction. These installations are performed by the coupler 24
Done by The coupler 24 uses a PC nut 26 embedded in the top plates 8 and 20 (FIG. 2). In addition, it is not always necessary to fix and attach in this way.
It is also possible to fix it later.

These steel rods are attached at a plurality of positions at equal intervals in the circumferential direction of the cylindrical body 15. For example, 3
There are four places. However, it may be attached to five or more places. For example, when a pulling force of 100 tons is required, if four attachments are made, the pulling force per steel bar 22 becomes 25 tons. Therefore, the steel bar is a PC steel bar, and the stranded steel wire is preferably a stranded PC steel wire, or a hard steel wire or a stranded hard steel wire having a strength equal to or higher than these. JIS G350 as a material for hard steel wire
There is a hard steel wire or a hard steel wire specified in US Pat.

The space 25 is formed in a ring shape along the lower end edge of the ring body 13, and in the middle of the ring shape, the top plate 20, the outer plate 21 and the inner plate 23 are The reinforcement rib 35 (FIG. 13 (B)) is welded to maintain the strength of the blade opening 19 and at the same time
Reinforce 0.

Further, in this embodiment, a cylindrical body 1 is assembled by connecting steel segment pieces 1 which are split rings.
5 (see FIG. 6) is for constructing a retaining wall around the pier 37. The earth retaining wall secures a work space necessary for performing seismic reinforcement measures around the pier 37.

The construction procedure of the seismic reinforcement work will be described below with reference to FIGS. First, FIG.
Shows a plan view of the construction site. Near the existing pier 37, many steel segment pieces 1 as split rings are prepared. On a side opposite to the temporary placement of the steel segment pieces 1, a temporary storage space 38 of a press-fitting facility described later is prepared. On both sides of the bridge pier 37, a hydraulic clam shell 39 and a rough terrain clam shell 41 are arranged as heavy equipment for excavation. Further, a transport truck 43 for transporting the excavated earth and sand is prepared.

Next, a description will be given of the steps of the construction flow shown in FIG. 12 with reference to FIGS. First, as shown in FIG. 3, a reaction force is applied to drive an anchor bolt (not shown) into the pier 37 (S1 in FIG. 12). Using this anchor bolt, a slide column 45 is attached to the pier 37, and the jack system 4 slides along the slide column 45.
7 is assembled. The steel segment piece 1 is fixed to the ground 49 by the slide strut 45 and the jack system 47.
A press-fitting facility for press-fitting is installed (FIG. 12S2).

Next, as shown in FIG. 4, a cutting edge metal part 51 having a ring-shaped cutting edge 19 is attached to the lower end edge of the lowermost steel segment piece 1 as shown in FIGS. It is installed so as to correspond (S3 in FIG. 12). This installation is performed by first arranging the cutting edge hardware 51 horizontally at a predetermined position on the ground 49, and mounting the lowermost steel segment piece 1 thereon as shown in FIG. . Then, the lowermost steel segment is press-fitted by the jack system 47.

The next steel segment is connected and assembled on the steel segment (the ring body 13) after the press-fitting as shown in FIG. 6 (S4 in FIG. 12). The press-fitting and connection are repeated in this manner, and a cylindrical body 15 made of a steel segment is gradually built in the ground. In order to facilitate the press-fitting, the inside of the cylindrical body 15, that is, the inside of the steel segment is excavated by a heavy machine such as the hydraulic clam shell 39 as shown in FIG. 7 (S5 in FIG. 12).

At this time, in order to reduce the friction of the peripheral surface of the cylindrical body 15, a liquid such as a bentonite suspension is fed from the ground through a pipe 29, and the surrounding liquid is introduced from a nozzle 33 which is an injection port of the blade port 19. Into the ground to soften the ground. Pressing and assembling of the steel segments are repeated in this manner, so that the total length of the upper and lower portions of the cylindrical body 15 is sufficiently long,
At a predetermined depth, in this embodiment the blade opening 19 reaches the footing 53 which is the foundation of the pier 37 (FIG. 8).
(FIG. 12S6).

After this arrival, a protective work is performed in which an injectant for stopping water is fed through a pipe 29 and injected into the ground through a nozzle 33 which is an injection port of the blade opening 19 (FIGS. 9 and 12S).
7). By this injection, an improved layer 55 in which a part of the ground is improved is formed, and water can be prevented from flowing out from the lower end of the retaining wall made of the cylindrical body 15.

During the operation of press-fitting a steel segment by the jack system 47, the cutting edge 1
An internal pressure is applied to a space 25 (see FIG. 1) having a triangular cross section 9, that is, the inside of the inlet. This internal pressure can prevent earth and sand from clogging the injection port due to the press-fitting operation. Thereafter, underground water replacement for discharging muddy water inside the cylindrical body 15 is performed (S8 in FIG. 12). Then, final excavation is performed manually (S9 in FIG. 12), and a space 57 for work is created between the pier and the cylindrical body 15 that is the retaining wall.

Thereafter, a worker descends into the work space 57 to carry out reinforcement work of the pier 37. In this embodiment, reinforcement is performed by a carbon fiber sheet construction method in which a carbon fiber sheet (trade name: toe sheet) is pasted around the pier 37 instead of a steel plate (FIG. 12S10). That is, pier 3
7 is subjected to a base treatment, a primer is applied, and then an epoxy resin is applied, and a toe sheet is attached.
A resin is impregnated from above and the surface is finished after being sufficiently dried.

After the reinforcement is performed in this manner, the work space 57 becomes unnecessary, and therefore, as shown in FIG. 10, the work space 57 is backfilled with the residual soil 59 or the like (FIG. 12S1).
1). Thereafter, the cylindrical body 15 as a steel segment is pulled out and removed (S12 in FIG. 12).

This drawing method uses the jack system 4
7 by applying a pulling force to the steel bar 22. The jack system 47 is located at the center of the cylinder 15, and the steel bar 22 is located around the cylinder 15. Therefore, the pulling is performed in the vertical direction through the beam 28 passed over the peripheral portion of the cylindrical body 15. A method of alternately applying a tensile force to each of the plurality of steel rods 22 to be attached, or a method of simultaneously applying a tensile force is also possible. A method with lower frictional force is selected according to the underground situation.

When heavy machinery specialized in pulling is used instead of the jack system 47, there is no need to use the beam 28. When using a heavy machinery specialized in pulling, it is also possible to perform a pull-out operation while applying vibration. The vibration reduces the frictional force associated with pulling and requires only a relatively small pulling force.

Further, the pulling may be performed by a specialized heavy machine, and the jack system 47 may be configured to pull the uppermost split ring. In that case, the part or split ring sandwiched between these two pulls receives the pull as a compressive force by a specialized heavy machine, and this compressive force is offset by the pull force by the jack system 47, and the received force is reduced. .

A large force is locally applied to the portion to which the steel bar 22 is attached. However, this portion is the top plate 20, which is the strength member of the cutting edge portion 19 which requires the greatest strength at the time of press-fitting. In addition, there is little need to reinforce the installation.

Further, this attachment can be performed on a plurality of main girders 3 or middle main girders 8 (FIG. 2).
(A)), it is possible to prevent a large force from being applied to a specific member, and it is less necessary to perform special reinforcement, for example, increasing the plate thickness. However, if reinforcement such as thickening of the plate is performed, pulling can be performed with a sufficiently large pulling force, and the work is safe and quick.

The grout 61 is injected into the gap remaining after the removal to fill the gap.
2). This injection is performed from a nozzle 33 which is an injection port of the blade opening 19. However, it is also possible to leave this steel segment without removing it. Finally, the press-fitting equipment attached to the pier 37 is removed (FIG. 12).
S13).

(Other Embodiments) In the above embodiment, the steel bar 22 is attached by the coupler 24. However, in other embodiments, the steel bar 22 is mounted alone on the top plate 20 or the main girder 3. PC nut 30 (Fig. 2 (C))
May be performed. Although it can be performed for the middle main girder 8, it is not preferable because the amount of work increases.

Further, in the above embodiment, the steel bar 22 is attached to transmit the pulling force, but in other embodiments, a stranded steel wire (wire) may be attached.

In the above embodiment, the steel bar 22 is attached not only to the top plate 20 constituting the blade opening 19 but also to a plurality of other main girders 3 or middle main girders 8. In the embodiment, the attachment may be made only to the top plate 20 constituting the blade opening 19. This is possible if the top plate 20 is sufficiently reinforced. In addition, it is preferable to attach only to the top plate 20 because it can be pulled out from the lowermost portion.

In the above embodiment, the cylindrical body 15 assembled by the steel segment pieces 1 has been described as being constructed around the existing pier 37. However, in other embodiments, the surroundings of other structures are provided. It is good also as what is built in.

In the above embodiment, the cylindrical body 15 assembled by the steel segment pieces 1 has a complete circular cross section. However, in other embodiments, the cylindrical body 15 does not necessarily have to have a circular cross section. It may be shaped, roughly square or elliptical.

In the above embodiment, the internal pressure is applied to the injection port to prevent clogging with earth and sand during the press-in operation. However, in other embodiments, the injection agent is injected at a high pressure. Even if earth and sand are clogged in the injection port, it can be expected that the earth and sand will be naturally removed at the time of injection, and it may be unnecessary to apply internal pressure.

In the above embodiment, the cylindrical body 15 is press-fitted into the ground downward, but in other embodiments, the cylindrical body 15 is press-fitted into the ground in another direction, for example, in the horizontal direction. There may be.

[0050]

As described above, as described above, the first to seventh embodiments are described.
According to the invention, a steel rod or a stranded steel wire for drawing is previously attached or arranged on a split ring, a ring body, or a cylindrical body, and tension is applied to the steel rod or the stranded steel wire to perform drawing. In addition, the upper part or the split ring above the part where the attachment is made is trapped in the ground, and is subjected to a compressive force.

Then, the main girder,
Since the middle main girder and the vertical ribs have strength enough to withstand a large compressive force at the time of press-fitting, it is not necessary to provide special reinforcement for pull-out.

According to the second or third aspect of the present invention, furthermore, a steel bar or a stranded steel wire is attached to a strength member at the cutting edge, which requires the greatest strength at the time of press-fitting, for example, a top plate. There is little need to reinforce for the purpose.

Further, according to the fifth aspect, by attaching a steel rod or a stranded steel wire to the main girder or the middle main girder, a large force can be prevented from being applied to a specific member. Less special reinforcement will be required.

According to the fourth or seventh aspect of the present invention, since the top plate is further reinforced, the pull-out can be performed with a sufficiently large pulling force, and the work can be performed quickly and safely.

[Brief description of the drawings]

1A and 1B show a blade opening of a split ring according to an embodiment of the present invention, wherein FIG. 1A is a longitudinal sectional view of the blade opening, and FIG. 1B is an outer plate constituting the blade opening of FIG. (C) is a view of the cutting edge portion of (A) viewed from the cutting edge portion direction,

2A and 2B show a blade opening of a split ring according to one embodiment of the present invention, wherein FIG.
(B) is an enlarged view showing a main part of (A), and (C) is a view showing a modification of (B).

FIG. 3 is a view showing a pier seismic retrofitting work according to one embodiment of the present invention, and is a view showing a state where press-fitting equipment for press-fitting steel segments is installed.

FIG. 4 is a view showing a state in which the blade fitting is further installed in FIG. 3;

FIG. 5 is a view showing a state in which a steel segment is assembled on the blade opening metal in FIG. 4;

FIG. 6 is a view showing a state in which other steel segments are assembled one after another on the steel segment and press-fitting is performed.

FIG. 7 is a diagram showing a state where the inside of the steel segment is excavated in FIG. 6;

FIG. 8 is a diagram showing a state where the steel segment has reached a predetermined depth in FIG.

FIG. 9 is a view showing a state in which an injection for stopping water is injected in FIG.

FIG. 10A is a diagram showing a state in which the inside of the segment is being backfilled and the segment is being removed in FIG. 9;
(B) is an enlarged view showing a main part of (A).

FIG. 11 is a plan view showing a seismic retrofitting construction site.

FIG. 12 is a construction flowchart for explaining the construction procedure of FIGS. 3 to 10;

13A and 13B show a lowermost ring body (steel segment) on which a ring-shaped blade opening is installed, wherein FIG. 13A is a plan view and FIG. 13B is a side view.

14 (A) is a front view, FIG. 14 (B) is a side view, FIG. 14 (C) is a plan view, and FIG. 14 (D) is a bottom view. .

[Explanation of symbols]

 Reference Signs List 1 steel segment piece (split ring) 8 middle main girder 13 ring body (steel segment) 15 cylinder body 19 blade opening 20 top plate 21 outer plate 22 steel bar 23 inner plate 24 coupler 25 space 26, 30 PC nut 29 Pipe 33 nozzle

Claims (8)

[Claims] 1. A ring body is assembled by connecting split rings in a circumferential direction of a ring, and the ring bodies are vertically stacked and connected to form a cylindrical body. Pressure is applied from above the cylindrical body while excavating the inside of the cylindrical body. By doing so, the cylindrical body was pressed into the ground from the ring-shaped cutting edge installed along the lower edge of the lowermost ring body, thereby constructing a soil retaining wall with the cylindrical body in the ground, and completed the predetermined construction This is an underground cylindrical body drawing method in which the cylindrical body is later pulled out from the ground to remove it.A steel rod or twisted steel wire for drawing is attached or arranged in advance on a split ring, ring body, or cylindrical body, and An underground cylindrical body drawing method characterized in that a steel rod or a stranded steel wire is drawn by applying tension. 2. A split ring used in the underground cylindrical body drawing method according to claim 1, wherein the steel rod or the stranded steel is used to pull out the cylindrical body from a cutting edge installed along a lower edge of the split ring. A split ring used in an underground cylindrical body drawing method, wherein a wire is attached. 3. The blade opening portion is curved in a ring shape along a lower edge of the split ring, and has a space having a triangular cross section in a radial direction, and the space includes an upper top plate and a top plate. 3. A strength member which is enclosed by an outer plate and an inner plate which extend downward from the inner and outer ends of the base plate and are joined at an acute angle and are joined, and to which the steel rod or the stranded steel wire is attached, is the top plate. A split ring used in the underground cylindrical body drawing method described in the above. 4. The steel rod is a PC steel rod, the stranded steel wire is a stranded PC steel wire, or a hard steel wire or a stranded hard steel wire having a strength equal to or greater than these, and the top plate is an anchor. 4. The underground cylinder body drawing method according to claim 3, wherein the steel bar or the stranded steel wire is attached to the top plate through a coupler. Split ring. 5. The mounting of the steel rod or the stranded steel wire is performed not only on the top plate surrounding the triangular space of the cutting edge but also on the main girder existing at a predetermined interval above the top plate. The split ring used in the underground tubular body drawing method according to claim 4, wherein the split ring is also used. 6. The split ring used in the underground cylindrical body drawing method according to claim 4, wherein the coupler uses a PC nut embedded in a top plate. 7. The top plate is reinforced by increasing the thickness of the top plate, providing a reinforcing material on the top plate, or performing both of them. A split ring used in the underground cylindrical body drawing method described in the above. 8. The split ring according to claim 2, wherein the cutting edge is made of a wear-resistant steel plate.