JP2020066908A - Steel pipe for ground reinforcement - Google Patents

Abstract

To improve workability by reducing the weight of steel pipes for ground reinforcement that are successively added by screw joining while ensuring the required strength.SOLUTION: Short connecting pipe portions 20 and 30 having screw portions 24 and 34 are inseparably joined to end portions of a pipe body 11 having no screw portion in a ground reinforcing steel pipe 10. Steel materials of the pipe body 11 and the connecting pipe portions 20 and 30 are different from each other, and tensile strength of the pipe body 11 is greater than tensile strength of the connecting pipe portions 20 and 30. Preferably, the pipe body 11 has tensile strength of 650 N/mmto 1200 N/mm, yield strength of 600 N/mmto 900 N/mm, and thickness of 2.5 mm to 4 mm.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a ground reinforcement steel pipe that is driven into the ground as an auxiliary construction method when constructing a tunnel by, for example, the NATM (New Austrian Tunneling Method) construction method, and in particular, a front-end steel pipe that is sequentially added by screw joining to increase the length. The present invention relates to a steel pipe for ground reinforcement suitable for such purposes.

  In the AGF (All Ground Fasten) method, which is one of the tunnel auxiliary methods, about 4 steel pipes with a length of about 3 m are sequentially added while driving into the ground in front of the face to reinforce the ground first. A male screw is formed on one end of each steel pipe, and a female screw is formed on the other end. The steel pipe that was driven in before and the steel pipe that follows is screwed together to add in a straight line. In the most advanced steel pipe and the last steel pipe, a male screw or a female screw may be formed only on one end.

  Usually, each type of steel pipe for ground reinforcement is an integral single pipe, and is entirely made of a single steel material. Specifically, a general structural carbon steel pipe STK400 (JIS G3444) is generally used.

The steel pipe for rock reinforcement in Patent Document 1 has a pipe main body and a connection pipe portion that is separate from the pipe main body. The pipe body has a required wall thickness for expressing the strength required for ground reinforcement. A female screw is formed on the inner peripheral surface of one end of the tube body. The connecting pipe portion is joined to the other end portion of the pipe body by friction welding. The connecting pipe portion is composed of a pipe that is thicker and shorter than the pipe body, and has a male screw formed on its outer peripheral surface.
In the steel pipe for ground reinforcement of Patent Document 2, a connecting pipe portion with a male screw is joined to one end of the pipe body, and a connecting pipe portion with a female screw is joined to the other end. The pipe body has neither male nor female threads.

JP, 2016-053268, A Utility model registration No. 3182663 (claim 2, FIG. 2)

The standard specifications of a steel pipe for a general AGF method are a wall thickness of about 6 mm, an outer diameter of about 114.3 mm, a length of about 3 m, and a weight of about 50 kg. For this reason, it is not easy to carry by hand and workability is not good.
In the steel pipe for ground reinforcement of Patent Document 1, it is necessary to make the wall thickness of the pipe body large enough to secure the strength required for ground reinforcement and to form a female screw on the inner peripheral surface of one end. is there. Patent Document 1 describes that the wall thickness of the pipe main body is set to about 2.5 mm to 7 mm, but considering the screw thread height for obtaining the required screw joint strength, the wall thickness of the pipe main body is actually Is required to be about 4.5 mm or more. Therefore, the weight cannot be reduced so much.
In the steel pipe for rock reinforcement of Patent Document 2, it is not necessary to make the pipe body thick enough to form threads, but as long as the carbon steel pipe for general structure is used, a certain amount of meat necessary for rock reinforcement is required. Since it must have a sufficient thickness, it cannot be expected to reduce the weight until workability can be sufficiently improved.
In view of such circumstances, it is an object of the present invention to improve the workability by reducing the weight of steel pipes for ground reinforcement that are sequentially added by screw joining while ensuring the required strength.

In order to solve the above problems, the present invention is a steel pipe for rock reinforcement, which is added by screw joining,
A tube body that does not have a screw part,
A connecting pipe portion having a threaded portion on the inner peripheral surface or the outer peripheral surface, shorter than the pipe body, and inseparably joined to the end portion of the pipe body,
The steel materials of the pipe body and the connecting pipe portion are different from each other, and the tensile strength of the pipe body is larger than the tensile strength of the connecting pipe portion.
By using a steel material having a higher tensile strength than the connecting pipe portion as the pipe body, the pipe body can be surely made thin while ensuring the required strength. Therefore, it is possible to reduce the weight of the steel pipe for ground reinforcement, make it easy to carry by human power, and improve workability.

It said connection tube portion, a tensile strength of ^{400N / mm 2 ~550N / mm 2} , which is preferably constituted by a steel yield strength ^{235N / mm 2 ~500N / mm 2} . As the connecting pipe portion, a general structural carbon steel pipe STK400 (JIS G3444) can be used.
The tube body, a tensile strength of ^{650N / mm 2 ~1200N / mm 2} , which is preferably constituted by a steel yield strength ^{600N / mm 2 ~900N / mm 2} . As the pipe body, a steel pipe having a higher tensile strength than that of the general structural carbon steel pipe STK400 is used. As a result, it is possible to reliably reduce the thickness of the pipe body while ensuring the required strength, reliably reduce the weight of the steel pipe for ground reinforcement, and improve workability sufficiently.

It is preferable that the tube body has a thickness of 2.5 mm to 4 mm.
It is not necessary to form a threaded portion on the pipe body, and such a thickness can be realized by using a steel material having a higher tensile strength than the connecting pipe portion.

  According to the present invention, the required strength of the steel pipe for ground reinforcement can be secured, the weight can be reduced, and the workability can be improved.

FIG. 1 is a cross-sectional view of a tunnel under construction showing a state in which a long front receiving steel pipe made of a steel pipe for rock reinforcement according to an embodiment of the present invention is driven into the ground. FIG. 2A is an exploded front view of the steel pipe for ground reinforcement. FIG.2 (b) is sectional drawing of the said steel pipe for rock reinforcement. FIG. 3 is an enlarged cross-sectional view of the circle III of FIG. 2B. FIG. 4 is an enlarged cross-sectional view of the circle IV of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the tunnel 1 under construction by the NATM method. The ground 2 is excavated and the tunnel 1 is constructed. Arch-shaped supports 3 made of steel having an H-shaped cross section are installed at regular intervals in the axial direction of the tunnel 1. Sprayed concrete 4 is sprayed on the excavated surface 2a between the support works 3. A secondary lining (not shown) is constructed on the inner peripheral side of the support 3 and the shotcrete 3.

In the construction of the tunnel 1, for example, the AGF method is used as an auxiliary method for reinforcing the ground. In the AGF method, a drill jumbo 5 is used to sequentially add a plurality of (for example, about 4) steel pipes 10 for ground reinforcement while driving diagonally into the ground 2 in front of the face 1b (right in FIG. 1). , A long receiving steel pipe 9 is formed. The length of the local mountain reinforcing steel pipe 10 is, for example, about 3 m. Adjacent ground reinforcing steel pipes 10 are connected in a straight line by screw connection. The total length of the front receiving steel pipe 9 is, for example, about 12 m.
Although not shown in detail, an injection material such as silica resin or mortar is injected into the ground 2 around the receiving steel pipe 9.

As shown in FIGS. 2A and 2B, the ground reinforcing steel pipe 10 has a pipe body 11 and connecting pipe portions 20 and 30.
The pipe body 11 is a straight pipe that extends straight. The pipe length of the pipe body 11 is approximately the same as the total length (for example, about 3 m) of the steel pipe 10 for reinforcing ground, and the outer diameter of the pipe body 11 is, for example, about 70 mm to 120 mm. No threaded portion, tapered portion, step or the like is formed on the outer peripheral surface and the inner peripheral surface of the tube body 11, and the thickness of the tube body 11 is constant from one end to the other end of the tube body 11. Both end surfaces of the tube body 11 are flat, and, for example, an inlay-type step for joining is not formed.

A connecting pipe portion 20 is abutted against one end portion (right end portion in FIG. 2B) of the pipe body 11 and is inseparably joined. A connecting pipe portion 30 is abutted and inseparably joined to the other end portion (the left end portion in FIG. 2B) of the pipe body 11. Although groove welding (detailed illustration is omitted) is applied as a joining means between the tube body 11 and the connecting tube portions 20 and 30, the invention is not limited to this and friction welding or the like may be applied. The pipe length of the connecting pipe portions 20 and 30 is sufficiently shorter than the pipe length of the pipe body 11.
In the frontmost steel pipe 10E of the front receiving steel pipe 9, the connecting pipe portion 20 or 30 may be provided only at the rear end portion (lower left end portion in FIG. 1). In the tailmost steel pipe 10B, the connecting pipe portion 30 or 20 may be provided only at the tip portion (upper right end portion in FIG. 1).

  As shown in FIG. 2B, the connection pipe portion 20 has a screw forming portion 21, a straight portion 22, and a taper portion 23. A male screw 24 (screw portion) is formed on the outer peripheral surface of the screw forming portion 21. A straight portion 22 is provided between the screw forming portion 21 and the taper portion 23. The inner peripheral surfaces of the screw forming portion 21 and the straight portion 22 are flush and continuous. The inner diameters of the screw forming portion 21 and the straight portion 22 are smaller than the inner diameter of the pipe body 11.

As shown in FIG. 3, the inner peripheral surface of the tapered portion 23 is continuous with the inner peripheral surface of the straight portion 22 without any step, and is expanded toward the tube body 11. The inner diameter of the end of the tapered portion 23 on the pipe body 11 side is equal to the inner diameter of the pipe body 11.
The outer diameters of the straight portion 22 and the tapered portion 23 are equal to the outer diameter of the pipe body 11. The outer peripheral surfaces of the straight portion 22 and the tapered portion 23 are flush and continuous with each other, and further flush with the outside air surface of the pipe body 11.

  As shown in FIG. 2B, the connecting pipe portion 30 has a screw forming portion 31, a straight portion 32, and a taper portion 33. A female screw 34 (screw portion) is formed on the inner peripheral surface of the screw forming portion 31. As shown by the chain double-dashed line in FIG. 2B, the female screw 34 of each local mountain reinforcing steel pipe 10 can be screwed with the male screw 24 of another adjacent natural mountain reinforcing steel pipe 10.

A straight portion 32 is provided between the screw forming portion 31 and the taper portion 33. As shown in FIG. 4, the inner diameter of the straight portion 32 is smaller than the inner diameter of the pipe body 11. The inner peripheral surface of the tapered portion 33 is continuous with the inner peripheral surface of the straight portion 32 without any step, and the diameter of the inner peripheral surface of the tapered portion 33 increases toward the tube body 11. The inner diameter of the end of the tapered portion 33 on the tube body 11 side is equal to the inner diameter of the tube body 11.
As shown in FIG. 2, the outer diameter of the connecting pipe portion 30 is equal to the outer diameter of the pipe body 11. The outer peripheral surface of the connecting pipe portion 30 is flush with the outer peripheral surface of the pipe body 11.

The steel materials of the pipe body 11 and the connecting pipe portions 20 and 30 are different from each other. Moreover, the tensile strength of the pipe body 11 is larger than the tensile strength of the connecting pipe portions 20 and 30.
Preferably, the connecting tube portion 20 and 30, a tensile strength of ^{400N / mm 2 ~550N / mm 2} , is constituted by the steel material strength ^{235N / mm 2 ~500N / mm 2} . As the steel pipe for the connecting pipe portions 20 and 30, a general structural carbon steel pipe STK400 (JIS G3444) can be used.

On the other hand, as the pipe body 11, the steel pipe 10 having a higher tensile strength than the general structural carbon steel pipe STK400 is used. Preferably, the tube main body 11, a tensile strength of ^{650N / mm 2 ~1200N / mm 2} , is constituted by the steel material strength ^{600N / mm 2 ~900N / mm 2} . The tensile strength and proof stress can be obtained by adjusting the compounding ratio of C, Si, Mn, P, S and other components contained in the steel material.
As the pipe body 11, for example, the steel pipe disclosed in JP 2002-003941 A may be used.

The thickness t ₁₁ (difference between the outer radius and the inner radius) of the pipe body 11 is smaller than the thickness of the straight portions 22 and 32 of the connecting pipe portions 20 and 30, and preferably t ₁₁ = 2.5 mm to 4 mm or more. Preferably, t ₁₁ = 2.5 mm to 3.5 mm or so.
The thickness of the straight portions 22 and 32 of the connecting pipe portions 20 and 30 is preferably about 5 mm to 7 mm, more preferably about 6 mm.

  According to the ground reinforcement steel pipe 10, by using a steel material having a higher tensile strength and a higher yield strength than the connecting pipe portions 20 and 30 as the pipe body 11, the pipe body 11 can be reliably made thin while ensuring the required strength. it can. Moreover, it is not necessary to form the screws 24 and 34 on the tube body 11, and the wall thickness can be further reduced. Therefore, the pipe body 11 and thus the steel pipe 10 for strengthening the natural ground can be reduced in weight, can be easily carried by human power, and workability can be improved.

For example, in the case of the standard specifications of a steel pipe for rock reinforcement in a general AGF method (wall thickness 6 mm, outer diameter 114.3 mm, length 3 m), the weight is about 50 kg, while the rock of the present invention embodiment In the reinforcing steel pipe 10, when the pipe body 11 has a tensile strength of 800 N / mm ² , a thickness of 3.2 mm, an outer diameter of 114.3 mm, and a length of 3 m, the weight is about 30 kg. Therefore, weight reduction of about 40% can be realized.

  Since the tube body 11 is not provided with a threaded portion, a tapered portion, a step, or any other shape-changing portion, it is not necessary to perform processing such as cutting. Therefore, the strength of the pipe main body 11 can be set without considering the workability.

  By providing the taper portions 23 and 33 between the inner peripheral surface of the pipe body 11 of the ground reinforcing steel pipe 10 and the inner peripheral surfaces of the screw forming portions 21 and 31 of the connecting pipe portions 20 and 30, the pilot It is possible to prevent the bit 6 (FIG. 1) from being caught when it is inserted or removed. Further, the earth and sand that have entered the inside of the long front receiving steel pipe 9 can be smoothly discharged.

The present invention is not limited to the embodiment described above, and various modifications can be made without departing from the spirit of the present invention.
For example, the steel pipe of the present invention can be applied not only to the receiving steel pipe for the AGF method, but also as a steel pipe for mirror reinforcement work and a steel pipe for underground piles.

  INDUSTRIAL APPLICABILITY The present invention can be applied to, for example, a receiving steel pipe for the AGF method.

1 Tunnel 2 Ground 2a Excavation surface 3 Supporting work 4 Sprayed concrete 5 Drill jumbo 6 Pilot bit 9 Long tip steel pipe 10 Steel pipe for ground reinforcement 11 Pipe body 20 Male screw pipe part (connection pipe part)
21 screw forming part 22 straight part 23 taper part 24 male screw (screw part)
30 Connection Pipe Part 31 Screw Forming Part 32 Straight Part 33 Tapered Part 34 Female Screw (Screw Part)

Claims (3)

A steel pipe for rock reinforcement that is added by screw joining,
A tube body that does not have a screw part,
A connecting pipe portion having a threaded portion on the inner peripheral surface or the outer peripheral surface, shorter than the pipe body, and inseparably joined to the end portion of the pipe body,
A steel pipe for ground reinforcement, characterized in that the pipe main body and the connecting pipe portion are made of different steel materials, and the tensile strength of the pipe main body is larger than the tensile strength of the connecting pipe portion. The tube body, a tensile strength of ^{650N / mm 2 ~1200N / mm 2} , is constituted by the steel material strength ^{600N / mm 2 ~900N / mm 2} ,
Said connection tube portion, a tensile strength of ^{400N / mm 2 ~550N / mm 2} , the natural ground reinforcing according to claim 1, characterized in that it is constituted by a steel yield strength 235N ^/ mm ² ~500N ^/ mm 2 Steel pipe.   The steel pipe for rock reinforcement according to claim 1 or 2, wherein the thickness of the pipe body is 2.5 mm to 4 mm.

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