JP7193789B2 - Steel pipe for ground reinforcement - Google Patents

Description

The present invention relates to a rock reinforcement steel pipe that is driven into the ground as a supplementary method for tunnel construction by, for example, the NATM (New Austrian Tunneling Method) method, and in particular, a pre-received steel pipe that is sequentially spliced by screw joints to lengthen it. The present invention relates to a steel pipe for ground reinforcement suitable for such as.

In the AGF (All Ground Fasten) method, which is one of the tunnel auxiliary construction methods, about four steel pipes with a length of about 3 m are sequentially spliced and driven into the natural ground in front of the face to reinforce the natural ground. A male thread is formed at one end of each steel pipe, and a female thread is formed at the other end. The preceding steel pipe and the succeeding steel pipe are screwed together to join in a straight line. The steel pipe at the forefront and the steel pipe at the rear only need to be formed with a male thread or a female thread at only one end.

Usually, each steel pipe for ground reinforcement of this type 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 ground reinforcement in Patent Document 1 has a pipe main body and a connecting pipe portion which is separate therefrom. The pipe body has a required wall thickness for exhibiting the strength required for ground reinforcement. A female thread is formed on the inner peripheral surface of one end of the pipe body. A connection pipe portion is joined to the other end portion of the pipe body by friction welding. The connection pipe portion is configured by a pipe that is thicker and shorter than the pipe main body, and has a male thread formed on its outer peripheral surface.
In the steel pipe for ground reinforcement of Patent Document 2, a connecting pipe portion with a male thread is joined to one end of a pipe body, and a connecting pipe portion with a female thread is joined to the other end. Neither male nor female threads are formed on the pipe body.

JP 2016-053268 A Utility Model Registration No. 3182663 (Claim 2, Figure 2)

The standard specifications of a steel pipe for general AGF construction method are about 6 mm in wall thickness, about 114.3 mm in outer diameter, about 3 m in length, and about 50 kg in weight. For this reason, it is not easy to carry manually and workability is not good.
In the steel pipe for ground reinforcement of Patent Document 1, the wall thickness of the pipe body must be set to a size that can ensure the strength necessary for ground reinforcement and that a female screw can be formed on the inner peripheral surface of one end. be. Patent Document 1 states that the thickness of the pipe body is about 2.5 mm to 7 mm. is considered necessary to be about 4.5 mm or more. Therefore, the weight cannot be reduced so much.
In the steel pipe for ground reinforcement of Patent Document 2, it is not necessary to make the pipe body thick enough to form a screw thread, but as long as a general structural carbon steel pipe is used, the wall thickness to a certain extent necessary for ground reinforcement is required. It must be thick and cannot be expected to be light enough to improve workability.
SUMMARY OF THE INVENTION In view of such circumstances, it is an object of the present invention to improve workability by reducing the weight of steel pipes for ground reinforcement that are successively spliced by screw joints while ensuring the required strength.

In order to solve the above problems, the present invention provides a steel pipe for ground reinforcement that is spliced by screw joint,
a pipe body having no thread;
a connecting pipe portion having a threaded portion on its inner or outer peripheral surface, being shorter than the pipe main body, and inseparably joined to the end of the pipe main body;
wherein the steel materials of the pipe body and the connecting pipe part are different from each other, and the tensile strength of the pipe body is greater than the tensile strength of the connecting pipe part.
By using a steel material having a tensile strength higher than that of the connecting pipe portion for the pipe body, the pipe body can be reliably made thin while ensuring the required strength. Therefore, the weight of the steel pipe for ground reinforcement can be reduced, it can be easily carried by human power, and workability can be improved.

It is preferable that the connection pipe portion is made of steel having a tensile strength of 400 N/mm ² to 550 N/mm ² and a yield strength of 235 N/mm ² to 500 N/mm ² . As the connecting pipe portion, a general structural carbon steel pipe STK400 (JIS G3444) can be used.
It is preferable that the pipe main body is made of steel having a tensile strength of 650 N/mm ² to 1200 N/mm ² and a yield strength of 600 N/mm ² to 900 N/mm ² . As the pipe main body, a steel pipe having a higher tensile strength than the general structural carbon steel pipe STK400 is used. As a result, the wall thickness of the pipe body can be reliably reduced while ensuring the required strength, the weight of the rock reinforcement steel pipe can be reliably reduced, and workability can be sufficiently improved.

It is preferable that the tube body has a thickness of 2.5 mm to 4 mm.
Such a thickness can be realized by using a steel material having a higher tensile strength than that of the connecting pipe portion without the need to form a threaded portion on the pipe body.

ADVANTAGE OF THE INVENTION According to this invention, while ensuring the required strength of the steel pipe for ground reinforcement, it can reduce weight and improve workability.

FIG. 1 is a cross-sectional view of a tunnel under construction, showing how a long pre-receiving steel pipe made of a steel pipe for ground reinforcement according to one embodiment of the present invention is driven into the ground. FIG. 2(a) is an exploded front view of the steel pipe for ground reinforcement. FIG. 2(b) is a cross-sectional view of the steel pipe for ground reinforcement. FIG. 3 is a cross-sectional view showing an enlarged circular portion III of FIG. 2(b). FIG. 4 is a cross-sectional view showing an enlarged circular portion IV of FIG. 2(b).

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows a tunnel 1 under construction by the NATM construction method. A natural ground 2 is excavated and a tunnel 1 is constructed. At regular intervals in the axial direction of the tunnel 1, arch-shaped shorings 3 made of H-shaped section steel are installed. Shotcrete 4 is sprayed on the excavated surface 2 a between the shorings 3 . A secondary lining (not shown) is constructed on the inner peripheral side of the shoring 3 and the shotcrete 3 .

In the construction of the tunnel 1, for example, the AGF construction method is implemented as an auxiliary construction method for ground reinforcement. In the AGF construction method, a drill jumbo 5 is used to sequentially add a plurality of (for example, about four) steel pipes 10 for ground reinforcement, and drive them obliquely into the ground 2 in front of the face 1b (right in FIG. 1). , forming a long pre-receiving steel pipe 9 . The length of each mountain reinforcing steel pipe 10 is, for example, about 3 m. Adjacent ground reinforcement steel pipes 10 are connected in a straight line by screw joints. The overall length of the pre-receiving steel pipe 9 is, for example, about 12 m.
Although detailed illustration is omitted, an injection material such as silica resin or mortar is injected into the ground 2 around the pre-receiving steel pipe 9 .

As shown in FIGS. 2( a ) and 2 ( b ), the rock reinforcement steel pipe 10 has a pipe body 11 and connection pipe portions 20 and 30 .
The pipe body 11 is a straight pipe extending straight. The pipe length of the pipe main body 11 is approximately the same as the overall length (for example, about 3 m) of the rock reinforcement steel pipe 10, and the outer diameter of the pipe main body 11 is, for example, about 70 mm to 120 mm. No threaded portion, tapered portion, step, etc. are formed on the outer and inner peripheral surfaces of the pipe body 11, and the thickness of the pipe body 11 is constant from one end to the other end of the pipe body 11. Both end surfaces of the pipe main body 11 are flat, and for example, a spigot-type joining step is not formed.

One end (the right end in FIG. 2(b)) of the pipe main body 11 is abutted against the connecting pipe portion 20 and joined inseparably. The other end (the left end in FIG. 2(b)) of the pipe body 11 is abutted against the connecting pipe portion 30 and joined inseparably. Groove welding (detailed illustration is omitted) is applied as a means for joining the pipe main body 11 and the connecting pipe portions 20 and 30, but the method is not limited to this, and friction welding or the like may be applied. The pipe lengths of the connecting pipe portions 20 and 30 are sufficiently shorter than the pipe length of the pipe main body 11 .
In addition, in the steel pipe 10E at the forefront of the pre-receiving steel pipe 9, it is sufficient that the connection pipe portion 20 or 30 is provided only at the rear end portion (lower left end portion in FIG. 1). In the rearmost steel pipe 10B, it is sufficient that the connection pipe portion 30 or 20 is provided only at the tip portion (upper right end portion in FIG. 1).

As shown in FIG. 2B, the connection tube portion 20 has a threaded portion 21, a straight portion 22, and a tapered portion 23. As shown in FIG. A male thread 24 (screw portion) is formed on the outer peripheral surface of the thread forming portion 21 . A straight portion 22 is provided between the threaded portion 21 and the tapered portion 23 . The inner peripheral surfaces of the threaded portion 21 and the straight portion 22 are flush with each other. The inner diameters of the threaded 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 continues to the inner peripheral surface of the straight portion 22 without a step, and the diameter of the tapered portion 23 increases toward the pipe main body 11 . The inner diameter of the tapered portion 23 at the end 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 with each other, and are further flush with the outside wind surface of the pipe body 11 .

As shown in FIG. 2B, the connecting pipe portion 30 has a threaded portion 31, a straight portion 32, and a tapered portion 33. As shown in FIG. A female thread 34 (screw portion) is formed on the inner peripheral surface of the thread forming portion 31 . As indicated by the two-dot chain line in FIG. 2B, the female thread 34 of each rock reinforcement steel pipe 10 can be screwed with the male screw 24 of another adjacent rock reinforcement steel pipe 10 .

A straight portion 32 is provided between the threaded portion 31 and the tapered 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 continues to the inner peripheral surface of the straight portion 32 without a step, and the diameter of the tapered portion 33 increases toward the pipe main body 11 . The inner diameter of the tapered portion 33 at the end on the pipe body 11 side is equal to the inner diameter of the pipe 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 main body 11 . The outer peripheral surface of the connecting pipe portion 30 continues flush with the outer peripheral surface of the pipe main body 11 .

The steel materials of the pipe body 11 and the connecting pipe portions 20, 30 are different from each other. Moreover, the tensile strength of the pipe main body 11 is greater than the tensile strength of the connecting pipe portions 20 and 30 .
Preferably, the connecting pipe portions 20 and 30 are made of steel having a tensile strength of 400 N/mm ² to 550 N/mm ² and a yield strength of 235 N/mm ² to 500 N/mm ² . As steel pipes for the connecting pipe portions 20 and 30, general structural carbon steel pipe STK400 (JIS G3444) can be used.

On the other hand, as the pipe main body 11, a steel pipe 10 having a higher tensile strength than the general structural carbon steel pipe STK400 is used. Preferably, the pipe body 11 is made of steel having a tensile strength of 650 N/mm ² to 1200 N/mm ² and a yield strength of 600 N/mm ² to 900 N/mm ² . By adjusting the compounding ratio of C, Si, Mn, P, S and other components contained in the steel material, the above tensile strength and yield strength can be obtained.
As the pipe body 11, for example, a steel pipe disclosed in JP-A-2002-003941 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, 32 of the connecting pipe portions 20, 30, preferably t ₁₁ =2.5 mm to 4 mm, or more. Preferably, t ₁₁ =2.5 mm to 3.5 mm.
The thickness of the straight portions 22, 32 of the connecting pipe portions 20, 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 connection pipe parts 20 and 30 for the pipe body 11, the pipe body 11 can be reliably made thin while ensuring the required strength. can. Moreover, it is not necessary to form the threads 24 and 34 on the pipe main body 11, so that the pipe body 11 can be further thinned. Therefore, the weight of the pipe main body 11 and thus the steel pipe 10 for ground reinforcement can be reduced, and it is easy to carry by human power, and workability can be improved.

For example, in the case of standard specs (6 mm thick, 114.3 mm outer diameter, 3 m in length) of a steel pipe for ground reinforcement in a general AGF construction method, the weight is about 50 kg. The reinforcing steel pipe 10 weighs about 30 kg 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. Therefore, weight reduction of about 40% can be realized.

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

By providing the tapered portions 23, 33 between the inner peripheral surface of the pipe main body 11 of the rock reinforcement steel pipe 10 and the inner peripheral surfaces of the thread forming portions 21, 31 of the connecting pipe portions 20, 30, the pilot It is possible to prevent the bit 6 (FIG. 1) from being caught when inserting and removing it. In addition, the earth and sand that have entered the inside of the long pre-receiving steel pipe 9 can be discharged smoothly.

The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the invention.
For example, the steel pipe of the present invention is applicable not only as a pre-receiving steel pipe for the AGF construction 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, for example, to pre-received steel pipes for the AGF construction method.

1 Tunnel 2 Rock 2a Excavated surface 3 Shoring 4 Shotcrete 5 Drill jumbo 6 Pilot bit 9 Long steel pipe 10 Rock reinforcement steel pipe 11 Pipe main body 20 Male screw pipe (connecting pipe)
21 threaded portion 22 straight portion 23 tapered portion 24 male screw (screw portion)
30 Connection tube portion 31 Thread forming portion 32 Straight portion 33 Tapered portion 34 Female thread (thread portion)

Claims (2)

A steel pipe for ground reinforcement that is spliced by screw joints,
a pipe body having no thread;
a connecting pipe portion having a threaded portion on its inner or outer peripheral surface, being shorter than the pipe main body, and inseparably joined to the end of the pipe main body;
wherein the steel materials of the pipe body and the connecting pipe portion are different from each other, the thickness of the pipe body is smaller than the thickness of the straight portion of the connecting pipe portion closer to the pipe body than the threaded portion, and the pipe body the tensile strength is greater than the tensile strength of the connection pipe ,
The pipe body is made of steel having a tensile strength of 650 N/mm ² to 1200 N/mm ² and a yield strength of 600 N/mm ² to 900 N/mm ² ,
The ground reinforcement according to claim 1, wherein the connecting pipe portion is made of steel having a tensile strength of 400 N/mm ² to 550 N/mm ² and a yield strength of 235 N/mm ² to 500 N/mm ² . Steel pipe for The steel pipe for ground reinforcement according to claim 1, wherein the pipe body has a thickness of 2.5 mm to 4 mm.

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