JP2019056285A - Ground-embedded steel pipe - Google Patents

Abstract

To provide a ground-embedded steel pipe capable of guaranteeing collapse strength and breaking strength and suppressing a possibility of loosening of screwing between male and female screws.SOLUTION: An ground-embedded steel pipe 10 is connected in series with each other and embedded in the underground, and comprises an enlarged diameter portion 20 formed in a predetermined range from a front end surface 12, a female screw 21 formed on an inner surface of the enlarged diameter portion 20, an inner surface taper 22 which is formed between the inner surface of the enlarged diameter portion 20 and an inner surface of a main body portion 11 and whose inner diameter decreases with distance from the front end surface 12, an outer diameter small portion 33 formed on an outer surface of a predetermined range from a rear end surface 13, an outer surface taper 32 formed on the outer diameter small portion 33, and a male screw 31 connected to the outer diameter small portion 33. The male screw 31 of one ground-embedded steel pipe 10 (ground-embedded steel pipe 2) and the female screw 21 of the other ground-embedded steel pipe 10 (ground-embedded steel pipe 3) are screwed together, and the former outer surface taper 32 and the latter inner surface taper 22 are pressed against each other.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a natural ground buried steel pipe, and more particularly, to a natural ground buried steel pipe buried in a natural ground or ground.

Conventionally, as steel pipes buried in natural ground and ground (hereinafter collectively referred to as “natural ground”), for example, steel pipes for injecting natural ground reinforcing material into natural ground, and for discharging water from natural ground Steel pipes are known.
For example, when constructing a tunnel in a vulnerable ground, it is used in construction methods such as the “AGF construction method” in which excavation is started with the front face of the face stabilized. Such a construction method is to place a plurality of steel pipes (hereinafter referred to as “connected steel pipes”) so as to be arranged in an approximately arch shape obliquely in front of the face, and the connected steel pipes are connected to each other in series. (Hereinafter, each of the steel pipes is referred to as a “natural mountain buried steel pipe”).
That is, the first (head) ground buried steel pipe is provided with a drilling device at the front end thereof and is drawn into a drilling hole formed along with the drilling following the drilling. And when it is pulled in by a predetermined distance, the front end of the second (intermediate) ground buried steel pipe is connected to the rear end of the first ground buried steel pipe, and both are pulled into the borehole following the excavation. It is. Similarly, the third (intermediate) underground steel pipe and the fourth (intermediate or tail) underground steel pipe are connected and drawn into the excavation hole as a connected steel pipe.

When the excavation (withdrawn) is completed, the connecting steel pipe is supplied with natural reinforcing agent (same as stabilizer or fixing agent) from the rear end, and the natural reinforcing agent is supplied to the side surface of the natural underground pipe. It is made "for reinforcing agent injection" by injecting into the natural ground from the through-hole provided in. Alternatively, instead of injecting the reinforcing agent, the groundwater is taken into the inside from the through-hole without supplying the ground reinforcing agent or the like, thereby “for draining”.
The length of the connecting steel pipe, the length and the number of the underground buried steel pipes to be connected are not limited, and the posture of the connecting steel pipe may be horizontal, inclined with respect to the horizontal or vertical. Furthermore, without providing a through hole, the inside may be a container, or the inside may be a flow path (the excavator is removed).

The underground steel pipe is a crushing strength that can withstand the pressure of the natural ground, a strength that does not separate each other when pulled, that is, a breaking strength that does not break the connecting part, and ease of handling and pulling during construction. There is a demand for weight reduction.
When the natural steel pipes are connected to each other by a male screw formed at one end of the pipe and a female screw formed at the other pipe end, the male screw and the female screw are connected to the natural steel pipe. Therefore, the thickness of the male screw portion (distance from the bottom of the screw valley to the inner surface) and the thickness of the female screw portion (distance from the bottom of the screw valley to the outer surface) are reduced.
Therefore, since the breaking strength is reduced, and when the thickness is increased to ensure the breaking strength, it becomes heavier. Therefore, an invention for solving these problems has been disclosed (for example, see Patent Document 1). ).

JP 2012-149458 A (page 5-7, FIG. 2)

In the invention disclosed in Patent Document 1 (corresponding to a natural ground buried steel pipe), a male screw is formed on the outer surface of one pipe end, the diameter of the other pipe end is expanded, and the inner surface of the expanded diameter portion Further, a female screw that is screwed onto the male screw is formed.
For this reason, the thickness of the male thread portion and the female screw portion are set to predetermined thicknesses to improve the breaking strength and to improve the breaking strength, thereby reducing the thickness of the buried steel pipe ( (Weight reduction). In the embodiment described in Patent Document 1, the ground buried steel pipe is a relatively small diameter steel pipe having an outer diameter of 76.3 mm and a wall thickness of 4.2 mm, and is located outside the expanded portion. The diameter is 81.7 mm and the wall thickness is 3.9 mm.

However, when advancing while excavating and rotating the excavator, repeated hits and rotations are repeatedly applied to the ground, and the excavator is repeatedly raised and lowered. It is repeatedly transmitted to the threaded part with the female screw. Then, in the natural ground buried steel pipe disclosed in Patent Document 1, the outer diameter becomes larger and the wall thickness becomes smaller (thinner) and the cross-sectional rigidity is lowered compared with the portion where the diameter-expanded portion is not expanded. For this reason, there is a problem that the screwing between the male screw and the female screw may be loosened.
In particular, when applied to a steel pipe having a larger outer diameter (for example, 89.1 mm or 114.3 mm), or to a thinner steel pipe (for example, 3.9 mm), the expanded diameter portion Since the outer diameter is further increased and the wall thickness is further reduced, this problem becomes remarkable.

  The present invention solves such a problem, and provides a ground buried steel pipe capable of ensuring the crushing strength and breaking strength and suppressing the risk of loosening of the male screw and the female screw. is there.

(1) The natural ground buried steel pipe according to the present invention is a natural ground buried steel pipe that is connected in series to be buried in the natural ground, and has an enlarged diameter portion formed in a predetermined range from one end face; A female screw formed on the inner surface of the enlarged diameter portion, a large inner diameter portion formed between one end surface and the female screw, and connected to the inner surface of the enlarged diameter portion, and away from the one end surface. An internal taper having an inner diameter that decreases, and a male screw formed in a predetermined range from the other end surface;
The male thread of one ground buried steel pipe and the female thread of the other ground buried steel pipe are screwed together, and the male thread of one ground buried steel pipe and the inner surface taper of the other ground buried steel pipe, Are characterized by pressing together.
(2) Moreover, it is a natural ground buried steel pipe which is connected in series with each other and buried in the natural ground, and is formed on the inner surface of the enlarged diameter portion formed in a predetermined range from one end face. An inner diameter large portion formed between one end face and the female screw, an inner taper formed to be connected to the inner face of the enlarged diameter portion, and the inner diameter decreases as the distance from the one end face increases. The outer surface small diameter portion formed on the outer surface of the predetermined range from the other end surface, and a male screw formed connected to the outer surface small diameter portion,
The male thread of one ground buried steel pipe and the female thread of the other ground buried steel pipe are screwed together, and the outer surface small diameter portion of one ground buried steel pipe and the inner surface of the other ground buried steel pipe The taper is pressed against each other.
(3) Further, the outer surface small diameter portion has an outer surface taper in which the outer diameter decreases toward the other end surface closer to the other end surface, and the ratio of the decrease in the inner diameter of the inner surface taper is the outer surface taper. The diameter is larger than the rate of reduction, and the inner taper of one of the ground buried steel pipes and the corner of the outer taper of the other ground buried steel pipe and the other end face are pressed against each other.
(4) Further, the male screw and the female screw are a trapezoidal screw or a deformed trapezoidal screw having a screw thread portion and a screw bottom portion formed in an arcuate cross section.

Since the ground buried steel pipe which concerns on this invention is the said structure, there exist the following effects.
(A) The thickness of the portion where the female screw is formed (distance from the bottom of the screw valley and the enlarged portion) and the thickness of the portion where the male screw is formed (the distance from the bottom of the screw valley to the inner surface) Since it increases compared with the case where the female screw and the male screw are formed without forming the portion, the breaking strength when the female screw and the male screw screwed to each other are separated in the tube axis direction is improved.
(B) Further, since the breaking strength is improved, it is possible to reduce the wall thickness to a value that can ensure the breaking strength and the crushing strength to predetermined values, respectively, so that weight reduction is promoted. The
(C) Also, the male screw and the inner taper are pressed against each other, or the outer surface small diameter portion and the inner taper are pressed against each other, so that the screw surface (slope) of the male screw and the screw surface (slope) of the female screw are in contact with each other. As the surface pressure increases, a frictional force acts between the male screw and the inner taper, or a frictional force acts between the outer surface small diameter portion and the inner taper. It becomes difficult to loosen.
(D) Moreover, since it has an inner diameter large diameter part, insertion of a male screw or an internal diameter small diameter part becomes easy, and workability | operativity improves.
(E) Furthermore, since the male screw and the female screw are trapezoidal screws or deformed trapezoidal screws (same as so-called “r screw” and “rope screw”), they are easily screwed and have high breaking strength.

It is sectional drawing of the side view which shows the use condition explaining the natural ground buried steel pipe which concerns on Embodiment 1 of this invention. It is a side view explaining the natural ground buried steel pipe which concerns on Embodiment 1 of this invention. It is a side view which shows a part in the use condition of the natural ground buried steel pipe shown in FIG. It is a side view explaining the natural ground buried steel pipe which concerns on Embodiment 2 of this invention. It is a side view which shows a part in the use condition of the natural ground buried steel pipe shown in FIG. It is a side view which shows a part in the use condition explaining the natural ground buried steel pipe which concerns on Embodiment 3 of this invention. The modification of the screw | thread of the natural ground buried steel pipe shown in FIG. 6 is demonstrated, Comprising: (a) is a side view which shows a part, (b) is a side view which expands a part.

  Hereinafter, modes for carrying out the invention (hereinafter referred to as “Embodiments 1 and 2”) will be described with reference to the drawings. Each drawing is schematically drawn, and the present invention is not limited to the illustrated form (the shape and number of parts). Moreover, in order not to make a drawing complicated, description of a one part member or one part code | symbol may be abbreviate | omitted.

[Embodiment 1]
FIGS. 1 to 3 illustrate a natural ground buried steel pipe according to Embodiment 1 of the present invention, taking the “steel pipe for injecting reinforcing agent” as an example in the AGF method, and FIG. FIG. 2 is a side view, FIG. 2 is a side view, and FIG. 3 is a side view showing a part in use. 2 and 3 are cross sections above the center line indicated by the alternate long and short dash line.

(Connecting pipe)
In FIG. 1, a connecting steel pipe 9 used in a known AGF method is a steel pipe for injecting a reinforcing agent, and is installed in a drilling hole 8 formed in a natural ground 7. For example, since the total length is about 12.5 m, it is formed by connecting four steel pipes 1, 2, 3, 4 of slightly over 3 m buried in the ground. In addition, the full length of the connection steel pipe 9, and the length and number of the natural ground buried steel pipes 1 and 2 to be connected are not limited.
At this time, the front end of the first (head) ground buried steel pipe 1 is installed in the excavator 5 and is drawn into the excavation hole 8 formed following the excavation. Then, the front end of the second (intermediate) underground steel pipe 2 is connected to the rear end of the underground steel pipe 1 and is drawn into an excavation hole 8 formed following the excavation. In the same manner, the front end of the third (intermediate) ground buried steel pipe 3 is connected to the rear end of the ground buried steel pipe 2, and the fourth (rear) ground buried steel pipe 4 is connected to the rear end of the ground buried steel pipe 3. Are connected to each other and drawn into the excavation holes 8 respectively.
And after a part of excavation apparatus 5 is collect | recovered, the injection apparatus 6 for inject | pouring a natural ground reinforcement into the rear end of the natural ground buried steel pipe 4 is installed.

The excavator 5 is a known double-pipe excavator including an inner bit (pilot bit) and an outer bit (ring bit) that can be attached to and detached from each other. Therefore, the excavator 5 shown in FIG. 1 is an outer bit remaining in the natural ground 7.
Further, the injection device 6 includes a closing means for closing the pipe end of the ground buried steel pipe 4, a transport hose for transporting the ground reinforcing agent, a pressure feeding means for applying pressure to the ground reinforcing agent, etc. (Not shown). However, the present invention does not limit the structure of the excavator 5 and the structure of the injection device 6.
In addition, since the natural ground buried steel pipe 3 and the natural ground buried steel pipe 4 are the same, in the following description, each is collectively called the "natural ground buried steel pipe 10". Further, the natural ground buried steel pipe 1 and the natural ground buried steel pipe 4 are obtained by changing a part of the natural ground buried steel pipe 10 (this will be described separately).

(Embedded steel pipe)
In FIG. 2, the natural ground buried steel pipe 10 has a large inner diameter portion 24 formed within a distance e from one end face (hereinafter referred to as “front end face”) 12 and a distance a from the large inner diameter section 24. The inner diameter taper 22 is formed to be connected to the inner surface of the enlarged diameter portion 20, the inner screw 21 formed on the inner surface of the enlarged diameter portion 20, and the inner diameter of the enlarged diameter portion 20. And a main body 11 having an inner surface connected to the inner surface taper 22.
That is, the large inner diameter portion 24, the expanded diameter portion 20, and the inner diameter taper 22 are formed by plastic deformation that expands the inner diameter and the outer diameter (so-called “expand”), and are not upset, and therefore are thinned. .
A screw escape portion or an incomplete screw portion (hereinafter collectively referred to as “inner surface groove”) 23 is formed between the female screw 21 and the inner surface taper 22.
The inner diameter (exactly, the diameter of the tip circle of the female screw 21) and the outer diameter of the enlarged diameter portion 20 are larger than the inner diameter and outer diameter of the main body 11, respectively. The distance between the tooth tip of the female screw 21 and the outer surface of the enlarged diameter portion 20 is smaller (thinner) than the wall thickness of the main body portion 11.
It should be noted that the inner surface of the main body 11 and the inner surface taper 22 are smoothly connected, and the inner surface taper 22 and the inner surface groove 23 are also connected smoothly. However, in order to facilitate understanding, in FIG. 2 and FIG. Draw a solid line.
The inner diameter of the large inner diameter portion 24 is the same as or larger than the thread valley diameter of the female screw 21. Further, the inner diameter large portion 24 may be a tapered surface whose inner diameter increases toward the front end surface 12.

Further, a screw escape portion or an incomplete screw portion (hereinafter collectively referred to as “small portion of outer surface diameter”) 33 is formed on the outer surface within the range of distance b from the other end surface (hereinafter referred to as “rear end surface”) 13, and the outer surface The small diameter portion 33 is formed with an outer surface taper 32 whose outer diameter decreases as it approaches the rear end surface 13. A male screw 31 is formed connected to the outer surface small diameter portion 33, and a screw escape portion or an incomplete screw portion (hereinafter collectively referred to as “outer surface groove”) 34 is formed connected to the male screw 31. In addition, a corner portion (exactly, a range chamfered in a substantially arc-shaped cross section) where the outer surface small diameter portion 33 (the outer surface taper 32 in FIG. 2) and the rear end surface 13 intersect is referred to as a “rear end corner portion 35”. Called.
Furthermore, a plurality of through holes 14 are formed in the main body portion 11 at intervals. The through hole 14 functions as a discharge port for injecting a ground reinforcing agent (not shown) into the ground 7 (see FIG. 1).

Both the inner surface taper 22 and the outer surface taper 32 are frustoconical, and the taper angle of the inner surface taper 22 (hereinafter referred to as “inner surface taper angle”) c is the taper angle of the outer surface taper 32 (hereinafter referred to as “outer surface taper angle”). It is larger than d (c> d).
The outer surface taper 32 formed in the outer surface small diameter portion 33 may be formed in a stepped shape in which a plurality of cylinders having different outer diameters are arranged in place of the truncated cone shape, or the outer surface taper 32 is not formed. Thus, the outer surface small diameter portion 33 and the rear end surface 13 may be connected by chamfering with a substantially circular section.
In addition, the form of the inner surface groove 23 and the outer surface groove 34 is not limited, and may be any form or can be formed as long as the female screw 21 and the male screw 31 can be formed respectively. If there is, it is not necessary to provide it.

(Linking)
In FIG. 3, the front end of the other ground buried steel pipe 10 (the ground buried steel pipe 3 (see FIG. 1)) is connected to the rear end of one ground buried steel pipe 10 (the ground buried steel pipe 2 (see FIG. 1)). Has been. That is, the latter female screw 21 is screwed into the former male screw 31, and the former rear end corner portion 35 and the latter inner surface taper 22 are pressed against each other.
For this reason, in the natural ground buried steel pipe 2, the male screw 31 receives a compressive force in the tube axis direction, and the range of the outer surface taper 32 receives a compressive force (reducing force) in the radial direction. On the other hand, in the natural steel buried steel pipe 3, the female screw 21 receives a tensile force in the pipe axis direction, and the range of the inner surface taper 22 receives a radial tensile force (expansion force).
The present invention does not limit the magnitude of the pressing force (the magnitude of the tightening torque when screwing). Therefore, when the pressing force is large, one or both of the rear end corner portion 35 and the inner surface taper 22 are plastically deformed, and the contact range is expanded or the inner surface taper 22 is bitten. Moreover, although the internal diameter of the range close | similar to the rear-end surface 13 of the natural ground buried steel pipe 2 reduces very slightly, it does not affect excavation work.

The distance a which is the length of the enlarged diameter portion 20 is appropriately selected within the range enabling the connection, and the distance b which is the length of the outer surface small diameter portion 33 is appropriately selected within the range allowing the pushing. It is to be selected.
The male screw 31 and the female screw 21 that are screwed to each other usually have a very small gap between the respective screw threads and screw valleys, and the thread surface of the male screw 31 (slope on the rear end surface 13 side). A very slight gap is also formed between the screw surface of the female screw 21 (the slope opposite to the front end face 12), but such a gap is not drawn in FIG. Although the male screw 31 and the female screw 21 are depicted as trapezoidal screws, the present invention is not limited to this, and any screw may be used.

Moreover, although the inner surface taper angle c is larger than the outer surface taper angle d, the present invention is not limited to this, and both may be the same value. At this time, the inner surface taper 22 and the outer surface taper 32 abut on a wide range.
In FIG. 3, the male thread 31 and the outer surface groove 34 of one of the natural ground buried steel pipes 10 (the natural ground buried steel pipe 2) are large in the inner diameter of the other natural ground buried steel pipe 10 (the natural ground buried steel pipe 3). Although it is surrounded by 24 and not exposed from the front end face 12, the present invention is not limited to this.
That is, the lengths (number of spirals) of the female screw 21 and the male screw 31 may be the same or different, and are appropriately selected. For this reason, the rear end corner portion 35 may be pressed against the inner surface taper 22 when the end of the outer surface groove 34 near the main body portion 11 coincides with the front end surface 12.

Referring again to FIG. 1, the first (first) ground buried steel pipe 1 is for removing the enlarged diameter portion 20 of the ground buried steel pipe 10 and installing a part of the excavator 5 near the front end face 12. This is the same as that provided with a structure (not shown).
The fourth (rear) ground buried steel pipe 4 is the same as that provided with a structure (not shown) for installing a part of the injection device 6 near the rear end surface 13 of the ground buried steel pipe 10. There are cases where the male screw 31 or the like is left as it is, and cases where the male screw 31 or the like is removed.
In the above, the case where the natural steel buried steel pipe 10 is a steel pipe for injecting a reinforcing agent has been described as an example, but the present invention is not limited to this. For example, the injection device 6 may not be installed at the rear end of the ground buried steel pipe 10, and the “drainage steel pipe” may be used without supplying the reinforcing agent in the pipe. At this time, the through hole 14 functions as an entrance for water (groundwater), and the shape thereof is not limited to a circle, and may be a long hole or a slit. On the other hand, it may be inclined or vertical.

(Function and effect)
Since the natural ground buried steel pipes 10 are connected as described above, the following effects can be obtained.
(A) The thickness of the female screw 21 part (distance between the screw valley bottom and the outer surface of the enlarged diameter portion 20) and the thickness of the male screw 31 part (distance between the screw valley bottom and the inner surface) do not form the enlarged diameter portion 20. Therefore, the breaking strength is improved when the female screw 21 and the male screw 31 screwed together are separated in the tube axis direction.
(B) Further, since the breaking strength is improved, the thickness of the main body 11 can be reduced to a value that can secure the breaking strength and the crushing strength to predetermined values. Is promoted.
(C) Furthermore, since the outer surface small diameter portion 33 (rear end corner portion 35) and the inner surface taper 22 are pressed against each other, the screw surface of the male screw 31 (the slope opposite to the rear end surface 13) and the screw of the female screw 21 are used. The contact surface pressure with the surface (the slope on the front end surface 12 side) increases, and a frictional force acts between the outer surface small diameter portion 33 and the inner surface taper 22, thereby causing the male screw 31 and the female screw 21 to move. Screwing is difficult to loosen.
(D) Further, when the female screw 21 and the male screw 31 are screwed together, the tightening torque is increased by pressing the outer surface small diameter portion 33 and the inner surface taper 22 against each other. Can be confirmed to be screwed in as designed, and screwing failure (insufficient tightening) is eliminated.
(E) Furthermore, since the large inner diameter portion 24 is formed, the outer surface taper 32 can be easily inserted and workability is improved.
(F) It should be noted that the frictional force overcomes the plastic deformation when the outer surface small diameter portion 33 and the inner surface taper 22 are pressed against each other to cause plastic deformation (eg, galling) to relax. It includes the power of

[Embodiment 2]
4 and 5 illustrate a natural ground buried steel pipe according to Embodiment 2 of the present invention. FIG. 4 is a side view showing a part thereof, and FIG. 5 is a side view showing a part in a use situation. is there. In addition, the same code | symbol is attached | subjected to the part which is the same as Embodiment 1, or an equivalent, and description is abbreviate | omitted. FIG. 4 shows a cross section above the center line indicated by the alternate long and short dash line.
In FIG. 4, the natural ground buried steel pipe 40 is obtained by removing the outer surface taper 32 in the natural ground buried steel pipe 10 and changing the corners of the outer surface small diameter portion 33 and the rear end surface 13 to the rear end corner portion 36. The other parts are the same as those of the natural ground buried steel pipe 10.

For this reason, when connecting the rear end of the natural ground buried steel pipe 40 (more precisely, the natural ground buried steel pipe 2) and the front end of the natural ground buried steel pipe 40 (more precisely, the natural ground buried steel pipe 3), the male screw 31 and the female The screw 21 is screwed, the rear end corner portion 36 abuts on the inner surface taper 22, and the range of the outer surface taper 32 receives a compressive force in the tube axis direction and a compressive force in the radial direction (diameter reducing force). .
At this time, since the large inner diameter portion 24 is formed, the small outer surface diameter portion 33 can be easily inserted. In particular, since the large inner diameter portion 24 is a tapered surface that expands toward the front end surface 12, insertion is further facilitated.
Therefore, in the natural ground buried steel pipe 40, the breaking strength between the female screw 21 and the male screw 31 is improved, and the weight reduction is promoted, and the screw between the male screw 31 and the female screw 21 is promoted similarly to the natural mountain buried steel pipe 10. There is an effect that it becomes difficult to loosen. In addition, although the internal diameter of the range close | similar to the rear-end surface 13 of the natural ground buried steel pipe 40 shrinks very slightly, it does not affect excavation work.
The small outer surface diameter portion 33 is cylindrical and has the same outer diameter in the axial direction (same as or smaller than the thread valley diameter of the male screw 31), but the rear end corner portion 36 is chamfered (C Chamfering or R chamfering) is provided.

[Embodiment 3]
FIG. 6 is a side view showing a part in the use situation for explaining a natural ground buried steel pipe according to Embodiment 4 of the present invention, in which the upper side is a cross-section above the center line indicated by a one-dot chain line. In addition, the same code | symbol is attached | subjected to the same part as Embodiment 1, or a corresponding part, and description is abbreviate | omitted (refer FIG. 3).
In FIG. 6, the natural ground buried steel pipe 60 removes the outer surface small diameter portion 33 (including the external surface taper 32) from the natural ground buried steel pipe 40 (see FIG. 4) to form the male screw 31 that reaches the rear end surface 13. It is a thing. In the connecting steel pipe 9, the male thread 31 of one ground buried steel pipe 60 is screwed into the female thread 21 of the other ground buried steel pipe 60.

At this time, the male screw 31 close to the rear end surface 13 enters the inner surface groove 23, and a corner portion (hereinafter referred to as “male screw end corner portion 37”) where the rear end surface 13 and the male screw 31 intersect with each other is formed in the inner surface taper 22. It is pressed.
Since the male screw 31 is spiral, the male screw end corner 37 is formed at the corner with the screw thread, the corner with the screw surface (slope), or the corner with the screw bottom. The corner portion with the thread having the larger diameter is pressed against the inner surface taper 22. The male screw end corner portion 37 may be chamfered or may not be chamfered.

(Function and effect)
Since the natural ground buried steel pipes 60 are connected as described above, the same effect as the natural ground buried steel pipe 10 (Embodiment 1) is exhibited. That is, the breaking strength is improved and the weight reduction is promoted, and the screwing between the male screw 31 and the female screw 21 is difficult to loosen.
In particular, the male screw 31 is pressed against the inner taper 22 at the corner with the screw thread, and the corner with the screw bottom is not pressed against the inner taper 22. If it does so, local plastic deformation (galling) will generate | occur | produce or a nonuniform force will act on a screw surface in the circumferential direction, and screwing will become difficult to loosen further. However, depending on the number of threads of the male screw 31 (the same applies to the female screw 21), the one-sided state may not occur.
Moreover, it can confirm that it was screwing as designed by the increase in tightening torque, and a screwing defect (tightening insufficient) is eliminated. Furthermore, since the outer diameter small portion 33 (screw escape portion or the like) is not provided, processing is facilitated, and a protector (not shown) for protecting the male screw 31 before construction can be shortened. Becomes cheaper.
Furthermore, since the large inner diameter portion 24 is formed, the male screw 31 can be easily inserted. In particular, since the large inner diameter portion 24 is a tapered surface that expands toward the front end surface 12, insertion is further facilitated.

(Modified example of screw)
FIGS. 7A and 7B illustrate a modification of the screw of the ground buried steel pipe shown in FIG. 6. FIG. 7A is a side view showing a part, and FIG. 7B is a side view showing a part thereof enlarged. .
The male screw 80 shown in FIG. 7 replaces the male screw 31 in FIG. That is, the female screw 21 and the male screw 31 are both trapezoidal screws, but the male screw 80 is a deformed trapezoidal screw (same as a so-called “r screw” or “rope screw”). In other words, a part of the range corresponding to the slope of the trapezoidal screw (the range between the extension lines indicated by the ends of the double-ended arrows) has the screw straight portion 82 and corresponds to the linear thread and the screw bottom of the trapezoidal screw. In this range, an arcuate thread arc portion 81 and a screw bottom arc portion 83 that are gently connected to the screw straight portion 82 are provided. A female screw (not shown) is a deformed trapezoidal screw that is screwed into the male screw 80.
Therefore, the ground buried steel pipe 60 that has been changed to the male screw 80 (the female screw is the same) that is a deformed trapezoidal screw can be more easily screwed, so that the workability is further improved.
In addition, the natural ground buried steel pipe 10 (Embodiment 1) and the natural ground buried steel pipe 40 (Embodiment 2) can also be deformed into deformed trapezoidal screws, and workability can be improved by such deformation.

The present invention has been described based on the first to third embodiments. Those skilled in the art will understand that the first to third embodiments are exemplifications, and that various modifications can be made to the respective components and combinations thereof, and that such modifications are also within the scope of the present invention. By the way.
That is, a water draining steel pipe that uses the through-hole 14 as an opening for allowing fluid to flow into the pipe from the outside of the pipe, and a steel pipe that does not have the through-hole 14 and uses the space inside the pipe for a predetermined purpose are all used. It is a natural mountain buried steel pipe 10.

  Since the present invention is as described above, the present invention is not limited to the AGF method and the like, and can be widely used as a ground buried steel pipe in various methods, further as a steel pipe for various drainage and various steel pipes for a predetermined purpose.

1: Local underground steel pipe (top)
2: Natural steel buried steel pipe (intermediate)
3: Ground buried steel pipe (intermediate)
4: Ground buried steel pipe (tail)
5: Drilling device 6: Injection device 7: Ground mountain 8: Drilling hole 9: Connecting steel pipe 10: Ground mountain buried steel pipe (Embodiment 1)
DESCRIPTION OF SYMBOLS 11: Main-body part 12: Front-end surface 13: Rear-end surface 14: Through-hole 20: Diameter-expanded part 21: Female screw 22: Internal taper 23: Internal groove 31: Male screw 32: External taper 33: Small external-surface part 34: External surface Groove 35: Rear end corner 36: Rear end corner 37: Male screw end corner 40: Ground buried steel pipe (Embodiment 2)
60: Ground buried steel pipe (Embodiment 3)
80: Male thread 81: Thread arc portion 82: Screw linear portion 83: Screw bottom arc portion a: Distance from the large inner diameter of the female screw b: Distance from the rear end surface of the small outer diameter portion c: Inner taper angle d: outer surface taper angle e: distance from the front end surface of the large inner surface diameter

Claims (4)

It is a natural ground buried steel pipe that is connected in series and buried in the natural ground,
An enlarged diameter portion formed in a predetermined range from one end face;
A female screw formed on the inner surface of the enlarged diameter portion;
A large inner diameter portion formed between one end face and the female screw;
An inner surface taper formed so as to be connected to the inner surface of the enlarged diameter portion, and the inner diameter decreases as the distance from one end surface increases.
A male screw formed in a predetermined range from the other end face;
The male thread of one ground buried steel pipe and the female thread of the other ground buried steel pipe are screwed together, and the male thread of one ground buried steel pipe and the inner surface taper of the other ground buried steel pipe, A natural steel buried steel pipe characterized by pressing together. It is a natural ground buried steel pipe that is connected in series and buried in the natural ground,
An enlarged diameter portion formed in a predetermined range from one end face;
A female screw formed on the inner surface of the enlarged diameter portion;
A large inner diameter portion formed between one end face and the female screw;
An inner surface taper formed so as to be connected to the inner surface of the enlarged diameter portion, and the inner diameter decreases as the distance from one end surface increases.
A small outer surface diameter portion formed on the outer surface of the predetermined range from the other end surface;
A male screw connected to the outer surface small diameter part,
The male thread of one ground buried steel pipe and the female thread of the other ground buried steel pipe are screwed together, and the outer surface small diameter portion of one ground buried steel pipe and the inner surface of the other ground buried steel pipe A natural steel pipe buried in a taper and pressed against the ground.   The outer surface small diameter portion has an outer surface taper in which the outer diameter decreases toward the other end surface closer to the other end surface, and the ratio of the inner surface taper decreasing in inner diameter is the ratio in which the outer diameter of the outer surface taper decreases. 3. The natural ground burial according to claim 2, wherein a corner of the inner surface taper of one of the natural ground buried steel pipes and a corner of the outer surface taper of the other natural ground buried steel pipe and the other end surface are pressed against each other. Steel pipe. 4. The ground according to claim 1, wherein the male screw and the female screw are a trapezoidal screw or a deformed trapezoidal screw in which a screw thread portion and a screw bottom portion are formed in a circular arc shape in cross section. Mountain buried steel pipe.

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