JP6955942B2 - Ground buried steel pipe - Google Patents

Description

The present invention relates to a ground-buried steel pipe, particularly a ground-buried steel pipe buried in the ground or the ground.

Conventionally, as steel pipes buried in the ground or the ground (hereinafter collectively referred to as "ground"), for example, steel pipes for injecting ground reinforcement into the ground and for discharging water from the ground. Steel pipes and the like are known.
For example, when constructing a tunnel on a fragile ground, it is used in a construction method such as the "AGF construction method" in which excavation is started with the front of the face stable. In such a construction method, a plurality of steel pipes (hereinafter referred to as "connecting steel pipes") are placed so as to be arranged in a substantially arch shape diagonally upward in front of the face, and the connecting steel pipes are a plurality of steel pipes connected in series with each other. (Hereinafter, each of the steel pipes is referred to as a "ground buried steel pipe").
That is, the first (head) ground buried steel pipe is drawn into the excavation hole formed by the excavation following the excavation by installing the excavation device at the front end thereof. Then, 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 drilling hole following the excavation. Is done. Similarly, the third (intermediate) ground buried steel pipe and the fourth (intermediate or tail) ground buried steel pipe are connected and drawn into the excavation hole as a connecting steel pipe.

Then, when the excavation (pull-in) of the connected steel pipe is completed, the ground reinforcing agent (same as the stabilizer or fixing agent) is supplied to the inside from the rear end, and the ground reinforcing agent is applied to the side surface of the ground buried steel pipe. By injecting into the ground through the through hole provided in, it is made "for reinforcing agent injection". Alternatively, instead of injecting a reinforcing agent, groundwater is taken in through a through hole inside without supplying a ground reinforcing agent or the like to make it "for draining water".
The length of the connected steel pipes, the length and the number of the ground buried steel pipes to be connected are not limited, and the posture of the connected steel pipes may be horizontal, inclined or vertical with respect to the horizontal. Further, the inside may be a container or the inside may be a flow path (the excavator is removed) without providing the through hole.

The ground-buried steel pipe has a crushing strength that can withstand the pressure of the ground and a strength that does not separate from each other when pulled in, that is, a breaking strength that does not break the connecting part, and is for facilitating handling and pulling in during construction. Weight reduction is required.
When the connection between the ground-buried steel pipes is made by screwing the male screw formed at one pipe end and the female screw formed at the other pipe end, the male screw and the female screw are the ground-buried steel pipes. Since the threads are screwed at approximately the center of the wall thickness, the wall thickness at the male thread portion (distance from the bottom of the screw root to the inner surface) and the wall thickness at the female screw portion (distance from the bottom of the screw valley to the outer surface) are reduced.
Therefore, since the breaking strength is lowered, and when an attempt is made to increase the wall thickness to guarantee the breaking strength, the breaking strength becomes heavy. Therefore, an invention for solving these problems has been disclosed (see, for example, Patent Document 1). ).

Japanese Unexamined Patent Publication No. 2012-149458 (Page 5-7, FIG. 2)

In the invention disclosed in Patent Document 1 (corresponding to a steel pipe buried in the ground), a male screw is formed on the outer surface of one pipe end portion, and the diameter of the other pipe end portion is enlarged to increase the inner surface of the enlarged diameter portion. In addition, a female screw to be screwed into the male screw is formed.
For this reason, the wall thickness of the male threaded portion and the wall thickness of the female threaded portion should be set to a predetermined thickness to improve the breaking strength, and the wall thickness of the ground-buried steel pipe should be reduced by improving the breaking strength ( Weight reduction) is possible. In the embodiment described in Patent Document 1, the ground buried steel pipe is a steel pipe having a relatively small diameter of 76.3 mm and a wall thickness of 4.2 mm, and is outside the expanded portion. The diameter is 81.7 mm and the wall thickness is 3.9 mm.

However, when excavating while giving a blow or rotation to the excavator, the ground is repeatedly hit or rotated many times, or the excavator is repeatedly raised and lowered, so the vibration at that time is a male screw. It is repeatedly transmitted to the threaded part with the female screw. Then, in the ground buried steel pipe disclosed in Patent Document 1, the outer diameter of the enlarged diameter portion becomes larger and the wall thickness becomes smaller (thinner) as compared with the portion where the diameter is not expanded, and the cross-sectional rigidity decreases. Therefore, there is a problem that the screw 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, 114.3 mm, etc.) or when applied to a thinner steel pipe (for example, 3.9 mm, etc.), the enlarged diameter portion As the outer diameter of the steel pipe becomes larger and the wall thickness becomes thinner, this problem becomes remarkable.

INDUSTRIAL APPLICABILITY The present invention provides a ground-buried steel pipe that solves such a problem, guarantees crushing strength and breaking strength, and can suppress the possibility of loosening of the screw between the male screw and the female screw. be.

(1) The ground-buried pipe according to the present invention is a ground-buried steel pipe that is connected in series with each other and buried in the ground, and has a diameter-expanded portion formed in a predetermined range from one end face and the above-mentioned. A female screw formed on the inner surface of the enlarged diameter portion, a large inner surface diameter formed between one end surface and the female screw, and a large inner surface formed by connecting to the inner surface of the enlarged diameter portion and moving away from one end surface. It has an inner surface taper whose inner diameter decreases to a certain extent, and a male screw formed in a predetermined range from the other end face and reaching the other end face.
The male screw of one ground-buried steel pipe and the female screw of the other ground-buried steel pipe are screwed together, and the corner where the male screw of one ground-buried steel pipe and the other end face intersect is the other. It is characterized in that it is pressed against the inner surface taper of the ground buried steel pipe.
(2) Further, it is a ground-buried steel pipe that is connected in series with each other and is buried in the ground, and is formed on a diameter-expanded portion formed in a predetermined range from one end face and an inner surface of the diameter-expanded portion. A female screw, a large inner surface diameter formed between one end surface and the female screw, and an inner surface taper formed by connecting to the inner surface of the enlarged diameter portion and whose inner diameter decreases as the distance from one end surface increases. It has a cylindrical outer surface diameter small portion formed on the outer surface within a predetermined range from the other end face and reaching the other end face, and a male screw formed connected to the outer surface diameter small portion.
A corner portion where the male screw of one ground-buried steel pipe and the female screw of the other ground-buried steel pipe are screwed together, and the small outer surface diameter portion of one ground-buried steel pipe and the other end face intersect. Is pressed against the inner surface taper of the other ground buried steel pipe.
(3) Further, it is a ground-buried steel pipe that is connected in series with each other and buried in the 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, and a large inner surface diameter formed between one end face and the female screw. An inner surface taper formed by connecting to the inner surface of the enlarged diameter portion and whose inner diameter decreases as the distance from one end surface decreases, an outer surface diameter small portion formed on an outer surface within a predetermined range from the other end surface, and the outer surface diameter small portion. Has a male screw formed by connecting to
The male screw of one ground-buried steel pipe and the female screw of the other ground-buried steel pipe are screwed together, and the outer surface diameter small portion of one ground-buried steel pipe and the inner surface of the other ground-buried steel pipe are screwed together. The outer surface diameter small portion is pressed against the taper, and the outer surface diameter portion is provided with an outer surface taper whose outer diameter decreases as it approaches the other end surface, and the rate at which the inner diameter of the inner surface taper decreases is outside the outer surface taper. greater than the rate of diameter is reduced, and the inner surface taper of one natural ground embedded steel pipe, it shall be the said corners of the other of said outer surface tapered and the other end surface of the natural ground buried steel pipe jostle.
(4) Further, the male screw and the female screw are trapezoidal screws or deformed trapezoidal screws having a thread portion and a screw bottom formed in an arc shape in cross section.

Since the ground-buried steel pipe according to the present invention has the above-mentioned structure, it has the following effects.
(A) The wall thickness of the portion where the female screw is formed (distance between the bottom of the screw root and the outer surface of the enlarged diameter portion) and the wall thickness of the portion where the male screw is formed (distance between the bottom of the screw root and the inner surface) are expanded. Since it is increased as 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 together are to be separated in the pipe axis direction is improved.
(B) Further, since the breaking strength is improved, the wall thickness can be reduced to a value that can guarantee the breaking strength and the crushing strength to predetermined values, respectively, so that the weight reduction is promoted. NS.
(C) Further, since the male screw and the inner surface taper are pressed against each other, or the small outer surface diameter portion and the inner surface taper are pressed against each other, the contact between the screw surface (slope) of the male screw and the screw surface (slope) of the female screw As the surface pressure increases, a frictional force acts between the male screw and the inner surface taper, or a frictional force acts between the small outer surface diameter portion and the inner surface taper, so that the male screw and the female screw are screwed together. It becomes difficult to loosen the screws.
(D) Further, since it has a large inner surface diameter portion, it is easy to insert a male screw or a small inner diameter diameter portion, and workability is improved.
(E) Further, since the male screw and the female screw are trapezoidal screws or deformed trapezoidal screws (same as so-called "r screws" and "rope screws"), they are easily screwed and have high breaking strength.

It is sectional drawing of the side view which shows the usage situation explaining the ground-buried steel pipe which concerns on Embodiment 1 of this invention. It is a side view explaining the ground buried steel pipe which concerns on Embodiment 1 of this invention. It is a side view which shows a part in the usage situation of the ground buried steel pipe shown in FIG. It is a side view explaining the ground buried steel pipe which concerns on Embodiment 2 of this invention. It is a side view which shows a part in the usage situation of the ground buried steel pipe shown in FIG. It is a side view which shows a part in the usage situation explaining the ground buried steel pipe which concerns on Embodiment 3 of this invention. A modified example of the screw of the ground buried steel pipe shown in FIG. 6 will be described. FIG. 6A is a side view showing a part, and FIG. 6B is a side view showing a part enlarged.

Hereinafter, embodiments for carrying out the invention (hereinafter, referred to as “Embodiments 1 , 2, 3 ”) will be described with reference to the drawings. It should be noted that each figure is schematically drawn, and the present invention is not limited to the illustrated form (shape, number of parts, etc.). Further, in order not to complicate the drawing, the description of some members or some symbols may be omitted.

[Embodiment 1]
1 to 3 show the ground buried steel pipe according to the first embodiment of the present invention by taking "a steel pipe for injecting a reinforcing agent" in the AGF method as an example, and FIG. 1 shows a usage situation. A cross-sectional view of a side view, FIG. 2 is a side view, and FIG. 3 is a side view showing a part of a usage situation. Note that FIGS. 2 and 3 have a cross section above the center line indicated by the alternate long and short dash line.

(Connecting pipe)
The connecting steel pipe 9 used in the known AGF method in FIG. 1 is a steel pipe for injecting a reinforcing agent, and is installed in a drilling hole 8 formed in a ground 7. For example, since the total length is about 12.5 m, it is formed by connecting four ground-buried steel pipes 1, 2, 3, and 4 of more than 3 m in series. The total length of the connected steel pipe 9 and the length and number of the 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 excavation device 5 and is drawn into the excavation hole 8 formed following the excavation. Then, the front end of the second (intermediate) ground buried steel pipe 2 is connected to the rear end of the ground buried steel pipe 1, and is drawn into the excavation hole 8 formed following the excavation. Similarly, the front end of the third (middle) ground buried steel pipe 3 is connected to the rear end of the ground buried steel pipe 2, and the fourth (tail) ground buried steel pipe 4 is connected to the rear end of the ground buried steel pipe 3. The front ends of the pipes are connected and each is drawn into the drilling hole 8.
Then, after a part of the excavation device 5 is recovered, an injection device 6 for injecting the ground reinforcing agent is installed at the rear end of the ground buried steel pipe 4.

The excavation device 5 is a known double-tube excavation device including an inner bit (pilot bit) and an outer bit (ring bit) that are detachable from each other, and is an inner bit (not shown) after excavation is completed. The excavator 5 shown in FIG. 1 is an outer bit remaining in the ground 7.
Further, the injection device 6 includes a closing means for closing the pipe end portion 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, and the like (either of them). Not shown). However, the present invention does not limit the structure of the excavation device 5 and the structure of the injection device 6.
Since the ground buried steel pipe 3 and the ground buried steel pipe 4 are the same, they are collectively referred to as “ground buried steel pipe 10” in the following description. Further, the ground-buried steel pipe 1 and the ground-buried steel pipe 4 are partially modified ground-ground steel pipes 10 (this will be described separately).

(Ground buried steel pipe)
In FIG. 2, the ground buried steel pipe 10 has an inner surface diameter large portion 24 formed in a range of a distance e from one end surface (hereinafter referred to as “front end surface”) 12 and a range a distance a from the inner surface diameter large portion 24. The inner surface taper 22 is formed by connecting the diameter-expanded portion 20 formed in the above, the female screw 21 formed on the inner surface of the diameter-expanded portion 20, and the inner surface of the diameter-expanded portion 20, and the inner diameter decreases as the distance from the front end surface 12 increases. And a main body portion 11 having an inner surface connected to the inner surface taper 22.
That is, the large inner diameter portion 24, the enlarged diameter portion 20, and the inner surface taper 22 are formed by plastic deformation that expands the inner diameter and the outer diameter (so-called “expand”), and are not upset, so that the wall thickness is reduced. ..
Further, a screw relief 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 (to be exact, the diameter of the tooth tip circle of the female screw 21) and the outer diameter of the enlarged diameter portion 20 are larger than the inner diameter and the outer diameter of the main body portion 11, respectively, and the wall thickness of the enlarged diameter portion 20 (to be exact). , The distance between the 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.
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 smoothly connected. However, in order to facilitate understanding, these boundaries are shown in FIGS. 2 and 3. A solid line is drawn on.
The inner diameter of the large inner surface diameter 24 is the same as or larger than the thread valley diameter of the female screw 21. Further, the large inner surface diameter 24 may be a tapered surface whose inner diameter increases toward the front end surface 12.

Further, a screw relief portion or an incomplete screw portion (hereinafter collectively referred to as "outer surface diameter small portion") 33 is formed on the outer surface within a range of a distance b from the other end surface (hereinafter referred to as "rear end surface") 13, and the outer surface is formed. 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. Then, a male screw 31 is formed by connecting to the small outer diameter portion 33, and a screw relief portion or an incomplete screw portion (hereinafter collectively referred to as an “outer surface groove”) 34 is formed by connecting to the male screw 31. The corner portion where the small outer surface diameter portion 33 (outer surface taper 32 in FIG. 2) and the rear end surface 13 intersect (to be exact, the range chamfered in a substantially arcuate cross section) is referred to as the “rear end corner portion 35”. Called.
Further, a plurality of through holes 14 are formed in the main body 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 have a truncated cone shape, 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 (referred to) d (c> d).
The outer surface taper 32 formed on the outer surface diameter small portion 33 may be formed in a stepped shape in which a plurality of cylinders having different outer diameters are arranged instead of the truncated cone shape, or the outer surface taper 32 is not formed. Then, the small outer diameter portion 33 and the rear end surface 13 may be connected by chamfering a substantially arc in cross section.
The form of the inner surface groove 23 and the outer surface groove 34 is not limited, and any form may be used 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 (ground buried steel pipe 3 (see FIG. 1)) is connected to the rear end of one ground buried steel pipe 10 (ground buried steel pipe 2 (see FIG. 1)). Has been done. That is, the female screw 21 of the latter is screwed into the male screw 31 of the former, and the rear end corner portion 35 of the former and the inner surface taper 22 of the latter are pressed against each other.
Therefore, in the ground buried steel pipe 2, the male screw 31 receives a compressive force in the pipe axial direction, and the range of the outer surface taper 32 receives a compressive force (diameter reduction force) in the radial direction. On the other hand, in the ground buried steel pipe 3, the female screw 21 receives a tensile force in the pipe axial direction, and the range of the inner surface taper 22 receives a tensile force (diameter expanding force) in the radial direction.
The present invention does not limit the magnitude of the pressing force (the magnitude of the tightening torque at the time of screwing). Therefore, when the pressing force is large, one or both of the rear end corner portion 35 and the inner surface taper 22 is plastically deformed to expand the contact range or bite into the inner surface taper 22. Further, although the inner diameter in the range close to the rear end surface 13 of the ground buried steel pipe 2 is slightly reduced, it does not affect the excavation work.

Then, the distance a, which is the length of the enlarged diameter portion 20, is appropriately selected within the range that enables the connection, and the distance b, which is the length of the small outer surface diameter portion 33, is appropriately selected within the range that enables the pressing. It is to be selected.
The male screw 31 and the female screw 21 screwed together usually have a very small gap formed between each thread and the thread valley, and the screw surface of the male screw 31 (slope on the rear end surface 13 side). A very small gap is also formed between the screw surface and the screw surface of the female screw 21 (the slope opposite to the front end surface 12), but such a gap is not drawn in FIG. Further, although the male screw 31 and the female screw 21 are drawn as trapezoidal screws, the present invention does not limit the screw shape to this, and any screw may be used.

Further, the inner surface taper angle c has a value larger than the outer surface taper angle d, but the present invention is not limited to this, and both may have the same value. At this time, the inner surface taper 22 and the outer surface taper 32 come into contact with each other in a wide range.
In FIG. 3, the male screw 31 and the outer groove 34 of one ground-buried steel pipe 10 (ground-buried steel pipe 2) have a large inner surface diameter of the other ground-buried steel pipe 10 (ground-buried steel pipe 3). Surrounded by 24 and not exposed from the front end surface 12, the present invention is not limited thereto.
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. Therefore, 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.

Again, in FIG. 1, the first (head) 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 surface 12. It is the same as the one provided with a structure (not shown).
Further, the fourth (tail) ground buried steel pipe 4 is the same as the one 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. Therefore, there are cases where the male screw 31 and the like are left as they are, and cases where the male screw 31 and the like are removed.
In the above description, the case where the ground buried steel pipe 10 is used as a steel pipe for injecting a reinforcing agent is described as an example, but the present invention is not limited to this. For example, a “steel pipe for draining water” may be used without installing the injection device 6 at the rear end of the ground buried steel pipe 10 and without supplying a reinforcing agent into the pipe. At this time, the through hole 14 functions as an inlet for water (groundwater), and its shape is not limited to a circular shape, but may be an elongated hole or a slit, and the buried posture is horizontal or horizontal. On the other hand, it may be inclined or vertical.

(Action effect)
Since the ground-buried steel pipes 10 are connected to each other as described above, the following effects are exhibited.
(A) The wall thickness of the female screw 21 part (distance between the screw root bottom and the outer surface of the diameter-expanded portion 20) and the wall thickness of the male screw 31 part (distance between the screw valley bottom and the inner surface) do not form the diameter-expanded portion 20. Since the increase is increased as compared with the case where the female screw 21 and the male screw 31 are formed in the above, the breaking strength when the female screw 21 and the male screw 31 screwed together are pulled apart in the pipe axis direction is improved.
(B) Further, since the breaking strength is improved, the wall thickness of the main body 11 can be reduced to a value that can secure each of the breaking strength and the crushing strength to a predetermined value, so that the weight is reduced. The conversion is promoted.
(C) Further, since the small outer surface 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 The contact surface pressure with the surface (slope on the front end surface 12 side) increases, and a frictional force acts between the outer surface diameter small portion 33 and the inner surface taper 22, so that the male screw 31 and the female screw 21 The screw becomes hard to loosen.
(D) Further, when the female screw 21 and the male screw 31 are screwed together, the tightening torque increases due to the pressing of the small outer surface diameter portion 33 and the inner surface taper 22, so that the female screw 21 and the male screw 31 It can be confirmed that the screw is screwed as designed, and the screwing failure (insufficient tightening) is eliminated.
(E) Further, since the large inner surface diameter 24 is formed, the outer surface taper 32 can be easily inserted and the workability is improved.
(F) The frictional force means that when plastic deformation (galling or the like) occurs on the contact surface between the small outer surface diameter portion 33 and the inner taper 22 due to pressing against each other, the frictional force overcomes the plastic deformation and relaxes. Includes the power to.

[Embodiment 2]
4 and 5 show a ground-buried steel pipe according to a second embodiment of the present invention, FIG. 4 is a side view showing a part, and FIG. 5 is a side view showing a part in a usage situation. be. The same parts as those in the first embodiment or the parts corresponding to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. FIG. 4 has a cross section above the center line indicated by the alternate long and short dash line.
In FIG. 4, in the ground-buried steel pipe 40, the outer surface taper 32 is removed from the ground-buried steel pipe 10, and the corner portion between the outer surface diameter small portion 33 and the rear end surface 13 is made into a rear end corner portion 36. The part other than this is the same as that of the ground buried steel pipe 10.

Therefore, when the rear end of the ground buried steel pipe 40 (to be exact, the ground buried steel pipe 2) and the front end of the ground buried steel pipe 40 (to be exact, the ground buried steel pipe 3) are connected, 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 diameter small portion 33 receives the compressive force in the pipe axis direction and the compressive force in the radial direction (diameter reduction force). Receive.
At this time, since the large inner surface diameter portion 24 is formed, the small outer surface diameter portion 33 can be easily inserted. In particular, since the large inner surface diameter 24 is made into a tapered surface that expands toward the front end surface 12, insertion is further facilitated.
Therefore, in the ground-buried steel pipe 40, similarly to the ground-buried steel pipe 10, the breaking strength between the female screw 21 and the male screw 31 is improved, weight reduction is promoted, and the screw between the male screw 31 and the female screw 21 is promoted. It has the effect of making it difficult for the screws to loosen. Although the inner diameter in the range close to the rear end surface 13 of the ground buried steel pipe 40 is slightly reduced, it does not affect the excavation work.
The small outer surface diameter portion 33 is cylindrical and has the same outer diameter in the axial direction (same as the screw valley diameter of the male screw 31 or smaller than the screw valley diameter), 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 of the use situation for explaining the ground buried steel pipe according to the third embodiment of the present invention, and has a cross section above the center line shown by the alternate long and short dash line. The same parts as those in the first embodiment or the corresponding parts are designated by the same reference numerals, and some description thereof will be omitted (see FIG. 3).
In FIG. 6, the ground-buried steel pipe 60 forms a male screw 31 that reaches the rear end surface 13 by removing the small outer surface diameter portion 33 (including the outer surface taper 32) of the ground-buried steel pipe 40 (see FIG. 4). It was done. Then, in the connecting steel pipe 9, the male screw 31 of one ground buried steel pipe 60 is screwed into the female screw 21 of the other ground buried steel pipe 60.

At this time, the male screw 31 close to the rear end surface 13 penetrates into the inner surface groove 23, and the corner portion where the rear end surface 13 and the male screw 31 intersect (hereinafter referred to as “male screw end angle portion 37”) becomes the inner surface taper 22. It is being 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, but is outside. The corner portion with the screw thread having a larger diameter is pressed against the inner surface taper 22. Further, the male screw end corner portion 37 may be chamfered or not chamfered.

(Action effect)
Since the ground-buried steel pipes 60 are connected to each other as described above, they have the same effect as the ground-buried steel pipe 10 (Embodiment 1). That is, the breaking strength is improved, weight reduction is promoted, and the screw between the male screw 31 and the female screw 21 is less likely to loosen.
In particular, the male screw 31 is pressed against the inner surface taper 22 at the corner with the screw thread, and is not pressed against the inner surface taper 22 at the corner with the screw bottom, so that a so-called "one-sided contact state" occurs. Then, local plastic deformation (galling) occurs, or a non-uniform force acts on the screw surface in the circumferential direction, making it more difficult for the screw to loosen. However, depending on the number of male threads 31 (same for female threads 21), the one-sided contact state may not occur.
Further, by increasing the tightening torque, it can be confirmed that the screw is screwed as designed, and the screwing failure (insufficient tightening) is eliminated. Further, by not providing the small outer diameter portion 33 (screw relief portion or the like), processing becomes easy and the protector (not shown) that protects the male screw 31 can be shortened before construction, so that the manufacturing cost Will be cheaper.
Further, since the large inner surface diameter 24 is formed, the male screw 31 can be easily inserted. In particular, since the large inner surface diameter 24 is made into a tapered surface that expands toward the front end surface 12, insertion is further facilitated.

(Modification example of screw)
7A and 7B explain a modified example of the screw of the ground buried steel pipe shown in FIG. 6, in which FIG. 7A is a side view showing a part, and FIG. 7B is a side view showing a part 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 were both trapezoidal screws, but the male screw 80 is a deformed trapezoidal screw (same as a so-called "r screw" or "rope screw"). That is, the screw straight portion 82 is provided in a part of the range corresponding to the slope of the trapezoidal screw (the range between the dimensional auxiliary lines indicated by the tips of the arrow ends), and corresponds to the straight thread and the screw bottom of the trapezoidal screw. An arcuate thread arc portion 81 and a screw bottom arc portion 83 that are gently connected to the screw straight line portion 82 are provided in the range to be formed. The female screw (not shown) is also a modified trapezoidal screw that is screwed into the male screw 80.
Therefore, the ground-embedded steel pipe 60 changed to the male screw 80 (the same applies to the female screw), which is a deformed trapezoidal screw, can be screwed more easily, and thus the workability is further improved.
The ground-buried steel pipe 10 (Embodiment 1) and the ground-buried steel pipe 40 (Embodiment 2) can also be deformed into deformed trapezoidal screws, and the workability can be improved by such deformation.

The present invention has been described above based on the first to third embodiments. It will be understood by those skilled in the art that the first to third embodiments are examples, and various modifications are possible for each of the components and combinations thereof, and such modifications are also within the scope of the present invention. By the way.
That is, any steel pipe for draining water, which uses the through hole 14 as an opening for allowing fluid to flow into the pipe from outside the pipe, and a steel pipe which does not have the through hole 14 and uses the space inside the pipe for a predetermined purpose. It is a ground buried steel pipe 10.

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 construction methods, as a steel pipe for draining various types of water, and as various steel pipes for a predetermined purpose.

1: Ground buried steel pipe (top)
2: Ground buried steel pipe (middle)
3: Ground buried steel pipe (middle)
4: Ground buried steel pipe (tail)
5: Excavation device 6: Injection device 7: Ground 8: Drilling hole 9: Connected steel pipe 10: Ground buried steel pipe (Embodiment 1)
11: Main body 12: Front end surface 13: Rear end surface 14: Through hole 20: Diameter expansion part 21: Female screw 22: Inner surface taper 23: Inner surface groove 31: Male screw 32: Outer surface taper 33: Outer surface diameter small part 34: Outer surface Groove 35: Rear end corner 36: Rear end corner 37: Male thread end corner 40: Ground buried steel pipe (Embodiment 2)
60: Ground buried steel pipe (Embodiment 3)
80: Male screw 81: Thread arc part 82: Thread straight part 83: Thread bottom arc part a: Distance from the large inner diameter of the female screw b: Distance from the rear end surface of the small outer diameter c: Inner surface 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 ground-buried steel pipe that is connected in series with each other and buried in the ground.
A diameter-expanded portion formed in a predetermined range from one end face,
The female screw formed on the inner surface of the enlarged diameter portion and
A large part of the inner surface diameter formed between one end face and the female screw,
An inner surface taper that is formed by connecting to the inner surface of the enlarged diameter portion and whose inner diameter decreases as the distance from one end surface increases.
It has a male screw that is formed in a predetermined range from the other end face and reaches the other end face.
The male screw of one ground-buried steel pipe and the female screw of the other ground-buried steel pipe are screwed together, and the corner where the male screw of one ground-buried steel pipe and the other end face intersect is the other. A ground-buried steel pipe, characterized in that it is pressed against the inner surface taper of the ground-buried steel pipe. It is a ground-buried steel pipe that is connected in series with each other and buried in the ground.
A diameter-expanded portion formed in a predetermined range from one end face,
The female screw formed on the inner surface of the enlarged diameter portion and
A large part of the inner surface diameter formed between one end face and the female screw,
An inner surface taper that is formed by connecting to the inner surface of the enlarged diameter portion and whose inner diameter decreases as the distance from one end surface increases.
A cylindrical outer surface diameter small portion formed on the outer surface within a predetermined range from the other end face and reaching the other end face,
It has a male screw formed by connecting to the small outer diameter portion, and has a male screw.
A corner portion where the male screw of one ground-buried steel pipe and the female screw of the other ground-buried steel pipe are screwed together, and the small outer surface diameter portion of one ground-buried steel pipe and the other end face intersect. Is pressed against the inner surface taper of the other ground-buried steel pipe. It is a ground-buried steel pipe that is connected in series with each other and buried in the ground.
A diameter-expanded portion formed in a predetermined range from one end face,
The female screw formed on the inner surface of the enlarged diameter portion and
A large part of the inner surface diameter formed between one end face and the female screw,
An inner surface taper that is formed by connecting to the inner surface of the enlarged diameter portion and whose inner diameter decreases as the distance from one end surface increases.
A small outer surface diameter formed on the outer surface within a predetermined range from the other end face,
It has a male screw formed by connecting to the small outer diameter portion, and has a male screw.
The male screw of one ground-buried steel pipe and the female screw of the other ground-buried steel pipe are screwed together to form the outer surface diameter small portion of one ground-buried steel pipe and the inner surface of the other ground-buried steel pipe. The taper pushes against each other,
The small outer surface diameter portion is provided with an outer surface taper whose outer diameter decreases as it approaches the other end face toward the other end face, and the rate at which the inner diameter of the inner surface taper decreases is the rate at which the outer diameter of the outer surface taper decreases. larger than, the inner surface tapered and, rock mass embedded steel you characterized in that the corners of the other of said outer surface tapered and the other end surface of the natural ground buried steel pipe jostling of one natural ground embedded steel pipe. The ground according to any one of claims 1 to 3, wherein the male screw and the female screw are a trapezoidal screw or a modified trapezoidal screw having a thread portion and a screw bottom formed in an arc shape in cross section. Mountain buried steel pipe.

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