Joints for steel pipes in slit dams, joint units, and steel slit dams

Abstract

When a large external force is applied to a steel slit dam, a large bending moment acts on the joint between the pair of steel pipes, making it important to improve the joint strength of the connection. [Solution] The slit dam steel pipe joint C is positioned at the joint between two opposing pairs of steel pipes among a plurality of steel pipes S that constitute a steel slit dam. The slit dam steel pipe joint C comprises a first wall portion 10 that can be joined to the end of one steel pipe S, a second wall portion 20 positioned at a first distance d from the first wall portion toward the other steel pipe, and a cylindrical side wall portion 30 connecting the first wall portion and the second wall portion. The first wall portion includes a first joint portion 13 that is joined to the steel pipe at a first position 71, the side wall portion includes a second joint portion 33 that is joined to the second wall portion at a second position 72 that is outside the first position with respect to the central axis Ac, and the second wall portion includes a joining means application portion 23 formed at a third position 73 that is outside the second position.

Description

Technical Field

[0007] ,

[0001] This invention relates to a slit dam steel pipe joint, a joint unit including the same, and a steel slit dam.

Background Art

[0002] Steel slit dams are constructed in mountain valleys, rivers, etc. for the purpose of capturing boulders, driftwood, etc. generated by debris flows, etc., or attenuating (reducing the momentum) debris flows, etc. to prevent disasters in advance (see, for example, Patent Document 1).

[0003] This steel slit dam is constructed by assembling a slit structure by joining a pair of opposed steel pipes among a plurality of steel pipes on a concrete foundation.

[0004] For joining a pair of steel pipes, a steel pipe with a flange in which an annular flange plate is welded in advance to the joining edge of each steel pipe is used.

[0005] This flange plate is typically a steel plate in which a plurality of bolt holes are formed. At the assembly construction site, the flange plates of the steel pipes with flanges to be joined are brought into contact with each other, and a pair of steel pipes are joined by passing bolts through the bolt holes and fastening them with nuts.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] When a large external force is applied to a steel slit dam due to a debris flow or the like, a large bending moment is applied to the joint between two opposing pairs of steel pipes that make up the steel slit dam. Therefore, it is important to improve the joint strength of the joint in order to maintain the connection between the steel pipes. [Means for solving the problem]

[0008] One aspect of this invention is a joint for steel pipes in a slit dam, which is arranged at the joint between two opposing pairs of steel pipes that make up a steel slit dam. This joint for steel pipes in a slit dam comprises a first wall portion that can be joined to the end of one of the pair of steel pipes, a second wall portion that is positioned at a first distance from the first wall portion toward the other steel pipe of the pair, and a cylindrical side wall portion that connects the first wall portion and the second wall portion. The first wall portion includes a first joint portion that is joined to the one steel pipe at a first position, the side wall portion includes a second joint portion that is joined to the second wall portion at a second position that is outside the first position with respect to the central axis of the side wall portion, and the second wall portion includes a joining means application portion that applies joining means that can be directly or indirectly joined to the other steel pipe, and is formed at a third position that is outside the second position with respect to the central axis.

[0009] In this slit dam steel pipe joint, the side wall connecting the first wall and the second wall is joined to the second wall at a position (second position) outside the joint position (first position) between one steel pipe and the first wall. Furthermore, a joining means application section for applying joining means that can directly or indirectly join to the other steel pipe is positioned at a position (third position) outside the joint position (second position) between the side wall and the second wall. That is, by connecting the first wall and the second wall via a cylindrical side wall, the joining means application section can be positioned at a third position outside the first and second positions. Therefore, it is possible to directly or indirectly join to the other steel pipe at a position further outward from the central axis than the first and second positions. Consequently, a resisting moment that can effectively resist the large bending moment acting on the joint between the pair of steel pipes can be applied. As a result, the joint strength of the joint can be improved.

[0010] Furthermore, in this slit dam steel pipe joint, by connecting the first wall and the second wall via a cylindrical side wall, it is easy to form a stress transmission path that spreads outward from one steel pipe towards the other steel pipe. Therefore, it is easy to suppress the decrease in bending rigidity as one moves from the joint position between one steel pipe and the first wall (first position) towards the joint position between the side wall and the second wall (second position). Consequently, without increasing the wall thickness of the second wall where the joining means is applied, it is possible to directly or indirectly join with the other steel pipe at a position further outward than the first and second positions.

[0011] The slit dam steel pipe joint may further include a plurality of inner reinforcing ribs connecting the first wall portion and the inner circumferential surface of the side wall portion. In this case, since the slit dam steel pipe joint includes a plurality of inner reinforcing ribs, stress can be easily distributed and transmitted between the first wall portion and the side wall portion.

[0012] The slit dam steel pipe joint may further include a plurality of external reinforcing ribs connecting the second wall portion and the outer circumferential surface of the side wall portion. In this case, since the slit dam steel pipe joint includes a plurality of external reinforcing ribs, it is easier to distribute and transmit stress between the second wall portion and the side wall portion. In addition, the plurality of external reinforcing ribs make it easier to prevent damage to the slit dam steel pipe joint from being directly hit by large boulders or driftwood generated by debris flows, etc., which would hit the side wall portion or the second wall portion.

[0013] The slit dam steel pipe joint may further include a plurality of inner reinforcing ribs connecting the first wall portion and the inner circumferential surface of the side wall portion, and a plurality of outer reinforcing ribs connecting the second wall portion and the outer circumferential surface of the side wall portion. In this case, since the slit dam steel pipe joint includes a plurality of inner reinforcing ribs and a plurality of outer reinforcing ribs, stress can be easily distributed and transmitted on both the inner and outer sides of the side wall portion.

[0014] The plurality of inner reinforcing ribs may include a first inner reinforcing rib, and the plurality of outer reinforcing ribs may include a first outer reinforcing rib arranged to face the first inner reinforcing rib via the side wall. In this case, since the first inner reinforcing rib and the first outer reinforcing rib are arranged to face each other via the side wall, stress can be easily transmitted directly between the inside and outside of the side wall.

[0015] Preferably, the first wall portion includes a plate-like portion formed to protrude from the first position toward the central axis so as to close the opening formed at the end of one of the steel pipes. In this case, since the first wall portion of the slit dam steel pipe joint includes a plate-like portion formed to close the opening formed at the end of the steel pipe, it is possible to suppress the inflow of fluids (especially liquids) into the steel pipe and the corrosion of the steel pipe.

[0016] Another aspect of this invention is a joint unit. This joint unit comprises at least one steel pipe from among a plurality of steel pipes constituting a steel slit dam, and a joint for slit dam steel pipes having the above-described features, which is joined to the end of the steel pipe.

[0017] Another aspect of this invention is a steel slit dam comprising a plurality of joint units having the features as described above, and joining means for joining the plurality of joint units to each other.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 9 is a side view of a slit dam unit constituting a steel slit dam according to an embodiment of this invention. [Figure 2] FIG. 12 is a perspective view for explaining the joining structure of a pair of steel pipes. [Figure 3] FIG. 15 is an exploded perspective view for explaining the joining structure of a pair of steel pipes. [Figure 4] FIG. 18 is a top view for explaining the configuration of a joint for a slit dam steel pipe. [Figure 5] FIG. ၂၁ is a bottom view for explaining the configuration of a joint for a slit dam steel pipe. [Figure 6] FIG. 24 is a side view seen in the direction of arrow VI in FIG. 4. [Figure 7] FIG. 27 is a cross-sectional view seen from cutting plane line VII-VII in FIG. 4.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of this invention will be described in detail with reference to the accompanying drawings.

[0020] FIG. 1 is a side view of a slit dam unit 1 constituting a steel slit dam according to an embodiment of this invention.

[0021] The steel slit dam is constructed by arranging a plurality of slit dam units 1 in a direction 3 perpendicular to the plane of FIG. 1 on a concrete foundation 2 and connecting them to each other. The direction 3 perpendicular to the plane of FIG. 1 is, for example, the direction crossing a valley or a river.

[0022] The slit dam unit 1 is constructed by transporting multiple parts P, which are manufactured in advance in a factory, to the site and assembling them there. Each part P includes at least one steel pipe S. Some parts P have a branch section 4 or a bend section 5. The branch section 4 is formed by welding one end of another steel pipe S, which has a different central axis direction, to the middle section of one steel pipe S. The bend section 5 is formed by welding one end of another steel pipe S, which has a different central axis direction, to one end of one steel pipe S, or by bending the middle section of one steel pipe S. Each part P has a connecting end 7 for joining with other parts P. The connecting end 7 is located at the end of the steel pipe S that make up part P. A slit dam steel pipe joint C is joined to the connecting end 7.

[0023] Figure 2 is a perspective view illustrating the joint structure between a first steel pipe S1, which constitutes a first part P1, and a second steel pipe S2, which constitutes another part P2. Figure 3 is an exploded perspective view thereof.

[0024] The first steel pipe S1 and the second steel pipe S2 are a pair of opposing steel pipes S among the multiple steel pipes S that constitute the slit dam unit 1, and are a pair of steel pipes S that should be joined together. A first slit dam steel pipe joint C1 (hereinafter referred to as "first joint C1") and a second slit dam steel pipe joint C2 (hereinafter referred to as "second joint C2") are placed at the respective joining ends 7 of these pairs of steel pipes S1 and S2.

[0025] More specifically, a first joint C1 is welded (joined) to the end of a first steel pipe S1 to form a first jointed steel pipe 81 (joint unit). Similarly, a second joint C2 is welded (joined) to the end of a second steel pipe S2 to form a second jointed steel pipe 82 (joint unit). The first joint C1 and the second joint C2 are joined to each other by a joining means 60, thereby joining the first jointed steel pipe 81 and the second jointed steel pipe 82 to each other. In this embodiment, the joining means 60 is a fastening means 60 including a bolt 61 and a nut 62 that is screwed onto it.

[0026] In this embodiment, the first joint C1 and the second joint C2 are joined together such that the central axis A1 of the first steel pipe S1 and the central axis A2 of the second steel pipe S2 are parallel to each other, and typically their central axes A1 and A2 (collectively referred to as "central axis A") are located on approximately the same straight line.

[0027] Figure 4 is a top view illustrating the common configuration of the first joint C1 and the second joint C2, and Figure 5 is its bottom view. Figure 6 is a side view taken in the direction of arrow VI in Figure 4, and Figure 7 is a cross-sectional view taken along the cutting line VII-VII in Figure 4.

[0028] In this embodiment, the first joint C1 and the second joint C2 have substantially the same configuration. Hereinafter, the first joint C1 and the second joint C2 will be collectively referred to as "joint C".

[0029] The first joint C1 includes a first wall portion 10 that can be joined to the end of the first steel pipe S1 (one of the steel pipes S) of a pair of steel pipes S to be joined together, a second wall portion 20 positioned at a first distance d (see Figure 7) from the first wall portion 10 toward the second steel pipe S2 (the other steel pipe S) of the pair of steel pipes S, and a cylindrical side wall portion 30 connecting the first wall portion 10 and the second wall portion 20. The first wall portion 10 includes a first joint portion 13 that is joined to one of the steel pipes S at a first position 71. The side wall portion 30 includes a second joint portion 33 that is joined to the second wall portion 20 at a second position 72 that is outside the first position 71 with respect to the central axis Ac of the cylindrical side wall portion 30. The same applies to the second joint C2 that is joined to the end of the second steel pipe S2 (the other steel pipe S).

[0030] The second wall portion 20 includes a joining means application portion 23 to which joining means 60 that can be joined to the second wall portion 20 of the second joint C2 (see Figure 2) is applied, and the joining means application portion 23 is formed at a third position 73 that is outside the second position 72 with respect to the central axis Ac. In this embodiment, the joining means application portion 23 includes a plurality of through holes 23 that penetrate the second wall portion 20 in a direction parallel to the central axis Ac. In this embodiment, the second wall portion 20 of the first steel pipe S1 and the second steel pipe S2 (the other steel pipe S) are joined indirectly via the second joint C2, but the second wall portion 20 of the first steel pipe S1 and the second steel pipe S2 (the other steel pipe S) may be joined directly without the second joint C2.

[0031] When the joint C is welded (joined) to the steel pipe S, the central axis Ac of the cylindrical side wall portion 30 is parallel to the central axis A of the steel pipe S, and typically the central axis Ac of the cylindrical side wall portion 30 and the central axis A of the steel pipe S are located substantially on the same straight line.

[0032] In this embodiment, the end of the steel pipe S is annular, and the first joint 13 is annular. The side wall portion 30 is cylindrical, and the second joint portion 33 is annular. The second position 72 is located outside (farther from the central axis Ac) than the first position 71 in any radial direction centered on the central axis Ac of the cylindrical side wall portion 30.

[0033] The first wall portion 10 is configured as a flat plate intersecting the central axis Ac of the cylindrical side wall portion 30, and is typically configured as a plate perpendicular to the central axis Ac of the cylindrical side wall portion 30, and has a flat joining surface 11 to which the first steel pipe S1 (one of the steel pipes S) is joined. When the end of the first steel pipe S1 is annular and the joining surface 11 of the first wall portion 10 is perpendicular to the central axis Ac of the side wall portion 30, the first joining portion 13 exhibits an annular shape. In this embodiment, the first wall portion 10 is formed as a flat canopy that completely closes the inner space 35 of the cylindrical side wall portion 30 on one end 30a of the side wall portion 30. Therefore, the first wall portion 10 includes a plate-like portion 14 that is formed to protrude from the first position 71 (first joint portion 13) toward the central axis Ac of the side wall portion 30, so as to close the opening 85 formed at the end of the first steel pipe S1 that is joined to the first wall portion 10.

[0034] The joint surface 11 preferably has an appropriate width in the radial direction (meaning the radial direction perpendicular to the central axis Ac; the same applies hereinafter) so that it can accommodate multiple types of steel pipes S with different diameter sizes, and it is preferable that the joint surface 11 be a flat, annular or circular region centered on the central axis Ac.

[0035] The second wall portion 20 is configured as a flat plate intersecting the central axis Ac of the cylindrical side wall portion 30, and is typically configured as a plate along a plane perpendicular to the central axis Ac of the cylindrical side wall portion 30. The second wall portion 20 has a flat mating surface 21 that abuts with the second wall portion 20 of the second joint C2. When the side wall portion 30 is cylindrical and the second wall portion 20 is a flat plate perpendicular to the central axis Ac, the second joint portion 33 exhibits an annular shape.

[0036] In this embodiment, the centers of both the first joint 13 and the second joint 33 are located on the central axis Ac of the cylindrical side wall 30, and the second joint 33 has a larger diameter than the first joint 13, giving it an annular shape. In this embodiment, the second wall 20 is formed so as to open the inner space 35 of the cylindrical side wall 30 at the other end 30b of the side wall 30. Specifically, it is formed as a plate that protrudes outward from the other end 30b of the side wall 30, away from the central axis Ac.

[0037] In this embodiment, the first wall portion 10, the second wall portion 20, and the side wall portion 30 constitute a joint body 8 having a so-called hat-shaped outer form. The first wall portion 10 is typically a flat plate with a uniform thickness. Therefore, the inner surface 12 facing the inner space 35 that is partitioned together with the side wall portion 30 and the joint surface 11 (outer surface) are substantially parallel. The second wall portion 20 is also typically a flat plate with a uniform thickness and has a mating surface 21 facing the second joint C2 and a non-facing surface 22 substantially parallel to the mating surface 21.

[0038] The side wall portion 30 is typically cylindrical (or tubular) with a uniform thickness defined by the distance between the inner circumferential surface 31 and the outer circumferential surface 32, and the inner circumferential surface 31 and the outer circumferential surface 32 are substantially parallel. In this embodiment, the side wall portion 30 is substantially cylindrical. Both the inner circumferential surface 31 and the outer circumferential surface 32 are surfaces substantially parallel to the central axis Ac and are substantially cylindrical surfaces. However, the inner circumferential surface 31 and the outer circumferential surface 32 may be inclined with respect to the central axis Ac such that they approach the central axis Ac as one moves from the second wall portion 20 toward the first wall portion 10.

[0039] The joint C includes reinforcing ribs 40 and 50 in addition to the joint body 8. The reinforcing ribs 40 and 50 include a plurality of inner reinforcing ribs 40 arranged inside the side wall portion 30 and a plurality of outer reinforcing ribs 50 arranged outside the side wall portion 30.

[0040] As shown in Figures 5 and 7, the multiple inner reinforcing ribs 40 are arranged to connect the first wall portion 10 and the inner circumferential surface 31 of the side wall portion 30. That is, the multiple inner reinforcing ribs 40 are connected to the inner surface 12 of the first wall portion 10 and the inner circumferential surface 31 of the side wall portion 30. In this embodiment, the inner circumferential surface 31 of the side wall portion 30 is a substantially cylindrical surface about the central axis Ac, and when viewed parallel to the central axis Ac, it forms a circumference centered on the central axis Ac. The multiple inner reinforcing ribs 40 are arranged at equal intervals along this circumference. Each inner reinforcing rib 40 is a flat plate and is arranged along a plane containing the central axis Ac. Therefore, when viewed parallel to the central axis Ac, it is aligned with the radius of the circumference formed by the inner circumferential surface 31 of the side wall portion 30. As a result, the multiple inner reinforcing ribs 40 are arranged radially around the central axis Ac.

[0041] As best illustrated in Figure 7, each inner reinforcing rib 40 has a first joining edge 41 joined to the inner circumferential surface 31 of the side wall portion 30, a second joining edge 42 joined to the inner surface 12 of the first wall portion 10, and an inner edge 43 that connects the inner circumferential surface 31 of the side wall portion 30 and the inner surface 12 of the first wall portion 10 and faces the central axis Ac. The inner edge 43 is in contact with the inner circumferential surface 31 at position 43a near the joining position between the side wall portion 30 and the second wall portion 20, and is in contact with the inner surface 12 of the first wall portion 10 at position 43b, which is radially inward from position 43a (in the direction toward the central axis Ac). In the illustrated example, the inner edge 43 is straight, but it may be curved in part or in whole. For example, the inner edge 43 may have a curved portion designed to optimize the stress state.

[0042] The multiple inner reinforcing ribs 40 do not all need to be the same shape, and may include multiple types of inner reinforcing ribs 40 that differ in shape and / or thickness. In this embodiment, the inner reinforcing ribs 40 are formed in a tapered shape, where the distance between one main surface 45 and the other main surface 46 (i.e., thickness) decreases from the first wall portion 10 to the second wall portion 20, but they may also have a uniform thickness.

[0043] As shown in Figures 2-4, 6, and 7, the multiple outer reinforcing ribs 50 are arranged to connect the second wall portion 20 and the outer circumferential surface 32 of the side wall portion 30. That is, the multiple outer reinforcing ribs 50 are connected to the non-opposing surface 22 of the second wall portion 20 and the outer circumferential surface 32 of the side wall portion 30. In this embodiment, the outer circumferential surface 32 is a substantially cylindrical surface about the central axis Ac, and when viewed parallel to the central axis Ac, it forms a circumference centered on the central axis Ac. The multiple outer reinforcing ribs 50 are arranged at equal intervals along this circumference. Each outer reinforcing rib 50 is a flat plate and is arranged along a plane containing the central axis Ac. Therefore, when viewed parallel to the central axis Ac, it is aligned with the radius of the circumference formed by the outer circumferential surface 32 of the side wall portion 30. As a result, the multiple outer reinforcing ribs 50 are arranged radially around the central axis Ac.

[0044] As shown in Figures 6 and 7, each outer reinforcing rib 50 has a first joining edge 51 joined to the outer circumferential surface 32 of the side wall portion 30, a second joining edge 52 joined to the second wall portion 20, and an outer edge 53 that connects the outer circumferential surface 32 of the side wall portion 30 and the non-opposing surface 22 of the second wall portion 20 and is oriented away from the central axis Ac. The outer edge 53 contacts the non-opposing surface 22 of the second wall portion 20 at a position 53a radially inward (towards the central axis Ac) from the outer edge of the second wall portion 20, and contacts the outer circumferential surface 32 at a position 53b near the joining position between the side wall portion 30 and the first wall portion 10. In the illustrated example, the outer edge 53 has a first side portion 53c extending substantially parallel to the central axis Ac from the second wall portion 20, and a second side portion 53d extending obliquely to the central axis Ac from the tip of the first side portion 53c to the outer peripheral surface 32, forming a bent shape with an obtuse angle 54 formed where the first side portion 53c and the second side portion 53d meet. Of course, this is just one example, and the outer edge 53 may be curved in part or all. For example, the outer edge 53 may have a curved portion designed to optimize the stress state. In particular, by making the entire outer edge 53 curved without corners, stress concentration can be suppressed.

[0045] The multiple outer reinforcing ribs 50 do not all need to be the same shape, and may include multiple types of outer reinforcing ribs 50 that differ in shape and / or thickness. In this embodiment, the outer reinforcing ribs 50 are formed in a tapered shape, where the distance (i.e., thickness) between one main surface 55 and the other main surface 56 decreases from the second wall portion 20 toward the first wall portion 10, but they may also be of a uniform thickness.

[0046] As shown in Figures 4 and 5, the multiple outer reinforcing ribs 50 include one outer reinforcing rib 50 (first outer reinforcing rib) that is positioned opposite one of the multiple inner reinforcing ribs 40 (first inner reinforcing rib) via the side wall portion 30. In this embodiment, the same number of outer reinforcing ribs 50 as the multiple inner reinforcing ribs 40 are provided, and each inner reinforcing rib 40 and each outer reinforcing rib 50 are opposite each other via one side wall portion 30. That is, one outer reinforcing rib 50 is positioned at each angular position (circumferential position) around the central axis Ac of the multiple inner reinforcing ribs 40. However, the arrangement of the inner reinforcing ribs 40 and outer reinforcing ribs 50 with respect to the circumferential direction 38 around the central axis Ac does not necessarily need to be aligned. For example, the circumferential arrangement 38 between all the inner reinforcing ribs 40 and all the outer reinforcing ribs 50 may be inconsistent, or the circumferential arrangement 38 between some of the inner reinforcing ribs 40 and some of the outer reinforcing ribs 50 may be consistent, while the circumferential arrangement 38 between other inner reinforcing ribs 40 and other outer reinforcing ribs 50 may be inconsistent. Furthermore, the number of inner reinforcing ribs 40 and outer reinforcing ribs 50 do not have to be equal.

[0047] As best shown in Figures 4 and 7, the second wall portion 20 has a plurality of through holes (joining means application portions) 23 that penetrate in a direction parallel to the central axis Ac. In this embodiment, the plurality of through holes 23 are arranged at equal intervals along the circumference located at a third position 73 that is outside (farther from the central axis Ac) than the second position 72 in any radial direction centered on the central axis Ac. The plurality of through holes 23 are arranged to avoid the outer reinforcing ribs 50, and are located one by one between two adjacent outer reinforcing ribs 50, or more specifically, at an intermediate position approximately equidistant from two adjacent outer reinforcing ribs 50. In this embodiment, the outer reinforcing ribs 50 and the through holes 23 are arranged alternately along the circumference centered on the central axis Ac, and the same number of through holes 23 as the number of outer reinforcing ribs 50 are formed in the second wall portion 20. However, the number of outer reinforcing ribs 50 and the number of through holes 23 do not have to be equal. Therefore, there may be no through holes 23 between adjacent outer reinforcing ribs 50, or there may be two or more through holes 23. Also, there may be no outer reinforcing ribs 50 between adjacent through holes 23, or there may be two or more outer reinforcing ribs 50.

[0048] In one specific example, the joint C is made of a single piece of cast steel, comprising at least a first wall portion 10, a second wall portion 20, and a side wall portion 30. In this case, the welding area with the end of the steel pipe S at the joint surface 11 of the first wall portion 10, and the mating surface 21 of the second wall portion 20 may be a machined surface obtained by smoothing the cast surface through machining. Preferably, the first wall portion 10, the second wall portion 20, the side wall portion 30, the inner reinforcing rib 40, and the outer reinforcing rib 50 are made of a single piece of cast steel. This reduces the effort and cost required to weld the reinforcing ribs 40 and 50.

[0049] As shown in Figures 2 and 3, when joining the first jointed steel pipe 81 and the second jointed steel pipe 82, their central axes A1 and A2 are aligned on the same straight line, and the first joint C1 and the second joint C2 are positioned facing each other. The positions of the multiple through holes (jointing means application parts) 23 formed in the second wall portion 20 of the first joint C1 and the second joint C2 are aligned in the circumferential direction 38 (see Figure 4) around the central axis Ac, and their mating surfaces 21 are brought together. In this state, multiple bolts 61 constituting the fastening means (jointing means) 60 are passed through the multiple through holes (jointing means application parts) 23, and multiple nuts 62 are screwed onto the multiple bolts 61. In this way, the first joint C1 and the second joint C2 are fastened together. This joins the first steel pipe with joint 81 (joint unit) and the second steel pipe with joint 82 (joint unit).

[0050] In this example, as clearly shown in Figure 3, washers 63 are placed at the positions of each through hole 23 on the non-opposing surfaces 22 of the second wall portions 20 of the first joint C1 and the second joint C2, and each bolt 61 is inserted through the washer 63, and the head of each bolt 61 and the nut 62 that screws onto the bolt 61 are pressed against the non-opposing surface 22 of the second wall portion 20 via the washer 63 to fasten them.

[0051] In the slit dam steel pipe joint C of this embodiment, the side wall portion 30 connecting the first wall portion 10 and the second wall portion 20 is joined to the second wall portion 20 at a position (second position 72) outside the joining position (first position 71) between the first steel pipe S1 (one steel pipe S) and the first wall portion 10 with respect to the central axis Ac. Furthermore, a through hole (joining means application portion) 23 to which a fastening means (joining means) 60 that can be joined to the second wall portion 20 of the second joint C2 joined to the end of the second steel pipe S2 (the other steel pipe S) is applied is located at a position (third position 73) outside the joining position (second position 72) between the side wall portion 30 and the second wall portion 20.

[0052] In other words, by connecting the first wall portion 10 and the second wall portion 20 via the cylindrical side wall portion 30, the through hole (joining means application portion) 23 can be positioned at a third position 73, which is outside the first position 71 and the second position 72.

[0053] Therefore, the second wall portion 20 of the second joint C2, which is joined to the end of the second steel pipe S2 (the other steel pipe S), can be joined at a position (third position 73) that is further outward from the central axis Ac than the first position 71 and the second position 72.

[0054] Therefore, a resistive moment M2 can be applied to effectively resist the large bending moment M1 acting on the joint T between the pair of steel pipes S(S1,S2) (see Figure 2). As a result, the joint strength of the joint T can be improved.

[0055] Furthermore, in this slit dam steel pipe joint C, by connecting the first wall portion 10 and the second wall portion 20 via a cylindrical side wall portion 30, it is easy to form a stress transmission path that spreads outward from the first steel pipe S1 (one steel pipe S) towards the second steel pipe S2 (the other steel pipe S). Therefore, it is easy to suppress the decrease in bending rigidity as one moves from the joint position between the first steel pipe S1 (one steel pipe S) and the first wall portion 10 (first position 71) towards the joint position between the side wall portion 30 and the second wall portion 20 (second position 72).

[0056] Therefore, without increasing the thickness of the second wall portion 20 in which the through hole (joining means application portion) 23 is formed, it is possible to join the second wall portion 20 of the second joint C2 joined to the end of the first steel pipe S2 (the other steel pipe S) at a position further outward than the first position 71 and the second position 72 (third position 73).

[0057] Furthermore, the slit dam steel pipe joint C of this embodiment is equipped with multiple inner reinforcing ribs 40, which facilitates the distribution and transmission of stress between the first wall portion 10 and the side wall portion 30. In addition, the slit dam steel pipe joint C of this embodiment is equipped with multiple outer reinforcing ribs 50, which facilitates the distribution and transmission of stress between the second wall portion 20 and the side wall portion 30. Moreover, the multiple outer reinforcing ribs 50 help to prevent damage to the slit dam steel pipe joint C from being directly hit by large boulders or driftwood generated by debris flows, etc., which would hit the side wall portion 30 or the second wall portion 20.

[0058] Furthermore, the slit dam steel pipe joint C of this embodiment is equipped with multiple inner reinforcing ribs 40 and multiple outer reinforcing ribs 50, making it easier to distribute and transmit stress on both the inside and outside of the side wall portion 30. Moreover, in this embodiment, at least one inner reinforcing rib 40 (first inner reinforcing rib) and at least one outer reinforcing rib 50 (first outer reinforcing rib) are arranged to face each other via the side wall portion 30, making it easier to transmit stress directly between the inside and outside of the side wall portion 30.

[0059] Furthermore, in this embodiment, the slit dam steel pipe joint C includes a plate-like portion 14 in the first wall portion 10 that is formed to close the opening 85 formed at the end of the steel pipe S. Therefore, it is possible to suppress the inflow of fluids (especially liquids) into the steel pipe S and the corrosion of the steel pipe S.

[0060] Furthermore, by welding (joining) a slit dam steel pipe joint C having the above-described characteristics to at least one of the multiple steel pipes S constituting the steel slit dam and to the end of the steel pipe S, a joint unit can be manufactured, and a part P including such a joint unit can be manufactured.

[0061] Furthermore, a steel slit dam can be constructed by fastening together multiple joint units having the above-described characteristics, more specifically, the second wall portions 20, 20 of a pair of slit dam steel pipe joints C(C1, C2) to each other using fastening means (joining means) 60 to assemble a slit dam unit 1, and by connecting multiple slit dam units 1 to each other.

[0062] Although one embodiment of the present invention has been described above, the invention is not limited to this embodiment, and other forms of implementation are possible within the scope defined in the claims.

[0063] For example, in the above-described embodiment, the steel pipe S, the first wall portion 10, the second wall portion 20, and the side wall portion 30 are formed in a circular shape (annular, circular plate-like, or cylindrical), but some or all of them may be rectangular (for example, square).

[0064] Furthermore, in the above-described embodiment, the first wall portion 10 completely closes the opening 85 formed at the end of the steel pipe S, but the first wall portion 10 may have an opening in a region facing the opening 85. More specifically, the first wall portion 10 may be formed in an inward-facing plate shape that protrudes from one end 30a of the side wall portion 30 toward the central axis Ac, and has an opening in a region including the central axis Ac. Alternatively, the first wall portion 10 may have a portion that protrudes from one end 30a of the side wall portion 30 in a direction away from the central axis Ac.

[0065] Furthermore, in the above-described embodiment, the second wall portion 20 is formed as a plate-like structure that protrudes outward from the other end 30b of the side wall portion 30, away from the central axis Ac. However, the second wall portion 20 may also have a portion that protrudes inward from the other end 30b toward the central axis Ac so as to cover part or all of the inner space 35 of the side wall portion 30.

[0066] Furthermore, in the above-described embodiment, the first wall portion 10, the second wall portion 20, and the side wall portion 30 are constructed in a plate shape, but the plate thickness does not need to be uniformly the same; some or all of the thicknesses may be different.

[0067] Furthermore, in the above-described embodiment, both the inner reinforcing rib 40 and the outer reinforcing rib 50 are provided, but either one of them may be omitted. Moreover, if the first wall portion 10, the second wall portion 20, and the side wall portion 30 can transmit stress while maintaining sufficient strength, the reinforcing ribs 40 and 50 may be omitted.

[0068] Furthermore, in the embodiments described above, expressions such as "annular," "circular shape," "cylindrical," "cylindrical surface," "circumference," "flat," "parallel," "alongside," "orthogonal," "uniform," "on the same line," "equally spaced," and "radial" were used, but it is not necessary for the surface to be strictly in these states. In other words, each of these expressions allows for deviations in manufacturing accuracy, installation accuracy, etc. [Explanation of Symbols]

[0069] 1: Slit Dam Unit 7: Joint end 8: Fitting body 10: First wall 11: Joint surface 13: First joint 14: Plate-like part 20: Second Wall 21: Machining surface 23: Through hole (joining means application part) 30: Side wall section 31: Inner surface 32: Outer surface 33: Second joint 40: Inner reinforcing rib 50: Outer reinforcing rib 60: Fastening means (joining means) 61: Bolt 62: Nut 71: First position 72: Second position 73: Third position 81: First steel pipe with joint (joint unit) 82: Second type of steel pipe with joint (joint unit) 85:Aperture A: Central axis of the steel pipe A1: Central axis of the first steel pipe A2: The central axis of the second steel pipe Ac: Central axis of the side wall C: Fittings for steel pipes used in slit dams C1: First slit dam steel pipe fitting C2: Second slit dam steel pipe joint S: Steel pipe S1: First steel pipe S2: Second steel pipe d: First distance M1: Bending moment M2: Resistive moment

Claims

1. A joint for steel pipes in a slit dam, which is placed at the joint between two opposing pairs of steel pipes among the multiple steel pipes that make up a steel slit dam, A first wall portion that can be joined to the end of one of the pair of steel pipes, A second wall portion is positioned at a first distance from the first wall portion toward the other steel pipe of the pair of steel pipes, It comprises a cylindrical side wall portion connecting the first wall portion and the second wall portion, The first wall portion includes a first joint portion which is joined to the one steel pipe at a first position, The side wall portion includes a second joint portion joined to the second wall portion at a second position which is outside the first position with respect to the central axis of the side wall portion, The second wall portion is a joining means application portion to which joining means that can be directly or indirectly joined to the other steel pipe are applied, and includes a joining means application portion formed at a third position outside the second position with respect to the central axis, Fittings for steel pipes in slit dams.

2. The joint for a slit dam steel pipe according to claim 1, further comprising a plurality of inner reinforcing ribs connecting the first wall portion and the inner circumferential surface of the side wall portion.

3. The joint for a slit dam steel pipe according to claim 1, further comprising a plurality of outer reinforcing ribs connecting the second wall portion and the outer circumferential surface of the side wall portion.

4. Multiple inner reinforcing ribs connecting the first wall portion and the inner circumferential surface of the side wall portion, The joint for a slit dam steel pipe according to claim 1, further comprising a plurality of outer reinforcing ribs connecting the second wall portion and the outer circumferential surface of the side wall portion.

5. The plurality of inner reinforcing ribs include a first inner reinforcing rib, The joint for a slit dam steel pipe according to claim 4, wherein the plurality of outer reinforcing ribs include a first outer reinforcing rib arranged to face the first inner reinforcing rib via the side wall portion.

6. The joint for a slit dam steel pipe according to claim 1, wherein the first wall portion includes a plate-like portion formed to protrude from a first position toward the central axis so as to close an opening formed at the end of one of the steel pipes.

7. At least one of the multiple steel pipes that make up the steel slit dam, A joint unit comprising a slit dam steel pipe joint according to any one of claims 1 to 6, which is joined to the end of the steel pipe.

8. A plurality of joint units according to claim 7, A steel slit dam comprising a joining means for joining the plurality of joint units to each other.

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