Mechanical joint and method for joining steel pipes having the mechanical joint provided at steel pipe end part

Abstract

To provide a mechanical joint which can correct the inclination of each steel pipe upon construction only by a simple structure and components, and a method for joining steel pipes having the mechanical joint provided at a steel pipe end part.SOLUTION: A mechanical joint 1 according to the present invention comprises: a PIN joint 3 and a BOX joint 5; annular grooves 7; and a C type ring member 9. A width of the annular groove 7 of the BOX joint 5 is set to be almost the same as that of the C type ring member 9, and a width of the annular groove 7 of the PIN joint 3 is set wider than that of the annular groove 7 of the BOX joint 5. Sim insertion opening parts 23 that allow the entire width of the annular groove 7 of the PIN joint 33 widely set in an insertion-completed state are provided at three or more points at almost equal intervals in a circumferential direction of the BOX joint 5, and each sim 25 can be inserted from each sim insertion opening part 23 into a gap between the widely set annular groove 7 and the C type ring member 9.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mechanical joint for joining steel pipes, such as steel pipe piles and steel pipe sheet piles, and a method for joining steel pipes having the mechanical joint provided at the ends thereof. [Background technology]

[0002] Joining of steel pipe piles and steel pipe sheet piles has traditionally been done mainly by on-site welding, but in recent years, due to factors such as a decrease in skilled workers, shortened construction periods, and quality control, joining by mechanical joints has become more common. In the case of steel pipe piles and steel pipe sheet piles, the tubular joint members are generally manufactured separately from the steel pipes, and then the joint members are attached to the ends of the steel pipes to be joined by welding, and the joint members are then joined together.

[0003] Because steel pipe piles and steel pipe sheet piles are installed underground, they may tilt slightly even when careful attention is paid to vertical accuracy. If a tilt occurs, the upper steel pipe is adjusted vertically when welding the piles together, and the resulting gap between the upper and lower steel pipes is adjusted by welding. This makes it possible to connect the upper steel pipe vertically even when the lower steel pipe is tilted.

[0004] However, when joining using mechanical joints, the upper steel pipe must be placed in accordance with the inclination of the lower steel pipe, which poses the problem that the upper steel pipe cannot be joined vertically.To address this problem, the following technologies have been devised.

[0005] In Patent Document 1, an upper joint and a lower joint are connected via a connecting member that corresponds to the inclination, while in Patent Document 2, an attitude adjustment mechanism that can adjust the inclination is incorporated into the joint itself. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-121452 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-151131 Summary of the Invention [Problem to be solved by the invention]

[0007] The inclination that occurs at the construction site of steel pipe piles or steel pipe sheet piles varies depending on the site conditions and is not determined until construction is complete. Therefore, the method of Patent Document 1 requires that various connecting members corresponding to the inclination be prepared in advance, and if the inclination that occurs is unexpected, some connecting members may not be applicable, resulting in the problem of extremely high costs.

[0008] Patent Document 2 describes a joint that can be adapted to the slope conditions of the site, but there is a problem in that incorporating the posture adjustment mechanism requires complex processing and special parts, which increases costs.

[0009] The present invention has been made to solve such problems, and aims to provide a mechanical joint that can correct the inclination of steel pipes during construction using only simple structures and parts, and a method for joining steel pipes with such a mechanical joint provided at the ends of the steel pipes. [Means for solving the problem]

[0010] (1) A mechanical joint according to the present invention comprises a tubular PIN joint, a BOX joint into which the PIN joint is inserted, one or more stages of annular grooves formed so as to face each other on the outer circumferential surface of the PIN joint and the inner circumferential surface of the BOX joint, and a C-shaped ring member that can be stored in the annular groove of the BOX joint or the PIN joint so as not to interfere with the insertion of the PIN joint into the BOX joint, and that can be positioned within the annular groove so as to straddle the BOX joint side and the PIN joint side in the inserted state, and is a mechanical joint that is attached to the end of a steel pipe to join steel pipes together, the width of the box joint annular groove is set to be substantially the same as the width of the C-ring member, and the width of the pin joint annular groove is set to be wider than the box joint annular groove, Shim insertion openings are provided at three or more locations at approximately equal intervals around the circumferential direction of the box joint, so that the entire width of the annular groove of the PIN joint, which is set wide, can be seen when the insertion is complete, and a shim can be inserted through the shim insertion openings into the gap between the annular groove of the PIN joint and the C-ring member.

[0011] (2) A method for joining steel pipes each having the mechanical joint described in (1) at the end of the steel pipe, After the pin joint has been fully inserted into the box joint, a C-ring member is placed across the box joint and the pin joint, and then the angle of the upper steel pipe is adjusted so that it faces vertically. After that, a shim is inserted from the shim insertion opening into the gap between the wide annular groove and the C-ring member to fix the angle of the upper steel pipe relative to the lower steel pipe.

[0012] (3) In the device described in (2) above, after the shim is inserted, a plate member is installed to cover the shim insertion opening. [Effects of the Invention]

[0013] According to the mechanical joint of the present invention, the inclination of the steel pipe during construction can be corrected using only a simple structure and parts. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a longitudinal sectional view of a mechanical joint according to an embodiment of the present invention. [Figure 2] 2(a) shows the position where a shim insertion opening is provided in the embodiment, and FIG. 2(b) shows an explanatory diagram of the internal structure as seen from the shim insertion opening. [Figure 3] 1 is an explanatory diagram of a method for joining steel pipes using a mechanical joint according to an embodiment. FIG. [Figure 4] 10 is a view showing a state in which a plate member is installed in a shim insertion opening. FIG. [Figure 5] 10A and 10B are explanatory diagrams of a method for joining steel pipes together using another aspect of the embodiment. [Figure 6] 10A and 10B are explanatory diagrams of a shape of a shim that is preferable in another aspect of the embodiment. [Figure 7] 1 is an explanatory diagram of a configuration of a conventional mechanical joint and a joining method that are the premise of the present invention. [Figure 8] 8 is an explanatory diagram of the movement of the C-ring member of the conventional mechanical joint shown in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0015] Before describing the embodiments of the present invention, an example of a conventional mechanical joint 31 equipped with a pin joint 3 and a box joint 5, which is the premise of the present invention, will be described with reference to Figs. 7(a) shows the state before the PIN joint 3 is inserted into the BOX joint 5, FIG. 7(b) shows the state after insertion is complete, and FIG. 7(c) shows the state after the C-ring member 9 has been expanded. In addition, in each of FIGS. 7(a) to 7(c), the upper part is a vertical cross-sectional view, the middle part is a horizontal cross-sectional view, and the lower part is a view showing the vicinity of the opening 21 provided in the BOX joint 5. 8(a) to 8(c) correspond to FIGS. 7(a) to 7(c), respectively, and are diagrams for explaining the movement of the C-shaped ring member 9. FIG.

[0016] As shown in Figures 7 and 8, a conventional mechanical joint 31 is based on the premise of a mechanical joint 31 that has a tubular pin joint 3, a box joint 5 into which the pin joint 3 is inserted, and one or more stages of annular grooves 7 formed so as to face each other on the outer peripheral surface of the pin joint 3 and the inner peripheral surface of the box joint 5, and that joins the pin joint 3 and box joint 5 by arranging a C-shaped ring member 9 within the annular groove 7 so as to straddle both the box joint 5 side and the pin joint 3 side.

[0017] As shown in Figure 7(a), a conventional mechanical joint 31 consists of a tubular PIN joint 3 and a BOX joint 5 into which the PIN joint 3 is inserted and fitted, and is attached to the end of steel pipes 11 to join the steel pipes 11 together. A step portion 13 is formed on the base end side of the PIN joint 3, and as shown in Figure 7(b), when the PIN joint 3 is inserted into the BOX joint 5, the tip portion 15 of the BOX joint 5 abuts against the step portion 13, thereby completing the insertion. The box joint 5 is the same as what is called an outer joint or a female joint, and the pin joint 3 is the same as what is called an inner joint or a male joint.

[0018] Annular grooves 7M, 7F that face each other when the joints are fully inserted are formed on the outer peripheral surface of the pin joint 3 and the inner peripheral surface of the box joint 5. Note that the letter M is used to indicate only the pin joint side of the annular groove 7, and the letter F is used to indicate only the box joint side. In this example, in the pre-insertion state, the C-shaped ring member 9 is stored in the box joint 5, so the depth of the annular groove 7F of the box joint is the same as or slightly deeper than the thickness of the C-shaped ring member 9. On the other hand, the depth of the annular groove 7M of the pin joint is about half the thickness of the C-shaped ring member 9.

[0019] In addition, the C-shaped ring member 9 stored in the annular groove 7F of the BOX joint is stored so as not to interfere with the insertion of the PIN joint 3 into the BOX joint 5, and is positioned within the annular groove 7 so as to straddle the BOX joint 5 side and the PIN joint 3 side when inserted. The C-shaped ring member 9 has a notch 17 at one location in the circumferential direction, and has a spring structure that expands and contracts in the radial direction.

[0020] When the C-shaped ring member 9 shown in Figure 7 is stored in the annular groove 7F of the box joint, its diameter is forcibly expanded by a diameter expansion jig 19 (see the middle part of Figure 7(a)), and the diameter expansion jig 19 can be operated through an opening 21 provided in the box joint 5.

[0021] The fitting operation of the conventional mechanical joint 31 configured as above will now be described. Before inserting the pin joint 3 into the box joint 5, as shown in Figure 7(a), the C-shaped ring member 9 is stored in the annular groove 7F of the box joint, and the pin joint 3 and the box joint 5 are aligned and the pin joint 3 is inserted into the box joint 5. As shown in FIG. 8(a), the C-ring member 9 is housed in the annular groove 7 on the box joint 5 side, and therefore does not impede the insertion operation.

[0022] As shown in Figure 7(b), insertion of the PIN joint 3 into the BOX joint 5 is completed with the step portion 13 of the PIN joint 3 and the tip of the BOX joint 5 in contact. In this state, the annular grooves 7 formed in the PIN joint 3 and the BOX joint 5 form an annular groove 7 consisting of a circular closed space, and the C-ring member 9 housed in the annular groove 7F of the BOX joint is positioned opposite the annular groove 7M of the PIN joint (see Figure 8(b)).

[0023] Next, when the diameter expansion jig 19 is accessed through the opening 21 and the expanded state of the C-shaped ring member 9 is released, the C-shaped ring member 9 is reduced in diameter by its own spring force, as shown in Figures 7(c) and 8(c), and the C-shaped ring member 9 is positioned so that it straddles both the annular grooves 7 and 7, completing the fitting.

[0024] When the mating is complete, the compressive force is transmitted mainly by the contact pressure between the stepped portion 13 of the pin joint 3 and the tip portion 15 of the box joint 5, and the tensile force is transmitted mainly by the supporting pressure of the C-ring member 9. The torsional force is transmitted by the shear of the bolts (not shown) joining the box joint 5 and the pin joint 3.

[0025] The C-ring member 9 may be accommodated in the annular groove 7M of the PIN joint before insertion. In this case, the diameter of the C-ring member 9 is forcibly reduced by a diameter-reducing jig when accommodated in the annular groove 7M of the PIN joint, and is released from the reduced diameter state when insertion is complete, and is positioned within the annular groove 7 so as to straddle both the box joint 5 side and the PIN joint 3 side.

[0026] In the conventional mechanical joint 31 described above, as described in the background art, the upper steel pipe 11U is installed to match the inclination of the lower steel pipe 11L, so it is sometimes not possible to join the upper steel pipe 11U vertically, and in such cases the posture of the upper steel pipe 11U cannot be corrected in the vertical direction.

[0027] Therefore, the mechanical joint 1 of the present invention corresponds to the above-mentioned conventional mechanical joint 31, to which a function is added that can correct the posture of the upper steel pipe 11U in the vertical direction when the upper steel pipe 11U becomes tilted during joining. A mechanical joint 1 according to this embodiment will be described with reference to Figures 1 and 2. In Figures 1 and 2, parts that are common to Figures 7 and 8 are given the same reference numerals. FIG. 1 is a longitudinal cross-sectional view of a mechanical joint 1 according to this embodiment, FIG. 2(a) is a diagram showing the position of a shim insertion opening 23 in a box joint 5, and FIG. 2(b) is a diagram showing the state in which a shim 25 has been inserted through the shim insertion opening 23.

[0028] 1, in the mechanical joint 1 according to this embodiment, the width of the annular groove 7F of the BOX joint is set to be approximately the same as the width of the C-ring member 9, and the width of the annular groove 7M of the PIN joint is set to be wider than the annular groove 7F of the BOX joint. Here, the widths of the annular grooves 7F and 7M refer to the widths of the groove bottoms (lengths in the axial direction of the joint). 2, the shim insertion openings 23 are provided at three or more locations (four locations in this example) at approximately equal intervals around the circumferential direction of the box joint 5. These shim insertion openings 23 are sized so that the entire width of the wide annular groove 7M can be seen when the joint is fully inserted, and a shim 25 can be inserted through the shim insertion openings 23 into the gap between the wide annular groove 7M and the C-ring member 9. The opening 23 for inserting a shim is different from the opening 21 for operating the expansion jig 19 described in the conventional example, and the mechanical joint 1 of the embodiment also has an opening 21 for operating the expansion jig 19, although not shown. However, the opening 21 can also be used as the shim insertion opening 23 .

[0029] The width of the annular groove 7M of the PIN joint is made wide in order to provide an adjustment margin for correcting the vertical position of the upper steel pipe 11U that is tilted during joining. When the tilted upper steel pipe 11U is adjusted vertically, a gap will form between it and the lower steel pipe 11L, but the maximum allowable gap is generally about 6 mm. Therefore, the groove width as an adjustment allowance should be set to a maximum of about 6 mm wider than the width of the C-ring member 9, regardless of the steel pipe diameter.

[0030] The reason why three or more (four in this example) shim insertion openings 23 are provided is as follows. When correcting the position of the upper steel pipe 11U in the vertical direction, the position of the gap in the circumferential direction varies depending on the direction in which the lower steel pipe 11L is tilted. Therefore, to be able to accommodate gaps in any direction, it is necessary to be able to insert shims in three or more positions in the circumferential direction.

[0031] Furthermore, the vertical width of the shim insertion opening 23 needs to be set so that the entire width of the annular groove 7M of the pin joint can be seen even at the widest gap position. On the other hand, the circumferential width of the shim insertion opening 23 is preferably as short as possible from the standpoint of strength, provided that the shim insertion operation is possible.

[0032] Next, a method for joining steel pipes 11 using the mechanical joint 1 of this embodiment configured as described above will be described with reference to Figure 3. Figure 3 shows the joining procedure in chronological order in Figures 3(a) to 3(d), with Figures 3(a) to 3(c) including partial cross-sectional views showing the movement of the C-ring member 9, and Figure 3(d) including a partial cross-sectional view showing the insertion state of the shim 25.

[0033] In the example shown in Figure 3, a pin joint 3 is attached to the upper end of the lower steel pipe 11L, and a box joint 5 is attached to the lower end of the upper steel pipe 11U. The box joint 5 also has four circumferential openings 23 for inserting shims. As shown in Figure 3(a), the upper steel pipe 11U is positioned to match the inclination of the lower steel pipe 11L, which is installed at an angle, so that the box joint 5 can be inserted into the pin joint 3. Matching the upper steel pipe 11U to the inclination of the lower steel pipe 11L means aligning the center line of the upper steel pipe 11U with the extension of the center line of the lower steel pipe 11L. In this pre-insertion state, the C-ring member 9 is housed in the annular groove 7F of the box joint, as shown in the cross-sectional view.

[0034] Next, as shown in Figure 3(b), when the box joint 5 is inserted into the pin joint 3 and brought into shoulder contact around the entire circumference, the annular groove 7F of the box joint and the annular groove 7M of the pin joint face each other, and the lower groove wall of the box joint 5 and the lower ring groove wall of the annular groove 7M of the pin joint are approximately flush. In this state, when the expanded state of the C-ring member 9 by the diameter expanding jig 19 (not shown) is released, the spring force causes the C-ring member 9 to contract in diameter and position itself so as to straddle the box joint 5 side and the pin joint 3 side. In this way, it is possible to release the expanded diameter state of the C-ring member 9 once the pin joint 3 and the box joint 5 are in shoulder contact over the entire circumference, which provides excellent workability.

[0035] Next, as shown in Figure 3(c), the upper steel pipe 11U is rotated around the shoulder touch part on the left side of the figure as a fulcrum to correct its position so that it is vertical. As a result, the upper steel pipe 11U becomes almost vertical, and a gap gradually widens toward the right side of the figure between the box joint 5 and the pin joint 3. The cross-sectional view in Figure 3(c) shows a cross section at the front position in the figure. When the upper steel pipe 11U is rotated to the left in the figure, the C-shaped ring member 9 moves upward within the annular groove 7M of the PIN joint, so the adjustment margin for the posture of the upper steel pipe 11U is the gap between the C-shaped ring member 9 and the annular groove 7M of the PIN joint in the state shown in Figure 3(b).

[0036] Next, as shown in Figure 3(d), in order to maintain the posture of the upper steel pipe 11U, a shim 25 is inserted into the gap between the pin joint 3 and the C-ring member 9 through the shim insertion opening 23. Figure 3(d) shows a state in which the shim 25 has been inserted through the shim insertion opening 23 at position A on the front side of the figure and position B on the right side of the figure. However, there is also a shim insertion opening 23 on the back side of position A, i.e., at a position rotated 180 degrees from position A, so the shim 25 is inserted at this position as well.

[0037] As shown in the cross-sectional view at position A in Fig. 3(d), at this position, two shims 25 are inserted on the upper side and one shim is inserted on the lower side of the C-shaped ring member 9. Also, as shown in the cross-sectional view at position B in Fig. 3(d), at this position, three shims 25 are inserted on the lower side of the C-shaped ring member 9. By inserting the shim 25, the gap between the C-ring member 9 and the annular groove 7M of the pin joint is closed, so that the upper steel pipe 11U can be maintained in a vertical state.

[0038] The size of the gap between the box joint 5 and the pin joint 3 varies depending on the rotation angle used to correct the posture of the upper steel pipe 11U, and even at the same rotation angle, the size of the gap varies in the circumferential direction. For this reason, multiple thin shims 25 are stacked on top of each other, and if the maximum gap is 4 mm, shims 25 of 0.5 mm, 1 mm, or 2 mm will be sufficient. The shim 25 may be made of an ordinary thin steel plate.

[0039] After inserting the shim 25, it is preferable to install a plate member 27 that covers the shim insertion opening 23, as shown in Fig. 4. By providing the plate member 27, it is possible to prevent the inserted shim 25 from falling out of the shim insertion opening 23. The required radial width of the shim 25 is the same as the depth of the pin groove, but it is preferable that the radially outer end of the shim 25, when inserted, comes close to the surface of the box joint 5. This is because, when the shim insertion opening 23 is covered with the plate member 27, the radially outer end of the shim 25 abuts against the inner surface of the plate member 27, preventing the shim 25 from moving.

[0040] As described above, according to this embodiment, the inclination of the steel pipe 11 during construction can be corrected using only a simple structure and parts.

[0041] Here, we will summarize the relationship between the annular groove 7F of the box joint, the annular groove 7M of the pin joint, and the C-ring member 9. In the above embodiment, the following relationship has been illustrated. <<Present Embodiment>> <Annular groove of box joint> The width is approximately the same as the C-shaped ring member 9, and the depth is approximately the same as the C-shaped ring member 9. The C-shaped ring member 9 is stored before insertion. <Annular groove of PIN joint> The width is wider than the annular groove 7F of the box joint, and the depth is approximately half that of the C-ring member 9

[0042] In addition to the above aspects, the present invention also includes the following aspects: Other Aspects <Annular groove of box joint> The width is approximately the same as the C-shaped ring member 9, and the depth is approximately half that of the C-shaped ring member 9. <Annular groove of PIN joint> The width is wider than the annular groove 7F of the BOX joint, and the depth is approximately the same as the C-ring member 9, so the C-ring member 9 is stored before insertion.

[0043] Regarding the other embodiment, a joining method will be described with reference to FIG. In FIG. 5, the pin joint 3 is on the upper side and the box joint 5 is on the lower side, and the arrangement of the pin joint 3 and the box joint 5 is upside down compared to FIG.

[0044] In another embodiment, as shown in Fig. 5(a), before insertion, the C-ring member 9 is housed in the wide annular groove 7M of the PIN joint 3. At this time, the C-ring member 9 is maintained in a reduced diameter state against its elastic force, and a means for maintaining the reduced diameter state (hereinafter referred to as a "reduced diameter maintaining means") may be, for example, as disclosed in Japanese Patent No. 7294559, a bolt whose shank passes through the C-ring member 9 and is screwed into the PIN joint 3 to compress the C-ring member 9 so that it contacts the bottom of the annular groove 7M of the PIN joint, and the bolt is loosened to release the reduced diameter state. Alternatively, a fastener may be used that is wrapped around the outer periphery of the C-ring member 9 and fastened in a reduced diameter state, as disclosed in Japanese Patent No. 7294559.

[0045] In the retracted state, the C-shaped ring member 9 is located at the lowest position in the annular groove 7M, as shown in Figure 5(a). Therefore, if shoulder contact is made in this state as in Figure 3(b), the C-shaped ring member 9 will be positioned out of alignment with the annular groove 7F of the box joint, and will not be able to enter the annular groove 7F of the box joint even if the contracted state is released. Therefore, as shown in Figure 5(a), a temporary support material 29 is placed at the tip portion 15 of the box joint 5, and the pin joint 3 is inserted into the box joint 5. The thickness of the temporary support material 29 is set so that, as shown in Figure 5(b), when the pin joint 3 is inserted into the box joint 5 and the upper surface of the temporary support material 29 abuts against the stepped portion 13 of the pin joint 3, the positions of the lower groove wall of the annular groove 7M of the pin joint and the lower groove wall of the box joint 5 coincide and are flush.

[0046] When the reduced diameter state of the C-shaped ring member 9 is released in the state shown in Figure 5(b), the diameter of the C-shaped ring member 9 expands and it is positioned straddling both the annular groove 7M of the PIN joint and the annular groove 7F of the BOX joint, as shown in Figure 5(c).

[0047] Next, the temporary receiving member 29 is removed, and the pin joint 3 is further inserted deeper to create the shoulder touch state shown in Fig. 5(d), which corresponds to the state shown in Fig. 3(b). Thereafter, the upper steel pipe 11U is rotated around the shoulder touch portion as a fulcrum to correct its position so that it is in the vertical direction. As a result, the upper steel pipe 11U becomes almost vertical, and a gap is created between the box joint 5 and the pin joint 3 that gradually widens as it moves away from the fulcrum of the rotation.

[0048] Next, as shown in FIG. 5(e), a shim 25 is inserted into the gap between the pin joint 3 and the C-ring member 9 through the shim insertion opening 23 in order to fix the position of the upper steel pipe 11U. A and B in FIG. 5(e) indicate the portions corresponding to A and B in FIG. Depending on the position of the gap, the shim 25 can be inserted both above and below the C-shaped ring member 9, but basically it can be inserted on only one side.

[0049] In another embodiment, the annular groove 7M of the PIN joint is deep, leaving a space behind the C-ring member 9. Therefore, if the shim 25 is inserted above the C-ring member 9, the weight of the rearward side is heavy if the shim 25 is rectangular, which could cause the shim 25 to fall toward the rear. Therefore, as shown in Fig. 6, it is preferable to form notches 25b in the portion of the shim 25 that faces the rear when inserted, with the exception of both ends 25a, and the portion located in the space being cut away. With this shape, when the shim 25 is inserted, both ends 25a abut against the groove bottom of the annular groove 7M of the PIN joint, restricting the insertion position of the shim 25. Furthermore, the reduced weight on the rearward side prevents the shim 25 from falling into the annular groove 7M of the PIN joint. [Explanation of symbols]

[0050] 1, 31 Mechanical couplings 3 PIN fitting 5 Box fittings 7 Annular groove 7M PIN joint annular groove 7F BOX joint annular groove 9 C-ring member 11 Steel pipe 11U upper steel pipe 11L lower steel pipe 13 Step 15 Tip 17 Notch 19 Expanding tool 21 Opening 23 Shim insertion opening 25 Sim 25a Both ends of the shim 25b Shim notch 27 Plate members 29 Temporary support material

Claims

1. a box joint into which the pin joint is inserted; one or more stages of annular grooves formed so as to face each other on the outer peripheral surface of the pin joint and the inner peripheral surface of the box joint; and a C-ring member that can be stored in the annular groove of the box joint or the pin joint so as not to interfere with the insertion of the pin joint into the box joint, and that can be positioned within the annular groove so as to straddle the box joint side and the pin joint side in the inserted state, wherein the mechanical joint is attached to the end of a steel pipe to join steel pipes together, the width of the box joint annular groove is set to be substantially the same as the width of the C-ring member, and the width of the pin joint annular groove is set to be wider than the box joint annular groove, This mechanical joint is configured so that shim insertion openings are provided at three or more locations at approximately equal intervals around the circumferential direction of the box joint, so that the entire width of the annular groove of the pin joint, which is set wide, can be seen when the insertion is complete, and so that shims can be inserted through the shim insertion openings into the gap between the annular groove of the pin joint and the C-ring member.

2. A method for joining steel pipes each having the mechanical joint according to claim 1 provided at an end of the steel pipe, This is a method of joining steel pipes, in which after the pin joint has been completely inserted into the box joint, a C-ring member is placed so as to straddle the box joint and the pin joint, and then the angle of the upper steel pipe is adjusted so that it is facing vertically.After that, a shim is inserted from the shim insertion opening into the gap between the wide annular groove and the C-ring member, thereby fixing the angle of the upper steel pipe relative to the lower steel pipe.

3. 3. The method for joining steel pipes according to claim 2, further comprising the step of: placing a plate member covering the shim insertion opening after inserting the shim.

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