Mechanical joints for steel pipe piles

Abstract

In a construction method in which an excavation device having a bit configured to expand and contract its outer diameter is inserted into a steel pipe pile, and the steel pipe pile is inserted into the excavation hole at the same time as the ground is excavated by the excavation device, a configuration is provided that can improve workability. [Solution] The mechanical joint 10 includes a cylindrical box joint 11 attached to the end of a steel pipe 2, with a box-side keyway portion 11c extending in the circumferential direction formed on its inner surface; a cylindrical pin joint 12 attached to the end of another steel pipe 2, with a portion of it positioned radially inward relative to the box joint 11 when combined with the box joint 11, and with a pin-side keyway portion extending in the circumferential direction formed on its outer surface; and a load-transmitting key 13 arranged to straddle the box-side keyway portion and the pin-side keyway portion. The inner diameter of the pin joint 12 is larger than the outer diameter of the bit 102 in its reduced diameter state. The outer diameter of the box joint 11 is equivalent to the outer diameter of the bit 102 in its expanded diameter state.

Description

Technical Field

[0001] The present invention relates to a mechanical joint of a steel pipe pile used in a construction method in which an excavation device having a bit configured to be able to expand and contract its outer diameter is inserted into the steel pipe pile, and the steel pipe pile is inserted into an excavation hole while excavating the ground by the excavation device.

Background Art

[0002] A construction method is known in which an excavation device having a bit configured to be able to expand and contract its outer diameter is inserted into a steel pipe pile, and the steel pipe pile is inserted into an excavation hole while excavating the ground by the excavation device. As such a construction method, for example, Patent Document 1 discloses a tubular pile driving method in which a down-the-hole hammer is used as the excavation device to drive a tubular pile fitted around the outer periphery of the excavation device into the ground while excavating.

[0003] In the construction method disclosed in Patent Document 1, when driving a tubular pile using an excavation device longer than the tubular pile to be driven, the excavation shaft member of the excavation device is inserted into the pipe, and a rotary drive device is provided above the excavation shaft member, and a bit portion of an expandable down-the-hole hammer protrudes outside the pipe below the excavation shaft member. The excavation device is suspended by a crane facility, and the tubular pile is supported by a tubular pile holding device installed on a structure fixed to the ground.

[0004] The bit portion of the expandable down-the-hole hammer is configured to be displaceable (i.e., expandable and contractible) between an expanded state and a contracted state. When the bit portion is in the contracted state, the bit portion can be freely inserted and removed with respect to the tubular pile. In the expanded state, the bit portion projects outward, and the turning locus of its outer end is configured to exceed the outer diameter of the tubular pile.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] By the way, as in Patent Document 1, when the bit portion of an expanding-diameter down-the-hole hammer protrudes outside the pipe from the lower part of the drilling shaft member inserted into the pipe of a tubular pile, and the tubular pile is inserted into the resulting excavation hole, a gap may occur between the excavation hole and the tubular pile. If such a gap occurs, the tubular pile may tilt or become misaligned.

[0007] As described above, if the tubular pile tilts or becomes misaligned, the enlarged-diameter down-the-hole hammer will tilt relative to the ground, reducing the drilling capacity of the drilling device and thus reducing workability.

[0008] In contrast, in a construction method in which an excavation device having a bit configured to expand and contract its outer diameter is inserted into a steel pipe pile, and the steel pipe pile is inserted into the excavation hole at the same time as the ground is excavated by the excavation device, there is a need for a configuration that can improve constructability.

[0009] The object of the present invention is to provide a configuration that can improve workability in a construction method in which an excavation device having a bit configured to be expandable and contractible in outer diameter is inserted into a steel pipe pile, and the steel pipe pile is inserted into the excavation hole at the same time as the ground is excavated by the excavation device. [Means for solving the problem]

[0010] As a result of diligent study, the inventors have conceived of using a mechanical joint for steel pipe piles in order to improve the constructability of the above-mentioned construction method. Specifically, the mechanical joint for steel pipe piles has a joint structure in which the axial joint portion and the cylindrical joint portion are joined by inserting a key member so as to engage with the axial-side key groove provided in the axial joint portion and the cylindrical-side key groove provided in the cylindrical joint portion, as disclosed in, for example, Japanese Patent Publication No. 5623923. This joins the axial joint portion and the cylindrical joint portion, which are fixed to the tip of one of the two steel pipes and into which the axial joint portion is inserted and fitted. Therefore, at the joint portion of the mechanical joint, the axial joint portion is inserted and fitted into the cylindrical joint portion, and it is necessary to insert a key member so as to engage with the key groove provided in each of the key grooves, resulting in a larger outer diameter at the joint portion compared to a general steel pipe.

[0011] From this perspective, the inventors conceived that by excavating a hole the same size as the outer diameter of the joint portion of the mechanical coupling, it would be possible to reduce the likelihood of tilting or misalignment of the steel pipe pile within the excavation hole. The configuration conceived by the inventors will be described below.

[0012] A configuration according to one embodiment of the present invention is a mechanical joint for a steel pipe pile used in a construction method in which an excavation device having a bit configured to expand and contract in outer diameter is inserted into a steel pipe pile, and the steel pipe pile is inserted into the excavation hole along with the excavation of the ground by the excavation device. This mechanical joint has a cylindrical box joint attached to the end of a first steel pipe and having a box side groove portion extending in the circumferential direction formed on its inner surface, a cylindrical pin joint attached to the end of a second steel pipe pile connected to the end of the first steel pipe, a part of which is located radially inward relative to the box joint when combined with the box joint and having a pin side groove portion extending in the circumferential direction formed on its outer surface, and a key arranged between the box joint and the pin joint so as to straddle the box side groove portion and the pin side groove portion. The inner diameter of the pin joint is larger than the outer diameter of the bit in the contracted state. The outer diameter of the box joint is the same as the outer diameter of the bit in the expanded state (first configuration).

[0013] As a result, the reduced-diameter bit can pass inside the pin joint located radially inward in the mechanical joint of the steel pipe pile. Furthermore, when the bit is expanded to have an outer diameter equivalent to the outer diameter of the mechanical joint of the steel pipe pile, it can excavate a hole having a diameter equivalent to the outer diameter of the box joint. Therefore, the steel pipe pile can pass through a hole having a diameter equivalent to the outer diameter of the box joint located radially outward in the mechanical joint.

[0014] Therefore, with the above configuration, the drilling device bit can move inside the steel pipe pile and drill a borehole through which the steel pipe pile can pass. Moreover, since the diameter of the borehole drilled by the drilling device bit is equal to the outer diameter of the mechanical joint of the steel pipe pile, it is possible to suppress tilting or misalignment of the steel pipe pile within the borehole.

[0015] As a result, the constructability of installing the steel pipe piles can be improved compared to conventional methods. [Effects of the Invention]

[0016] A mechanical joint for a steel pipe pile according to one embodiment of the present invention comprises: a cylindrical box joint attached to the end of a first steel pipe, having a box-shaped groove extending in the circumferential direction on its inner surface; a cylindrical pin joint attached to the end of a second steel pipe pile connected to the end of the first steel pipe, having a portion of which is radially inward relative to the box joint when combined with the box joint, and having a pin-shaped groove extending in the circumferential direction on its outer surface; and a key positioned between the box joint and the pin joint so as to straddle the box-shaped groove and the pin-shaped groove. The inner diameter of the pin joint is larger than the outer diameter of the bit in its reduced diameter state. The outer diameter of the box joint is equal to the outer diameter of the bit in its expanded diameter state.

[0017] As a result, the bit of the excavation device can move inside the steel pipe pile, and can excavate an excavation hole through which the steel pipe pile can pass. Moreover, since the diameter of the excavation hole excavated by the bit of the excavation device is equivalent to the outer diameter of the mechanical joint of the steel pipe pile, it is possible to suppress the steel pipe pile from tilting or experiencing core deviation within the hole. Therefore, compared with the conventional construction method, the workability when installing the steel pipe pile can be improved.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a view showing a state in which an excavation device penetrates a steel pipe pile having a mechanical joint according to Embodiment 1. [Figure 2] FIG. 2 is a cross-sectional view showing a lower part of a steel pipe pile in a cross-section along the axis. [Figure 3] FIG. 3 is an enlarged cross-sectional view showing a mechanical joint. [Figure 4] FIG. 4 is a view showing the expanded diameter state of the bit as seen in the axial direction. [Figure 5] FIG. 5 is a view showing the reduced diameter state of the bit as seen in the axial direction. [Figure 6] FIG. 6 is a flowchart showing a method for installing a steel pipe pile. [Figure 7] FIG. 7 is a view schematically showing a method for installing a steel pipe pile. [[ID=??]]

Embodiments for Carrying Out the Invention

[0019] Hereinafter, each embodiment will be described with reference to the drawings. In each figure, the same parts are denoted by the same reference numerals, and the description of the same parts will not be repeated. Note that the dimensions of the constituent members in each figure do not faithfully represent the actual dimensions of the constituent members and the dimensional ratios of the constituent members.

[0020] In the following description, the axial direction means the direction in which the axis P of the steel pipe pile 1 extends. The radial direction means the direction orthogonal to the axis P of the steel pipe pile 1, that is, the radial direction of the steel pipe pile 1. The circumferential direction means the direction along an arc centered on the axis P of the steel pipe pile 1. It seems there is a small error in the provided text where the "

発明を実施するための形態

Embodiments for Carrying Out the Invention

[0021] (Steel pipe pile) FIG. 1 is a view showing a state in which an excavation device 100 penetrates a steel pipe pile 1 having a mechanical joint 10 according to an embodiment of the present invention. The steel pipe pile 1 is an annular member extending along an axis P. The steel pipe pile 1 is used, for example, in foundation pile work such as bridge foundations, port structures, river structures, building structures, and earth retaining walls. In FIG. 1, the excavation device 100 axially penetrates the inside of the steel pipe pile 1.

[0022] FIG. 2 is a cross-sectional view showing a lower portion of the steel pipe pile 1 along the axis P. The steel pipe pile 1 includes a plurality of steel pipes 2 axially connected by a mechanical joint 10. The steel pipe 2 is a cylindrical metal member. One axial end of the steel pipe 2 is connected to a box joint 11 that forms part of the mechanical joint 10, and the other axial end is connected to a pin joint 12 that forms part of the mechanical joint 10. In the example shown in FIG. 2, a box joint 11 is connected to the lower end of the upper steel pipe 2 (first steel pipe), and a pin joint 12 is connected to the upper end of the lower steel pipe 2 (second steel pipe). The steel pipes 2 are connected by connecting the box joint 11 and the pin joint 12.

[0023] Note that the steel pipe 2 and the box joint 11 may be joined by welding or may be joined by a mechanical configuration. Similarly, the steel pipe 2 and the pin joint 12 may be joined by welding or may be joined by a mechanical configuration.

[0024] (Mechanical joint) FIG. 3 is an enlarged cross-sectional view showing the mechanical joint 10. The mechanical joint 10 includes a box joint 11, a pin joint 12, a load transmission key 13 (key), and an insertion fixing bolt 14.

[0025] The box joint 11 has a cylindrical outer peripheral projection 11a, an inner peripheral receiving portion 11b, a box-side keyway portion 11c (box-side groove portion), and a screw hole 11d. The inner peripheral receiving portion 11b is provided on the inner circumference of the base end side (upper side in Figure 3) of the outer peripheral projection 11a. The box-side keyway portion 11c extending in the circumferential direction is provided on the inner circumference side of the outer peripheral projection 11a. The outer peripheral projection 11a is provided with a screw hole 11d that penetrates radially so as to connect to the box-side keyway portion 11c.

[0026] The inner circumferential support portion 11b is provided so as to face the inner circumferential projection portion 12a of the pin joint 12, which will be described later, when the pin joint 12 is assembled with the box joint 11. When the mechanical joint 10 is subjected to a force in the axial compression direction, the inner circumferential support portion 11b contacts the inner circumferential projection portion 12a of the pin joint 12 and receives a portion of the force.

[0027] Furthermore, the inner circumferential receiving portion 11b has a groove on its outer circumference that extends in the circumferential direction, into which a portion of the inner circumferential projection 12a of the pin joint 12 is inserted. This prevents the box joint 11 and the pin joint 12 from shifting radially.

[0028] The pin joint 12 has a cylindrical inner circumferential projection 12a, an outer circumferential receiving portion 12b, and a pin-side keyway portion 12c (pin-side groove portion). The outer circumferential receiving portion 12b is provided on the outer circumference of the base end side (lower side in Figure 3) of the inner circumferential projection 12a. The pin-side keyway portion 12c extending in the circumferential direction is provided on the outer circumference side of the inner circumferential projection 12a.

[0029] The outer peripheral support portion 12b is provided so as to face the outer peripheral projection 11a of the box joint 11 when the pin joint 12 is assembled with the box joint 11. When the mechanical joint 10 is subjected to a force in the axial compression direction, the outer peripheral support portion 12b contacts the outer peripheral projection 11a of the box joint 11 and receives a portion of the force.

[0030] Furthermore, the outer peripheral receiving portion 12b has a groove on its inner peripheral side that extends in the circumferential direction, into which a portion of the outer peripheral projection 11a of the box joint 11 is inserted. This prevents the box joint 11 and the pin joint 12 from shifting radially.

[0031] The load-transmitting key 13 is located within the box-side keyway 11c of the box joint 11 and within the pin-side keyway 12c of the pin joint 12 when the steel pipes 2 are joined together by the mechanical joint 10. The load-transmitting key 13 is pressed against the bottom surface of the pin-side keyway 12c by an insertion fixing bolt 14 that is screwed into the threaded hole 11d of the box joint 11. This allows the load-transmitting key 13 to be positioned within the pin-side keyway 12c and the box-side keyway 11c, and when a force is applied to the mechanical joint 10 in the axial tensile direction, the load-transmitting key 13 can receive the force. In other words, the load-transmitting key 13 has a radial dimension that is greater than the depth of the pin-side keyway 12c.

[0032] When joining the box joint 11 and the pin joint 12, the load transmission key 13 is housed within the box-side keyway portion 11c of the box joint 11, and the box joint 11 and the pin joint 12 are then assembled. Therefore, the box-side keyway portion 11c has a depth greater than the radial dimension of the load transmission key 13. Subsequently, by screwing the insertion fixing bolt 14 into the screw hole 11d of the box joint 11, the insertion fixing bolt 14 moves the load transmission key 13 into the pin-side keyway portion 12c of the pin joint 12 and presses it against the bottom surface of the pin-side keyway portion 12c.

[0033] As shown in Figure 3, in the mechanical joint 10, the amount L1 of the radial protrusion of the inner surface of the pin joint 12 relative to the inner surface of the steel pipe 2 is smaller than the amount L2 of the radial protrusion of the outer surface of the box joint 11 relative to the outer surface of the steel pipe 2. Furthermore, the amount L1 of the radial protrusion of the inner surface of the pin joint 12 relative to the inner surface of the steel pipe 2 is smaller than the pipe thickness T of the steel pipe 2. The inner circumferential protrusion 12a and the outer circumferential protrusion 11a each have tapered portions 11e and 12e at their axial ends. Moreover, when viewed in a cross-section of the mechanical joint 10 cut in the axial direction, the inclination angle α of the tapered portion 12e of the inner circumferential protrusion 12a relative to the inner surface of the steel pipe 2 is smaller than the inclination angle β of the tapered portion 11e of the outer circumferential protrusion 11a relative to the outer surface of the steel pipe 2. With these configurations, when the drilling device 100 is moved axially within the steel pipe pile 1, the drilling device 100 is less likely to interfere with the mechanical joint 10. Therefore, the excavation device 100 can be easily moved axially within the steel pipe pile 1.

[0034] The thickness t2 of the outer circumferential projection 11a of the box joint 11 where the box-side keyway 11c is provided, and the thickness t3 of the inner circumferential projection 12a of the pin joint 12 where the pin-side keyway 12c is provided, are both smaller than the radial thickness t1 of the load-transmitting key 13. This makes it possible to reduce the thickness of the outer circumferential projection 11a of the box joint 11 and the inner circumferential projection 12a of the pin joint 12, thereby reducing the radial thickness of the mechanical joint 10. Thus, a joint structure can be realized in which the excavation device 100 can move easily inside the mechanical joint 10.

[0035] (Drilling equipment) Next, the configuration of the drilling device 100, which is inserted into the steel pipe pile 1 having the configuration described above, will be explained. The drilling device 100 is a device equipped with a so-called down-the-hole hammer, which uses compressed air to cause a piston inside the hammer to move back and forth, thereby crushing the ground with the resulting impact force.

[0036] More specifically, the drilling device 100 has a columnar body 101 that can penetrate the steel pipe pile 1, and a bit 102 provided at its tip.

[0037] The columnar body 101, although not specifically shown, houses a hammer, piston, motor, etc., inside its casing. A bit 102 is provided at the tip of the columnar body 101. The detailed configuration of the columnar body 101 is the same as in the conventional design, so a detailed explanation is omitted.

[0038] The bit 102 is configured to transmit the impact force from the hammer inside the columnar body 101, and is also configured to be rotatable around its axis by a motor. Therefore, the bit 102 crushes the ground with the impact force of the hammer and scrapes out the crushed ground by rotating with the motor.

[0039] Figure 4 shows the bit 102 in its expanded state, viewed in the axial direction. Figure 5 shows the bit 102 in its reduced state, viewed in the axial direction. As shown in Figures 4 and 5, the bit 102 has a plurality of bit movement parts 103.

[0040] The multiple bit moving parts 103 move such that one side moves radially inward (in the direction of the solid arrow shown in Figure 4) and the other side protrudes radially outward as the bit 102 rotates in one direction (in the direction of the white arrow shown in Figure 4) around the axis P by the motor. As a result, the multiple bit moving parts 103 are in the state where they are located radially outward (hereinafter referred to as the expanded diameter state of the bit 102).

[0041] Meanwhile, the multiple bit movement units 103 move such that one side moves radially outward (in the direction of the solid arrow shown in Figure 5) and the other side is housed radially inward as the bit 102 rotates in the opposite direction (in the direction of the white arrow shown in Figure 5) by the motor. As a result, the multiple bit movement units 103 are in their most radially inward position (hereinafter referred to as the reduced diameter state of the bit 102).

[0042] Thus, the multiple bit movement units 103 are configured to move radially by the rotation of the bit 102. The movement mechanism of the multiple bit movement units 103 is the same as in the conventional design, so a detailed explanation is omitted.

[0043] As shown in Figure 2, in the reduced diameter state of bit 102 (dashed line in Figure 2), the outer diameter of bit 102 is smaller than the inner diameter of the mechanical joint 10 of the steel pipe pile 1. That is, the inner diameter of the pin joint 12 of the mechanical joint 10 is larger than the outer diameter of bit 102 in the reduced diameter state. On the other hand, in the expanded diameter state of bit 102 (solid line in Figure 2), the outer diameter of bit 102 is equivalent to the outer diameter of the mechanical joint 10 of the steel pipe pile 1. That is, the outer diameter of the box joint 11 of the mechanical joint 10 is equivalent to the outer diameter of bit 102 in the expanded diameter state.

[0044] Furthermore, the statement that the outer diameter of bit 102 is equivalent to the outer diameter of mechanical joint 10 or box joint 11 includes cases where it is the same as the outer diameter of mechanical joint 10 or box joint 11, or where it is larger than the outer diameter of mechanical joint 10 or box joint 11 to the extent that the steel pipe pile 1 does not tilt or become misaligned.

[0045] (Method for installing steel pipe piles) Next, a method for excavating the ground using the excavation device 100 having the above-described configuration and installing the steel pipe pile 1 will be explained. Figure 6 is a flowchart showing the method for installing the steel pipe pile 1. Figure 7 is a schematic diagram showing the method for installing the steel pipe pile 1.

[0046] When the flowchart shown in Figure 6 starts (START), first, as shown in Figure 7(a), the drilling device 100 is inserted into the steel pipe pile 1 (Step SA1). Although not specifically shown, the drilling device 100 is suspended by a crane or the like. Next, as shown in Figure 7(b), with the bit 102 of the drilling device 100 protruding from the axial end of the steel pipe pile 1, the bit 102 is rotated in one direction around its axis to expand its diameter (Step SA2). The outer diameter of the expanded bit 102 is larger than the outer diameter of the steel pipe 2 of the steel pipe pile 1, and is equivalent to the outer diameter of the mechanical joint 10 (outer diameter of the box joint 11) of the steel pipe pile 1.

[0047] Subsequently, in step SA3, as shown in Figures 7(c) and (d), the ground is excavated by the enlarged bit 102 of the drilling device 100. The excavated hole H obtained by the drilling of bit 102 has a diameter equivalent to the outer diameter of the mechanical joint 10 of the steel pipe pile 1. Therefore, the steel pipe pile 1 does not tilt or become misaligned within the excavated hole H.

[0048] In step SA3, the axial length of the steel pipe pile 1 may be increased by connecting the steel pipe 2 axially to the steel pipe pile 1, depending on the depth of the excavation hole H. Alternatively, the ground may be excavated using the excavation device 100, and the steel pipe pile 1 may be driven into the ground at the same time.

[0049] After the drilling of the ground is completed by the bit 102 of the drilling device 100, in step SA4, as shown in Figure 7(e), the bit 102 is rotated in the opposite direction around its axis to reduce its diameter. The outer diameter of the bit 102 in the reduced diameter state is smaller than the inner diameter of the mechanical joint 10 of the steel pipe pile 1 (the inner diameter of the pin joint 12).

[0050] Subsequently, as shown in Figure 7(f), the drilling device 100 is withdrawn axially from the steel pipe pile 1 (step SA5). At this time, as described above, the outer diameter of the reduced-diameter bit 102 is smaller than the inner diameter of the mechanical joint 10 of the steel pipe pile 1, so the bit 102 can move smoothly axially inside the steel pipe pile 1. After the drilling device 100 is withdrawn axially from the steel pipe pile 1, this flow is terminated (END).

[0051] The mechanical joint 10 of the steel pipe pile 1 in this embodiment is used in a construction method in which an excavation device 100 having a bit 102 configured to expand and contract its outer diameter is inserted into the steel pipe pile 1, and the steel pipe pile 1 is inserted into the excavation hole at the same time as the ground is excavated by the excavation device 100. The mechanical joint 10 of the steel pipe pile 1 in this embodiment is used in a construction method in which an excavation device 100 having a bit 102 configured to expand and contract its outer diameter is inserted into the steel pipe pile 1, and the steel pipe pile 1 is inserted into the excavation hole at the same time as the ground is excavated by the excavation device 100. The mechanical joint 10 of the steel pipe pile 1 in this embodiment is used in a construction method in which an excavation device 100 having a bit 102 configured to expand and contract its outer diameter is inserted into the steel pipe pile 1 The outer diameter of the box fitting 11 is equivalent to the outer diameter of the bit 102 in its expanded state.

[0052] As a result, the reduced-diameter bit 102 can pass inside the pin joint 12 located radially inward in the mechanical joint 10 of the steel pipe pile 1. Furthermore, when the bit 102 expands to an outer diameter equivalent to the outer diameter of the mechanical joint 10 of the steel pipe pile 1, it can excavate a hole having a diameter equivalent to the outer diameter of the box joint 11. Therefore, the steel pipe pile 1 can pass through an excavated hole having a diameter equivalent to the outer diameter of the box joint 11 located radially outward in the mechanical joint 10.

[0053] Therefore, with the above configuration, the bit 102 of the drilling device 100 can move inside the steel pipe pile 1 and drill a borehole through which the steel pipe pile 1 can pass. Moreover, since the diameter of the borehole drilled by the bit 102 of the drilling device 100 is equal to the outer diameter of the mechanical joint 10 of the steel pipe pile 1, it is possible to suppress tilting or misalignment of the steel pipe pile 1 within the borehole.

[0054] As a result, the constructability of installing the steel pipe pile 1 can be improved compared to conventional methods.

[0055] [Other embodiments] Although embodiments of the present invention have been described above, the embodiments described above are merely examples for carrying out the present invention. Therefore, the invention is not limited to the embodiments described above, and it is possible to carry out the invention by appropriately modifying the embodiments described above without departing from the spirit of the invention.

[0056] In the above embodiment, the multiple bit moving parts 103 in the bit 102 of the drilling device 100 switch between an expanded diameter state and a contracted diameter state by moving radially through rotation around the axis of the bit 102. However, the configuration in which the drilling device's bit switches between an expanded diameter state and a contracted diameter state is not limited to the configuration in the above embodiment. That is, the bit may have any configuration as long as the outer diameter of the bit can be switched. [Industrial applicability]

[0057] The present invention can be used in a construction method in which an excavation device having a bit configured to expand and contract in outer diameter is inserted into a steel pipe pile, and the steel pipe pile is inserted into the excavation hole at the same time as the ground is excavated by the excavation device. [Explanation of Symbols]

[0058] 1 steel pipe pile 2 Steel pipe 10 Mechanical couplings 11 Box fittings 11a Outer protrusion 11b Inner circumference receiving portion 11c Box side keyway 11d screw hole 12-pin fitting 12a Inner protrusion 12b Outer circumference receiving part 12c Pin-side keyway 13. Load transmission key (key) 14 Insertion fixing bolts 100 drilling equipment 101 Column 102-bit 103-bit movement section H Excavation hole P axis

Claims

[Claim 1] A mechanical joint for a steel pipe pile used in a construction method in which an excavation device having a bit configured to expand and contract its outer diameter is inserted into the steel pipe pile, and the steel pipe pile is inserted into the excavation hole at the same time as the ground is excavated by the excavation device, A cylindrical box joint is attached to the end of the first steel pipe, and has a box-shaped side groove portion extending in the circumferential direction formed on its inner surface, A cylindrical pin joint is attached to the end of a second steel pipe connected to the end of the first steel pipe, and when combined with the box joint, a portion of it is positioned radially inward relative to the box joint, and a pin side groove portion extending in the circumferential direction is formed on its outer surface, Between the box joint and the pin joint, a key is provided, which is positioned to straddle the box side groove and the pin side groove. It has, The inner diameter of the pin joint is larger than the outer diameter of the bit in its reduced diameter state. The outer diameter of the box joint is equivalent to the outer diameter of the bit in its expanded state. Mechanical joint for steel pipe piles.

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