Land improvement machine

Abstract

To provide a ground improvement machine equipped with a device for preventing co-rotation of a swivel joint which is excellent in assemblability and can be used safely.SOLUTION: A rod 32 constituting an anti-rotation device 31 comprises a short large diameter pipe 34 fixed to one side of an auger 17, a long small diameter pipe 35 slidably provided coaxially therewith, a temporary holding portion 36 that creates a temporary holding state in which a center of gravity of the small diameter pipe is positioned below the large diameter pipe, and a fixed portion that creates a fixed state where the center of gravity of the small diameter pipe is located above the large diameter pipe. The temporary holding portion has a link rod 41 inserted into the large diameter pipe, and an abutment member 42 fixed to an upper end of the link rod and abutting an upper opening end 34b of the large diameter pipe to retain the link rod. The link rod has a protruding portion 43 that protrudes downward from a lower opening end 34a of the large diameter pipe in the abutting state of the abutting member. A locking pin 40 can be inserted into and removed from a pin hole provided in an overlapping portion of the protruding portion and a tip portion 39 of the small diameter pipe.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a soil improvement machine, and more particularly to a soil improvement machine that improves the soil by stirring and mixing excavated soil and injected soil improvement agent. [Background technology]

[0002] In building and civil engineering projects, soil improvement machines are used to improve soft ground by injecting and stirring soil improvement agents such as cement milk into excavated holes to harden the ground. This type of soil improvement machine has a soil improvement agent injection hose (grout hose) connected via a swivel joint to the upper end of a hollow drilling shaft (screw shaft), and a drilling head with drilling blades and stirring blades attached to the lower end. The rotating screw shaft is lowered along the leader to excavate the ground, and the soil improvement agent is sent through the screw shaft and sprayed out from the drilling head, stirring the soil and soil improvement agent.

[0003] Due to its mounting structure, a swivel joint, which is a rotary joint, may cause the body side to rotate along with the shaft due to the resistance of the seal portion built between the coupling (shaft side) and the body (hose side). To prevent this type of co-rotation of the swivel joint, the soil improvement machine is equipped with an extension rod attached to the rotary drive device and a connecting member that connects the extension rod to the swivel joint. The connecting member is configured to rotatably hold the swivel joint coupling while also holding the connected injection hose. This prevents the body side of the swivel joint from rotating in a fixed position, preventing co-rotation caused by the rotating screw shaft (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-203659 Summary of the Invention [Problem to be solved by the invention]

[0005] The telescopic rod that constitutes the anti-corotation means has a telescopic structure in which multiple pipes are inserted in sequence. To ensure the amount of extension and contraction required for such a structure to accommodate a long screw shaft, the pipe diameters become thinner starting from the fixed pipe, resulting in a larger overall amount of deflection. On the other hand, if the pipes are not connected to each other and are made into a single long pipe, the overall rigidity increases and the problem of deflection is resolved. However, a configuration using a long pipe requires a crane with a lifting height suitable for installation and removal work, and high-altitude scaffolding for handling the sling rope, which poses problems of reduced work efficiency and safety.

[0006] Therefore, an object of the present invention is to provide a ground improvement machine equipped with a device for preventing co-rotation of a swivel joint, which is easy to assemble and can be used safely. [Means for solving the problem]

[0007] In order to achieve the above object, the ground improvement machine of the present invention comprises a base machine having an upper rotating body rotatably mounted on the top of a lower traveling body, a leader erected at the front of the upper rotating body, a rotation drive device that moves up and down along the leader, a screw shaft attached to the rotation drive device, and a swivel joint that is provided at the upper end of the screw shaft and to which a soil improvement agent injection hose is connected, and a rod is provided in the rotation drive device parallel to the screw shaft, and the rod and the swivel joint are connected by a connecting member. In this soil improvement machine, the rod is connected to a short large diameter pipe fixed to one side of the rotation drive device and a sliding member that is coaxial with the large diameter pipe. The apparatus comprises a movably mounted long small-diameter pipe, a temporary holding part that creates a temporary holding state in which the center of gravity of the small-diameter pipe is located below the large-diameter pipe, and a fixing part that creates a fixed state in which the center of gravity of the small-diameter pipe is located above the large-diameter pipe, the temporary holding part having a link rod inserted into the large-diameter pipe and a contact member that is fixed to the upper end of the link rod and contacts the upper open end of the large-diameter pipe to prevent the link rod from slipping out downward, the link rod having a protruding part that protrudes downward beyond the lower open end of the large-diameter pipe when in contact with the contact member, and a locking pin is formed in a locking pin insertion hole that is provided at the overlapping part between the protruding part and the tip end of the small-diameter pipe so that a locking pin can be inserted and removed The locking pin insertion hole is formed to extend across both longitudinal ends of the link rod, and is an elongated hole through which the locking pin slides to cause the link rod to appear and disappear at the tip end of the small diameter pipe. It is characterized by the following.

[0008] The fixing portion is characterized in that a fixing pin is formed so as to be insertable and detachable into a fixing pin insertion hole provided in the overlapping portion of the large diameter pipe and the small diameter pipe. 。 [Effects of the Invention]

[0009] According to the soil improvement machine of the present invention, the rod constituting the drag prevention means comprises a short large-diameter pipe secured to the rotary drive unit, a long small-diameter pipe slidably mounted coaxially thereon, and a temporary holding section and a fixed section that function according to the relative vertical positions of the two pipes. Therefore, simply using an assembly jig consisting of a link rod and abutment member as the temporary holding section, the rod can be attached and detached from below the rotary drive unit, eliminating the need for crane or high-altitude work. In other words, the jig can be attached to the large-diameter pipe and the locking pin inserted and removed from the small-diameter pipe from the ground. After setup, the simple act of raising the rotary drive unit and lifting the small-diameter pipe creates a temporary holding state in which the two pipes are coaxially aligned. Furthermore, when the rotary drive unit is lowered from the temporary holding state, the small-diameter pipe is inserted into the large-diameter pipe independently, and the center of gravity is shifted upward in a stable state, allowing for a safe and rapid fixation. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a side view showing a state in which a rod is temporarily held in a soil improvement machine according to an embodiment of the present invention. FIG. [Figure 2] This is also a front view. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] 6 is a cross-sectional view taken along the line VI-VI in FIG. 5. [Figure 7] FIG. [Figure 8] FIG. [Figure 9] FIG. 10 is a diagram showing a state in which the small diameter pipe is placed on a base. [Figure 10] 10 is a diagram showing a state in which the upper end of the small diameter pipe is inserted into the large diameter pipe. FIG. [Figure 11] FIG. 10 is a diagram showing a fixed state of the fixing portion. [Figure 12] FIG. 10 is a diagram showing the state in which the first screw shaft is connected. [Figure 13] FIG. 10 is a diagram showing the state in which the screw shaft has been re-gripped. [Figure 14] FIG. 10 is a diagram showing the state in which the second screw shaft is connected. DETAILED DESCRIPTION OF THE INVENTION

[0011] Figures 1 to 14 show an example of a soil improvement machine of the present invention. As shown in Figures 1 and 2, the soil improvement machine 11 includes a base machine 14 made up of a lower traveling body 12 equipped with crawlers and an upper rotating body 13 rotatably mounted on the lower traveling body 12, a leader 15 erected at the front of the upper rotating body 13, a hoisting cylinder 16 supporting the leader 15 from the rear, and an auger 17, which is a rotary drive device mounted on the leader 15 so as to be able to rise and fall.

[0012] A leader support 18 that supports the leader 15 so that it can be raised and lowered is provided at the front of the upper rotating body 13. A driver's cab 19 is provided on the right side of the upper rotating body 13, and an equipment room 20 that houses equipment such as an engine and a hydraulic pump is provided on the left side. Stabilizing jacks 21 are provided at four locations on the front, rear, left and right of the upper rotating body 13, and a counterweight 22 for balancing the soil improvement machine 11 is mounted at the rear end of the upper rotating body 13.

[0013] The leader 15 is made up of multiple leader members connected together, each with a cross section formed into a square tube, and is rotatably attached to a support shaft provided on the leader support 18. The upper end of the leader 15 is provided with a top sheave 23 around which a hanging rope is wound, and the front lower part is provided with an anti-vibration device 24 that prevents the swing of the rotationally driven construction member. In the center of the front face of the leader 15, a rack gear 25 is provided as a component of a rack and pinion type lifting device, and a pair of left and right guide pipes 26, 26 are provided continuously over the entire length of the leader 15 at the front ends of both sides.

[0014] The auger 17 is equipped with a chuck mechanism 17b that grips the workpiece that has passed through the gear case 17a, and an auger drive hydraulic motor 17c that applies a rotational driving force to the workpiece.A pair of left and right guide gibs 17d, 17d that slide against the guide pipes 26, 26 are provided protruding rearward, and a pair of left and right pinions (not shown) that mesh with the rack gear 25 are rotationally driven by an auger lifting hydraulic motor 17e, thereby causing the auger to rise and fall along the front of the leader 15.

[0015] When performing ground improvement using the soil improvement machine 11, a screw shaft is used as a construction member. The screw shaft 27 is a hollow tube that can be extended and through which a soil improvement agent such as cement milk passes. As shown in Figure 13, the screw shaft 27 is provided with square shaft portions 27b with chuck grooves 27a that engage with the chuck mechanism 17b at multiple locations along its length, including the upper shaft 28 at its upper end. A drilling head (not shown) with a drilling blade and agitating blades is attached to the lower end. Also, as shown in Figure 4, a swivel joint 29 is attached to the upper end of the upper shaft 28, and an injection hose (grout hose) 30 is connected to the swivel joint 29.

[0016] Swivel joint 29 is assembled so that coupling 29a, which connects to upper shaft 28, and body 29b, to which injection hose 30 is connected, are rotatable relative to each other, so that even when screw shaft 27 rotates, the rotational force is not transmitted to injection hose 30. However, because a leak-proof seal is interposed between coupling 29a and body 29b, there is a risk that body 29b will rotate together due to the resistance of this seal. Therefore, anti-rotation device 31 is used to prevent swivel joint 29 from rotating together.

[0017] The rotation prevention device 31 has a rod 32 provided on the auger 17 that is parallel to the screw shaft 27 , and the rod 32 and the swivel joint 29 are connected by a connecting member 33 .

[0018] 3 to 8, the rod 32 includes a short large-diameter pipe 34 fixed to one side of the auger 17 (the side of the gear case 17a), a long small-diameter pipe 35 slidably disposed coaxially with the large-diameter pipe 34, a temporary holding portion 36 for creating a temporary holding state (FIG. 1) in which the center of gravity of the small-diameter pipe 35 is located below the large-diameter pipe 34, and a fixing portion 37 for creating a fixed state (FIG. 11) in which the center of gravity of the small-diameter pipe 35 is located above the large-diameter pipe 34. The temporary holding portion 36 and the fixing portion 37 are selected and used as needed in accordance with the progress of the assembly work of the rod 32.

[0019] 3 and 4, the large-diameter pipe 34 is formed slightly shorter than the overall height of the auger 17, and when bolted via a flat mounting portion 38, the height position of the lower open end 34a is aligned with the underside of the gear case 17a. The small-diameter pipe 35 is formed long to accommodate the long specifications of the screw shaft 27, and is, for example, about eight times longer than the large-diameter pipe 34, allowing it to slide smoothly within the large-diameter pipe 34. The tip (upper end) of the small-diameter pipe 35 is formed as a connecting structure that also serves as reinforcement, and is provided with a bifurcated portion 39 that is pin-connected to the temporary holding portion 36. The bifurcated portion 39 is provided with a circular locking pin insertion hole 39a through which a locking pin 40 can be inserted and removed.

[0020] The temporary holding portion 36 is lightweight and can be handled manually as an assembly jig for the rod 32, and includes a link rod 41 to be inserted into the large diameter pipe 34, and a contact member 42 fixed to the upper end of the link rod 41 and contacting the upper open end 34b of the large diameter pipe 34 to prevent the link rod 41 from slipping out downward. The contact member 42 is a circular plate formed slightly larger than the outer diameter of the large diameter pipe 34.

[0021] The link rod 41 is formed from a square timber with a rectangular cross section, is slightly longer than the large diameter pipe 34, and has a slot-shaped locking pin insertion hole 41a extending across both longitudinal ends. The lower end of the link rod 41 forms a protruding part 43 that protrudes downward from the lower open end 34a of the large diameter pipe 34 when the abutting member 42 abuts against the upper open end 34b of the large diameter pipe 34, and the locking pin 40 can be inserted into and removed from the overlapping part formed by inserting this protruding part 43 into the bifurcated part 39 (Figs. 5 to 7).

[0022] When the small diameter pipe 35 is locked to the link rod 41 via the locking pin 40, the weight of the small diameter pipe 35 acts on the link rod 41. As will be described in detail later, when the tip end (forked portion 39) of the small diameter pipe 35 is inserted into the large diameter pipe 34, the load on the link rod 41 is removed, and at the same time, the locking pin 40 slides toward the top of the elongated hole (locking pin insertion hole 41a). As a result, the link rod 41 moves from a position protruding outside the small diameter pipe 35 (imaginary line in FIG. 8) to a position retracted inside the small diameter pipe 35 through an opening 39b provided in the forked portion 39. In other words, the link rod 41 can move in and out of the tip end of the small diameter pipe 35 by following the relative axial (vertical) movement of the two pipes 34, 35.

[0023] The fixing portion 37 determines the vertical position of the small diameter pipe 35 relative to the large diameter pipe 34, making the rod 32 usable. As shown in Figures 3 and 11, fixing pin insertion holes 34c and 35a are provided at the overlapping portion of the large diameter pipe 34 and the small diameter pipe 35, and a fixing pin 44 can be inserted and removed when the positions of both holes are aligned. The fixing pin insertion holes 34c and 35a are provided so as to coincide when the lower ends of both pipes 34 and 35 are aligned. This ensures both the installation height of the small diameter pipe 35 and the insertion amount (overlap amount) relative to the large diameter pipe 34.

[0024] Connecting member 33 is composed mainly of arm body 33a that is bridged between rod 32 and swivel joint 29, and has guide tube 33b with an inner diameter that allows large-diameter pipe 34 to be inserted therethrough, retaining tube 33c that holds the coupling 29a side of swivel joint 29 via a bearing mechanism, and hose guide 33d that holds injection hose 30, with rod 32 inserted into guide tube 33b so as to be movable in the axial direction. As a result, with injection hose 30 connected, the body 29b side of swivel joint 29 is held non-rotatably in a fixed position, and will not rotate along with the rotating screw shaft 27.

[0025] The following describes the procedure for performing ground improvement using the thus formed soil improvement machine 11 with a screw shaft 27 that is longer than the leader 15. First, when the soil improvement machine 11 is moved to the site, the auger 17 is placed at the lower end of the leader 15, and the top of the leader 15 is tilted down and the machine is placed on the bed of a trailer in a transport position. At this time, only the upper shaft 28 is attached to the auger 17, and the anti-rotation device 31 is held in a provisionally assembled state with the connecting member 33 spanning between the swivel joint 29 and the large diameter pipe 34.

[0026] After the soil improvement machine 11 is delivered to the construction site, it raises the leader 15 to allow the auger 17 to ascend and descend. Then, as shown in FIG. 3, it inserts the prepared link rod 41 into the large-diameter pipe 34, and lifts the tip (forked portion 39) of the small-diameter pipe 35 off the ground, connecting it to the lower end (protruding portion 43) of the link rod 41 with the locking pin 40. This applies tension to the link rod 41, i.e., the necessary steps for assembling the rod 32 are completed, and the temporary holding portion 36 is ready to perform its function. When the auger 17 is raised, the small-diameter pipe 35 slides along the ground, pivots around the locking pin 40, and is raised. Finally, it becomes parallel to the upper shaft 28 and is suspended below the large-diameter pipe 34, i.e., a temporary holding state is established (FIG. 1).

[0027] 9 to 11, the procedure from the temporary holding state will be described. First, the base 45 is set in position to match the small diameter pipe 35. Next, as shown in FIG. 9, the auger 17 is lowered to place the small diameter pipe 35 on the base 45. From this state, the auger 17 is gradually lowered, and the upper end of the small diameter pipe 35 is inserted into the large diameter pipe 34, as shown in FIG. 10. At this time, the link rod 41 is held in the large diameter pipe 34 without the weight of the small diameter pipe 35, and is retracted into the small diameter pipe 35 while moving the locking pin 40 from the lower end to the upper end of the elongated hole. When the upper end of the small diameter pipe 35 is fully inserted into the large diameter pipe 34, the locking pin 40 abuts against the upper end of the elongated hole (solid line in FIG. 8). After sinking into the tip of the small diameter pipe 35, the link rod 41 moves vertically away from the large diameter pipe 34 while maintaining its retracted state.

[0028] On the other hand, the center of gravity of the small diameter pipe 35 (the middle position in the longitudinal direction) moves from below to above the large diameter pipe 34, but the small diameter pipe 35 maintains an upright state by obtaining an overlapping amount in the longitudinal direction with the large diameter pipe 34. Then, as shown in Figure 11, the lower ends of both pipes 34, 35 are aligned, and then the pin holes in the overlapping portion are aligned and the small diameter pipe 35 is connected by the fixing pin 44. When the anti-rotation device 31 is assembled in this manner, the fixing portion 37 functions to extend the small diameter pipe 35 as far as possible above the large diameter pipe 34, i.e., the small diameter pipe 35 is fixed.

[0029] Here, the assembly work of the screw shaft 27 will be explained with reference to Figures 12 to 14. In this work, the lifting rope equipped on the soil improvement machine 11 is used, and a separate aerial work vehicle is prepared to secure the foothold. These operation procedures are performed using conventional procedures. First, the injection hose 30 is connected to the swivel joint 29, and the auger 17 is raised. After that, as shown in Figure 12, the first screw shaft 27 is hung directly below the auger 17 using the lifting rope hanging from the top sheave 23, and connected to the upper shaft 28.

[0030] After disengaging from the screw shaft 27 through a predetermined operation, the auger 17 is lowered below the leader 15 to perform re-gripping, gripping the lower angular shaft portion of the screw shaft 27. At this time, while the auger 17 is lowered, the height of the connecting member 33 holding the swivel joint 29 does not change, so the guide tube 33b of the connecting member 33 moves from the outer periphery of the large-diameter pipe 34 to the outer periphery of the small-diameter pipe 35, and finally moves to the upper end of the small-diameter pipe 35, as shown in Figure 13. Then, after gripping the lower angular shaft portion of the screw shaft 27, the auger 17 is raised again, and as shown in Figure 14, a second screw shaft 27 is connected to the lower end of the first screw shaft 27, and an excavation head is attached to the lower end of that, thereby completing the assembly work of the screw shaft 27.

[0031] After assembling the screw shaft 27 in this manner, it is held by the vibration control device 24, and the auger 17 is operated to rotate the screw shaft 27 while lowering it along the leader 15, and the soil improvement agent sent through the pipeline is sprayed from the tip of the drilling head into the drilled hole, so that the soil excavated by the drilling blade is mixed with the soil improvement agent by the mixing blade.

[0032] After the auger 17 is lowered to the bottom of the leader 15, the auger 17, which has released its grip on the middle angular shaft portion, is raised to grip the upper angular shaft portion. At this time, the screw shaft 27 is gripped by the fixing means of the anti-vibration device 24 to fix the screw shaft 27 in that position. When the engagement with the screw shaft 27 is released and the auger 17 is raised, the height of the connecting member 33 holding the swivel joint 29 does not change, so the guide tube 33b of the connecting member 33 moves to the bottom of the small diameter pipe 35 and finally to the large diameter pipe 34.

[0033] After the auger 17 has been moved to switch the gripping position of the screw shaft 27 to the upper side, the screw shaft 27 is lowered while being rotated, and the soil excavated by the excavation blade of the excavation head is mixed with the soil improvement agent by the mixing blade. After the excavation head has been lowered to the specified depth, the excavation head is pulled out in the reverse order, completing the ground improvement work.

[0034] Thus, according to the ground improvement machine 11 of the present invention, the rod 32 constituting the anti-rotation device 31 includes a short large-diameter pipe 34 fixed to the rotary drive device 17, a long small-diameter pipe 35 that can slide coaxially thereon, and a temporary holding portion 36 and a fixing portion 37 that function according to the relative vertical positions of the two pipes 34, 35. Therefore, by simply using an assembly jig consisting of a link rod 41 and an abutment member 42 as the temporary holding portion 36, the rod 32 can be attached and detached from the bottom of the rotary drive device 17, eliminating the need for crane work or work at height. In other words, the jig can be placed on the large-diameter pipe 34 and the locking pin 40 inserted and detached between the large-diameter pipe 34 and the small-diameter pipe 35 can be done from the ground, and after setup, the simple operation of raising the rotary drive device 17 and lifting the small-diameter pipe 35 creates a temporary holding state in which the two pipes 34, 35 are coaxially aligned. Furthermore, when the rotary drive device 17 is lowered from the temporary holding state, the small diameter pipe 35 stands upright and is inserted into the large diameter pipe 34, and the center of gravity moves upward to the large diameter pipe 34 in a stable state, so that the fixed state can be created safely and quickly.

[0035] Furthermore, since the fixing portion 37 has a pin connection structure using the overlapping portion of both pipes 34, 35, the fixed state can be achieved with a simple configuration, contributing to improved ease of assembly. Furthermore, the locking pin insertion hole 41a provided in the link rod 41 is an elongated hole through which the locking pin 40 slides to cause the link rod 41 to appear and disappear at the tip end (bifurcated portion 39) of the small diameter pipe 35, so that in the fixed state, the link rod 41 can be prevented from protruding or tipping over relative to the small diameter pipe 35, thereby achieving a configuration for the temporary holding portion 36 that is practical as an assembly jig.

[0036] The present invention is not limited to the above-described embodiment, and the length of the small diameter pipe of the rod can be changed as appropriate depending on the specifications of the screw shaft, and when a longer rod is required, the length of the large diameter pipe may be extended to the extent that does not impair transportability or assembly. Furthermore, various configurations can be considered for the temporary holding portion and the fixing portion that allow stable movement of the center of gravity of the small diameter pipe, thereby widening the range of applications in the various environments in which the soil improvement machine is used. [Explanation of symbols]

[0037] 11...ground improvement machine, 12...lower running body, 13...upper rotating body, 14...base machine, 15...leader, 16...derailing cylinder, 17...auger, 17a...gear case, 17b...chuck mechanism, 17c...hydraulic motor for driving auger, 17d...guide gib, 17e...hydraulic motor for lifting auger, 18...leader support, 19...operator's cab, 20...equipment room, 21...jack, 22...counterweight, 23...top sheave, 24...anti-vibration device, 25...rack gear, 26...guide pipe, 27...screw shaft, 27a...chuck groove, 27b...square shaft portion, 28...upper shaft, 29...swivel joy vent, 29a...coupling, 29b...body, 30...injection hose, 31...anti-rotation device, 32...rod, 33...connecting member, 33a...arm body, 33b...guide tube, 33c...holding tube, 33d...hose guide, 34...large diameter pipe, 34a...lower opening end, 34b...upper opening end, 34c...fixing pin insertion hole, 35...small diameter pipe, 35a...fixing pin insertion hole, 36...temporary holding portion, 37...fixing portion, 38...mounting portion, 39...bifurcated portion, 39a...locking pin insertion hole, 39b...opening, 40...locking pin, 41...link rod, 41a...locking pin insertion hole, 42...abutting member, 43...protrusion, 44...fixing pin, 45...base

Claims

1. A soil improvement machine comprising: a base machine having a rotatable upper rotating body mounted on the top of a lower running body; a leader erected at the front of the upper rotating body; a rotary drive device that moves up and down along the leader; a screw shaft attached to the rotary drive device; and a swivel joint provided at the upper end of the screw shaft to which a soil improvement agent injection hose is connected; a rod provided in parallel with the screw shaft on the rotary drive device; and a connecting member connecting the rod and the swivel joint. the rod comprises a short large-diameter pipe fixed to one side of the rotation drive device, a long small-diameter pipe slidably provided coaxially with the large-diameter pipe, a temporary holding part that creates a temporary holding state in which the center of gravity of the small-diameter pipe is located below the large-diameter pipe, and a fixing part that creates a fixed state in which the center of gravity of the small-diameter pipe is located above the large-diameter pipe, the temporary holding portion includes a link rod inserted into the large diameter pipe, and a contact member fixed to the upper end of the link rod and contacting the upper open end of the large diameter pipe to prevent the link rod from slipping out downward, the link rod has a protruding portion that protrudes downward from the lower open end of the large diameter pipe when the abutting member is in contact with the link rod, and a locking pin is inserted into and removed from a locking pin insertion hole provided at an overlapping portion between the protruding portion and the tip end of the small diameter pipe, A ground improvement machine characterized in that the locking pin insertion hole is formed extending over both longitudinal ends of the link rod and is a long hole through which the locking pin slides to cause the link rod to appear and disappear at the tip of the small diameter pipe.

2. 2. The soil improvement machine according to claim 1, wherein the fixing portion is formed so that a fixing pin can be inserted and removed into a fixing pin insertion hole provided in the overlapping portion of the large diameter pipe and the small diameter pipe.

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