JP7481947B2 - Casing removal device and removal method - Google Patents

Description

The present invention relates to a casing extraction device and extraction method suitable for extracting casings buried horizontally or diagonally, and relates to a technology that is effective for use in extracting casings buried in platforms during reinforcement work for embankment platforms, for example.

One type of station platform structure is an embankment-type station platform, where the embankment is supported by masonry walls made of stacked stone blocks. Some existing embankment-type station platforms have been built many years ago and no longer meet recent earthquake resistance standards. There is concern that such embankment-type station platforms will collapse due to external forces in the event of a large earthquake, causing the collapse of stacked stones and the collapse of the embankment.
Therefore, the applicant developed a technology to reinforce the platform of an earth-filled station by burying cylindrical reinforcing bodies made of mortar, etc., in the embankment. Specifically, holes are drilled diagonally from the stone wall of the platform embankment, steel pipes are inserted into the holes, casing is performed, mortar or grout is injected, and the holes are allowed to harden to form cylindrical reinforcing bodies in the embankment.

Incidentally, in the above-mentioned reinforcement, the surface of the steel pipe that becomes the casing is smooth, so the strength can be increased by pulling out the steel pipe and having the mortar or grout reinforcement come into contact with the embankment, rather than leaving the steel pipe in. However, since a large force is required to pull out the casing, a casing pull-out device is required.
Conventionally, devices for extracting a casing buried underground are known from Patent Documents 1 and 2.

Japanese Utility Model Application Publication No. 61-125548 Japanese Patent Application Laid-Open No. 9-111763 Japanese Utility Model Application Publication No. 61-155496

However, the casing extraction devices described in Patent Documents 1 and 2 are both equipped with a means for gripping or locking the end of the steel pipe that serves as the casing and a hydraulic cylinder, and the device is installed on the ground surface and pulled out vertically, so there is a problem that it cannot extract casings that are buried horizontally or diagonally.
Also, Patent Document 3 describes an invention related to a device that presses in and pulls out a casing tube at an angle to the ground. However, the device described in Patent Document 3 requires the use of large heavy machinery, and therefore has a problem in that it is difficult to apply when working in places where rails are laid on the sides, such as in the embankment of a station platform, making it difficult to secure sufficient working space.

The present invention has been made in light of the above-mentioned problems, and its object is to provide a casing extraction device and extraction method capable of extracting a casing buried horizontally or obliquely.
Another object of the present invention is to provide a casing extraction device and an extraction method that enable work to be performed in locations where it is difficult to secure a working space.

In order to achieve the above object, the present invention relates to
A casing extraction device comprising: a fixed frame unit having a base plate for mounting the device to a work object; an extraction unit held by the fixed frame unit, the extraction unit having gripping means for gripping a part of a casing inserted into the ground and a pressure type expansion and contraction means for moving the gripping means; and a stopper unit held by the fixed frame unit, the stopper unit having a pressing means inserted into an inlet of the casing for pressing down a filling material in the casing,
an end of the extraction unit is rotatably coupled to the base plate by a hinge structure;
the pressing means comprises a pressing bar held by the fixed frame unit, and a pressing member provided at a tip of the pressing bar and capable of being fitted into an inlet of the casing,
The presser bar is arranged to pass through the gripping means of the pulling unit.

According to the casing extraction device having the above-mentioned configuration, the end of the extraction unit is rotatably connected to the base plate that is joined to the work object by a hinge structure, so that the extraction unit can be tilted at any angle with respect to the base plate, and the casing buried horizontally or diagonally can be extracted. In addition, since it is equipped with a pressure rod having a pressure member at its tip that can be fitted into the entrance of the casing, the casing can be extracted by the extraction unit while the filling inside the casing is being pressed down by the pressure rod. Furthermore, since the device is compact and can be assembled and disassembled, it can be used in places where it is difficult to secure work space, such as the embankment of a station platform.

Here, preferably, the pressure type expansion and contraction means is a hydraulic jack,
At least a pair of support pieces each having an axial hole is provided on the base plate so as to protrude substantially parallel to a surface of the base plate opposite to a surface of the base plate that is to be joined to an object;
A connecting member having a shaft hole is provided at an end of the hydraulic jack,
The hinge structure is configured by a pin shaft inserted through the shaft holes formed in the pair of support pieces and the shaft hole formed in the connecting member.

With the above configuration, the hydraulic jack can be easily connected to the base plate and tilted at any angle by aligning the shaft hole of the connecting member at the end of the hydraulic jack with the shaft hole of the support piece provided on the base plate and inserting the pin shaft. In this specification, "approximately parallel" includes a state close to parallel.

Also, preferably, the extraction unit has two hydraulic jacks arranged substantially in parallel, and the gripping means is provided on a support plate that is horizontally disposed between the cylinders of the two hydraulic jacks.
According to this configuration, the extraction unit is equipped with two hydraulic jacks that are approximately parallel to each other, and a gripping means is provided between the two hydraulic jacks for grasping and holding the ends of the casing, so that the force of the hydraulic jacks can be applied evenly to the casing, thereby enabling the casing to be smoothly pulled out.

Further, preferably, the fixed frame unit includes a pair of connecting bars connected to the base plate, and a reaction plate horizontally disposed between the other ends of the connecting bars,
The retaining unit includes a connecting ring that is connected to an end of the casing to be removed,
The presser bar has a square thread formed on its outer periphery,
A nut is fixed to the reaction plate, into which the square screw of the presser bar can be screwed.
The connecting ring is provided with a cylindrical guide member through which the presser bar is inserted so as to be movable in the axial direction,
The gripping means is configured with a chuck that grips and holds the outer periphery of the casing.

With the above configuration, when the casing is pulled out, the reaction plate prevents the axial movement of the pressure bar, preventing the pressure member at the tip of the pressure bar from coming out of the casing and ensuring that the filling is held down. In addition, the connecting ring is provided with a cylindrical guide member through which the pressure bar is inserted, allowing the connecting ring to be guided along the pressure bar by the guide member, stabilizing the movement of the movable part of the pulling unit.

Another invention related to this application is
A casing extraction method using an extraction device equipped with a gripping means for gripping a part of a casing inserted into the ground and a pressure type expansion and contraction means for moving the gripping means, comprising:
The filling material inside the casing is pressed down by a pressing member that can be inserted into the entrance portion of the casing, while the pressure-type expansion means is operated to move the casing grasped by the gripping means and pull it out from the ground.
This method prevents the walls of the drilled hole from collapsing and being crushed when the casing is pulled out, thereby allowing the shape of the reinforcement body to be buried in the ground to be accurately maintained and ensuring the strength of the reinforcement body.

The casing extraction device and extraction method of the present invention make it possible to extract casings buried horizontally or diagonally. It also has the advantage of being able to work in places where it is difficult to secure working space, such as in the embankments of station platforms.

(A) is a cross-sectional view showing the cross-sectional structure of a station platform embankment as an example of a structure equipped with a reinforcing body that requires casing removal work, and (B) is a cross-sectional view showing the cross-sectional structure of the reinforcing body constructed within the embankment before the casing is removed. 1 is a plan view showing one embodiment of a casing extracting device constituting a casing extracting device according to the present invention. FIG. 1 is a side view showing a configuration of a casing puller according to an embodiment of the present invention; FIG. 2 is a plan view showing a state in which a hydraulic jack of the casing extraction device of the embodiment is operated. 13 is an enlarged perspective view showing the configuration of a presser at the tip of a presser bar that constitutes the fall-off prevention unit and a connecting ring that is attached to the end of a casing. FIG. 1A is a front view showing a specific example of a base plate, and FIG. 1B is a side view showing the base plate installed on a masonry wall. 1A to 1I are diagrams showing the steps of a method for constructing a diagonal reinforcement body in a station platform embankment and a method for extracting a casing using a casing extraction device of an embodiment.

Hereinafter, an embodiment of the casing extraction device according to the present invention will be described in detail with reference to the drawings. Before describing the casing extraction device of this embodiment, however, a brief description will be given of the structure and reinforcement example of an embankment-type station platform with reference to FIG. 1.
As shown in FIG. 1(A), an embankment-type station platform 10 has a structure in which an inner embankment 13 is supported by a masonry wall 12 consisting of a number of masonry blocks 11 stacked to form a vertical plane. In order to reinforce an existing embankment having such a structure, a cylindrical reinforcing body 20 made of solidified self-hardening filler such as mortar or grout (hereinafter simply referred to as filler) is buried in the soil of the embankment.

In order to enhance the reinforcing effect, the reinforcing member 20 is usually provided with an inclination so that the tip is lower. Also, as shown in Fig. 1 (B), the reinforcing member 20 has a structure in which a reinforcing bar or the like with a diameter of just under 20 mm is inserted as a core material 22 in the center of a cylindrical filling material 21 with a diameter of about 150 mm.
The reinforcement 20 of this structure is constructed by inserting a steel pipe 23 as a casing while drilling the embankment of the station platform 10, inserting a core material 22 in the center, injecting the filler material 21, and then pulling out the steel pipe 23 and allowing it to solidify. The steel pipe is inserted because there is a large earth pressure inside the embankment, and this earth pressure is required to prevent the wall around the hole from collapsing and being crushed during drilling.

It should be noted that the steel pipe 23 is not a long one, but rather a short one is used and inserted while drilling the hole. A male thread is formed on the outer periphery of one end of the short steel pipe to be used, and a female thread is formed on the inner periphery of the other end. The steel pipe to be added is rotated to screw the male or female thread of the end into the female or male thread of the end of the steel pipe already buried, thereby connecting the steel pipes.

Next, an embodiment of a casing extractor according to the present invention will be described.
2 to 5 show one embodiment of the casing extraction device according to the present invention, in which FIG. 2 is a plan view of the casing extraction device constituting the casing extraction device, FIG. 3 is a side view of the casing extraction device (connecting bar 132a omitted), FIG. 4 is a plan view showing the hydraulic jack of the casing extraction device in an extended state, and FIG. 5 is a perspective view showing the structure of the connecting ring that is connected to the core material holder at the tip of the pressure bar and the end of the steel pipe serving as the casing.

As shown in Figures 2 and 3, the casing extraction device 100 of this embodiment includes an extraction unit 110 for grasping and extracting the end of a steel pipe 23 serving as a casing inserted into a hole formed in the soil of the embankment, a retaining unit 120 for preventing the filling material and core material from leaking or coming out of the steel pipe 23 when the steel pipe 23 is extracted, and a fixing frame unit 130 for fixing the device to the side of the masonry block 11 while holding the extraction unit 110 and the retaining unit 120 together.

Of the units, the fixed frame unit 130 comprises a base plate 131 that is joined and fixed to the side of the masonry block 11, a pair of connecting bars 132a, 132b that are rotatably connected at one end to a pair of outer support pieces 131a, 131b provided on both side edges of the base plate 131, and a reaction plate 133 that is connected at both ends to the other ends of the connecting bars 132a, 132b and spans the other end. As a result, the fixed frame unit 130 is configured as a frame body that is approximately rectangular in top view. The connecting bars 132a, 132b and the reaction plate 133 are detachably connected by pins 134a, 134b.

As shown in FIG. 6(A), the base plate 131 has a U-shaped opening 131c in the center and bolt insertion holes 131d on both sides of the opening 131c. The base plate 131 is fixed to the side of the masonry block 11 by inserting an embedded bolt that has been fixed in advance to the side of the masonry block 11 through the bolt insertion holes 131d and screwing and tightening the nut.

2, a pair of inner support pieces 135a, 135b are fixed to the base plate 131 substantially parallel to the pair of outer support pieces 131a, 131b. Axial holes are formed in the outer support pieces 131a, 131b and the inner support pieces 135a, 135b, respectively, and pin shafts 136a, 136b can be inserted so as to straddle the outer support pieces 131a, 131b and the inner support pieces 135a, 135b. Axial holes through which the pin shafts 136a, 136b are inserted are formed in the ends of the connecting bars 132a, 132b, and the connecting bars 132a, 132b are connected to the base plate 131 by the pin shafts 136a, 136b.

The extraction unit 110 includes a pair of connecting blocks 111a, 111b that have shaft holes through which the pin shafts 136a, 136b can be inserted and are rotatably connected to the pin shafts 136a, 136b, and a pair of hydraulic jacks 112a, 112b whose piston rods are connected to the connecting blocks 111a, 111b. This allows the hydraulic jacks 112a, 112b to rotate around the pin shafts 136a, 136b, changing the angle, i.e., the inclination angle, relative to the base plate 131.

A support plate 114, both ends of which are joined by fixing plates 113a, 113b, is mounted across the cylinders of the hydraulic jacks 112a, 112b. A circular ring 115 is fixed to the center of the support plate 114, and a chuck 116 is attached to grasp and hold the outer periphery of the end of the steel pipe 23 serving as the casing.
Note that Figure 2 shows the hydraulic jacks 112a, 112b in a contracted state. When the hydraulic jacks 112a, 112b are extended, as shown in Figure 4, the chuck 116 moves to the left while gripping the outer periphery of the end of the steel pipe 23, and the steel pipe 23 is pulled out by the stroke of the jack. By repeating this process, the chuck 116 is loosened and the jack is contracted, and then the chuck 116 is again gripped around the outer periphery of the steel pipe 23 and the jack is extended, the entire casing can be pulled out.

The chuck 116 is comprised of an outer chuck 116a which is cylindrical and has an inner diameter slightly larger than the outer diameter of the steel pipe to be drawn and a thickness that decreases toward the tip (left in the figure) and which is formed integrally with the pressure ring 115, and an inner chuck 116b which is cylindrical and has an inner diameter approximately the same as the outer diameter of the steel pipe to be drawn and a thickness that decreases toward the tip (right in the figure) and which can be fitted inside the outer chuck 116a.

The outer chuck 116a has a tapered inner surface, and the inner chuck 116b has a tapered outer surface that contacts each other. The cylindrical inner chuck 116b has an axial slit. When the outer chuck 116a is pushed by the support plate 114 and moved to the left in the figure, the inner chuck 116b enters the inside of the outer chuck 116a like a wedge. Then, the inner chuck 116b has an axial slit, so its diameter becomes smaller and it can enter further inside the outer chuck 116a and firmly grip the outer periphery of the end of the steel pipe. It is recommended that the inner surface of the inner chuck 116b be knurled (with non-slip grooves) to increase friction.

The retaining unit 120 has a presser bar 121 that can be screwed into a hexagonal nut 137 fixed to the center of the reaction plate 133 that constitutes the fixed frame unit 130, a cylindrical connecting ring 122 that can be connected to the end of a steel pipe as a casing, and a core material holder 123 provided at the tip of the presser bar 121 (the right end in the figure). The connecting ring 122 has a female thread formed on its inner circumferential surface, and is connected to the end of the steel pipe by screwing this female thread into the male thread on the outer periphery of the end of the steel pipe 23. Since the presser bar 121 is screwed into the hexagonal nut 137, when the presser bar 121 is rotated, it moves in the axial direction relative to the reaction plate 133, thereby moving the core material holder 123 at the tip.

The connecting ring 122 has a cylindrical guide portion 122a in the center that guides the pressure bar 121 in the axial direction, and the guide portion 122a is connected to the main body of the connecting ring 122 by radially arranged connecting portions 122b as shown in Fig. 6. An insertion hole having a diameter substantially the same as the outer diameter of the pressure bar 121 is formed in the guide portion 122a, and since no female thread is formed on the inner circumference of this insertion hole, even if the connecting ring 122 having the guide portion 122a is connected to a steel pipe, the pressure bar 121 can move freely in the axial direction within the guide portion 122a.

The core material presser 123 has a recess in the center that can engage with the end of the core material 22 that constitutes the reinforcing body 20. As shown in FIG. 5, the core material presser 123 also has radially arranged presser pieces 123a that contact the filling material 21 of the reinforcing body 20. Although not shown, the presser pieces 123a are attached to the tip of the presser bar 121 so that they can rotate freely and will not fall off. Therefore, even if the presser bar 121 is rotated, the core material presser 123 does not rotate with the presser bar 121. In other words, the presser bar 121 can be rotated and moved with the core material presser 123 in contact with the core material 22 and filling material 21 of the reinforcing body 20, and the core material presser 123 can be firmly pressed against the core material 22.

The presser bar 121 has a hexagonal hole formed in the end face at its rear end (the end on the left side in FIG. 2). When a hexagonal wrench is inserted into this hexagonal hole and turned, the male thread slides along the female thread of the hexagonal nut 137, generating a reaction force that allows the presser bar 121 to move in the axial direction. The male thread on the outer periphery of the presser bar 121 is formed as a square thread. This allows the presser bar 121 to receive the axial load firmly when a pressing force is applied from the core material presser 123 and transmit the load firmly to the reaction plate 133.

Next, a method for constructing a diagonal reinforcement body in a station platform embankment and a method for extracting a casing using the casing extraction device 100 having the above-mentioned configuration will be described with reference to FIG.
When constructing a reinforcing body diagonally from the masonry wall 12 to the embankment, first determine the position and inclination angle θ of the reinforcing body to be constructed. Next, as shown in Fig. 7(a), set a core machine 200 for drilling holes at a predetermined position of the masonry wall 12 so as to obtain the above-mentioned angle θ. Next, operate the core machine 200 to insert a short steel pipe that will become the casing while drilling holes in the masonry wall 12 as shown in Fig. 7(b).

After that, as shown in Fig. 7(c), drilling is continued while adding short steel pipes to the embankment (10) as casings. When connecting the next steel pipe to the one already inserted, excavation is performed inside the steel pipe tube as shown in Fig. 7(d). Then, as shown in Fig. 7(e), the above drilling and excavation are repeated until the desired depth is reached.
Next, the core machine 200 is removed, and the core material 22 is inserted into the steel tube as shown in Fig. 7(f). Spacers 24 are provided at the front and rear ends and at the middle of the core material 22 to be inserted in order to hold the core material 22 in the center of the hole being drilled. As the spacer 24, one having radial pressing pieces 123a can be used, similar to the core material pressing member 123 provided at the tip of the pressing bar 121 shown in Fig. 4.

Then, as shown in Fig. 7(g), a filler such as mortar is injected into the steel tube to fill it. Next, as shown in Fig. 7(h), the base plate 131 is installed on the side of the masonry wall 12, and the extraction device 100 of the above embodiment is set at a predetermined position on the masonry wall 12 at a predetermined angle θ. Then, the steel tube is extracted while the core material holder 123 prevents the core material 22 from falling out and the filler from leaking.
When setting the extraction device 100 on the masonry wall 12, first, as shown in Figure 6 (B), the base plate 131 is installed on the side of the masonry wall 12 so that the axial holes H of the outer support pieces 131a, 131b and the inner support pieces 135a, 135b provided on the base plate 131 are on the extension line of the center line C of the reinforcing body (drilling) B having an inclination angle θ.

A pin shaft which serves as the rotation axis of the pulling unit 110 is inserted into the above-mentioned axial hole H. By making the axial hole H lie on an extension of the center line C of the reinforcement body (hole drilling) B, when the pulling unit 110 is later set on the base plate 131 and tilted by angle θ around the pin shaft, the center line of the reinforcement body (hole drilling) H will be aligned with the center line of the base plate 131, and when pulling out the steel tube from the hole drilling, a pulling force can be applied accurately in the direction of angle θ to pull it out.
Once the steel tube has been extracted, as shown in Figure 7(i), the extraction device 100 and base plate 131 are removed from the masonry wall 12, and additional filler material is injected to make up for the amount of sinking caused by the extraction. The surface of the filler material at the mouth is then finished, completing the series of operations.

According to the casing extraction device and extraction method of the above embodiment, the core material and filler material inside the casing (steel tube) are pressed while the outer periphery of the steel tube is grasped with a chuck and the hydraulic jack is operated to extract the casing, which prevents the core material from falling out and the filler material from leaking when the casing is extracted.

Furthermore, in the casing extraction device of the above embodiment, the extraction unit 110 is rotatably attached to the base plate 131 installed on the side of the stone wall by pin shafts 136a, 136b, and the load during extraction is borne by the reaction plate 133 of the fixed frame unit 130, so that the casing buried at an angle can be extracted without using heavy machinery, etc.
Furthermore, since the pull-out unit 110, the retaining unit 120, and the fixed frame unit 130 are configured to be separable from one another, there is an advantage that they are easy to carry and can be easily assembled and disassembled in the narrow working space on the tracks next to the station platform.

Although the invention made by the inventor has been specifically described above based on the embodiment, the present invention is not limited to the above embodiment. For example, in the above embodiment, the core material presser 123 at the tip of the presser bar 121 is provided with radially arranged presser pieces 123a, but it is also possible to use a core material presser 123 made of a circular plate having a notch or small hole for injecting a filler.
In the above embodiment, the presser bar 121 is configured to double as a guide rod when the pulling unit 110 moves, but it is also possible to configure the guide rod of the pulling unit 110 to be provided separately from the presser bar 121. However, by configuring the presser bar 121 to double as a guide rod, it is possible to make the device more compact.

In addition, in the above embodiment, a hydraulic jack is used as the pressure-type extension means for moving the gripping means (chuck), but it is also possible to use a water hydraulic jack or other liquid-operated jack, or a mechanical jack such as a screw jack, rack-driven jack, or screw jack, or an air-operated jack known as an air jack.
Furthermore, in the above embodiment, an example has been described in which the invention is applied to pulling out a casing when constructing a cylindrical reinforcing body for reinforcing the embankment of a station platform at an angle from the side of a masonry wall, but the invention is not limited to this and can also be used when using a casing to construct a reinforcing body or other structure at an angle to the ground.

REFERENCE SIGNS LIST 10 Station platform embankment 11 Stone block 12 Stone wall 13 Embankment 20 Reinforcement body 21 Filling material 22 Core material 100 Casing extraction device 110 Extraction unit 111a, 111b Connecting block (connecting member)
112a, 112b Hydraulic jack 115 Press ring 116a Outer chuck 116b Inner chuck 120 Anti-slip unit 121 Presser bar 122 Connecting ring 123 Core material holder 130 Fixed frame unit 131a, 131b Support piece 132a, 132b Connecting bar 133 Reaction plate 135a, 135b Support piece 136a, 136b Pin shaft

Claims (5)

A casing extraction device comprising: a fixed frame unit having a base plate for mounting the device to a work object; an extraction unit held by the fixed frame unit, the extraction unit having a gripping means for gripping a part of a casing inserted into the ground and a pressure type expansion and contraction means for moving the gripping means; and a stopper unit held by the fixed frame unit, the stopper unit having a pressing means inserted into an inlet of the casing for pressing down a filling material in the casing,
The pressure type expansion and contraction means is a pair of jacks having a cylinder and a piston rod and arranged parallel to each other at a predetermined distance,
The fixed frame unit includes a reaction plate arranged parallel to the base plate, and a pair of connecting bars arranged parallel to the base plate at a predetermined interval in order to connect the reaction plate, one end of which is connected to the base plate and the other end of which is connected to the base plate, to the base plate;
At least a pair of support pieces each having an axial hole is provided on the base plate so as to protrude substantially parallel from a surface of the base plate opposite to a surface that is joined to an object, and a connecting member having an axial hole whose axis is in the same direction as the axial holes of the pair of support pieces is provided on an end of the piston rod of the jack;
The pair of connecting bars have ends on the side where the base plate is located that are provided with axial holes having the same axis as the axial holes of the pair of support pieces,
A hinge structure is formed by pin shafts inserted into the shaft holes provided in the pair of support pieces, the shaft holes provided in the connecting member, and the shaft holes provided in the pair of connecting bars, and the hinge structure connects the pull-out unit and the fixed frame unit to the base plate so as to be rotatable in a direction perpendicular to the arrangement direction of the pair of jacks ,
The extraction unit includes a support plate that fixes the cylinders of the pair of jacks at a predetermined distance from each other in a state where both are facing the casing extraction direction, and a ring-shaped press ring that is fixed to the center of the support plate and through which the casing to be extracted can be inserted,
the gripping means comprises a cylindrical outer chuck integral with the press ring, and an inner chuck having an inner diameter larger than the outer diameter of the casing to be pulled out, a cylindrical shape that becomes thinner toward its tip, a slit in the axial direction, and fitted inside the outer chuck, and when the pair of jacks are operated, the outer chuck moves together with the support plate in the pulling direction, thereby narrowing the diameter of the inner chuck and enabling it to grip the end of the casing to be pulled out,
The support plate and the base plate each have a through hole formed therein such that their centers are aligned on the same axis,
the pressing means includes a pressing bar held by the fixed frame unit, and a pressing member provided at a tip of the pressing bar and capable of being fitted into an inlet of the casing,
A male screw is formed on the outer periphery of the presser bar,
A nut into which the male screw of the presser bar can be screwed is fixed to the reaction plate,
A casing puller according to claim 1, wherein the pressure bar is disposed so as to pass through the through holes formed in the support plate and the base plate. 2. The casing puller according to claim 1, wherein the male thread formed on the outer periphery of the presser bar is a square thread, and the nut has an inner periphery formed with a female thread having a shape into which the square thread can be screwed . The present invention provides a method for extracting a casing by using a casing having a cylindrical connecting ring that is connected to an end of the casing to be extracted.
the connecting ring is provided with a guide portion having a through hole through which the presser bar is inserted so as to be movable in the axial direction, and a connecting portion disposed in a radial direction and connecting the guide portion to a cylindrical main body of the connecting ring,
3. A casing puller according to claim 1, wherein an inner circumferential surface of the body of the connecting ring is provided with a female thread that can be screwed into a male thread formed on an outer circumferential surface of the end of the casing . a pair of outer support pieces having a shaft hole through which the pin shaft can be inserted are provided on an edge portion of the base plate that is outer than the pair of support pieces;
A casing puller as described in any one of claims 1 to 3, characterized in that the pin shaft is inserted through the pair of support pieces, the pair of outer support pieces, the axial hole of the connecting member, and the axial hole of the pair of connecting bars . A casing extraction method using the casing extraction device according to any one of claims 1 to 4 ,
A casing extraction method comprising the steps of: installing the casing extraction device so that the base plate is in contact with the surface of the embankment or masonry wall in which the casing to be extracted is buried and the end of the casing to be extracted is inserted into the annular push ring; gripping the end of the casing with the gripping means; inserting the pressing member into the entrance portion of the casing; and, while pressing down on the filling inside the casing with the pressing member, operating the pressure-type expansion and contraction means to move the casing gripped by the gripping means and extract it from the ground.

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