Hollow steel pipe and method for extracting existing structure using the same

Abstract

To provide a drawing-out method that prevents soil from being deposited or stuck on the inside of a hollow steel pipe upon edge-cutting between an existing structure buried in the ground such as an existing pile and its surrounding ground.SOLUTION: A hollow steel pipe 10 comprises a deposition prevention mechanism 40 removing deposited soil on an inner peripheral wall 10i and backfill material. The deposition prevention mechanism 40 may include a co-rotation prevention mechanism 42. The co-rotation prevention mechanism 42 may be provided with apertures 43 arranged along an outer peripheral wall 10o of the hollow steel pipe 10 and a protruding body 44 passing through the apertures 43 from the inside to the outside of the hollow steel pipe 10.SELECTED DRAWING: Figure 12A

Description

[Technical Field]

[0001] The present invention relates to a hollow steel pipe and a method for extracting the hollow steel pipe from an existing structure. [Background technology]

[0002] For example, when an existing structure standing on foundation piles is to be removed and a new structure constructed in its place, the disposal of the existing piles can be classified into three main categories: "direct use," "retention," and "removal." Of these, "removal" involves pulling out the existing piles and driving in new piles (see, for example, Patent Document 1).

[0003] As mentioned above, one method for pulling out and removing an existing pile is to insert a hollow steel pipe around the existing pile and then pull it out. This separates the existing pile from the surrounding ground by using the hollow steel pipe to separate the pile, so to speak, and this prevents the surrounding ground from collapsing when the existing pile is pulled out, allowing the removal work to be carried out more smoothly. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-66721 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if soil adheres to the inside of the hollow steel pipe, the intended effect of separating the edges may not be fully achieved.

[0006] Therefore, the present invention aims to provide a hollow steel pipe that can prevent soil from adhering to the inside of the hollow steel pipe, in order to fully maximize the effect of isolating existing structures buried in the ground, including existing piles, from the surrounding ground using the hollow steel pipe, and a method for extracting existing structures using the hollow steel pipe. [Means for solving the problem]

[0007] One aspect of the present invention is a hollow steel pipe used to extract an existing structure buried in the ground, such as an existing pile, while it is contained within the hollow steel pipe, and to fill a backfill material into the hollow steel pipe after the existing structure has been extracted. This hollow steel pipe has an adhesion prevention mechanism that scrapes off soil and backfill material that has adhered to the inner wall of the hollow steel pipe.

[0008] A hollow steel pipe having such an adhesion suppression mechanism can fully perform the following functions: (1) when the pile is pulled out, the soil between the hollow steel pipe and the pile is sufficiently loosened; (2) when backfill material is poured in, the soil is sufficiently loosened so that the soil remaining in the hollow steel pipe does not act as a lid, preventing the backfill material from being filled in; and (3) when the hollow steel pipe is pulled out of the ground, the filled backfill material is sufficiently loosened so that it does not clog the casing, thereby preventing the backfill material from being discharged along with the hollow steel pipe.

[0009] The adhesion suppression mechanism in the hollow steel pipe as described above may include a co-rotation suppression mechanism.

[0010] The co-rotation suppression mechanism in the hollow steel pipe as described above may include an opening provided along the outer wall of the hollow steel pipe and a protrusion that passes through the opening from the inside to the outside of the hollow steel pipe.

[0011] The adhesion prevention mechanism in the hollow steel pipe as described above may comprise a ring-shaped body provided inside the hollow steel pipe and a protrusion-shaped body provided on the ring-shaped body and extending in the central axis direction of the hollow steel pipe, the opening being a long hole, and the ring-shaped body and the protrusion-shaped body being rotatable relative to the hollow steel pipe along the long hole.

[0012] The adhesion suppression mechanism in the hollow steel pipe as described above may comprise a protrusion provided on the inner peripheral wall of the hollow steel pipe.

[0013] The protrusion of the hollow steel pipe as described above may be hemispherical.

[0014] In the hollow steel pipe as described above, an adhesion suppression mechanism may be provided below the hollow steel pipe.

[0015] The hollow steel pipe as described above may have multiple casings connected along the central axis of the hollow steel pipe, and at least the casing located at the lowest level among these multiple casings may be provided with an adhesion prevention mechanism.

[0016] Another aspect of the present invention is a method for extracting an existing structure, which uses the hollow steel pipe described above to extract an existing structure buried in the ground. [Effects of the Invention]

[0017] According to the present invention, by preventing soil from adhering to the inside of the hollow steel pipe, the hollow steel pipe can be effectively used to separate the existing structure from the surrounding ground. [Brief explanation of the drawings]

[0018] [Figure 1] This is a diagram showing an example of a construction procedure for inserting and burying a hollow steel pipe without peripheral holes and with a spiral 10S around it into the ground. [Figure 2] 10A and 10B are diagrams showing an example of a construction procedure for extracting an embedded hollow steel pipe. [Figure 3]FIG. 10 is a diagram illustrating a pin-type joint as an example of a joint between casings. [Figure 4A] FIG. 10 is a plan view illustrating a flange type joint as an example of a joint between casings. [Figure 4B] 10A and 10B are front and side views illustrating a flange type joint as an example of a joint between casings. [Figure 5] This figure shows an example of a construction procedure in which a hollow steel pipe with a spiral around it and no peripheral holes is inserted into the ground, up to the extraction of an existing pile. [Figure 6] This is a diagram showing an example of a construction procedure in which a hollow steel pipe with a spiral around it and a peripheral hole is inserted into the ground, and then an existing pile is pulled out. [Figure 7] This is a diagram showing an example of a construction procedure in which a hollow steel pipe without a spiral around it and without peripheral holes is inserted into the ground and an existing pile is pulled out. [Figure 8] This is a diagram showing an example of a construction procedure in which a hollow steel pipe with a peripheral hole and no spiral around it is inserted into the ground and an existing pile is pulled out. [Figure 9] 10A to 10C are diagrams showing an example of a cover member that opens and closes a peripheral hole, as viewed from three different directions. [Figure 10] 10A to 10C are diagrams showing another example of a cover member for opening and closing a peripheral hole, as viewed from three different directions. [Figure 11] FIG. 10 is a diagram showing an example of an adhesion suppression mechanism formed by a protrusion provided on the inner peripheral wall of a hollow steel pipe. [Figure 12A] 1 is a perspective view showing an example of an adhesion suppression mechanism composed of a protrusion, an annular body, and a protruding body that can rotate relative to a hollow steel pipe. FIG. [Figure 12B] 1 is a plan view showing an example of an adhesion suppression mechanism composed of a protrusion, an annular body, and a protruding body that can rotate relative to a hollow steel pipe. FIG. [Figure 13] FIG. 1 is a perspective view showing an example of a fastening tool that can be used when removing a buried hollow steel pipe. [Figure 14]FIG. 10 is a perspective view showing another example of a fastening tool that can be used when removing a buried hollow steel pipe. [Figure 15] FIG. 10 is a diagram showing a schematic example of a configuration for sending air or water into the casing pipe to remove soil clogs downward. [Figure 16A] FIG. 10 is a plan view schematically showing an example of a configuration for spraying air, water, etc. using a jet pipe for edge cutting provided on the peripheral surface of a casing. [Figure 16B] 10 is a cross-sectional view showing an example of a configuration for spraying air, water, etc. using a jet pipe for edge cutting provided on the peripheral surface of a casing. FIG. [Figure 17] FIG. 10 is a diagram showing an example of the configuration of an introduction member that maintains verticality when pouring a hollow steel pipe. DETAILED DESCRIPTION OF THE INVENTION

[0019] The configuration of the present invention will be described in detail below based on an example of an embodiment shown in the drawings (see FIG. 1, etc.).

[0020] The hollow steel pipe 10 according to the present invention is used to cut off the connection between an existing pile P and the surrounding ground G when an existing pile P buried in the ground G is pulled out and removed by penetrating the pipe around the existing pile P. Below, we will first explain the construction procedure for penetrating and burying the hollow steel pipe 10 in the ground G, and then the construction procedure for pulling out the existing pile P (see Figures 1 to 6), and then explain the structural features of the hollow steel pipe 10 (see Figure 7, etc.).

[0021] [Construction procedure for inserting and burying the hollow steel pipe 10 into the ground G] An example of a construction procedure for inserting and burying a hollow steel pipe 10 without peripheral holes and having a spiral 10S around its periphery into ground G will be described below (see Figure 1). Note that the soil around an existing pile P in the ground G is indicated by the symbol D in Figure 1.

[0022] A mouth pipe 81 is installed around the existing pile P (see Figure 1(A)). A lower casing 11 is erected in a hole J different from the pile hole H where the existing pile P is located, and a jig 82 is connected to connect the casing to the drive unit of the construction machine. In addition, a wire 83 is attached to the pile head of the existing pile P (see Figure 1(A)).

[0023] The lower casing 11 is driven around the existing pile P, and the jig 82 is removed. The middle casing 12 is erected in a separate hole J, and the jig 82 is connected (see FIG. 1(B)).

[0024] The middle casing 12 is connected to the lower casing 11 (see FIG. 1(C)).

[0025] The middle casing 12 is cast and the jig 82 is removed. The upper casing 13 is erected in a separate hole J and the jig 82 is connected (see FIG. 1(D)).

[0026] The upper casing 13 is connected to the middle casing 12 (see FIG. 1(E)).

[0027] A hollow steel pipe 10 consisting of an upper casing 13, a middle casing 12 and a lower casing 11 is cast to the planned depth (see FIG. 1(F)).

[0028] The jig 82 is made removable by removing the nuts that connect the jig 82 to the upper casing 13 (see FIG. 1(G)).

[0029] The hollow steel pipe 10 is again driven into the hole to the planned depth by pushing it in only, and the jig 82 is removed (see FIG. 1(H)).

[0030] [Procedure for pulling out hollow steel pipe 10] An example of a construction procedure for extracting the hollow steel pipe 10 buried as described above (after removing the existing pile) will be described (see FIG. 2).

[0031] The mouth pipe 81 is pulled out and excavation is carried out around the pile hole H. A worker descends into the enlarged pile hole, connects a jig 82 to the hollow steel pipe 10 (which constitutes the upper casing 13), and pours in soil as backfill material (indicated by the symbol B in the figure) (see Figure 2(A)).

[0032] When compacting, after pouring backfill material B, pull up the casing and then compact it by pushing the casing in again once or multiple times (see Figure 2(B)).

[0033] Add soil (see Figure 2(C)).

[0034] The hollow steel pipe 10 is pulled up and tamped (see FIG. 2(D)).

[0035] The upper casing 13 is removed and soil is added (see FIG. 2(E)).

[0036] The middle casing 12 and the lower casing 11 are pulled up and tamped down (see FIG. 2(F)).

[0037] The inner casing 12 is removed (see FIG. 2(G)).

[0038] Pull out and remove the lower casing 11 (see FIG. 2(H)).

[0039] The mouth pipe 81 is pulled out and the pile hole H is backfilled (see FIG. 2(I)).

[0040] [Casing joint example (pin type)] As an example of a joint between casings, a pin type will be explained (see Figure 3). Note that although an example of joining (connecting) the lower casing 11 and the upper casing 13 is shown here, it goes without saying that a similar structure can also be applied when an intermediate casing 12 is interposed between them.

[0041] In this example, the protrusion 13b of the upper casing 13 is inserted into an L-shaped groove 11d provided on the inner peripheral surface of the lower casing 11 and rotated circumferentially (in the example shown in FIG. 3, the upper casing 13 is rotated clockwise when viewed from above) until the protrusion 13b is locked in the groove 11d (see FIGS. 3(A) and 3(B)). Then, the bridge 17a is inserted into the groove 11d of the lower casing 11, and the pin 17b is inserted into the pin hole 11e of the lower casing 11 to fix the bridge 17a (see FIG. 3(C)). In this way, the bridge 17a prevents the movement of the protrusion 13b, and the lower casing 11 and the upper casing 13 are joined (connected). A bolt or the like may be used instead of the pin 17b.

[0042] [Casing joint example (flange type)] As another example of a joint between casings, a flange type will be described (see Figures 4A and 4B). When joining (connecting) the lower casing 11 and the upper casing 13 as in the above example, flanges 11f and 13f are provided at the upper end of the lower casing 11 and the lower end of the upper casing 13, respectively, and the lower casing 11 and the upper casing 13 can be joined (connected) by aligning the bolt holes of both flanges 11f and 13f and fastening them with bolts 18a and nuts 18b (see Figures 4A and 4B).

[0043] [An example of a construction procedure from penetrating the hollow steel pipe 10 into the ground G to pulling out the existing pile P] Next, an example of a construction procedure will be described (see Figure 5) from inserting a hollow steel pipe 10 without peripheral holes and having a spiral 10S around it into the ground G to pulling out an existing pile P. Note that some of the construction procedures shown below differ from the above construction procedure shown in Figure 1, but any of the procedures can be selected as appropriate for actual construction, and the construction procedures are not limited to any one of them.

[0044] In this example, first, the lower casing 11 and the upper casing 13 are connected in advance (see FIG. 5(A)).

[0045] In addition, a reinforcing steel rod 84 for edge separation confirmation is attached to the head of the existing pile P in the pile hole H to confirm that the edge between the casing and the existing pile P has been severed (see Figure 5(B)). When attaching the reinforcing steel rod 84, if the hollow portion of the head of the existing pile P is made of concrete or the like, a simple method such as directly inserting the reinforcing steel rod 84 with a hammer may be employed. Here, edge separation as used herein means that when the hollow steel pipe 10 (or the casing constituting it) is inserted around the existing pile P while rotating, the edge between the existing pile P and the ground G is severed, causing the existing pile P to rotate along with the rotation of the hollow steel pipe 10 (or the casing constituting it). The state in which the existing pile P can be pulled out is when the edge between the existing pile P and the ground G has been completely severed, and this state is confirmed by the phenomenon in which the reinforcing steel rod 84 for edge separation confirmation rotates along with the existing pile P. This allows the periphery of the existing pile P to be sufficiently severed (separated).

[0046] Next, the lower casing 11 and the upper casing 13 are driven around the existing pile P and penetrated (see Figure 5(C)). After that, the upper casing 13 is temporarily removed, and the middle casing 12 and the upper casing 13 are connected and assembled in a hole (casing erection hole) J separate from the pile hole H. After assembly, the middle casing 12 and the upper casing 13 are connected to the lower casing 11 (see Figure 5(D)). Then, the hollow steel pipe 10 (the lower casing 11, the middle casing 12, and the upper casing 13) is driven and penetrated to an appropriate depth (see Figure 5(E)). Thereafter, the upper casing 13 is removed, and the existing pile P is pulled out of the pile hole H (see Figure 5(F)). After the existing pile P is pulled out, soil is backfilled with the hollow steel pipe 10 (the lower casing 11 and the middle casing 12 that make up the pipe) remaining in the ground G to prevent loosening of the surrounding ground (not shown).

[0047] [Another example of the construction procedure from penetrating the hollow steel pipe 10 into the ground G to pulling out the existing pile P] In the above example, a hollow steel pipe 10 having a spiral 10S around its periphery and no peripheral holes is used, but similar procedures can also be used when other hollow steel pipes 10 are used. As other examples, FIG. 6 shows an example of the construction procedure when a hollow steel pipe 10 having a spiral 10S around its periphery and a peripheral hole (indicated by the reference symbol 20) is used, FIG. 7 shows an example of the construction procedure when a hollow steel pipe 10 having no spiral around its periphery and no peripheral holes is used, and FIG. 8 shows an example of the construction procedure when a hollow steel pipe 10 having no spiral around its periphery and a peripheral hole 20 is used. Note that the construction procedure shown in FIGS. 6 to 8 is the same as the construction procedure shown in FIG. 5, so the explanation of FIGS. 6 to 8 will be omitted. Needless to say, the above explanation is merely an example, and a casing without peripheral holes and having a spiral 10S around it (see Figure 5) may be used in combination with a casing with peripheral holes 20 and having a spiral 10S around it, or a casing without peripheral holes and having no spiral around it (see Figure 7) may be used in combination with a casing with peripheral holes 20 and having no spiral around it (see Figure 8).

[0048] [Cover member 30 for opening and closing peripheral hole 20] When a hollow steel pipe 10 having peripheral holes 20 is used (see Figs. 6 and 8), a cover member 30 can be used in combination as a soil flow prevention member for preventing soil from flowing in or out through the peripheral holes 20. This cover member 30 will be described below (see Figs. 9 and 10).

[0049] The cover member 30 is a cover that opens and closes the circumferential hole (hole portion) 20 provided in the hollow steel pipe 10 (or the casing that constitutes it), and when closed, at least a portion of the circumferential hole 20 is blocked. The advantages of providing a circumferential hole 20 in the hollow steel pipe 10 include: (1) reducing resistance and preventing soil clogging inside the pipe by allowing mud and water to pass through the inside and outside of the pipe during construction; (2) allowing the pipe to be placed on the ground by passing an iron rod through the circumferential hole 20 during construction; and (3) improving construction work efficiency by allowing the inside of the steel pipe to be observed. On the other hand, providing a circumferential hole 20 in the hollow steel pipe 10 can cause a problem: after an existing pile P is pulled out of the ground G, soil from the collapsed surrounding ground may flow into the hollow steel pipe 10 through the circumferential hole 20. If soil flows into the hollow steel pipe 10 through the peripheral holes 20 in this way, it may not be possible to fill all of the intended amount of backfill soil, which may result in variations in the strength of the backfill material B after backfilling or the occurrence of hollow spaces. In this regard, providing a cover member 30 that can freely open and close the peripheral holes 20 can solve this problem. Furthermore, by leaving the peripheral holes 20 open when necessary, the intended function of the peripheral holes 20 can be achieved. The cover member (or blocking member) 30 does not have to completely cover the entire peripheral holes 20. Furthermore, it does not have to cover all of the multiple peripheral holes 20 provided in the hollow steel pipe 10.

[0050] An example of the specific structure of the lid member 30 will be described with reference to the drawings. The lid member 30 shown in Fig. 9 is connected to the hollow steel pipe 10 (the casing that constitutes it) with a connecting pin 31 so that it can be opened and closed freely, and is provided so that it cannot be opened when it is locked with a locking pin 33 in the closed state (see Figs. 9(A) to (C)).

[0051] Although the specific form of the connecting pin 31 is not particularly limited, in this embodiment, the connecting pin 31 is provided at a position directly above the peripheral hole 20 so as to follow the direction of a tangent extending in the circumferential direction on the peripheral surface (surface of the outer wall 10o) of the hollow steel pipe 10 (or casing). The cover member 30 connected by a hinge structure including such a connecting pin 31 opens and closes in a direction (approximately coinciding with the vertical direction during construction) parallel to the central axis 10C of the hollow steel pipe 10 or the central axis of the casing (indicated by symbol C in Fig. 4B and Fig. 11) with the connecting pin 31 as the rotation center (see Fig. 9(C) etc.).

[0052] The locking pin 33 is a pin consisting of a shaft portion and a head portion with a larger diameter that can be inserted into and removed from both the cylindrical portion 36 provided at the end of the cover member 30 and the cylindrical portion 16 provided on the outer peripheral wall 10o of the hollow steel pipe 10. When the locking pin 33 is inserted when the cylindrical portion 36 and the cylindrical portion 16 are aligned in a straight line, the cover member 30 is locked and held in a closed state (see Figure 9(A) etc.).

[0053] Another example of the specific structure of the lid member 30 will be described with reference to the drawings. The lid member 30 shown in Fig. 10 is composed of a member that slides along a guide member 32 provided on the hollow steel pipe 10 (or casing). The guide member 32 in this embodiment includes, for example, a pair of parallel members on the left and right (stepped and holding the lid member 30 so that it does not fall outward in the radial direction of the hollow steel pipe 10) and a member that functions as a stopper and is positioned below them during construction, and is arranged on three sides so as to form a channel shape (a "C" shape) with only the side that will be upper during construction open (see Fig. 10(A) etc.). The lid member 30 is inserted into this guide member 32 from the side that will be upper during construction and is positioned in a predetermined position. In addition, by inserting a locking pin (locking member) 33 into a pin hole 32a provided near the upper end of the guide member 32, the cover member 30 can be locked so that it does not move upward on the guide member 32 or fall off from the guide member 32 (see Figure 10(C) etc.).

[0054] In the drawings shown in the above explanation, the outer peripheral wall 10o of the hollow steel pipe 10 (or casing) is shown as if it were flat (see Figures 9 and 10), but it should be noted that this is merely for the sake of convenience in the drawings. It goes without saying that if the hollow steel pipe 10 (or casing) is cylindrical, the outer peripheral wall 10o will actually be curved in the circumferential direction.

[0055] The cover member 30 may also be a mesh made of reinforcing bars or the like.

[0056] The cover members 30 described above using examples up to this point may be arranged to correspond to all of the circumferential holes 20 of the hollow steel pipe 10, or may be arranged only for some of the multiple circumferential holes 20. In short, in order to prevent soil from the collapsed surrounding ground from flowing into the inside of the hollow steel pipe 10 through the circumferential holes 20, depending on the desired degree, it may not be necessary to cover all of the circumferential holes 20, and in such cases, it can be said that it is sufficient to arrange the cover members 30 only for some of the multiple circumferential holes 20.

[0057] Furthermore, when arranging the cover members 30 only for some of the multiple circumferential holes 20 in this manner, the cover members 30 may be arranged to block the circumferential holes 20 provided in at least the lowest casing among the multiple casings (the lower casing 11 in the above embodiment). Generally, it is the underlying ground that is particularly problematic if it loosens during a series of construction works, and it is expected that stable backfilling will become relatively difficult if the underlying ground loosens. If this point is taken into consideration when arranging the cover members 30 only for some of the multiple circumferential holes 20, for example, by blocking the circumferential hole 20 of the lowest casing with the cover member 30 as described above, it will be possible to prevent the ground in the lower layers from loosening.

[0058] The cover member 30 described so far is merely one suitable example of a member that functions as a soil flow prevention member for preventing soil from flowing in or out through the peripheral holes 20. In addition to the cover member 30 described above, the soil flow prevention member may have the following configurations and aspects. - Wrap it around with tape or use a ring-shaped plate that covers the outer periphery of the casing to seal the outside including the peripheral hole 20. A plate material having a diameter larger than the peripheral hole 20 is fastened to the outer wall with bolts or the like so as to close the peripheral hole 20. -Closing the peripheral hole 20 with a plug

[0059] [Adhesion suppression mechanism] The hollow steel pipe 10 may be provided with an adhesion prevention mechanism 40 as a mechanism for preventing soil and the like from adhering. If soil adheres or sticks to the inside of the hollow steel pipe 10, there is a risk that the intended edge-cutting effect cannot be fully achieved, but by providing the adhesion prevention mechanism 40, it is possible to achieve the desired edge-cutting effect.

[0060] One specific example of the adhesion prevention mechanism 40 is configured by protrusions 41 provided on the inner peripheral wall 10i of the hollow steel pipe 10 (see FIG. 11). In this case, if the protrusions 41 have a smooth shape, soil is less likely to adhere to the surface, which is preferable in that adhesion can be prevented. As an example, in this embodiment, multiple protrusions 41 each having an approximately hemispherical shape are provided on the inner peripheral wall 10i of the hollow steel pipe 10 (see FIG. 11). Note that the shape of the protrusions 41 is not limited to hemispherical.

[0061] Another specific example of the adhesion prevention mechanism 40 will be described (see Figs. 12A and 12B). The adhesion prevention mechanism 40 shown in the figures includes a co-rotation prevention mechanism 42. Co-rotation as used in this specification refers to the phenomenon in which, when the hollow steel pipe 10 (or the casing that constitutes it) is inserted into the existing pile P while rotating around it, the soil between the hollow steel pipe 10 and the existing pile P rotates around the existing pile P together with the hollow steel pipe 10. The co-rotation prevention mechanism 42 is configured to effectively suppress this phenomenon of co-rotation.

[0062] A specific example of the co-rotation suppression mechanism 42 is shown below. The co-rotation suppression mechanism 42 of this embodiment includes an opening 43, a protrusion 44, an annular body 45, and a protruding body 46 (see FIGS. 12A and 12B).

[0063] The openings 43 are holes formed in the outer peripheral wall 10o of the hollow steel pipe 10. In this embodiment, two openings 43 are provided at the same height and in opposing positions. This pair of holes is an elongated hole formed in the circumferential direction by a circumferential angle A, for example, approximately 90° (see FIG. 12B). Note that such openings 43 may also function as the peripheral holes (hole portions) 20 in the above-described embodiment.

[0064] The protrusion 44, the annular body 45, and the protruding body 46 are integrally formed. The annular body 45 is a circular member, and although its cross-sectional shape is rectangular in this embodiment, it may be circular or the like. The annular body 45 is formed so that its outer diameter is slightly smaller than the inner diameter (of the inner peripheral wall 10i) of the hollow steel pipe 10, and is disposed inside the hollow steel pipe 10.

[0065] The protrusions 44 are configured as a pair of protrusions, for example two protrusions, formed so as to extend radially outward from the annular body 45. Each of the pair of protrusions 44 is arranged so as to protrude from the inside to the outside of the hollow steel pipe 10 through an opening 43. The opening 43, which is an elongated hole, functions as a guide that guides each protrusion 44 in the circumferential direction. The protrusions 44 guided by the opening 43 can rotate together with the annular body 45 in the circumferential direction relative to the hollow steel pipe 10 by an amount corresponding to the circumferential angle A (slightly less than 90° in this embodiment) (see Figure 12B).

[0066] The protruding bodies 46 are provided to protrude from the annular body 45 and are configured to move circumferentially along the inner peripheral wall 10i of the hollow steel pipe 10, thereby acting like a scraper to scrape off soil adhering to the inner peripheral wall 10i. Based on this, the protruding bodies 46 of this embodiment are configured to extend vertically along the axial direction of the central axis 10C of the hollow steel pipe 10, and are capable of scraping off soil adhering to the inner peripheral wall 10i by an area equivalent to the product of their vertical length and the circumferential movement length corresponding to the circumferential angle A. The number of such protruding bodies 46 is not particularly limited. In this embodiment, four protruding bodies 46 are arranged at equal intervals (every 90°) on the annular body 45 (see FIGS. 12A and 12B ).

[0067] The adhesion suppression mechanism 40 including the co-rotation suppression mechanism 42 configured as described above prevents soil from adhering or sticking to the interior of the hollow steel pipe 10 when the hollow steel pipe 10 is inserted into the ground G, thereby enabling the edge-cutting effect to be fully exerted. Moreover, in the co-rotation suppression mechanism 42 of this embodiment, the integrally formed member consisting of the protrusions 44, the annular body 45, and the protruding bodies 46 can rotate circumferentially relative to the hollow steel pipe 10 along the elongated openings 43 by an amount corresponding to the circumferential angle A. Therefore, when the hollow steel pipe 10 rotates forward or backward, the protrusions 44 protruding outward remain stuck in the soil, thereby loosening the soil and backfill material B inside the pipe. Furthermore, the protruding bodies 46, which move relatively along the inner peripheral wall 10i of the hollow steel pipe 10, also function to scrape off soil adhering to the inner peripheral wall 10i. A hollow steel pipe 10 having such an adhesion suppression mechanism 40 can fully perform the following functions: (1) when the existing pile P is pulled out, the soil between the hollow steel pipe 10 and the existing pile P is sufficiently loosened; (2) when the backfill material B is introduced, the soil is sufficiently loosened so that the soil remaining in the hollow steel pipe 10 does not form a lid and prevent the backfill material B from being filled in; and (3) when the hollow steel pipe 10 is pulled out from the ground G, the filled backfill material B is sufficiently loosened so that it does not clog the casing, thereby preventing the backfill material B from being discharged together with the hollow steel pipe.

[0068] When the hollow steel pipe 10 is made up of multiple casings as in this embodiment, providing the adhesion prevention mechanism 40 in at least the lowest casing (in this embodiment, the lower casing 11) makes it possible to prevent clogging at the tip end of the hollow steel pipe 10, which is particularly prone to soil clogging. The adhesion prevention mechanism 40 needs to be located at least below the hollow steel pipe 10. In the case of a casing, the adhesion prevention mechanism 40 needs to be located in the lowest casing. The hollow steel pipe 10 (or the casing that is a component of it) may be provided with both the protrusion 41 and the co-rotation prevention mechanism 42.

[0069] [Method of removing hollow steel pipes after filling with backfill material] As described above, after the existing pile P is extracted from the ground G, the hollow steel pipe 10 is left in the ground G, and backfilling material B is used to prevent loosening of the surrounding ground. However, after backfilling, when the hollow steel pipe 10 is extracted and removed, the soil inside the hollow steel pipe 10 may rise up and not fall down. If this phenomenon occurs, there is a possibility that the excavated hole will not be sufficiently filled with soil, resulting in a hollow space. In view of the above, in this embodiment, the following means are adopted to prevent this possibility (see FIG. 13, etc.).

[0070] That is, a so-called "kanzashi" (iron rod) 51 is inserted into the peripheral hole 20 of the casing 11 (12, 13) constituting the hollow steel pipe 10 and penetrates through it, and both ends of the kanzashi 51 are placed directly on the ground G or on a boat (foundation) 52, so that the casing 11 (12, 13) is suspended (stored) using a fastening device 50 (see Figure 13). Alternatively, instead of using the kanzashi 51, a wire 53 hung on the boat 52 may be passed through the peripheral hole 20 to suspend the casing 11 (12, 13) (see Figure 14).

[0071] By using such a means as a pin 51 or wire 53 to temporarily hold the casing 11 (12, 13), the operation of gradually (for example, at the level of several tens of centimeters) pouring backfill material B into the hollow steel pipe 10 and then repeatedly pulling up the casing 11 (12, 13) is performed to prevent soil from clogging the hollow steel pipe 10.

[0072] When using such means to prevent soil from clogging the hollow steel pipe 10, the following devices or means may be used in combination to more effectively prevent clogging. The rod 54 is pushed into the casing 11 (12, 13) from above (see FIG. 14). The protrusions inside the casing 11 (12, 13) are eliminated to prevent resistance. In other words, while nails or iron bars (rectangular pieces of iron) are sometimes attached to the inside of the casing 11 (12, 13) to loosen the soil during excavation, these can actually create resistance when backfilling, causing the soil to become clogged, so these have been eliminated. -Use a material that is less likely to clog as backfill material B. Air or water is pumped into the pipe of the casing 11 (12, 13) from above ground to apply pressure and drop the soil clog downward (see Figure 15). Air or water outlet holes 19 are provided on the circumferential surface of the casing 11 (12, 13), and air or water is ejected from the air outlet holes 19 using an air or water ejection pipe 59 for edge cutting (see Figures 16A and 16B). Although not shown, an ejection pipe (ejection passage) may be formed so as to pass through the thicker portion of the casing 11 (12, 13).

[0073] In addition, considering the case where the casing 11 (12, 13) is temporarily suspended using the hairpin 51 or wire 53 as described above, the peripheral hole 20 may be provided in the upper (vertically upward) part of the casing 11 (12, 13).

[0074] [Ensuring verticality, checking pile heads (inlet pipe)] Conventionally, when driving steel pipe piles, a construction machine equipped with a vibration damper is used to keep the steel pipe pile vertical. However, when the hollow steel pipe 10 (including the casings 11, 12, and 13) is the target, it can be difficult to damp the casing, especially if it has a large diameter.

[0075] Furthermore, when removing the existing pile P, there are issues such as: (1) the vertical state of the existing pile P in the ground is unknown; (2) after the hollow steel pipe (the casing that constitutes it) is inserted, it is not possible to confirm whether the existing pile and the hollow steel pipe (the casing that constitutes it) are vertical; and (3) if the hollow steel pipe is driven without maintaining the vertical state, it will interfere with the existing pile and in some cases twist off the existing pile.

[0076] In this regard, in this embodiment, when driving the hollow steel pipe 10 around the existing pile P to penetrate it, an introduction member 60 is used to maintain the verticality of the hollow steel pipe 10 when driving the hollow steel pipe 10, thereby solving the above-mentioned problem (see FIG. 17). By using such an introduction member 60, the hollow steel pipe 10 can be installed evenly with respect to the pile center (the central axis Pc of the existing pile P).

[0077] The introduction member 60 of this embodiment is composed of a tubular body that is smaller than the inner diameter of the hollow steel pipe 10 and larger than the outer diameter of the existing pile P, and is arranged along the inner peripheral wall 10i of the hollow steel pipe 10 (see Figure 17). The introduction member 60 may also be composed of a reinforcing bar cage that is arranged along the inner circumference of the hollow steel pipe 10 and is smaller than the inner diameter of the hollow steel pipe 10 and larger than the outer diameter of the existing pile. Such an introduction member 60 can maintain the verticality of the hollow steel pipe 10. Note that an introduction member with a different configuration can also be used, for example, an introduction member 60 in which the inner diameter of at least a part (or all) of the upper side is larger than the outer diameter of the casing 11 (12, 13).

[0078] There is no particular limitation on the material of the introduction member 60. In this embodiment, a steel tubular introduction member 60 is used. The introduction member 60 can be more easily maintained vertically if it is made of a highly rigid material.

[0079] Furthermore, the introduction member 60 of this embodiment is hollow, and has a holding member 61 formed, for example, in a sleeve or dish shape, on the inner periphery of the introduction member 60, which is held by the head of the existing pile P. By holding a part of the tip of the introduction member 60 in the head of the existing pile P, it becomes possible to maintain verticality.

[0080] Moreover, the introduction member 60 of this embodiment has an insertion portion 62 that excavates the soil around the existing pile P and inserts it into the excavated soil. By inserting the introduction member 60 into the ground G using such an insertion portion 62, it is possible to guide the hollow steel pipe 10 so that it is parallel to the existing pile P, even if the existing pile P is at an angle.

[0081] The introduction member 60 may be configured so that the upper part of the introduction member 60 extends to the ground when it is placed between the existing pile P and the hollow steel pipe 10 when the hollow steel pipe 10 is driven into place. When the excavated soil is backfilled after the pile head has been confirmed, if the reinforcing rod 84 inserted into the pile head becomes unclear and the pile head cannot be reconfirmed, it becomes impossible to continue to reliably confirm the pile head underground. However, with this introduction member 60, the location of the existing pile P can be easily confirmed.

[0082] That is, one aspect of the present invention is (1) An introduction member that maintains the verticality of a hollow steel pipe when driving (penetrating) it around an existing structure buried in the ground, such as an existing pile. (2) The introduction member described in (1) is composed of a tubular body that is smaller than the inner diameter of the hollow steel pipe and larger than the outer diameter of the existing structure, and is arranged along the inner circumference of the hollow steel pipe. (3) The introduction member according to (2), wherein the tubular body is made of steel. (4) The introduction member described in (1) is arranged along the inner circumference of the hollow steel pipe and is composed of a reinforcing bar cage that is smaller than the inner diameter of the hollow steel pipe and larger than the outer diameter of the existing structure. (5) The introduction member according to any one of (2) to (4), which is hollow and has a holding member on the inner periphery of the introduction member that is held by the head of the existing structure. (6) The introduction member according to any one of (1) to (5), which excavates the soil around the existing structure and has an insertion portion that is inserted into the excavated soil. (7) An introduction member as described in (6), in which the upper part of the introduction member extends to the ground when the introduction member is placed between the existing structure and the hollow steel pipe when the hollow steel pipe is cast. (8) A method for extracting an existing structure buried in the ground using a hollow steel pipe described in any one of (1) to (7).

[0083] The above-described embodiment is one example of a preferred embodiment of the present invention, but is not limited thereto and various modifications are possible within the scope of the present invention. For example, in the above-described embodiment, a case where the hollow steel pipe 10 is driven around an existing pile P is described, but the existing pile P is merely one example of an existing underground structure at the construction site. Naturally, the present invention can also be applied to cases where the hollow steel pipe 10 is driven around various existing structures such as spread foundations, columnar improvement bodies, etc., in addition to existing piles, in other words, around objects that may become obstacles underground. [Industrial Applicability]

[0084] The present invention is suitable for application to a method for extracting hollow steel pipes and existing structures using such pipes. [Explanation of symbols]

[0085] 10...Hollow steel pipe 10C…Central axis 10i…Inner peripheral wall 10o...Outer wall 10S...Spiral 11...Lower casing (casing) 11d...Groove 11e...Pinhole 12...Middle casing (casing) 13...Upper casing (casing) 13b...Protrusion 16...Cylindrical part 17a... Piece 17b...Pin 18a...Bolt 18b...Nat 19...Air outlet 20...Peripheral hole (hole) 30...Cover member (soil flow prevention member) 31...Connecting pin 32...Guide member 32a...Pin hole 33...Latching pin (locking member) 36...Cylindrical part 40...Adhesion suppression mechanism 41...Protrusion 42... Co-rotation suppression mechanism 43...Long hole (open hole) 44...Protrusion 45...Ring 46...Protruding body 50...Latching device 51... Hairpin (horizontal bar) 52…ship 53...Wire 54...Rod 59...Air jet pipe 60...Introduction member 60u…upper 61...holding member 62...insertion part 81...Mouth tube 82...Jig 83...Wire 84...Reinforced concrete A: Circumferential angle of opening B: Backfill material C: Casing central axis D...Soil G...Ground H…Pile hole J...Another hole P...Existing pile (existing structure) Pc: central axis of the pile

Claims

1. A hollow steel pipe used to extract an existing structure buried in the ground, such as an existing pile, while it is contained within the hollow steel pipe, and to fill the hollow steel pipe with backfill material after the existing structure has been extracted. an adhesion suppression mechanism for scraping off soil and backfill material adhering to the inner peripheral wall of the hollow steel pipe; The adhesion suppression mechanism includes a co-rotation suppression mechanism, the co-rotation suppression mechanism comprises an opening provided along the outer peripheral wall of the hollow steel pipe, and a protrusion passing through the opening from the inside to the outside of the hollow steel pipe, The adhesion prevention mechanism comprises a ring-shaped body provided inside the hollow steel pipe and a protrusion-shaped body provided on the ring-shaped body and extending in the central axis direction of the hollow steel pipe, the opening being a long hole, and the ring-shaped body and the protrusion-shaped body are capable of rotating relative to the hollow steel pipe along the long hole.

2. The hollow steel pipe according to claim 1 , wherein the adhesion suppression mechanism comprises a protrusion provided on an inner peripheral wall of the hollow steel pipe.

3. The hollow steel pipe according to claim 2, wherein the protrusion is hemispherical.

4. The hollow steel pipe according to claim 1 , wherein the adhesion suppression mechanism is provided below the hollow steel pipe.

5. A hollow steel pipe as described in any one of claims 1 to 4, wherein a plurality of casings are connected along the central axis direction of the hollow steel pipe, and at least the casing located at the lowest level among the plurality of casings is provided with the adhesion prevention mechanism.

6. A method for extracting an existing structure, comprising extracting an existing structure buried in the ground using the hollow steel pipe according to any one of claims 1 to 5.

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