JP5869425B2 - Formation method of through hole - Google Patents

Description

  The present invention relates to a method of forming a through-hole for inserting a reinforcing bar, a tension material for introducing prestress, or the like into a concrete member.

  In forming the concrete member, a through hole may be formed in advance in the concrete member. For example, after placing concrete, a tension material for introducing prestress into the concrete is inserted into the through hole, and a tension force is introduced to fix the end to the concrete. In this way, the through-hole for inserting the tension material is usually placed in a predetermined position in the mold before placing the concrete member called a sheath, and the concrete is placed so that it is embedded. Is formed. Many sheaths are formed by joining steel strips in a spiral shape into a cylindrical shape, or molding a synthetic resin into a cylindrical shape, and these sheaths are generally used after concrete is cast and hardened. Is also retained as it is embedded in concrete. However, it is desirable to remove the sheath when the tension material is tensioned and the grout is filled with the grout and the tension material is fixed to the concrete member by the hardened grout. That is, there is a concern about deformation of the sheath due to a change in the sustained load or temperature, and it is desired to avoid this.

  On the other hand, the precast concrete member may be provided with a through-hole through which a reinforcing bar is inserted in order to join a plurality of precast concrete members to each other. For example, a reinforcing bar is embedded in one precast concrete member to be joined, and a reinforcing bar is protruded from an end face to be joined to another precast concrete member, and a through hole is provided in the precast concrete member to be joined, and the joining end face Insert the reinforcing bar protruding from the top, fill the through hole with grout, and harden it. Thereby, two precast concrete members are joined via a reinforcing bar. Since the through-hole through which the reinforcing bar is inserted as described above is a unit in which the reinforcing bar and the concrete are integrated via a grout, a mold for forming the through-hole remains on the inner peripheral surface of the through-hole. It is required to be in a state that is not.

As a method for forming such a through hole, for example, there are methods described in Patent Document 1, Patent Document 2, Patent Document 3, and the like.
The method described in Patent Document 1 includes a cylindrical member that is flexibly deformed as a mold for forming a through hole, and a core member made of steel or the like that is inserted into the cylindrical member and retains its shape. Use things. Then, pressurized air is introduced into the cylindrical member, and the section is embedded in the concrete to be placed while maintaining a substantially circular cross section. Moreover, in the method of patent document 2 and patent document 3, in order to make it easy to pull out a cylindrical member from the through-hole in which the cylindrical member was formed after hardening of concrete, a core material divides | segments a steel pipe into multiple by the dividing line of an axial direction. Using this, the diameter of the cylindrical member after the concrete is hardened can be easily reduced.

No. 5-23284 JP 11-320534 A JP 2009-184235 A

However, the conventional method for forming a through hole as described above has a problem that the following solution is desired.
In a through hole formed by embedding a sheath in concrete, it becomes difficult to remove the embedded sheath after the concrete has hardened. In a sheath in which steel sheets are spirally connected, when the length of the through-hole is small, the strip-shaped steel sheet can be removed while being separated, but the length of the through-hole is large. It becomes difficult.

  In addition, the method described in Patent Document 1 is based on the assumption that concrete is placed by supporting the cylindrical member in the vertical direction as described in FIG. 3 of Patent Document 1. It is not suitable for providing a through-hole that is long in the axial direction in a concrete member. Further, in the methods described in Patent Document 2 and Patent Document 3, a rigid pipe or a rigid cylindrical body that retains a shape is divided into a plurality of parts along an axial line, and a structure as a mold for forming a through hole is obtained. Complicated and not suitable for forming long through holes. Further, in order to provide a long through hole, a large amount of cost is required.

  This invention is made | formed in view of the above subjects, The objective is to provide the formation method of the through-hole which can form a long through-hole easily in a concrete member.

  In order to solve the above-mentioned problem, the invention according to claim 1 assembles a formwork for forming a concrete member, and the tubular member has a sectional shape flexibly deformed by the introduced air pressure. A rod-shaped or cylindrical shape holding member having an outer diameter smaller than the inner diameter of the cylindrical member is inserted, and the cylindrical member into which the shape holding member is inserted is bridged on a support member provided at a predetermined interval. It arrange | positions in the predetermined position in the said formwork, makes the both ends project from the concrete placement range in the said formwork, introduces pressurized air into the said cylindrical member, and pours concrete into the said formwork In addition, the cylindrical member has a substantially circular cross-sectional shape so that a space is maintained inside, and the shape is formed below the inner peripheral surface of the cylindrical member by buoyancy acting on the cylindrical member from uncured concrete. Protection The pressurized air in the cylindrical member is maintained so that the holding member is in contact, and after the concrete is cured, the pressurized air in the cylindrical member is released, and the shape holding member and the cylindrical member are Provided is a method for forming a through hole, which is drawn out from a hardened concrete member.

  In this through hole forming method, the cross-section of the tubular member is maintained substantially circular even when the tubular member is embedded in uncured concrete by the pressurized air introduced into the tubular member. And the shape of an axial direction is maintained by the shape along the axis of the shape holding member spanned on the support member by buoyancy. Therefore, a through-hole that is long in the horizontal direction and has a shape along the axis of the shape holding member can be formed with a simple configuration.

  The invention according to claim 2 is the method for forming a through-hole according to claim 1, wherein a negative pressure is introduced into the cylindrical member after the concrete is cured, and all or part of the outer peripheral surface of the cylindrical member is introduced. Is peeled from the concrete member, and the tubular member is pulled out from the concrete member.

  In this through hole forming method, since negative pressure is introduced into the cylindrical member by suction, the cross-section of the flexible cylindrical member is reduced, and the outer peripheral surface is peeled off from the concrete so that the cylindrical member can be easily pulled out. It becomes.

The invention according to claim 3 is the method for forming a through hole according to claim 1 or 2, wherein the shape retaining member is inserted into the tubular member after the concrete is cured, or the tubular shape. In a state where the shape holding member is pulled out from the member and a drawing core having a smaller outer diameter than the shape holding member is inserted into the cylindrical member, a negative pressure is introduced into the cylindrical member, and the cylindrical member While maintaining the state in which the inner peripheral surface of the cylindrical member is pressed against the outer peripheral surface of the shape holding member or the drawing core by the negative pressure inside, the cylinder together with the shape holding member or the drawing core It is assumed that the shaped member is pulled out from the concrete member.

  In this through-hole forming method, the shape retaining member is inserted into the tubular member, or after the shape retaining member is extracted from the tubular member, the drawing core is inserted into the tubular member. Since the pressure is introduced, the inner peripheral surface of the cylindrical member can be brought into pressure contact with the outer peripheral surface of the shape maintaining member or the core material for drawing. In this way, when a part of the cylindrical member is in pressure contact with the shape holding member or the drawing core, pulling the shape holding member or the drawing core and the cylindrical member pulls the tensile force into the shape holding member or The cylindrical member that is borne by and pressed against the drawing core can be pulled out together with the shape holding member or the drawing core. Therefore, even if a cylindrical member that is flexible and has a low tensile strength is used, it can be easily pulled out from the hardened concrete.

  According to a fourth aspect of the present invention, in the method for forming a through hole according to the third aspect, the drawing core material is a member having an outer peripheral surface that is uneven in the axial direction.

  In this through hole forming method, when a negative pressure is introduced into the inside of the tubular member and the tubular member is brought into pressure contact with the drawing core, the tubular member has irregularities following the shape of the drawing core. The resulting shape. Thereby, a cylindrical member peels in a wide area from the internal peripheral surface of the through-hole formed in concrete, and it becomes easy to pull out a cylindrical member from the hardened concrete member. In addition, when the cylindrical member is pressed against the outer peripheral surface of the extraction core material having unevenness, the extraction core material and the cylindrical member are prevented from being displaced in the axial direction, and the extraction force is borne by the pulling force. It becomes easy to pull out the cylindrical member together with the core material. Therefore, the cylindrical member can be easily pulled out from the concrete member even when a long through hole is formed.

  As described above, in the method for forming a through hole according to the present invention, the cylindrical member embedded in the concrete can be peeled off and pulled out from the concrete member with a simple member. It can be formed easily.

It is a schematic side view which shows the state which installed the through-hole formation type | mold used for the formation method of the through-hole which is one Embodiment of this invention, and this through-hole formation type | mold in the formwork. It is a figure which shows the process of the formation method of the through-hole which is the 1st Embodiment of this invention, Comprising: It is an expanded sectional view which shows a state when the through-hole formation type | mold shown in FIG. 1 is installed in the formwork. . It is a schematic sectional drawing which shows a state when installing the through-hole formation type | mold shown in FIG. 1 in a formwork, and placing concrete. It is a schematic sectional drawing which shows a state when installing the through-hole formation type | mold shown in FIG. 1 in a formwork, and placing concrete. It is a schematic sectional drawing which shows the process after placing and hardening concrete so that the through-hole formation type | mold shown in FIG. 1 may be embedded. It is a schematic sectional drawing which shows the process after placing and hardening concrete so that the through-hole formation type | mold shown in FIG. 1 may be embedded. It is a schematic sectional drawing which shows the process of introduce | transducing prestress into the concrete member after formation of a through-hole is completed. It is a schematic sectional drawing which shows the process of the formation method of the through-hole which is the 2nd Embodiment of this invention. It is a schematic sectional drawing which shows the process of the formation method of the through-hole which is the 2nd Embodiment of this invention. It is a schematic sectional drawing which shows the state which introduced the negative pressure inside the cylindrical member using the core material for drawing | extracting which can be used in embodiment shown in FIG.8 and FIG.9. It is a schematic sectional drawing which shows the process of the formation method of the through-hole which is the 3rd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic side view showing a through hole forming mold used in a method for forming a through hole according to an embodiment of the present invention and a state in which the through hole forming mold is installed in a mold.
The said through-hole formation type | mold 11 is arrange | positioned in the formwork 1 which forms a concrete member, before placing concrete, as shown in FIG. The through hole is formed in the concrete member.
As shown in FIG. 1B, the through-hole forming mold 11 includes a tubular member 12, and a shape holding member 13 that is inserted into the tubular member and regulates the shape of the tubular member 12 in the axial direction. A closing jig 14 for closing one end of the cylindrical member 12 and a base joined to the other end of the cylindrical member and serving as a pressure inlet for introducing pressurized air into the cylindrical member 15, the main part is configured.
The cylindrical member 12 is formed using chemical fiber and soft vinyl chloride as main raw materials, and its sectional shape and shape in the axial direction are flexibly deformed. Before use, the tubular member 12 is flattened and folded or wound. It can be transported and transported to the location where it will be used. Moreover, it can cut and use according to required length, and the cut both ends become an opening. For example, it can be used to form a through hole having a length of about 7 to 15 m in a concrete member, and is cut into a length longer than the length of the through hole.
For this cylindrical member 12, for example, a hose or the like generally used for conveying liquid or gas can be used.

  The shape holding member 13 is a rod-shaped member or a tubular member made of steel, and has an outer diameter smaller than the inner diameter of the tubular member 12 and set to such an extent that it can be easily inserted into the tubular member 12. Yes. In the present embodiment, it is formed to be approximately 2 mm to 5 mm smaller than the inner diameter of the cylindrical member 12 and is a substantially linear member. Further, the shape holding member 13 is provided with a rigidity that can be bridged on a support member provided at a predetermined interval in the axial direction and maintain a substantially linear shape.

The shape holding member 13 is formed to be shorter than the length of the cylindrical member 12 and is longer than the length between the opposing surfaces of the concrete member mold 1 in which the through hole is formed. That is, when the shape holding member 13 is inserted inside the cylindrical member 12, the length is set so that regions where the shape holding member 13 is not inserted are formed at both ends of the cylindrical member 12. And as shown to Fig.1 (a), while spanning between the opposing surfaces of the mold 1 with the said cylindrical member 12, the shape holding member 13 can be penetrated to both the molds 1 which oppose It has become.
The shape holding member 13 may be continuous within the range of the length set as described above, or may be a member in which a plurality of members are connected. For the connection, a structure is used in which the outer diameter does not change greatly at the joint using a joint or the like.

  The closing jig 14 closes one end that is an opening of the cylindrical member 12 to block the inflow and outflow of air, and the shape holding member 13 of the cylindrical member 12 is inserted. It is possible to employ a clip or the like that sandwiches and tightens a non-end portion.

  The base 15 is joined to the other end of the cylindrical member 12 to serve as an inlet for pressurized air or negative pressure, and is inserted into the cylindrical member 12 to form a cylindrical curved outer surface. The inner peripheral surface of the cylindrical member 12 is brought into contact with. And it press-contacts by the fastening member 16 from the outer side of a cylindrical member, and airtightness is hold | maintained between the nozzle | cap | die 15 and the cylindrical member 12. FIG. The introduction of pressurized air or the introduction of negative pressure is performed by an air pump (not shown) through an opening 15a provided in the base and a vent pipe 17 connected to be continuous with the opening 15a. It has become.

Using the through hole forming mold 11 as described above, the through hole of the concrete member is formed as follows.
The through-hole forming mold 11 is formed in the mold 1 for forming a concrete member as shown in FIGS. 1 (a) and 1 (b) in a state where the shape holding member 13 is inserted into the cylindrical member 12. Deploy. In the mold 1, reinforcing bars 2 are assembled, and supported by these reinforcing bars 2 and supporting bars 3 serving as support members are arranged at predetermined intervals along the arrangement positions of the through-hole forming mold 11. And the through-hole formation type | mold 11 is mounted so that it may bridge over the said supporting muscle 3. FIG. The support bars 3 have an interval at which the shape holding member 13 inserted into the cylindrical member 12 is maintained substantially linearly on the support bars 3 due to its rigidity. Further, both end portions of the through-hole forming mold 11 are inserted through openings formed in two opposing surfaces of the mold 1 so that the ends protrude outside the mold 1. At this time, the shape holding member 13 inserted through the cylindrical member 12 also protrudes outside the mold 1 in the cylindrical member 12 as shown in FIG.

The cylindrical member 12 protruding outward from the mold 1 is closed at one end by a closing jig 14, attached to the other end by a base 15, and connected to an air pump by a vent pipe 17. Then, the air pump is operated to introduce pressurized air into the cylindrical member 12. This air pressure is set so that the cross-section of the cylindrical member 12 is maintained circular even when embedded in uncured concrete, and the predetermined cross-sectional area can be maintained even if the cross-section is reduced by pressure from the outside. For example, it can be set to 0.3 to 0.4 MPa.
The air pressure can be appropriately set in consideration of the size of the through hole to be formed, the pressure acting on the uncured concrete, and the like.

  By introducing the pressurized air into the cylindrical member 12 in this way, the cross section of the cylindrical member 12 becomes substantially circular, and before placing the concrete, at the position supported by the support bar 3 in the mold 1. As shown in FIG. 2B, the lower part is supported while being sandwiched between the support bar 3 and the shape maintaining member 13. Then, a deflection occurs due to the weight of the cylindrical member 12 between the support bar 3 and the support bar 3, and the upper part is in contact with the upper part of the peripheral surface of the shape maintaining member 13 as shown in FIG. Is done. Therefore, as shown in FIG. 2A, the cylindrical member 12 does not maintain linearity within the mold and is deformed into a waveform.

As shown in FIG. 3A, concrete 4 is placed in the mold 1 in which the through-hole forming mold 11 is arranged in this manner. In the through hole forming mold 11 into which the pressurized air is introduced, buoyancy occurs in the uncured concrete 4 having fluidity. Therefore, between the support bars 3 and the support bars 3 (DD cross section in FIG. 4), the cylindrical member 12 is pushed upward, and the lower part of the cylindrical member 12 is shaped as shown in FIG. It can be held at a position in contact with the lower surface of the holding member 13. On the other hand, at the position supported by the support bars 3 (C-C cross section in FIG. 4), even if uncured concrete 4 is put into the mold 1, as shown in FIG. The position where the lower part of 12 contacts the outer peripheral surface of the shape holding member 13 is maintained. That is, the cylindrical member 12 is held at a position along the lower surface of the shape holding member 13 between the support bars 3 and the support bars 3 as in the position supported by the support bars 3, as shown in FIG. Following the linear shape holding member 13, the cylindrical member 12 is substantially linear.
In this way, the concrete 4 is cured until the cylindrical member 12 is substantially straight until it is cured.

  When the concrete 4 is hardened, as shown in FIG. 5A, the closing jig 14 attached to the end of the cylindrical member 12 is removed, and the pressurized air in the cylindrical member 12 is released, and the mold 1 To remove. Then, the shape holding member 13 is extracted from the end from which the closing jig 14 is removed. Since the shape holding member 13 is formed with a diameter smaller than that of the cylindrical member 12, it can be easily pulled out from the cylindrical member 12.

  The cylindrical member 12 remaining in the concrete member 5 formed by hardening the concrete 4 may be pulled out from the end portion, but when the concrete 4 is cured, the cylindrical member 12 is in close contact with the concrete 4. In some cases, it may be difficult to remove due to the adhesive force. That is, it is difficult for the cylindrical member 12 that is flexibly deformed to have a high tensile strength, and the tubular member 12 may be broken by being pulled strongly. In such a case, as shown in FIG. 5 (b), the end of the cylindrical member 12 is closed again by the closing jig 14 after the shape holding member 13 is extracted, and is sucked from the air pump through the base 15. Thus, a negative pressure is introduced into the cylindrical member 12. The tubular member 12 that can be deformed flexibly is deformed flat by negative pressure, and at least a part thereof is peeled off from the concrete 4 so that the adhesion between the tubular member 12 and the concrete 4 is reduced. Thereafter, as shown in FIG. 6, the closing jig 14 and the base 15 can be removed, the tubular member 12 can be pulled, and pulled out from the concrete member 5.

In the present embodiment, a tension material is inserted into the through hole formed in this way, and prestress is introduced into the concrete member. The tension material is fixed to the concrete member by the grout filled in the through hole, and the tension material can be tensioned and fixed as follows.
As shown in FIG. 7A, the tension member 21 is inserted into the through hole 6, the end of the tension member 21 is gripped, and a tension force is introduced into the tension member 21 by the jack 22. At this time, the reaction force of the tension force is applied to the concrete member 5 from the jack 22 via the jack chair 23. Supporting a state where a predetermined tension force is introduced into the tension member 21, the through-hole 6 through which the tension member 21 is inserted is closed by bonding of the shielding plate 24 or the like as shown in FIG. 6 is inserted with the grout hose 25. A grout 26 is injected from the grout hose 25 into the through hole 6 and hardened in the through hole 6. After the grout 26 is cured and integrated with the concrete member 5, the tension force by the jack 22 is released, and the tension force of the tension material 21 is applied to the adhesion force between the grout 26 and the tension material 21 and the adhesion force between the grout 26 and the concrete. Thus, the concrete member 5 is made to act and be fixed. Then, as shown in FIG.7 (c), the jack 22 and the jack chair 23 are removed, the edge part of the tension material 21 is cut | disconnected, and introduction of prestress is completed.

  In the present embodiment, the PC steel material 21 is used as the tension material 21, but a tension material using an aramid fiber or the like can also be used. When such a non-metallic tension material is used, the tension material can be fixed to the concrete member without using a metal wedge, etc., and damage to the tension material can be avoided, and corrosion of the fixing tool and the tension material can be prevented. There can be no structure.

Next, a through hole forming method according to another embodiment of the present invention will be described.
In this method, the same process is performed until the through-hole forming mold 11 is placed in the mold 1 and the concrete 4 is placed and the shape retaining member 13 is pulled out after curing.
In this embodiment, after releasing the pressurized air introduced into the cylindrical member 12 and pulling out the shape holding member 13 from the cylindrical member 12, the closing jig 14 is removed as shown in FIG. The extraction core 31 is inserted into the tubular member 12 from the end. The drawing core material 31 does not need to have great rigidity, and a material having a smaller cross section than the shape maintaining member 13 can be used. Further, it is desirable to use a member in which convex portions and concave portions are arranged in the axial direction on the outer peripheral surface, for example, a member in which node-like convex portions are arranged in the axial direction as shown in FIG. Etc. can be used.

  After inserting the drawing core 31 into the tubular member 12, the end of the tubular member 12 is closed again. At this time, the extraction core 31 may be closed so as to be accommodated in the cylindrical member 12, but as shown in FIG. 8B, the extraction core 31 is formed on the inner peripheral surface of the cylindrical member 12. It may be tightened by the fastening member 32 from the outside of the tubular member 12 so as to be pressed against the outer peripheral surface of the tubular member 12, and the space between the inside of the tubular member 12 and the drawing core 31 may be closed. The end portion closed in this way is dimensioned so that it can pass through the through-hole while maintaining the closed state.

  After closing the end where the drawing core 31 is inserted, as shown in FIG. 8 (b), suction is performed by an air pump through the base 15, and negative pressure is applied to the cylindrical member 12. As a result, the cylindrical member 12 is deformed to reduce its cross section, and the inner peripheral surface is pressed against the drawing core 31. As shown in FIG. 10, the drawing core material 31 is provided with irregularities on the outer circumferential surface, and the inner circumferential surface of the tubular member 12 is pressed against the drawing core material 31 so that the outer circumferential surface of the cylindrical member 12 is formed. Also, irregularities are generated, and a wide range of the outer peripheral surface of the cylindrical member 12 is peeled off from the inner peripheral surface of the through hole 6 provided in the concrete member 5. Then, as shown in FIG. 9, the end portion to which the base 15 is attached is tightened by the fastening member 33 from the outside of the tubular member 12 to close the space between the tubular member 12 and the outer peripheral surface of the drawing core 31. . Thereby, even if the vent pipe 17 into which the negative pressure is introduced is released, the state in which the cylindrical member 12 is pressed against the outer peripheral surface of the drawing core 31 is maintained. In this state, the pulling core 31 is gripped through the tubular member 12 and pulled out from the concrete member 5, whereby the tensile force is borne by the pulling core 31 and the tubular member 12 is pulled out. The cylindrical member 12 can be pulled out easily by being pulled out while being pressed against the tube.

The tubular member 12 can be pulled out together with the shape holding member 13 in place of the drawing core 31. That is, after the cast concrete 4 is hardened, the pressurized air is released without releasing the pressurized air and pulling out the shape retaining member 13, and then the tubular member is used as it is, as shown in FIG. A negative pressure is introduced into 12. Then, the tubular member 12 is pressed against the outer peripheral surface of the shape holding member 13 by negative pressure, and the end portion to which the base 15 is attached in this state is tightened with a tightening member 34 from the outside to The shape holding member 13 is brought into close contact with the outer peripheral surface. Thus, as in the embodiment shown in FIGS. 8 and 9, the shape holding member 13 is gripped via the cylindrical member 12, and the shape holding member 13 is moved to the cylindrical member as shown in FIG. 11B. 12 together with the concrete member 5.
Thus, when pulling out the cylindrical member 12 together with the shape holding member 13, it is desirable to set a large difference between the inner diameter of the cylindrical member 12 and the outer diameter of the shape holding member 13. Thus, when a negative pressure is introduced, a wide range of the outer peripheral surface of the cylindrical member 12 is peeled from the concrete member 5.

The present invention is not limited to the embodiment described above, and can be implemented with appropriate modifications within the scope of the present invention.
For example, the member used for the through hole forming mold may be any member other than those described above as long as it functions similarly. Moreover, in the said embodiment, although a through-hole formation type | mold is arrange | positioned at linear form, if curvature is constant, it can also arrange | position at curvilinear form.
In addition, the concrete member that forms the through hole by the method according to the present invention can be a bridge girder, a pillar or a beam of a building, and the bridge girder is provided with a through hole through which a tension material is inserted in the axial direction of the girder. It can be employed when a bridge slab having a box-shaped cross section is provided with a through hole through which a tension material is inserted in a direction perpendicular to the axis of the bridge girder.

1: Formwork, 2: Reinforcing bar, 3: Supporting bar, 4: Concrete, 5: Concrete member, 6: Through hole,
11: Through-hole forming mold, 12: Cylindrical member, 13: Shape holding member, 14: Closure jig (clip), 15: Base, 16: Tightening member, 17: Vent pipe,
21: tension material, 22: jack, 23: jack chair, 24: shielding board, 25: grout hose, 26: grout,
31: Core material for drawing, 32, 33, 34: Tightening member

Claims (4)

Assemble the formwork to form the concrete parts,
Insert a rod-shaped or cylindrical shape holding member having an outer diameter smaller than the inner diameter of the cylindrical member into the cylindrical member whose cross-sectional shape is flexibly deformed by the introduced air pressure,
The cylindrical member into which the shape maintaining member is inserted is placed on a support member provided at a predetermined interval and arranged at a predetermined position in the formwork, and both ends thereof are placed in the formwork. Project from the concrete placement area of
Introducing pressurized air into the tubular member;
The concrete is poured into the mold, the cross-sectional shape of the cylindrical member is substantially circular so that a space is maintained inside, and buoyancy that acts on the cylindrical member from uncured concrete is used. Maintaining the pressurized air in the tubular member so that the shape retaining member contacts the lower part of the inner peripheral surface;
After the concrete is hardened, the pressurized air in the tubular member is released,
A method for forming a through hole, wherein the shape holding member and the cylindrical member are pulled out from a hardened concrete member.   Introducing a negative pressure into the cylindrical member after curing of the concrete, peeling all or part of the outer peripheral surface of the cylindrical member from the concrete member, and drawing the cylindrical member out of the concrete member; The method for forming a through hole according to claim 1, wherein: After the concrete is hardened, the core material for drawing having a smaller outer diameter than the shape holding member by pulling out the shape holding member from the cylindrical member in a state where the shape holding member is inserted into the cylindrical member In a state of being inserted into the cylindrical member, a negative pressure is introduced into the cylindrical member,
While maintaining the state where the inner peripheral surface of the cylindrical member is pressed against the outer peripheral surface of the shape holding member or the extraction core by the negative pressure in the cylindrical member, the shape holding member or the extraction core The method for forming a through hole according to claim 1, wherein the cylindrical member is pulled out from the concrete member together with a material. The method for forming a through hole according to claim 3, wherein the drawing core material is a member having irregularities on an outer peripheral surface.

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