JP4708236B2 - Ready-made concrete pile with internal protrusion and method for manufacturing the same - Google Patents

Description

  The present invention relates to a ready-made concrete pile with an inner surface protrusion, which is mainly formed by centrifugal force, in the form of a protrusion formed on the inner peripheral surface of a pile body, and a method for manufacturing the same.

  As for ready-made concrete piles, centrifugally reinforced concrete piles (JIS A 5372 "centrifugal reinforced concrete piles") that use helical reinforcing bars and multiple axial reinforcing bars arranged in the axial direction of the pile as reinforcing bars Pretension type centrifugal force high strength prestressed concrete pile (JIS A 5373 “Pretension type centrifugal force high strength prestressed) using steel bars and PC steel materials that are arranged in the axial direction of the pile. Concrete piles)).

  These pre-fabricated concrete piles are placed in the form divided in half so that high compressive strength is given, and then the concrete is poured into the form to rotate the form around the axis, Generally, it is manufactured by centrifugal force molding in which concrete is compacted toward the peripheral surface of the mold (see Non-Patent Document 1). Since the poured concrete is consolidated while being drawn toward the formwork side, the finished concrete pile basically has a hollow cross section continuously in the axial direction.

  The ready-made concrete piles are used in a form that is embedded in the bulb formed by the ground improvement body, etc. in order to increase the tip support force, and is used in a form that ensures unity. It is necessary to form a protrusion for enhancing the effect of adhesion to the bulb (see Patent Documents 1 and 2).

  The integrity of the pile and bulb is obtained by joining the two so that the shearing force in the axial direction of the pile is transmitted between them, so that the protrusions are nodal and spaced apart on the inner surface of the pile. It is effective to be formed.

  However, since the ready-made concrete pile formed by centrifugal force as described above is finished in a continuous shape in the axial direction, it is difficult to form a nodular projection on the inner surface of the pile during molding. In order to form the steel pipe, after forming the pile, a steel pipe or the like with protrusions must be joined to the end plate embedded at the tip (see Patent Document 3).

  In order to weld or bolt a steel pipe with projections to a molded pile, the molded pile body must be finished with the dimensions as designed, and the dimensions of both the pile and the steel pipe must match. For piles formed by force molding, manufacturing errors are allowed for each outer diameter and thickness (JIS A 5372 “Centrifuged reinforced concrete pile”, JIS A 5373 “Pretensioned centrifugal force high strength prestressed Concrete piles ”), this error may prevent steel pipes from joining.

  According to the above document that specified the error, positive and negative (+-) errors are allowed in the outer diameter of the pile body after molding, but negative errors are not allowed in the thickness dimension. Since the pile body is often finished with a thickness equal to or greater than a certain dimension, the inner diameter is different for each pile.

  If a steel pipe with a projection is inscribed in a pile having different inner diameters as in Patent Document 3, a steel pipe in which steel material is integrated on the inner peripheral surface is prepared for each outer diameter dimension of the pile. However, since it is difficult and expensive to integrate the steel material into the inner peripheral surface of the steel pipe, it is extremely uneconomical to prepare a steel pipe for each inner diameter of the pile.

  Also, if a steel pipe with a steel projection on the inner peripheral surface is welded to the end plate of the pile, there is no pile inside the steel pipe, so a thick steel pipe must be used so that the steel pipe does not deform. Without getting high price. In addition, since welding is performed on the peripheral surface of the pile, welding is likely to be insufficient, and there is a risk that the steel pipe may fall off during use. For this reason, a pile in which a steel pipe is integrated with the inner peripheral surface of the tip of the pile has not been put into practical use.

  On the other hand, there is a method of forming convex portions that are continuous in the circumferential direction of the pile by placing a convex-shaped ring-shaped protruding portion on the inner peripheral surface of the formwork and performing centrifugal force molding (see Patent Document 4). ) As long as it is centrifugal force molding, the convex portion is formed on the outer periphery of the pile.

Tatsuo Aoki and Kensaburo Takeyama, “Concrete Pile Handbook”, First Edition, Concrete Pole and Pile Association, August 25, 1966, p. 297, 300 Japanese Utility Model Publication No. 62-81634 (Claim 1, FIGS. 1 to 3) Japanese Utility Model Publication No. 5-21530 (Claim 1, FIGS. 1 to 3) JP-A-55-119822 (Claim 2, FIGS. 2 to 4) Registered Utility Model No. 3061939 (Claim 1, FIG. 1)

  As described above, in the ready-made concrete pile, a pile having a protrusion on the outer peripheral surface is known, but a pile having a protrusion on the inner peripheral surface is not known, in order to provide a protrusion on the inner peripheral surface side. It has only been proposed to mount a steel pipe with a protrusion on the inner surface of the lower end of the pile or on the lower end of the pile. Thus, if the protrusion is present on the inner peripheral surface and the protrusion does not easily fall off, the protrusion is present on the inner peripheral surface of the pile. The unity with the root-fixing bulb can be ensured.

  However, there is a problem as described in paragraphs 0009 and 0010 in mounting a steel pipe having a protrusion on the inner surface of the lower end of the pile or the lower end of the pile, and it has not been put into practical use. On the other hand, in the method of Patent Document 4, the protrusion cannot be formed on the inner peripheral surface of the pile.

  From the above background, the present invention proposes a ready-made concrete pile with an inner surface protrusion and a method of manufacturing the same, in which protrusions can be formed on the inner peripheral surface of the pile by centrifugal force molding.

It pre-cast concrete pile according to claim 1, the inner peripheral surface of the distal end of the pile body, projections projecting into the inner peripheral side is formed, only the projecting portion is a concrete pile projecting from the concrete surface Is a basic configuration requirement. The protrusion is formed by embedding an annular member (fixing material) in advance in a mold for molding a concrete pile as described later, and continuously or intermittently projects in the circumferential direction of the pile body. .

The projecting part is a concrete pile by injecting concrete into the mold and forming it by centrifugal force with the annular member such as steel plate or other steel material held in a bar such as a reinforcing bar. Is formed at the same time as the molding. It is possible to form the protrusions with the steel material or the like by setting in advance so that the steel material or the like protrudes from the inner peripheral surface of the pile body, that is, the steel material or the like is not completely embedded in the concrete. Specific to the annular fixing member in the partially protruding portion by fixing the mold frame so as to protrude from the concrete is formed.

The protrusion is formed by projecting a part of the annular fixing material embedded in the concrete of the pile body from the inner peripheral surface of the pile body. Annular fixing member is embedded in the concrete in the portion of the outer periphery toward, it protrudes from the inner circumferential surface of the concrete in the portion of the inner circumference closer, portion projecting becomes projections. As described above, since the portion near the outer periphery of the annular fixing material is embedded in the concrete and the ready-made concrete pile is molded, there is no situation where the protrusion is dropped.

Ready-made concrete piles are obtained as follows. The fixing material is held in the formwork by a bar material embedded in the concrete of the pile body being inserted into the concrete through the fixing material. Here, if at least the bar is fixed to the end plate at the tip of the pile body, the axial movement does not occur, and the rod moves through the fixing material, so that the radial movement of the fixing material is also restrained. Therefore, stability in the axial direction and the radial direction of the fixing material at the time of centrifugal force molding is ensured. By fixing the fixing material in the concrete as it is, the portion near the inner periphery protrudes from the concrete to form a protrusion. Since the fixing material is stable in the concrete, the placement accuracy of the fixing material after molding is also improved.

After completion of the ready-made concrete pile, the bar material that has been inserted through the fixing material is buried and fixed in the concrete, so that when the ready-made concrete pile is used, the fixing material receives a vertical upward force from the bulb. Stability against slipping out of the material is improved. At the same time, the shear force from the bulb can be transmitted to the ready-made concrete pile and shared with the ready-made concrete pile.

In claim 1 by projections from the inner peripheral surface of the distal end portion of the prefabricated concrete pile to be completed projects, without the diameter of the bulbs was particularly larger than the outer diameter of the pile body, ensuring the integrity of the bulbs It becomes possible to do. Compared with the case where a protrusion that requires a bulb having a diameter larger than the pile diameter is formed on the outer periphery of the pile body, the present invention can reduce the diameter of the bulb, thereby reducing the cost required for constructing the bulb itself. It is also possible to install adjacent piles close to each other.

While projection in claim 1 (fixing member) is continuously in the circumferential direction on the inner peripheral surface of the pile body, or to protrude intermittently, the pile body as shown in FIG. 5 integral with the bulbs When placed in use and bears a vertical load, the protrusion receives a vertically upward force from the bulb as described above. At this time, the ground improvement body that constitutes the bulb receives a compressive force from below and is constrained by the concrete pile at the periphery, so that it becomes a triaxial stress state. A pressing force is generated in the direction.

  This force causes the concrete pile to bulge outward, so that it follows the deformation of the concrete and, for example, the protrusion (fixing material) that originally formed a horizontal plane tends to incline. If the protrusions are inclined, the tendency of the concrete piles to swell is promoted because the component in the thickness direction of the protrusions faces the outer peripheral side of the piles in the vertically upward force acting on the protrusions. . As a result, a tensile force acts on the outer peripheral surface of the concrete pile, which may cause cracks in the concrete.

For this situation, the outer periphery of the pile body as claimed in claim 2, of the section in which projections are formed, by reinforcing plate portion of the section of at least the tip side surrounds Since the tip of the pile body can be restrained from the outer peripheral surface, it is possible to prevent the concrete from protruding. In addition, since the tensile force can be applied to the reinforcing plate, it is possible to prevent the occurrence of cracks.

The ready-made concrete pile according to claim 1 or 2 , wherein the fixing material is embedded in the concrete, and the concrete is placed in the formwork in a state where the fixing material is disposed in the formwork as described in claim 3. It is manufactured by injecting, rotating the mold and applying centrifugal force.

The fixing material is fixed to the mold frame by fixing the bar material to the end plate, and the outer periphery of the fixing material is held from the periphery by the reinforcing bars arranged in the concrete, thereby obtaining stability during molding.

  The projecting part protrudes from the inner peripheral surface of the tip of the finished ready-made concrete pile, so that when it is integrated with the bulb, the integrity of the bulb is not required even if the diameter of the bulb is not significantly larger than the outer diameter of the pile body. Can be secured. Contrary to the case where protrusions that require bulbs larger in diameter than the pile diameter are formed on the outer periphery of the pile body, the bulb diameter does not have to be larger than the outer diameter of the pile body. Cost can be reduced, and adjacent piles can be installed close to each other.

Since some of the annular anchoring material embedded in concrete is a prefabricated concrete pile with a structure protruding from the inner peripheral surface of the pile body, it is necessary to prepare a steel pipe with a protrusion on the inner peripheral surface as in the past , There is no need for welding, and the risk of dropout due to welding is eliminated. As described above, since the portion near the outer periphery of the annular fixing material forming the protrusion is embedded in the concrete, the protrusion does not fall off as in the prior art.

Since the rod material embedded in the concrete of the pile body is inserted into the fixing material and embedded in the concrete, the fixing material is held in the formwork, so the axial movement and radial movement of the fixing material are restrained. The ready-made concrete pile can be formed in a state, and the integrity of the fixing material and the pile body can be enhanced.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  1- (a) and (b) are pre-tension type centrifugal force high strength prestressed using a prestressed concrete pile 1 and a PC steel material for applying prestress as a main reinforcement 3 and a helical rebar 4 for restraining it. An example of manufacturing a concrete pile (PHC pile) is shown. In this ready-made concrete pile 1, a protrusion 7 is formed on the inner peripheral surface on the front end side of the pile body 2 so as to project to the inner peripheral side. The pile main body 2 refers to a portion made of reinforcing steel and concrete 5 in the ready-made concrete pile 1. (A) shows the longitudinal cross-section of the ready-made concrete pile 1 with an internal surface protrusion, (b) shows the cross section of an AA line.

  In addition to the concrete 5, the pile body 2 includes a PC steel material as a tension material that is the main reinforcement 3 arranged in the axial direction, and a helical rebar 4 arranged in the circumferential direction on the outer peripheral side of the main reinforcement 3. An end plate 6 serving as a dam plate on the end face side of the concrete 5 is disposed at the tip position of the pile body 2. In the illustrated example, a friction cutter 61 is welded to the end plate 6 after the ready-made concrete pile 1 is molded. The friction cutter 61 is added to reduce the frictional force between the outer peripheral surface of the pile body 2 and the hole wall when the ready-made concrete pile 1 is buried, and is not necessarily required in the present invention.

  As shown in FIG. 1, the protrusion 7 is formed, for example, by embedding a part of the annular fixing member 8 near the outer periphery in the concrete 5 and projecting a part on the inner peripheral side from the inner peripheral surface of the pile body 2. The In FIG. 1, a tension member 9 such as a PC steel material that applies prestress to the concrete 5 is used as the main reinforcement 3. Therefore, the fixing member 8 is fixed using a bar 10 different from the main reinforcement 3. This is because if the tension material 9 is inserted through the fixing material 8, it becomes difficult to tension the tension material 9 and apply prestress to the concrete 5.

  The fixing material 8 is preferably a flat iron plate (steel plate). Specifically, as shown in FIG. 3B, an annular plate in which the center of the disc is mainly hollowed is used. The fixing material 8 is arranged at one place in the axial direction of the pile body 2 or at a plurality of places at intervals in the axial direction as shown. The fixing member 8 is fixed to the rod member 10 with a nut 11 or by welding. As shown in FIG. 1- (b), the fixing material 8 has an annular shape having an outer diameter that is inscribed in the plurality of main reinforcing bars 3 or the tension material 9, so that the fixing material 8 is attached to one fixing material 8 and has a plurality of The bar 10 is inserted.

  For example, a reinforcing bar is used for the bar 10. The bar 10 is positioned in the concrete 5 by welding to the end plate 6 on the front end side of the pile body 2 or joining with the nut 11. As described above, the fixing material 8 is formed with an insertion hole through which the bar 10 is inserted.

  Since the portion above the tip (end plate 6) side of the bar 10 is fixed to the tension member 9 by the fixing material 8 bonded thereto, the radial distance of the pile body 2 is kept constant. 10 is positioned in the mold even if it is not connected to the main reinforcement 3 or the like. Further, since the ready-made concrete pile 1 is subjected to centrifugal force molding, a radially outward force acts on the bar 10 and the fixing material 8, and the fixing material 8 is stretched on the main reinforcement 3 and the tension material 9 located on the outer peripheral side. Since it is kept in the attached state, stability is not impaired. The bar 10 only needs to be restrained against movement in the axial direction.

  For example, the ready-made concrete pile 1 has a main bar 3 or a tension member 9 in an axial direction and a helical rebar 4 in the outer peripheral side of the main bar 3 or the like in a mold formed by dividing a cylinder into two along an axis. In the state where the fixing material 8 is arranged inside the main reinforcement 3 and the tension material 9 and the bar material 10 is joined to the end plate 6 arranged at the distal end position of the pile body 2, the mold 5 is poured while the concrete 5 is injected. Centrifugal force molding is performed by rotating the frame around its axis. If the movement of the bar 10 in the axial direction can be constrained, the bar 10 may be bound to the main reinforcement 3 or the tension material 9 with a wire, but to reliably restrain the movement of the bar 10 in the axial direction, As described above, it is preferably fixed to the end plate 6 by welding or the like.

  Since the fixing material 8 has an annular shape along the cross-sectional shape of the pile body 2, if it is arranged in a form inscribed in the plurality of main bars 3 and the tension material 9 as shown in FIG. Property is ensured, and no misalignment occurs during molding. In addition, as shown in FIG. 2A, the fixing material 8 is arranged so that the outer peripheral surface of the fixing material 8 is in contact with the main reinforcement 3 and the tension material 9, so that the fixing material 8 can be used when the mold is rotated. There is no rampage within.

  In forming the ready-made concrete pile 1, the main reinforcement 3, the diameter of the tension material 9, the outer diameter and the inner diameter of the fixing material 8 have the sizes as designed, and the inner peripheral portion of the fixing material 8 is made of the concrete 5. If the outer diameter of the pile main body 2 and the cover of the main bar 3 and the tension material 9 are accurately secured, the thickness of the pile main body 2 will have an error. In addition, it is possible to obtain a state in which the inner peripheral portion of the fixing material 8 protrudes from the inner peripheral surface of the concrete 5.

  According to the above-mentioned JIS A 5372 and the like, there is an allowable error in the outer diameter dimension of the pile body 2 and there is no allowable value in the thickness dimension. As shown in 2- (a), the embedding depth d when the fixing material 8 is embedded in the concrete 5 may be a certain value or more.

  On the contrary, the protrusion width h of the fixing material 8 may be a certain value or less. However, by giving a sufficient size to the width (d + h) of the cross section of the fixing material 8 itself, the fixing material 8 is completely formed. The situation of being buried in the concrete 5 is avoided. FIG. 2B shows the state of the shearing force acting on the protrusion 7 which is a portion protruding from the concrete 5 of the fixing material 8.

  The effect of integration of the ready-made concrete pile 1 and the bulb increases as the protrusion width h of the fixing material 8 from the inner peripheral surface of the concrete 5 increases, but the portion protruding from the concrete 5 (projection 7) is integrated with the bulb. Since the vertical upward load is received from the bulb in the converted use state, if the protrusion width h is increased, the portion is easily plastically deformed or broken.

  Further, if the number of fixing materials 8 integrated in the pile body 2 is large, the load to be borne by the fixing material 8 per sheet is small. However, when the number of the fixing materials 8 is small, the protrusion of the fixing material 8 described above is small. When the width h becomes larger than a certain value, the protruding portion of the fixing material 8 is easily plastically deformed. Although the deformation can be suppressed by increasing the thickness t of the fixing material 8, it is uneconomical.

  Specifically, if the protrusion width h of the fixing material 8 exceeds 40 mm, the fixing material 8 tends to be deformed by the load received by the protruding portion, and the surrounding concrete 5 responsible for the load may be crushed. .

  Furthermore, when carrying out the intermediate digging method for excavating through the inside of the ready-made concrete pile 1, a spiral auger having a diameter of about 70 to 100 mm smaller than the inner diameter of the ready-made concrete pile 1 is used, but the screw is fixed when the spiral auger is rotated. It is also necessary not to collide with the material 8.

  From the above points, it can be said that the maximum value of the protrusion width h of the fixing material 8 is about 30 mm or less.

  Conversely, if the protrusion width h of the fixing material 8 is reduced, the risk of plastic deformation of the fixing material 8 and the accompanying collapse of the concrete 5 is reduced, but the effect of integration with the bulb is also reduced. Therefore, the number of fixing members 8 to be arranged must be increased. In that case, since the ready-made concrete pile 1 has to be inserted deeply into the bulb, it is necessary to increase the length of the bulb accordingly, which is not reasonable. From this point, it can be said that the minimum value of the protrusion width h of the fixing material 8 is about 10 mm or more.

  Further, when the ready-made concrete pile 1 is subjected to centrifugal force molding as described above, there is no limit on the positive side error in the thickness dimension of the concrete 5, so that the thickness of the finished ready-made concrete pile 1 is larger than the target thickness. In view of this, it is appropriate that the protrusion width h of the fixing material 8 is 20 mm or more.

  Taking the above points together, it can be said that the protrusion width h of the fixing material 8 is suitably in the range of 10 to 30 mm, and optimally in the range of 20 to 30 mm.

  The thickness t of the fixing material 8 is determined by a bending stress caused by a shearing force acting on a portion of the fixing width 8, that is, a portion of the fixing material 8 protruding from the concrete 5 (projecting portion 7). If the thickness is 25 mm, the appropriate thickness t is about 15 to 25 mm.

  1 and 3 show an example in which the protruding portion of the fixing material 8 continuously protrudes in the circumferential direction of the pile body 2, and the fixing material 8 in this case is as shown in FIG. A ring with a certain width in the circumferential direction is used.

  FIG. 4 shows an example in which the protruding portion of the fixing material 8 intermittently projects in the circumferential direction of the pile body 2. In this case, the fixing material 8 is formed in a shape in which a circular ring having a constant width in the circumferential direction is partially cut out, or a circular plate is added to a circular ring having a fixed width. The fixing material 8 is completely embedded in the concrete 5 at a portion other than the notched portion or the added portion, and protrudes from the concrete 5 at the other portion.

  In the case of FIG. 4, the protruding portion from the concrete 5 is discontinuous in the circumferential direction of the fixing material 8, and therefore, the fixing material 8 adjacent to the axial direction between the fixing material 8 and the mold frame at the time of centrifugal force molding, The filling property of the concrete 5 between 8 is improved, and the ready-made concrete pile 1 having a uniform strength in the axial direction becomes easier to manufacture. In addition, since the filling of the concrete 5 is not hindered by the fixing material 8, it becomes easy to ensure the accuracy of the thickness of the concrete 5 and the accuracy of the protrusion width h of the fixing material 8.

  FIG. 5 shows that the fixing material 8 receives a vertically upward force from the bulb 12 integrated with the tip portion of the ready-made concrete pile 1, and accordingly, the concrete 5 enters a part of the bulb 12 entering the inside of the ready-made concrete pile 1. A state when the pressure acts radially outward is shown. The ground improvement body etc. which comprise the bulb 12 penetrate | invade to the level which embeds the uppermost fixing material 8 in the inside of the ready-made concrete pile 1. FIG. In FIG. 5, a reinforcing plate 13 made of a steel pipe or the like is wound around the outer periphery of the concrete 5 in order to reinforce the concrete 5 against pressure that tends to swell into the concrete 5 due to the force received from the bulb 12.

  FIG. 6 shows the state of the test for confirming the change in the maximum compressive force (maximum load) acting on the ready-made concrete pile 1 due to the difference in the number (stages) of the fixing members 8 assuming the situation of FIG.

In the test, a mortar 15 having a compressive strength of 20 N / mm ² is filled in the test body 14 corresponding to the ready-made concrete pile 1 with a gap at the lower end, and a receiving plate 16 is added to the tip (lower end) side. With the loading plate 17 arranged on the force side, a compressive load was applied from above the loading plate 17, and the load when the internal mortar 15 was pulled out toward the receiving plate 16 was evaluated as the maximum load. The test body 14 has an outer diameter of 600 mm and an inner diameter of 400 mm, and the fixing material 8 has an inner diameter of 370 mm. The relationship between the number of steps of the fixing material 8 and the maximum load is shown in Table 1, and a graph is shown in FIG.

  From Table 1 and FIG. 7, the maximum load is doubled by the presence of the fixing material 8, and when the embedding depth d, the protruding width h, and the thickness t of the fixing material 8 are constant, the number of steps of the fixing material 8 is large. It can be seen that the maximum load increases. The greater the maximum load, the greater the tip support force of the solidified ready-made concrete pile 1.

  FIG. 8 shows that the concrete 5 of the ready-made concrete pile 1 is subjected to a pressure to expand to the outer peripheral side by the compressive force from a part of the bulb 12 entering the inside of the ready-made concrete pile 1 as shown in FIG. In order to prevent the concrete pile 1 from opening at the tip, a reinforcing plate 13 made of a steel pipe or the like is wound around the tip of the ready-made concrete pile 1.

  Although the reinforcing plate 13 may be continuously arranged over the section where the fixing material 8 is arranged as in FIG. 5, the concrete 5 near the end plate 6 is constrained intensively, and the concrete in that portion By applying a tensile force acting on the surface of 5, the opening of the tip of the concrete 5 can be prevented. As a result, an effect of reinforcing the concrete 5 above the reinforcing plate 13 is also produced, so that generation of cracks can be prevented. In FIG. 8, a reinforcing member 18 such as a reinforcing bar is further disposed around the reinforcing plate 13. The reinforcing members 18 are arranged in one stage or a plurality of stages as shown.

  The reinforcing plate 13 may be retrofitted by being welded to the end plate 6 after the ready-made concrete pile 1 is molded. It can be integrated into the concrete 5 only by being molded. Similarly, the reinforcing member 18 is retrofitted to the reinforcing plate 13 and is previously integrated with the reinforcing plate 13 by welding.

(A) is the longitudinal cross-sectional view which showed the front-end | tip part of a ready-made concrete pile, (b) is the sectional view on the AA line of (a). (A) is an enlarged view of the broken-line circle part of FIG. 1- (a), and (b) is an explanatory view showing the relationship between the fixing material and the shearing force. (A) is the cross-sectional perspective view which showed a mode that the fixing material protruded continuously on the internal peripheral surface of concrete, (b) is the perspective view which showed the fixing material used by (a). (A) is the cross-sectional perspective view which showed a mode that the fixing material protrudes intermittently on the internal peripheral surface of concrete, (b) is the perspective view which showed the fixing material used by (a). It is the longitudinal cross-sectional view which showed the relationship of the force which acts on the inside of the ready-made concrete pile integrated with the bulb. (A) is the longitudinal cross-sectional view which showed a mode that the relationship between the ready-made concrete pile of FIG. 5 and a bulb was modeled, (b) is a horizontal sectional view of (a). It is the graph which showed the relationship between the step number of the fixing material when a compressive force is applied to the mortar inside the ready-made concrete pile in FIG. 6, and the maximum load. It is the partial cross section elevation which showed a mode that the reinforcement board and the reinforcing material were wound around the front-end | tip part of a ready-made concrete pile.

Explanation of symbols

1 ……… Prefabricated concrete pile 2 ……… Pile body 3 ……… Main reinforcement 4 ……… Helical rebar 5 ……… Concrete 6 ……… End plate 61 …… Friction cutter 7 ……… Projection 8 …… ... Fixing material 9 ... Tension material 10 ... Bar material 11 ... Nut 12 ... Bulb 13 ... Reinforcement plate 14 ... Specimen 15 ... Mortar 16 ... Receiving plate 17 ... Loading plate 18 ... Reinforcement Material

Claims (3)

In the concrete pile in which a protrusion protruding to the inner peripheral side is formed on the inner peripheral surface on the tip side of the pile body, and only this protrusion protrudes from the concrete surface ,
The protrusion is embedded in the concrete of the pile main body, and a part of an annular fixing material having an outer diameter inscribed in a main reinforcing bar arranged in the axial direction of the pile main body or a tension material is included in the pile main body. Formed protruding from the inner peripheral surface,
The fixing material is a ready-made concrete with an inner surface protrusion , wherein a bar fixed to an end plate disposed at the tip end position of the pile body is inserted and embedded in the concrete in a fixed state Pile. 2. The inner plate with protrusions according to claim 1 , wherein a reinforcing plate surrounds at least a part of the outer periphery of the pile main body on the tip side among the sections where the protrusions are formed. Ready-made concrete piles. An inner surface protrusion for producing a ready-made concrete pile according to claim 1 or 2 , wherein concrete is poured into the mold and the mold is rotated in a state where the fixing material is disposed in the mold. A manufacturing method for ready-made concrete piles.

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