JP6336850B2 - Pile head reinforcement method for foundation pile - Google Patents

Description

  The present invention relates to a pile head reinforcement method for a foundation pile serving as a foundation for an upper structure.

  In the Great Hanshin-Awaji Earthquake and the Great East Japan Earthquake, there were accidents such as the foundation piles of buildings etc. being damaged by the great earthquake force, and the buildings collapsed or tilted. According to surveys by various organizations, it has been found that most of these accidents were caused by pile head damage. The cause is that the strength of the pile head (including the upper part of the pile and the joint between the pile head and the footing) is insufficient, or the seismic force is higher than expected in the design.

  On the other hand, in recent years, various pile construction methods have been developed, and a number of construction methods having a greater vertical support force than before have been developed. However, since the horizontal load also increases in proportion to the vertical load acting on the pile, the design may not be able to cope with the bending moment of the pile head. As a result, the large vertical bearing force of the foundation pile may not be used effectively. It has been found that this tendency is particularly strong when the ground near the pile head is soft.

  In view of the above, various techniques for reinforcing the pile head have been proposed. For example, a construction method using a cylindrical casing having a diameter larger than that of a steel pipe pile has been proposed (see Patent Document 1). In this construction method, first, the cylindrical casing penetrates into the ground and then excavates the earth and sand inside the cylindrical casing, forming a space inside the cylindrical casing, and then placing a steel pipe pile in the center of this space, The steel pipe pile is rotated and penetrated into the ground, then a reinforcing bar is inserted between the outer peripheral surface of the steel pipe pile and the inner peripheral surface of the cylindrical casing, and then the outer peripheral surface of the steel pipe pile and the inner peripheral surface of the cylindrical casing are Concrete is laid in between, and then the cylindrical casing is pulled out from the ground to reinforce the pile head with reinforced concrete.

  As another construction method, a construction method using a Yatco that includes an outer frame body that expands the ground and a guide that holds the pile core of the steel pipe pile substantially in line with the rotation center of the Yatco is also proposed. (See Patent Document 2). In this construction method, the pile core of the steel pipe pile is first held approximately in line with the center of rotation of the Yatco, then the steel pipe pile is buried in the ground and the outer periphery of the steel pipe pile is expanded and excavated. The pile head of the steel pipe pile is reinforced with the ground improvement material by pulling up the Yatco and placing a ground improvement material in the expanded excavated part.

JP 2005-232694 A JP 2011-117216 A

  In the former construction method, a heavy machine (in-pipe excavator such as a crane and a hammer grab) different from the pile driving machine is required for excavation work in the casing, and there is a problem that residual excavation soil is generated.

  In the latter construction method, although excavation residual soil does not occur, it is necessary to penetrate the support layer penetration of the steel pipe pile and the Yatco with the outer frame at the same time, and it is actually difficult to construct. Even normal steel pipe piles require a torque that is close to the capacity of the construction machine to penetrate the support layer, but in this construction method, in addition to this, it is necessary to add a large torque to penetrate the outer frame body with a large diameter, As the pile driver increases in size, the required torque exceeds the allowable torsional torque of the pile body, and there is a strong risk that construction will not be possible. Further, not only a torque problem but also a propulsion problem occurs. The blades for rotational penetration generate a propulsive force that pushes the pile downward, but a very large propulsive force is required to penetrate the outer frame with a large diameter, and only the propulsive force of the vanes provided on the steel pipe pile However, there is a risk that the steel pipe pile will run around. Furthermore, even if the pile head is reinforced with ground improvement material (actually cement milk or concrete), there is no reinforcing bar, so cracks occur during earthquakes where a large horizontal force acts, and a highly reliable reinforcement effect is obtained. There is a problem that cannot be done. Furthermore, in this latter construction method, there is a problem that reinforcing bars cannot be put in the ground improvement material.

  The present invention may require a heavy machine different from the pile driving machine, generate excavation residual soil, or may cause the torque required to rotate the Yatco to exceed the allowable torsional torque of the foundation pile and may not be able to be constructed. An object of the present invention is to provide a pile head reinforcement method for a foundation pile that can effectively reinforce the pile head of the foundation pile without causing any problems.

  The pile head reinforcement method for a foundation pile according to claim 1 of the present invention is a pile head reinforcement method for a foundation pile embedded in the ground, and a curable fluid is provided around the pile head of the foundation pile. A cylindrical body that forms a space for constructing a reinforcing body containing a reinforcing bar rod, a blade having a screwing action provided on the outer peripheral surface of the cylindrical body, and the pile head penetrates A drilling pipe having a through hole and a bottom lid that is detachably attached to the bottom of the cylindrical body and closes the bottom, and the pile head enters the space through the through hole. Rotating and penetrating step of rotating and penetrating the excavation pipe into the construction ground where the foundation pile is embedded until the bottom cover is positioned at the lower end of the reinforcing section partitioned into the construction ground by the reinforcing body, Before the rotation penetration step or after the rotation penetration step, the empty space around the pile head An installation step of installing the rebar rod in, a placement step of placing the curable fluid in the space around the pile head, and the construction of the excavation pipe leaving the bottom lid And a removal process for removing from the ground.

  According to the present invention, a blade having a screwing action is provided on the outer peripheral surface of a cylindrical body, a bottom cover having a through hole is detachably attached to the bottom of the cylindrical body, and a closed excavation pipe is used. Since the pipe is rotated and penetrated into the construction ground where the foundation pile is buried, the pile head of the foundation pile is penetrated into the space of the excavation pipe through the through hole. No heavy machinery is required, no excavation remains are generated, and the excavation pipe is rotated and penetrated into the ground of the foundation pile that has already been penetrated by rotation. There is no possibility that the allowable torsional torque exceeds the allowable torque. In addition, the reinforcement body is constructed by installing a reinforcing bar in the space of the excavation pipe and placing a curable fluid, so the combined effect of the reinforcement body and the foundation pile is several times greater than that of the foundation pile alone. It can exhibit rigidity and bending / shearing strength, and can greatly enhance the strength of the pile head, and can effectively utilize the vertical support force of the foundation pile, which makes it possible to generate bending at the pile head of the foundation pile. Moment and horizontal displacement can be greatly reduced (by a fraction), and the pile diameter can be reduced by design. Further, by extending the reinforcing bar to the footing, the reinforcing body and the footing are integrated, the force transmission between both becomes smooth, and the reliability of the pile head joint is greatly improved. Furthermore, the heavy machinery to be used is a pile driving machine alone, and a reinforcing body can be constructed around the pile head of the existing pile, so that construction can be performed at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory sectional drawing which shows schematically the construction procedure in one Example of the pile head reinforcement construction method of the foundation pile of this invention, (a) is explanatory sectional drawing which shows the construction process of a foundation pile, (b) is an excavation pipe Explanatory cross-sectional view showing the erection process, (c) is an explanatory cross-sectional view showing the rotational penetration process of the excavating pipe, (d) is an explanatory cross-sectional view showing the step of installing the reinforcing bar, and (e) is an injection of the curable fluid Explanatory sectional drawing which shows an installation process, (f) is explanatory sectional drawing which shows the removal process of an excavation pipe. BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory sectional drawing which shows schematically the construction procedure in the other Example of the pile head reinforcement construction method of the foundation pile of this invention, (a) is explanatory sectional drawing which shows the construction process of a foundation pile, (b) is an excavation pipe (C) is an explanatory cross-sectional view showing the rotational penetration process of the excavating pipe, (d) is an explanatory cross-sectional view showing the placing process of the curable fluid, (e) is an excavating pipe It is explanatory sectional drawing which shows this removal process. The excavation pipe used by the pile head reinforcement method of the foundation pile shown in FIG. 1 or FIG. 2 is shown, (a) is a perspective view, (b) is an enlarged longitudinal sectional view partially omitted. An example of a through hole when a rotating bracket that transmits the rotational force of the pile driver is attached to the foundation pile, (a) is a side view of the pile head portion of the foundation pile with the rotating bracket attached, (b) is ( It is a top view of the through hole formed so that the rotation metal fitting shown to a) may pass. It is explanatory drawing which shows an example which attaches a bottom cover to the bottom part of a cylindrical body so that attachment or detachment is possible, (a) is a description perspective view which abbreviate | omitted one part of the cylindrical body which provided the notch in the bottom part, (b) is a processus | protrusion which fits into a notch | incision FIG. 4C is an explanatory side view of the bottom cover provided with a, and FIG. 4D is an explanatory partial side view showing a state in which the protrusion of the bottom cover is fitted in the cut of the cylindrical body. It is explanatory sectional drawing which shows an example of the method of removing a bottom cover from the excavation pipe which attached the bottom cover removably as shown in FIG. 1 or 2 shows a reinforcing body containing a reinforcing bar made of a curable fluid formed by a pile head reinforcement method for a foundation pile shown in FIG. 1 or 2, wherein (a) is a longitudinal sectional view, and (b) is a transverse sectional view. is there. FIG. 7 shows a modified example of the reinforcing body containing the reinforcing bar shown in FIG. 7, (a) is a longitudinal sectional view of the reinforcing body using the reinforcing bar having a height protruding from the upper end of the pile head, and (b) is ( It is a longitudinal cross-sectional view of the state which wound the reinforcing bar rod on the reinforcement body shown to a), and formed the footing. FIG. 7 is a partially cutaway side view showing a first modification of the excavation pipe of FIG. 3. The 2nd modification of the excavation pipe | tube of FIG. 3 is shown, (a) is a back view of a bottom cover part, (b) is the side view partly notched. FIG. 1 or FIG. 2 shows a first modification of the pile head reinforcement method for foundation piles, in which (a) can continue to use the yatco used when constructing foundation piles to guide the rotation penetration of excavated pipes. FIG. 5 is a partially longitudinal cross-sectional view for explaining a state in which rotation penetration of the excavation pipe is started by being guided by the double-use guide. Fig. 1 or Fig. 2 shows a second modification of the pile head reinforcement method for foundation piles. Fig. 1 (a) shows a pile that penetrates the excavation pipe into the ground and then penetrates the excavation pipe through the through hole in the bottom cover. Cross-sectional view for explaining the state in which mud adhering to the peripheral surface of the head is removed with a brush, (b) is an explanation for explaining the state in which mud is removed by spraying water from a nozzle instead of the brush in (a) It is sectional drawing.

  Excavation pipes used in an embodiment (see FIGS. 1 and 2) of the pile head reinforcement method for a foundation pile according to the present invention will be described with reference to FIGS. 3 (a) and 3 (b). The excavation pipe 10 is a tubular body 11 made of steel pipe, a blade 12 having a screwing action attached to the outer peripheral surface of the tubular body 11, and a detachable attachment to the bottom of the tubular body 11 to close the bottom. And a bottom lid 13.

  The cylindrical body 11 is provided with a curable fluid 20 (see FIGS. 1, 2 and 9) around a pile head B of a foundation pile A (see FIGS. 1 and 2) penetrating into the construction ground. The space 14 for doing this is formed. A reinforcing body 22 containing a reinforcing bar 21 is constructed by the curable fluid 20. The inner diameter and axial length (height) of the cylindrical body 11 are set based on the dimensions of the reinforcing body 22 to be constructed. The outer diameter of the reinforcing body 22 is set to, for example, 2 to 4 times the outer diameter of the foundation pile A, and the axial length (height) depends on the hardness of the ground near the pile head B, for example. Is set to 3 to 6 times the outer diameter of the reinforcing body 22. Then, the inner diameter of the cylindrical body 11 is set to be the same as the outer diameter of the reinforcing body 22 (2 to 4 times the outer diameter of the foundation pile A) or slightly larger than that. Further, the axial length of the cylindrical body 11 is such that the cylindrical body 11 is rotated and penetrated into the construction ground, and the bottom cover 13 portion is partitioned by the reinforcing body 22 into the construction ground (FIG. 1, FIG. 2), when the position reaches the vicinity of the lower end (when the rotation penetration is completed), the upper end portion of the cylindrical body 11 is set to a dimension protruding from the construction ground surface. This is because the reinforcing section H is formed at a predetermined depth, and the cylindrical body 11 can be easily removed from the construction ground by the pile driving machine after the curable fluid 20 is placed. In addition, the foundation pile A is a prefabricated pile with a cylindrical cross-section in which a tip is embedded in advance to a support layer by a pile driver. The reinforcing bar 21 is formed by combining a number of straight reinforcing bars and annular reinforcing bars in a hook shape. The curable fluid 20 is a civil engineering / building material such as concrete or cement mortar that has fluidity during construction and hardens over time after construction.

  The blade 12 is formed from a screw having a screwing action such as a spiral wing. However, as long as it has a screwing action, the shape of the blade 12 is not limited, and a rectangular strip is slightly inclined with respect to the horizontal. The arranged shape may be used. Although the dimension of the blade | wing 12 is set according to the hardness of a construction ground, 1.5 times or less of the outer diameter of the said cylindrical body 11 is desirable. The blades 12 are attached to the outer peripheral surface near the bottom of the cylindrical body 11.

  The bottom lid 13 is made of, for example, a steel plate, and a through hole 15 through which the pile head B of the foundation pile A passes is formed at the center thereof. The inner diameter of the through hole 15 is set slightly larger than the outer diameter of the pile head B. The outer diameter of the bottom lid 13 varies depending on the method of attaching to the cylindrical body 11, but is set slightly smaller than the inner diameter of the cylindrical body 11 when fitted into the bottom of the cylindrical body 11. In addition, when the foundation pile A is a thin-diameter rotating penetration steel pipe, the rotational force of the pile driver is applied to the foundation pile A on the peripheral surface (side surface) near the upper end of the pile head B as shown in FIG. Since the rotating metal fitting C for transmission is often provided, a recess 15a for passing the rotating metal fitting C through the through hole 15 may be provided in accordance with this as shown in FIG. Although there is no restriction | limiting in particular about the shape of the bottom cover 13, For example, the donut plate shape with low manufacturing cost may be sufficient.

  FIGS. 5A to 5D show an example in which the bottom lid 13 is detachably fitted to the bottom of the cylindrical body 11. As shown in FIG. 5A, the cylindrical body 11 is provided with a plurality of (for example, four) cut portions 11 a having a predetermined depth with a lower end opened at the bottom thereof with an appropriate interval in the circumferential direction. As shown in FIGS. 5B and 5C, the bottom lid 13 has a plurality of protrusions 13a (for example, four pieces) that are removably fitted into the notches 11a around the periphery of the bottom lid 13 at appropriate intervals in the circumferential direction. Provided. As shown in FIG. 5 (d), the bottom lid 13 is detachably attached to the bottom of the cylindrical body 11 by fitting these protrusions 13 a into the notch 11 a. In this case, the outer diameter of the bottom cover 13 is set slightly smaller than the inner diameter of the cylindrical body 11 as described above. When the cylindrical body 11 is rotated and penetrated into the construction ground, the bottom lid 13 is pressed against the bottom side of the cylindrical body 11 by earth and sand, so that it does not come off.

  In order to remove the bottom lid 13 attached by the method shown in FIGS. 5A to 5D from the bottom of the cylindrical body 11, for example, a pushing jig 30 is used as shown in FIG. Specifically, when the pushing jig 30 is applied to the upper end portion of the reinforcing bar 21 (see FIGS. 1 and 2) and the pushing jig 30 is pushed down by the pile driving machine, the lower end portion of the reinforcing bar 21 causes the bottom lid 13 to be moved. Push downward to remove the protrusion 13a from the notch 11a. As a result, the bottom cover 13 comes out of the cylindrical body 11 and comes off. By providing the claw portion 13b on the bottom surface (back surface) of the bottom lid 13, the ground is excavated and agitated and softened by the claw portion 13b when the excavation pipe 10 is rotated and penetrated. Pushing becomes easy.

  An embodiment of a pile head reinforcement method for a foundation pile according to the present invention will be described with reference to FIGS.

  FIG. 1A shows a construction process of the foundation pile A. In this construction process, the foundation pile A is rotated and penetrated to the final depth of the construction ground by a pile driver. The foundation pile A is a pile having a cylindrical cross section, and a concrete pile such as a PHC pile or a steel pipe pile is used. As a construction method of the foundation pile A, it is a general construction method adopted for the existing piles such as the rotating intrusion pile, the Nakabori pile, and the pre-boring pile. The tip (lower end) of the foundation pile A is supported by a solid support layer in the construction ground. The top of the pile head B at the upper end of the foundation pile A is generally lower than the construction ground surface.

  FIG. 1 (b) shows the construction process of the excavation pipe 10. In this step, first, the bottom cover 13 is detachably attached to the bottom of the cylindrical body 11. This attachment is performed, for example, by the method shown in FIGS. Next, the excavation pipe 10 to which the bottom cover 13 is attached is suspended from a pile driving machine (not shown), and alignment is performed so that the axis of the excavation pipe 10 matches the axis of the foundation pile A in the construction ground. . After this, the excavation pipe 10 is rotated and penetrated into the construction ground by a pile driver. At this time, the excavation pipe 10 enters the construction ground while receiving the screwing action of the blades 12.

  FIG. 1 (c) shows the rotational penetration process of the excavation pipe 10. In this process, the pile head B of the foundation pile A penetrates the through hole 15 of the bottom lid 13 and penetrates into the excavation pipe 10 while the excavation pipe 10 enters the construction ground while rotating. And if the bottom cover 13 continues rotation penetration of the excavation pipe 10 with a pile driving machine until it reaches the desired depth (the lower end of the reinforcement section H defined by the reinforcing body 22), the pile head in the excavation pipe 10 A space 14 for constructing the reinforcing body 22 is formed around the portion B, and the rotary penetration of the excavation pipe 10 is completed. The upper end portion of the excavation pipe 10 protrudes from the construction ground surface.

  FIG. 1 (d) shows an installation process of the reinforcing bar 21. In this process, the reinforcing bar 21 is suspended from the pile driving machine, and the reinforcing bar 21 is installed in the space 14 around the pile head B. Then, a necessary position holding measure is taken with respect to the reinforcing bar 21 so that the reinforcing bar 21 does not move when the curable fluid 20 is placed in the space 14. The outer diameter of the reinforcing bar 21 is set so that the cover thickness of the curable fluid 20 is about 6 cm to 10 cm when the curable fluid 20 shown in FIG. In addition, the earth and sand around the excavation pipe 10 are not pressed by the blades 12 and discharged (soiled) onto the construction ground.

  FIG. 1 (e) shows a process for placing the curable fluid 20. In this process, a curable fluid 20 is driven into the space 14 from the head of the excavating pipe 10 using a chute or a tremy pipe (not shown). At the time of this placement, the upper surface of the curable fluid 20 is set to be higher than the expected height of the reinforcing body 22.

  FIG. 1 (f) shows the removal process of the excavation pipe 10. In this step, before the excavation pipe 10 is removed from the construction ground, the bottom lid 13 is removed from the bottom of the excavation pipe 10 by a pushing jig 30, for example, as shown in FIG. Then, the excavation pipe 10 is removed from the construction ground by rotating the excavation pipe 10 in the direction opposite to that during the rotation penetration by the pile driving machine. When it does so, the upper surface height of the curable fluid 20 will fall by the volume corresponding to the thickness of the excavation pipe 10. That is, the curable fluid 20 spreads in the gap generated by removing the excavating pipe 10, and the height of the curable fluid 20 is lowered by this spread. The reason why the upper surface of the curable fluid 20 becomes higher than the expected height of the reinforcing body 22 during the placing process shown in FIG. 1 (e) is that the curable fluid 20 spreads and becomes lower in height. Is to expect. With the passage of time, the curable fluid 20 is cured, and a strong reinforcing body 22 is constructed around the pile head B.

  Another embodiment of the pile head reinforcement method for a foundation pile according to the present invention will be described with reference to FIGS. In addition, in the figure, the same code | symbol is attached | subjected to the part same as the part shown to Fig.1 (a) thru | or (f), and the detailed description is abbreviate | omitted.

  In the present embodiment, in the rotary penetration process of the excavation pipe 10, the reinforcing bar 21 is previously installed in the excavation pipe 10 and then the rotary penetration of the excavation pipe 10 is started. It is the same as the Example of the pile head reinforcement construction method of a foundation pile shown in. Specifically, the construction process of the foundation pile A shown in FIG. 2 (a) is the same as that shown in FIG. 1 (a), and the rotary penetration process of the excavated pipe 10 shown in FIG. The content of the curable fluid 20 shown in FIG. 2 (d) is the same as that shown in FIG. 2 (d), and the excavation shown in FIG. Since the removal process of the pipe 10 is the same as that shown in FIG. 1 (f), description thereof will be omitted, and only the construction process of the excavation pipe 10 shown in FIG. 2 (b) will be described.

  In the erection process of the excavation pipe 10 shown in FIG. 2 (b), the reinforcing bar 21 is installed in the tubular body 11 in advance, and the bottom cover 13 is attached to the bottom of the tubular body 11. The attachment method is performed, for example, by the method shown in FIGS. 5A to 5D, similarly to the case described in the erection process shown in FIG. The reinforcing bar 21 may be fixed to the bottom lid 13 and integrated in advance. Thereafter, similarly to the case described with reference to FIG. 1B, the excavation pipe 10 is suspended from a pile driving machine (not shown), and the axis of the excavation pipe 10 is the axis of the foundation pile A in the construction ground. Align so that it matches. And the excavation pipe 10 is made to rotate and penetrate into the construction ground by a pile driver. In this embodiment, it is possible to omit the step of installing the reinforcing bar 21 in the tubular body 11 during the construction as compared with the embodiment shown in FIG.

  7 (a) and 7 (b) show the pile head reinforcement method for the foundation pile shown in FIGS. 1 (a) to (f), or the pile head reinforcement for the foundation pile shown in FIGS. 2 (a) to (e). The reinforcement body 22 constructed | assembled by the construction method is shown. As described above, the reinforcing body 22 includes the reinforcing bar 21 and is composed of the curable fluid 20. The outer diameter is two to four times the outer diameter of the foundation pile A, and the axial length is The outer diameter of the reinforcing body 22 is 3 to 6 times. By constructing and reinforcing the reinforcing body 22 around the pile head B of the foundation pile A, the foundation pile A exhibits several times to ten times the rigidity and bending / shear strength of the pile alone, The horizontal displacement and bending moment of the foundation pile A are greatly reduced (to a fraction). Moreover, since the pile head B of the foundation pile A increases the part which touches the ground by the reinforcing body 22, it becomes possible to receive a big horizontal ground reaction force. The remaining bottom lid 13 is a construction member, and has no role after the reinforcement body 22 is constructed.

  FIGS. 8A and 8B show a modification of the reinforcing body 22 shown in FIGS. 7A and 7B described above. In the figure, the same parts as those shown in FIGS. 7A and 7B are denoted by the same reference numerals, and the description thereof is omitted.

  In the reinforcing body 22 of the present modification, a reinforcing bar 21 having a length longer than the axial length of the reinforcing body 22 and protruding upward from the pile head B is used. Thereby, as shown to Fig.8 (a), the upper end part 21a of the reinforcing bar 21 protrudes higher than the pile head B from the upper surface of the reinforcement body 22. As shown in FIG. When the footing 23 is constructed on the upper surface of the reinforcing body 22, after the reinforcing body 22 is constructed, the root is cut and the upper end portion 21 a of the reinforcing bar 21 projecting on the upper surface of the reinforcing body 22 is rolled up to place concrete. As a result, as shown in FIG. 8B, the footing 23 is constructed on the upper surface of the reinforcing body 22, the reinforcing body 22 and the footing 23 are reliably integrated by the reinforcing bar 21, and the strength of the pile head joint portion is greatly improved. And the load transmission is ensured. In addition, in FIG.8 (b), the reinforcing bar for coupling | bonding the foundation pile A and the footing 23 is abbreviate | omitted and shown in figure. The foundation pile A and the footing 23 are joined by installing a reinforcing bar rod or welding a reinforcing bar to the side face of the pile head in the same manner as a normal foundation pile.

  As described above, according to the pile head reinforcement method for foundation piles shown in FIGS. 1 (a) to (f) and the pile head reinforcement method for foundation piles shown in FIGS. 2 (a) to (e), This excavation pipe 10 is provided by providing a blade 12 having a screwing action on the outer peripheral surface of the cylindrical body 11, and attaching a bottom lid 13 having a through hole 15 to the bottom of the cylindrical body 11 so as to be detachable and closed. While the pipe 10 is rotated through the construction ground where the foundation pile A has already been installed, the pile head B of the foundation pile A is penetrated into the excavation pipe 10 through the through hole 15, Since the space 14 for constructing the reinforcing body 22 is formed, a heavy machine different from the pile driving machine is not required, and no excavation residual soil is generated, and the excavation pipe 10 is rotated and penetrated. For this reason, the torque required to exceed the allowable torsional torque of foundation pile A could not be constructed. Nor does it. In addition, a curable fluid 20 is placed in the space 14 in which the reinforcing bar 21 is installed, and a reinforcing body 22 including the reinforcing bar 21 made of the curable fluid 20 is constructed around the pile head B. Therefore, the combined effect of the foundation pile A and the reinforcing body 22 can exhibit several times or more than ten times the rigidity and bending / shear strength of the foundation pile A alone. The bending moment and horizontal displacement generated in the can be significantly reduced. Furthermore, by extending the reinforcing bar 21 to the footing 23, the reinforcing body 22 and the footing 23 are integrated, the transmission of force between them becomes smooth, and the reliability of the pile head coupling portion is increased. Furthermore, a heavy machine to be used can construct a reinforcing body only by a pile driving machine, and construction can be performed at low cost.

  FIG. 9 is a partially cutaway side view showing a first modification of the excavation pipe 10 of FIG. 3, and the same components as those shown in FIG.

  In order to transmit the rotational force directly from the pile driver to the excavation pipe 10, it is necessary to replace a member (commonly called cap) that connects the motor of the pile driver and the excavation pipe 10 with one that matches the outer diameter of the excavation pipe 10. That is, it is necessary to replace the cap with a larger diameter than the cap used for the construction of the foundation pile A. Therefore, in the present modification, a transmission pipe 16 having the same diameter as the foundation pile A is disposed at the upper end of the excavation pipe 10, and the rotational force to rotate and penetrate the excavation pipe 10 is transmitted via the transmission pipe 16. , Omitting cap replacement. Specifically, a disc-shaped connection fitting 17 is attached to the upper end of the excavation pipe 10, and a transmission pipe 16 is attached to the center of the connection fitting 17 so as to coincide with the axis L of the excavation pipe 10. The excavation pipe 10 can be rotated and inserted without exchanging the cap after the construction of the pile A, thereby improving the construction efficiency. Since the upper end of the excavation pipe 10 is closed by the connection fitting 17, the connection fitting 17 is provided with an input port 17 a for driving the curable fluid 20 into the excavation pipe 10. In the case where the reinforcing bar 21 is installed after the excavation pipe 10 is rotated and penetrated into the construction ground (see FIG. 1D), a connection structure in which the connection fitting 17 can be attached to and detached from the excavation pipe 10 is adopted. To do. After the rotation penetration, the connection fitting 17 is once removed from the excavation pipe 10 and the reinforcing bar 21 is installed, and then the connection fitting 17 is connected to the excavation pipe 10 again. A taper tube may be used as the connection fitting 17.

  FIG. 10 shows a second modification of the excavation pipe 10 of FIG. 3, and the same components as those shown in FIG.

  When the bottom surface of the bottom cover 13 is horizontal as shown in FIG. 3 (b), there is a risk of receiving a large resistance from the earth and sand when the excavation pipe 10 is rotated into the construction ground. Therefore, in this modification, a plurality (four) of triangular excavation plates 18 are arranged radially (in a cross shape) on the lower surface (back surface) of the bottom lid 13. Thus, when the excavation pipe 10 rotates and penetrates into the construction ground, the excavation plate 18 first softens the excavation of the soil below the bottom lid 13 and guides the earth to the outside, and the penetration resistance of the excavation pipe 10 to the construction ground. Can be relaxed.

  FIG. 11 is a first modification of the pile head reinforcement method for the foundation pile shown in FIG. 1 or 2. In the figure, the same parts as those shown in FIG. 1, FIG. 2, and FIG.

  At the time of construction of foundation pile A, pile head B is buried in the ground using Yatco, then when Yatco is pulled out, the ground around the hole formed with Yatco collapses and the hole is buried with earth and sand There is a risk that. If it does so, it will be necessary to remove the earth and sand which collapsed before the excavation pipe | tube 10 penetrates into the construction ground from a hole, and the operation | work which penetrates the pile head B to the through-hole 15 of the bottom cover 13 will become troublesome. Therefore, in the present modification, the yatco used in the construction process of the foundation pile A can be used to guide the drilling pipe 10 to the construction ground when the drilling pipe 10 continues to rotate. The guide-use YATCO 40 used in this modification is set so that the outer diameter of the upper portion 40a is substantially the same as the outer diameter of the foundation pile A (pile head B) (the dimension that penetrates the through hole 15 of the bottom lid 13). The outer diameter of the lower portion 40b is set slightly smaller than the inner diameter of the foundation pile A (pile head B) (so that it can be fitted into the pile head B). The length of the guide / yat 40 is set such that when the lower portion 40b is fitted into the pile head B, the upper end portion of the upper portion 40a protrudes from the construction ground. As shown in FIG. 11 (a), the guide-combined Yatco 40 is self-supporting while maintaining the vertical when the lower portion 40b is fitted into the pile head B. When the excavation pipe 10 is rotated and penetrated, as shown in FIG. 11 (b), the guide / yat 40 (the upper end portion of the upper portion 40 a) protruding from the surface of the construction ground penetrates the through hole 15 of the bottom lid 13 and excavates. The pipe 10 is guided so that the rotation penetration into the construction ground and the penetration into the through hole 15 of the pile head B can be smoothly performed. Since the guide combined use YATKO 40 of this modification can also be used to guide the excavation pipe 10 to the construction ground after the pile head B is buried in the ground, it is necessary to prepare a YATCO and a guide member, respectively. There is no. Moreover, since it does not pull out immediately after embedding the pile head B, the ground around the hole formed with the yatco does not collapse.

  FIG. 12 is a second modification of the pile head reinforcement method for the foundation pile shown in FIG. 1 or 2. In the figure, the same parts as those shown in FIG. 1, FIG. 2, and FIG.

  The inner diameter of the through hole 15 in the bottom lid 13 is set slightly larger than the outer diameter of the pile head B so that the pile head B can be smoothly penetrated into the through hole 15. In the case of clayey ground, mud soil may adhere to the peripheral surface of the pile head B. Depending on the degree of adhesion, if the mud adheres, the combined effect of the pile head B and the reinforcing body 22 may be reduced. Therefore, in this modification, the adhering mud is removed before placing the curable fluid 20 in the space 14 around the pile head B of the excavating pipe 10. In the case shown in FIG. 12 (a), the brush 50 is mounted in the excavation pipe 10 while the excavation pipe 10 penetrates the construction ground, and the vertical movement of the pile head B is repeated while rotating the cylindrical body 11. The mud adhered to the peripheral surface is removed with the brush 50. In the case shown in FIG. 12B, the nozzle 51 is mounted in the excavation pipe 10 while the excavation pipe 10 penetrates into the construction ground, and the nozzle 51 is moved up and down while rotating around the pile head B. The washing liquid is sprayed repeatedly, and the mud adhering to the peripheral surface of the pile head B is washed away and removed.

  The pile head reinforcement method of the foundation pile of the present invention can be applied to the case where the strength of the pile head is greatly increased and the vertical supporting force of the foundation pile is effectively utilized. It can also be applied to increase the strength of the pile head when the ground near the pile head of the foundation pile is soft.

DESCRIPTION OF SYMBOLS 10 Excavation pipe 11 Cylindrical body 12 Blade 13 Bottom cover 14 Space 15 Through hole 20 Hardening fluid (concrete)
21 Reinforcing bar 22 Reinforcing body 30 Pushing jig 40 Guide Yatco A A foundation pile B pile head

Claims (4)

A pile head reinforcement method for foundation piles embedded in the ground,
A cylindrical body that forms a space for constructing a reinforcing body containing reinforcing bars by placing a curable fluid around the pile head of the foundation pile, and provided on the outer peripheral surface of the cylindrical body Using a drilling pipe comprising a blade having a screwing action, and a bottom lid that has a through hole through which the pile head penetrates and is detachably attached to the bottom of the cylindrical body and closes the bottom,
The foundation pile is embedded in the excavation pipe until the pile head penetrates into the space through the through-hole and the bottom lid is positioned at the lower end of the reinforcement section partitioned by the reinforcing body into the construction ground. Rotating and penetrating process to rotate and penetrate the construction ground
An installation step of installing the reinforcing bar in the space around the pile head before the rotation penetration step or after the rotation penetration step;
A placing step of placing the curable fluid in the space around the pile head;
Leaving the bottom cover, removing the excavation pipe from the construction ground; and
A pile head reinforcement method for foundation piles, comprising: In the pile head reinforcement construction method of the foundation pile according to claim 1,
The method for reinforcing a pile head of a foundation pile, wherein the reinforcing bar is longer than an axial length of the reinforcing body, and an upper end portion is set to a height protruding from the pile head. In the pile head reinforcement method of the foundation pile according to claim 1 or 2,
A transmission force having the same diameter as that of the foundation pile is arranged at the upper end of the excavation pipe so as to coincide with the axis of the excavation pipe, and the rotational force causes the excavation pipe to rotate into the ground via the transmission pipe. The pile head reinforcement method of the foundation pile characterized by transmitting. In the pile head reinforcement construction method of the foundation pile according to claim 1,
The Yatco used to embed the pile head below the construction ground surface during construction of the foundation pile, the upper part of which is set to an outer diameter that penetrates the through hole, and the lower part is the pile head It is set to an outer diameter that can be fitted in, and its axial length is set so that a part of its upper part protrudes from the construction ground surface, and guides the rotation penetration of the excavation pipe during the rotation penetration step A pile head reinforcement method for foundation piles, characterized in that it is a guide-and-use Yatco.