JP2007162416A - Concrete pile joining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a concrete pile joining method belonging to a technical field of a method for joining a pile head of a concrete pile to a lower part of a structure, more specifically a method for positively reducing bending moment in case of a big earthquake. <P>SOLUTION: Pile main reinforcements 3 are arranged lowered to a fixed depth from a pile head level, and concrete 4 is placed to construct a foundation pile 1. An extra fill on the pile head 2 of the foundation pile 1 is removed to the pile head level to leave a center core at the pile head and to form an annular stepped part at the outer periphery. Concrete with low rigidity and a high deforming property is placed at the stepped part of the pile head, and a foundation such as a foundation beam, a foundation slab, footing and a column is constructed in an axial force supportable manner on the upper face of the pile head. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to the technical field of a method for joining a pile head of a concrete pile to a lower part of a structure, and more specifically, relates to a method for joining a concrete pile that reliably reduces a bending moment during a large earthquake.

  Various methods for preventing shear failure of a pile during an earthquake are implemented for joining a pile head of a concrete pile and a lower portion of a structure such as a foundation beam, a foundation slab, or a footing. For example, as shown in FIG. 5, there is a method of preventing damage to the pile by fixing the main reinforcement of the pile head to the foundation slab or foundation beam and increasing the bending rigidity to be higher than the bending stress of the pile head generated during an earthquake. . Moreover, as shown in FIG. 6, there is a method of preventing damage to the pile by reducing the diameter of the pile head and reducing the bending rigidity to suppress the generation of bending stress during an earthquake.

By the way, the following patent document discloses a joining method in which a shearing force during an earthquake is transmitted by a frictional force to prevent pile damage.
In Patent Document 1, the pile head and the lower part of the structure are cut off, and the main axial reinforcement does not protrude from the pile head or the axial main reinforcement protrudes so as not to transmit bending stress to the foundation beam or the like. Thus, a method of joining in a contact state in which a shearing force is transmitted via a frictional force is disclosed.

  Patent Documents 2 to 4 disclose an elastic body made of a rubber cap between a pile head and a lower part of the structure as a method for preventing bending damage by reducing a bending moment generated in the structure during an earthquake. Alternatively, a method of interposing an impact absorbing material and an up-down restoring member, and a method of constructing a pile head with a concrete column containing a rubber chip are disclosed.

Japanese Patent No. 366314 Japanese Patent Laid-Open No. 62-156429 Japanese Patent No. 3677702 JP-A-10-183612

  In the method shown in FIG. 5, since the bending moment generated at the head of the pile increases proportionally when large vibrations occur, it is necessary to increase the yield strength of the pile in order to prevent damage to the pile. As the method, the pile diameter is increased, the main reinforcement is increased, and the steel pipe is reinforced. Moreover, in order to increase the yield strength of the lower part of structures such as foundation beams and foundation slabs, it is also necessary to increase the amount of warp and main reinforcement. Therefore, main bars such as slab bars, column bars, and foundation beam bars are congested on the pile head, which makes the bar arrangement work very troublesome and increases the cost. Furthermore, there is a problem in that the outer periphery of the pile head is damaged during a large earthquake, causing cracks in the pile body and impairing the proof strength of the entire pile.

  It is recognized that the method shown in FIG. 6 prevents damage to the pile by reducing the horizontal stiffness of the pile head by increasing the diameter of the pile head and increasing horizontal deformation. However, since the diameter of the pile head is reduced, the usual stress increases, and it is necessary to increase the yield strength of the troublesome pile described above.

  The technique described in the above-mentioned Patent Document 1 is configured to cut a lower part of a structure and a pile head, and to transmit a shearing force via a frictional force as a configuration in which bending stress is not transmitted from the pile head to a foundation beam or the like. The point is recognized. However, the large bending moment concentrated on the outer periphery of the pile head during a large earthquake cannot be reduced, and the vicinity of the outer periphery of the head is crushed and the soundness of the foundation pile cannot be ensured. Moreover, since it is set as the structure which does not project the main reinforcing bar of an axial direction from the upper surface of a pile head, or the construction of piled-up concrete performed at the time of pile construction is difficult, workability is bad.

  In Patent Document 2 and Patent Document 3, an elastic body or a shock absorbing material is provided on the upper surface of the pile head to reduce the bending moment. However, these always undergo compressive deformation due to the axial force of the superstructure. In addition, many foundation piles of the structure are arranged, and the axial force applied to each foundation pile is also different. Therefore, a subsidence difference is generated in the compression deformation of the elastic body or the shock absorbing material installed on the pile head of each foundation pile and affects the entire structure. In addition, these technologies do not take into account the shear strength of elastic bodies due to horizontal forces during a large earthquake.

  Moreover, in patent document 4, stress concentrates on the outer periphery vicinity of the concrete pillar containing a rubber chip by the axial force of a structure, and the distortion is large. For this reason, in the event of a large earthquake, the vicinity of the outer periphery is damaged, causing a great adverse effect on the entire structure.

  In short, none of the above-described conventional techniques has yet been able to secure a sufficient pile soundness while reducing a large bending moment generated in the event of a large earthquake and join a pile with good workability.

  The object of the present invention is to construct a pile head from a central core portion and a low-rigidity / high-deformability concrete portion placed in a stepped portion, to reliably reduce the bending moment during a large earthquake, and The object is to provide a method for joining concrete piles that can ensure soundness and has excellent workability.

As means for solving the above-described problems of the prior art, the method for joining concrete piles according to the invention described in claim 1 is:
A method of joining a pile head of a concrete foundation pile supporting a structure and a lower part of the structure,
Lowering the pile main bar from the pile head level to a certain depth, placing the concrete, constructing the foundation pile by placing concrete,
Removing the excess pile above the pile head of the foundation pile to the pile head level, leaving a central core portion on the pile head, and forming an annular stepped portion on the outer periphery thereof;
Placing a low-rigidity, highly deformable concrete on the stepped portion of the pile head;
Constructing a foundation such as a foundation beam of a structure, a foundation slab, a footing, or a column on the upper surface of the pile head so as to support axial force;
It is characterized by comprising.

The invention according to claim 2 is the method for joining concrete piles according to claim 1,
The outer diameter of the central core portion is characterized by a size that can support the overload.

The invention according to claim 3 is the method for joining concrete piles according to claim 1,
The low-rigidity concrete is a lightweight aggregate, rubber chip, mortar that does not contain voids and aggregates, and the highly deformable concrete is fiber-reinforced concrete.

The method for joining concrete piles according to the present invention has the following effects.
1) Since the pile head is composed of a central core made of high-strength concrete and low-rigidity / high-deformability concrete cast in the stepped portion, the central core supports the load on the structure, Bending moment that high deformable concrete concentrates especially on the outer periphery of piles is greatly reduced in the event of a large earthquake. It can prevent damage to the central core part made of concrete, maintain the soundness of the entire concrete foundation pile, and prevent collapse of the structure.
2) Since the pile main reinforcement is lowered from the pile head to a certain depth and the reinforcement is arranged, the lifting work when constructing the concrete pile can be simplified and the workability can be improved.

The present invention is a method for joining a pile head 2 of a foundation pile 1 that supports a structure and a lower part of the structure.
The pile main reinforcement 3 is lowered from the pile head level H1 to a certain depth H2, and then the concrete 4 is placed.
The excess pile above the pile head 2 of the foundation pile 1 is removed to the pile head level H1, the central core portion 20 is left on the pile head 2, and an annular step portion 21 is formed on the outer periphery thereof.
Low rigidity / highly deformable concrete 5 is placed on the stepped portion 21 of the pile head 2 so that the upper surface of the pile head 2 is horizontal.
On the upper surface of the pile head 2, a foundation 6 such as a foundation beam, foundation slab, column, underground wall or the like of the structure is constructed so as to be able to support the axial force.

Hereinafter, a concrete pile joining method according to the present invention will be described with reference to the drawings.
First, as shown in FIG. 1, the foundation ground G is excavated to a predetermined depth with an excavator or the like to provide a pile hole (not shown). And the pile main reinforcement 3 is lowered | hung and arranged to the fixed depth H2 below the pile head level H1 to the said pile hole. After arranging the pile main reinforcing bars 3 as described above, the foundation pile 1 is constructed by placing concrete 4 in the pile holes. Concrete placement will be done by surfacing (single-dot diagonal line) to impure impure concrete that floats in the upper layer.

  Next, as shown in FIG. 2, after excavating to the depth ground (H1 in the figure) to construct the foundation 6 of the structure such as the foundation beam, foundation slab, footing, column, underground wall, etc. Hang the extra-concrete concrete (dotted line part). When removing the surplus concrete to the pile head level H1 by this lifting work, the central core portion 20 is left in the pile head 2 and the stepped portion 21 is formed by ringing the outer periphery to a certain depth H3. Form. This depth H3 is designed to a depth that can sufficiently reduce the bending moment generated in the event of a large earthquake by the low rigidity / highly deformable concrete 5 described later. Naturally, it is comprised so that it may become above the pile main reinforcement 3 (H2) mentioned above. Moreover, the outer diameter of the central core part 20 is made into the magnitude | size which can support an upper load (invention of Claim 2).

  Then, as shown in FIGS. 3A and 3B, the low-rigidity / high-deformability concrete 5 is placed on the step portion 21 provided by the above method. The low-rigidity / high-deformability concrete 5 is, for example, lightweight aggregate and rubber chips as low-rigidity concrete, and mortar without voids and aggregates, and fiber-reinforced concrete as high-deformation concrete. Described invention). These are appropriately selected depending on the size of the structure and the ground conditions.

  Thereafter, the top surface of the pile head 2 is flattened by treating the top surface of the low-rigidity / highly deformable concrete 5 placed on the stepped portion 21 so as to be horizontal with the central core portion 20. As a result, a sufficient area to be in contact with the foundation 6 of the structure to be constructed later can be secured, so that it is possible to expect a shear force transmission by a frictional force in addition to firmly supporting the axial force. Of course, in the case of the rubber-based low-rigidity concrete 5, it is also preferably implemented to be slightly above the pile head level H1.

  Semi-rigid that can support the axial force of the foundation 6 of the structure such as footing, foundation slab, foundation beam, column, underground wall, etc. as shown in FIG. Build sequentially as a junction. Therefore, since the lower part 6 and the foundation pile 1 of the said structure can suppress a reinforcing bar to the minimum, cost can be reduced and work efficiency can also be improved.

  Since the present invention constructs the foundation pile 1 by the method as described above, the pile load (long-term vertical force) is firmly supported by the central core portion 20 and the stress is concentrated at the time of a huge earthquake due to a large earthquake. The low-rigidity and high-deformability concrete 5 placed at the outer peripheral position 2 reliably reduces the bending moment. Even if a bending moment that causes collapse is applied, the low rigidity / highly deformable concrete 5 of the stepped portion 21 is destroyed first, so that the foundation pile 1 composed of the central core portion 20 and the strong concrete 4 is damaged such as cracks. It is possible to prevent the occurrence of cracks and ensure the soundness of the piles, thereby preventing the collapse of the structure.

  The embodiments have been described with reference to the drawings. However, the present invention is not limited to the illustrated embodiments, and design modifications and application variations that are usually made by those skilled in the art are within the scope of the technical idea of the invention. I will add a note to include the range. For example, it is conceivable to reduce the bending moment by joining the central core portion 20 and the lower portion 6 of the structure with a reinforcing bar having a predetermined length.

In the joining method of the concrete pile which concerns on this invention, it is an elevation view which shows the step which builds a foundation pile. It is the elevation which showed the stage which formed the central core part and the level | step-difference part in the joining method of the concrete pile which concerns on this invention. A and B are the figures which showed the step which laid the low rigidity and highly deformable concrete to the level | step-difference part in the joining method of the concrete pile concerning this invention. In the joining method of the concrete pile which concerns on this invention, it is the elevation which showed the step which constructed | assembled the lower part of the structure to the upper surface of the pile foundation. It is a reference figure which shows a prior art example. It is a reference figure which shows another prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Foundation pile 2 Pile head 20 Central core part 21 Step part 3 Pile main reinforcement 4 Concrete
5 Low rigidity and high deformation concrete

Claims (3)

A method of joining a pile head of a concrete foundation pile supporting a structure and a lower part of the structure,
Lowering the pile main bar from the pile head level to a certain depth, placing the concrete, constructing the foundation pile by placing concrete,
Removing the excess pile above the pile head of the foundation pile to the pile head level, leaving a central core portion on the pile head, and forming an annular stepped portion on the outer periphery thereof;
Placing a low-rigidity, highly deformable concrete on the stepped portion of the pile head;
Constructing a foundation such as a foundation beam of a structure, a foundation slab, a footing, or a column on the upper surface of the pile head so as to support axial force;
A method for joining concrete piles, comprising:   The method for joining concrete piles according to claim 1, wherein the outer diameter of the central core portion is set to a size capable of supporting an overload.   2. The method for joining concrete piles according to claim 1, wherein the low-rigidity concrete is a mortar that does not contain lightweight aggregates, rubber chips, and aggregates, and the highly deformable concrete is fiber-reinforced concrete.

Images