JP2005320692A - Pile foundation and its construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pile foundation and its construction method capable of inexpensively reduce the burden of a pile imposed on horizontal force in the case of earthquake in a short construction period of time. <P>SOLUTION: The pile foundation comprises a footing 4 of a reinforced concrete construction constructed on the ground 1 consisting of a soft layer 2 and a supporting layer 3 under the soft layer 2, a bearing pile 5 consisting of a pre-cast concrete reaching a pile front end section 5a to the supporting layer 3 and connecting a pile head section 5b to the footing 4 or a higher strength pile such as a steel pipe pile or the like and a ground improvement body 6 locally formed on the circumference section of the bearing pile 5 so that the footing 4 is wrapped from the ground surface G to a depth not shallower than 10m in plan view. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pile foundation and a construction method thereof.

In recent years, the development of high bearing capacity piles in ready-made concrete piles and steel pipe piles has progressed, but for horizontal forces during earthquakes, methods such as increasing the material strength and the thickness of the steel pipe have been adopted. Currently there is no effective policy. On the other hand, the method of reducing the burden of the pile with respect to the horizontal force at the time of an earthquake by ground improvement is proposed (for example, refer patent document 1).
JP 2001-342637 A (page 2-3, FIG. 1)

However, it can be said that the conventional pile foundation ground improvement method is not practical in terms of construction cost and construction period, such as a method of performing ground improvement for the majority of the pile length and an improvement of the entire site.
The present invention has been made in view of the above-described problems, and an object thereof is to provide a pile foundation capable of reducing the burden of a pile against a horizontal force during an earthquake at a low cost and in a short construction period, and a construction method thereof. To do.

In order to achieve the above object, in the pile foundation according to the present invention, a footing constructed on the ground having a soft layer on the ground surface side and a support layer under the soft layer, and the tip of the pile is the support layer. The pile head includes a support pile joined to the footing and a ground improvement body formed on the outer periphery of the support pile from the ground surface to a depth of 10 m or less.
Here, the soft layer is a ground layer that may be consolidated, and the support layer is a high-quality ground that does not settle. Further, the soft layer may include a liquefied layer in the layer.
It is the portion from the ground surface to a depth of 10 m or less that is most related to the horizontal resistance of the support pile during earthquake. Therefore, in the present invention, by forming a ground improvement body locally on the outer periphery of the support pile from the ground surface to a depth of 10 m or less, the ground reaction force coefficient is increased and the horizontal deformation and bending moment of the support pile during an earthquake. Is to make it smaller. Particularly when the liquefied layer is shallower than 10 m, it is very effective.
In order to form the ground improvement body, inexpensive ground improvement methods for shallow and middle layers such as the power blender method and the Elmud method are adopted. The power blender method is a ground improvement method in which an improved material such as cement or cement-based solidifying material is kneaded into a slurry and then injected into the ground, and the in-situ soil and the improved material are forcibly stirred and mixed to solidify. On the other hand, the Elmud method uses stable treated soil that is made by adding muddy water (or water) and solidification material such as cement to the soil generated by construction, and mixing the foundation, structure backfilling, backfilling and filling narrow spaces. This is a ground improvement method that does not require compaction, and can set the strength after placement curing by adjusting the amount of solidification material added.

  Further, the pile foundation construction method according to the present invention is a pile foundation construction method constructed on the ground having a soft layer on the ground surface side and a support layer under the soft layer. After forming a ground improvement body in the soft layer to a depth of 10 m or less, a support pile is placed in the ground improvement body so that the tip of the pile reaches the support layer, and on the pile head of the support pile A footing is formed.

  According to the present invention, by forming a ground improvement body locally on the outer periphery of the support pile from the ground surface to a depth of 10 m or less, the burden on the pile against the horizontal force during earthquake can be reduced at a low cost and in a short construction period. Can be realized.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a pile foundation and its construction method according to the present invention will be described with reference to the drawings.
Drawing 1 is an outline elevation sectional view showing an example of an embodiment of a pile foundation concerning the present invention.
As shown in FIG. 1, the pile foundation according to the present embodiment has a reinforced concrete footing 4 constructed on a ground 1 composed of a soft layer 2 and a support layer 3 below the soft layer 2, and a pile tip 5 a is a support layer. 3 and the pile head 5b is joined to the footing 4 with a support pile 5 made of a high strength pile such as a ready-made concrete pile or a steel pipe pile, and the outer periphery of the support pile 5 is flat from the ground surface G to a depth of 10 m or less. It consists of a ground improvement body 6 that is locally formed so that the footing 4 is included by visual inspection.

  The ground improvement body 6 is obtained by stirring and mixing an in-situ soil and an improvement material such as a cement-based solidification material. By forming the ground improvement body 6 locally on the outer periphery of the support pile 5 from the ground surface G to a depth of 10 m or less, the ground reaction force coefficient is increased and the horizontal deformation and bending moment of the support pile 5 are reduced. can do. Particularly when the liquefied layer is shallower than 10 m, it is very effective.

Next, a method for constructing a pile foundation according to the present invention will be described.
FIG. 2 is a schematic sectional elevation view showing an example of a pile foundation construction method according to the present invention.
First, as shown in FIG. 2 (a), a plane from the ground surface G to a depth of 10 m or less is formed in the soft layer 2 by using an inexpensive shallow / middle ground improvement method such as the power blender method or the Elmud method. The ground improvement body 6 is formed so that the footing 4 is included visually.
Next, as shown in FIG. 2 (b), the support pile 5 is driven into the ground improvement body 6 so that the pile tip portion 5 a reaches the support layer 3.
Then, as shown in FIG.2 (c), the footing 4 is constructed | assembled on the pile head 5b.

  In the pile foundation and its construction method according to the present embodiment, the ground improvement body 6 is locally formed on the outer periphery of the support pile 5 from the ground surface G to a depth of 10 m or less, so that the support pile 5 against the horizontal force during an earthquake can be obtained. The burden can be reduced at a low cost and in a short construction period.

  As mentioned above, although the embodiment of the pile foundation which concerns on this invention, and its construction method was described, this invention is not limited to said embodiment, In the range which does not deviate from the meaning, it can change suitably.

It is a schematic elevation sectional view showing an example of an embodiment of a pile foundation concerning the present invention. It is a general | schematic elevational sectional view which shows an example of the construction method of the pile foundation which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground 2 Soft layer 3 Support layer 4 Footing 5 Support pile 6 Ground improvement body

Claims (2)

  A footing constructed on the ground with a soft layer on the ground surface side and a support layer under the soft layer, and a support pile in which the pile tip reaches the support layer and the pile head is joined to the footing And a ground improvement body formed on the outer periphery of the support pile from the ground surface to a depth of 10 m or less. It is a construction method of a pile foundation constructed on the ground having a soft layer on the ground surface side and a support layer under the soft layer,
After the ground improvement body is formed in the soft layer from the ground surface to a depth of 10 m or less, a support pile is placed in the ground improvement body so that the tip of the pile reaches the support layer. A pile foundation construction method characterized by forming a footing on the head.

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