JP2005061172A - Pile head structure of pile foundation and pile head reinforcement method of pile foundation - Google Patents

Abstract

[PROBLEMS] To increase shear resistance near a pile head of a pile foundation and increase resistance to horizontal load during an earthquake.
A pile head structure of a pile foundation 2 in which a replacement material 6 having a large volume expansion (dilatancy) due to shear strain is embedded in the ground 1 around the pile head of the pile foundation 2. The horizontal force applied to the pile head can be diffused and absorbed by the replacement material 6 embedded around the pile head. Further, when the horizontal force is large, the replacement material 6 receives the shearing force and expands in volume, thereby restraining the pile head and obtaining a large shear resistance.
[Selection] Figure 1

Description

  The present invention relates to a pile head structure of a pile foundation embedded in the ground and a pile head reinforcement method of the pile foundation.

  The role of the foundation is to fix the building to the ground 1, and to prevent the building from sinking, moving sideways, or rising due to vertical load such as its own weight or seismic force.

  When building pillars are placed across the railway track at Hashigami Station or artificial ground 1 etc., the structure of supporting one pillar with one pile foundation is omitted, in order to facilitate construction. It has become standard. Since this structure reduces resistance to horizontal loads during an earthquake, measures such as increasing the pile diameter are taken so as not to cause harmful displacement at the pile head.

  There is also a method of increasing the effective stress in the horizontal direction in the vicinity of the pile head by mixing or injecting a chemical solution such as a cement-based solidifying agent into the surface layer of soft ground to improve the ground (see, for example, Patent Document 1).

On the other hand, dense soil particles and rocks have a property (dilatancy characteristics) that tends to expand due to shear force, and it has been proposed to reinforce a loose ground (for example, non-patent literature) 1).
Japanese Patent No. 3127275 Matsuoka Moto, Liu Sishiro “Research on Strengthening Method of Support Strength Enveloping Part of Ground”, Journal of Japan Society of Civil Engineers, March 1999, Vol. 617, III-46, p. 235-249

  However, increasing the pile diameter beyond the thickness required to support the vertical load to increase the resistance to horizontal load has been uneconomical because of the increased material used for the pile foundation.

  Also, in the method of improving the ground by mixing or injecting chemical solution such as cement solidifying agent into the surface layer of soft ground, it is necessary to improve the ground in a wide range around the pile, the cost of the chemical solution to be used and the labor to mix with the ground, There was a problem that it took time to cure.

  An object of the present invention is to increase the shear resistance by increasing the dilatancy in the vicinity of the pile head of the pile foundation, and to increase the resistance to a horizontal load during an earthquake.

  In order to solve the above-mentioned problems, the invention described in claim 1 is a pile head structure of a pile foundation 2, wherein the ground 1 around the pile head of the pile foundation 2 has a volume expansion (dilatancy) caused by shear strain. A large replacement material 6 is embedded.

  Here, examples of the replacement material 6 having a large volume expansion associated with the shear strain include crushed stone and earthen sand filled with crushed stone. According to the first aspect of the present invention, the horizontal force applied to the pile head can be diffused and absorbed by the replacement material 6 embedded around the pile head. Further, when the horizontal force is large, the replacement material 6 receives the shearing force and expands in volume, thereby restraining the pile head and obtaining a large shear resistance.

  Invention of Claim 2 is the pile head structure of the pile foundation 2 of Claim 1, Comprising: The sand-proof sheet | seat 5 is laid between the said replacement material 6 and the ground 1, It is characterized by the above-mentioned. To do.

  According to the second aspect of the present invention, by providing the sandproof sheet 5 for partitioning the crushed stone or the earthen sand filled with crushed stone and the ground 1, the surrounding earth and sand enters between the replacement materials 6 to cause ground subsidence. Can be prevented.

  The invention according to claim 3 is a pile head reinforcing method for the pile foundation 2, which excavates the ground 1 around the pile head of the pile foundation 2 and lays a sandproof sheet 5 in the excavated hole 4, 5 is filled with a replacement material 6 having a large volume expansion associated with shear strain from the top to the inside of the hole 4 and hardened.

  According to the third aspect of the present invention, the horizontal force applied to the pile head can be diffused and absorbed by the replacement material 6 filled and hardened around the pile head. Further, when the horizontal force is large, the replacement material 6 receives the shearing force and expands in volume, thereby restraining the pile head and obtaining a large shear resistance. Further, by providing the sandproof sheet 5 for partitioning the crushed stone or the sandbag filled with the crushed stone and the ground 1, it is possible to prevent the surrounding earth and sand from entering between the replacement materials 6 and causing the ground subsidence.

  According to the present invention, the horizontal force applied to the pile head can be diffused and absorbed by the replacement material 6 filled around the pile head. In addition, when the horizontal force is large, the replacement material receives a shearing force and expands in volume, thereby restraining the pile head and obtaining a large shear resistance. Moreover, this invention can be easily applied also to the reinforcement of the existing pile foundation.

  In addition, excavating the ground around the pile head, filling it with crushed stone or sandbag filled with crushed stone, and solidifying it, the construction can be completed in a short period of time compared to ground improvement.

  Hereinafter, embodiments of the present invention will be described in detail. In the pile head structure of the first embodiment, as shown in FIGS. 1 and 2, a pillar 3 such as a building is provided on a pile foundation 2 embedded in the ground 1. Moreover, the earth and sand near the pile head of the pile foundation 2 are removed, and the replacement material 6 is tamped and densely embedded.

  Here, as the replacement material 6, a material having a large dilatancy can be used, and specifically, a crushed stone, a sandbag filled with crushed stone, or the like can be used. As crushed stone, what is used for the ballast of a track | line, etc. can be used, for example.

  Note that a sandproof sheet 5 is laid between the replacement material 6 and the ground 1 so that surrounding earth and sand enter between the replacement material 6 and the ground does not sink. As the sandproof sheet 5, a vinyl sheet etc. can be used, for example. The sandproof sheet 5 is provided with a drain hole so that rainwater does not stay between the replacement materials 6.

  The pile head structure of this Embodiment can be formed as follows, for example. First, as shown in FIG. 3A, the pile foundation 2 is embedded in the ground 1. The pile foundation 2 may be provided by driving an existing pile, or may be provided by drilling the ground 1 and placing concrete in the drilled hole.

  Next, as shown in FIG.3 (b), the pile head vicinity of the pile foundation 2 is excavated, the earth and sand around a pile head are removed, and the hole 4 is formed. Next, a sandproof sheet 5 is laid in the hole 4.

  When the sandproof sheet 5 is laid in the hole 4, as shown in FIG. 3C, the replacement material 6 is filled into the hole 4 from above the sandproof sheet 5 and hardened. If the replacement material 6 is hardened and the gap between the replacement materials 6 is made small, when the replacement material 6 receives a horizontal force, the gap expands and the pile head can be restrained.

  As described above, the pile head structure of the present embodiment can be formed. According to the present invention, the horizontal force applied to the pile head can be diffused and absorbed by the replacement material 6 filled around the pile head. In addition, when the horizontal force applied to the pile head is large, the replacement material 6 receives the shearing force and expands in volume, thereby restraining the pile head and obtaining a large shear resistance.

  In addition, in the present invention, since the construction is performed by excavating the ground 1 around the pile head, filling the sandbag filled with crushed stone and crushed stone, and solidifying it, it is constructed in a short period of time compared with the ground improvement. It can also be applied to cases where construction time is limited, for example, when columns are provided between tracks.

  In addition, the present invention reinforces the pile head by excavating the ground around the pile head, filling it with crushed stone or sandbag filled with crushed stone, and solidifying it. Can be applied.

  In addition, in the above embodiment, although the column-shaped pile foundation was used, the shape is arbitrary, such as polygonal column shape. Moreover, the size of the sandbag filled with crushed stone and crushed stone can be arbitrarily changed so as to increase the dilatancy. Of course, the shape of the hole drilled around the pile head can be changed as appropriate.

It is a figure which shows an example of the pile head structure of this invention, and is a side view. FIG. (A)-(c) is a side view which shows the pile head reinforcement method of this invention.

Explanation of symbols

1 Ground 2 Pile Foundation 4 Hole 5 Sand Protection Sheet 6 Replacement Material

Claims (3)

  A pile head structure of a pile foundation characterized in that a replacement material having a large volume expansion associated with shear strain is embedded in the ground around the pile head of the pile foundation.   The pile head structure of a pile foundation according to claim 1, wherein a sandproof sheet is laid between the replacement material and the ground. Excavating the ground around the pile head of the pile foundation, laying a sandproof sheet in the excavated hole, filling the hole from the top of the sandproof sheet with a replacement material with a large volume expansion due to shear strain and tamping it The pile head reinforcement method of the pile foundation characterized.

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