JPH1025732A - Foundation pile method in liquefied ground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To install a perfect liquefaction preventive means to the foundation pile section of a structure by a simple technique. SOLUTION: A casing 1 is built while discharging soil and sand up to a liquefied stratum. A foundation pile 3 having an inside diameter smaller than the inside diameter of the casing 1 is driven up to the depth of a bearing ground 4 while being conformed to the center of the casing 1, a clearance between the casing 1 and the foundation pile 3 is filled with crushed stones 5, the casing 1 is extracted, and crushed stones 5' are laid continuously even on the ground surface GL of the upper section of the foundation pile 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foundation pile method in liquefied ground.

[0002]

2. Description of the Related Art As a method of constructing a foundation, a method of driving and constructing a foundation pile is generally used. Normally, if there is a possibility of liquefaction due to an earthquake etc. in the ground where the foundation pile is installed, consider the degree of liquefaction of the ground and design the thickness, outer diameter and arrangement of the foundation pile with a low ground constant. .

As a means for preventing liquefaction, a crushed stone drain formed of crushed stone columns is formed from the lower part and the side of the structure to the supporting ground, and water due to liquefaction is caused to flow out through the crushed stone. A construction method is known (prior art 1).

FIGS. 14 (a), 14 (b), 14 (c) and 14 (d) are views showing examples of the crushed stone drain method for preventing liquefaction of the foundations of various structures according to the prior art 1. FIG. 14 (a) is a diagram showing a countermeasure against liquefaction of the ground of the underground buried object 6. It is a structure that prevents liquefaction of the ground by overflowing the ground. Note that S
L is a supporting ground.

FIG. 14 (b) shows an example of liquefaction prevention measures for the moat road 8, and FIG. 14 (c) shows an example of liquefaction prevention measures for the seawall 9.
FIG. 14 (d) is a diagram showing an example of measures for preventing liquefaction of the existing tank 10. Similar to FIG. 14 (a), the crushed stone drain 7 is provided in the vicinity of each structure so that the water due to liquefaction can be reduced. This is to prevent liquefaction of the ground by overflowing to the surface (GL).

FIGS. 15A and 15B show the aforementioned FIGS. 14A and 14B.
(C) The pile plan of the continuous footing foundation used in the prior art 1 of (d), 7 is a crushed stone drain, 3 is a foundation pile, 11
Is footing.

FIG. 16 is a pile plan of a single foundation according to the prior art 1, in which 3 is a foundation pile, 7 is a crushed stone drain, and 11 is a footing.

As can be seen from FIGS. 15 and 16, in these construction methods, the foundation pile 3 is provided at the place where the footing 11 is provided, and the crushed stone drain 7 is provided around the footing 11. And the crushed stone drain 7 are separated.

As a technique different from the prior art 1, Japanese Patent Publication No. Sho 6
Japanese Patent Laid-Open No. 1-51093 (pile method on liquefied ground) discloses a method of integrally forming the crushed stone drain on the outer periphery of a foundation pile, "a bottom plate is provided at the tip and a spacer is provided in the height direction. The technique of embedding a casing whose outer periphery is divided into a plurality of pieces in the ground around a foundation pile, filling a highly permeable material such as crushed stone between the foundation pile and the casing, and pulling out the casing one by one while leaving a bottom plate. '' (Prior art 2) is described.

Furthermore, Japanese Patent Publication No. Hei 6-51967 (Liquefaction prevention construction method and foundation pile) states that
After penetrating a foundation pile wound with a drain material made of a water-permeable membrane such as a natural fiber sheet through the liquefaction countermeasure formation and into the supporting ground, horizontal drainage between the lower layer of the upper building and the liquefaction countermeasure formation is performed. With a water-permeable layer for use "(Prior art 3)
Is described.

[0011]

However, the prior art 1 is a method in which the foundation of the structure is a foundation pile and the surrounding area is a crushed stone drain. Therefore, since the foundation pile and the crushed stone drain are arranged separately, there is a problem that a complete liquefaction prevention means cannot be taken in the foundation pile part of the structure.

In the prior art 2, the foundation pile and the crushed stone drain are integrated, but it is necessary to prepare a casing having special parts such as a bottom plate and a spacer, which increases the cost. Furthermore, there are problems such as vibration and noise caused by casting the casing.

In the prior art 3, it takes time and effort to wind a sheet of natural fiber or the like around the foundation pile, and the foundation pile on which the sheet is wound has a large frictional resistance, which makes it difficult to cast. There's a problem.

The present invention has been made in order to solve these problems, and an object of the present invention is to provide a simple liquefaction preventing means in a foundation pile portion of a building by a simple construction method.

[0015]

A first means for solving the above-mentioned problem is to build a casing while discharging earth and sand to a liquefied formation, and then align the casing with the center of the casing and make the casing smaller than the inner diameter of the casing. Driving the foundation pile to the depth of the supporting ground, filling the gap between the casing and the foundation pile with the granular material, extracting the casing, and then continuously laying the granular material on the ground surface at the top of the foundation pile This is a foundation pile method in liquefied ground characterized by the following.

A second means for solving the above-mentioned problem is that the casing is extracted while compacting the granular material filled in the gap between the casing and the foundation pile in the step of extracting the casing. It is a foundation pile construction method in the liquefied ground described.

[0017]

1 (a), 1 (b), 1 (c), 1 (d)
FIG. 2 is a cross-sectional view illustrating an example of a process of a foundation pile method in the liquefied ground of the present invention.

First, as shown in FIG. 1 (a), a casing 1 is arranged by an all-casing method, a grab hammer 2 is set inside, and the casing 1 is buried to a liquefied stratum while excavating the soil with the grab hammer 2. I do.

Next, as shown in FIG. 1 (b), the foundation pile 3 is driven into the supporting ground 4 by a known driving means while being aligned with the radial center of the buried casing 1. Vibration, a hydraulic hammer or the like is used for driving.

When the foundation pile 3 is driven, the granular material 5 is placed between the casing 1 and the foundation pile 3 as shown in FIG.
For example, the crushed stone is filled, and then the casing 1 is pulled upward and removed to complete the drain.

When the crushed stone 5 is filled, as shown in FIG. 1D, a crushed stone 5 'which is a granular material is laid on the ground GL.
The structure is such that moisture around the foundation pile 3 overflows onto the ground GL.

FIG. 2 shows a process of filling the granular material 5, for example, crushed stone, between the casing 1 and the foundation pile 3 in the foundation pile method in the liquefied ground of the present invention, and then pulling the casing 1 upward. FIG. 4 is a side sectional view of a means for squeezing the granular material 5.

Reference numeral 1 denotes a casing, 3 denotes a foundation pile, and 4 'denotes a peripheral ground. A tamping tool 100 is provided on the lower inner surface side of the casing 1.

The tamping tool 100 is shown in FIG.
(A sectional view), a plurality of portions are provided on the inner peripheral surface of the casing 1.

The tamping tool 100 is shown in FIG.
As shown in FIG. 5 (front view) and FIG. 6 (plane enlarged view), the shape is a triangular pyramid including inclined surfaces 100a, 100b, and 100c, and the bottom surface is flat.

FIG. 7 is a side sectional view of another means for compacting the granular material 5. As shown in FIG. 1 is a casing, 3 is a foundation pile, and 4 'is a surrounding ground, and a tamping tool 101 is provided on the lower inner surface side of the casing 1.

The ramming tool 101 is shown in FIG.
As shown in FIG. 2B), a plurality of portions are provided on the inner peripheral surface of the casing 1.

The tamping tool 101 is shown in FIG.
As shown in FIGS. 10 (front view) and 11 (enlarged plan view), a triangular pyramid composed of inclined surfaces 101a, 101b, and 101c, and a wedge-shaped projection 101d on the bottom surface are further provided.

At the end of the casing 1,
By providing 0 or 101 and pulling out the casing 1 while applying longitudinal vibration to it, the granular material 5 such as crushed stone is compacted and the surrounding ground 4 ′ is compacted. After the tamping operation, the casing 1 is pulled up.
Flows down along the side of the tamping tool 100 or 101,
Go under the tamping tool 100 or 101.

As described above, by repeating the compacting operation and the rocking and lifting operation, the granular material 5 is extruded in the lateral direction, the density increases, the surrounding ground 4 'is tightened, and the lateral resistance of the foundation pile 3 is evaluated. There is an effect that the ground constant to be raised is increased and a foundation pile having a large lateral resistance is obtained.

FIG. 12 is a pile plan view of a foundation using the foundation pile method in the liquefied ground of the present invention. A is a drain in which crushed stones 5 are buried around a foundation pile 3 constructed by the foundation pile construction method of the present invention, 3 is a single foundation pile, 7 is a conventional crushed stone drain, and 11 is footing.

FIG. 13 is a pile plan view of a foundation using the foundation pile method of the present invention for a single foundation. The drain A of the present invention is arranged in the footing 11 by mixing with the foundation pile 3. In addition, a conventional crushed stone drain will be placed around it.

As can be seen from FIGS. 12 and 13, it is not always necessary to apply the method of the present invention to all the foundation piles 3 in the footing 11. This method should be applied.

[0034]

As described above, according to the present invention, since the foundation pile and the drain made of the granular material are arranged integrally, the liquefaction of the foundation pile part of the building can be completely prevented. Become.

Further, by using the drain according to the present invention together with the conventional crushed stone drain, flexibility in measures for liquefaction of the entire pile foundation can be obtained, and an effective arrangement of the drain can be obtained.

Further, since the crushed stone is arranged around the foundation pile, the drain diameter increases, and the drainage area of the drain increases. Therefore, since the arrangement interval of the drains can be increased, the number of drains per area can be reduced.

In addition, since the casing is penetrated, pulled out and the foundation pile is driven by using existing construction machines, it can be easily constructed with low noise and low vibration.

In addition, the provision of the tamping tool at the tip of the casing increases the density of the granular material, tightens the surrounding ground, and provides a foundation pile with a large lateral resistance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of steps of a foundation pile construction method in liquefied ground according to the present invention.

FIG. 2 is a side sectional view of a granular material tamping tool used in the foundation pile method in the liquefied ground of the present invention.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a side sectional view of the tamping tool according to the present invention.

FIG. 5 is a front view of the tamping tool according to the present invention.

FIG. 6 is an enlarged plan view of the tamping tool according to the present invention.

FIG. 7 is a side sectional view of another granular material tamping tool used for the foundation pile method in the liquefied ground of the present invention.

FIG. 8 is a sectional view taken along line BB of FIG. 7;

FIG. 9 is a side sectional view of another tamping tool according to the present invention.

FIG. 10 is a front view of another tamping tool according to the present invention.

FIG. 11 is an enlarged plan view of another tamping tool according to the present invention.

FIG. 12 is a pile plan view showing an example of a continuous footing foundation using a foundation pile method in liquefied ground according to the present invention.

FIG. 13 is a pile plan view showing an example of a single foundation using the foundation pile method in the liquefied ground according to the present invention.

FIG. 14 is a diagram showing an application example of a crushed stone drain according to the related art.

FIG. 15 is a pile plan view of a continuous footing foundation used in the prior art.

FIG. 16 is a pile plan view of a single foundation used in the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 100 Tumbling tool 101 Tumbling tool 2 Grab hammer 3 Foundation pile 4 Supporting ground 4 'Surrounding ground 5 Granular material (crushed stone) A Drain formed by the present invention 6 Underground buried object 7 Crushed stone drain 8 Drilling road 9 Seawall 10 Existing tank 11 Footing

Claims (2)

[Claims] 1. A casing is erected while discharging earth and sand to a liquefied stratum, and then a foundation pile smaller than the casing inner diameter is driven to the depth of a supporting ground so as to coincide with the center of the casing. A foundation pile method in a liquefied ground, characterized in that a granular material is filled in a gap between piles, a casing is extracted, and then the granules are continuously laid on the ground surface above the foundation pile. 2. The method according to claim 1, wherein in the step of extracting the casing, the casing is extracted while compacting the granular material filled in the gap between the casing and the foundation pile.