JPH0649840A - Construction method of steel pipe foundation pile for preventing liquefaction - Google Patents

Abstract

PURPOSE:To prevent the liquefaction of water-containing soft ground surely by a simple means. CONSTITUTION:A casing pipe 1 is pressed into the water-containing soft ground 2, and a vertical hole 5, which reaches the support ground 4, is drilled by a drilling machine inserted into the casing pipe 1. The base protecting concrete 6 is placed into the vertical hole 5 under the support ground 4, and thereafter, the lower part of a steel pipe pile 7, which is inserted to the vertical hole 5, is inserted to the base protecting concrete 6. The casing pipe 1 is drawn out, and a clearance between the steel pipe pile 7 and the peripheral wall of the vertical hole 5 is filled with the crushed stone to form a crushed stone pillar 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of constructing a liquefaction-suppressing steel pipe foundation pile to be installed on a water-containing soft ground.

[0002]

2. Description of the Related Art Conventionally, a water-containing soft ground (for example, as a construction method of a liquefaction-suppressing steel pipe foundation pile installed in a water-containing sand layer, as disclosed in Japanese Patent Laid-Open No. 64-10819), a water-containing soft ground in a steel pipe pile. To the position where
Providing a large number of drain holes with a net for preventing sediment inflow,
A method is known in which a steel pipe pile having the net-stretched drainage holes is placed on the soft ground containing water.

[0003]

In the case of the conventional liquefaction-suppressing steel pipe foundation pile construction method, since the steel pipe pile is provided with a large number of drain holes, the structural strength of the steel pipe pile is reduced and The net stretched over the hole may become clogged with the lapse of usage period, and may also be clogged due to water permeation at the time of an earthquake.When the net is clogged, the soft ground is liquefied. There is a problem of losing the effect of suppression. An object of the present invention is to provide a method for constructing a liquefaction-suppressing steel pipe foundation pile that can advantageously solve the above problems.

[0004]

In order to advantageously solve the above problems, in the method for constructing a liquefaction-suppressing steel pipe foundation pile of the present invention, the casing pipe 1 is pressed into the water-containing soft ground 2 while the casing is being pressed. After excavating the vertical hole 5 reaching the support ground 4 by the excavator 3 inserted in the pipe 1, and then placing the concrete 6 into the vertical hole 5 in the support ground 4,
The lower part of the steel pipe pile 7 inserted into the vertical hole 5 is inserted into the root-consolidating concrete 6, and then while the casing pipe 1 is being pulled out, crushed stones are filled between the steel pipe pile 7 and the peripheral wall of the vertical hole 5. The crushed stone pillar 8 is configured.

[0005]

The present invention will now be described in detail with reference to the examples shown in the drawings. When constructing a liquefaction-suppressing steel pipe foundation pile by carrying out the present invention, first, as shown in FIG. 1, a steel casing pipe 1 is press-fitted into a water-containing soft ground 2 while being inserted into the casing pipe 1. Vertical hole 5 by screw type excavator 3
When the vertical hole 5 penetrates the water-containing soft ground 2 and reaches an appropriate depth of the support ground 4, the vertical hole 5 is stopped and the excavator 3 is pulled out.

Next, as shown in FIG. 2, when the concrete for consolidation 6 is placed in the vertical hole 5 in the support ground 4 and then the concrete for consolidation 6 is in a semi-hardened state, the steel pipe pile 7 is vertically drilled. 5, the lower part of the steel pipe pile 7 is inserted into the root-consolidating concrete 6, and the upper part of the steel pipe pile 7 is held at the central position of the upper part of the casing pipe 1 by the holder 11. To do.

Next, after the concrete for consolidation 6 hardens, as shown in FIG. 3, while pulling out the casing pipe 1, crushed stone is filled between the steel pipe pile 7 and the peripheral wall of the vertical hole 5 to form the crushed stone column 8. Constitute. After constructing a large number of liquefaction-preventing steel pipe foundation piles in this way, as shown in FIG. 4, a crushed stone layer 9 is laid on the water-containing soft ground 2, and the upper portion of the steel pipe pile 7 is cut at an appropriate position. Then, a concrete foundation footing 10 is applied on the crushed stone layer 9, and the upper portion of the steel pipe pile 7 is embedded in the foundation footing 10.

When the liquefaction-suppressing steel pipe foundation pile is constructed as described above, when the hydrous soft ground 2 is about to liquefy due to an earthquake, the water content of the hydrous soft ground 2 rises through the crushed stone columns 8. Since the water is discharged and liquefaction of the water-containing soft ground 2 is suppressed, a decrease in the bearing capacity of the steel pipe pile 7 due to the liquefaction of the water-containing soft ground 2 is prevented.

[0009]

Since the present invention is constructed as described above, it has the following effects. When the hydrous soft ground 2 is about to be liquefied due to an earthquake, the water content of the hydrous soft ground 2 enters the crushed stone pillar 8 from the entire circumference of the crushed stone pillar 8 and ascends and discharges. Liquefaction can be surely prevented, and therefore safety at the time of an earthquake can be improved, and water can be absorbed from the entire circumference of the crushed stone column 8, so that it can be used like a net stretched over a conventional drainage hole. It is possible to suppress liquefaction of the water-containing soft ground 2 for a long period of time without causing clogging, and, as in the case of the above-mentioned conventional case, to provide a large number of drain holes in the steel pipe pile,
Since it is not necessary to extend a net for closing the drainage holes in the steel pipe pile, the strength of the steel pipe pile 7 does not decrease, and the liquefaction-preventing steel pipe foundation pile can be constructed at low cost.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view showing a state in which a casing pipe is press-fitted into water-containing soft ground and a vertical hole is excavated by an excavator.

FIG. 2 is a vertical cross-sectional side view showing a state in which a steel pipe pile is built by filling a vertical hole of a supporting ground with a rooting concret.

FIG. 3 is a vertical cross-sectional side view showing a state in which crushed stones are filled between the steel pipe pile and the peripheral wall of the vertical hole while pulling out the casing pipe.

FIG. 4 is a vertical cross-sectional side view showing a state in which a foundation footing is installed on an upper portion of the completed liquefaction-suppressing steel pipe foundation pile.

[Explanation of symbols]

 1 Casing pipe 2 Water-containing soft ground 3 Excavator 4 Supporting ground 5 Vertical hole 6 Rooted concrete 7 Steel pipe pile 8 Crushed stone pillar 9 Crushed stone layer 10 Foundation footing

Claims (1)

[Claims] 1. A vertical hole 5 reaching a supporting ground 4 is excavated by an excavator 3 inserted into the casing pipe 1 while press-fitting a casing pipe 1 into a water-containing soft ground 2, and then a vertical hole in the supporting ground 4. 5, the bottom portion of the steel pipe pile 7 inserted into the vertical hole 5 is inserted into the root consolidation concrete 6, and then the casing pipe 1 is pulled out, while the steel pipe pile 7 and the vertical hole are formed. A method for constructing a liquefaction-suppressing steel pipe foundation pile in which crushed stone is filled between the peripheral wall of No. 5 and the crushed stone column 8.