JPH01250514A - Liquefaction-proof construction for poor subsoil - Google Patents

Abstract

PURPOSE:To enable drainage to be executed without laying a gravel mat, by embedding drain piles consisting of the gravels of crushed stones or the like, in poor subsoil, and by packing the gravels of the crushed stones in permeable longish bag bodies to be bridged between the heads of the piles. CONSTITUTION:In sandy ground W, a plurality of drain piles 1 consisting of the gravels G of crushed stones or the like are embedded at mutually fixed intervals. After that, drain piles 3 formed by packing the gravels G in longish screen-formed bag bodies 2 are bridged to come in contact with the head sections of the respective drain piles 1, and the end sections of the lines of the respective drain piles 3 are extended outside a site. On the piles 3, sand or the like is put, and a foundation layer T is formed. As a result, comparing with the case of forming a gravel mat on ground surface, drainage can be executed by using fewer gravels.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a method for installing a required number of drain piles made of highly permeable gravel (crushed stone, gravel, slag, etc.) in soft ground, especially sandy ground that is easily liquefied. By burying them, when the pore water pressure in the sandy ground increases during an earthquake, the moisture in the ground will be sucked up and discharged to the ground through these drain piles, thereby causing the sandy ground to lose its bearing capacity during an earthquake. Concerning construction methods to prevent liquefaction of soft ground to make the ground safe.

(Prior Art) In this type of construction method, water discharged to the ground through drain piles is generally caused to flow out of the ground of a predetermined site by means of a gravel mat laid on the ground surface. However, since this gravel mat is laid almost entirely on the ground of the site, a large amount of gravel is required to form this mantle, which is one of the causes of soaring construction costs. .

Therefore, instead of such a gravel mat, a water permeable pit is formed by connecting the heads of each drain pile with gravel, and this permeable pit allows water discharged to the ground to flow out of the site ground. Such a construction method is disclosed in Japanese Unexamined Patent Publication No. 56-89619. This permeable pit requires only a small amount of gravel, which reduces construction costs.

(Problem to be Solved by the Invention) According to the above-mentioned enemy-like permeable pit, since gravel is simply piled up in an enemy-like manner, this permeable pit is likely to collapse if earth and sand is placed on top of it. In addition, when there is a problem with rain, the soil particles from the rain invade the gravel gaps in the permeable pit and cause clogging, which obstructs the permeability function of the permeable pit and prevents drainage. There is a problem.

The present invention aims to provide a method that can solve these problems.

(Means for Solving the Problems) In order to achieve the above object, the construction method of the present invention provides a drain pillow in which a drain pile is filled with gravel such as crushed stone in a water-permeable long bag. is characterized in that it is spanned so as to be in contact with the head of each drain pile.

(Example) An example of the construction method of the present invention will be described with reference to the drawings. As shown in Figures 1 and 2, a drain made of gravel G such as crushed stone is installed on soft sandy ground W within a predetermined site A. The required number of piles 1 are mathematically installed at regular intervals from each other. At this time, each drain pile l has its head raised slightly above the surface H of the sandy ground W. Therefore, drain piles 3 made by bagging gravel G similar to the gravel of the drain piles 1 in long mesh bags 2 are attached to these drain piles 1 . When installing a drain pile 3 to each drain pile 1 so that it is in contact with the head of the drain pile 1, as shown on the right side of Fig. The left f! As shown in l'1, the intermediate portions of the seven drain piles 3 may be placed on the head of the drain pile l.

In addition, in this embodiment, as shown in FIG.
Although the drain piles are installed in a straight line above the heads of the drain piles 1, they may also be installed vertically and linearly along the vertical and horizontal drain piles 1. 1... May be laid over the base in the shape of a base, or the first
As is clear from the figure, the ends of each row of drain piles 3 extend outside the site A.

The mesh bag 2 of the drain pile 3 has a mesh smaller than sand particles, and is made of synthetic resin such as vinyl chloride.

In this way, drain pile 3... is connected to drain pile L...
- Once the bridges have been built over the head, soil or the like is poured over them to form, for example, a base W4T.

According to the sandy ground W improved by the construction method described above, when the pore water pressure of the sandy ground W increases during an earthquake, water in the sandy ground 5iW passes through each drain pile 1 (sucked up to the ground side and , is passed through the head of each drain pile 1 to each drain pile 3 connected thereto, and is flowed and discharged to the outside of the predetermined site A through this drain pile 3, thereby preventing liquefaction of the sandy ground W. In such a case, if the base layer T is in a muddy state due to rain, etc., sand, etc. in the muddy soil will try to flow into the gravel G of the drain pile 3 along with water, but this gravel G is Since the mud is packed in a mesh bag 2, sand particles in the mud are prevented from entering the inside by this mesh bag 2, and only soil particles with extremely small particle sizes can enter the inside, so that this No clogging occurs inside the gravel G of the drain pile 3.

In addition, it is desirable that the drain pile 1 buried in the sandy ground W be packed in a water-permeable bag like the drain pile 3, but the pore water pressure in the sandy ground during an earthquake is quite high. Therefore, even if some clogging occurs due to sand particles inside the drain pile 1, the moisture in the sandy ground W is relatively easily discharged to the ground, and therefore it is not necessarily necessary to pack it into bags.

The above-mentioned drain pile l is constructed by inserting a rotationally driven casing with screws on the outer circumferential surface or a casing driven by a machine to a predetermined depth into the ground, and filling the casing with gravel. , can be created by pulling out the casing while pressurizing the filled gravel. To form the drain pile 3, only the long bag body 2 is placed on the upper surface of the ground where the drain pile 1 is buried. is placed horizontally so as to be in contact with the head of the drain pile 1, and the closed end of the bag body 2 is properly fixed to the upper surface of the ground, and the open end is raised to an appropriate height. It can be formed by sequentially filling gravel from the closed end side using a hopper.

In this example, an example was explained in which the drain pile was buried so that its head was almost located near the ground.
In the case of a site ground for a building with a basement, such as a second or third floor, a concave part of a considerable depth is excavated from the ground, and for drain piles buried in such a site ground. Since the difference in height between the pile head and the ground surface is quite large, it becomes difficult to drain water to the ground using the drain piles themselves, which are installed between the drain piles. Therefore, in such a case, a drain pipe may be constructed in an inclined manner from the drain pile to the ground level, and the water may be drained through the drain pipe.

(Effects of the Invention) According to the present invention, a drain pillow made of gravel such as crushed stone packed in a long, water-permeable bag body is mounted on the drain pile in contact with the head of each drain pile. By passing it over, the amount of gravel used is much smaller than with conventional gravel mantles, and when covering the top of the drain pile with earth and sand, there is no risk of it collapsing like with conventional permeable pits. In the present invention, even if the sand, etc. covering the retrain pillow becomes muddy due to rain etc., the sand, etc. is prevented from entering the inside by the water permeable bag body.
Clogging inside the drain pillow can be prevented, thereby allowing the drainage function to be fully exhibited and allowing good drainage to be performed.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of the present invention, in which the drain pile is not covered with earth and sand, and FIG. 2 is an enlarged sectional view taken along the line nn of FIG. 1. W...soft sandy ground, G...gravel, 1...drain pile, 2...mesh bag (water permeable bag), 3...
drain pile. -9;

Claims (1)

[Claims] In a method for preventing liquefaction of soft ground, a required number of drain piles made of gravel such as crushed stone are buried in soft ground, and moisture in the soft ground is sucked up and discharged to the ground through these drain piles. , a construction method for preventing liquefaction of soft ground, characterized by constructing a drain pillow made by packing gravel such as crushed stone in a water-permeable long bag so as to be in contact with the head of each drain pile.