JPS6365771B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for constructing cast-in-place concrete piles in soft ground zones.

When installing structures, structures, works, etc. on soft ground, piles are installed that reach the bedrock beneath the soft ground, and the bearing capacity of the bedrock is supported through these piles to support these structures. It is necessary to construct it. In such cases, there is a method of driving precast concrete piles, or rotating a drilling bucket attached to the tip of a square rod called a kelibar to capture the earth and sand, and then rolling it upward to remove the earth and sand. Known methods include the earth drill method, which uses a rotating bit to suck out the excavated earth and sand through a drill pipe, along with water, and the Benoto method, which uses a casing tube to push it into the ground while shaking it. ing. However, all of these methods require large construction equipment and cannot avoid problems such as vibration and noise, the problem of discharging leftover soil, and the contamination of the construction site due to the use of water.

For example, FIGS. 1a to 1c show an example of a conventional method for constructing cast-in-place concrete piles. First, the soft ground 1 has a diameter of 500 to 600 mm reaching from the ground surface 2 to the bedrock 3.
Drill a borehole 4 inside. Next, a concrete stake 5 having a diameter of 1000 to 1200 mm is mechanically driven into this hole. Since this pile 5 has a considerably larger diameter than the borehole 4, the ground around the pile is strengthened by driving the pile. In this traditional method,
Since a hole with a relatively large diameter is excavated, it is necessary to use a large excavator, which increases the construction cost. On the other hand, a large amount of soil is discharged, so it is necessary to carry out this discharged soil, and it is necessary to secure a place to dump it. In short, a large amount of drilling water is used to reduce the resistance between the drilling drill and the soil during drilling, which deteriorates the working environment. Further, when driving piles, a large pile driving machine is required, which causes noise and vibration, and there are also problems such as muddy water generally coming out from the soil and contaminating the surrounding area.

The purpose of the present invention is to solve the above-mentioned problems, and to provide a method for constructing cast-in-place concrete piles that can simultaneously construct any number of piles of any thickness, has a ground improvement effect, and is inexpensive in construction cost. shall be.

FIGS. 2a to 2g are process diagrams showing the steps of the present invention,
The present invention will be explained below with reference to FIG.

(a) First, a relatively small diameter bore hole 14 is drilled in the soft ground 1, reaching from the ground surface 2 to the bedrock 3. The borehole 14 may have a diameter of 50 to 100 mmφ. Since the hole is small in diameter, a small drill can be used, no large machinery is required, and only a small amount of soil is removed.The resistance between the drilling drill and the soil is also small, so a small amount of drilling water is sufficient, and the work environment is not contaminated.

(b) Insert an elongated bag 15 made of a highly elastic material into the borehole. This bag is, for example, shaped like a cylindrical rubber tube, with little elongation in the longitudinal direction and large elongation in the circumferential direction, and the diameter is expanded by supplying high-pressure fluid to the inside of the bag.

(c) Next, a high-pressure fluid 20 such as high-pressure air or high-pressure water is supplied to the bag 15 to inflate the bag 15 and enlarge the diameter of the bore hole. Bag body 15
The diameter of the borehole is expanded by supplying high-pressure fluid, which can expand up to 4 to 5 times the diameter of the borehole, and the diameter of the borehole is expanded.The diameter of the borehole is then expanded, and the borehole is left for a certain period of time until the ground around the hole is compressed and stabilized. The first diameter expansion will be approximately 150 to 300 mmφ in diameter. This dimension is determined by the inflation capacity of the bag 15 and is adjusted by the fluid pressure flowing into the bag 15 in accordance with the nature of the ground.

(d) After being left for a certain period of time, the fluid pressure inside the bag 15 is reduced, the bag 15 is taken out from the hole 14, and then,
In the second stage, the bag body 15a with a diameter of 150 to 300 mm is inserted into the hole 1.
Insert into 4. The bag 15a may be a single cylinder bag, but it may also be an assembly of a large number of small diameter cylinders, as shown in cross sections in FIGS. 3a to 3e, for example. Further, as shown in the side view in FIG. 4, the chamber may be divided into a large number of chambers in the longitudinal direction.

(e) Supply high pressure fluid to the bag body 15a to further enlarge the diameter of the hole 14.

If necessary, replace the bag with a larger diameter, repeat the operation of inflating by supplying pressure fluid, and finally expand the diameter of the hole 14 to 1000 to 1200 mm, and expand the inside of the highly elastic bag. The pressure consolidates the side walls of the holes 14.

The fluid pressure required for this diameter expansion varies depending on the ground, but may be 10 to 100 kg/cm ² . Such a fluid can be easily obtained by using an air compressor, a high pressure gas cylinder, a water pressure pump, or the like. In addition, the expansion of the hole in the longitudinal direction can be suppressed by incorporating canvas into the side wall of the bag body or by using an ^appropriate weight. It is sufficient to use a weight of about 12 tons when supplied with .

In addition, this diameter expansion work does not require a pile driver, and can be performed simultaneously on multiple boreholes, and the fluid can be replaced sequentially, making work more efficient. It is.

(f) After reaching the required hole diameter, drain the fluid inside the bag, remove the bag, and open the hole 14 where the bag was removed.
Pour fresh concrete into the container.

(g) After curing the concrete for the required number of days, the construction of the cast-in-place concrete pile 30 will be completed.

In the method of the present invention, no noise or vibration unlike conventional pile driving is generated during the diameter expansion and concrete pouring. Furthermore, since fresh concrete is used, there is no need to store or transport concrete piles, and there is no need for large pile driving machines.

Next, the bag 15 (or 1
An example of 5a) is shown in FIG. 5, and an example of its usage is shown in FIG. The bag 15 shown in FIG. 5 has a length of about 1 m.
The bag body 15 has one-touch connecting fittings 17 on the top and bottom, and canvas 16 is incorporated into the side wall of the bag body 15 at a constant pitch. 17, they can be easily connected in the longitudinal direction, and as shown in FIG. 6, the required number can be connected and used depending on the depth of the hole.

The advantages of the method of the present invention are summarized as follows.

(1) There is almost no need for soil disposal.

(2) There is no contamination of the working environment by drilling water.

(3) It does not require large machinery and can operate 24 hours a day without vibration or noise.

(4) High efficiency as multiple piles can be installed at the same time.

(5) It has a ground improvement effect because it consolidates the ground without soil removal.

(6) It is also possible to install piles with a larger diameter at the bottom.

(7) Overall, cast-in-place concrete piles can be constructed at low cost.

[Brief explanation of drawings]

Figures 1 a to c are sectional views of the ground showing steps of an example of the conventional pile driving method; Figures 2 a to g are sectional views of the ground showing steps of an embodiment of the present invention; A cross-sectional view illustrating a bag used in the invention, FIG. 4 is a vertical cross-sectional view thereof, FIG. 5 is a vertical cross-sectional view of the bag, and FIG.
The figure is a cross-sectional view of the construction part of the present invention, showing a state in which the bags of FIG. 5 are connected. 1...Soft ground, 2...Ground surface, 3...Bedrock, 4
...Large diameter borehole, 14...Hole according to the present invention (small diameter borehole or enlarged hole thereof), 1
5, 15a... Highly elastic bag body, 16... Canvas, 1
7...Connection fitting, 20...High pressure fluid, 30...Piece according to the present invention.

Claims (1)

[Claims] 1. A small-diameter borehole is drilled in soft ground from the ground surface to the bedrock, a single or multiple elongated bag body made of a highly elastic material is inserted into the hole, and high-pressure fluid is flowed into the bag body. The bag is inflated to enlarge the diameter of the borehole and the hole wall is compacted. After reaching the required hole diameter, the bag is removed and ready-mixed concrete is poured into the hole where the removed hole remains to create cast-in-place concrete. A method for constructing cast-in-place concrete piles in soft ground zones, which is characterized by forming piles.