JPH01239221A - Pressure proof rubber bag for precompressing ground at pile end - Google Patents

Abstract

PURPOSE:To compress the ground at the end of a pile so as to increase force for supporting the ground by arranging a rubber bag between the bottom of an excavated hole for pile installation, and charging pressure fluid into the bag so as to swell the same. CONSTITUTION:An excavated hole 2 is formed in the ground 1, and reinforced bar cage having a pressure proof rubber bag at the bottom is inserted therein. The bag is pressure charged with a charge material such as water cement milk and the like through a charge pipe 5 so as to harden concrete 8 in the form of a pile filled into the hole 2. It is thus possible to increase force for supporting the ground and prevent the foundation pile from sinking.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-resistant rubber bag used in a soil bearing capacity reinforcement method for supporting foundation piles of various M4'Ili objects constructed on the ground.

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Conventionally, when constructing foundation piles for a structure, a pit for pile construction is excavated in the ground, the excavated hole is filled with a stabilizing liquid such as bentonite suspension, concrete is poured, and then the excavation process is carried out. Foundation piles are constructed by replacing the stabilizing liquid in the holes with concrete.

In this construction method, the ground supporting the pile tip t111 is in a relaxed state due to the release of the soil by excavation, sedimentation of earth and sand in the stabilizing liquid, etc., and when a load is applied to the pile, the ground at the pile tip deforms. The disadvantage is that the pile length will have to be increased because the pile will sink significantly.

In addition, in conventional construction methods, in order to reduce the amount of settlement mentioned above, the bottom of the excavation hole is formed larger than the details using the so-called expanded pile method, ensuring a large pressure-receiving area of the ground. It's getting complicated.

・In order to overcome these drawbacks of conventional construction methods, it has been found that a method of pre-compressing the ground at the end of the pile to increase the supporting capacity of the foundation pile is effective. This method of increasing support capacity requires a pressure-resistant rubber bag that can be inflated by injecting fluid. It is therefore an object of the present invention to provide a pressure resistant rubber bag.

The object is a bag that expands into a substantially spherical shape when fluid is injected into the interior, and is equipped with a cap on the top wall that can simultaneously supply fluid to the interior and discharge fluid from the interior. This is accomplished by providing pressure-resistant rubber bags.

The soil bearing capacity reinforcement method for supporting foundation piles is a method in which a rubber bag is placed between the bottom of the excavated hole for pile construction and the tip of the foundation pile (referring to the bottom head), and pressurized fluid is injected into the rubber bag. This is a construction method in which the rubber bag is injected and expanded, and the surrounding ground in contact with the rubber bag is compressed by the expansion force of the rubber bag, by taking the reaction force from the load applied to the pile head and the peripheral friction force of the pile.

This construction method will be explained with reference to FIGS. 1 and 2.

■Example shown in FIG. 1: An excavated hole 2 is formed in the ground 1, and a reinforcing bar 813 is inserted inside it. A pressure-resistant rubber bag 4 is attached to the bottom of the reinforcing bar n3 in advance, and fluid is injected into the pressure-resistant rubber bag 4 through an injection pipe 5, and the fluid pressure is led out to the ground through a discharge pipe 6, and the pressure is 7 to measure the injection fluid pressure.

Next, pile frame concrete 8 is placed in the excavated hole 2, and after the poured concrete has hardened, a filler such as water and cement milk is pressurized into the pressure-resistant rubber bag 4 through the injection pipe 5. At this time, the degree of filling of the filler and the pressurizing pressure are measured through the outlet pipe 6.

As a result, the pressure-resistant rubber bag 4 expands, and the ground in contact with the pressure-resistant rubber bag 4 expands due to the expansion force of the pressure-resistant rubber bag 4, which is a reaction force to the load applied to the pile cap and the frictional force between the pile body and the surrounding ground. It is compressed and the bearing capacity of the ground increases. Note that the filler filled in the pressure-resistant rubber bag 4 is hardened under pressure.

■Illustrated example in Figure 2: This is an example of application to the embedded pile construction method. Either insert the pile body 9 into the excavated hole 2 with the pressure-resistant rubber bag 4 attached to the tip of the embedded pile body 9 in advance, or insert the pile body 9 into the excavated hole 2 through the hollow part 10. A pressure-resistant rubber bag 4 is inserted into the tip of the pile frame 9. Next, concrete 11 is poured into the hollow part 10 of the pile frame 9, and after the concrete 11 has hardened, the pressure-resistant rubber bag 4 is filled with a filler material under pressure in the same manner as the example shown in FIG. The ground in contact with the bag 4 is compressed under pressure.

Friend JLL Yu Hereinafter, a pressure-resistant rubber bag as an example used in the soil bearing capacity reinforcement method will be explained (Fig. 3).

The pressure-resistant rubber bag 12 is formed as a substantially spherical body (including a true spherical body) as shown in the figure. The pressure-resistant rubber bag 12 is made of a material with a high elongation rate (for example, 600 to 900
%) is preferable, and wall thickness<m thickness) (() is suitably 5#Il1 or more, and the relationship between outer diameter (D) and length (T1) is H
/D = 0.05~1 (therefore, H = 0.0
50-0) is preferable. However, this dimensional relationship applies when the pressure-resistant rubber bag 12 is filled with gas to such an extent that the membrane wall does not stretch. In addition, liquid is supplied to the top wall of the pressure-resistant rubber bag 12 into its inner chamber.

A cap 13, 14 is attached for ejection.

■The reason why the wall thickness ([) is set to 5#III or more is that if the wall thickness is too small, the pressure-resistant rubber bag 12 may expand and break when it comes into contact with pebbles or the like in the ground.

However, it is not necessary to make the wall thickness (1) excessively large, and in consideration of economic efficiency, it is appropriate to make it 15ffiI11 or less.

■Outer diameter 0 and length (The reason for changing the old ratio to N/D -0.05 to 1 is based on the pressure resistance test results.The pressure resistance test is based on the wall thickness (1
) is constant (t-10am) and the ratio (IIlo) is different from each other. (shape)), water is injected under pressure into the pressure-resistant rubber bag 12 through the cap 13 to inflate the pressure-resistant rubber bag 12, and the water pressure of the pressurized water drawn out through the cap 14 is measured. It was done by doing. The results are shown in Figure 4. According to the graph in FIG. 4, the smaller or larger the ratio (H/D) is, the lower the pressure-resistant strength of the pressure-resistant rubber bag 12 is, +1/D -0,0
It turns out that 5 to 1 is appropriate.

Next, a method for manufacturing the pressure-resistant rubber bag 12 will be explained.

■The top wall (bottom of the cup) has a bulging shape! A cup-shaped mold 15 made of No. 4 is prepared (FIG. 5).

■ A raw rubber plate 16 with a rectangular notch around the periphery is placed on the mold 15 whose surface has been coated with a mold release agent (Fig. 6...
(partially cutaway), the peripheral part of the raw rubber plate 16 is folded back and
Make it into a double layered shape as shown in the figure. At that time, a destination plate 17, which is a vulcanized rubber plate, is placed along the bent portion to prevent the wall thickness from becoming locally thin (Fig. 7), and a release paper is placed between the double rubber layers. 18 is interposed.

■Mold the double raw rubber plates 16 by folding them into a seamless integral piece and adjust the shape (
Figure 9).

■Cover the raw rubber plate 16 on the mold 15 with a steel cup-shaped mold 19 as an upper mold (Fig. 10), pressurize the raw rubber plate 16, heat the entire body, and vulcanize the raw rubber plate 16. conduct. Note that instead of using the mold 19, a canvas may be used to press the raw rubber plate 16.

(2) By vulcanization molding, a bowl-shaped vulcanized rubber molded product 20 as shown in FIG. 11 can be obtained.

■A pair of openings 21 in the membrane wall on the concave side of the vulcanized rubber molded product 20
．． 22, and a tubular cap 13, 14 having a flange is bonded to the opening 21, 22 with an adhesive. A female thread or a male thread is formed in advance at the tip of the cap 13, 14 so that an injection pipe and a discharge pipe can be connected thereto, respectively. In this way, the desired pressure-resistant rubber bag 12 can be obtained (12th
figure).

Tomb Blind ■'' Pressure-resistant rubber bag 12 with dimensions shown in Figures 13 and 14
A and 12B were prepared. In addition, pressure-resistant rubber bag 12^.

Lead foil was attached to the entire surface of 12B to observe the state of elongation and deformation.

■As shown in Figure 15, fill the steel cylindrical container 23 with sand 24 to about half its depth, place the pressure-resistant rubber bag 12A (or pressure-resistant rubber bag 12B), which is the test specimen, on the sand, and fill the remaining 24 pieces of sand were charged. At that time, in order to prevent deformation of the pressure-resistant rubber bag 12A (or pressure-resistant rubber bag 12B) in the radial direction (arrow A),
) was surrounded by tin roots 25.

■While applying a load to the upper surface of the sand 24 with the pressing body 29, water is injected under pressure into the pressure-resistant rubber bag 12^ (or pressure-resistant rubber bag 12B) through the injection pipe 26 connected to the mouthpiece 13, and the water is injected into the mouthpiece 14. The water pressure taken out to the outside through the connected outlet pipe 27 was measured with a pressure gauge 28.

■Pressurization was carried out in two stages. That is, in the first stage, the water pressure was set to 20 kof/cII, and after the water pressure was released, the second stage of pressurization was performed. As a result, the pressure-resistant rubber bag 12B broke at a water pressure of 46 kof/cd.

(2) The fracture position was at section E, and the fracture occurred uniformly in a range of 9500 mm in the circumferential direction.

Based on the results of this test, it is effective to apply pressure in two stages, and in the case of Test Example 1, where the fracture occurred uniformly over a wide range in the circumferential direction, and the fracture occurred locally due to stress concentration. It is understood that the pressure-resistant rubber bag breaks at high pressure compared to the above.

12 FIG. 17 shows the main parts of a pressure-resistant rubber bag 30 according to another embodiment. The material of the pressure-resistant rubber bag 30 is the same as the pressure-resistant rubber bag 12 mentioned above.
Similar to , those with a large elongation rate (e.g. 600-900%)
is preferable, and the wall thickness (film thickness) is suitably 5 m or more. Further, when the inside of the pressure-resistant rubber bag 30 is filled with gas to such an extent that the membrane wall does not stretch, the shape (true shape) is close to a perfect sphere (H/D←1).

A cylindrical cap 31 is attached to the top wall of the pressure-resistant rubber bag 30, and by connecting a composite pipe 32 to the cap 31, liquid is supplied to the inner chamber of the pressure-resistant rubber bag 30 through the composite pipe 32. Liquid can be discharged from the inner chamber of the pressure-resistant rubber bag 30. The composite tube 32 includes an inner tube 33 for liquid injection and a base 3.
It consists of an outer tube 34 which is threadedly connected to 1.

The inner tube 33 passes through the upper end wall 35 of the outer tube 34 in an air-water tight manner and extends to the inner surface of one wall of the pressure-resistant rubber bag 30, and an extension rubber tube 36 is attached to its lower end. This rubber tube 3
6 is not necessarily necessary, and the inner tube 33 may be made longer than the inner surface of the membrane wall. In short, pressure-resistant rubber bag 30
It is only necessary to prevent the liquid immediately after being injected into the bag 30 from mixing with the liquid being discharged, so that water and mortar can be successfully replaced by injecting mortar into a container in which water has been previously injected into the pressure-resistant rubber bag 30. Can be done.

Fig. 18 shows a state in which a pile frame concrete 37 is cast into an excavated hole 2 in the ground 1 using a pressure-resistant rubber bag 30 and a composite pipe 32 connected to the pressure-resistant rubber bag 30, and the pressure-resistant rubber bag 30 is inflated. There is. Water is first filled under pressure into the pressure-resistant rubber bag 30 through the inner tube 33, and then mortar is injected to replace the water. The replaced water is discharged to the outside through the space between the outer tube 34 and the inner tube 33.

As is clear from the above explanation, it is a bag that is used to compress the ground at the end of the pile when constructing foundation piles, and expands into an almost spherical shape when fluid is injected inside. A pressure-resistant rubber bag for pre-compressing the soil at the tip of a pile has been proposed, which is equipped with a cap on the top wall that can simultaneously supply fluid to the pile and discharge fluid from the inside.

This pressure-resistant rubber bag is suitable for use in soil bearing capacity reinforcement construction methods, and the pressure-resistant rubber bag is placed between the bottom of an excavated hole for pile construction and the tip of the foundation pile to be created, and the liquid filler is pressurized. By injecting and inflating the pressure-resistant rubber bag and hardening the filler, the ground at the pile tip can be compressed and the ground bearing capacity can be increased. This construction method prevents the foundation piles from sinking after construction, making it possible to shorten the length of the piles compared to conventional methods, and adopting the expanded pile method (a construction method in which the bottom of the excavation hole is widened). There is no need to do this, and together with the simplification of construction, it is possible to reduce construction costs.

[Brief explanation of the drawing]

Fig. 1 and Fig. 2 are diagrams showing the construction mode of the soil bearing capacity reinforcement construction method implemented using the pressure-resistant rubber bag of the present invention, respectively, and Fig. 3 is a diagram showing the outside of the pressure-resistant rubber bag according to an embodiment of the present invention. Diameter (0)
A graph showing the difference in pressure resistance performance due to the ratio (IIlo) of the pressure-resistant rubber bag and the length (11).
Graph showing the difference in pressure resistance performance depending on the ratio (H/D), 5th
12 to 12 are diagrams showing the manufacturing process of the pressure-resistant rubber bag of the present invention, and FIGS. 13 and 14 are a partially cutaway side view (in a contracted state) of the pressure-resistant rubber bag used in the pressure test, respectively. 15
The figure shows the pressure-resistant rubber bag buried in sand for testing, Figure 16 is an estimated view of the pressure-resistant rubber bag inflated by injecting pressurized water, and Figure 17 is another diagram. FIG. 18 is a cross-sectional view showing the main parts of the pressure-resistant rubber bag according to the embodiment and a composite pipe (supply and discharge pipe) connected thereto, and FIG. 18 is a cross-sectional view showing the manner in which the bag is used. 1...Ground, 2...Drilling hole, 3...Reinforcement set, 4...
...Pressure-resistant rubber bag, 5...Injection pipe, 6...Output pipe, 7
...Pressure gauge, 8...Pile frame concrete, 9...
Pile frame, 10... hollow part, 11... concrete,
12...Pressure-resistant rubber bag, 13.14...Cap, 15.
... Mold, 16... Raw rubber board, 17... Addressing board, 18... Release paper, 19... Mold, 20...
Vulcanized rubber molded product, 21...opening, 22...opening, 2
3... Cylindrical container, 24... Sand, 25... Tin plate, 26... Injection pipe, 27... Outlet pipe, 28... Pressure gauge 1.29... Pressing body, 30 ...Pressure rubber bag, 3
1... Cap, 32... Composite pipe, 33... Inner pipe, 3
4... Outer tube, 35... End wall, 3G... Rubber tube, 3
7... Pile frame concrete.

Claims (1)

[Claims] This bag is used to compress the ground at the end of a pile when constructing foundation piles, and expands into an approximately spherical shape when fluid is injected into the interior, and simultaneously supplies fluid to the interior and discharges fluid from the interior. A pressure-resistant rubber bag for pre-compressing the ground at the tip of a pile, which is equipped with a cap on the top wall that can be used to pre-compact the ground at the end of a pile.