JP2884268B2 - Construction method of cast-in-place concrete pile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a cast-in-place concrete pile which is used as a support pile for a foundation of a building, and more particularly to a construction method for increasing a pile supporting force.

[0002]

2. Description of the Related Art The construction of cast-in-place concrete piles is shown in FIG.
As shown in (1), a hole b for a pile is excavated in the ground a, a reinforcing steel basket (not shown) is inserted and arranged in the hole b for the pile, and concrete c is cast and constructed on the site. . The construction method of the cast-in-place concrete pile is a well-known technique, and is widely practiced as a large foundation pile or a support pile having a diameter of about 1 m to 4 m and a length of about 5 m to 40 m.

[0003]

The method of constructing a cast-in-place concrete pile involves a problem that when the hole b is excavated, the surrounding ground becomes loose, leading to a decrease in the ground strength and a decrease in the bearing capacity of the pile. Is in question. As a method of excavating the ground a, a hole wall stabilizing liquid is used to maintain the stability of the hole wall of the pile hole b, and as shown in FIG. Although the membrane e is formed, there is a problem that the water-impermeable membrane e gradually develops and lowers the peripheral frictional resistance of the pile, which also lowers the bearing capacity of the pile. In addition, concrete c cast through a tremy tube (not shown) into the pile hole b filled with the hole wall stabilizing liquid as described above.
Is generally not subjected to compaction processing, and in fact, as shown in FIG.
On the other hand, concrete c is not sufficiently filled to every corner,
A gap f may be left. And, since the ground which has been loosened by the excavation is not improved, the peripheral frictional resistance is low, which causes a decrease in the bearing capacity of the pile. As described above, in the conventional construction method of the cast-in-place concrete pile, since the quality of the pile body is low and the strength is low, the problem is that the supporting force of the pile is low, which is a problem to be solved.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method of constructing a cast-in-place concrete pile having a large supporting force, in which the adhesion between the wall surface of the hole for the pile and the concrete is increased to increase the peripheral frictional resistance of the pile. It is.

[0005]

As a means for solving the above-mentioned problems, a method for constructing a cast-in-place concrete pile according to the present invention is described below with reference to FIGS. In the construction method of a cast-in-place concrete pile in which a pile hole 2 is excavated, a reinforcing cage is inserted into the pile hole 2 and installed, and a concrete 1 is cast to construct a pile body, the concrete 1 is struck. Before installation, a tube 3 having a length reaching the bottom of the hole is inserted into the substantially central portion of the hole 2 for the pile and installed, and after the concrete 1 has been cast, the concrete 1 is set before the concrete 1 hardens. A method in which compressed air or an inflating material is injected into the tube 3 while the tube 3 is prevented from rising to the upper part, and the tube 3 is pressurized and expanded to apply a compressive force to the concrete 1 to perform compaction. I do.

[0006]

In the state where the poured concrete 1 is not yet solidified, the tube 3 at the center is expanded by pressurization. Therefore, the poured concrete 1 in a state where the swelling to the upper part is prevented is caused by the expansion of the tube 3. As a result, a radially outward compressive force is applied to consolidate. This consolidation effect spreads well throughout the concrete 1 and to every corner.

As a result, dewatering occurs from the poured concrete 1 toward the surrounding ground 4, and the density of the concrete 1 increases, the quality improves, and the strength increases. Hole for pile 2
Even if the water-impermeable membrane 16 developed on the wall surface 2b of
Due to the consolidation effect, the concrete 1 sufficiently reaches every corner of the wall surface 2b of the hole 2 for piles, the degree of adhesion between the ground 4 and the concrete 1 is increased, and the ground loosened by excavation is compacted. The peripheral frictional resistance increases. Therefore, a cast-in-place concrete pile having a large bearing capacity is constructed.

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings. 1A and 1B show construction drawings of a cast-in-place concrete pile according to the present invention. In particular, FIG. 1A shows that after excavating the pile hole 2 in the ground 4 and before placing the concrete 1,
The tube 3 is inserted and installed at a substantially central portion in the hole 2 for the pile,
Thereafter, a state in which the concrete 1 is cast at a predetermined level is shown. FIG. 1B shows that, before the concrete 1 is cast yet, compressed air is supplied to the top of the concrete 1 through a hose 8 as one means for preventing the top of the concrete 1 from rising upward. Then, the tube 3 is pressurized and expanded to apply a radially outward compressive force to the concrete 1 to consolidate the concrete. Therefore, up to this stage, a well-known procedure for constructing a cast-in-place concrete pile, that is, a hole 2 for a pile is excavated in the ground 4 and a reinforcing cage (not shown) is inserted into the hole 2 for the pile. And a step of inserting a tremy pipe (not shown) and placing concrete 1 upward sequentially from the bottom of the pile hole 2 is performed.

The tube 3 for applying a radially outward compressive force to the concrete 1 is formed in a bag shape from a film material having sufficient strength to withstand the pressure expansion, such as a high-strength film material. . A cap 5a that hermetically seals the upper end opening of the casing pipe 5 installed above the pile hole 2 is attached with a lock pin 20.
a into the steel pipe 6 attached to the approximate center of
Are connected (FIG. 2). Thus tube 3
Is positioned substantially at the center of the casing pipe 5 and the pile hole 2 and is inserted and arranged so as to reach the vicinity of the hole bottom 2a. In order to expand the tube 3 under pressure, a hose 7 is connected to the outer end of the steel pipe 6, and this hose 7 is connected to a compressor (or a grout pump or the like) not shown above the ground. The tube 3 is pressurized and expanded by injecting an inflating material of high-pressure air (or high-pressure grout sent from a grout pump) generated by the compressor into the tube 3 through the hose 7 and the steel pipe 6. At this time, the rising of the concrete 1 compressed by the pressure expansion of the tube 3 is prevented by the high-pressure air supplied through the hose 8 pressurizing the concrete top in the casing pipe 5 downward. The hose 8 is connected to an air compressor (not shown) on the ground, whereby compressed air is supplied into the casing pipe 5.

[0010] In order to secure a reaction force required when pressurizing the top of the concrete in the casing pipe 5 with the high-pressure air supplied through the hose 8, the reaction is carried out around the casing pipe 5 on the ground surface around the casing pipe 5. A force base 9 is installed, and is fixed to the ground 4 by a ground anchor 10 with a reaction force (FIG. 1). It is also possible to place a weight such as a steel ingot on the reaction force base 9 to take the reaction force. A power jack 11 is provided on the reaction force base 9 in a horizontal inward direction with the casing pipe 5 as a center. The power jack 11 is driven to grip the outer peripheral surface of the casing pipe 5 so that the power jack 11 is held. The casing pipe 5 and the reaction force base 9 are integrated. At the upper end of the casing pipe 5, as shown in FIG.
The cap 5a is integrally provided by a fastening method such as 0, and the hoses 7 and 8 are connected to the cap 5a. As shown in FIGS. 3A and 3B, an air tube 12 serving as a so-called locking bag is provided on the outer peripheral surface of the lower portion of the casing pipe 5. The air tube 12 is compressed and expanded by compressed air supplied through an air hose 13 by an air compressor (not shown). The air tube 12 is brought into close contact with the casing pipe 5 and the pile hole wall surface 2b by inflating, and the gap 14 between the two is closed (FIG. 3B). Therefore, when the cast concrete 1 is compressed and compacted as described above, the concrete 1
Is prevented from leaking. A tube holding piece 15 is provided on the outer peripheral surface of the lower part of the casing pipe 5 in a vertical arrangement with the air tube 12 interposed therebetween. The tube holding piece 15 prevents the air tube 12 from shifting or falling off when the casing pipe 5 is inserted into the pile hole 2.

The operation of installing the tube 3 in the pile hole 2 is performed by a procedure of fixing the cap 5a to the upper end of the casing pipe 5 with a lock pin 20 or the like. Thus, the tube 3 whose upper end is connected to the steel pipe 6 of the cap 5a is necessarily positioned substantially at the center of the casing pipe 5 and the pile hole 2, and is disposed so as to protrude long near the hole bottom 2a. It is done. Thereafter, the concrete 1 is poured into the pile hole 2 from the bottom of the hole upward through a tremee pipe (not shown) to a required amount and a predetermined level position. Before the concrete 1 thus cast has not yet set, compressed air is first supplied to the top end of the concrete 1 through the hose 8 so that the concrete 1 does not rise to the top (FIG. 2). At this time, the reaction force required is such that the resistance of the casing pipe 5 coming out of the ground 4 and the casing pipe 5
Is provided by the ground anchor 10 or the weight of the reaction force base 9 constrained through the shaft, and the floating of the casing pipe 5 is prevented. Compressed air is also supplied to the air tube 12 to perform pressure expansion, thereby closing the gap 14 between the casing pipe 5 and the pile hole wall surface 2b, and preventing the concrete 1 from leaking from the gap 14. You.

When the tube 3 is pressurized and expanded by injecting compressed air or an inflating material in parallel with or before or after the above procedure, the concrete 1 serving as a pile body is efficiently radially outwardly from the center in the radial direction. A compressive force is applied, and the consolidation of the concrete 1 is performed substantially uniformly and uniformly in the vertical and circumferential directions of the pile. When the concrete 1 is compacted by the compressive force due to the expansion of the tube 3 in this way, as shown by the arrow in FIG. 1B, dehydration occurs from the concrete 1 toward the surrounding ground, and the quality of the concrete 1 improves, Strength increases. At the same time, as illustrated in FIG. 4, even if the water-impermeable membrane 16 developed by the hole wall stabilizing liquid exists on the wall surface 2 b of the pile hole 2, the concrete 1 is condensed by the above-described consolidation effect.
The degree of filling of the concrete 1 is increased, and the concrete 1 sufficiently spreads to every corner of the wall with severe irregularities. In addition, the ground loosened by excavation is compacted, the degree of adhesion between the concrete 1 and the ground is increased, the peripheral frictional resistance of the pile body is increased, and a cast-in-place concrete pile having a large bearing capacity is constructed. After the cast concrete 1 has hardened, the mortar is poured into the tube 3 densely to integrate the tube 3 with the pile.

[0013]

According to the method for constructing a cast-in-place concrete pile according to the present invention, the tube 3 installed at the center of the cast concrete 1 over the entire length in the vertical direction causes the tube 3 to expand radially from the center. Since the consolidation process is performed by compressing outward, the consolidation effect is evenly and sufficiently extended from the upper end to the lower end of the concrete 1 serving as a pile, the quality of the pile concrete 1 is improved, and the strength is increased. Even if the water-impermeable membrane 16 developed on the wall surface 2b of the hole 2 exists, the concrete 1 can easily reach every corner of the wall surface 2b and the ground loosened by excavation can be compacted. Since the degree of adhesion is increased and the peripheral frictional resistance of the pile body is increased, it is possible to construct a cast-in-place concrete pile having a large bearing capacity and high quality and high reliability. Moreover, by pressurizing and expanding the inside of the tube 3, the pile body (concrete 1) can be compacted at a stroke from the upper end to the lower end. The construction time of the pile can be shortened, which contributes to shortening the construction period and improving the economic efficiency especially in the construction of a long and large foundation pile.

[Brief description of the drawings]

1A and 1B are construction diagrams of a cast-in-place concrete pile according to the construction method of the present invention.

FIG. 2 is an enlarged sectional view showing an upper part of a pile concrete and a casing pipe.

FIGS. 3A and 3B are cross-sectional views showing before and after operation of a means for closing a gap between a wall surface of a pile hole and a casing pipe.

FIG. 4 is an enlarged sectional view showing the relationship between the state of the wall surface of the hole for a pile and the filling of concrete.

FIG. 5 is a construction diagram of a conventional general cast-in-place concrete pile.

FIG. 6 is an enlarged sectional view showing the relationship between the state of the wall surface of a hole for a pile and the filling of concrete in a conventional cast-in-place concrete pile.

[Explanation of Signs] 1 Concrete 2 Pile hole 3 Tube 4 Ground

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tomio Tsuchiya 2-5-1 Minamisuna, Koto-ku, Tokyo Inside the Technical Research Institute, Takenaka Corporation (72) Inventor Takeshi Yamada 2-5-1, Minamisuna, Koto-ku, Tokyo No. Takenaka Corporation Technical Research Institute Co., Ltd. (56) References Japanese Utility Model Showa 52-29704 (JP, U) JP-B 38-571 (JP, B1) JP-B 37-14175 (JP, B1) (58) Surveyed field (Int.Cl. ⁶ , DB name) E02D 5/36 E04G 21/06 E04D 5/34

Claims (1)

(57) [Claims] In a method of constructing a cast-in-place concrete pile, a pile hole is excavated in the ground, a reinforcing steel cage is inserted into the excavation hole, and the pile is installed. Before placing, insert and install a tube with a length that reaches the bottom of the hole almost at the center of the hole for the pile,
After the concrete is cast and before the concrete hardens, compressed air or an inflating material is injected into the tube while the slab is prevented from rising to the upper part of the cast concrete, and the tube is compressed and expanded. A method of constructing a cast-in-place concrete pile, comprising compressing concrete by applying compressive force to the concrete.