JPS6319394Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a structure at the tip of a pile used in the medium excavation method.

In recent years, this method has been widely adopted as a noise-free and vibration-free construction method, but no improvements have been made to the void created between the ground and the pile due to the friction cutter attached to the tip of the pile. Therefore, the effect of the friction force on the pile circumferential surface could hardly be expected.
I had no choice but to rely solely on the supporting force at the tip. For this reason, the design of pile foundations for structures has become uneconomical. Recently, various attempts have been made to improve the performance of piles for hollow excavation methods by increasing the friction force on the circumferential surface of the piles. for example,
A method has been devised in which an injection conduit and a tip ring are attached along the outer circumference of the pile and the injection fluid is spouted out. However, the method of installing the injection conduit and tip ring along the outer circumference of the pile poses the biggest problem, such as damage during transportation if the injection tube and tip ring are installed at the factory, and if installed at the construction site. , there is a problem of inadequate quality control. Furthermore, if the pile is deposited while injecting fluid at the same time as the pile is being excavated, there are problems such as the fluid getting around to the tip of the pile and adhering to the screw auger head, making it impossible to excavate the pile.

The present invention provides a pile tip structure that solves these problems.

That is, in the present invention, the annular body exists outside the fluid injection port provided on the circumferential side of the pile tip, and the part of the annular body toward the pile tip is connected to the injection ring or friction cutter at the pile tip. The pile tip structure is attached to the pile and the fluid injection port is located inside the toroidal body.

The present invention as described above is designed to connect the outlet of the fluid to be injected, that is, the fluid injection port, to the pile in order to facilitate the burying of piles in the medium excavation method or to adjust the friction force on the pile circumferential surface after burying the piles. The pile is provided on the circumferential side of the tip, and in order to prevent the injected fluid from going around the pile tip, the toric body is opened in the opposite direction to the pile tip, that is, the toric body is opened upward. It is attached to the tip, and has a structure in which the fluid injection port is wrapped inside the annular body.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows one embodiment of the present invention, and FIG.
is a vertical sectional view, FIG. 1B is a cutaway perspective view of the tip portion thereof, FIG. 1C is an enlarged sectional view of the portion in FIG. 1A,
FIG. 2 shows a sectional view of the pile shown in FIG. 1A in a used state. In this embodiment, the injection conduit 8 is fixed to the pile reinforcement before forming and embedded in the concrete part 1 inside the pile, and the injection ring 2 is fixed to the skirt fitting 5 and the friction cutter 6 by welding. . The fluid injection port 7 provided in the injection ring 2 is an open hole, which is sealed (for example, welded) during pile formation and is opened after formation, so there is no risk of concrete paste flowing into it during pile formation. After forming the pile body, the annular body 3 is fixed to the injection ring 2 or friction cutter 6 with screws or adhesive so that the fluid injection port 7 is located on the inside, and the annular body 3 is opposite to the direction of the tip of the pile. It is fixed so that it opens upward in the direction.

The material of the annular body 3 used is flexible rubber, cloth, or paper, which is made into an annular shape with a width H of 15 to 20 cm as shown in Fig. 1C and Fig. used.

When this type of pile is used, as shown in FIG. This prevents the fluid 10 from going around the tip.

Further, FIGS. 3 and 4 show other embodiments of the present invention, with FIG. 3 being a longitudinal sectional view and FIG. 4 being an enlarged sectional view of the portion shown in FIG. 3. In this embodiment, the injection ring 2 is fixed to the skirt fitting 5 by welding 4, and the injection pipe 8 is fixed and molded to the pile reinforcement. Further, the annular body 3 is attached to the friction cutter 6 with screws or adhesive, as in the case of FIG. 1. In the tip structure, the method of fixing the injection ring 2 and the injection conduit 8 is a problem, but generally a skirt fitting 5 is attached to the pile to protect the end plate. The injection ring 2 can be fixed by welding to the skirt fitting 5, and the injection conduit 8 can be tied to the pile reinforcing bars so that it can be formed without moving even when it is centrifugally formed, for example. can. Generally, the injection ring 2 is made of a steel pipe, and its inner diameter is suitably 20 to 30 mm.

As explained above, the tip structure of the present invention can ensure the protection of the injection conduit against external forces, and the toroidal body can be tightly sealed into the excavated hole in the ground by the fluid injection pressure. Since it is firmly attached, it is also possible to prevent fluid from getting around the tip.

Examples and Comparative Examples A 500 mm diameter tube having the tip structure shown in FIG. 1A.
A 15m long centrifugally formed prestressed concrete pile was dug in and sunk while squirting cement milk with a W/C ratio of 70% from the fluid injection nozzle 7, and construction was completed in about 15 minutes without any problems. When the pile was excavated one week after sunk, a strong hardened cement milk body was found to have formed around the pile. The soil type used for construction was a fill layer 3m above the ground surface, a clay layer with a cohesive strength of 0.3kg/ ^cm2 8m below the ground surface, and
The 4m layer is sand with an N value of 20.

For comparison, an injection conduit 8,
Outer diameter 500mm with a structure with injection ring 2 attached,
When a 15 m long centrifugally formed prestressed concrete pile was dug in the middle and cement milk of 70% W/C was injected, the auger screw was empty at a point 8 m from the ground surface. This caused the soil to spin around, making it impossible to remove the soil. When the auger screw was pulled out and observed, cement milk was found to be attached to a portion approximately 3 m from the tip of the auger screw. In addition, it was necessary to pay close attention to the wires when hanging the piles, and when the piles were being set in the cap, the piles hit the main body of the pile driver, damaging a part of the injection conduit and forcing the injection conduit to be re-installed. I had to install it. Note that the stratum in which the test was carried out has the same soil quality as in the example.

[Brief explanation of the drawing]

Fig. 1 shows one embodiment of the present invention, Fig. 1A is a vertical cross-sectional view of the pile, Fig. 1B is a partially cutaway perspective view of the tip of Fig. 1A, and Fig. 1C is the Fig. 1 An enlarged cross-sectional view of part A, FIG. 2 is a vertical cross-sectional view of the tip of the pile in a state in which the pile shown in FIG. 1 A is driven into the ground, and FIG. Front view, Figure 4 is the 3rd
FIG. 5 is an enlarged cross-sectional view of the part shown in the figure, and FIG. 5 is a vertical cross-sectional view of the tip of a conventional pile. 1... Concrete part inside the pile, 2... Injection ring, 3... Annular body, 4... Welding part, 5... Skirt fitting, 6... Friction cutter, 7...
Fluid injection port, 8... Injection conduit, 9... Ground, 10
... Injection fluid, 11 ... Auger screw.

Claims (1)

[Claims for Utility Model Registration] (1) A friction cutter 6 is present at the leading edge of the pile, and an injection ring 2 having a fluid injection port 7 is located at the upper part of the friction cutter 6 on the outer circumference side of the pile. In the provided pile tip structure, the toric body 3 is attached to the injection ring 2 or the friction cutter 6 at the portion toward the tip of the pile, and the fluid injection port 7 is located inside the outer toric body 3. The peg tip structure is characterized by: (2) The stake tip structure according to claim 1, wherein the annular body 3 is made of a flexible material such as a rubber plate, cloth, or paper.