JPS6140816B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for constructing a buried pile.

[Prior art]

The hammer construction method, which is the conventional construction method for prefabricated piles, is rarely used in urban areas in recent years due to the large amount of vibration and noise generated during construction and stricter regulations. The cement milk method has been developed and put into practical use as a typical non-polluting construction method. However, with this method, there are cases where the hole wall collapses and the hole is penetrated by impact. On the other hand, the supporting capacity is greatly affected by the quality of the cement milk injection work, and once the friction is broken, the sinking tends to increase.

Two methods are known for the medium excavation method: inserting piles close to the support layer and hitting them with a Monken or diesel hammer to generate bearing strength, and pumping cement milk to stir the earth and sand at the tip and harden the roots. . The former generates vibrations and noise, albeit temporarily, while the latter only allows stirring within the inner diameter of the stake, and the area directly below the thick part where the load is originally transmitted is not solidified. Recently, a method of using an auger with an enlarged tip has been considered, but at present it is not possible to use an auger that is mechanically large.

The method of embedding ready-made piles in the pit is an excellent method for preventing pollution with extremely low vibration and noise, and is also characterized by the fact that it has a large root hardening effect by enlarging the tips of the piles, so it can be expected to have a large allowable bearing capacity. For this reason, there is an opportunity for it to become popular and developed as one of the basic construction methods in the future.

However, when using existing earth augers used for medium excavation, soil adheres to the blade surface when excavating clay soil. As a result, excavation efficiency and vertical accuracy are poor, and in some cases, internal pressure can cause cracks in the body. Further, along with such a decrease in excavability, there is a drawback that the solidified body constructed by cement injection becomes inhomogeneous and anisotropic. As a result of these shortcomings, the long-term permissible bearing capacity of the pile may not be as high as expected.

Furthermore, in order to inject the cement milk used for root consolidation, a method is used in which the cement milk itself is injected under high pressure. This method has the disadvantage that if groundwater is present and the depth of foot protection work is deep, the hydrostatic pressure will become considerably high and the effective injection range of cement milk will be narrowed.

[Purpose of the invention]

Accordingly, an object of the present invention is to provide a method for constructing a buried pile in a hollow trench, which does not generate noise and can provide sufficiently strong foot protection.

[Structure and effects of the invention]

According to the method of constructing a hollow buried pile according to the present invention, an earth auger equipped with a hollow blade with a small hole formed on the blade surface is inserted into the hollow part of an open type ready-made pile, and fluid is injected from the small hole on the blade surface. While excavating by rotating the earth auger, press-fit the pile to the planned depth. When the pile reaches the planned depth, pull out the earth auger, then insert the injection rod into the hollow part of the pile, until the tip of the rod reaches the pile. When the tip of the rod is reached, the rod is rotated to perform preliminary excavation for root hardening, and when the rod reaches a predetermined depth, the injection liquid is injected from the rod's injection liquid injection nozzle, and the rod is rotated to inject the root hardening. The rod is screwed into the hollow part, and then the rod is pulled out.

Therefore, since the hollow part of the earth auger is excavated, no noise is generated. Then, a rod for injection into the hollow part of the pile is inserted, the lower part of the pile is preliminary excavated, and the injection liquid is injected into the lower part of the pile to harden the lower part of the pile. Therefore, strong root compaction can be achieved without soil collapse.

[Preferred embodiment]

In carrying out the present invention, the injection rod is made of a double pipe, and the injection liquid is injected from the injection liquid injection nozzle of the injection rod, and air is injected from the air injection nozzle of the injection rod so as to surround the injection liquid. is preferred. In this way, the flight distance of the injection liquid can be increased, and a large root hardening can be formed.

Further, when carrying out the present invention, the injection rod is made of a triple pipe, and the injection liquid is injected from the injection liquid injection nozzle of the injection rod, and high pressure water is injected from the high pressure water injection nozzle of the injection rod, and the high pressure water is surrounded. Preferably, air is injected from the air injection nozzle of the injection rod. In this way, the injection liquid flows into the ground that has been cut with high-pressure water, making it possible to form even larger foot protection.

〔Example〕

An embodiment of the construction method of the present invention will be described in detail below with reference to the drawings.

First, an apparatus for carrying out the construction method of the present invention will be explained. Fig. 1 shows the screw part of the earth auger used in the medium excavation process in the construction method of the present invention, in which the rod 11 is a hollow rod, and the blade 12 for discharging the excavated soil upward is similar to the conventional earth auger. It is equipped with... The blade 12 is a hollow blade, and a large number of small holes (injection holes) 13 for injecting fluid are formed on the blade surface. A digging blade is provided at the tip, similar to a conventional earth auger. The details will be described later, but when excavating the ground, a fluid such as air jet, foaming agent, water, or oil is injected from the injection holes 13 on the blade surface, and an air film, oil film, or water is created between the excavated soil and the blade surface. Forms a film to prevent excavated soil from adhering to the blade surface.

Fig. 2 and Fig. 2 show the injection rod used in the injection process in the construction method of the present invention, and the rod 14A in Fig. 2 is a single pipe, and has a digging blade 15 at the tip for performing preliminary excavation for foot protection. and is equipped with an injection liquid injection nozzle 16. Rod 1 in Figure 2
4B is a double pipe, and includes an injection liquid injection nozzle 16 and an air injection nozzle 17 surrounding it. The rod 14C in FIG. 2 is a triple tube and includes an injection liquid injection nozzle 16, a high-pressure water injection nozzle 18, and an air injection nozzle 17 surrounding it. Each of these injection rods can be used depending on the construction conditions.

Next, with reference to FIGS. 3A to 3C, the hollow embedding method of the present invention will be explained. A to D indicate the medium excavation process, and H to I indicate the injection process. The piles used in the construction method of the present invention are PC piles. Use open ready-made piles such as RC piles or steel pipe piles.

Mid-excavation process: The earth auger 5 shown in Figure 1 is inserted into the hollow part of the ready-made pit 1, and the earth auger 5 is erected using the crane 2 (Figure 3-A). 3 indicates a motor, and 4 indicates an air swivel.

Connect the motor shaft and the earth auger shaft, and also connect the air delivery pipe from the compressor and the air intake hole to the hollow blade (Figure 3 B). Driving the compressor and injecting air from the small hole provided on the blade surface, rotate the earth auger 5 to excavate (inside the ready-made pile or the ground directly under the pile)
At the same time, the hydraulic device for press-fitting the pile is driven to press-fit the pile 1. If the construction depth cannot be reached with a single pile, install the single pile with the earth auger inserted over the existing pile, connect the auger shaft, and then weld the pile. Thereafter, while digging in the same way, the piles are pressed in to the planned depth (the depth at which bearing capacity can be obtained) (Figure 3 C and D). Next, Earth Auger 5
The medium excavation process is completed by pulling it out (Fig. 3 D).

Injection process Set the injection device 6 and insert the injection rod 8 into the 1
(Fig. 3 E). The injection rod to be inserted is a triple pipe (Fig. 2) that sends high-pressure water, compressed air, and injection liquid (ground hardening agent such as cement milk) as shown in Fig. 2, or used when the hydrostatic pressure is not very high. Three types of injection rods can be used depending on the construction conditions: a single pipe (Fig. 2) for transporting the injection liquid and a double pipe (Fig. 2) for sending the injection liquid and compressed air. 7 shows a triple pipe swivel, and in this construction example, an injection rod made of a triple pipe is used.

If the injection rod does not reach the construction depth, connect the injection rod (see Figure 3). When the tip of the rod reaches the tip of the stake, the rod 8 is rotated and preliminary excavation for root hardening is performed using the digging blade attached to the tip (Fig. 3).

When a predetermined depth is reached, compressed air is injected to surround the injection liquid, high-pressure water, and high-pressure water, and the rod 8 is pulled up while rotating (Fig. 3 H). Complete the injection by reaching the inner cavity of the pile. Then pull out the rod 8 (Fig. 3).

〔Effect of the invention〕

As explained above, according to the construction method of the present invention, the following excellent effects are achieved.

(1) Noise and vibration during construction are extremely low.

(2) Since the fluid jet is injected from the auger blade surface, an air film is formed between the blade surface and the cohesive soil, which prevents the cohesive soil from adhering to the blade surface during excavation, improving excavation efficiency and vertical accuracy. .

(3) Cracks in the pile body due to internal pressure during excavation can be prevented.

(4) The effective injection range remains almost unchanged even when the excavation depth is deep or the hydrostatic pressure is high.

(5) Since there is no disadvantage that the solidified body to be constructed will be inhomogeneous and anisotropic, a large yield strength can be expected.

Furthermore, if an air film jet is injected around the high-pressure water or high-pressure injection liquid as in the preferred embodiment, the effective injection range is widened, and as a result, the permissible supporting force can be increased.

[Brief explanation of the drawing]

1 and 2 show the screw part of the earth auger implemented in the construction method of the present invention, and 1 and 2 are vertical cross-sectional views partially shown in plan view, respectively, and FIG. 1 is a cross-sectional view. 2 and 2 are plan views of injection rods used in the construction method of the present invention, where 1 is a single pipe, 1 is a double pipe,
indicates one using a triple tube. Figure 3 A to L show the construction order of the construction method of the present invention.
C and D indicate the construction order of the medium excavation process, and E, H, G, J and R indicate the construction order of the injection process. 1...Open-type ready-made pipe, 2...Crane, 3...
... Motor, 4 ... Air swivel, 5 ... Earth auger, 6 ... Injection device, 7 ... Triple tube swivel, 8 ... Injection rod, 11 ... Hollow rod, 12 ... Hollow blade, 13 ... Injection Hole, 14A
... single pipe, 14B ... double pipe, 14C ... triple pipe, 15 ... drilling blade, 16 ... injection liquid injection nozzle, 17 ... air injection nozzle, 18 ... high pressure water injection nozzle.

Claims (1)

[Claims] 1. An earth auger equipped with hollow blades with small holes formed on the blade surface is inserted into the hollow part of the open ready-made pile. When the pile reaches the planned depth, pull out the earth auger, then insert the injection rod into the hollow part of the pile, and when the tip of the rod reaches the tip of the pile, rotate the rod to harden the roots. Preliminary excavation is carried out for this purpose, and when the rod reaches a predetermined depth, the injection liquid is injected from the injection liquid injection nozzle of the rod, and while the rod is rotated, the foot protection is sprayed to the hollow part of the pile, and then the rod is pulled out. A construction method for hollow buried piles characterized by: