JP2003096769A - Method for embedding ready-made pile with little earth removal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for embedding a ready-made pile capable of reducing a volume of excavated soil to be removed and safely and surely transferring upper load to the ground. SOLUTION: The method for embedding the ready-make pile is so constituted that a hole having a diameter less than an outside diameter of a spiral vane is excavated until the predetermined depth after dry excavation is made in the vicinity of the surface of the earth by a pre-auger method, the neighboring front end of the excavated hole is enlargingly excavated and, at the same time, that the pile having a plurality of spiral vanes around the front end of the pile into the excavated hole is rotationally pressed in after a cement milk is injected to make it in a soil cement state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for burying a composite structure of ready-made piles and soil cement.

[0002]

2. Description of the Related Art Conventionally, in the pre-built embedded pile method of prefabricated piles, a pre-boring expansion root consolidation method has been often carried out in which the pile tip is enlarged and excavated and cement milk is injected into this portion to form an enlarged bulb at the pile tip. Came (Fig. 3). However, since the bearing capacity of the pile tip is smaller than that of the driving method and is insufficient, we have made ST piles with only the pile tip a large diameter and knotted piles with protrusions around the pile tip, A method of increasing the supporting force by adding a surface friction force (FIG. 4), and further, JP-A-60
There has also been devised a method of increasing the pile tip supporting force by providing a spiral wing at the tip of the pile as in -238515.

However, in this method, since the pile outer diameter has a large diameter portion such as a convex portion or a spiral wing, in order to bury the pile by the buried pile construction method, the excavation hole should have a diameter larger than the diameter of the large diameter portion of the pile over the entire length of the pile. Had to drill in. As a result, a large amount of earth and sand is discharged during excavation and burying of piles, and these are industrial wastes, which poses many environmental problems. In the conventional embedding method for piles with large diameter parts that have convex parts and spiral wings, etc., if the large diameter part is enlarged, the excavation holes for sunk the piles also increase, and the amount of excavated soil for that purpose also increases, and also the construction machinery. It had the drawback of becoming large.

[0004]

SUMMARY OF THE INVENTION The present invention is a composite structure of ready-made piles and soil cement which has less excavated soil, improves the reliability of the bottom of the excavation hole, and can transmit the upper load safely and reliably to the ground. The purpose is to provide the buried construction method.

[0005]

The present inventor has made the upper pre-auger hole diameter smaller than the pile outer diameter (that is, the diameter of the spiral blade), and has been skillful in the rotation sinking function of the spiral blade and the integrated function for expressing the supporting force. The present invention has been reached, focusing on the utilization of That is, the present invention is as follows. (1) At the surface, excavate with an auger, then drill a hole with a diameter less than or equal to the outer diameter of the spiral blade of a ready-made pile to a predetermined depth using water or cement milk. After injecting cement milk to make the vicinity of the soil cement-like, a ready-made pile with small soil discharge characterized by rotatingly press-fitting and embedding a ready-made pile having a spiral blade at the pile tip in the excavation hole Buried method.

(2) With an auger, a hole having a diameter equal to or smaller than the outer diameter of the spiral blade of the ready-made pile is dug to a predetermined depth, and then the vicinity of the tip is enlarged and at the same time cement milk is injected to make a soil cement shape near the tip. After that, the method for burying a ready-made pile with a small amount of soil discharge is characterized in that the ready-made pile having a spiral blade at the tip of the pile is rotatively press-fitted and buried in the excavation hole.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. 1 and 2 show the outline of the embodiment. Reference numeral 1 shown in the drawing is a pile main body, and 3 is a spiral blade fixed to the pile main body and having about one rotation. Reference numeral 2 is an upper pre-auger hole having a diameter equal to or smaller than the outer diameter of the spiral blade, and 5 is a lower pre-auger hole larger than the diameter of the spiral blade. In addition, 6 is a hollow portion of the ground surface.

Soil cement is filled in the lower pre-auger hole and is integrated with the pile to form a composite structure. The bottom of the excavator used for constructing this structure is an auger bit, and the top is a rod having no bending and high rigidity. The auger bit at the tip may have any shape as long as it has an enlarged digging blade, even if the enlarged digging blade is hydraulically opened and closed mechanically, or it is opened and closed by resistance to the surrounding soil by reverse rotation. A system may be used. It is preferable that the tip of the bit has a nozzle and has a structure capable of discharging the drilling liquid and the cement milk.

By using such an excavating device, an upper pre-auger hole having a diameter equal to or smaller than the outer diameter of the spiral blade is provided up to a predetermined depth. Before starting the excavation of the upper pre-auger hole, empty digging will be performed near the surface without discharging water or cement milk. The longer the length of hollow digging is, the less soil and sand is discharged, which is more effective. In the upper pre-auger section, as shown in Fig. 1, except for the blank digging section, it may be possible to dig while injecting water or cement milk depending on the ground condition, or if the ground is soft, continue digging as shown in Fig. 2. You may. Subsequent to the excavation of the upper pre-auger hole, the expansion drilling blade is expanded to excavate the tip bottom expanding part, and cement milk is injected into the tip bottom expanding part through a nozzle or the like at the bit tip. After pulling out the excavator, the ready-made pile having a plurality of spiral blades on the outer peripheral surface of the pile tip in the drill hole is lowered by rotation to fix the lower end of the ready-made pile to the bottom of the drill hole.

The diameter of the upper pre-auger hole may be selected according to the hardness of the ground. If multiple independent spiral blades are provided at the tip of the pile, the pile can be rotationally sunk by the spiral blade even if the drill hole is smaller than the outer diameter of the spiral blade. The length of the enlarged excavation hole may be selected according to the type of ground and the required bearing capacity. About 3 times the spiral blade diameter is enough, but 5 times or more is sufficient. The diameter of the enlarged excavation hole may be about the diameter of the blade, but it may be slightly smaller than the diameter of the blade when the ground is hard.

Further, when the ground is soft and large expansion excavation is possible, it is desirable to make it larger than the blade diameter. In order to sufficiently transmit the load from the blade to the expanded bulb, it is sufficient that the expanded bulb diameter is about 1.1 to 1.5 times the blade diameter. The piles to be used can be steel pipe piles, ready-made concrete piles, steel pipe concrete piles, H-shaped steel piles and the like. In the case of ready-made concrete, it is necessary to take measures to attach the spiral blade to the outer peripheral surface of the pile. A plurality of short steel pipes may be installed in the formwork in advance during the production of concrete piles, and after the concrete is hardened, the spiral blade may be fixed to the steel pipe portion by welding.

The plurality of spiral blades attached to the tip of the pile are
It is preferable that each spiral blade has almost one rotation. It is preferable that the spiral blades are installed at substantially equal intervals. The diameter of the spiral blade is preferably about 1.5 to 3 times the outer diameter of the pile. It is preferably 1.5 times or more from the viewpoint of the effect of dispersing the load, and is preferably 3 times or less from the viewpoint of not unduly increasing the blade sharing force. It is effective to install the blades at intervals of about 2 to 10 times the pile diameter, depending on the outer diameter of the pile.

[0013]

Embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 5, the excavation diameter D ₁ = 380 mm is excavated to a depth of 18 m from the ground, and then the bottom excavation diameter D 0 =
At 1000 mm, L = 6.5 m was excavated, and the total length was L.
A drilling hole of 0 = 23.5 m was provided. Cement milk with a water-cement ratio of 60% was injected into the drilled hole in the bottom part, and the outer diameter of the main body in which five spiral blades were joined to the outer periphery of the pile at a pitch of 1500 mm in the range of the tip LB of the pile = about 6 m. D = 40
A concrete pile with a 0 mm outer shell steel pipe was buried. The average N value in the standard penetration test near the tip of the pile was about 30.

[0014]

[Comparative Example] As shown in FIG. 6, a drilling diameter D ₁ = 450 mm and a total length L o = 23.5 m from the ground, which is a conventional method, are provided in the same site as in the embodiment, and then the tip is D 0 = 6.
50, LB = 2.0 m expanded drilling hole was created, cement milk with a water cement ratio of 60% was injected into this expanded drilling hole, and a ready-made concrete pile with the same outer diameter (D = 400 mm) as in the example. Buried.

After the cement milk was hardened, the ready-made piles buried in Examples and Comparative Examples were retested. The maximum load was 4100 kN in the example, whereas it was at most 1300 kN in the comparative example.

[0016]

EFFECTS OF THE INVENTION In the conventional pre-boring tip widening consolidation method using ready-made piles, a lot of water and cement milk were used because it was necessary to carefully excavate the piles in order to submerge them to a predetermined depth. Therefore, the excavated soil discharged to the ground was extremely large and became a work waste, which was a problem. In the present invention, since a plurality of spiral blades are provided at the tip of the pile, a large excavation hole is not required, and even if the amount of water and cement milk is reduced, the pile can be buried to a predetermined depth by rotationally burying it by the thrust of the spiral blade. For this reason, it is possible to perform hollow digging without using water or cement milk near the surface, and the empty digging section serves as a cover for the drilling hole, so that the earth and sand are discharged to the surface not only during pre-auger digging but also during pile burial. Has the effect of being suppressed.

Further, in the construction of the knotted pile, it was necessary to excavate the ground with a diameter equal to or larger than the knot diameter over the entire length of the pile in order to sink the pile to a predetermined depth. Therefore, it is uneconomical to make the joints much larger than the outer diameter of the pile body, and it is not possible to make them larger.
Therefore, there is a problem that even if an enlarged bulb is formed at the tip of the pile, there is a large difference between the enlarged diameter and the node diameter, and sufficient bearing force cannot be transmitted. In the present invention, even if a spiral blade larger than the outer diameter of the pile main body is attached, the excavation hole may be smaller than the spiral blade diameter, and if the spiral blade is made large, the enlarged excavation hole and the pile can be sufficiently integrated. The load transmission of is good.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram illustrating one embodiment of the present invention.

FIG. 2 is a schematic explanatory view showing another aspect of the present invention.

FIG. 3 is a schematic explanatory diagram showing an example of a conventional method.

FIG. 4 is a schematic explanatory view showing an example of a conventional construction method in which a knotted pile is used at the tip of the pile.

FIG. 5 is an explanatory diagram showing an example of the present invention.

FIG. 6 is an explanatory diagram showing a comparative example.

[Explanation of symbols]

1 Pile Main Body 2 Upper Pre-Auger Hole 3 Helical Wing 4 Soil Cement Hardened Body 5 Lower Pre-Auger Hole 6 Empty Dug D D Ready-made Pile D0 Expanded Bottom Excavation Diameter D ₁ Excavated Diameter L Expanded Excavation Length LB Pre-existing Pile Tip L0 Excavation Hole Total Length

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[Procedure amendment]

[Submission date] September 20, 2001 (2001.9.2)
0)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

[0014]

[Comparative Example] As shown in FIG. 6 in the same site as in Example, after having a borehole of the full-length L0 = 23.5m from the ground by drilling diameter D ₁ = 450 mm, which is a conventional method, the tip D0 = 650 mm , LB = 2.0 m enlarged drilling hole was created, and cement milk having a water-cement ratio of 60% was injected into this enlarged drilling hole, and the same outer diameter (D = 400 mm) as in the example.
The prefabricated concrete pile was buried.

Claims (2)

[Claims] 1. The surface of the ground is dug by an auger,
Next, drill a hole with a diameter less than or equal to the spiral blade outer diameter of the prefabricated pile to a predetermined depth using water or cement milk, and expand the vicinity of the tip and inject cement milk to make the soil cement near the tip. After that, a method for burying a ready-made pile with little soil discharge is characterized in that the ready-made pile having a spiral blade at the tip of the pile is rotationally press-fitted and buried in the excavation hole. 2. A hole is drilled by an auger to a predetermined depth up to the outer diameter of the spiral blade of the ready-made pile, and then the vicinity of the tip is expanded and cement milk is injected to make the vicinity of the soil cement-like. After that, the method for burying a ready-made pile with a small amount of soil discharge is characterized in that the ready-made pile having a spiral wing at the tip of the pile is rotatively press-fitted and buried in the excavated hole.