JP2000144727A - Construction method of footing pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of efficiently and surely executing stirring and mixing of excavated earth and sand and hardener in construction of a footing pile by pile installation by inner excavation. SOLUTION: A steel pipe pile 1 and an excavation device 2 inserting an excavation rod in the steel pipe pile 1 are provided to the ground surface of a construction positon, While discharging hardener such as cement milk or the like from a discharge port provided to an excavation head 5, the excavation is carried out by the excavation head 5 on the front end of an inner pipe 4. Then, since both outer pipe 3 and inner pipe 4 of the excavation rod having double pipe construction are rotated in the opposite direction, excavated earth and sand and hardener are stirred to mix while rotating also a plurality of excavation wings 3a and 4a provided to the pipes in the opposite direction. Boring is carried out by the excavation device 2, at the same time, the settlement of the steel pipe pile 1 is carried out, and when the steel pipe pile 1 reaches the bearing ground 11 having a specific depth, the outer pipe 3 and inner pipe 4 are respectively rotated in the opposite direction from when the excavation is carried out to close the stirring wings 3a and 4a, and they are pulled out from the inside of the steel pipe pile 1. After the solidification of the hardener stirred and mixed with earth and sand, the construction of the footing pile is completed.

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 buried pile by a middle digging method as a foundation pile.

[0002]

2. Description of the Related Art As a method of constructing a foundation pile by a medium digging method, a rod of a drilling device is penetrated into a hollow portion of a hollow preformed pile, and while excavating the ground by a drilling mechanism at a rod tip portion, cement milk or the like is used. In general, a solidified material is injected, mixed with excavated earth and sand to form a soil cement, a hollow precast pile is sunk to a predetermined depth, and the soil cement is hardened to form a buried pile.

Some excavating mechanisms at the tip of the rod are provided with excavating wings, agitating wings, counter-rotating wings, and the like. In many cases, the pile can be enlarged and reduced in the radial direction by mechanical means such as a mechanism.

[0004] Hollow precast piles include steel pipe piles, hollow concrete piles, steel concrete composite piles, and the like. Steel pipe piles are further provided with steel pipes having external ribs formed with spiral projections on the outer surface of the steel pipes, and steel pipes at the lower end of the steel pipes. In some cases, a projection is formed to enhance the adhesive force at the tip root fixing portion.

[0005] In many cases, an enlarged excavation section is provided for the tip root compaction part and filled with a rich blend of cement milk or mortar to enhance the tip root compaction part.
For example, Japanese Patent Publication No. Hei 7-81270 discloses a method for forming an anchor foundation pile, in which a spiral projection is provided on the outer peripheral surface.
In addition, when using a steel pipe pile with a ring-shaped projection formed on the inner peripheral surface of the lower end and using this for the middle digging method, a drilling device equipped with a drilling wing, stirring blade, co-rotation prevention wing, etc. at the tip of the auger rod A method is described in which the construction is performed while injecting a solidifying material such as cement milk from the tip portion using the above method.

[0006]

The advantage of the medium excavation method is that compared to the first excavation method in which a soil cement column is formed in advance and then a pile is laid, the construction efficiency can be improved because the pile can be buried at the same time as excavation (two steps). Only one process)
Is mentioned.

However, excavation and agitation of earth and sand and solidified material,
Since the piles are buried at the same time as mixing, it is necessary to consider the resistance of the piles from the ground during excavation.
In addition, in the case of the pre-digging method, the excavated earth and sand and the solidified material can be agitated and mixed both when the excavating device excavates the ground and when the excavating device is lifted, whereas the medium excavating method is used. In such a case, stirring and mixing when lifting the excavator cannot be performed.

[0008] Therefore, in order to efficiently perform the foundation pile in the construction of the inside digging method, it is necessary to efficiently and surely perform the stirring and mixing at the tip of the digging rod.
Insufficient stirring and mixing may lead to a decrease in the bearing capacity of the constructed foundation pile.

In the method described in Japanese Patent Publication No. Hei 7-81270, in addition to the excavating blades and the stirring blades, the anti-rotating anti-rotation blades that have the co-rotating anti-rotating blades and the like are provided. In some cases, the effect of agitation is greater than in the case of simply rotating blades (although this is not an inherent effect of the anti-corotating blade).

[0010] However, compared with the method of freely stirring and mixing regardless of the piles to be set later as in the pre-digging method, the mixing and stirring of the earth and sand and the solidified material cannot be said to be sufficient.
Uncertainty remains in the uniformity and strength of the resulting soil cement.

It is an object of the present invention to provide a method of efficiently and reliably mixing and mixing excavated earth and sand with a solidified material in the construction of a foundation pile by such a medium digging method.

[0012]

According to a first aspect of the present invention, there is provided a method for constructing a foundation pile, wherein a rod of an excavator is penetrated into a hollow portion of a hollow preformed pile, and the ground is excavated by a drilling and stirring means at a rod tip. While solidifying material is injected, the hollow precast pile is sunk to a predetermined depth while stirring and mixing the excavated earth and sand with the solidifying material,
When the buried pile is formed by hardening of the solidified material agitated and mixed with the earth and sand, the excavated earth and the solidified material are formed by the rotation of the forward and reverse stirring mechanisms provided in the excavation and stirring means at the tip of the rod and rotating in opposite directions to each other. The hollow precast pile is settled while forcibly mixing.

That is, when a hollow precast pile is constructed by a conventional middle digging method, the digging and stirring means having a reciprocating stirring mechanism is used to forcibly mix the excavated earth and sand with a solidified material such as cement milk. Therefore, it is intended to improve the stirring and mixing effect, to enhance the homogeneity of the mixture, and to construct a highly reliable foundation pile.

The basic part of the inside digging method can be carried out by various conventionally used methods using various conventionally used devices. For example, as the excavating mechanism in the excavating and stirring means at the tip of the rod, an excavating head provided with a number of excavating blades (bits), an excavating blade type equipped with an excavating blade, and an excavating and stirring device also serving as an agitating blade. There are wing type and spiral wing type.

[0015] Further, co-rotation prevention wings, a stabilizer provided at a portion of the rod located in the hollow preformed pile, and the like can be added as necessary. Regarding these drives, usually, a drive device supported by a crane or a leader is attached to the upper end of the rod of the excavator, and while the upper end of the hollow preformed pile is grasped by the chucking device, the rotation of the rod and the rotation of the hollow preformed pile are performed. It is common to perform the simultaneous deposition, but there is no particular limitation.

Further, hollow precast piles may be built without rotating or built while rotating, and in the case of steel pipe piles with external projections provided with spiral ribs on the outer peripheral surface, etc. In many cases, it is built while rotating.

According to a second aspect of the present invention, in the method for constructing a foundation pile according to the first aspect, the forward / reverse stirring mechanism includes a coaxial inner pipe and an outer pipe which are respectively rotated in opposite directions by a driving device;
The present invention is limited to the case where the inner pipe has an outer surface of a portion protruding below the outer pipe and a plurality of stirring blades provided on the outer surface of a lower part of the outer pipe so as to be expandable and contractible.

In this case, when the inner tube and the outer tube are rotated in opposite directions by the driving device, a driving device such as a motor may be separately provided, or the driving force of the driving device may be transmitted via a gear transmission mechanism or the like. A configuration may be adopted in which the rotational force is converted into a rotational force in the opposite direction, and a single drive device may be used.

The structure of the stirring blade itself can be the same as that of the conventional excavator for the middle digging method.
The rotation of the outer pipe drilling blade located above and the inner pipe drilling blade located below rotate in the opposite direction, so that all agitating blades or the agitating blades and the agitating blade rotate in the same direction. The mixing effect is greatly improved.

The outer pipe excavation wing and the inner pipe excavation wing are not limited to one stage, and a plurality of stages may be provided.

[0021]

FIG. 1 shows an example of the structure of the tip of a drilling rig used in an embodiment of the present invention.

The excavating rod of the excavating apparatus 2 has a double-pipe structure having an inner pipe 4 inside the outer pipe 3, and an excavating head having a number of excavating blades (drilling bits) 5 a at the tip of the inner pipe 4. 5 is attached. Also, this drilling head 5
A discharge port 8 for discharging a solidified material such as cement milk is formed in the portion.

In this example, a total of four stirring blades 3a are attached to the outer peripheral surface of the lower end of the outer tube 3 in two stages. Each of the stirring blades 3a is rotatable around the pin 11, and the outer tube 3
When it rotates in the direction of the arrow shown in FIG. 1 (b), it opens in the direction in which the diameter increases due to the resistance of the excavated earth or sand mixed with the solidified material.

The stirring blade 3a shown on the upper side in FIG. 1 (b) is in an open state, and the expanded state is maintained by hitting the stopper 12. Diameter R _1max at this time corresponds to the stirred diameter D _s.

The stirring blade 3a shown on the lower side of FIG. 1B is in a closed state, and the steel pipe pile 1
This state is obtained by rotating the outer pipe 3 in the direction opposite to the arrow in the figure when inserting the steel pipe pile 1 into the inside or when sinking the steel pipe pile 1 to the support ground of a predetermined depth and lifting the excavation rod. . Diameter R _1min at this time is designed to be equal to or less than the internal diameter D _i of the steel pipe pile 1.

Similarly, FIG. 1 (c) shows that the inner pipe 4 also has a stirring blade 4
a are attached in two stages in total, and have a reverse relationship to the stirring blade 3 a of the outer tube 3. Stirred diameter R _2max at which the wing 4a is opened corresponds to the stirring diameter D _s in the borehole 10, the diameter R _2min when closing is set to be less than the inside diameter D _i of the steel pipe pile 1.

In FIG. 1A, reference numeral 14 denotes a misalignment prevention wing attached to the side surface of the outer tube 3 in four directions.
The drill rod is located at the center of the steel pipe pile 1. Also, when the rod is pulled out, the excavation rod is kept at the center of the steel pipe pile 1 due to the presence of the misalignment preventing wings.
Since the contacting portion with the inner surface is limited, the pull-out becomes easy.

FIG. 2 shows a construction procedure according to an embodiment of the present invention. The work is performed according to the following procedure. Installation of steel pipe pile and excavator (see Fig. 2 (a)) The steel pipe pile 1 and excavator 2 are installed on the ground surface at the construction position, and excavation is performed by the excavator 2. The excavation is performed by the excavation blade of the excavation head 5 at the tip of the inner tube 4 while discharging the solidified material such as cement milk from the discharge port 8 in FIG.

At this time, the outer pipe 3 having a double pipe structure
The inner pipe 4 rotates in the opposite direction, and the plurality of excavating blades 3a, 4a provided in each pipe also perform the stirring and mixing of the excavated earth and sand and the solidified material while rotating in the opposite direction.

Excavation by excavator, sinking of steel pipe pile (see FIG. 2 (b)) Rotational force of excavator 2 is transmitted from drive device 6 provided at the upper end, and a chucking device provided at drive device 6 portion. With 7 holding the upper end of the steel pipe pile 1, at the same time as digging,
The steel pipe pile 1 is laid down. As part of the load for laying down the steel pipe pile 1, the excavator 2 including the driving device 6
Can use its own weight.

When the steel pipe pile 1 is laid down to the supporting ground 11 having a predetermined depth, the outer pipe 3 and the inner pipe 4 are rotated in the directions opposite to those of the excavation, respectively. With the stirring blades 3a, 4a closed, pull out from the inside of the steel pipe pile 1.

Completion of Construction (See FIG. 2 (d)) By the hardening of the solidified material mixed with the earth and sand, the construction of the foundation pile in which the steel pipe pile 1 is buried in the soil cement column is completed.

[0033]

According to the present invention, the excavating earth and the solidified material such as cement milk are forcibly mixed by the reciprocating agitating mechanisms rotating in opposite directions, so that all the agitating blades or the excavating blade and the agitating blade are in the same direction. As compared with the case of rotating at a low speed, the effect of stirring and mixing is greatly improved, the homogeneity of the mixture is increased, and a highly reliable foundation pile can be constructed.

Since the construction is basically performed by the middle digging method, compared with the first digging method in which an existing pile is erected later, it has higher workability and can surely carry out the stirring and mixing. Equal or near homogeneity of the mixture is obtained.

[Brief description of the drawings]

FIG. 1 shows an example of a structure of a tip portion of an excavator used in an embodiment of the present invention, where (a) is a side view and (b)
Is a cross-sectional view taken along the line BB, and (c) is a cross-sectional view taken along the line CC.

FIG. 2 is a vertical sectional view showing a construction procedure in one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Steel pipe pile, 2 ... Drilling equipment, 3 ... Outer pipe, 3a ... Stirring blade,
DESCRIPTION OF SYMBOLS 4 ... Inner pipe, 4a ... Stirring blade, 5 ... Drilling head, 5a ... Drilling blade, 6 ... Drive device, 7 ... Chucking device, 8 ... Solidified material discharge port, 9 ... Soil cement, 10 ... Drilling hole, 11 ... Pin, 12: Stopper, 13: Support ground, 14: Off-center prevention wing

Claims (2)

[Claims] 1. A rod of an excavator is penetrated into a hollow portion of a hollow preformed pile, a solidified material is injected while excavating the ground by an excavating and stirring means at a rod tip, and the excavated earth and sand and the solidified material are stirred and mixed. When the hollow prefabricated pile is sunk to a predetermined depth, and the buried pile is formed by hardening of the solidified material mixed and mixed with earth and sand, when the excavation and stirring means at the rod tip is provided, a stirrer for the forward and reverse directions in the opposite direction is provided. A method for constructing a foundation pile, wherein a hollow precast pile is settled while forcibly mixing and mixing excavated soil and solidified material by rotation. 2. The reciprocating stirring mechanism includes a coaxial inner tube and an outer tube which are respectively rotated in opposite directions by a driving device, and an outer surface of a portion of the inner tube protruding below the outer tube and the outer tube. 2. The method according to claim 1, further comprising a plurality of stirring blades provided on the outer surface of the lower part of the pipe so as to be expandable and contractible.