JP2003247233A - Construction method for hollow pipe pile and construction device thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a construction method for a hollow pipe pile and a construction device thereof capable of improving friction force on a peripheral face of the hollow pipe pile by pile installation by inner excavation and improving construction efficiency of enlarged foot protection bulb. <P>SOLUTION: The hollow pipe pile is provided at predetermined depth by pile installation by inner excavation, high pressure injection and low pressure pouring of cement milk are simultaneously performed, an outer part side of the enlarged foot protection bulb is mainly constructed by high pressure injection, and an inner part side of the enlarged foot protection bulb is mainly constructed by low pressure pouring to construct the enlarged foot protection bulb in a tip part of the hollow pipe pile. An auger used in pile installation by inner excavation is provided with a low pressure discharge port opened in the vicinity of a tip of an auger rod and a high pressure injection port in which a tip of a pipe extended outward from the auger rod in the vicinity of the tip of the auger rod is opened. High pressure injection of cement milk is performed through the high pressure injection port, and low pressure pouring of cement milk is performed through the low pressure discharge port. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for constructing hollow pipe piles such as PHC piles and steel pipe piles, and in particular, a method for constructing hollow pipe piles characterized by the construction of enlarged root-consolidating bulbs. And its construction equipment.

[0002]

2. Description of the Related Art Conventionally, a hollow pipe pile embedding method has been to dig a hollow pipe pile to a predetermined depth by a hollow excavation method or a pre-boring method, expand the pile tip ground and inject cement milk. A general method is to build an enlarged root consolidation bulb by using the above method and connect the enlarged root consolidation bulb to the hollow pipe pile. Then, as the method for expanding and excavating, there are a mechanical expanding and excavating method and a method using high-pressure injection (jet).

[0003]

Expansion of hollow pipe piles by the medium excavation method When the root-fixing bulbs are mechanically expanded and excavated, the expansion excavator becomes complicated and construction performance deteriorates due to poor soil discharge. However, if a simple reverse rotation expansion device is used, there is a problem that expanded excavation becomes uncertain.

On the other hand, if the high-pressure jet method is adopted, the excavator is simple, but there is a problem that it takes time to build the root-hardening bulb. High-pressure injection of cement milk is usually 20 N / m from a nozzle with an outer diameter of 2-4 mm.
It is jetted at a pressure exceeding m ² and the discharge amount is about 50 to 300 liters / minute. Therefore, when the outer diameter of the hollow pipe pile becomes large, the root consolidation bulb also inevitably becomes large both in outer diameter and height.Therefore, the high-pressure injection method with a small discharge amount of cement milk per unit time is used for the construction of the root consolidation bulb. It will take time.

In addition, in the method of constructing a hollow pipe pile by the hollow excavation method, since a friction cutter is generally fixed on the peripheral surface of the tip end of the hollow pipe pile, the presence of this friction cutter causes the peripheral portion of the hollow pipe pile to be surrounded. There is a problem that the ground is loose and the peripheral frictional force is small.

Further, when the hollow pipe pile is sunk by the medium excavation method, the earth and sand pass through the hollow portion of the pile from the bottom to the top.
Sediment adheres to the inner wall surface of the hollow pipe pile. Therefore, especially when the hollow pipe pile is formed of a steel pipe, the integration between the hollow pipe pile tip and the enlarged root consolidation bulb is reduced, or the axis between the hollow pipe pile tip and the enlarged root consolidation bulb is reduced. It may interfere with the transmission of directional force.

The present invention solves the above problems and improves the frictional force on the peripheral surface of the hollow pipe pile by the hollow excavation method, and the method for constructing the hollow pipe pile for improving the construction efficiency of the expanded root-fixing bulb and the method thereof. A construction device is provided.

[0008]

In order to solve the above-mentioned problems, a method for constructing a hollow pipe pile according to the present invention is a hollow pipe pile which is submerged to a predetermined depth in a hollow excavation method, and high pressure injection and low pressure injection of cement milk are carried out. By injecting at the same time, by injecting high pressure, mainly the outer side of the expanded root consolidation bulb is created, and by low pressure injection, mainly the inner side of the expanded root consolidation bulb is created to form the expanded root consolidation bulb at the end of the hollow pipe pile. It is characterized by being built in the club.
As a result, the enlarged part (outside) of the root-fixing bulb is built by high-pressure injection with a small discharge rate, and the inner part is built by low-pressure injection with a large discharge rate. You can build hardened bulbs.

In the method for constructing the hollow pipe pile,
High pressure injection is performed by using an auger in which a low pressure discharge port is opened near the tip of the auger rod and a tip end opening of a pipe extending outward from the auger rod near the tip of the auger rod is used as a high pressure injection port. It is injected from an injection port, and the low-pressure injection is performed by injecting from the low-pressure discharge port of the auger. Note that the vicinity of the tip of the auger rod is an expression including a position that is separated from the tip of the screw blade (spiral blade) by about one round.

In the intermediate digging method, the tip of the hollow pipe pile is positioned in the expanded root-fixing bulb. The expanded root-fixing bulb is simultaneously pierced while the expanded root-fixing bulb is being pierced. Although there is a method of penetrating into the root-hardening bulb, any method may be adopted in the method of the present invention.

In the method for constructing a hollow pipe pile according to the present invention, high-pressure injection of cement milk is carried out before the hollow pipe pile reaches a predetermined depth. As a result, the cement milk can be present outside the outer surface of the hollow pipe pile in front of (above) the expanded root-consolidation bulb, whereby the peripheral frictional force of the hollow pipe pile can be recovered and increased.

Further, if the hollow pipe pile is sunk by the medium excavation method, the earth and sand will pass through the hollow portion of the pile from the bottom to the top.
Sediment adheres to the inner wall surface of the hollow pipe pile. Therefore, according to the present invention, when the auger is pulled up after the expansion rooting bulb construction, the cement milk is injected at high pressure toward the inner surface of the tip of the hollow pipe pile.
As a result, the adhered sand is removed (blown away), and the cement milk is filled in the hollow part of the hollow pipe pile tip, which strengthens the integration of the hollow pipe pile tip and the expanded root consolidation bulb, The tip end closing effect is exerted to increase the axial supporting force.

As the hollow pipe pile, a hollow pipe pile in which a flat rope plate as a friction cutter is fixedly provided on the outer surface of the tip portion is used. This reduces the frictional force between the hollow pipe pile and the wall surface of the ground hole, and facilitates the hollow pipe pile to be sunk.

Further, according to the present invention, when the hollow pipe pile is a steel pipe pile, a ring-shaped reinforcing bar or steel material is fixedly provided on the inner surface of the tip. As a result, when cement milk is filled into the tip of the steel pipe pile, the hollow pipe pile and the expanded root consolidation bulb are surely integrated, and the tip closing effect is exerted to improve the tip supporting force. Instead of the ring-shaped reinforcing bar or steel material, at least one stepped node portion may be formed by projecting the side surface of the tip end portion of the steel pipe pile into a ring shape. As a result, the same effect can be obtained, and since the cement milk hardened body is filled inside the node, even if axial compressive force acts on the node, there is also a three-dimensional restraining effect, so sufficient yield strength is obtained. In addition, since the vertically projected area of the tip portion is also increased, the tip endurance is also increased due to the area effect. Further, in the case of a steel pipe pile provided with a node portion formed by projecting the tip side surface portion in a ring shape, when the tip outer diameter of the steel pipe pile is enlarged to be approximately the same as the outer diameter of the node portion, the enlarged tip is formed. Is preferable because it acts to pull in the tip end soil and sand corresponding to the projection area in the vertical direction of the nodes into the steel pipe pile, and the steel pipe pile can be easily sunk.

The hollow pipe pile construction apparatus of the present invention is
A low-pressure discharge port is opened near the tip of the auger rod, and there is an auger in the vicinity of the tip of the auger rod in which the tip opening of the pipe extending outward from the auger rod serves as a high-pressure injection port. According to this construction device, the cement milk can be injected at high pressure to the outside by the high pressure injection port of the auger, and can be injected at the inside of the low pressure discharge port of the auger. Therefore, the enlarged portion (outside) of the root-hardening bulb can be constructed by high-pressure injection with a small discharge amount, and the inner portion can be constructed by low-pressure injection with a large discharge amount. Further, the auger rod of the auger is a double pipe of an outer pipe and an inner pipe, and between the outer pipe and the inner pipe and a passage in the inner pipe serve as a passage for cement milk, and a high pressure injection port is provided in one of the passages, When the low-pressure discharge port is communicated with the passage of, the cement milk can be supplied from both of the passages, and the cement milk can be discharged from the high-pressure injection port and the low-pressure discharge port to construct the expanded root-hardening bulb.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a partially cutaway front view of an auger as a hollow pipe pile construction device showing an embodiment of the present invention. The auger 1 has a screw blade 6 spirally wound around and fixed to the outer periphery of an auger rod 2, and a bit 7 is fixed to the tip of the screw blade 6. Therefore, this auger 1
When rotation and thrust are applied to the ground, the ground is excavated by the bit 7 at the tip of the screw blade 6, and the excavated soil thus excavated is guided by the screw blade 6 and discharged to the ground.

The auger 1 is provided with a high pressure injection port 8 located outside and a low pressure discharge port 9 located inside, near the tip. The low-pressure discharge port 9 located inside is provided so as to open in the auger rod 2, and the auger rod 2 is also provided.
From the above, the pipe 10 goes out to the vicinity of the outer diameter of the screw blade 6 along the lower surface of the screw blade 6, and the high-pressure injection port 8 is the tip opening of the pipe 10.

The auger rod 2 is composed of a double pipe of an outer pipe 3 and an inner pipe 4, and is provided between the outer pipe 3 and the inner pipe 4 and the inner pipe 4.
Inside are passages 5a and 5b for cement milk. The high pressure injection port 8 communicates with one of the passages 5a and 5b, and the low pressure discharge port 9 communicates with the other of the passages 5a and 5b. For example, the high pressure injection port 8 is in communication with the passage 5b, and the low pressure discharge port 9 is in communication with the passage 5a. Then, the cement milk is supplied at a high pressure to the passage 5b of the high-pressure injection port 8, and the cement milk is supplied to the passage 5a of the low-pressure discharge port 9 at a low pressure. Therefore, the cement milk supplied through the passages 5 b and 5 a of the auger rod 2 is discharged from the high pressure injection port 8 and the low pressure discharge port 9.
At this time, the high-pressure injection port 8 and the low-pressure discharge port 9 are
The high-pressure injection port 8 is small and the low-pressure discharge port 9 is large so that the supply pressure is different and the discharge pressure is different as described above, and the discharge amount of cement milk per unit time is also different. From the high-pressure injection port 8, the discharge amount per unit time is small but high-pressure injection is performed, and the discharge amount from the low-pressure discharge port 9 is large, but low-pressure discharge is performed.

The height levels at which the high-pressure jet port 8 and the low-pressure jet port 9 are provided are the same even if they are at the same height position.
The height position may be different. In FIG. 1, both 8,
9 shows the case of substantially the same level, and FIG. 2 shows the case where the high pressure injection port 8 is at a position higher than the low pressure discharge port 9.

Next, a method of constructing a hollow pipe pile using the auger 1 will be described with reference to FIGS. FIG. 2 is a partial sectional explanatory view showing a set state of a hollow pipe pile and an auger,
FIG. 3 is a front view of a half section showing an example of a hollow pipe pile, and FIG. 4 shows a method of constructing the hollow pipe pile 11 using the auger 1 in the order of steps (a) (b) (c) (d). ) (E) (f) is an explanatory view.

First, as shown in FIG. 2, the auger 1 is set in the hollow pipe pile 11 to be sunk in the ground. At this time, the auger 1 and the hollow pipe pile 11 are positioned concentrically, and the tip portion of the auger 1 has a high-pressure jet port 8 and a low-pressure jet port 9
With the hollow pipe pile 11 protruding downward from the tip of the hollow pipe pile 11 and standing vertically on the ground, and the auger 1 and the top portion (upper end) of the hollow pipe pile 11 are constructed machines (which are conventionally known). So omitted).

The hollow pipe pile 11 is not particularly limited, and any conventionally known hollow pipe piles such as PHC piles and steel pipe piles can be adopted. However, when the hollow pipe piles 11 are steel pipe piles. As shown in FIG. 2, when at least one step of the ring reinforcement 12 formed of a reinforcing bar or a flat rope is fixedly provided on the inner peripheral wall surface of the tip of the steel pipe pile 11a, the tip end of the pile and the rooting bulb are surely integrated. It is preferable that the tip end portion of the pile is reliably blocked and the tip end supporting force of the pile is surely expressed. Moreover, when the hollow pipe pile 11 is the steel pipe pile 11a, as shown in FIG.
It is also possible to form the node portion 13 which is formed in at least one step in a ring shape by expanding the tip portion of a from the inner surface to the outside. Also in this case, the same effect as described above can be obtained, which is preferable. In addition, since the cement milk hardened material is filled inside the joint, even if an axial compressive force acts on the joint, it also has a three-dimensional restraining effect, so it has sufficient proof strength. Since the projected area in the vertical direction is also increased, the tip supporting force is increased due to the area effect. When the hollow pipe pile 11 is the steel pipe pile 11a, it is preferable to provide a friction cutter at the tip of the steel pipe pile 11a because the steel pipe pile 11a can be easily sunk. 2 shows a flat steel plate 14 as a friction cutter, and FIG. 3 shows a case where the outer diameter of the tip of the steel pipe pile 11a is enlarged 15 to be substantially the same as the outer diameter of the joint 13. These friction cutters are merely examples, and the friction cutters are not limited to these embodiments, and any conventionally known cutter can be adopted.

Next, the auger 1 and the hollow pipe pile 11 connected to the construction machine are given a rotational force and a thrust to the auger 1 by this construction machine, and a pushing force is applied to the hollow pipe pile 11. give.
At least a pushing force may be applied to the hollow pipe pile 11, but a rotating force may be applied to the hollow pile 11. When the rotational force is applied, the hollow pipe pile 11 is more effectively sunk. In the following, the case where a pushing force is applied to the hollow pipe pile 11 is described, but this also includes the case where a rotation is applied.

When the auger 1 is rotated and thrust, and the auger 1 rotates, the ground is excavated by the bit 7 provided at the tip of the screw blade 6, and the excavated soil is hollowed by the rotating screw blade 6. Since the auger 1 is conveyed in the pile 11 and discharged to the ground, and the auger 1 is also provided with thrust, it digs forward. Due to this, a drilling hole is formed in the ground, and as the auger 1 is dug, the hollow pipe pile 11 also enters the drilling hole together with the auger 1. In this way, the hollow pipe pile 11 is deposited as shown in FIG.

Subsequently, as shown in FIG. 4 (b), when the hollow pipe pile 11 reaches halfway, high-pressure injection of cement milk is carried out from the high-pressure injection port 8 of the auger 1 to lay down the hollow pipe pile 11. To continue. Due to the high-pressure injection from the high-pressure injection port 8 located outside, the cement milk comes to exist outside the hollow pipe pile 11, and as shown in FIG. The cement milk 16 exists between the empty pipe pile 11 and the wall surface of the hole and is deposited, so that the cement milk 16 adheres to the outer peripheral surface of the hollow pipe pile 11. This construction section corresponds to the portion A in FIG. Conventionally, the frictional force of the peripheral surface of the hollow pipe pile that was sunk due to the presence of the friction cutter was small, but the friction cutter 14
Alternatively, despite the presence of 15, the peripheral frictional force of the hollow pipe pile 11 can be recovered and secured. It takes time to settle the piles thereafter, and if there is a risk that the construction efficiency will decrease due to the hardening of the cement milk, or the piles may not be settled, a hardening retarder may be added to the cement milk, or a hardening delaying type Sometimes cement is used.

Next, when the hollow pipe pile 11 reaches a predetermined depth, high-pressure injection and low-pressure injection of cement milk from the high-pressure injection port 8 and the low-pressure discharge port 9 of the auger 1 are simultaneously carried out to expand the root consolidation bulb. 17 is built, and the tip portion of the hollow pipe pile 11 is inserted into the enlarged root-consolidating bulb 17. This rooting bulb-building section corresponds to the portion B in FIG. The penetration speed of the B part is slower than that of the A part. Fig. 4 (c) shows a state in which construction of the expanded root consolidation bulb 17 in which high-pressure injection and low-pressure injection of cement milk have been carried out has started, and Fig. 4 (d) shows a state in which the expanded root consolidation bulb 17 is completed. The figure (e) has shown the state which the front-end | tip part of the hollow pipe pile 11 penetrated in the expanded rooting bulb 17. FIG.

By simultaneously performing high-pressure injection and low-pressure injection of cement milk from the high-pressure injection port 8 and the low-pressure injection port 9, the outside of the expanded root-fixing bulb 17 is injected with high pressure,
The inner side can be built by low-pressure injection, and the expanded root consolidation bulb 17 can be built in a short time. 5 and 6 are enlarged cross-sectional explanatory views showing a state in which high-pressure injection and low-pressure injection of cement milk are carried out at the same time to build up an enlarged root consolidation bulb 17, and FIG. 5 is a high-pressure injection port 8 of the auger 1.
When the low pressure discharge port 9 and the low pressure discharge port 9 are at substantially the same level, FIG. 6 shows the case where the high pressure injection port 8 is located above the low pressure discharge port 9. From FIGS. 5 and 6, it can be well understood that the enlarged root consolidation bulb 17 is constructed by high-pressure injection on the outer side and low-pressure injection on the inner side.

Further, in the method of penetrating the tip of the hollow pipe pile 11 into the built-up expanded rooting bulb 17, the hollow pipe pile 11 is fixed at a predetermined depth. A method of constructing an enlarged root consolidation bulb 17 at the lower end of the tip and then penetrating it, and a method of constructing the enlarged root consolidation bulb 17 and at the same time allowing the tip of the hollow pipe pile 11 to penetrate into the enlarged root consolidation bulb 17. However, any one of the present invention may be adopted. Of course, the present invention also includes a case where the expanded consolidation bulb 17 is built at the tip of the hollow tube pile 11 and the hollow tube pile 11 is not penetrated into the consolidation bulb 17.

Finally, when the tip of the hollow pipe pile 11 has penetrated into the enlarged root-consolidating bulb 17, the hollow pipe pile 11 that has been sunk as shown in FIGS. 4 (e) to (f) is removed. Leave it as it is and pull the auger 1 to the ground. At this time, high-pressure injection of cement milk (the low-pressure injection may be used together) from the start of pulling up, and as shown in FIG. 17a is filled and pulled up. This rooting bulb building section corresponds to the portions C and D in FIG. 9, and corresponds to the portions E and F when the pile is press-fitted after the bulb construction or when the pile is not press-fitted. The portion D in FIG. 9 is E
The pulling speed of the auger 1 can be made faster than that of the part. In the case of the steel pipe pile 11a, the soil adhered to the inner wall surface is washed and the ring streak 12 is provided on the inner wall surface at the tip,
Since the node portion 13 is provided at the tip portion, the pile tip portion and the rooting bulb 17 are surely integrated by filling the cement milk 17a, and the closing effect of the pile tip portion is surely achieved, and the pile 11 The tip supporting force can be surely expressed. Since the earth and sand adhering to the inner wall surface of the hollow pipe pile 11 is removed (blown away or scraped off) by high-pressure injection from the high-pressure injection port 8 when pulling up the auger 1, it is integrated with the cement milk 17a. Becomes stronger. FIG. 7 is a cross-sectional view showing an enlarged portion of the completed enlarged root-consolidating bulb 17, and FIG. 8 shows the hollow pipe pile 11 that has been completed. In FIG. 8, the steel pipe pile 11a shown in FIG. 3 is shown as the hollow pipe pile 11.

Next, the operation of the present invention will be described with reference to the above embodiment. The auger 1 used in the present invention comprises a high pressure injection port 8 located outside and a low pressure discharge port 9 located inside.
Since the cement milk is provided, the high pressure injection from the high pressure injection port 8 is only used, or the high pressure injection and the low pressure injection from the high pressure injection port 8 and the low pressure injection port 9 are simultaneously performed. You can do it. Further, since the high-pressure injection is performed from the high-pressure injection port 8 located on the outer side, the cement milk has a small discharge amount but is strongly injected toward the wall surface of the drilled hole, so that the impact force collapses and expands the hole wall. Thus, the low-pressure injection is performed from the low-pressure discharge port 9 located inside, and since the discharge amount is large, the injected cement milk is around the low-pressure discharge port 9.

Therefore, when high-pressure injection and low-pressure injection of cement milk are carried out at the same time when constructing the expanded root consolidation bulb 17, the outside portion (enlarged portion) of the expanded root consolidation bulb 17 is performed.
Is built by high-pressure injection with a small discharge amount, and the inner part is built by low-pressure injection with a large discharge amount, so that an expanded root consolidation bulb can be built in a short time. Further, conventionally, the frictional cutter fixed to the peripheral surface of the distal end of the hollow pipe pile, the peripheral frictional force of the hollow pipe pile sunk by the hollow excavation method was generally very small. In the invention, by performing high-pressure injection of cement milk before reaching a predetermined depth at which the hollow pipe pile 11 is supported, the cement milk is made to exist outside the hollow pipe pile 11 and adheres to the outer peripheral surface. Therefore, the peripheral frictional force of the hollow pipe pile 11 can be recovered and secured. The high-pressure injection condition of the cement milk at this time may be set so that the discharge pressure and the discharge amount are lower than those at the time of constructing the expanded root consolidation bulb 17.

When the hollow pipe pile is sunk by the medium excavation method, the earth and sand pass through the hollow portion of the pile from the bottom to the top.
Sediment adheres to the inner wall surface of the hollow pipe. Therefore, particularly when the hollow pipe pile is formed of a steel pipe pile, the integration between the hollow pipe pile tip and the expanded root consolidation bulb is reduced, or the hollow pipe pile tip and the expanded root consolidation bulb are combined. It may interfere with the transmission of axial force. In the present invention, the enlarged root consolidation bulb 17
After the construction of No. 1 is completed, in the process of pulling up the auger 1, by injecting cement milk at a high pressure when passing through the tip of the hollow pipe pile 11, soil and sand adhered to the inner peripheral wall surface of the hollow pipe pile 11 is removed. It can be removed, and the integration of the tip portion of the hollow pipe pile 11 and the expanded root consolidation bulb becomes firm, and the axial support force is secured.

The above embodiment does not limit the present invention, and the present invention can be variously modified without departing from the scope of the invention. For example, the auger can be applied not only to the screw auger but also to the auger used in the hollow excavation method.

[0034]

As described in detail above, the method and apparatus for constructing hollow pipe piles according to the present invention have the following effects. (1) When constructing an expanded root-fixing bulb, construct the outer side (enlarged part) by high-pressure injection with a small discharge amount of cement milk, and at the same time build the inner side (central part) by a low-pressure injection with a large discharge amount. As a result, it is possible to significantly reduce the time required to build the expanded compaction bulb and improve the work efficiency.

(2) By performing high-pressure injection and low-pressure injection at the same time, it is possible to construct an expanded root consolidation bulb in which the high-pressure part and the low-pressure part are completely integrated. (3) By inserting the hollow tube pile into the expanded root consolidation bulb, both can be integrated and a large tip supporting force can be exhibited.

(4) By performing high-pressure injection of cement milk before the hollow pipe pile reaches a predetermined depth,
Cement milk can be present outside the outer surface of the hollow pipe pile, and the circumferential frictional force of the hollow pipe pile can be recovered and secured regardless of the presence of the friction cutter.

(5) When the hollow pipe pile is a steel pipe pile, when the auger is rotated and pulled up, high pressure injection of cement milk toward the inner wall surface of the tip of the pile removes the earth and sand adhering to the inner wall surface. It is possible to increase the adhesion between the inner wall surface and the hardened cement milk to ensure the effect of closing the tip part, and to ensure reliable integration with the expanded root-fixing bulb and to secure the tip support force. it can.

(6) When the hollow pipe pile is a steel pipe pile, if at least one stage of a ring-shaped reinforcing bar or flat rope is fixedly provided on the inner wall surface of the tip portion, the hollow portion can be integrated with the hardened cement milk. Improved, the closing effect of the tip portion increases in certainty, and the tip supporting force increases.

(7) When the hollow pipe pile is a steel pipe pile, the hollow pipe pile tip portion is expanded outward from the inner surface to provide at least one stage of a ring-shaped knot portion. Since the hollow portion can be more firmly integrated with the hardened cement milk, the tip closing effect is ensured, and the vertical projected area of the tip portion is increased, so that the tip supporting force is also increased.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view of an auger as a hollow pipe pile construction device showing an embodiment of the present invention.

FIG. 2 is a partial cross-sectional explanatory view showing a set state of a hollow pipe pile and an auger.

FIG. 3 is a front view of a half section showing an example of a hollow pipe pile.

[Fig. 4] Construction method of hollow pipe piles in order of process (a) (b)
It is explanatory drawing shown in (c) (d) (e) (f).

FIG. 5 is an enlarged cross-sectional explanatory view showing a state in which high-pressure injection and low-pressure injection of cement milk are carried out at the same time to construct an expanded root-hardening bulb.

FIG. 6 is an enlarged cross-sectional explanatory view showing another state in which high-pressure injection and low-pressure injection of cement milk are simultaneously carried out to construct an enlarged root consolidation bulb.

FIG. 7 is an enlarged cross-sectional explanatory view showing a completed enlarged root consolidation bulb portion.

FIG. 8 is a front view showing a hollow pipe pile that has been completed in construction.

FIG. 9 is an explanatory diagram showing a construction section for high-pressure injection and low-pressure injection of cement milk.

[Explanation of symbols]

1 auger 2 auger rod 3 outer pipe 4 inner pipe 5a, 5b cement milk passage 6 screw blade 7 bit 8 high pressure injection port 9 low pressure discharge port 10 pipe 11 hollow pipe pile 11a steel pipe pile 12 ring reinforcement 13 ring-shaped node 14 Flat rope plate (friction cutter) 16 Cement milk 17 Enlarged root-fixing bulb 17a Cement milk filled in the hollow part at the tip of the pile

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Isao Aoki             6-13-7 Akasaka, Minato-ku, Tokyo Co., Ltd.             In Tenox F-term (reference) 2D041 AA02 BA13 BA25 CA03 CA05                       CB06 DB02 FA03 FA05 FA07                 2D050 AA04 AA06 CA02 CA05 CB04                       CB42

Claims (9)

[Claims] 1. A hollow pipe pile is sunk to a predetermined depth in the medium excavation method, high-pressure injection and low-pressure injection of cement milk are simultaneously performed, and high-pressure injection is performed mainly on the outer side of the expanded root consolidation bulb, and A method for constructing a hollow pipe pile, characterized in that the inner side of the expanded root consolidation bulb is formed mainly by low-pressure injection and the expanded root consolidation bulb is constructed at the tip of the hollow pipe pile. 2. A high pressure discharge port is formed near the tip of the auger rod, and an auger having a high pressure jet port at the tip opening of a pipe extending outward from the auger rod near the tip of the auger rod is used. The method for constructing a hollow pipe pile according to claim 1, wherein the injection is performed from a high pressure injection port of the auger, and the low pressure injection is performed from a low pressure discharge port of the auger. 3. The method for constructing a hollow pipe pile according to claim 1, wherein the hollow pipe pile is penetrated into the enlarged root consolidation bulb at the same time as or after the construction of the enlarged root consolidation bulb. 4. The cement milk is made to exist outside the outer surface of the hollow pipe pile by performing high-pressure injection of cement milk before the hollow pipe pile reaches a predetermined depth. The method for constructing a hollow pipe pile according to any one of 1 to 3. 5. The cement milk is injected at a high pressure toward the inner surface of the tip of the hollow pipe pile when the auger is pulled up after the expanded root-hardening bulb is constructed, according to any one of claims 1 to 4. Construction method of empty pipe pile. 6. The method for constructing a hollow pipe pile according to claim 1, wherein a flat rope plate as a friction cutter is fixedly provided on the outer surface of the end portion of the hollow pipe pile. . 7. The hollow pipe pile is a steel pipe pile, and a ring-shaped reinforcing bar or steel material is welded to the inner surface of the tip end of the steel pipe pile, according to any one of claims 1 to 6. Construction method of empty pipe pile. 8. A hollow pipe pile construction device for a medium excavation method, wherein a low pressure discharge port is opened near the tip of an auger rod, and a tip of a pipe extending outward from the auger rod near the tip of the auger rod. An apparatus for constructing a hollow pipe pile, characterized in that there is an auger whose opening is a high-pressure injection port. 9. The auger rod of the auger is a double pipe of an outer pipe and an inner pipe, and a cement milk passage is provided between the outer pipe and the inner pipe and in the inner pipe, and a high pressure injection port is provided in one of the passages. The hollow pipe pile construction device according to claim 8, wherein the low-pressure discharge port is communicated with the other passage.