JP2951049B2 - Consolidation method of medium excavation pile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for solidifying a middle-pitted pile on a pile foundation.

[0002]

[0009] In the borehole pile method, the spiral screw auger inserted into the hollow part of the pile is rotated to excavate and excavate the ground at the tip of the pile, and furthermore, the compressed air is blown out to enhance the excavation effect. Is a method of submerging ready-made piles in the ground. Accordingly, when the pile is settled and the pile or more is discharged, the soil around the pile is disturbed over a wide area (indicated by dotted lines in FIGS. 1 and 2) and loosened. The range in which the ground loosens increases as the pile diameter increases, and it is empirically said that H1 = 1 to 4D (D: pile diameter) in the depth direction from the tip of the pile. In addition, when excavating ground below the groundwater level in sandy ground, there is a possibility that a boring phenomenon in which groundwater spouts may occur, and piles constructed by the mid-digging pile method may not express the expected bearing capacity. There are drawbacks.

[0003] In order to solve the above-mentioned drawbacks, a method has been practiced in which an expanded root compaction bulb made of cement milk is formed at the tip of the pile to express the supporting force of the pile.

[0004] For example, Japanese Patent Laid-Open No. 1-29
As disclosed in Japanese Patent No. 5913, a method for producing an expanded root compaction bulb by high-pressure injection of cement milk is disclosed in
As disclosed in Japanese Patent No. 5121, there is a method of forming a mechanically expanded root compaction bulb using an expansion bit, but each of them also has the following problems.

In other words, in the above-mentioned method, since the bulbs are formed within a range of at most H2 = 2D (D: pile diameter) deeper than the lower end of the pile, the compacted bulbs are formed within the range of the disturbed ground. (FIG. 3). Therefore, even if the rooting bulb is formed, the supporting force is insufficient. In addition, since it is difficult to penetrate the pile into the root compaction bulb, the peripheral frictional force at the tip of the pile is small.

In the above-mentioned method, since the formation diameter of the rooting bulb cannot be larger than the outer diameter of the enlarged excavation bit, the rooting bulb is formed in a range in which the ground is disturbed in both the depth direction and the horizontal direction. And the supporting force is insufficient (FIG. 4).

[0007] In addition, in the conventional method, a boiling phenomenon occurs due to a negative pressure generated when the spiral screw auger is pulled out, cement milk in the root compacted bulb portion is sucked up into the hollow portion of the pile, and the compacted bulb is destroyed (FIG. 5). .

The present invention is a method developed to solve the above-mentioned various problems.

[0009]

According to the method of the present invention, a hollow screw pile is penetrated into a ground by inserting a spiral screw auger into the hollow pile and excavating the ground, and the hollow pile is pierced into the ground. When it reaches, while hardening material such as cement milk is injected at high pressure from the auger bit tip into the ground loosened by middle digging while the hollow pile is fixed, or water is injected at high pressure when excavating from the auger bit tip. Injecting a high-pressure hardened material at the time of raising the auger bit, pre-drilling from the pile tip to a depth of 2 to 4 times the pile diameter to create an expanded root compaction bulb, and then expand the hollow pile to expand Insert one or more times the pile diameter into the bulb, and then pull up while rotating the spiral screw auger in the reverse direction.

Further, the auger is pulled up, and when it reaches a predetermined position, a flash-setting material such as a mixture of cement and water glass is sprayed from the auger bit tip to plug the hollow portion of the pile,
Then raise the auger to the full length.

[0011]

6 to 10 are longitudinal sectional views showing the outline of the construction process of the present invention. The hollow pile 1 is made of a ready-made concrete pile, a steel pipe pile or the like. An auger 2 to be inserted into the hollow pile 1 has a spiral wing 3 around it, and a central rotating shaft 4 has a bit 5 at its tip.
The spiral screw auger 2 is rotated while the hardened material such as high-pressure cement milk is injected and injected into the ground loosened by the middle digging to excavate the ground, and the hollow pile 1 penetrates into the ground. Let it.

When the hollow pile 1 reaches a predetermined depth, the hollow pile 1 is fixed, and a hardened material such as cement milk is injected at a high pressure from the tip of the auger bit 5 while the pile diameter is 2 to 4 mm from the pile tip. An expanded root compaction bulb A is created by preliminarily excavating a double depth H3, and the hollow pile 1 is inserted into the enlarged root compaction bulb A at least one time the pile diameter while it is not hardened (H4). ,
Next, the spiral screw auger 2 is pulled up while rotating in the reverse direction, and when it reaches a predetermined position, for example, an intermediate portion of the hollow pile 1, a flash-hardened material made of a mixture of cement, water glass, and the like is injected and injected from the tip of the auger bit 5 under high pressure. A stopper B is provided in the middle of the hollow portion of the pile, and then the entire length of the spiral screw auger 2 is pulled up.

In the above-mentioned process, when excavating in advance, water may be injected at a high pressure during excavation, and when the spiral screw auger is pulled up, it may be switched to a hardened material to form an expanded root consolidation bulb (FIG. 9). Also, the resistance of the ground acting on the auger bit 5 is comprehensively determined from the current value, the pushing force, the excavation speed, etc., flowing through the auger motor (not shown),
It is economical to confirm that the ground is not disturbed and to determine the depth of the preceding excavation, since the shortest preceding excavation length is sufficient. The injection pressure of the instantaneous hardening material may be large enough to remove the soil attached to the inner surface of the hollow pile and secure the adhesive force between the instantaneous hardening material and the inner surface of the hollow pile.

[0014]

The present invention has the above-mentioned structure, and when the hollow pile reaches a predetermined depth by the inside excavation by the spiral screw auger, the high pressure cement milk or the like is introduced from the tip of the auger bit into the ground loosened by the inside excavation. While injecting hardened material or injecting water at high pressure when drilling from the auger bit tip, and injecting high pressure hardened material when pulling up the auger bit, the pile diameter is 2 to 4 mm from the pile tip.
By excavating twice the depth, expanded compacted bulbs can be created on the undisturbed ground, and hollow piles can be inserted into expanded compacted bulbs at least 1 times the diameter of the pile. Fixing is ensured. In addition, in the case of high-quality support ground such as gravel and sandy gravel, the hollow pile can be directly fixed to the undisturbed support ground as shown in FIG. 11, and a safer support pile can be obtained.

[0015] Furthermore, by bubbling a flash screw auger when the spiral screw auger is pulled up by injecting a flash hardening material such as a mixture of cement and water glass into the hollow pile from the tip of the auger bit and plugging the material, The solidification bulbs of the medium digging pile can be reliably created.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a loosened state of a ground during hollowing of a hollow pile by a conventional construction method.

FIG. 2 is a longitudinal sectional view showing a loosened state of the ground when the hollow pile is fixed by the conventional method.

FIG. 3 is a longitudinal sectional view showing a state in which an enlarged root compaction bulb is formed by high-pressure injection according to a conventional method.

FIG. 4 is a longitudinal sectional view showing a state in which an enlarged root compaction bulb is formed by an enlarged bit according to a conventional method.

FIG. 5 is a longitudinal sectional view showing a state of occurrence of a boiling phenomenon caused by raising a spiral screw auger.

FIG. 6 is a longitudinal sectional view showing a state where the hollow pile according to the present invention is laid down to a predetermined depth.

FIG. 7 is a longitudinal sectional view showing a preceding excavation situation of the present invention.

FIG. 8 is a longitudinal sectional view showing a precedent excavation state up to the undisturbed supporting ground according to the present invention.

FIG. 9 is a longitudinal sectional view showing a state in which an expanded augmented bulb is formed by pulling up the auger bit while injecting hardened material after completion of the preceding excavation of the present invention.

FIG. 10 is a longitudinal sectional view showing a state in which the hollow pile of the present invention is inserted into an expanded root compaction bulb.

FIG. 11 is a longitudinal sectional view showing a situation where the hollow pile according to the present invention is directly fixed on a supporting ground which is not disturbed.

FIG. 12 is a longitudinal sectional view showing a state in which the instantaneously hardening material of the present invention is injected in a hollow pile.

FIG. 13 is a longitudinal sectional view showing a state in which the inside of a hollow pile is plugged with the instantaneously hardening material of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... hollow pile, 2 ... auger, 3 ... spiral blade, 4 ... rotating shaft, 5
... bit A ... bulb, B ... plug

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-295913 (JP, A) JP-A-3-25121 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) E02D 7/00 E02D 5/50

Claims (4)

(57) [Claims] 1. When an auger is inserted into a hollow pile and the hollow pile penetrates into the ground, when a predetermined depth is reached, a high pressure is applied from the tip of the auger bit into the ground loosened by digging while fixing the hollow pile. While injecting the hardened material of the above, an expanded root compaction bulb is formed by pre-digging a depth of 2 to 4 times the pile diameter from the tip of the pile, and then the hollow pile is inserted into the enlarged root compaction bulb with a diameter of 1 mm. A method of digging piles for digging, characterized by inserting more than twice and then lifting the auger while rotating it in the reverse direction. 2. Inserting an auger into a hollow pile to penetrate the hollow pile into the ground, and when reaching a predetermined depth, excavating from the tip of the auger bit into the ground loosened by middle digging while fixing the hollow pile. At times, water is injected at a high pressure, and when the auger bit is lifted, a high-pressure hardened material is sprayed, and from the tip of the pile, a depth of 2 to 4 times the pile diameter is preliminarily excavated to create an expanded root consolidation bulb. A method of consolidating a digging pile, wherein a hollow pile is inserted into the expanded rooting bulb at least one time the diameter of the pile, and then the auger is pulled up while rotating in the reverse direction. 3. The auger is pulled up, and when it reaches a predetermined position, an instantaneous hardening material is injected from the tip of the auger bit to plug the hollow portion of the pile, and thereafter the auger is pulled up to the full length. 3. The method for solidifying a digging pile according to claim 2. 4. The method according to claim 1, wherein the hardening material is cement milk, and the instantaneously hardening material is a mixture of cement and water glass.