JPH04371611A - Method of consolidation construction of foundation of hollow pile - Google Patents

Abstract

PURPOSE:To make a foundation consolidation bulb positively, and to prevent a boiling phenomenon at the time of pulling-up by injecting a hardening material from the tip section of an auger bit and preparing the expanded foundation consolidation bulb by applying a consolidated plug to the intermediate section of a pile. CONSTITUTION:An auger inserted into a hollow pile 1 is turned and the ground is excavated, the hollow pile 1 is penetrated down to specified depth and fixed, and the depth of twice or quadruple as large as a pile diameter from the tip of the pile is excavated precedingly while injecting a hardening material such as cement milk at high pressure from the tip section of an auger bit, thus preparing an expanded foundation consolidation bulb A. The hollow pile 1 is inserted into the foundation consolidation bulb A by once or more of the pile diameter during a time when the bulb A is not hardened. The auger is pulled up while being reversely rotated, a flash setting hardening material composed of the mixture of cement and water glass is injected at high pressure from the tip section of the bit when the auger reaches a specified position, a consolidated plug B is applied between a pile hollow section, and overall length of the auger is drawn up.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of hardening the roots of hollow piles in pile foundations.

0002

[Problem to be solved by the invention] The hollow pile construction method rotates a spiral screw auger inserted into the hollow part of the pile to excavate and remove soil from the tip of the pile, and then blows out compressed air to enhance the soil removal effect. This is a construction method in which ready-made piles are sunk into the ground. Therefore, if a volume of earth and sand exceeding the volume of the pile is discharged as the pile is set, the ground around the pile will be disturbed and loosened over a wide area (as shown by dotted lines in Figures 1 and 2). The range in which the ground loosens becomes wider 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 sandy ground below the groundwater level, a boiling phenomenon in which groundwater gushes out may occur, and piles constructed using the hollow pile method have the disadvantage that they do not exhibit the expected bearing capacity. .

[0003] In order to eliminate the above-mentioned drawbacks, a construction method has been implemented in which an enlarged hardening bulb is created at the tip of the pile using cement milk to increase the bearing capacity of the pile.

[0004] The construction methods include (1) a method of creating an expanded hardened bulb by high-pressure injection of cement milk, and (2) a method of creating a mechanically expanded hardened bulb using an expanding bit, but each of these methods has the following problems.

[0005] In other words, in the method (2) above, since the bulbs are created in a range of at most H2 = 2D (D: pile diameter) below the bottom end of the pile, the foot hardening bulbs are created within the range of disturbed ground. (Figure 3). Therefore, even if hardened bulbs are created, the supporting capacity will be insufficient. Furthermore, since it is difficult to penetrate the pile into the hardened bulb, the peripheral surface friction force at the tip of the pile is small.

[0006] In addition, in the method (2) above, since the diameter of the foot hardening bulb cannot be larger than the outer diameter of the enlarged excavation bit, the foot hardening bulb is placed within the area where the ground is disturbed both in the depth direction and horizontally. The support capacity will be insufficient (
Figure 4).

[0007] In other conventional construction methods, a boiling phenomenon occurs due to the negative pressure generated when the spiral screw auger is pulled out, and the cement milk in the foot hardening bulb is sucked up into the hollow part of the pile, destroying the foot hardening bulb (Figure 5).
).

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

[0009]

[Means for Solving the Problems] The root hardening method for hollow piles of the present invention involves inserting a spiral screw auger into the hollow pile to excavate the ground, thereby penetrating the hollow pile into the ground to a predetermined depth. Once the hollow pile is fixed, hardened material is injected at high pressure from the tip of the auger bit, and an expanded root hardening bulb is created by excavating from the tip of the pile to a depth of 2 to 4 times the diameter of the pile. Thereafter, a hollow pile is inserted into the enlarged root compaction bulb at least 1 times the diameter of the pile, and then pulled up while rotating the spiral screw auger in the opposite direction.

0010

Embodiment FIGS. 6 to 10 are longitudinal sections showing an outline of the construction process of the present invention, in which the hollow pile 1 is made of a ready-made concrete pile, a steel pipe pile, or the like. The auger 2 inserted into the hollow pile 1 has spiral blades 3 around it, and a central rotating shaft 4 has a bit 5 at its tip, which can inject/inject high-pressure water and hardening material. Then, the spiral screw auger 2 is rotated to excavate the ground, and the hollow pile 1 is penetrated into the ground.

When the hollow pile 1 reaches a predetermined depth, the hollow pile 1 is fixed, and while a hardening material such as cement milk is injected at high pressure from the tip of the auger bit 5, a depth of 2 to 4 times the diameter of the pile is removed from the tip of the pile. An enlarged root hardening bulb A is created by preliminary excavation to a double depth H3, and while it is not hardened, a hollow pile 1 is inserted into the expanded root hardening bulb A at least one times the diameter of the pile (H4), Next, the spiral screw auger 2 is pulled up while rotating in the opposite direction, and when it reaches a predetermined position, for example, the middle part of the hollow pile 1, an instant hardening material consisting of a mixture of cement and water glass is injected at high pressure from the tip of the auger bit 5. A plug B is placed in the middle of the hollow part of the pile, and then the entire length of the spiral screw auger 2 is pulled up.

[0012] In the above process, when performing advance excavation, water may be injected at high pressure during excavation, and when the spiral screw auger is pulled up, the material may be switched to a hardened material to create an enlarged root hardening bulb (FIG. 9). In addition, the resistance force of the ground acting on the auger bit 5 is comprehensively judged from the current value flowing through the auger motor (not shown), pushing force, digging speed, etc.
If the depth of preliminary excavation is determined after confirming that the ground is undisturbed, the shortest preliminary excavation length is required, which is economical. Further, the injection pressure of the flash-setting hardening material needs to be large enough to remove the earth and sand adhering to the inner surface of the hollow pile and ensuring adhesion between the flash-setting hardening material and the inside surface of the hollow pile.

[0013]

[Effects of the Invention] The present invention has the above-mentioned structure. When a hollow pile is excavated to a predetermined depth by a spiral screw auger, a high-pressure hardened material is injected from the tip of the auger bit, and a hollow pile of 2 to 4 mm of the pile diameter is excavated from the tip of the pile. By pre-drilling twice as deep, it is possible to create an enlarged root compaction bulb on undisturbed ground, and because the hollow pile is inserted into the enlarged root compaction bulb at least one times the diameter of the pile, the hollow pile It can be firmly established. Furthermore, in the case of high-quality supporting ground such as gravel or gravel, it becomes possible to directly anchor hollow piles to the undisturbed supporting ground as shown in FIG. 11, making it possible to obtain safer supporting piles.

Furthermore, by providing a plug inside the hollow pile, it is possible to prevent the boiling phenomenon when the spiral screw auger is pulled up, and it is possible to reliably create a root-hardening bulb for the hollow pile.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing the state of loosening of the ground during the construction of hollow piles using a conventional construction method.

FIG. 2 is a vertical cross-sectional view showing the loosened state of the ground when hollow piles are anchored in the conventional construction method.

FIG. 3 is a longitudinal sectional view showing the state of expansion of hardened root bulbs created by high-pressure injection using a conventional construction method.

FIG. 4 is a longitudinal sectional view showing the state of construction of an enlarged root hardening bulb using an enlargement bit in a conventional construction method.

FIG. 5 is a longitudinal sectional view showing the occurrence of boiling phenomenon due to the lifting of the spiral screw auger.

FIG. 6 is a longitudinal sectional view showing a hollow pile of the present invention sunk to a predetermined depth.

FIG. 7 is a longitudinal sectional view showing the state of advance excavation according to the present invention.

FIG. 8 is a longitudinal sectional view showing the preliminary excavation to the undisturbed supporting ground of the present invention.

FIG. 9 is a longitudinal sectional view showing a situation in which an enlarged root-hardened bulb is created by pulling up the auger bit while injecting hardened material after completion of preliminary excavation according to the present invention.

FIG. 10 is a longitudinal sectional view showing the hollow pile of the present invention being inserted into an expanded root hardening bulb.

FIG. 11 is a longitudinal sectional view showing a hollow pile of the present invention being anchored directly to undisturbed supporting ground.

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

FIG. 13 is a longitudinal sectional view showing the inside of a hollow pile being plugged with the instant hardening material of the present invention.

[Explanation of symbols]

1...Hollow pile, 2...Auger, 3...Spiral blade, 4...Rotary shaft, 5
…Bit A…Bulb, B…Cut

Claims (3)

[Claims] Claim 1: An auger is inserted into the hollow pile to penetrate the ground, and when the hollow pile reaches a predetermined depth, the diameter of the pile is The method is characterized in that an enlarged root-hardened bulb is created by preliminary digging to a depth of 2 to 4 times the depth of the root-hardened bulb, then a hollow pile is inserted into the expanded root-hardened bulb at least 1 times the diameter of the pile, and then the auger is pulled up. Root hardening method for medium-dug piles. 2. The method according to claim 1, wherein the auger is pulled up, and when it reaches a predetermined position, an instant hardening material is injected from the tip of the auger bit to plug the hollow part of the pile, and then the auger is pulled up the entire length. Root hardening method for hollow piles. 3. The method for root hardening of hollow piles according to claim 2, wherein the hardening material is cement milk and the instant setting material is a mixture of cement and water glass.