JPH0860654A - Construction method of pile with bag - Google Patents

Abstract

PURPOSE: To make it possible to surely expand a bag body to a specific form in order that the ground can be surely excavated regardless of its high collapse- efficiency and to enable the revealment of bearing force as designed. CONSTITUTION: After a bearing ground is excavated for a pile burying position with an auger bit 1, the auger bit 1 is withdrawn while discharging solidifiable fluid 9 from the front end of the auger bit 1 to mix with excavated soil, and after that, the solidifiable fluid 9 is left alone until it is solidified, in the pile burying position, a prefabricated pile equipped with a bag body 4 on the outer circumference of the front end section is settled up to the bearing ground after the bearing ground is expanded and excavated with the auger bit 1. The solidifiable fluid 9 is poured into the bag body 4, and a foot protection bulb 5 is developed in the front end section of the pile.

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 pile with a bag, in which cement milk or concrete is injected into a bag attached to the tip of the pile to form a rooted bulb.

[0002]

2. Description of the Related Art Conventionally, a bag is attached to the end of a ready-made pile, and the pile is sunk in the ground that has been enlarged and excavated by the pre-boring method. A method of forming a bulb is known. This construction method is disclosed, for example, in JP-A-62-215719 and JP-A-62-63721. The conventional method is the auger bit 21 as shown in FIG.
Immediately after the ground is expanded and excavated by the
A pile 23 with a bag is sunk in the bag, and the solidified fluid 2
9 is injected and inflated to a predetermined diameter, and a root-fixing bulb 25 is formed near the tip of the pile. This rooting bulb 25
With the creation of, a large supporting force can be expressed.

[0003]

However, in the conventional method, the excavation hole wall 26 collapses after the ground is enlarged and excavated until the bagged piles 23 are sunk, and the earth and sand are removed by the excavation hole bottom portion 2.
It was sometimes thickly deposited on 7. In particular, in the standard penetration test, the sand with a low N value or the ground mixed with gravel tends to collapse, and the accumulated soil prevents the bag from expanding and the bag cannot expand to a predetermined shape. there were. Therefore, in such a case, there was a phenomenon that the bearing capacity of the pile could not be achieved as designed. Therefore, in such a case, it has been attempted to maintain the stability of the excavation hole wall 26 by introducing bentonite or the like into the excavation hole 28, but this is not reliable.

The present invention is intended to solve the above-mentioned problems, and even when a pile with a bag is constructed on a highly collapsible ground, the borehole wall collapses after preboring with an auger bit. It is intended to provide a construction method in which the bag body can be surely inflated without causing the occurrence of a stable supporting force as designed.

[0005]

According to the present invention, after excavating a pile burying position to a support ground with an auger bit, a solidifying fluid is discharged from the tip of the auger bit to mix the excavated soil with the auger bit. After recovering the bit, it is left to stand until the solidifying fluid is solidified, and at the pile burying position, the support ground is expanded and excavated again, and the ready-made pile with the bag body attached to the outer peripheral surface of the tip is supported. It is a construction method of a pile with a bag, which is characterized by sinking to the ground, and then injecting a solidifying fluid into the bag body to solidify a root at the tip of the pile to form a bulb.

[0006]

According to the present invention, since the excavation is carried out by the auger bit, the solidified fluid is discharged and mixed with the excavated soil to be solidified, the auger bit is excavated again, and the pile sunk tip is enlarged and excavated. The excavation wall does not collapse even on low-grade loose ground, and the excavation hole wall can be kept stable. Therefore, it is possible to surely inflate the bag body of the pile with the bag that is sunk.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below with reference to the drawings. FIG. 1 is a conceptual diagram of the construction method of the present invention. First, as shown in (a), the ground is excavated straight while discharging water or the like from the tip of the auger bit 1, or only the tip is enlarged and excavated to reach the support layer. Next, as shown in (b), the solidifying fluid 9 is discharged from the tip of the auger bit, and the auger bit is collected while mixing with the excavated soil. Then, as in (c), the solidifying fluid 9 is allowed to stand until it is solidified. Then (d)
As described above, the auger bit is used to excavate to the supporting ground, and the tip is enlarged. After collecting the auger bit, the bagged pile 3 is sunk as shown in (e). Finally, as in (f), the solidifying fluid 9 is injected into the bag to form the root-hardening bulb 5.

The piles used in the present invention are steel pipe piles, concrete piles and steel pipe concrete composite piles. A bag is attached to the outer peripheral surface of the tip of the pile by a band. In addition, an injection pipe for injecting the solidifying fluid into the bag body is provided in the pile in the thick portion, that is, in the hollow portion of the pile. The material of the bag used in the present invention is synthetic fiber such as nylon, polyester, vinylon, polypropylene and the like. In this way, when the synthetic fluid is used, the water in the solidifying fluid can be discharged to the outside when the solidifying fluid is injected, so that the strength of the completed root-hardening bulb can be increased.

The setting in the present invention means that the strength of the ground-improved soil obtained by mixing the solidifying fluid and the soil is 2 to 30 in uniaxial compressive strength.
It is kg / cm ² . 5-10 kg / from the viewpoint of resistance to soil collapse and penetration of auger bit during excavation
cm ² is preferred. The excavation diameters d and D of the excavation performed in (a) are preferably equal to or larger than the excavation diameters d ′ and D ′ of the excavation performed in (d), or about 10 cm. That is,
This is because it is necessary to sufficiently spread the caking fluid 9 on the peripheral surface 10 of the drill hole wall 6 so as not to collapse the drill hole wall 6 by the expanded drilling performed in (d). Also,
The auger bit 1 has a structure in which only the tip can be expanded and excavated (for example, one with an expanded excavation blade 14 etc.), which reduces the amount of earth and sand discharged, and the solidifying flow used in (b). This is preferable because it reduces the number of animals 9. Furthermore, the rod 11 above the auger bit 1 is preferably a screw-shaped one or one with a stirring arm 12 so that the injected solidifying fluid 9 and the excavated soil can be easily mixed. Although the solidifying fluid 9 discharged into the ground in (b) is generally cement milk,
Depending on the ground conditions, a grout material having silicate soda as a base material may be used.

The amount of the solidifying fluid used depends on the ground conditions, but in the case of cement milk having a water-cement ratio of 60 to 70%, the volume ratio is 5 to 20 with respect to the excavation volume.
% Is preferable. It is necessary to fill the solidified fluid to at least the upper surface of the highly collapsible formation. In (c), it is necessary to leave it until the caking fluid is sufficiently set. When cement milk is used as the caking fluid, it is left for about 2 hours or longer.

After that, a construction method similar to the conventional construction method is performed. In the excavation performed in (d), in order to increase the excavation efficiency,
It is better to discharge the drilling fluid such as water from the tip of the auger bit 1. Further, at the bottom portion 7 of the excavation hole, some hardening material 1 such as cement milk is used for the purpose of filling a gap with the root consolidation bulb 5.
It is better to throw in 3. In the expanded excavation hole 2 thus formed, the excavation hole wall 6 is formed by the solidifying fluid 9.
Since it has been improved to a solid ground, there is no danger of it collapsing.

Therefore, the subsequent steps (e) and (f) can be performed extremely smoothly and reliably. That is, since the rooting bulb 9 can be reliably formed into a predetermined shape, a large supporting force can be stably ensured.

[0013]

The present invention will be described in detail below with reference to examples. Five piles 3 with bags were constructed by the construction method of the present invention. The support layer was a gravel layer distributed in GL-20m to 25m, but was a ground in which a highly collapsible gravel layer was present in GL-13m to 16m. For the construction method of the present invention, an excavating jig having a structure shown in FIG. That is, the outer diameter of the rod 11 having an outer diameter of 200 mm is 600 mm, and the outer diameter at the time of enlarged excavation is 95 mm.
An auger bit 1 having a size of 0 mm was installed. The auger bit 1 was used to excavate up to GL-23m and expand the range of the tip 3m. Then water cement ratio 7
0% cement milk was introduced into the excavation hole 8 at a volume ratio of 10% with respect to the excavation volume, mixed with excavated soil by the stirring arm 12 of the rod 11, and then the auger bit 1 was recovered. It was left for about 2 hours until it set. Next, an outer diameter of 530 is attached to a rod with an outer diameter of 200 mm.
mm, and the auger bit 1 having an outer diameter of 860 mm when expanded and excavated was installed, and re-excavation was performed. The excavation length was also GL-23m, and the range of the tip 3m was enlarged and excavated.
An SC pile having an outer diameter of 500 mm and a length of 23 m with a nylon bag having an outer diameter of 900 mm and a length of 3 m attached to the tip was sunk to the GL-23 m in the excavated hole. As a result of injecting cement milk with a water-cement ratio of 60% into the bag from the ground, it is possible to create 5 root-fixing bulbs 5 of the size as designed, that is, root-fixing bulbs 5 having an outer diameter of 800 mm to 860 mm. did it.

[0014]

[Comparative Example] Five piles having the same specifications as those of the example were constructed on the same ground by the conventional method as shown in FIG. As a result, it was possible to produce only 5 to 70% of the root-consolidating bulbs having a predetermined shape, that is, the root-consolidating bulbs having an outer diameter of 650 mm to 700 mm. As a result of the excavation investigation, it was found that the bag body expansion was hindered because the hole wall collapsed and gravel accumulated on the bottom surface of the hole.

[0015]

EFFECTS OF THE INVENTION According to the method of the present invention, even when a pile with a bag is constructed on a highly collapsible ground, when preboring with an auger bit, the solidified fluid is discharged into the excavation hole to excavate the excavated soil. Since the mixture is mixed with and coagulated and excavated again with the auger bit, the bag wall can be surely inflated without collapsing the hole wall. Therefore, a large supporting force as designed can be expressed.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a construction method of the present invention.

FIG. 2 is a conceptual diagram of a conventional method.

[Explanation of symbols]

 1 Auger Bit 2 Expanded Drilling Hole 3 Bag Pile 4 Bag Body 5 Rooting Bulb 6 Drilling Hole Wall 7 Drilling Hole Bottom 8 Drilling Hole 9 Solidifying Fluid 10 Circumferential Surface of Drilling Hole Wall 11 Rod 12 Stirring Arm 13 Cement Milk Hardened materials such as 14 Expanded drilling blade 21 Auger bit 22 Expanded drilled hole 23 Bagged pile 24 Bag body 25 Rooting bulb 26 Drilled hole wall 27 Drilled hole bottom 28 Drilled hole

Claims (1)

[Claims] 1. After excavating a pile burying position to a support ground with an auger bit, a solidifying fluid is discharged from a tip of the auger bit to collect the auger bit while mixing with excavated soil, and then solidified. After leaving the fluidized material to solidify, at the pile burying position again, after enlarging and excavating the support ground with an auger bit, the ready-made pile with the bag body attached to the tip outer peripheral surface is sunk to the support ground, and then the A method for constructing a pile with a bag, comprising injecting a solidifying fluid into a bag body to solidify a root at a tip of the pile to form a bulb.