JPH0328416A - Construction method to build up pile - Google Patents

Abstract

PURPOSE:To enhance supporting force by filling cement milk into a drilled hole excavated and a hollow pile is inserted, injecting ground improving material after a single packer is set, setting a double packer, and performing sectional injection of the ground improving material. CONSTITUTION:Soft ground A is drilled by an earth auger, and cement milk having low strength is injected into a drilled hole 2. Next, a hollow pile 4 whereon small holes 5 are drilled is inserted, and a single packer 7 is set at the lower end part of the hollow pile 4. Then, ground improving material in a grout mixer 9 is injected into the pile front part D from the single packer 7 through a grout pipe 11 by a grout pump 10. Successively, the single packer 7 is pulled up, a double packer 12 is set at the lower end part, and sectional injection of the ground improving material 14 is performed into the space between the packers 12 from an injection pipe 13. And, the improving material 14 is released to the pile peripheral part E to enhance adhesiveness of the hollow pipe with the ground A, B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for erecting piles to support architectural structures or civil engineering structures (hereinafter simply referred to as architectural structures, etc.).

[Prior Art] Driven piles, cast-in-place piles, and embedded piles are known as piles for supporting building structures and the like. The embedded pile is
Since the piles are embedded in the excavated holes, they are often used because they produce less noise and vibration than driven piles.

[Problems to be Solved by the Invention] In conventional embedded piles, excavation of the original ground releases stress in the ground, which causes a phenomenon in which the ground at the tip and surrounding areas of the pile loosens. Therefore, due to this ground loosening phenomenon, the peripheral surface friction force and the tip supporting force, which are the supporting forces of the embedded pile, decrease.

Furthermore, even if the ground at the tip of the pile is strong, if the surrounding ground is soft, there is a problem that the supporting building structure or the like may sway laterally.

On the other hand, a construction method is known in which a soil improvement material is injected into soft ground to strengthen the ground (Japanese Patent Publication No. 1-14376, etc.).

An object of the present invention is to provide a method for erecting embedded piles that effectively uses soil improvement materials to increase bearing capacity.

[Means for Solving the Problems] According to the present invention, the ground is excavated, the excavated hole is filled with cement milk of low strength, and a hollow pile with a large number of small holes is inserted into the hole. Then, a single packer is set at the lower end of the hollow pile, a soil improvement material is injected into the tip of the pile, a double packer is set, and the soil improvement material is applied sequentially from above or below to the local part of the pile through the small hole. Interval injection.

It is preferable to provide closing means such as a check valve or a stopper in the small hole and lower end opening of the hollow pile to prevent the inflow of low-strength cement milk and to allow the soil improvement material to flow out.

Furthermore, the filling amount of cement milk having low strength is preferably determined by the product of the cross-sectional area of the gap between the drilled hole and the hollow pile and the depth of the drilled hole.

[Function] In the pile construction method configured as above,
When a hollow pile is inserted into a drilled hole filled with low-strength cement milk, the cement milk is forced to fill the gap between the drilled hole and the hollow pile up to the ground surface.

Therefore, when the soil improvement material is injected through the small holes in the hollow pile, the solidified cement milk prevents the soil improvement material from blowing upward through the gap.

In addition, by injecting the ground improvement material, the ground at the pile tip and around the pile is improved, a columnar solid body is formed integrally with the hollow pile, and the adhesion between the hollow pile and the ground is improved.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, ground A is excavated by an earth auger 1.

When the hole 2 reaches a predetermined depth in the solid ground B as shown in FIG. 2, the excavation is finished and the earth auger 1 is pulled up. Next, the drilled hole 2 is filled with a required amount of low-strength cement milk 3, which will be described later.

Next, as shown in FIG. 3, a number of small holes 5 are formed in the drilled hole 2.
Insert the hollow pile 4 with the holes drilled therein.

As shown in FIGS. 6 and 7, the outer openings of the small holes 5 are provided with a vinyl sheet 6a that covers approximately the upper half of the small holes 5.
and a lower vinyl sheet 6b overlapping the sheet 6a. The sealing means is not limited to the check valve 6, but may also be a single vinyl sheet having the same planar shape as the check valve 6. A single vinyl sheet is provided. In this way, since the small hole 5 and the lower end opening of the hollow pile 4 are provided with a sealing means, when the hollow pile 4 is inserted into the drilled hole 2 filled with cement milk 3, the cement milk 3 is The gap C between the drilled hole 2 and the hollow pile 4 is forcibly filled up to the ground surface. Therefore, the predetermined amount of cement milk 3 is determined by taking into account the product of the cross-sectional area of the gap C and the depth of the drilled hole 2, as well as the amount absorbed by the ground.

Next, as shown in FIG. 4, the single packer 7 is set at the lower end of the hollow pile 4, and the ground improvement material from the grout mixers 9, 9 is pumped from the single packer 7 to the tip of the pile via the grout pipe 11 using the grout pump 10. Inject into part D.

Next, as shown in FIG. 5, the single packer 7 is pulled up and the double packers 12, 12 are set at the lower end (
(The figure shows a state in which the double backers 12, 12 are pulled up and set in the upper part after the injection of the lower part is completed), the ground improvement material 14 is injected from the injection pipe 13 between the packers 12, 12, and the small hole is 5 to the pile circumference E. The injection pressure at this time causes cracks in the solidified cement milk, and the ground improvement material is injected into the ground through these cracks. And double packer 12, 12
, and then sequentially apply soil improvement material 1 to the upper part of the pile circumference E.
Inject 4. As a result, a columnar solid body is integrally formed at the pile tip D and the pile circumference E of the hollow pipe 4, improving the adhesion between the hollow vibe 4 and the ground A and B, and having a bearing capacity equal to or higher than that of a driven pile. get. At this time, the cement milk 4 serves as a sealing material that prevents the ground improvement material 14 from blowing upward from the gap C. Incidentally, in the above embodiments, the injection operation was carried out sequentially from the bottom to the top, but there is no difference in the operation and effect even if the injection is carried out from the top to the bottom.

[Effects of the Invention] Since the present invention is configured as described above, a columnar solid body is integrally formed at the tip and peripheral surface of a hollow pile by injecting a soil improvement material, and the supporting capacity of the pile is increased. By increasing the tip bearing capacity and surface friction force, it is possible to obtain a bearing capacity equivalent to or higher than that of a driven pile.

Therefore, compared to conventional construction methods, the pile diameter can be made smaller.

Furthermore, it is possible to strengthen the ground around the piles, prevent lateral vibrations of building structures, etc., and improve earthquake resistance.

[Brief explanation of drawings]

Figures 1 to 5 show the construction procedure according to the present invention. Figure 1 is excavation, Figure 2 is filling with cement milk, Figure 3 is hollow pipe insertion, and Figure 4 is the tip of the pile of ground improvement material. part injection,
Figure 5 is a vertical sectional view showing the procedure for injecting soil improvement material around the pile, Figure 6 is a side view showing the check valve, and Figure 7 is a sectional view taken along the line X--X in Figure 6. be. A... Soft ground B... Strong ground D... Pile tip E... Pile circumference 2... Hole drilling 3...
Low strength cement milk 4...Hollow vial 5.
...Small hole 6...Check valve 7...Single backer 12, 12...Double backer 14...
・Soil improvement material Figure 4 Figure 5 D D

Claims (1)

[Claims] The ground is excavated, the excavated circumcision is filled with low-strength cement milk, a hollow pile with many small holes is inserted into the excavated hole, a single packer is set at the lower end of the hollow pile, and the pile A method for building piles, which comprises injecting a soil improvement material into the tip, setting a double packer, and injecting the soil improvement material sequentially from above or below into the circumferential portion of the pile through the small holes.