JP2003213674A - Underground pile forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an underground pile forming method for forming a field- constructed underground pile capable of compacting a soft ground. <P>SOLUTION: This method comprises a penetration process for normally rotating an auger 2 (rotating the auger in the direction of carrying out soil) to penetrate a construction ground G to the depth corresponding to the vertical dimension of the underground pile 10 to be created, an auger raising process for reversely rotating the auger 2 (in the direction reverse to the normal rotation) to raise the auger 2 by a prescribed distance h, and a compression process for injecting a solidifying agent Mc while reversely rotating the auger 2 in the state of holding the underground position, and the auger raising process and the compression process are repeated. <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 an improvement in a technique for forming an underground pile having a relatively small diameter such as a mortar pile.

[0002]

2. Description of the Related Art Conventionally, for underground piles with a relatively small diameter that can be constructed with a digging column car, etc., concrete mortar piles are manufactured at a factory, etc. and transported to the construction site. We were driving into the ground at the site using a pile driver.

Since the underground pile used here is generally long in length, it requires a lot of space and labor for manufacturing and storing in a factory, and it is particularly difficult to carry and handle it. It was From such a problem, it is very convenient if piles can be directly constructed in the construction ground at the construction site.

In addition to this, when the ground to be constructed is a soft ground such as a sand layer, in order to prevent liquefaction, as in the case where the filling grout method is constructed using underground piles, Is preferably compacted.

However, a technique for compressing or filling the soft ground by the on-site underground pile and thereby compacting the soft ground (by forming the on-site underground pile) has been conventionally proposed. Not not.

[0006]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned problems of the prior art, and it is an underground pile for on-site construction, which is capable of compacting soft ground. The purpose is to provide a construction method for middle piles.

[0007]

The method for constructing an underground pile according to the present invention is a method for vertically constructing an underground pile (10) to be formed by rotating the auger (2) forward (rotating in the direction in which the auger carries out soil). Penetration process that penetrates the construction ground (G) to the depth corresponding to the direction dimension, and reverse rotation of the auger (2) (reverse direction of normal rotation)
Then, the auger raising process of raising the auger (2) by a predetermined distance (h), and the reverse rotation (auger downward movement) while maintaining the underground position of the auger (2) (for example, by the auger driving equipment on the ground side) And a compressing step of compressing the soil (in the region (1)), and the auger raising step and the compressing step are repeated (claim 1).

In carrying out the present invention, a solidifying material (eg cement milk Mc) is injected in the auger raising step (eg from the tip of the auger 2) (claim 2). Alternatively, in the compression step (for example, from the tip of the auger 2), a solidifying material (for example, cement milk Mc) is injected (claim 3). In this case, it is preferable to inject the solidifying material (for example, cement milk Mc) (for example, from the tip of the auger 2) when performing both the auger raising step and the compression step.

Further, in the present invention, it is preferable to have a core material inserting step of inserting (for example, press-fitting) a core material (for example, steel material such as H steel or pile) after pulling out the auger from the construction ground (claim 4). ).

According to the present invention having the above-mentioned structure,
Using the auger drive equipment on the ground side, the auger (for example, an auger composed of a pipe with a spiral rotary blade (cutter) that pierces the ground: 2) is rotated in the rotation direction (drilling). While rotating and raising the soil in the direction opposite to the rotation direction in which the soil is carried out (forward rotation direction), and /
Or, at the time of compressing the soil in the region below the auger by rotating in reverse while keeping the position of the auger in the ground (compressing step),
A solidifying material (for example, cement milk: Mc) is jetted from (for example, the tip of) the auger (2).

When the solidifying material is sprayed in the auger raising step, the solidified material sprayed (eg cement milk: M
c) is stirred with the ground by the rising auger. on the other hand,
When the solidifying material is sprayed in the compression step, the sprayed solidifying material is mixed with the soil which is pressurized and moves to the lower region as described later.

In the compression process, if the auger (2) is rotated in the reverse direction while maintaining the underground position, the soil cut by the auger (2) will cause the auger (2) to have a continuous spiral rotor blade (4). ) Along the vertical direction. Therefore, the area below the auger (2) is pressed and compressed by the soil (moving vertically downward).

As a result of the area under the auger (2) being pressed and compressed by the soil (moving vertically downward),
The injected solidification material (Mc) such as cement milk (in the auger rising step and / or the compression step) mixes with the soil in the injected area and compresses the surrounding soil (G) to exceed the elastic range. Plastically deform. In other words, the area under the auger (2) is pressurized, so that the surrounding soil (or the surrounding ground) of the part where the auger (2) penetrates.
Since (G) is compressed and compacted, liquefaction of soft ground is prevented.

The auger raising process and the compressing process are repeated until the auger (2) is extracted from the ground.
That is, the compression of the surrounding ground (G) by the solidifying material (Mc) described above is performed for each rising amount (predetermined distance h) when the auger (2) is rising. During the ascending step of the auger (2), unless the position of the auger (2) in the ground is maintained, the soil does not move downward along the auger rotor (4), and the auger (2) itself rotates and the ground side. Move (up) (up)
To do. During this time, the soil does not move downward and the lower region is not pressurized, but since the soil is plastically deformed as described above, (while the solidifying material is not pressed downward in the auger rising step, ,) The soil will not be restored.

[0015]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an auger 2 used in the present invention and a state in which an auger drilling hole d is bored by the auger 2. An auger 2 to which a normal and reverse rotational force and vertical movement are freely applied by an auger driving facility on the ground (not shown) is erected in the soft ground (G).

The auger 2 is spirally connected to a tubular pipe 3 for introducing a solidifying material, and the rotary blades 4 are arranged at an equal pitch to form a pipe end portion 3.
It is installed up to the vicinity of a. The rotary blade 4 is formed of hard steel capable of cutting the ground G, in which the left rotation is formed in the forward excavation direction and the right rotation is formed in the reverse upward direction in the figure.

A stirring blade 5 is provided at the tip of the rotary blade 4 at a right angle to the pipe axis and in a horizontal direction, and the ground G1 in the auger drilling hole d is stirred by the rotation of the pipe 3.

The tip 3a of the tube 3 is formed in a conical shape,
The tip 3a is provided with a nozzle 3b for injecting cement milk Mc, which is a solidifying material supplied from the ground.

In FIG. 2, an auger 2 having an auger hole d drilled to a depth H in the ground G is raised by a predetermined length h to create a ground G1 in the injection area and cement milk Mc is injected. The state is about to be reached (auger rising process).

The compression process described above is shown in FIGS. In the compression step, as shown in FIG. 3, first, the cement milk Mc is injected and injected from the nozzle 3b of the auger 2 which has risen to the predetermined length h into the ground G1 under stirring.

FIG. 4 is a detailed view of the portion B of FIG. 3, showing the relationship between the outer diameter of the rotary blade 4 and the auger drilling hole d. The gap δ between the rotary blade 4 and the auger boring d is the cement milk Mc described later.
The front surface 4a of the rotary blade 4 is made of mortar which is a mixture of mortar and cutting soil.
It is necessary to make the gap so that the pressing force does not leak upward when pressing with.

In the illustrated embodiment, cement milk Mc, which is a solidifying material, is injected in the stage (compression step) of FIG. However, in the auger raising process shown in FIG.
The cement milk Mc may be jetted from the nozzle 3b at the tip of the auger 2. When the cement milk Mc is sprayed in the auger raising step, the cement milk Mc and the soil are mixed immediately after spraying due to the reverse rotation of the auger. Here, in both the auger raising process shown in FIG. 2 and the compression process shown in FIGS. 3 and 4, it is most desirable that the cement milk Mc be injected from the nozzle 3b at the tip of the auger 2.

FIG. 5 shows a state in which a mortar pile 10 (for example, about φ = 600 mm) having an auger drilling hole d as an outer diameter is formed in the ground G.

Construction of the mortar pile 10 will be described with reference to the above-mentioned drawings with reference to the flow chart of FIG.

In step S1, preparation for mortar pile construction is made. Selection of mortar pile construction position, installation of auger drive, preparation and placement of mortar and other members.

In step S2, as shown in FIG. 1, the auger 2 is penetrated into the construction ground G to form an auger drilling hole d.
The auger 2 is rotated in the forward direction, that is, in the excavated soil discharging direction, and penetrates to the bottom portion Bd having a predetermined depth H corresponding to the vertical direction of the underground pile to be constructed. By the penetration of the auger 2, the soil in the auger drilling hole d is stirred and cut. At this time, due to the nature of the ground G, the stirring blade 5 does not have a large resistance during penetration. Further, the auger drilling hole d is bored while being careful not to exceed the outer diameter of the rotary blade 4. This step S
2 is a penetration process.

In step S3, as shown in FIG. 2, the auger 2 is rotated in the reverse direction so as to be raised by a predetermined distance h from the bottom portion Bd of the auger drilling hole d. And cement milk injection area G
Create 1. This step S3 is an auger raising process.

At step S4, as shown in FIG.
While rotating the auger 2 in the reverse direction at a position elevated by a predetermined distance h from d, the cement milk Mc is pressure-fed and injected from the nozzle 3b toward the injection region G1. The injected cement milk Mc mixes with the ground soil in the injection area G1. The mixture of cement milk Mc and soil is compressed by the earth pressure in the auger drilling hole d applied to the front surface 4a (see FIG. 4) side of the rotary blade 4 of the auger 2 rotating at the constant height position h, and is stirred by the stirring blade 5. While being kneaded, the soil G is compressed and compacted by the pressure P toward the outside of the auger drilling hole d. The soil G outside the auger drilling hole d is compressed and transformed from a fluid elastic region to a plastic deformation region to become stable soil. This step S4 is a compression process.

In the process drawings shown in FIGS. 1 to 5, FIGS.
Cement milk M in the compression step (step S4) of
Although c is jetted from the auger tip, as described above, the cement milk Mc may be jetted from the auger tip in the auger raising step. In that case, the above step S3
At, cement milk Mc is injected. Of course, it is possible to inject the cement milk Mc from the auger tip in both the auger raising step and the compression step. In that case, cement milk is injected in step S3 and step S4.

Next, in step S5, it is confirmed whether or not the auger 2 can be further raised by h. If there is room for ascent (Yes in step S5), the process returns to step S3 to repeat the auger raising process and the compressing process to form the mortar layer of the next stage and add the mortar pile. In this case, the step of raising the auger in step S3 is performed before the mortar is solidified.

On the other hand, (pressure feeding step of steps S3 to S5)
If there is no room for raising the auger 2 (after the raising process is repeated) (No in step S5), the formation of the mortar pile 10 in the auger drilling d is completed as shown in FIG. 5 (FIG. 6). "E").

In this way, the mortar pile 10 is constructed using the soil of the soft ground G, and the soil around the mortar pile 10 is transformed into stable soil without fluidity.

When the mortar pile 10 is formed, it is preferable that the mortar pile 10 has a core material (made of H steel or other steel material or pile) embedded therein. FIGS. 7 and 8 show an embodiment in which such a core material is embedded. When constructing the embodiment shown in FIGS. 7 and 8, first, all the steps described above with reference to FIGS. 1 to 6 are performed to form a mortar pile as shown in FIG.

Next, as shown in FIG. 7, H steel 20 (core material) is embedded in the mortar portion Mt of the mortar pile by a known / existing method. FIG. 8 shows H steel 2 in the mortar portion Mt.
The state in which 0 is embedded is shown in a plan view.

The illustrated embodiment is merely an example,
It is additionally noted that the description is not intended to limit the technical scope of the present invention.

[0036]

The effects of the present invention are listed below. (1) A mortar pile can be created in the soft ground and the surrounding ground can be compacted by an auger composed of a spiral rotor provided on the pipe and a stirring blade provided at the tip of the pipe. (2) Since the ground to be ground is kneaded with cement milk to form a mortar pile, it is possible to eliminate the soil disposal process associated with the auger boring.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a step of penetrating an auger into the ground according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a step of raising a penetrating auger by a predetermined distance.

[Fig. 3] Cement milk (solidifying material) from the nozzle at the tip of the pipe
Sectional drawing which shows the process of injecting and stirring.

FIG. 4 is an enlarged view of a local area B in FIG.

FIG. 5 is a cross-sectional view showing a state in which a mortar pile is formed.

FIG. 6 is a flowchart showing a construction method of the present invention.

FIG. 7 is a cross-sectional view showing a state in which a core material is embedded in a mortar pile.

FIG. 8 is a plan view similar to FIG.

[Explanation of symbols]

d ... Auger drilling G: Soft ground GL ... the ground surface 2 ... Ogre 3 ... tube 3a ... Conical end 3b ... Nozzle 4 ... Rotary blade 5 ... Stirrer

Claims (4)

[Claims] 1. A penetrating step for penetrating the construction ground to a depth corresponding to the vertical dimension of the underground pile to be formed by rotating the auger forward, and an auger rising for rotating the auger backward to raise the auger by a predetermined distance. An underground pile construction method comprising a step and a compressing step of compressing soil by rotating the auger in a state in which the auger is kept in the underground position, and repeating an auger raising step and a compressing step. 2. The underground pile construction method according to claim 1, wherein a solidifying material is injected in the auger raising step. 3. The underground pile construction method according to claim 1, wherein a solidifying material is injected in the compression step. 4. The underground pile construction method according to claim 1, further comprising a core material inserting step of inserting the core material after pulling out the auger from the construction ground.