JP2001107353A - Displacement reducing ground improvement construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement reducing ground improvement construction method capable of preventing displacement of the improving ground needless to say the surrounding ground without being influenced by the depth and a kind of the ground to be improved and capable of improving the original ground and of preventing displacement by the same execution work machine. SOLUTION: In improving the ground A by creating an improved pile 12 by discharging a ground improving material 1 such as sand in a hollow pipe of an execution work machine in the soil by using compressed air at execution work time, a pile 3 by a gas permeable material 2 such as a crushed stone is preliminarily driven into the ground A to be improved from the hollow pipe of the same execution work machine, and when exhausting compressed air in the atompsphere from the pile 3 after discharging the ground improving material 1 such as sand in the soil, displacement is not imparted to a natural object such as an existing structure and a tree positioned in the vicinity of the improving ground.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement-reducing ground improvement method for reducing ground displacement caused by compressed air when the ground is improved by a method involving the discharge of compressed air into the ground during construction.

[0002]

2. Description of the Related Art There are the following methods for improving the ground by a method that involves discharging compressed air into the ground during construction. That is, (1) a powdery or powdery ground improvement material is discharged into the soil by compressed air, and mixed with the in-situ soil by a stirring blade to improve the ground (Japanese Patent Publication No. 57-58493). ). (2) A liquid ground improvement material is injected into the soil by compressed air, and the injected power is mixed with the in situ soil by stirring to improve the ground (Japanese Patent Publication No. 51-8493). (3) Put sand as soil improvement material into the rotating shaft of the hollow tube, penetrate the ground to a certain depth while rotating the rotating shaft, and then compress into the sand column discharged from the lower end of the hollow tube A method in which a hollow pipe is drawn out while applying the pressure of air to form a predetermined sand pile (Japanese Patent Application Laid-Open No. 53-145810).

In the ground improvement method using compressed air, compressed air is usually collected by an air release mechanism attached to the construction machine. For example, in the ground improvement method of the above (3), a rotary shaft is formed into a square or a fin is provided to form a gap between the outer periphery of the rotary shaft and the ground. There is an air venting mechanism that guides the air through a rotating shaft and collects the air in a hood installed on the ground (see Japanese Patent Application Laid-Open No. 57-61108). However, in the above-described air venting mechanism, it is difficult to maintain the gap when the rotating shaft is long, and the degree of the release of the compressed air varies depending on the type of soil of the ground, which is unstable. Therefore, as an air bleeding mechanism capable of surely bleeding air, there is a mechanism that establishes a passage for guiding used compressed air to the ground in the rotary shaft and recovers the compressed air through the passage (Japanese Patent Publication No. 61-1986)
-16808, JP-B-5-8295, JP-B-62-49409, etc.).

[0004] However, if the ground to be improved has an air permeable stratum, even if there are various air bleeding mechanisms described above,
Part of the compressed air flows through the permeable stratum to the surrounding ground other than the improved ground, causing the surrounding ground to be displaced, such as uplifting or horizontal movement, affecting existing structures on the surrounding ground and natural objects such as trees and trees. give. Therefore, there is a displacement reduction ground improvement method in which an air release mechanism is provided near the periphery of the improved ground to reduce the flow of compressed air from the improved ground to the surrounding ground (see Japanese Patent Publication No. 4-38241).

[0005]

In the displacement reduction ground improvement method disclosed in the above-mentioned publication, since an air release mechanism is provided near the periphery of the ground to be improved, the compressed air passing through the permeable formation passes through the air release mechanism to the atmosphere. This reduces the flow of the compressed air toward the surrounding ground and does not give any displacement to the surrounding ground, which is convenient. However, if the entire improved ground is cohesive soil, the compressed air that could not be collected by the air release mechanism attached to the construction machine of the ground improvement method tends to stay in the improved ground, causing various displacements in the improved ground. Become. In addition, the air bleeding mechanism of the publication example installs a perforated pipe in the vertical hole drilled by an auger-type drilling machine near the periphery of the ground to be improved, and fills and installs the periphery with a filter material such as crushed stone. It is necessary to use a construction machine separate from the original ground improvement method, such as filling the center with coarse crushed stone or the like rather than a filter material instead of a perforated pipe.

Accordingly, an object of the present invention is not to be affected by the depth and type of the ground to be improved, and the surrounding ground is of course prevented from being displaced by the improved ground, and the original ground improvement and displacement prevention are performed by the same construction machine. It is an object of the present invention to provide a displacement reduction ground improvement method capable of performing the above.

[0007]

Under such circumstances, the present inventors have conducted intensive studies and as a result, when improving the ground by a method involving the underground discharge of compressed air at the time of construction, the ground to be improved in advance is required. If a pile made of a permeable material is cast and the used compressed air discharged into the ground by the ground improvement method performed thereafter can be exhausted from the pile, the displacement of the ground can be reduced by the compressed air flowing through the ground. The inventors have found that the present invention can prevent such a situation, and have completed the present invention.

That is, according to the first aspect of the present invention, when the ground is improved by a method involving the underground discharge of compressed air at the time of construction, a pile made of a permeable material is previously poured into the ground to be improved, and thereafter, the pile is formed. It is an object of the present invention to provide a displacement reduction ground improvement method characterized in that compressed air discharged into the ground by the ground improvement method is exhausted from the pile to reduce ground displacement.
By adopting such a configuration, it is possible to discharge the compressed air flowing through the ground from the pile that has been previously poured into the ground to be improved into the atmosphere, and to use existing structures and planting trees on the surrounding ground,
It does not affect natural objects such as trees.

The invention of claim 2 provides a construction machine having substantially the same functions in both the ground improvement accompanied by the underground discharge of compressed air during the construction and the driving of the pile with the permeable material. The method for improving the ground for reducing displacement according to claim 1 is provided. By adopting such a configuration, there is no need to prepare a separate construction machine,
Work costs can be reduced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a displacement reduction ground improvement method according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view showing a displacement reduction ground improvement method according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view showing the construction state of a construction machine used in the displacement reduction ground improvement method according to an embodiment of the present invention. It is. The displacement-reducing ground improvement method of the present invention uses compressed air during construction to discharge a ground improvement material (hereinafter referred to as a ground improvement material) 1 such as sand into the ground, and
Is improved, a pile 3 made of the permeable material 2 is previously placed on the ground A to be improved. In the subsequent construction, when the ground improvement material 1 is discharged or conveyed into the soil, the used compressed air can be exhausted from the pile 3, and the air permeable formation 4 such as a sand layer is formed on the ground A.
If there is, compressed air escapes quickly from the pile 3, and even if there is no air permeable stratum 4 and only the viscous soil layer 5 has a slight air permeability, the compressed air escapes from the pile 3 and reduces the displacement of the ground A It is. Here, as the ground improvement material 1 such as sand, for example, high-quality soil such as sand, remaining soil or a mixture of the remaining soil and another material (solidified material) can be exemplified.

The ground improvement method of reducing displacement according to the present invention can be applied to all ground improvement methods involving the underground discharge of compressed air during construction. In the ground improvement method in the present embodiment, the ground improvement material 1 is put into the hollow pipe 10 and penetrated into the ground A to a predetermined depth while rotating the hollow pipe 10.
Soil improvement material 1 while reversely rotating and lifting up to a predetermined position
Is discharged from the lower end 11 of the hollow tube 10 while applying compressed air thereto, and then the hollow tube 10 is rotated forward to re-penetrate, thereby compacting the ground improvement material 1 and the surrounding ground soil. The ground improvement is carried out by repeating the drawing and intrusion to form an improved pile 12 having an enlarged diameter in the ground A.

The above-mentioned hollow tube 10 is in the shape of a round pipe, and is hung rotatably and vertically by a rotary drive unit 13 and a forced elevating device 14 of a construction machine. Also,
Ground improvement material 1 transported by moving bucket (not shown)
Is supplied from the hopper 15 into the hollow tube 10. Using this same construction machine, the displacement reduction ground improvement method of the present invention can be implemented. That is, the air permeable material 2 may be used instead of the ground improvement material 1.

[0013] In the present invention, a method of driving a pile made of an air-permeable material into the ground to be improved in advance, and then performing a method of discharging the compressed air into the ground at the time of construction, for example, is as follows.
When the ground A to be improved is surrounded by the boundary 20 as shown in FIG. 3, first, the pile 3 is driven along the boundary 20 and the inside thereof is driven by the improved pile 12. Form, the form in which the pile 3 and the improved pile 12 are alternately driven, and the boundary line 20
, The piles 3 are laid in one row in the vertical (horizontal) direction, the improved stake 12 is laid in one row thereafter, and the piles are repeatedly laid. In the case where the pile 3 is driven along the boundary line 20 and the improved pile 12 is driven inside the pile 3, as shown in FIG.
First, the pile 3 is formed and the surrounding ground 21 outside the boundary line 20 is formed.
Do not allow compressed air to flow through. That is, as shown in FIG. 4, the hollow tube 10 is positioned, and the permeable material 2 transported by the moving bucket into the hollow tube 10 is supplied through the hopper 15. Thereafter, the hollow tube 10 penetrates into the ground A to a predetermined depth while rotating, and then the hollow tube 10
The air permeable material 2 is discharged from the lower end 11 of the hollow tube 10 into the opened hole 22 while pulling out by reverse rotation, and the pile 3 is formed on the ground A. Since the pile 3 uses the air-permeable material 2, the compressed air having many voids can be easily discharged. Examples of the permeable material 2 include gravel, crushed stone, slag, and shells. After the pile 3 is driven along the boundary line 20, the improved pile 12 inside the pile 3 may be driven.

In the case where the piles 3 and the improved piles 12 are alternately driven, as shown in FIG. 5, under the situation where there are existing structures 23 and natural objects 24 such as trees on one side 20a of the boundary 20. First, the permeable piles 3a and 3b on the boundary line 20a side are cast, then the improved pile 12a is cast, then the permeable pile 3c is cast, and then the improved pile 12b is cast. A method of placing in this order in a direction away from the line, or placing the air-permeable piles 3a, 3b, and 3c on the boundary line 20a side, and then driving the improved piles 12a and 12b to form a pile near the boundary line 20a side. And a method of sequentially laying them in a direction away from the boundary line. Which of these methods is adopted is not particularly limited as long as it is a casting method that does not cause displacement to the existing structure 23 or a natural object 24 such as a tree.

The piles 3 are laid in a row in the vertical (horizontal) direction along the boundary line 20, the improved stakes 12 are laid in one row thereafter, and the piles are repeatedly laid, as shown in FIG. The present invention is applied in a situation where an existing structure 23 or a natural object 24 such as a tree is located on one side 20a of the line 20. According to this, since the pile near the one side 20a side of the boundary line 20 to be cast first is the permeable pile 3, the spent air discharged into the ground from the subsequently improved pile 12 is not permeable. Discharged to the atmosphere through
It does not cause displacement to existing structures 23 or natural objects 24 such as trees.

Note that the pile 3 does not have to have the same depth as the improved pile 12 as long as the pile 3 has reached the permeable formation 4.

In the present invention, both the ground improvement by the ground improvement material accompanied by the underground discharge of compressed air during the construction and the driving of the pile by the permeable material are performed by construction machines having substantially the same function. be able to. In this case, having substantially the same function means that, for example, construction machines that differ only in sand as a ground improvement material and crushed stone as an air-permeable material to be injected into a hollow pipe, or as one construction machine First, it means that both of these construction machines are included in the case where the crushed stone is cast and the sand pile is driven by another construction machine.

Although the embodiment of the present invention has been described above, the specific configuration is not limited to this, and changes and additions without departing from the spirit of the present invention are within the scope of the present invention.

[0019]

According to the first aspect of the present invention, the compressed air flowing through the ground can be discharged from the air-permeable pile previously cast on the ground to be improved. Therefore, regardless of the depth and type of the ground to be improved, the surrounding ground can of course prevent the displacement of the improved ground and perform the original ground improvement.

According to the second aspect of the present invention, there is no need to prepare a separate construction machine, and the construction cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a displacement reduction ground improvement method according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a construction state of a construction machine used in a displacement reduction ground improvement method according to the embodiment of the present invention.

FIG. 3 is a plan view showing a displacement reduction ground improvement method according to an embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing each step of a displacement reduction ground improvement method according to an embodiment of the present invention.

FIG. 5 is a plan view showing a displacement reduction ground improvement method according to an embodiment of the present invention.

FIG. 6 is a plan view showing a displacement reduction ground improvement method according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ground improvement material 2 Air permeable material 3 Pile (air permeable pile) 4 Air permeable formation 5 Cohesive soil layer 10 Hollow pipe 11 Lower end 12 Improved pile 13 Rotary drive 14 Forced lifting device 15 Hopper 20 Boundary line 21 Peripheral ground 22 Hole 23 Structure 24 Natural object A Improved ground

Claims (2)

[Claims] When the ground is improved by a method involving the discharge of compressed air into the ground at the time of construction, a pile made of an air-permeable material is placed in advance on the ground to be improved, and the pile is then submerged by the ground improvement method. Displacement reduction ground improvement method, wherein discharged compressed air is exhausted from the pile to reduce ground displacement. 2. The method according to claim 1, wherein the improvement of the ground accompanied by the underground discharge of compressed air during the construction and the placing of the pile with the permeable material are both performed by construction machines having substantially the same function. The displacement reduction ground improvement method according to claim 1.