JP3636628B2 - Ground improvement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention supplies powder ground improvement material into the ground, forcibly mixes with the soil in situ, reacts the soil with the ground improvement material, stabilizes the soil properties, and increases the strength. It relates to the ground improvement method.
[0002]
[Prior art]
Conventionally, in this kind of ground improvement method, the air is removed by making the rotary shaft square or by providing fins on the rotary shaft to form a gap between the outer periphery of the rotary shaft and the ground. They are guided to the ground and inserted into a rotating shaft so as to be collected in a hood installed on the ground (see JP-A-57-61108). However, in this conventional example, it is difficult to maintain a gap when the rotating shaft is long, and the degree of air removal varies depending on the type of ground, making it difficult to perform stable ground improvement. Air may remain.
[0003]
Under such circumstances, as a construction method that can perform reliable air venting, (1) The ground improvement material and the mixed fluid of air are discharged into the stirring blades of the hollow body whose top surface is closed and only the bottom surface is open, and the ground improvement There has been disclosed a ground improvement method in which the material is attached to the in-situ soil in the stirring blade and the air is collected on the ground through the inside of the rotating shaft (see Japanese Patent Publication No. 61-16808). (2) An air recovery hood whose inner space is in communication with the air recovery path in the rotation shaft is mounted on the rotation shaft slightly above the stirring blade, and the rotation shaft is lifted and lowered at the lower opening of the air recovery hood. A ground improvement device provided with a lid that automatically opens and closes in response to the above has been disclosed (see Japanese Patent Publication No. 5-8295). In addition, (3) ground improvement material is pumped with air, spouted into the ground at the bottom of the water, and stirred and mixed with the soil in situ, while used air is released into the atmosphere through a hood installed at the bottom of the water, An underwater ground improvement method for applying an air pressure equivalent to the water pressure in the hood is disclosed (Japanese Patent Publication No. 62).
-49409).
[0004]
[Problems to be solved by the invention]
All of the ground improvement methods and the like that can perform air venting in the above-mentioned publications are very convenient because an air passage is created and used air is collected on the ground from the passage. However, in the air passage formed by the conventional construction method, the removal of used air is not always sufficient. That is, in the publication example of (1), the air that has come out of the stirring blade of the hollow body for some reason or the air that has further circulated to the upper surface of the stirring blade is difficult to recover. In the publication examples of (2) and (3), There is a problem that the air that has been removed from the recovery hood is difficult to recover, and adverse effects such as displacement of other structures due to the unrecovered air and suppression of discharge of the ground improvement material occur.
[0005]
In addition, the construction equipment used in the conventional construction method needs to process the stirring blade into a complex shape or install an air recovery hood, which increases the manufacturing cost of the equipment and uses the construction equipment. The structure is difficult to perform, and includes troublesome processes for the operator.
[0006]
Accordingly, an object of the present invention is to provide a simple structure, form an air passage between a pair of rotating shafts and discharge used air to the ground, and to prevent displacement of other structures and discharge of ground improvement materials. It is to provide a ground improvement method that can prevent harmful effects.
[0007]
[Means for Solving the Problems]
In such a situation, the present inventors have intensively studied to achieve the above object, and as a result, the thickness of the steady rest plate installed over the stirring blade between the pair of rotating shafts is set to the axis of the rotating shaft. If the diameter is equal to or greater than the diameter, a part of the in-situ soil existing between the rotating shafts can be sufficiently loosened when the rotating shafts are inserted and withdrawn. It became an escape route, and it was found that used air was discharged to the ground through the escape route of the air, and the present invention was completed.
[0008]
That is, in the present invention, the ground improvement material of the granular material is discharged together with air into the ground in the rotation region of one or more stirring blades provided radially below the pair of rotating shafts, and is stirred and mixed with the in-situ soil. In the ground improvement method in which air is collected on the ground, between the pair of rotating shafts, a bearing portion that is loosely fitted to the rotating shaft at a position above the stirring blade, and a main body that connects the bearing portions vibration provided a stop plate in the across consisting section, the body portion of the bracing plate and a thickness equal to or more than the diameter of the rotating shaft, and be one except the open structure in plan view, the bracing plate the air The ground improvement construction method is characterized in that it is discharged upward through the ground loosened in the step and collected on the ground. By adopting such a configuration, the in-situ soil existing between the pair of rotating shafts and above the agitating blade is sufficient due to the unraveling effect accompanying the upward movement of the steady rest plate having a predetermined thickness when the rotating shaft is pulled out. The loosened in-situ voids in the soil become air passages, and the used air is discharged to the ground through the air passages.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a ground improvement method according to an embodiment of the present invention will be described with reference to FIGS. 1 is a schematic diagram of a construction apparatus used in the ground improvement method according to the embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB. FIG. 4, FIG. 4 is a cross-sectional view of the rotating shaft, FIG. 5 is a schematic diagram for explaining the process of the ground improvement method according to the embodiment of the present invention, and FIG. 6 is taken along line CC in FIG. It is a figure. In the ground improvement method of the present invention, the ground improvement material is a granular material together with air in the ground in the rotation region of one or more stirring blades 2 provided radially below the pair of rotating shafts 1 and 1 of the construction apparatus 10. Is discharged from the ground improvement material discharge port 4 and mixed with the original soil, and the air is recovered on the ground.
[0010]
In the construction apparatus 10, an anti- sway plate 5 is provided between the pair of rotating shafts 1, 1 and above the stirring blade 2. The steady rest plate 5 includes bearing portions 52 and 52 that are loosely fitted to the rotary shaft 1, and a main body portion 51 that connects the bearing portions 52. As shown in FIG. 2 and FIG. 3, the main body 51 is made of a hollow tube having a rhombus cross section, and the thickness dimension W of the main body 51 is larger than the diameter D of the rotating shaft 1. The shape of the main body 51 is not particularly limited as long as the thickness dimension W of the main body 51 is equal to or greater than the diameter D of the rotary shaft 1. For example, the cross section is circular, square, inverted triangular, or Y-shaped. Can also be used. The maximum value of the thickness dimension W of the main body 51 is appropriately determined within a range that does not hinder the rise of the rotating shaft in consideration of the soil quality, the size of the construction device, and the like. Further, the main body 51 is joined to a flat plate having an I-shaped cross section, which is the shape of a steady plate of a conventional construction apparatus, for example, a band-like protrusion having a triangular cross section, and the thickness dimension W of the main body 51 is set. What adjusted so that it may become large may be sufficient. The thickness dimension W of the main body 51 is preferably formed over the entire length of the main body 51, but may be a part of the total length of the main body as long as the soil is loosened to the extent that used air can be discharged. In FIG. 1, reference numeral 6 denotes a co-rotation prevention plate, which is installed to prevent co-rotation of the stirring blades 2 and 2 positioned above and below the co-rotation prevention plate 6 of the rotating shaft 1.
[0011]
The rotary shaft 1 can be lifted and lowered freely by a rotary drive machine 7 of the construction equipment, and is formed into a square pipe shape. As shown in FIG. A circulating passage 15 is passed. A plurality of stirring blades 2a and 2b are provided at the lower part of the rotating shaft 1, and a ground improvement material discharge port 4 is provided on the outer periphery of the rotating shaft 1 at the root portion on the back side in the rotation direction of the one stirring blade 2a. . Further, an air discharge port 3 is provided on the outer periphery of the rotation shaft 1 at the root portion on the back side in the rotation direction of the other stirring blade 2b positioned below the rotation shaft. Both the air discharge port 3 and the ground improvement material discharge port 4 are connected to a passage 15, and this passage 15 is connected to a compressed air discharge air supply facility or a ground improvement material supply facility (not shown) on the ground 13. The rotating shaft 1 may be, for example, a round pipe shape in addition to the square pipe shape. The air discharge port 3 may be used as a ground improvement material discharge port.
[0012]
Next, the ground improvement method according to the embodiment of the present invention will be described with reference to FIG. FIG. 5 is a schematic diagram, and an example in which the stirring blade is one stage per rotating shaft is described for convenience of explanation. When the rotary shaft 7 penetrates the ground 9 while rotating the rotary shaft 1 in the forward rotation direction, compressed air of 3 to 10 kg / cm ² , for example, is omitted from FIG. It discharges from the exit 3, and the ground around the outer periphery of the rotating shaft 1 is loosened beforehand (FIG. 3 (A)). When reaching a predetermined depth, the discharge of air from the air discharge port 3 is stopped, and the rotating shaft penetration step is completed (FIG. 3B). Next, when the rotary shaft 1 is pulled out from the ground while rotating in the reverse direction, the ground improvement material pneumatically transported from the ground improvement material supply facility on the ground 13 is discharged from the ground improvement material discharge port 4 and mixed in the ground. Thus, the improved column 12 is formed. At that time, since the steady plate 5 rises in the ground in the same manner as the rotation shaft, the wide effect of the steady plate main body 51 surrounds the two-dot chain line on the upper position side of the stirring blade 2 in FIG. It is possible to form an in-situ soil loosened in a portion (shaded portion). For this reason, the used air is discharged in the direction indicated by the arrow (C) in FIG. In addition, when the rotary shaft 1 penetrates into the ground, or when both the penetration and the withdrawal are performed, the ground improvement material may be discharged from the ground improvement material discharge port 4 and stirred and mixed in the ground. In addition, rotation of the rotating shaft at the time of extraction is not limited to the reverse direction, and may be the normal direction.
[0013]
According to the present embodiment, the in-situ soil existing between the pair of rotating shafts is sufficiently loosened due to the unraveling effect accompanying the upward movement of the steady plate having a predetermined thickness when the rotating shaft is pulled out. The void in the original soil becomes a passage for air, and the used air is discharged to the ground through the passage for the air.
[0014]
As mentioned above, although embodiment of this invention was described, a specific structure is not limited to this, The change and addition in the range which does not deviate from the meaning of this invention are in the scope of this invention.
[0015]
【Example】
Next, an Example is given and this invention is demonstrated further more concretely.
Example 1
The ground improvement method of the present invention was performed on the X city Y line. The construction apparatus used is the same as that shown in FIGS. The improvement depth was 30 m, and the time for creating one improvement column was determined. The results are shown in FIG. In FIG. 7, the vertical axis represents the depth, the horizontal axis represents the construction time, and the locus of the tip of the rotating shaft is depicted. At point b where penetration started from point a and reached a predetermined depth of 30 m, the ground improvement material discharge port was clogged and the ground improvement material became defective. In order to eliminate this clogging, when the rotating shaft was pulled upward while discharging compressed air from the ground improvement material discharge port 4, the clogging material could be removed at a point c 10m above the predetermined depth 30m. After re-penetration, it reached a point d at a predetermined depth, and then a drawing process was performed. At point e, the rotating shaft was drawn to the ground, and an improved pillar body could be created. The time required from a to e was about 1.5 hours.
[0016]
Comparative Example 1
The rest was performed in the same manner as in Example 1 except that the steady rest plate having an I-shaped cross section was used. In this case, the thickness of the main body portion of the steady rest plate was smaller than the diameter of the rotating shaft. The results are shown in FIG. FIG. 8 is similar to FIG. 7 and shows the locus of the tip of the rotating shaft. In Comparative Example 1, in order to eliminate the first clogging, it was necessary to raise the rotating shaft by 15 to 20 m from a predetermined depth (point h in the figure). Further, since clogging occurred at point i, the same clogging removal process was performed (from point i to point j in the figure). For this reason, the time required from the start point a to the point 1 for completing the formation of the improved pillar was 3 to 4 hours.
[0017]
From Example 1 and Comparative Example 1, it was found that according to the construction method of the present invention, the construction period can be shortened to ½ compared with the conventional construction method.
[0018]
【The invention's effect】
According to the present invention, the in-situ soil existing between the pair of rotating shafts is sufficiently loosened by the loosening effect accompanying the upward movement of the steady rest plate having a predetermined thickness when the rotating shaft is pulled out. The void in the location soil becomes an air escape route, and the used air can be discharged to the ground through the air escape route, preventing adverse effects such as displacement of other structures and suppression of discharge of ground improvement materials. . In this way, the construction period can be shortened to half that of the prior art by simply changing the width dimension of the main body portion of the steady rest plate .
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a construction apparatus used in a ground improvement method according to an embodiment of the present invention.
FIG. 2 is an end view taken along line AA in FIG.
FIG. 3 is a view taken along line BB in FIG. 1;
FIG. 4 is a cross-sectional view of a rotating shaft.
FIG. 5 is a schematic diagram for explaining a process of the ground improvement method according to the embodiment of the present invention.
6 is a view taken along the line CC in FIG. 5C. FIG.
7 is a diagram showing a locus of a tip of a rotating shaft in the construction method of Example 1. FIG.
8 is a diagram showing a locus of a tip of a rotating shaft in the construction method of Comparative Example 1. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotating shaft 2, 2a, 2b Stirring blade 3 Air discharge port (Ground improvement material discharge port)
4 Ground Improvement Material Discharge Port 5 Stabilization Plate 6 Co-rotation Prevention Plate 7 Rotation Drive 9 Ground 10 Construction Equipment 11 Original Soil 12 Improved Pillar 13 Ground 15 Ground Improvement Material and Discharge Air Passage 16 Upward Movement of Stabilization Plate The loosened soil 51 The main body portion of the steady rest plate 52 The bearing portion W The thickness of the main body portion of the steady rest plate D The diameter of the rotating shaft

Claims (1)

The ground improvement material of the granular material is discharged together with air into the ground of the rotation region of one or more stirring blades provided radially below the pair of rotating shafts, and is stirred and mixed with the in-situ soil. In the recovered ground improvement method, between the pair of rotating shafts, a steady rest plate comprising a bearing portion loosely fitted to the rotating shaft at a position above the stirring blade and a main body portion connecting the bearing portions. The main body of the steady rest plate has a thickness equal to or greater than the diameter of the rotating shaft , and excludes the opening structure in plan view, and the ground is loosened by the steady rest plate. A ground improvement method characterized by discharging upward through and collecting on the ground.

Images