JP4625573B2 - Ground improvement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ground improvement method for creating a large number of ground improvement piles by high-pressure jetting of a hardened material into the ground to be improved and stirring and mixing.
[0002]
[Prior art]
In this type of ground improvement method, there are cases where adverse effects such as expansion and deformation of the ground due to high-pressure injection of a hardener into the ground may occur. For example, when creating a new ground improvement pile around the existing ground improvement pile, the surrounding ground expands by the volume equivalent to the volume of the hardened material injected to create the new ground improvement pile. It is also assumed that excessive side pressure acts on the improved pile and destroys it.
[0003]
Conventionally, as a countermeasure against such a problem, a high-pressure jet stirrer provided with a double rod or a triple rod is used to inject a hardening material into the ground together with air or water. In that case, the hardened material reaches farther than when only the hardened material is sprayed, so that the range of improvement can be expanded (that is, a large-diameter ground improvement pile can be created), and the hardened material It is said that by discharging slime to the ground surface during jetting and ground improvement piles, volume expansion due to ground improvement is alleviated and ground deformation is also reduced.
[0004]
[Problems to be solved by the invention]
However, in the method of injecting the hardened material into the ground together with air and water as described above, the cost is higher than in the case of injecting only the hardened material, and the high-pressure jet agitator used therefor is also complicated and large. Not only that, but a part of the hardened material sprayed together with air and water is ejected to the surface of the earth, which causes another problem that the waste mud slime needs to be collected with a vacuum car and disposed of as industrial waste. .
[0005]
In view of the above circumstances, an object of the present invention is to provide an effective ground improvement method capable of preventing an adverse effect on the ground due to injection of a hardener when a ground improvement pile is created.
[0006]
[Means for Solving the Problems]
The invention of claim 1 is a ground improvement method for creating a large number of ground improvement piles by injecting and mixing a hardener into the ground to be improved, and then using a drilling machine first with respect to the ground to be improved. A rod having a stirrer blade and a hardener injection hole at the tip after forming a hole and performing soil removal corresponding to an increase in the ground volume by hardener injection carried out in the subsequent stage, after pulling out the hole drilling machine after allowed to reach the hole bottom by penetrating the rod prior drilling in using a high pressure injection mixer, pulling the rod while allowed injecting a hardening material around the previous drilling of a cured material injection holes Rukoto having a Thus, a ground improvement pile having a diameter larger than that of the preceding drilling hole is formed around the preceding drilling hole.
[0007]
The invention of claim 2 is characterized in that, when the ground improvement method of the invention of claim 1 is carried out, the diameter of the preceding drilling hole formed by the drilling machine is made equal to the diameter of the stirring blade in the high-pressure jet agitator. And
[0008]
The invention of claim 3 is a new ground improvement which fills the gap between existing ground improvement piles by implementing the ground improvement construction method of claim 1 or 2 between existing ground improvement piles. It is characterized by creating piles.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the ground improvement method of the present embodiment is renewed so as to fill a gap between existing ground improvement piles 1 (hereinafter abbreviated as existing piles 1) that have already been created. The present invention is applied when the ground improvement pile 2 is created.
[0010]
In this case, by simply injecting a hardening material between the existing piles 1 to create a new ground improvement pile 2, the ground volume between the existing piles 1 is greatly expanded, and an excessive lateral pressure acts on the existing pile 1. Therefore, there is a concern that the existing pile 1 may be damaged by the side pressure. Therefore, in the present embodiment, the ground improvement pile 2 is created by the process shown in FIGS. I have to.
[0011]
Pre-drilling process First, using a general-purpose drilling machine 3 as shown in FIG. 2, for example, an earth auger equipped with a screw rod 4, the pre-drilling hole 5 is formed between the existing piles 1 as shown in FIG. To do. The diameter of the preceding drilled hole 5 may be set as appropriate as long as it can be formed between the existing piles 1, but is preferably set to be approximately equal to the diameter of the agitating blade 8 in the high-pressure jet agitator 6 used in the subsequent process. Then, when the preceding drilling hole 5 is formed, the earth removal corresponding to the increase in the ground volume by the subsequent injection of the hardener is performed in advance. More specifically, after the screw rod 4 is rotated forward and penetrates into the ground, a predetermined amount of soil may be discharged by using both forward rotation and reverse rotation during pulling.
[0012]
In addition, when the existing pile 1 is not formed vertically, or when the existing pile 1 bulges sideways in the middle, the screw rod 4 is provided when forming the preceding hole 5. Interference with the pile 1 is also assumed, but in that case, the existing pile 1 may be shaved without any problem. Of course, by using an earth auger as the hole drilling machine 3, even in such a case, it is possible to cut the existing pile 1 without hindrance and to form the preceding hole 5 vertically with high accuracy.
[0013]
-High-pressure jet stirring process Next, the ground improvement pile 2 is created using the high-pressure jet stirring machine 6 as shown in FIG. The high-pressure jet agitator 6 in the illustrated example is of a general-purpose boring machine type, and has a single-tube rod 7 that injects only a hardened material at a high pressure, and has a stirring blade 8 and a hardener injection hole (not shown) at the tip. ), And the rod 7 is inserted into the preceding drilled hole 5 formed earlier. At this time, as described above, the diameter of the preceding hole 5 is set to be approximately the same as the diameter of the stirring blade 8 so that the rod 7 can be penetrated very easily. There is almost no need to have.
[0014]
As shown in FIG. 3 (b), the stirrer blade 8 is brought to the bottom of the preceding hole 5, and then the hardener is injected at a high pressure from the hardener injection hole to the surroundings, and the rod 7 is rotated and stirred by the stirrer blade 8. The rod 7 is pulled up while mixing. Thereby, as shown in (c), the ground improvement pile 2 having a diameter larger than that of the preceding hole 5 is formed. At this time, the reach of the hardened material is set to cover the entire gap between the existing piles 1 as shown by the chain line in FIG. The hardening material injection specification measures the amount of mud discharged on site and sets the injection time of the hardening material in consideration of this and the arrival distance of the hardening material (the injection amount per hour and the injection pressure are constant). In such hardener injection, since a part of the improved range has been removed in advance, the existing pile 1 is not damaged, and thus the ground improved pile 2 formed is not cylindrical and the existing pile 1 is not damaged. It is formed in a shape that naturally fills in the shape of the gap between them. Of course, since the earth equivalent to the increase in the ground volume assumed by the hardener injection has already been made, the ground does not greatly expand or deform between the existing piles 1.
[0015]
As described above, after the pre-drilled hole 5 is formed between the existing piles 1 by the drilling machine 3 such as an earth auger and a predetermined amount of soil is removed in advance, the high-pressure jet agitator 6 injects the hardened material at a high pressure. By forming the ground improvement pile 2 by stirring, the ground improvement pile 2 can be efficiently constructed so as to reliably fill the entire gap between the existing piles 1, and the existing pile 1 is excessively large. There is no fear of damaging it due to side pressure.
[0016]
In addition, although the said embodiment is an example in the case of applying when forming the ground improvement pile 2 newly between the existing piles 1, this invention is not restricted to such a case, The expansion | swelling of ground, It can be widely applied to cases where deformation is a concern. For example, in the case where the ground improvement pile 2 is formed so as to be in contact with the existing structure 10 as shown in FIG. 5, first, the preceding drilling hole 5 is first formed in the same manner as described above, and then a predetermined amount of soil is discharged. By forming the ground improvement pile 2 in a state of wrapping the ground improvement pile 2 around the center, it is possible to prevent the expansion and deformation of the ground due to the curing material injection, and the adverse effect that excessive side pressure is applied to the existing structure 10 Can be prevented.
[0017]
In addition, the diameter of the preceding hole 5 is preferably equal to the diameter of the agitating blade 8 as in the above embodiment, but the diameter is not necessarily limited thereto, and the agitating blade 8 can be provided with a hole forming performance. In such a case, the leading hole 5 may be formed in a small diameter, and the rod 7 may be penetrated while the diameter thereof is expanded by the stirring blade 8.
[0018]
【The invention's effect】
According to the first aspect of the present invention, first a prior drilling hole is formed on the ground to be improved by a drilling machine, and the earth corresponding to the increase in the ground volume by the subsequent hardening material injection is performed in advance. Since the hardened material is sprayed from the inside of the hole to the periphery to create a ground improvement pile with a diameter larger than that of the preceding hole, it is possible to effectively prevent deformation and expansion of the ground due to the injection of the hardened material. Adverse effects can be prevented.
[0019]
In the invention of claim 2, since the diameter of the preceding drilling hole formed by the drilling machine is made equal to the diameter of the stirring blade in the high-pressure jet agitator, the rod of the high-pressure jet agitator can be easily inserted into the preceding drilling hole. Therefore, it is not necessary to give a hole-drilling performance to the stirring blade and the rod.
[0020]
In the invention of claim 3, a new ground improvement pile is created between the existing ground improvement piles by carrying out the above ground improvement construction method between the existing ground improvement piles. It is possible to efficiently construct a ground improvement pile that reliably fills the entire gap, and there is no concern that the existing ground improvement pile will be damaged due to excessive side pressure.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overview of a ground improvement method according to an embodiment of the present invention.
FIG. 2 is a view showing a preceding drilling step.
FIG. 3 is a view showing a high-pressure jet stirring step.
FIG. 4 is a process diagram of the same.
FIG. 5 is a diagram showing another embodiment of the present invention.
[Explanation of symbols]
1 Existing ground improvement pile (existing pile)
2 Ground improvement pile 3 Drilling machine (earth auger)
4 Screw rod 5 Pre-drilling hole 6 High-pressure jet agitator 7 Rod 8 Stirring blade

Claims (3)

In the ground improvement method that creates a large number of ground improvement piles by injecting and mixing the hardened material into the ground to be improved and mixing it, first the pre-drilling hole is formed on the ground to be improved using a drilling machine and the subsequent stage A high-pressure jet agitator equipped with a rod having a stirring blade and a hardener injection hole at the tip after the earth removal corresponding to the increase in the ground volume due to the injection of the hardener carried out in Fig. central after allowed to reach the hole bottom by penetrating the rod prior drilling in by pulling Rukoto rod while allowed injecting a hardening material around the previous drilling of a cured material injection hole, the leading drilling using As a ground improvement construction method, it is characterized by creating a ground improvement pile with a diameter larger than that of the preceding drilling hole. The ground improvement method according to claim 1, wherein the diameter of the preceding hole formed by the hole drilling machine is made equal to the diameter of the stirring blade in the high-pressure jet agitator. By carrying out the ground improvement method according to claim 1 or 2 between the existing ground improvement piles, a new ground improvement pile that fills the gap between the existing ground improvement piles is created. The ground improvement construction method.

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