JPH1136282A - Improved post construction method in ground improvement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct a post improved in the full length homogeneous strength by excavating while a solidifying material liquid is discharged from the ground surface of a designated position into underground, stopping the discharge of the solidifying liquid when it reaches a designated depth, and pulling a drilling rod at a designated pulling speed while agitation is repeatedly performed extending over a designated length. SOLUTION: First an excavator 8 is installed in a position where to construct an improved post, the center of the improved post to be constructed is fixed, and the shaft center of a drilling rod 7 is aligned therewith. When dry excavation is performed to a designated depth, a part where to form an improved post is excavated at a designated speed while a designated quantity of a solidifying material liquid is discharged from the lower end of the drilling rod 7. When the depth of excavation reaches a predetermined depth, the discharge of the solidifying liquid is stopped, and then the drilling rod 7 is repeatedly moved up and down in rotation for agitation extending from the lower end of the lower end of dry excavation part to the lower end of excavation to uniformly mix the liquid. After the end of repetition, the drilling rod 7 is pulled at a designated pulling speed while agitating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of constructing an improved column in ground improvement for the purpose of equalizing the strength of the ground improvement column.

[0002]

2. Description of the Related Art Conventionally, improved pillars in ground improvement have been constructed in layers while controlling excavation speed and the amount of solidified material liquid to be excavated while discharging solidified material liquid. .

[0003]

According to the above-mentioned conventional construction method, an improved column of the same quality can be formed in the case of a homogeneous layer (for example, a sand layer or a clay layer). There was a problem that the strength of the improved column was different.

As described above, if there is a difference in strength between the improved columns,
When subjected to an earthquake or other lateral external force, stress concentrates near the boundary of the strength difference, and eventually causes buckling failure.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems by eliminating the local strength change of the improved pillar by repeatedly performing the vertical construction when the improved pillar is constructed. It was done.

That is, according to the present invention, if a position where an improved pillar is set is determined, excavation is performed while discharging solidified material liquid from the surface of the position toward the ground, and when a predetermined degree of progress is reached, Stop discharge of the solidification liquid, repeat over a predetermined length,
An improved column construction method in soil improvement characterized by pulling up a drill rod at a predetermined pulling speed while stirring. The repetition of the predetermined length is performed over the upper and lower portions of the formation thickness, over the entire length of the improved column, or only at the tip portion. Further, the repetition of the predetermined length is characterized in that it is performed at least over and under different formations and while discharging the solidification liquid. The composition is determined in advance for each mixing, and the composition of the solidifying material liquid discharged at the time of stirring is a standard composition.

The excavation speed in the present invention varies depending on the geology, but is usually 1-2 m / min for sandy soil and 0.5-1 m / min for clay layer. Strength (for example, equal to or less than 10 kg per square centimeter)
Depends on If the discharge amount of the solidifying material liquid (for example, cement milk) in the above is kept constant, the rate of the solidifying material liquid will inevitably increase if the excavation speed decreases, but the solidifying material liquid amount will increase in proportion to the excavation amount. It can also be determined. In short, it is only necessary to control the strength of the improved pillar.

The ground improvement technology of the present invention can be used for various purposes, such as the foundation of a relatively lightweight building, the prevention of consolidation settlement of the foundation, the prevention of lateral flow, slip failure, and the strengthening of the backside of the buckle. .

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, repetition is performed after excavation is completed or during excavation in order to make the strength of an improved column uniform.

The above-described repetition improves the unevenness of the strength in the vertical direction.

[0011]

Embodiment 1 An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, first, a construction machine is installed at the construction position of the improved column, the center of the improved column to be constructed is determined, and the center of the excavation rod is aligned with this. Next, when the hollow portion is dug to a predetermined depth, a portion to be an improved pillar is dug at a predetermined speed while discharging a predetermined amount of solidifying material liquid from the lower end of the drill rod. When the excavation depth reaches a predetermined depth, the discharge of the solidification liquid is stopped, and then the operation is repeated over the entire length from the lower end of the empty excavation portion to the excavation lower end. Specifically, the drilling rod moves up and down while rotating. The above repetition can be uniformly mixed by stirring the drill rod up and down three to six times over the entire length. When the repetition is completed, the drilling rod is pulled up while stirring at a predetermined pulling speed, and the improved column construction at this location is completed. On the other hand, the fixing material liquid is supplied at a predetermined flow rate while sufficiently mixing and kneading the cement-based solid material and a required amount of water into a mixer and checking with a flow meter.

In the above, when the flow rate is constant, the mixing ratio between the excavated soil and the solidified material liquid can be adjusted by adjusting the excavation speed.

In the above embodiment, the agitation was performed over the entire length of the improved column.
By repeating the excavation end portion over a predetermined length, an improved column having substantially uniform strength can be obtained.

[0014]

Embodiment 2 An embodiment of the present invention will be described with reference to FIGS. In order to carry out the present invention, the excavator 8 is set at a predetermined position, and excavation is started after the axis of the excavation rod 7 is aligned with the center line of the improved column 9. The drill rod 7 used in the present invention has the inner pipe 2 inserted through the outer pipe 1 and the drill head 3 fixed to the lower end of the inner pipe 2. A frame 5 is fixed to the lower end of the outer tube 1, the lower end of the inner tube 2 is inserted into the frame 5, and stirring rods 4, 4 are drilled in this portion in the radial direction. In the figure, reference numeral 6 denotes an annular body fitted to the inner tube 2 to support the frame 5, and the upper end of the inner tube 2 is connected to a power (not shown). Therefore, only the inner pipe 2 and the excavating head 3 rotate, and the outer pipe 1 and the frame 5 do not rotate, so that the excavated soil is crushed by the stirring rods 4 and 4 and crushed by the frame 5 and eventually excavated. The soil undergoes sufficient crushing and kneading and mixes with the solidified material liquid to form a homogeneous improved column.

According to the present invention, as shown in FIG.
0, an extra portion 11 and an improved portion 12. Further, as shown in FIG. 5, the solidifying material liquid is discharged at the time of excavation, and after the discharge is stopped, a predetermined range 13a (one part) or 13b (full length) is obtained.
Repeat to pull up the drill rod.

At the time of the repetition, the solidifying material liquid may be slightly discharged, but if the total amount of the solidifying material liquid is kept substantially constant, a homogeneous improvement column can be formed.

[0017]

According to the present invention, repetition is performed over a predetermined length after excavation, so that the strength of the improved column is equalized.

Therefore, even if an external force is applied to the improved column from the lateral direction due to an earthquake or the like, there is no possibility that the column will be destroyed from an overlapping portion of different strata, and the effect of ground improvement can be sufficiently exhibited.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is an explanatory view showing a construction state. (A) State before excavation. (B) Excavation start state. (C) Excavation to the planned depth. (D) The state where the drilling rod is pulled up after the repetition.

FIG. 3 is a front view in which a part of the drilling rod is omitted.

FIG. 4 is a cross-sectional view showing an improved range.

FIG. 5 is an explanatory diagram showing a discharge range of a solidifying material liquid.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer pipe 2 Inner pipe 3 Drilling head 4 Stirrer bar 5 Frame body 6 Ring body 7 Drilling rod 8 Excavator 9 Improved column 10 Empty digging part 11 Surplus part

Claims (4)

[Claims] When a position where the improvement pillar is set is determined, excavation is performed while discharging the solidifying material liquid from the surface of the position toward the ground. An improved column construction method in ground improvement, characterized in that the discharge is stopped, the drill is repeated over a predetermined length, and the excavating rod is pulled up at a predetermined pulling speed while stirring. 2. The method according to claim 1, wherein the repetition of the predetermined length is performed over the vertical direction of the formation layer, over the entire length of the improved column, or only at the tip. An improved pillar construction method for ground improvement. 3. The improved column construction method in ground improvement according to claim 1, wherein the repetition of the predetermined length is performed at least over and under different layers and while discharging the solidified liquid. . 4. The ground according to claim 1, wherein the composition of the solidified material liquid during excavation is a predetermined composition for each layer, and the composition of the solidified material liquid discharged at the time of stirring is a standard composition. Construction method of improved pillar in improvement.