JP7169731B2 - ground improvement method - Google Patents

Description

The present invention cuts in-situ soil by injecting a fluid (for example, solidifying material such as cement milk, high pressure air) from an injection device (for example, an injection device provided at the tip of a rod: monitor) that is pulled up while rotating. , relates to a ground improvement method for creating a rotating body-shaped improved body by stirring.

As shown in FIG. 9, irregularities (so-called "corners") are formed on the outer peripheral edge (peripheral surface) of the improved body 10 created in the ground by the ground improvement method. For convenience of illustration, in the attached drawings, the unevenness is expressed larger than it actually is.
FIG. 10 is an enlarged view of the area α in FIG. In FIG. 10, the convex portion related to the outer peripheral edge of the improved body 10 (FIG. 9) is indicated by A1, and the concave portion is indicated by A2. FIG. 11 shows the region α in FIG. 10 developed in the circumferential direction (circumferential direction in FIG. 9) of improved body 10 (FIG. 9).
In FIGS. 10 and 11, convex portions A1 and concave portions A2 having the same width dimension are alternately and continuously arranged in the circumferential direction (horizontal direction in FIG. 11). In FIG. 11, the circumferential width dimension of the convex portion A1 and the concave portion A2 (horizontal direction dimension in FIG. 11: the width dimension of the convex portion A1 and the concave portion A2) is the same. However, the adjacent protrusions A1 and recesses A2 do not always have the same width.
In FIG. 11, the width dimensions of the convex portion A1 and the concave portion A2 are indicated by reference numeral 1PT.

Here, for example, when creating an improved body (underground solidified body) as a countermeasure against liquefaction, the convex part A1 and the concave part A2 are protruded, and the fluid material (for example, solidifying material such as cement milk, high pressure air) The cost of liquefaction countermeasures can be reduced by increasing the reach of the jet. This is because the number of improved bodies to be constructed can be reduced by widening the interval between adjacent improved bodies.
However, the prior art does not propose a technique for increasing the projecting distance of the projection A1 and the recess A2 shown in FIGS.

Other conventional techniques include a rock grout construction method (Patent Document 1) in which pulsating pressure having a specific frequency is superimposed, and a periodic fluctuation of long-wave injection pressure and a periodic fluctuation of short-wave injection pressure are superimposed. A method for grouting sandy ground (Patent Document 2) has been proposed. However, these conventional technologies (Patent Document 1, Patent Document 2) are all technologies related to the injection method, and in-situ soil is formed by injecting a fluid material from a nozzle provided on a rotating injection rod. It does not correspond to the ground improvement construction method that cuts and agitates to form a rotator-shaped improved body, and cannot solve the above-mentioned problems related to liquefaction prevention measures.
A liquid pressurization device capable of preventing pulsation of the pump has also been proposed (Patent Document 3). It is not disclosed that it is applied to a ground improvement method that cuts and stirs to create a rotating body-shaped improvement body, and it is not intended to solve the above-mentioned problems.

Japanese Patent No. 3096244 Japanese Patent No. 5089430 Japanese Patent No. 3508378

The present invention has been proposed in view of the above-mentioned problems of the prior art. To provide a ground improvement method capable of increasing the reaching distance of a fluid jet in the ground improvement method for creating a

As a result of various researches and experiments, the inventors have found that the reason why the outer peripheral edge of the improved body does not have a smooth surface and the convex portion A1 and the concave portion A2 (FIGS. 10 and 11) are formed is the ground side. It was found that the pulsation of a pump in a supply system that supplies a fluid (eg, solidifying material such as cement milk, high-pressure air) to an injection rod (eg, a nozzle at the tip).
In other words, when the discharge flow rate and discharge pressure of the pump decrease due to the pulsation of the pump, a concave portion is formed on the outer periphery of the improved body, and when the discharge flow rate and discharge pressure of the pump increase, a convex portion is formed on the outer periphery of the improved body. The inventor found that.
The inventors have found that if the projections of the irregularities formed by the pulsation of the pump on the outer periphery of the improved body are overlapped with each other, the reach distance of the fluid jet can be increased.

The ground improvement method of the present invention created from such knowledge,
A fluid material (for example, solidifying material such as cement milk, high-pressure air) is jetted from a nozzle (N) provided on a rotating jetting rod (1) to cut, agitate, and rotate the in-situ soil. In the ground improvement method for creating an improved body,
A pump (P) is interposed in the fluid supply system (2),
Due to the pulsation of the pump (P), a convex portion (A1) is formed on the outer peripheral edge of the improved body (10), and the cycle of pump pulsation in the fluid jet forming the preceding convex portion (A1). By equalizing the pulsation cycle of the pump in the fluid jet forming the trailing protrusion (A1), the leading protrusion (A1) and the trailing protrusion (A1) are superimposed to increase the reaching distance of the fluid jet.
Here, the interval between adjacent convex portions (A1) or the interval between adjacent concave portions (A2), width dimension or positional relationship in the circumferential direction of the improved body (10) is expressed as “phase” in this specification. sometimes.
In addition, in this specification, the phrase "overlapping the previously formed convex portion (A1) and the subsequently formed convex portion (A1)" means "the previously formed concave portion (A2 ) and the subsequently formed concave portion (A2)”.
There is no particular limitation on the number of nozzles (N) provided on the injection rod (1). For example, it is possible to provide a single nozzle (N) on the injection rod (1) to perform so-called "single-sided injection".

In the present invention, as shown in FIG. 4, the injection rod (1) is provided with a pair of nozzles (N1, N2), and one nozzle (N2) is connected to the other nozzle (N1) for injection rod ( 1) is arranged at a position eccentric (by a predetermined amount δ1 or central angle δ1) from a position (Nn1) symmetrical with respect to the central axis of 1). A1) is preferably set so as to be superimposed.

In the present invention, as shown in FIG. 5, the rotational speed of the injection rod (1) is varied, and the positions of the nozzles (N3, N4) after the rotational speed is varied are Each nozzle (N3, N4) is displaced by a predetermined central angle (δ2) with respect to the position (Nn3, Nn4) at which it was present, and the leading convex portion (A1) and the trailing convex portion (A1) overlap each other. It is preferable that the rotation speed is set at the same time.

Further, in the present invention, as shown in FIG. 6, the injection rod (1) is provided with a plurality of nozzles (for example, a pair of nozzles N5 and N6: three or more nozzles may be provided). (1) is provided with a plurality of supply systems (2) that supply fluids (for example, solidifying materials such as cement milk, high-pressure air), and a plurality of supply systems (for example, two systems: 2-1, 2-2 ) is connected to one of a plurality of nozzles (eg, two nozzles: N5, N6), and a pump interposed in a plurality of supply systems (eg, two systems: 2-1, 2-2) pulsation cycles are equal.

In addition to this, in the present invention, the interval between the convex portions (A1) depends on the construction specifications of the improvement body construction and the characteristics of the pump (P: the pump interposed in the solidifying material supply system 2: P1, P2, for example). It is preferably determined on the basis of values.
Here, it is preferable to select the speed of pulling up the injection rod (1), the number of repetitions, and the pitch of pulling up as the construction specifications for forming the improved body. Further, it is preferable to select the number of rotations of the pump (P) as the pump characteristic value.

According to the present invention having the above-described configuration, as shown in FIG. Since (A1) overlap each other (as shown in FIG. 2), the tip of the projection (A1) is radially outward, and the position reached by cutting the ground is extended radially outward. As a result, the reaching distance of the fluid material (for example, the solidifying material) constituting the jet increases, so even if the distance from the adjacent improved body 10 (improved body) is long, the tip of the protrusion (A1) (injection device 1 ) are connected to each other.
Therefore, for example, when building the improved body (10) as a countermeasure against liquefaction, even if the distance between the adjacent improved bodies (10) increases as the reach distance increases, the tips of the protrusions (A1) are connected to each other. It can be in a state where That is, even if the interval between the improved bodies (10) is widened compared to the conventional technology, the effect of preventing liquefaction can be maintained at the same level, and the number of improved bodies (10) to be formed can be reduced. I can. Therefore, it is possible to keep the cost low while maintaining the quality of countermeasures against liquefaction.
In addition, by superimposing the previously formed convex portion (A1) and the subsequently formed convex portion (A1), the previously formed concave portion (A2) is formed subsequently. The recesses (A2) are superimposed so that the modified area expands radially outwards.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows typically the principle in the embodiment of this invention. It is explanatory drawing which shows typically the state by which the convex parts were superimposed. FIG. 10 is an explanatory diagram showing the merits when the reaching distance is increased; BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory sectional drawing which shows 1st Embodiment of this invention. It is explanatory sectional drawing which shows 2nd Embodiment of this invention. It is explanatory sectional drawing which shows 3rd Embodiment of this invention. FIG. 7 is a block diagram of the third embodiment of FIG. 6; FIG. 8 is an explanatory diagram of a modification of the embodiment of FIGS. 1 to 7; FIG. It is explanatory drawing which shows the cross-sectional shape of the improved body created by the soil improvement method. FIG. 10 is an enlarged cross-sectional view showing a region indicated by symbol α in FIG. 9; FIG. 11 is an explanatory diagram showing FIG. 10 by expanding it;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
First, the principle of embodiments of the present invention will be described with reference to FIGS. 1-2.
Here, in the ground improvement method according to the illustrated embodiment, a fluid material (for example, solidifying material such as cement milk, high pressure air) is injected from the injection device (nozzle N at the tip of the injection rod 1) that is pulled up while rotating. The in-situ soil is cut, stirred, and mixed with the solidifying material to form the improved body 10 (see FIG. 9) in the shape of a rotating body. The fluid is supplied to the injection rod 1 via a supply system (for example, supply system 2-1 or 2-2 in FIG. 7), and the supply system includes a pump (for example, pump P1 or P2 in FIG. 7). intervened.
1 and 2 schematically illustrate the principle of superimposing convex portions A1 (convex portion A11 and convex portion A12) formed on the outer peripheral edge of the improved body 10 when forming the improved body 10 in the form of a rotating body. clearly shown.

In FIG. 1 in which the outer peripheral edge of the improved body is developed in the circumferential direction, the arrangement (or phase) of the convex portion A11 and the concave portion A21 indicated by solid lines in the upper part of FIG. 1 and the dotted line in the lower part of FIG. The arrangement (or phase thereof) of the displayed convex portion A12 and concave portion A22 is the same. Here, the width dimension of the convex portions A1 (A11, A12) or the concave portions A2 (A21, A22) in FIG. 1 is indicated by the symbol PT.
In FIG. 1, the sign "+ (plus)" means that the phase indicated by the solid line in the upper part of FIG. 1 and the phase indicated by the dotted line in the lower part of FIG. there is
In FIGS. 1 and 2, for the sake of simplification, the width dimensions and intervals of the protrusions A1 (A11, A12) or the recesses A2 (A21, A22) are exactly the same. However, in actual construction, the width dimensions and intervals of the protrusions A1 (A11, A12) or the recesses A2 (A21, A22) are not the same and often differ. Even in such a case, the convex portions A1 are overlapped with each other.

A specific mode for superimposing the phase indicated by the solid line in the upper part of FIG. 1 and the phase indicated by the dotted line in the lower part of FIG. 1 will be described later with reference to FIGS.
FIG. 2 schematically shows a state in which the phase indicated by the solid line in the upper part of FIG. 1 and the convex part A1 of the phase indicated by the dotted line in the lower part of FIG. 1 are superimposed.
In FIG. 2, the convex portion A1 indicated by the solid line shows the state before the convex portions are superimposed on each other. 2, the diameter is expanded upward (the excavation distance of the convex portion A1 increases). In other words, in FIG. 2, the convex portion A1 indicated by the solid line indicates a state in which the convex portions A1 do not overlap each other, and the convex portion A1A indicated by the dotted line indicates a state in which the convex portions A1 overlap each other. Although not clearly shown, as the protrusions A1 overlap each other, the recesses A2 also expand radially outward (upward in FIG. 2). In FIG. 2, the area where the diameter of the concave portion A2 is enlarged is indicated by a dotted line.

In FIG. 3, the solid lines indicate that in the improved bodies (underground solidified bodies) 10-1 and 10-2 adjacent to each other, the convex portions are not superimposed and the amount of protrusion of the convex portions A11 and A12 increases. indicates a state in which the In the state indicated by the solid line, the convex portion A11 on the side of the improved body 10-1 and the convex portion A12 on the side of the improved body 10-2 are separated from each other. Therefore, in order to effectively take measures to prevent liquefaction in the state indicated by the solid line in FIG. 3, the distance between the two improved bodies 10-1 and 10-2 must be shortened.
On the other hand, if the protrusions A11A and A12A are formed by superimposing the protrusions on each other and the radially outward protrusion amount of the protrusions A11 and A12 is increased as indicated by the dotted line in FIG. If the distance is increased), adjacent improvements 10-1 and 10-2 are connected to each other, as indicated by the dotted line in FIG. As a result, even if the distance between the two improved bodies 10-1 and 10-2 is not shortened, effective liquefaction prevention measures can be taken.
Although not explicitly shown in FIG. 3, the effective diameters D1 of the two improved bodies 10-1 and 10-2 are the same. Therefore, if the convex portions A1 are overlapped with each other as described in FIGS. -1 and 10-2 can be connected to effectively prevent liquefaction.

FIG. 4, which is an explanatory diagram of the first embodiment of the present invention, is an example of a specific method for superimposing a convex portion A11 indicated by a solid line in the upper part of FIG. 1 and a convex portion A12 indicated by a dotted line in the lower part of FIG. is shown. As described above, the formation of the convex portions A1 (A11, A12) and the concave portions A2 (A21, A22) is caused by the pulsation of the pump in the supply system.
As shown in FIG. 4, a pair of nozzles N1 and N2 for injecting the solidifying material are provided at two positions (positions near both ends in the diametrical direction) on the outer circumference of the injection rod 1. As shown in FIG. The nozzle N2 is positioned opposite to the direction of rotation of the injection rod 1 (arrow CW direction) ( It is eccentric in the counterclockwise CCW direction) by the amount indicated by the central angle δ1.

Here, the solidifying material is supplied to the nozzles N1 and N2 from, for example, the same supply system (same pump).
In addition, the central angle δ1 corresponding to the amount of eccentricity is determined by the pulsation cycle of the pump in the solidifying material jet forming the preceding convex portion A1 (for example, convex portion A11 in FIG. 1) and the following convex portion A1 (for example, in FIG. Considering the pulsation cycle of the pump in the solidifying material jet that forms the convex portion A12) of No. 1, the leading convex portion A1 and the trailing convex portion A1 are set to overlap each other.
Therefore, by eccentrically moving the nozzle N2 by a central angle δ1, a convex portion A1 (for example, Fig. 1 Convex portion A12) is opposed to the convex portion A1 (for example, convex portion A11 in FIG. 1) on the outer peripheral edge of the improved body formed in the region where the solidifying material jet flow ejected from the nozzle N1 cuts, stirs, and mixes are superimposed.

Therefore, when the injection rod 1 rotates and pulls up while injecting the jet of the solidifying material from the injection rod 1, the projection A1 in the area cut, stirred, and mixed by the jet of the solidifying material injected from the nozzle N2. The position (or phase) overlaps with the position (phase) of the convex portion A1 in the region to be cut, stirred, and mixed by the solidifying material jet jetted from the preceding nozzle N1 (for example).
Then, since the preceding convex portion A1 (for example, convex portion A11 in FIG. 1) and the succeeding convex portion A1 (for example, convex portion A12 in FIG. 1) are superimposed, in convex portion A1, solidification material jet flow The reach in the formed refinement 10 increases radially outward.

In the illustrated embodiment, the direction of rotation of the injection rod 1 is clockwise (the direction of the arrow CW), so in the right half of FIG. , and the convex portion A1 in the area where the jet of the solidifying material is injected from the nozzle N2 becomes the trailing convex portion. Then, the trailing protrusion A1 formed by the jet from the nozzle N2 overlaps the leading protrusion A1 formed by the jet from the nozzle N1.
On the other hand, in the left half of FIG. 4, the convex portion A1 formed by the jet flow of the solidifying material from the nozzle N2 is the leading convex portion, and the convex portion A1 formed by the jet flow of the solidifying material injected from the nozzle N1 is the trailing convex portion. become a department. Then, the leading convex portion A1 formed by the jet of the solidifying material from the nozzle N2 and the trailing convex portion A1 formed by the jet of the solidifying material injected from the nozzle N1 overlap each other.
Therefore, in both the right half area and the left half area in FIG. 4, the leading convex portion and the trailing convex portion are superimposed, and the reaching distance of the improved body 10 is increased.

According to the first embodiment of FIG. 4, the convex portion A1 (for example, the convex portion A12 in FIG. 1) formed subsequent to the previously formed convex portion A1 (for example, the convex portion A11 in FIG. 1) is Since the nozzles N2 can be superimposed, by deviating the nozzle N2 by the central angle δ1, the convex portions A1 overlap each other as shown in FIG. increases in the direction of As a result, even if the adjacent improved bodies 10 are separated from each other, the tips of the projections A1 (the points farthest from the injection device) are connected to each other.
Therefore, for example, when forming the improved body 10 as a countermeasure against liquefaction, the liquefaction prevention effect can be exhibited by connecting the tips of the convex portions A1 to each other. By increasing the distance between the improved bodies 10, the number of improved bodies 10 to be formed can be reduced, and the cost can be kept low.

FIG. 5 shows a second embodiment. In FIG. 5, a pair of solidifying material injection nozzles N3 and a N4 is provided.
In the second embodiment of FIG. 5, each time the injection rod 1 rotates halfway (in the direction of the arrow CW), the rotation is temporarily stopped and rotated again (in the same direction). The time at which the rotation of the injection rod 1 is stopped is phased by a central angle δ2 with respect to the positions Nn3 and Nn4 (indicated by dotted lines in FIG. 5) where the nozzles N3 and N4 would have existed if the rotation had not been stopped. It is time equivalent to being late. The central angle δ2 is an angle at which the preceding convex portion A1 (for example, the convex portion A11 in FIG. 1) and the following convex portion A1 (for example, the convex portion A12 in FIG. 1) overlap, and is used to set (control) the rotation speed. determined by

By temporarily stopping the rotation every half rotation of the injection rod 1, a delay corresponding to the central angle δ2 occurs as shown in FIG. The positions (phases) of the projections in the region where is jetted and the positions (phases) of the projections in the region where the solidifying agent jets are jetted from the nozzles N3 and N4 after restarting the rotation after stopping It is eccentric (phase lags) by the amount of time. The eccentricity (phase delay) corresponds to the central angle δ2, whereby the convex portion A1 (for example, the convex portion A11 in FIG. 1) formed before stopping the rotation and the convex portion A11 formed after stopping the rotation. The convex portion A1 (for example, the convex portion A12 in FIG. 1) is superimposed.
Therefore, also in the second embodiment of FIG. The reaching distance of the solidification agent jet at is increased.
Other configurations and effects of the second embodiment are the same as those of the first embodiment shown in FIG.

6 and 7 show a third embodiment of the invention.
In FIG. 6 as well, the injection rod 1 is provided with two nozzles N5 and N6 arranged point-symmetrically with respect to the center O of the rod 1. As shown in FIG.
The third embodiment has two solidifying material supply systems 2. The first solidifying material supply system 2-1 communicates with the first nozzle N5, and the second nozzle N6 communicates with the second solidifying material supply system 2-1. 2 is connected to the solidifying material supply system 2-2.

As shown in FIG. 7, the first solidifying material supply system 2-1 includes a first solidifying material supply source 3-1 and a first pump P1, and rotates the injection rod 1 for rotary excavation. It is connected to the injection rod 1 via a mechanism 4 . Although not clearly shown, the first solidifying material supply system 2-1 is connected to the first nozzle N5 arranged on the rod 1. As shown in FIG.
On the other hand, the second solidifying material supply system 2-2 is provided with a second solidifying material supply source 3-2 and a second pump P2. It is connected to the injection rod 1 . Although not clearly shown, the second solidifying material supply system 2-2 is connected to the second nozzle N6 arranged on the rod 1. As shown in FIG.

The position (phase) of the projections in the area cut, stirred, and mixed by the solidifying material jet jetted from the first nozzle N5 via the first solidifying material supply system 2-1 is the first solidifying material supply system 2-1. It is determined based on the pulsation cycle of the first pump P1 interposed in the supply system 2-1. In addition, the position (phase) of the projections in the area cut, stirred, and mixed by the solidifying material jet jetted from the second nozzle N6 via the second solidifying material supply system 2-2 is the second It is determined based on the pulsation cycle of the second pump P2 interposed in the solidifying material supply system 2-2.
Then, considering the pulsation cycle of the first pump P1 and the pulsation cycle of the second pump P2, the convex portion formed by the solidifying material jet flow ejected from the first nozzle N5 and the second nozzle N6 It is set so that the projections formed by the jets of the solidifying material jetted from are superimposed on each other.
In the third embodiment of FIGS. 6 and 7 as well, since the positions of the projections formed by the jets ejected from the first nozzle N5 and the second nozzle N6 overlap (synchronize in phase), the solidification material The jet's reach increases radially outward.
Other configurations and effects of the third embodiment are the same as those of the embodiment of FIGS. 4 and 5. FIG.

In the embodiments of FIGS. 4 to 7, the width dimensions of the recesses and protrusions on the outer peripheral surface of the improved body (the circumferential dimension of the outer peripheral surface of the improved body) are shown to be the same. However, in actual construction sites, the width dimensions of the concave portion and the convex portion are often not the same. For example, as shown in FIG. 8, there is a case where the width dimension of the concave portion A2A (vertical dimension in FIG. 8) is larger than the width dimension B of the convex portion A1 (vertical dimension in FIG. 8). Alternatively, a case opposite to that in FIG. 8 also exists.
Even in such a case, the trailing protrusion may be superimposed on the leading protrusion in the manner described in the embodiments of FIGS. 4 to 7, for example.
4 to 7 can be applied even if the ratio of the width dimension of the recesses and protrusions on the outer peripheral surface of the improved body (the circumferential dimension of the outer peripheral surface of the improved body) is different from that in FIG. Thus, the trailing protrusion can be superimposed on the leading protrusion.

In each embodiment shown in FIGS. 4 to 8, the control amount (control parameter) such as the interval and width of the convex portion A1 is determined by the construction specifications of the improved body construction and the pump P (which is installed in the solidification material supply system 2). pumps: for example P1, P2).
Alternatively, it is determined based on the construction specifications for creating the improved body, the characteristic values of the pump P, and the ratio of the widths of the convex portion A1 and the concave portion A2 (improved body circumferential dimension).
Here, as construction specifications for forming an improved body, there are the lifting speed of the injection rod 1, the number of repetitions, and the lifting pitch. Further, the number of revolutions of the pump P is one of the pump characteristic values.

It should be noted that the illustrated embodiment is merely an example and is not intended to limit the technical scope of the present invention.
For example, in FIGS. 4-6, the injection rod is provided with a pair of nozzles, but it is also possible to provide three or more nozzles. Furthermore, in FIG. 5, it is also possible to provide a single nozzle on the injection rod to perform a so-called "single-side injection".

1 ... Injection rods 2, 2-1, 2-2 ... Solidifying material supply system (fluid material supply system)
DESCRIPTION OF SYMBOLS 10... Improved body A1... Convex part A2... Concave part N, N1, N2, N3, N4, N5, N6... Nozzle P, P1, P2... Pump

Claims (5)

In a ground improvement method in which a fluid material is jetted from a nozzle provided on a rotating jetting rod to cut and agitate the in-situ soil to create a rotating body-shaped improvement body,
A pump is interposed in the fluid supply system,
Due to the pulsation of the pump, a convex portion is formed on the outer peripheral edge of the improved body, and the cycle of the pump pulsation in the fluid jet forming the leading convex portion and the fluid jet forming the trailing convex portion. Soil improvement characterized by equalizing the pulsation cycle of the pump in and overlapping the previously formed convex portion and the subsequently formed convex portion to increase the reaching distance of the fluid jet Construction method. A pair of nozzles is provided on the injection rod, one nozzle is arranged at a position symmetrical to the central axis of the injection rod of the other nozzle, and the amount of eccentricity is the same as that of the preceding convex portion. The ground improvement method according to claim 1, wherein the trailing convex portions are set so as to overlap. When the rotation speed of the injection rod fluctuates, the position of each nozzle after the rotation speed fluctuates is displaced by a predetermined center angle with respect to the position where each nozzle exists when the rotation speed does not fluctuate. 3. The ground improvement method according to claim 1 or 2, wherein the rotation speed is set so that the portion and the trailing convex portion are superimposed. The injection rod is provided with a plurality of nozzles, the injection rod is provided with a plurality of supply systems for supplying a fluid, each of the plurality of supply systems is connected to one of the plurality of nozzles, The ground improvement method according to claim 1, wherein the pulsation cycles of the pumps interposed in the plurality of supply systems are equal. The ground improvement method according to any one of claims 1 to 4, wherein the intervals between the convex portions are determined based on the construction specifications of the improvement body construction and the characteristic values of the pump.

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