JP4003997B2 - Ground improvement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ground improvement method for improving the ground by creating an improved body in the ground.
[0002]
[Prior art]
The so-called “jet grout method” is well known as a very effective method for such ground improvement. This method (hereinafter referred to as “ground improvement method” or “conventional method”, etc.) is obtained by cutting a boring hole in the ground to be improved and inserting a rod with a monitor at the tip into the boring hole. A ground improvement material (including) jet is sprayed in a horizontal direction from a nozzle provided in the ground to mix the ground cutting and the improvement material. Then, while mixing with the ground cutting and improving material, the rod is pulled up to the ground side while rotating. Thereby, it is possible to create a cylindrical improvement body made of a mixture of the ground and the ground improvement material and having a radial dimension equal to the jet reach distance.
[0003]
Here, when it is necessary to improve the ground over a relatively wide range, as shown in FIG. . In that case, it is common to perform construction by overlapping a part (partial region) of the improved bodies 1, 2, and 3 so that no unreformed portion is generated.
[0004]
However, in the area shown with hatching in FIG. 15 (overlapping area), the improved body once formed is cut and mixed with a jet to be improved again. In particular, the central area indicated by reference numeral 123 is improved a total of three times. In this way, improving the same region a plurality of times means that the ground improvement material is consumed more, which causes the construction cost to increase.
[0005]
In addition, when the overlap region of the improved body is cut with a jet, the improved body is a mixture of ground improvement material, so the slurry generated when cutting with the jet must be treated as industrial waste. . Here, there also exists a problem that the cost of processing of industrial waste increases and causes construction costs to increase.
[0006]
On the other hand, as shown in FIG. 16, the constructed improvements 1, 2, 3, 4 are constructed so that they do not overlap, and only the unimproved areas indicated by reference numerals 6 and 7 are improved in a separate process. It is also possible to do.
[0007]
However, with the technique shown in FIG. 16, it is quite difficult to create the improved bodies 1, 2, 3, and 4 so that no overlap region is generated. In addition, it is difficult to perform construction so that only the unimproved areas 6 and 7 are improved, and special equipment or the like is required.
[0008]
[Problems to be solved by the invention]
The present invention has been proposed in view of the above-described problems of the prior art, and does not generate an overlapping region as described above, and does not generate an unimproved region. Therefore, the purpose is to provide a ground improvement method that enables ground improvement over a wide range.
[0009]
[Means for Solving the Problems]
According to the present invention, a step of inserting a rod provided with a monitor into a boring hole cut in the ground to be improved, a fluid for cutting the ground from a nozzle provided in the monitor, or a ground improvement material is provided. A jet injection step of jetting and mixing the ground cutting and the improvement material, and a step of pulling up the rod while rotating the rod, and in the jet injection step, the region of the region where the ground is cut and mixed with the improvement material In the jet injection step, the nozzle provided in the monitor revolves around the central axis of the rod, and the member provided with the nozzle itself. The angular speed at which the nozzle revolves is different from the angular speed at which the member provided with the nozzle rotates.
[0010]
According to the present invention having such a configuration, a closed shape improvement body having a non-circular cross section, for example, an improvement body having a rectangular cross section, is formed. Therefore, there is no area that is improved (overlap area). Therefore, the amount of ground improvement material used for at least the overlap region is saved. In addition, when cutting the ground by jet injection, there is no need to cut the overlap part, so there is no need to process the industrial waste generated by cutting the overlap part, and the industrial waste processing cost is correspondingly reduced. Can save.
[0012]
In particular, when the cross-sectional shape of the region where the ground is cut and mixed with the improvement material is a square, the angular velocity at which the nozzle revolves (revolution angular velocity) and the angular velocity at which the member provided with the nozzle rotates (rotational angular velocity) It is preferred that the ratio is approximately 3: 1.
[0013]
As a result of various researches, the inventors have found that when the above-mentioned conditions are satisfied, the revolution trajectory drawn by the nozzle is the same as a square having sides equal in length to the improved body having a square cross section to be created. It has been found that when an equilateral triangle having a length side moves inscribed, it coincides with the locus drawn by the center of gravity of the equilateral triangle. Therefore, if the reach distance of the jet ejected from the nozzle is equal to the distance from the vertex of the equilateral triangle to the center of gravity, the ground is cut and mixed so as to have a square cross section by the jet.
[0014]
In carrying out the present invention, it is preferable that the jet is constituted by a so-called cross jet, and the nozzles are provided in a pair so as to form a cross jet. This is because the intersecting jet can control the jet reach with high accuracy.
[0015]
Further, according to the present invention having the above-described configuration, it can be implemented with a simple mechanism, the assembly cost and the construction cost can be reduced, and the labor spent on the ground improvement method can be saved.
[0016]
In addition, the cross-sectional shape of the improved body can be changed by performing extremely simple improvements or changes, such as changing the ratio between the rotation angular velocity and the revolution angular velocity, so that the applicable range is extremely wide.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to FIGS.
[0018]
FIG. 1: has shown the outline | summary of construction of the ground improvement construction method by one Embodiment of this invention. As can be seen from FIG. 1, according to the ground improvement method according to the embodiment of the present invention, the improved body 10 (region where the ground is cut and mixed with the improved material) is formed. As shown by the dotted line in FIG. 1, even if a plurality of improved bodies 10 are formed, since the cross section of the improved body 10 is a square, the ground improvement points do not overlap as in the prior art of FIG. 15. . Further, it is possible to solve the problem of remaining unimproved areas as in the prior art shown in FIG.
[0019]
In FIG. 1, reference numeral 20 denotes a monitor, and jets J1, J2, and J3 including a ground improvement material are ejected from the monitor 20. The ground to be improved is cut by jets J1 and J2, and mixed with the ground improvement material by J3. Further, in FIG. 1, a dotted line TL indicates a locus of a jet injection nozzle provided on the monitor 20, and a symbol L indicates an arrival distance of the jets J1, J2, and J3.
[0020]
In the illustrated embodiment, the jets (J1, J2) for cutting the ground use cross jets so that the reach distance L can be controlled with high accuracy.
[0021]
An example of the structure of the monitor 20 and swivel 21 is shown in FIG. In FIG. 2, the monitor 20 connected to the rod 22 includes a disk 24 that rotates at the same angular velocity as the rod 22, and a pipe 28 (a member provided with a nozzle) that can rotate at an angular velocity different from the disk 24. It is configured as a so-called turntable. A swivel 21 is connected to the upper portion of the monitor 20, and the swivel 21 rotates at the same angular velocity as that of the rod 22, that is, at an angular velocity different from that of the monitor 20. And the like are supplied to the monitor 20.
[0022]
As a method of rotating the rod 22 and the monitor 20 at different angular velocities, it is possible to rotate the rod 22 and the monitor 20 independently of each other. However, FIG. 2 illustrates a method of rotating using a gear, The example will be described below.
[0023]
A first gear 30 that rotates integrally with the rod 22 and the disk 24 and a second gear 32 that rotates integrally with the pipe 28 and meshes with the gear 30 are provided inside the disk 24. ing. In the illustrated embodiment, between the number of teeth T30 of the first gear 30 and the number of teeth T32 of the second gear 32,
T30: T32 = 1: 3 (1)
A relationship exists. Therefore, in the monitor 20, the disk 24 rotates three times while the pipe 28 rotates once.
[0024]
Here, nozzles N1 and N2 are provided on the pipe 28, and jets J1 and J2 for cutting the ground are respectively ejected from the nozzles N1 and N2. As described above, the jets J1 and J2 constitute a cross jet. In addition, a nozzle N3 is provided at a lower portion of the nozzle N2 in a direction opposite to the nozzles N1 and N2, and a ground improvement material is sprayed from the nozzle N3.
[0025]
As a fluid constituting the jets J1 and J2 for cutting the ground, for example, high-pressure water or the like is used. Here, it is also possible to configure the jets J1 and J2 with a ground improvement material and to cut the ground with the ground improvement material.
[0026]
Next, the operation of the illustrated embodiment will be described with reference to FIGS. In FIGS. 3 to 14, jets J <b> 1 and J <b> 2 constituting the intersecting jet are represented by a single arrow J, and nozzles N <b> 1 and N <b> 2 are also represented by a point N to simplify the illustration.
[0027]
In the following description, the term “revolution” means that the pipe 28 moves on a circular locus as indicated by the dotted line TL in FIG. 1 according to the rotation of the disk 24 shown in FIG. Further, the term “spinning” means that the pipe 28 itself rotates or the nozzles N1 and N2 (nozzles N) attached to the pipe 28 rotate and move according to the rotation of the pipe 28 (moves on the locus TL). is doing. Here, as described above, the disk 24 rotates three times while the pipe 28 makes one rotation. Therefore, according to the illustrated embodiment, the “revolution” rotation number is three times the “spinning” rotation number.
[0028]
In FIG. 3, which is a cross-sectional view schematically showing one process of forming the improved body 10 having a square cross section, if the radius dimension of the circle formed by the trajectory (revolution trajectory) TL of the nozzle N is “r”, the nozzle The coordinates (x, y) of the initial position of N (the position shown in FIG. 3) are (r, 0). When generalized, the following equations (2), (3)
It becomes as follows.
[0029]
x = r cos ωt (2)
y = rsinωt (3)
In the equations (2) and (3), the symbol ω is the revolution angular velocity of the nozzle N.
[0030]
In the initial position shown in FIG. 3, the jet J from the nozzle N is ejected leftward on the X axis, and the tip thereof is indicated by the symbol J-E.
[0031]
Next, the revolution trajectory of the nozzle N will be described with reference to FIG. In FIG. 4, the length of the square cross section of the improved body 10 is indicated by a symbol a. And in the following explanation:
The term “square 10” means a square having a side length of a.
[0032]
The revolution trajectory of the nozzle N described in FIG. 3 is the normal trajectory when the regular triangle whose one side is a is always inscribed in the square 10 (the square whose one side is a). Matches the locus of the center of gravity of the triangle. In other words, the center of gravity of the equilateral triangle FGH with the tip position F of the jet JS from the nozzle N at the position N0 as one vertex and inscribed in the square 10 coincides with the position N0. Then, the center of gravity of the equilateral triangle KNM having the tip K of the jet J-G ejected from the nozzle at the position NG (the position K is also one point on the side of the square 10) as one vertex and inscribed in the square 10 is , Coincides with the position NG.
[0033]
Both the positions N0 and NG are points on the locus TL. That is, the locus of the center of gravity of the equilateral triangle inscribed in the square 10 is a circle having a radius of the dimension r and concentric with the center of the square 10.
[0034]
Next, the radius r of the trajectory TL will be considered. Considering the equilateral triangle FGH in FIG. 4, the reach distance L of the jet JS ejected from the position N0 is equal to the distance from the vertex to the center of gravity in the equilateral triangle of one side length a.
L = a / 3 ^1/2 (4)
It is expressed by the following mathematical formula. here,
a = 2 (Lr) = 2L-2r
If the above equation (4) is substituted into this equation,
a = 2 (a / 3 ^1/2 ) -2r
It becomes. If this is rearranged about r, then r = {(1/3 ^1/2 ) − (1/2)} a (5)
It becomes. That is, if the length of one side of the improved body (having a square cross section) to be created is determined, the radius dimension r of the revolution trajectory TL of the nozzle N is the same as the dimension r in FIG. Is determined.
[0035]
Here, in the illustrated embodiment, if the outer periphery of the square (improved body) 10 is set so that the tip J-E (see FIG. 3) of the jet makes one round in 20 seconds, for example, the nozzle N If the rotation speed is π / 10 (= 2π / 20: rad / sec), the revolution angular velocity ω of the nozzle N in the equations (2) and (3) is three times that, so that 3π / 10 (rad / sec).
[0036]
In FIG. 3 again, the initial coordinates of the jet tip position J-E (in other words, the coordinates of the symbol F in FIG. 4) are (−a / 2, 0). Then, referring also to FIG. 4, when the coordinates (X, Y) of the jet tip position J-E are generalized,
X = x + (a / 3 ^1/2 ) cos (ωt / 3) (6)
Y = y− (a / 3 ^1/2 ) sin (ωt / 3) (7)
It becomes. In other words, the above formulas (6) and (7) are mathematical expressions that generalize the trajectory of the rotation of the nozzle N (and the jet J ejected therefrom), that is, the trajectory of cutting and mixing by the jet J. Will be shown.
[0037]
5 to 14 illustrate the progress of cutting and mixing by the jet J represented by the above equations (6) and (7). 5-14, the code | symbol (theta) has shown the angle which the nozzle N revolved,
θ = ωt.
[0038]
FIG. 5 shows a state in which the nozzle N (or the pipe 28) has revolved by π / 4 (rad) in the counterclockwise direction with respect to the position (initial position) shown in FIG. Since the nozzle N rotates at an angular velocity that is 1/3 of the revolution movement, the jet J ejected from the nozzle N is not parallel to the X axis, and is an angle as shown in FIG. 5 (rotation angle by rotation). have. Then, the jet J also moves due to the revolution and rotation of the nozzle N, and the tip J-E moves from the position F of the jet tip at the initial position (same as the vertex F in FIG. 4) to the position shown in FIG. . As a result, the hatched area in FIG. 5 is cut and mixed with the ground improvement material. Here, the cross-sectional shape of the improved region is a cross-sectional shape that could not be formed by a conventional improved body having a circular cross-section.
[0039]
At this time, in the cut and improved region (the region indicated by hatching), the line segment connecting the point F and the point J-E is a straight line parallel to the Y axis. In other words, the tip of the jet J has moved upward in the figure in parallel with the Y axis.
[0040]
FIG. 6 shows a state in which the nozzle N has revolved by π / 2 in the left rotation direction with respect to the initial position. In addition, the code | symbol TL has shown the revolution locus. Even at this stage, the line segment connecting the point F and the point J-E is a straight line parallel to the Y axis. For simplification of illustration, the improved region is not hatched in FIGS.
[0041]
FIG. 7 shows a state in which the nozzle N has revolved by π (rad) in the left rotation direction with respect to the initial position. At this stage, the tip J-E of the jet J moves in parallel to the Y axis and then moves to the right in the drawing in parallel to the X axis. In the stage shown in FIG. 8, that is, the stage where the nozzle N revolves by 5π / 4 with respect to the initial position, the tip J-E of the jet J further moves in the right direction in the drawing parallel to the X axis. . When the nozzle N revolves by 2π (rad) (in other words, when the nozzle N makes one revolution on the revolution locus TL), the tip J-E of the jet J reaches a position as shown in FIG.
[0042]
FIG. 10 shows a state in which the nozzle N has revolved by 11π / 4 with respect to the initial position. At this stage, the tip J-E of the jet J does not move in parallel with the X axis, but moves downward in the figure in parallel with the Y axis. In the stage shown in FIG. 11, that is, the stage where the nozzle N revolves by 13π / 4 with respect to the initial position, the tip J-E of the jet J further moves downward in the drawing parallel to the Y axis.
[0043]
FIG. 12 shows a state where the nozzle N has revolved by 17π / 4 with respect to the initial position. At this stage, the tip J-E of the jet J does not move in parallel with the Y axis, but moves in the left direction in the drawing in parallel with the X axis.
[0044]
Further, at the stage shown in FIG. 13, the nozzle N revolves by 11π / 2 with respect to the initial position, and the tip J-E of the jet J does not move parallel to the X axis, but parallel to the Y axis. It moves to the upper side in the figure. When the nozzle N revolves by 6π with respect to the initial position, that is, when the nozzle N rotates three times on the revolution locus TL, the tip J-E of the jet J returns to the initial position F (that is, performs one rotation). As shown at 14, the cutting of the area having a square cross section and the mixing with the ground improvement material are performed.
[0045]
Therefore, if the rod 22 (FIG. 2) is rotated and pulled up to the ground side as in a normal grouting method, an improved body having a square cross section is created in the ground. Then, if the cutting of the boring rod in the initial stage of the ground improvement method is performed at a position separated by a dimension a from the boring rod (not shown) at the time of the adjacent improvement body construction, as shown in FIG. The ground can be improved over a wide area without generating an area.
[0046]
5 to 14, the revolution direction of the nozzle N is the left rotation direction, and the rotation direction of the nozzle N is the right rotation direction. However, the rod 22 and the disks 24 and 26 in FIG. Since it is common, it is preferable to set the revolution direction to the right rotation direction and the rotation direction to the left rotation direction. 5-14, the corners of the square 10 are slightly rounded, but the difference between the right-angled corners and the rounded corners is negligible in actual ground improvement methods. Is a small thing.
[0047]
In the illustrated embodiment, an improved body having a square cross section is created. However, if the rotational speed ratio and dimensions between the disk 24 and the pipe 28 are appropriately set, the improved cross section is a noncircular closed shape, for example, a rectangular cross section. It is also possible to create an improved body having The configuration of the monitor 20 is not limited to the turntable shown in FIG. The structure of the monitor 20 can be applied if the rotation and revolution of the pipe can be performed at a predetermined rotation ratio (angular velocity ratio).
[0048]
In the illustrated embodiment, since the disk 24 rotates exactly three times while the pipe 28 rotates once, the ratio between the angular velocity at which the nozzle revolves and the angular velocity at which the pipe (the member provided with the nozzle) rotates is also accurate. 3: 1. However, it is added that the technical scope of the present invention does not include only when the ratio is exactly 3: 1, but is approximately 3: 1 within the technical scope of the present invention.
[0049]
【The invention's effect】
The effects of the present invention described above are listed below.
[0050]
(1) When an improved body is created over a plurality of locations, a region that is improved in a redundant manner (overlap region) does not occur.
(2) The amount of ground improvement material used is saved.
(3) Since the amount of industrial waste including ground improvement materials is reduced, industrial waste disposal costs can be saved.
(4) It can be implemented with a simple mechanism, and the assembly cost and construction cost are reduced, and the labor spent on the ground improvement method can be saved.
(5) Since the cross-sectional shape of the improved body can be changed by simple improvement, the applicable range is extremely wide.
[Brief description of the drawings]
FIG. 1 is a plan view showing an outline of construction of a ground improvement method according to an embodiment of the present invention.
FIG. 2 is a side view showing an example of a monitor used for implementing the present invention.
FIG. 3 is a cross-sectional view schematically showing one process of improvement body formation.
FIG. 4 is a cross-sectional view schematically showing the principle of making the cross-sectional shape of the improved body a square.
FIG. 5 is a cross-sectional view schematically showing one process of cutting and mixing the ground.
FIG. 6 is a cross-sectional view schematically showing one process of cutting and mixing the ground.
FIG. 7 is a cross-sectional view schematically showing one process of cutting and mixing the ground.
FIG. 8 is a cross-sectional view schematically showing one process of cutting and mixing the ground.
FIG. 9 is a cross-sectional view schematically showing one process of cutting and mixing the ground.
FIG. 10 is a cross-sectional view schematically showing one process of cutting and mixing the ground.
FIG. 11 is a cross-sectional view schematically showing one process of cutting and mixing the ground.
FIG. 12 is a cross-sectional view schematically showing one process of cutting and mixing the ground.
FIG. 13 is a cross-sectional view schematically showing one process of cutting and mixing the ground.
FIG. 14 is a cross-sectional view schematically showing one process of cutting and mixing the ground.
FIG. 15 is a plan view for explaining problems of a conventional improved construction method.
FIG. 16 is a plan view for explaining a problem in another conventional improved construction method.
[Explanation of symbols]
1, 2, 3, 4, 10 ... improved body 20 ... monitor 21 ... swivel J, J1, J2, J3 ... jet TL ... revolution trajectory L of nozzle ... jet reach distance 22 ... Rod 24 ... Disk 28 ... Pipe 30, 32 ... Gear N, N1, N2, N3 ... Nozzle r ... Radial dimension a of nozzle revolution trajectory a ... Square 1 Side length JE ... Jet tip position

Claims (2)

 Inserting the rod provided with the monitor into the borehole cut in the ground to be improved, and spraying the fluid for cutting the ground from the nozzle provided in the monitor or spraying the ground improvement material, A jet injection step of mixing the cutting and the improvement material, and a step of pulling up the rod while rotating the rod. In the jet injection step, the cross-sectional shape of the region where the ground is cut and mixed with the improvement material is noncircular. In the jet injection step, the nozzle provided in the monitor revolves around the central axis of the rod, and the member provided with the nozzle itself rotates in the jet injection step. The ground improvement method characterized in that the angular velocity at which the nozzle revolves at the same time is different from the angular velocity at which the member provided with the nozzle rotates.  The cross-sectional shape of the area where the ground is cut and mixed with the improved material is square, and the ratio of the angular velocity at which the nozzle revolves to the angular velocity at which the member provided with the nozzle rotates is approximately 3: 1. Ground improvement method.

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