Soil improvement method and soil improvement device using mechanical stirring deep mixing treatment method

Abstract

To provide an all-directional ground improvement construction method and device capable of constructing a ground improvement pile and a ground improvement body having a desired cross-sectional shape in all directions such as diameter expansion in the ground and a ground improvement bent in the ground with excellent workability at a low cost.SOLUTION: An excavation stirring device 6 is installed at the lower end of a rotary device which is constituted by installing a vertical rotary body 3 having a vertical part connected to a horizontal shaft part and freely rotatable in a vertical surface on the lower end of a horizontal rotary body having a horizontal part freely rotatable in a horizontal surface, and the upper end of the rotary device is attached to the lower end of a rod 1. Vertical posture holding members 15, 25, and 35 long in the horizontal direction for holding the vertical posture of the rod 1 are provided on the upper surface part 33 of the rotary device or the rod 1, and the excavation stirring device 6 is inclined in a desired direction S of a vertical plane by the rotary device and rotated in a desired direction of a horizontal plane to perform stirring deep layer mixing treatment as necessary, and a ground improvement pile A or a ground improvement body B having a desired shape is created in a desired range of all directions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ground improvement method and a ground improvement device, and more specifically to a ground improvement method and a ground improvement device suitable for the method, which uses a mechanical mixing and deep mixing treatment method to improve the original ground within a desired range by mixing and stirring cement-based stabilizers and in-situ soil using a treatment machine to create ground improvement piles or ground improvement bodies, and solidify and improve the soft original ground. In this specification, the term "ground improvement pile" refers to not only vertical straight piles with a circular cross section, but also nodular piles or piles with special shapes formed by expanding or tilting a portion of them (irregular piles), and the term "ground improvement body" refers to a wall-like structure formed by constructing the ground improvement piles continuously in one direction. [Background technology]

[0002] The cross section of the ground improvement piles constructed using the mechanical deep mixing method is circular and remains constant in the depth direction. For example, in the case of liquefaction countermeasures using the lattice-type ground improvement method, the generated stress is most severe in the deepest parts, but because the cross section cannot be changed in the depth direction, it is not possible to construct a wall with a large cross section (expanded diameter) underground, as shown in Figure 9A. To increase the cross-section only in the deeper areas, two rows of improved piles would be required, but this would require dry-driving in the shallower areas as well, which is uneconomical. Although the compressive strength of the soil improvement body is high, the tensile strength can only be expected to be about 10–15% of the compressive strength. Furthermore, because there is an upper limit to tensile strength, increasing the compressive strength does not increase the allowable tensile stress. When tensile stress becomes critical, the only solution is to increase the cross-section, which is uneconomical. In such cases, constructing a cross-section with ribs, as shown in Figure 9B, would eliminate the need to drive extra improved piles, leading to cost savings. Furthermore, if mechanically improved piles could be installed and their direction changed underground, as shown in Figure 9C, they could be used to seismically reinforce existing structures.

[0003] On the other hand, when using the jet mixing method, it is possible to change the cross section underground by changing the cement milk discharge pressure and the rotation speed of the rod. However, with the jet mixing method, there is no guarantee that the improved pile will have the desired shape underground, so the reliability of the construction is low. In contrast, with mechanical improvement, the area where the mixing blade passes is reliably improved, so the construction is highly reliable in terms of the finished shape.

[0004] For example, the ground improvement method described in Patent Document 1 below, as shown in Figures 1 to 4 of that document, is a soft ground improvement method using an excavation and mixing device equipped with an agitator 3 capable of excavating and mixing the ground. This method involves drilling holes with the agitator 3 closed down to the soft ground 2 that needs improvement (Figure 1), then opening the agitator 3 a predetermined angle (Figure 2) to drill holes in the ground from the top to the bottom of the soft ground 2 excluding the layer 1 that does not need improvement, and alternately repeating a drilling step and a lifting step in which the agitator 3 is opened a further predetermined angle or fully opened (Figure 3) and pulled up while rotating to drill holes. The soft ground improvement method then involves rotating the agitator 3 while discharging improvement material into the soft ground 2, improving the ground, and creating an improved body 4 up to the top of the soft ground 2 that needs improvement (Figure 4).

[0005] Furthermore, Patent Document 2 discloses a foundation ground boring device, as shown in FIG. 1 of the same document 2, in which the overall shape is formed into a roughly conical shape, a pre-digging blade 4 of an appropriate shape is attached to the tip, and a spiral blade 5 is integrally formed on the top of the auger head 3, and a spiral convex portion 2 is attached integrally to the periphery of the casing 1 by means of a hinge 6 or the like, with one part of the auger head 3 as a support shaft and the other part being a movable rod such as a hydraulic jack 7, which is extended and retracted so that the entire auger head 3 can be bent and expanded at a certain inclination angle relative to the axis of the casing 1 (see left in FIG. 1). This drilling device is used to rotary excavate the ground, and when the excavation reaches a predetermined depth, the auger head 3 is bent and expanded to the required hole diameter d width (right side of Figure 1), and by rotating and excavating the ground with the auger head 3 bending and expanding, a large diameter bulbous hole is excavated in the ground, and a ground layer with strong bearing capacity is constructed, as described in this ground improvement method.

[0006] The construction method according to Patent Document 1 mentioned above can only be used for circular cross sections, so it is difficult to construct a cross section with ribs on the wall as mentioned above (FIG. 9B), and there is also a limit to the expansion width. In addition, the boring equipment of Patent Document 2 uses a hinge 6 at the bottom of the casing 1 as a support shaft for part of the auger head 3, and the other part is extended and retracted by a movable rod such as a hydraulic jack 7, and only the auger head 3 at the tip is bent to a certain range of inclination angles relative to the axis of the casing 1, so the entire casing 1 is not designed to be inclined greatly. Therefore, although it is possible to create a large bulbous section directly below a vertical pile hole, it is not possible to create an improved pile at a desired oblique angle as shown in Figure 9C. Construction of a cross section with ribs is also difficult.

[0007] In view of the problems in Patent Documents 1 and 2, the present applicant has developed and patented a ground improvement method using a mechanical mixing and deep mixing method, which is capable of creating ground improvement piles or ground improvement bodies with desired cross-sectional shapes, such as those that expand underground or bend underground, by rotating an excavating and mixing device at a desired angle and direction, as shown in Patent Document 3. The invention described in Patent Document 3 also makes it possible to realize a ground improvement method using a mechanical mixing and deep mixing method and a ground improvement device suitable for the method, which is suitable for construction in narrow spaces (narrow areas), enables construction under existing structures, and is highly convenient as it can be applied to seismic reinforcement of existing structures, etc. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 3697348 [Patent Document 2] Japanese Patent Application Publication No. 7-71033 [Patent Document 3] Patent No. 6397147 Summary of the Invention [Problem to be solved by the invention]

[0009] In the ground improvement method and soil improvement device using the mechanical mixing deep mixing method described in Patent Document 3, which rotates the hydraulic auger (excavation and mixing device) 6 itself without rotating the rod 1, a vertical rotor 3 allows free vertical rotation, or a horizontal rotor 4 allows free horizontal rotation. During ground improvement, stabilizers (e.g., cement slurry) and the improved ground are mixed and stirred to form a soft, unsolidified soil. Therefore, a reaction force is required to stably rotate the hydraulic auger 6, especially during vertical rotation by the vertical rotor 3. Without this reaction force, the rod 1 becomes more likely to misalign with its axis as it extends (deepens), making it difficult to maintain its vertical position with the restraint provided by commonly used anti-vibration devices. This misalignment of the rod 1 complicates control of the hydraulic auger 6 and also poses concerns about the quality of the improved soil, making it an issue that requires improvement.

[0010] If it were possible to prevent (suppress) misalignment of the rod 1, i.e., if it were possible to maintain the vertical position of the rod 1, it would be possible to control the hydraulic auger 6 in a stable state and with good control, and it would also be possible to construct improved ground of excellent quality, so it would clearly be even more beneficial.

[0011] The present invention was devised in consideration of the problems of the background art described above, and its purpose is to provide a ground improvement method using a mechanical stirring deep mixing treatment method that is excellent in workability, economy, and quality, and a ground improvement device suitable for the method, which not only enables the creation of ground improvement piles or ground improvement bodies of desired cross-sectional shapes, such as expansion of the diameter underground or bent underground, by mechanical ground improvement performed by rotating an excavating and mixing device at a desired angle and direction, but also prevents (suppresses) misalignment of the rod and can maintain the vertical position of the rod even during vertical rotation by the vertical rotor, and by maintaining the vertical position of the rod, good ground improvement work can be performed and high-quality improved ground can be achieved. [Means for solving the problem]

[0012] As a means for solving the above problems, the ground improvement method using the mechanical stirring deep mixing method according to the invention described in claim 1 is a mechanical stirring deep mixing method in which an excavation mixing device attached to the lower end of a rod via a rotating device is penetrated into the soft ground while excavating the soft ground, and a stabilizing material is discharged by penetration discharge or pull-up discharge, and the stabilizing material is mixed and mixed with the in-situ soil to create a ground improvement pile or a ground improvement body, The rotating device is a vertical rotating body having a horizontal shaft portion and left and right vertical portions connected to both ends of the horizontal shaft portion and rotatable on a vertical plane, the left and right vertical portions being configured to rotate 90 degrees left and right on the vertical plane, within a maximum range of 180 degrees, the upper end of the vertical rotating body is connected to the lower end of the rod, and the left and right vertical portions of the vertical rotating body are connected to the excavation and mixing device, and a horizontally long vertical position holding member for holding the vertical position of the rod is provided on the upper surface of the rotating device or the rod, The left and right vertical parts of the vertical rotor allow the excavation and mixing device to be tilted in the desired direction in the vertical plane within the maximum rotation range of 180 degrees, performing deep mixing and mixing processing and creating ground improvement piles or ground improvement bodies of the desired shape within the desired range.

[0013] The ground improvement method using the mechanical stirring deep mixing method according to the invention described in claim 2 is a mechanical stirring deep mixing method in which an excavation and mixing device attached to the lower end of a rod via a rotating device is penetrated into the soft ground while excavating the soft ground, and a stabilizing material is discharged by penetration discharge or pull-up discharge, and the stabilizer is mixed and mixed with the in-situ soil to create a ground improvement pile or a ground improvement body, the rotation device is formed by combining a vertical rotation body and a horizontal rotation body, and a vertical position holding member that is long in the horizontal direction is provided on an upper surface of the rotation device or on the rod to hold the rod in a vertical position, The vertical rotor includes a horizontal shaft portion and left and right vertical portions connected to both ends of the horizontal shaft portion and rotatable on a vertical plane. The left and right vertical portions rotate by 90 degrees left and right on the vertical plane, and can rotate up to 18 degrees. 0 degrees, the upper end of the vertical rotating body is connected to the horizontal rotating body, and the left and right vertical portions of the vertical rotating body are connected to the excavation and stirring device; the horizontal rotor includes a vertical shaft portion and a horizontal portion pivotally supported on the vertical shaft portion and rotatable within a range of 360 degrees on a horizontal plane, the horizontal portion of the horizontal rotor being connected to the vertical rotor, and the vertical shaft portion of the horizontal rotor being connected to a lower end of the rod, The left and right vertical parts of the vertical rotor of the rotating device tilt the excavation and mixing device in the desired direction on a vertical plane within the maximum rotation range of 180 degrees, and the horizontal part of the horizontal rotor of the rotating device rotates the excavation and mixing device in the desired direction on a horizontal plane, thereby performing a deep mixing process and creating ground improvement piles or ground improvement bodies of the desired shape within the desired range.

[0014] The invention described in claim 3 is characterized in that, in a ground improvement method using the mechanical stirring deep mixing treatment method described in claim 1 or 2, the vertical posture maintaining member is formed so that the cross-sectional shape of the rod is rectangular in plan view, which improves cross-sectional rigidity, instead of a horizontally long vertical posture maintaining member provided on the upper surface of the rotating device or the rod.

[0015] The ground improvement method according to the invention described in claim 4 is a ground improvement device used in a mechanical mixing and deep mixing treatment method in which the device penetrates into the soft ground while excavating the soft ground, discharges stabilizing material by penetration discharge or uplift discharge, and mixes and mixes the material with the in-situ soil to create ground improvement piles or ground improvement bodies, The ground improvement device comprises a rotation device and an excavation and stirring device, The rotating device is a vertical rotating body having a horizontal shaft portion and left and right vertical portions connected to both ends of the horizontal shaft portion and rotatable on a vertical plane, the left and right vertical portions being configured to rotate 90 degrees left and right on the vertical plane, and to rotate within a maximum range of 180 degrees, the excavating and mixing device is connected to the left and right vertical portions of the vertical rotating body, the upper end of the vertical rotating body is attachable to the lower end of a rod, and a horizontally long vertical position holding member for holding the vertical position of the rod is provided on the upper surface of the rotating device or the rod, The left and right vertical parts of the vertical rotor allow the excavation and mixing device to be tilted in the desired direction in the vertical plane within the maximum rotation range of 180 degrees, and the configuration is characterized in that ground improvement piles or ground improvement bodies of the desired shape are constructed within the desired range.

[0016] The ground improvement method according to the invention described in claim 5 is a ground improvement device used in a mechanical mixing and deep mixing treatment method in which the device penetrates into the soft ground while excavating the soft ground, discharges stabilizing material by penetration discharge or uplift discharge, and mixes and mixes the material with the in-situ soil to create ground improvement piles or ground improvement bodies, The ground improvement device comprises a rotating device and an excavating and stirring device, and the rotating device comprises a combination of a vertical rotating body and a horizontal rotating body; The vertical rotor includes a horizontal shaft portion and left and right vertical portions connected to both ends of the horizontal shaft portion and rotatable on a vertical plane, and the left and right vertical portions rotate 90 degrees left and right on the vertical plane, rotating within a maximum range of 180 degrees. The upper end of the vertical rotor is connected to the horizontal rotor, and the excavation and stirring device is connected to the left and right vertical portions of the vertical rotor, the horizontal rotating body comprises a vertical shaft portion and a horizontal portion pivotally supported on the vertical shaft portion and rotatable within a range of 360 degrees on a horizontal plane, the horizontal portion of the horizontal rotating body is connected to the vertical rotating body, the vertical shaft portion of the horizontal rotating body is attachable to the lower end of a rod, and a vertical position holding member that is long in the horizontal direction is provided on the upper surface portion of the rotating device or on the rod to hold the rod in a vertical position; The left and right vertical parts of the vertical rotor of the rotating device tilt the excavating and mixing device in the desired direction on a vertical plane within the maximum rotation range of 180 degrees, and the horizontal part of the horizontal rotor of the rotating device rotates the excavating and mixing device in the desired direction on a horizontal plane, thereby constructing ground improvement piles or ground improvement bodies of the desired shape within the desired range.

[0017] The ground improvement method according to the invention described in claim 6 is characterized in that, in the ground improvement device described in claim 4 or 5, the excavation and mixing device is a hydraulic auger or an electric auger. .

[0018] The invention described in claim 7 is characterized in that, in the ground improvement device described in claim 4 or 5, the vertical posture maintaining member is detachably attached to the upper surface of the rotating device or the rod.

[0019] The invention described in claim 8 is characterized in that, in the ground improvement device described in claim 4 or 5, the vertical posture maintaining member comprises two horizontally long parallel rod-shaped members and two vertically long connecting plate members that connect the two end portions of the two parallel rod-shaped members to form a frame, and the two parallel rod-shaped members are arranged so as to sandwich the rod when viewed from a planar direction.

[0020] The invention as set forth in claim 9 is characterized in that, in the soil improvement device as set forth in claim 8, the rod-shaped members are H-shaped steel beams with their webs oriented vertically.

[0021] The invention described in claim 10 is characterized in that, in the ground improvement device described in claim 4 or 5, the vertical posture maintaining member consists of a pair of left and right vertical posture maintaining member pieces each having a semi-cylindrical flanged joint portion that connects to surround the rod and a main body portion, the main body portion consisting of a plurality of horizontally long parallel plate-shaped members and a blocking member that connects one end of the plate-shaped members, and the other end of the plate-shaped members is connected to the joint portion.

[0022] The invention described in claim 11 is characterized in that, in the ground improvement device described in claim 10, the joint portion and the blocking member are formed so that the horizontal length can be adjusted by adding, as necessary, a component unit consisting of a plurality of horizontally long parallel plate-like members and connecting plates connecting both ends of the plate-like members, instead of the plurality of horizontally long parallel plate-like members.

[0023] The invention described in claim 12 is characterized in that, in the ground improvement device described in claim 4 or 5, the vertical posture maintaining member is formed such that, instead of a horizontally long vertical posture maintaining member provided on the upper surface of the rotating device or the rod, the cross-sectional shape of the rod is formed into a rectangular shape in a plan view, which improves cross-sectional rigidity. [Effects of the Invention]

[0024] The ground improvement method and ground improvement device using the mechanical mixing deep mixing method of the present invention allows the excavation and mixing device to be tilted and rotated in the desired direction using a rotation device, making it possible to efficiently construct ground improvement piles (ground improvement bodies) with any cross-sectional shape, contributing to cost reduction.For example, it is possible to rationally realize construction of lattice walls for lattice improvement and under existing structures, and is also suitable for construction in narrow areas (narrow spaces), and can be applied to seismic reinforcement of existing structures, making it extremely convenient. Furthermore, by providing the vertical position maintaining member, misalignment of the rod can be prevented (suppressed) even during vertical rotation by the vertical rotor, and the vertical position of the rod can be maintained. By maintaining the vertical position of the rod, good ground improvement work can be performed and high-quality improved ground can be achieved. Therefore, a ground improvement method using a high-quality mechanical stirring deep mixing method and a ground improvement device suitable for this can be realized. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic diagram showing the key steps of a ground improvement method using a mechanical stirring deep mixing treatment method using the ground improvement device of the present invention. [Figure 2] FIG. 2 is an overall view showing a different embodiment of FIG. 1. [Figure 3] A is a plan view showing a so-called long type ground improvement device, B is a front view of the same, and C is an expanded view of the same. [Figure 4] FIG. 1A is an elevational view showing how to use a so-called short-type ground improvement device, and FIG. 1B is a perspective view showing a different rotation device that is installed on the ground improvement device of FIG. [Figure 5]1A to 1C are explanatory diagrams that schematically show the construction procedure of the ground improvement method. [Figure 6] 5A and 5B are explanatory views schematically showing steps subsequent to FIG. [Figure 7] This is an explanatory diagram showing the outline of the construction procedure for an inclined ground improvement body. [Figure 8] 1A to 1C are explanatory diagrams that schematically show the construction procedure for a ground improvement body provided with ribs. [Figure 9] 1A to 1C are explanatory diagrams showing schematic examples of various improved piles or improved bodies constructed by the ground improvement method. [Figure 10] 10 is an elevational view showing another embodiment of the drilling and stirring device. FIG. [Figure 11] 1 is an elevational view showing a main part of a ground improvement device according to the present invention. [Figure 12] 12A is a front view showing a vertical attitude maintaining member of the soil improvement device of FIG. 11, and FIG. 12B is a plan view of the same. [Figure 13] 12 is a construction drawing for confirming the effect of the ground improvement device equipped with the vertical attitude maintaining member according to FIG. 11. [Figure 14] 12 is a construction drawing for confirming the effect of the ground improvement device equipped with the vertical attitude maintaining member according to FIG. 11. [Figure 15] 13 is an elevation view showing a ground improvement device equipped with a vertical attitude maintaining member different from the vertical attitude maintaining member shown in FIG. 12. [Figure 16] FIG. 16 is a plan view of the soil improvement device according to FIG. [Figure 17] FIG. 16 is a side view of the soil improvement device according to FIG. [Figure 18] FIG. 16 is a plan view showing a ground improvement device equipped with a vertical attitude maintaining member different from the vertical attitude maintaining member shown in FIGS. 12 and 15. [Figure 19] FIG. 19 is a plan view of the vertical attitude maintaining member shown in FIG. 18. [Figure 20] 19A to 19C are elevation views showing variations of the vertical attitude maintaining member shown in FIG. 18. [Figure 21] 10A and 10B are explanatory diagrams showing different vertical posture maintaining members. BEST MODE FOR CARRYING OUT THE INVENTION

[0026] Next, an embodiment of a ground improvement method using the mechanical stirring deep mixing treatment method according to the present invention and a ground improvement device suitable for the method will be described with reference to the drawings. This ground improvement method is suitably carried out in a mechanical mixing deep mixing treatment method in which an excavating and mixing device 6 appropriately attached to the lower end of a rod 1 is penetrated into the soft ground while excavating the soft ground 2, and a stabilizer such as cement milk (not shown) is discharged by penetration discharge or pull-up discharge, which is then stirred and mixed with the in-situ soil to create ground improvement piles A and ground improvement bodies B within the desired range.

[0027] Figures 1 and 2 are diagrams showing the main steps of the ground improvement method using the ground improvement device. The configuration of the ground improvement device will be explained mainly with reference to Figure 3. This ground improvement device has a vertical rotor 3, which serves as a rotation device, installed above an excavating and stirring device 6. The vertical rotor 3 is basically the type shown in Figures 3 and 4A (hereinafter sometimes referred to as a two-dimensional type). This two-dimensional type vertical rotor 3 is connected to a horizontal shaft 30, and left and right vertical sections 31, 31 are supported on both sides of the horizontal shaft 30 via bearings that can rotate freely in a vertical plane, and are each supported by vertically arranged support sections 32, 32. These left and right vertical sections 31, 31 can each rotate 90 degrees left and right in a vertical plane, and can rotate at a desired angle inclined within a maximum range of 180 degrees. The lower ends of the vertical sections 31, 31 are connected to a horizontal plate-shaped lower surface 34, and the excavating and stirring device 6, which will be described later, is connected to the underside of the lower surface 34. Meanwhile, the upper ends of the support portions 32, 32 are connected to a horizontal, disk-shaped upper surface portion 33, and a shaft portion 50 protruding upward is provided in the center of the upper surface portion 33. In this embodiment, the height of the vertical rotor 3 is, for example, approximately 0.5 m. The shaft portion 50 can be freely attached to a rod 1, which will be described later (see FIG. 4A). Furthermore, a vertical position holding member 15 that is long in the horizontal direction is provided on the upper surface portion 33 (or rod 1) of the rotation device (vertical rotation body) 3 to hold the rod 1 in a vertical position.

[0028] In addition, the rotation of the type shown in FIG. 4B (hereinafter sometimes referred to as the three-dimensional type) The device 5 may also be suitably applied to a ground improvement device. That is, this ground improvement device is configured such that the upper ends of the vertical parts 31, 31 of the vertical rotor 3 are connected to the lower end of a horizontal part 41 of a horizontal rotor 4, which is supported by a vertical shaft part 40 and has a horizontal part 41 via a bearing that is rotatable on a horizontal plane. A shaft part 50 is protruded from the vertical shaft part 40 (see Fig. 4A), and the shaft part 50 allows the rotor 5 to be freely attached to the rod 1 as appropriate, just like the two-dimensional type. Therefore, with this three-dimensional type rotation device 5, the excavation and mixing device 6 described later can be tilted in a vertical plane by a maximum of 180 degrees using the vertical part 31 of the vertical rotation body 3, and can be rotated in a horizontal plane by a 360 degree range using the horizontal part 41 of the horizontal rotation body 4, and free three-dimensional ground improvement can be performed by combining these tilt angles and rotation angles.

[0029] Next, the excavating and stirring device 6 connected to the lower end of the rotating device 5 will be described. In this embodiment, the excavating and stirring device 6 is implemented as a hydraulic auger. As an example, this hydraulic auger 6 has a built-in motor and is configured to operate by receiving hydraulic pressure from a hydraulic device provided in a backhoe 7. The same implementation can also be achieved by using an electric auger instead of the hydraulic auger. Incidentally, the reference numeral 70 in FIG. 1 indicates the arm of the backhoe 7. As shown in Fig. 3, the excavating and stirring device 6 is composed of an inner cylinder 60 and an outer cylinder 61, each about 2 m high, and the inner cylinder 60 is installed on the lower surface 34 of the lower end of the rotating device 5. A stirring blade 63 is attached to the outer peripheral surface 62 of the rotating outer cylinder 61, and a long spiral drilling body 64 (about 1 m high, for example) equipped with a tip drilling bit 65 is attached to the lower end of the outer peripheral surface 62. In detail, the reference numeral 66 in the figure indicates the cement milk outlet, the reference numeral 67 indicates the intermediate cement milk outlet, the reference numeral 68 indicates the cement milk connection port which switches between normal discharge and downward discharge, and the reference numeral 69 indicates the hydraulic piping. Figure 4 shows a short type of excavating and stirring device 6 in Figure 3, in which the excavating body 64 at the tip is short (for example, approximately 40 cm in height), and the other configuration is the same as the long type in Figure 3 (detailed explanation will be omitted).

[0030] Therefore, with the above-mentioned two-dimensional type ground improvement device, as shown in Figure 1, simply by placing the upper end of the vertical rotating body (rotating device) 3 of the above-mentioned configuration at the lower end of the rod 1, the vertical rotating body 3 can be used to tilt the excavating and mixing device 6 in the desired direction S of the vertical plane as necessary, thereby constructing a ground improvement pile A of the desired shape as illustrated in Figure 9. Furthermore, with the above-mentioned ground improvement device equipped with the three-dimensional type rotation device 5, the excavating and stirring device 6 can be tilted in a desired direction S on a vertical plane by the rotation device 5 as needed, and rotated in a desired direction T on a horizontal plane, thereby creating a ground improvement body B (or a ground improvement pile A) of a desired shape within a desired range. For example, a ground improvement body B such as that shown in Figures 6 to 8 can be created. It is also possible to mount the upper end of the rotation device 5 of the ground improvement device on the lower end of the rod 1 operated by a stationary boring machine (base machine) 8 as shown in Figure 2. In addition to the stationary type, the boring machine can also be a mobile type that can run on laid rails. In particular, a mobile type that can move regularly is suitable when constructing a wall-shaped ground improvement body.

[0031] 5 to 8, an embodiment of a ground improvement method using a ground improvement device equipped with a three-dimensional type rotation device 5 will be described below. It should be noted that the procedure described below is merely one example. As shown in FIG. 5A, after inserting the hydraulic auger (excavation and mixing device) 6 into the ground almost vertically, the hydraulic auger 6 is tilted by 90 degrees in the vertical plane by the rotation device 5 (FIG. 5B). After that, as shown in Fig. 5C, the hydraulic auger 6 is rotated 360 degrees in the T direction on the horizontal plane to improve the ground, and a circular ground improvement body B is created in plan view. The horizontal rotation in the T direction can be achieved by using the horizontal rotating body 4 of the rotation device 5, but it can also be achieved by rotating the rod 1. Next, as shown in Figure 6A, the position of the hydraulic auger 6 is gradually lowered, and the ground improvement work of rotating it 360 degrees on a horizontal plane as shown in Figure 5C is repeated to create a cylindrical ground improvement body B. In this way, an improved body B with a large cross section can be created using this small-sized ground improvement device. As shown in Figure 6B, by setting the depth at which ground improvement work will be performed and the depth at which it will not be performed by rotating the work 360 degrees on the horizontal plane of Figure 5C, and then carrying out the work, it is also possible to create an improved body B that alternates between large-diameter improved sections and small-diameter improved sections.

[0032] Figure 7 shows an example of construction of an inclined ground improvement body. The rod 1 is inserted into the ground in an inclined state, and the hydraulic auger 6 is tilted by 90 degrees using the rotation device 5 (see Figures 5A and 5B). In this state, large-scale soil improvement work can be carried out on a diagonal two-dimensional cross section. Furthermore, to carry out ground improvement work on a three-dimensional cross section, the hydraulic auger 6 can be further rotated 360 degrees on the horizontal plane and carried out as shown in Figure 5B, thereby creating a large cross section of an inclined ground improvement body B. The 360 ​​degree rotation on the horizontal plane can be carried out using the rotation device 5 as described above, but it can also be carried out by rotating the rod 1.

[0033] FIG. 8 shows an example of construction in which ribs are provided on an underground wall (including a grid-type improved wall). A rod 1 (not shown) is inserted into the ground approximately vertically, and ground improvement is performed in this state (see FIG. 5A). When the rod reaches a predetermined depth, the hydraulic auger 6 is tilted 90 degrees using the rotation device 5 (see FIG. 5B) to perform ground improvement. The hydraulic auger 6 is then returned to its original approximately vertical position using the rotation device 5 to perform ground improvement. The cross section shown in FIG. 8B is cross section II in FIG. 8A, which shows ground improvement over a narrow area. The hydraulic auger 6 is then tilted 90 degrees using the rotation device 5 to perform ground improvement. The cross section shown in FIG. 8C is cross section II-II in FIG. 8A, which shows ground improvement over a wide area. In this way, by alternately performing ground improvement with the hydraulic auger 6 tilted 90 degrees using the rotation device 5 and ground improvement in an approximately vertical position, an underground wall (improved body B) with ribs C at a predetermined depth can be constructed (FIG. 8A).

[0034] Next, FIG. 11 shows an embodiment in which a soil improvement device having the above-mentioned rod 1 connection structure is provided with a horizontally long vertical position maintaining member 15 for maintaining the vertical position of the rod 1.

[0035] In the present invention, a ground improvement device rotates the hydraulic auger 6 itself without rotating the rod 1, allowing free vertical rotation using the vertical rotor 3, or free horizontal rotation using the horizontal rotor 4. During ground improvement, stabilizers (e.g., cement slurry) and the improved ground are mixed and stirred to form a soft, unsolidified soil. Therefore, a reaction force is required to stably rotate the hydraulic auger 6, especially during vertical rotation using the vertical rotor 3. Without this reaction force, the rod 1 becomes more likely to misalign as it becomes longer (deeper), making it difficult to maintain its vertical position with the restraint provided by commonly used anti-vibration devices. This misalignment of the rod 1 complicates control of the hydraulic auger 6 and also poses concerns about the quality of the improved ground, making it an issue that requires improvement. If it were possible to prevent (suppress) misalignment of the rod 1, i.e., if it were possible to maintain the vertical position of the rod 1, it would be possible to control the hydraulic auger 6 in a stable state and with good control, and it would also be possible to construct improved ground of excellent quality, so it would clearly be even more beneficial. Therefore, in the present invention, as shown in Figure 11, etc., the vertical posture maintaining member 15 was developed to prevent (suppress) misalignment of the rod 1 even during vertical rotation by the vertical rotating body 3.

[0036] 12A and 12B, the vertical posture maintaining member 15 is provided on the upper surface 33 of the rotation device 5, and includes two horizontally long parallel rod-shaped members 15a and two vertically long connecting plate members 15b that connect both ends of the two parallel rod-shaped members 15a and integrate them into a frame shape by means of welding or the like, and the two parallel rod-shaped members 15a are arranged to sandwich the rod 1 when viewed from above. Incidentally, the reference numeral 15c in the drawing denotes a metallic reinforcing member (diagonal member). Specifically, in this embodiment, an H-shaped steel beam with its web oriented vertically is used as the bar-shaped member 15a, and the rod 1 is disposed in the center of the bar-shaped member 15a. A steel plate is preferably used for the connecting plate member 15b. In this embodiment, the lower flange surface in the center of the bar-shaped member (H-shaped steel beam) 15a and the upper surface 33 of the rotation device 5 are integrated by welding, but this is not limited thereto, and a detachable structure such as bolt connection may also be used.

[0037] The size of the vertical positioning member 15 can be modified as appropriate depending on the structural design. In this embodiment, as an example only, the rod-shaped member (H-beam) 15a has a flange width of approximately 100 mm, a web height of approximately 100 mm, and a length of approximately 3850 mm. The vertically elongated connecting plate member 15b has a height (see symbol H in FIG. 12A) of approximately 600 mm, a width (see symbol W in FIG. 12B) of approximately 450 mm, and a plate thickness of approximately 22 mm. The reinforcing member (diagonal member) has a plate thickness of approximately 22 mm and a length of approximately 400 mm. For example, the vertical positioning member 15 in the illustrated example is wider than the mixing blade 63, but it can of course also be implemented with approximately the same width (length).

[0038] According to the ground improvement device equipped with this vertical posture maintaining member 15, the hydraulic auger 6 penetrates into the improved ground while excavating the soft ground 2, and a stabilizing material (e.g., cement slurry) is discharged by penetration discharge or pull-up discharge, and the vertical posture maintaining member 15 remains stationary (non-rotating) and is buried in the soft improved soil before it is stirred and mixed with the in-situ soil (improved ground) and solidified. The vertical attitude maintaining member 15, which is fully buried in the improved soil and in a stationary state, acts as a resistance member in the improved soil, preventing (suppressing) the vibration of the rod 1 and maintaining the vertical attitude of the rod 1. If the vertical attitude of the rod 1 can be maintained, the hydraulic auger 6 can be well controlled in a stable state, and ultimately improved ground of excellent quality can be achieved.

[0039] Figures 13 and 14 show examples of construction work carried out to confirm the effectiveness of the ground improvement device shown in Figures 11 and 12. Incidentally, in the ground improvement device shown in Figures 13 and 14, the anti-vibration members 16 are installed as high above the ground surface as possible compared to normal construction in order to economically and efficiently eliminate a situation in which the vertical rotation device 3 (rotation device 5) and the anti-vibration members 16 are separated and misalignment is likely to occur.

[0040] The ground improvement device shown in Figure 13 shows an example of a configuration in which the left and right vertical sections 31 are rotated 33 degrees left and right on a vertical plane by the vertical rotor 3. In this example, the excavation width and the horizontal length of the vertical positioning member 15 are approximately equal (3.894 m in this example), so both ends of the vertical positioning member 15 abut against the unimproved portion of the ground, ensuring a positive reaction force. As a result, the vertical positioning member 15 prevents the rod 1 from swinging when penetrated into the improved ground. This prevents the rod 1 from misaligning even during vertical rotation by the vertical rotor 3, confirming that good ground improvement work can be performed.

[0041] The ground improvement device shown in Figure 14 shows an example of a construction in which the vertical rotor 3 rotates the left and right vertical sections 31 45 degrees to the left and right in a vertical plane. In this example, the horizontal length of the vertical positioning member 15 (3.894 m) is shorter than the excavation width (4.540 m). In this case, the excavation width is longer (wider) than the vertical positioning member 15, so a reaction force due to the vertical positioning member 15 abutting the unimproved portion, as shown in Figure 13, cannot be expected. However, when the vertical positioning member 15 is fully embedded in the improved soil, it resists the improved soil, ensuring a reaction force, preventing the rod 1 from swinging. Therefore, as with the ground improvement device shown in Figure 13, it was confirmed that misalignment of the rod 1 can be prevented even during vertical rotation by the vertical rotor 3, enabling successful ground improvement work.

[0042] 13 and 14, it is possible to prevent (suppress) misalignment of the rod 1 and maintain the vertical position of the rod 1 even during vertical rotation by the vertical rotor 3. Because the vertical position of the rod 1 can be maintained, it is possible to effectively control the hydraulic auger 6 in a stable state, perform effective ground improvement work, and ultimately achieve improved ground of excellent quality.

[0043] 15 to 17 show an embodiment of a soil improvement device equipped with a vertical attitude maintaining member 25 that is different from the vertical attitude maintaining member 15 shown in FIGS. The vertical posture maintaining member 25 is detachably attached to the lower part of the rod 1 and consists of a pair of left and right vertical posture maintaining member pieces 25a each having a semi-cylindrical flanged (steel) joint part 26 that connects to surround the rod 1 and a main body part 27, the main body part 27 consisting of a plurality of horizontally long parallel plate-like members (steel plates) 27a and a blocking member (such as an arc-shaped steel plate in a plan view) 27b that connects one end of the plate-like members 27a, the other end of which is connected to the joint part 26. Specifically, the components (joints 26, plate-like members 27a, and closing members 27b) that make up the vertical attitude maintaining member 25 are, for example, made of metal plates (steel plates) with a thickness of about 22 mm and are joined together by joining means such as welding. The horizontal length of the vertical attitude maintaining member 25 is about 3000 mm, the horizontal length of the pair of left and right vertical attitude maintaining member pieces 25a is about 1500 mm, the height of the plate-like members (steel plates) 27a (see FIG. 15) is about 350 mm, and the height of the closing members 27b (see FIG. 15) is about 600 mm. Note that the above dimensions are merely examples and can be modified as appropriate depending on the structural design.

[0044] With the ground improvement device equipped with this vertical positioning member 25, the hydraulic auger 6 penetrates the improved ground while excavating the soft ground 2, and a stabilizer (e.g., cement slurry) is dispensed by penetration or lifting. The vertical positioning member 25 remains stationary (non-rotating) and is embedded in the soft improved soil before it is mixed with the in-situ soil (improved ground) and solidifies. The stationary vertical positioning member 25 still functions as a resistance member in the improved soil, similar to the vertical positioning member 15 shown in Figures 11 to 14, and thus prevents (suppresses) the swing of the rod 1 and maintains the vertical position of the rod 1. Maintaining the vertical position of the rod 1 allows for stable and effective control of the hydraulic auger 6, ultimately resulting in improved ground of high quality.

[0045] 18 and 19 show an embodiment of the soil improvement device equipped with a vertical attitude maintaining member 35 different from those shown in FIGS. 11 to 14 and 15 to 18. In FIGS. The vertical attitude maintaining member 35 has the following features in comparison with the vertical attitude maintaining member 25 shown in FIGS. Instead of the horizontally long, parallel plate-like members 27a, a member unit 36 ​​is formed between the joint portion 26 and the blocking member 27b. The member unit 36 ​​is made up of a plurality of horizontally long (three in the illustrated example) parallel plate-like members (steel plates) 36a and connecting plates (steel plates) 36b connecting both ends of the plate-like members 36a, which are integrated by welding. The member unit 36 ​​can be joined as needed with bolts 37 as connecting means, thereby making the horizontal length adjustable, as illustrated in the stepwise manner in Figures 20A to 20C. Incidentally, reference numeral 38 in the figures denotes a stiffener. It should be noted that the embodiment shown in Figure 20 is a variation diagram based on a similar concept, although the detailed structure differs from that shown in Figures 18 and 19.

[0046] With the ground improvement device equipped with this vertical positioning member 35, the hydraulic auger 6 penetrates the improved ground while excavating the soft ground 2, and a stabilizer (e.g., cement slurry) is dispensed by penetration or lifting. The vertical positioning member 35 remains stationary (non-rotating) and is embedded in the soft improved soil before it is mixed with the in-situ soil (improved ground) and solidifies. The stationary vertical positioning member 35 still functions as a resistance member in the improved soil, similar to the vertical positioning members 15 and 25 shown in Figures 11 to 14 and 15 to 17, and thus prevents (suppresses) the swing of the rod 1 and maintains the vertical position of the rod 1. Maintaining the vertical position of the rod 1 allows for stable and effective control of the hydraulic auger 6, ultimately resulting in improved ground of high quality.

[0047] FIG. 21 shows an embodiment of a vertical attitude maintaining member different from the above-described vertical attitude maintaining members 15, 25, and 35. In FIG. That is, the vertical posture maintaining member of Figure 21 is characterized in that, instead of the horizontally long vertical posture maintaining member 15, 25, or 35 provided on the upper surface portion 33 of the rotating device or the rod 1, the cross-sectional shape of the rod 1 is formed into a rectangular shape in a plan view which improves cross-sectional rigidity. Regarding the size of the cross-sectional shape of the rod 1, the outer diameter (φ) of the cylindrical rod 1 in Figure 1, etc. is, for example, about 267 mm, whereas the rod 1 having a rectangular shape in plan view in Figure 21 is, for example, larger than the outer diameter (φ) of the cylindrical rod 1, with a vertical dimension (symbol D) of about 600 mm, a horizontal dimension (symbol E) of about 355 mm, and a thickness of about 20 mm. 21 makes use of the feature of the present invention that the rod 1 does not rotate, and forms the cross-sectional shape of the rod 1 itself with a large resistance surface just like the vertical attitude maintaining member 15, 25, or 35, so that the entire rod 1 in the improved soil plays the role of a resistance member similar to the vertical attitude maintaining member 15, 25, or 35, thereby preventing (suppressing) the swinging of the rod 1 and maintaining the vertical attitude of the rod 1. Therefore, according to the embodiment of Fig. 21, by maintaining the vertical attitude of the rod 1, the hydraulic auger 6 can be well controlled in a stable state, and ultimately improved ground of excellent quality can be achieved. The size of the outer diameter of the rod 1 is not limited to the above dimensions and can be modified as appropriate. The portion of the rod 1 that is rectangular in plan view may be formed over the entire length of the rod 1, or may be formed only on the portion that is buried underground. The rod 1 is usually extended vertically as appropriate, and the extended portions (connection portions) are formed by forming male and female portions and joining them by conventional joining means such as pin joints, bolt joints, or screw joints.

[0048] Although the embodiments of the present invention have been described above with reference to the drawings, it should be noted that the present invention is not limited to the illustrated examples and includes the range of design modifications and application variations that would normally be made by a person skilled in the art, provided that they do not deviate from the technical concept of the present invention. For example, in the above embodiment, the horizontal shaft portion 30 and the vertical portion 31 of the vertical rotor 3 used in the two-dimensional type and three-dimensional type are joined by a (ball) bearing system, but this is not limited to this and can also be implemented by a gear system 9 as shown in Fig. 10. In this way, the configuration of the excavating and stirring device (hydraulic auger) 6 can be appropriately modified in design depending on the structural design, as shown in the illustrated examples (see Fig. 3, Fig. 10, Fig. 11, or Fig. 15), and it should be noted that the configuration of the vertical rotor 3 (rotating device 5) and the like is also not limited to the illustrated examples and can be appropriately modified in design depending on the structural design. [Explanation of symbols]

[0049] 1 rod 2 Soft ground 3 Vertical Rotating Body 30 Horizontal shaft section 31 Vertical section 32 Support part 33 Top part 34 Bottom part 4 Horizontal Rotating Body 40 Vertical shaft section 41 Horizontal part 5 Rotating device 50 Shaft 6. Excavation and mixing equipment (hydraulic auger) 60 Inner cylinder 61 Outer cylinder 62 Outer surface 63 Mixing blade 64 Excavation body 65 Tip Drilling Bit 66 Cement milk outlet 67 Cement milk intermediate outlet 68 Cement milk connection port 69 Hydraulic piping 7. Backhoe 70 Arm 8. Boring Machine 9 Gear type A Ground improvement pile B Ground improvement body (improved body) C Rib S Desired direction T Desired direction 15 Vertical position maintaining member 15a Rod-shaped member 15b Connecting plate member 15c Reinforcement (diagonal member) 16 Anti-vibration member 25 Vertical position maintaining member 26 Flanged joint 27 Main body 25a Vertical position maintaining member piece 27a Plate-shaped member 27b Closure member 35 Vertical position maintaining member 36 component units 36a Plate-shaped member 36b Connecting plate 37 volts 38 Stiffener

Claims

1. A mechanical mixing deep mixing method in which an excavation mixing device attached to the lower end of a rod via a rotating device is penetrated into the soft ground while excavating the soft ground, and a stabilizing material is discharged by penetration discharge or lifting discharge, and mixed with the in-situ soil to create a ground improvement pile or a ground improvement body. The rotating device is a vertical rotating body having a horizontal shaft portion and left and right vertical portions connected to both ends of the horizontal shaft portion and rotatable on a vertical plane, and the left and right vertical portions rotate 90 degrees left and right on the vertical plane, rotating within a range of up to 180 degrees, the upper end of the vertical rotating body is connected to the lower end of the rod, and the left and right vertical portions of the vertical rotating body are connected to the excavation and mixing device, and a horizontally long vertical position holding member for holding the vertical position of the rod is provided on the upper surface of the rotating device or the rod, A ground improvement method using a mechanical mixing deep mixing treatment method, characterized in that the left and right vertical parts of the vertical rotor are used to tilt the excavation and mixing device in the desired direction in the vertical plane within the maximum rotation range of 180 degrees, performing a mixing deep mixing treatment, and creating ground improvement piles or ground improvement bodies of the desired shape in the desired range.

2. A mechanical mixing deep mixing method in which an excavation mixing device attached to the lower end of a rod via a rotating device is penetrated into the soft ground while excavating the soft ground, and a stabilizing material is discharged by penetration discharge or lifting discharge, and mixed with the in-situ soil to create a ground improvement pile or a ground improvement body. the rotation device is formed by combining a vertical rotation body and a horizontal rotation body, and a vertical position holding member that is long in the horizontal direction is provided on an upper surface of the rotation device or on the rod to hold the rod in a vertical position, The vertical rotating body includes a horizontal shaft portion and left and right vertical portions connected to both ends of the horizontal shaft portion and rotatable on a vertical plane, and the left and right vertical portions rotate 90 degrees left and right on the vertical plane, rotating within a range of up to 180 degrees. The upper end of the vertical rotating body is connected to the horizontal rotating body, and the left and right vertical portions of the vertical rotating body are connected to the excavation and stirring device. the horizontal rotor includes a vertical shaft portion and a horizontal portion pivotally supported on the vertical shaft portion and rotatable within a range of 360 degrees on a horizontal plane, the horizontal portion of the horizontal rotor being connected to the vertical rotor, and the vertical shaft portion of the horizontal rotor being connected to a lower end of the rod, A ground improvement method using a mechanical mixing deep mixing treatment method, characterized in that the left and right vertical parts of the vertical rotor of the rotating device tilt the excavation and mixing device in the desired direction on a vertical plane within the maximum rotation range of 180 degrees, and the horizontal part of the horizontal rotor of the rotating device rotates the excavation and mixing device in the desired direction on a horizontal plane, thereby performing a mixing deep mixing treatment and creating ground improvement piles or ground improvement bodies of the desired shape in the desired range.

3. The vertical posture maintaining member is, instead of a horizontally long vertical posture maintaining member provided on the upper surface of the rotating device or the rod, characterized in that the cross-sectional shape of the rod is formed into a rectangular shape in a plan view that improves cross-sectional rigidity. A ground improvement method using a mechanical stirring deep mixing treatment method described in claim 1 or 2.

4. A ground improvement device used in a mechanical mixing deep mixing treatment method in which the device penetrates into the soft ground while excavating the soft ground, discharges stabilizing material by penetration discharge or lift discharge, and mixes and mixes it with the in-situ soil to create ground improvement piles or ground improvement bodies. The ground improvement device comprises a rotation device and an excavation and stirring device, The rotating device is a vertical rotating body having a horizontal shaft portion and left and right vertical portions connected to both ends of the horizontal shaft portion and rotatable on a vertical plane, the left and right vertical portions being configured to rotate 90 degrees left and right on the vertical plane, and to rotate within a range of up to 180 degrees, the excavating and stirring device is connected to the left and right vertical portions of the vertical rotating body, the upper end of the vertical rotating body is attachable to the lower end of a rod, and a horizontally long vertical position holding member for holding the vertical position of the rod is provided on the upper surface of the rotating device or the rod, This ground improvement device is characterized in that the left and right vertical portions of the vertical rotor allow the excavation and mixing device to be tilted in the desired direction in the vertical plane within the maximum rotation range of 180 degrees, thereby creating ground improvement piles or ground improvement bodies of the desired shape within the desired range.

5. A ground improvement device used in a mechanical mixing deep mixing treatment method in which the device penetrates into the soft ground while excavating the soft ground, discharges stabilizing material by penetration discharge or lift discharge, and mixes and mixes it with the in-situ soil to create ground improvement piles or ground improvement bodies. The ground improvement device comprises a rotating device and an excavating and stirring device, and the rotating device comprises a combination of a vertical rotating body and a horizontal rotating body; The vertical rotating body includes a horizontal shaft portion and left and right vertical portions connected to both ends of the horizontal shaft portion and rotatable on a vertical plane, and the left and right vertical portions rotate 90 degrees left and right on the vertical plane, rotating within a range of up to 180 degrees. The upper end of the vertical rotating body is connected to the horizontal rotating body, and the excavating and stirring device is connected to the left and right vertical portions of the vertical rotating body. the horizontal rotor comprises a vertical shaft portion and a horizontal portion pivotally supported on the vertical shaft portion and rotatable within a range of 360 degrees on a horizontal plane, the horizontal portion of the horizontal rotor is connected to the vertical rotor, the vertical shaft portion of the horizontal rotor is attachable to the lower end of a rod, and a vertical position holding member that is long in the horizontal direction is provided on the upper surface portion of the rotation device or on the rod to hold the rod in a vertical position; A ground improvement device characterized in that the left and right vertical parts of the vertical rotor of the rotating device tilt the excavating and stirring device in the desired direction on a vertical plane within the maximum rotation range of 180 degrees, and the horizontal part of the horizontal rotor of the rotating device rotates the excavating and stirring device in the desired direction on a horizontal plane, thereby constructing ground improvement piles or ground improvement bodies of the desired shape within the desired range.

6. 6. The soil improvement device according to claim 4 or 5, wherein the excavating and stirring device is a hydraulic auger or an electric auger.

7. 6. The soil improvement device according to claim 4, wherein the vertical attitude maintaining member is detachably provided on the upper surface of the rotation device or on the rod.

8. A ground improvement device as described in claim 4 or 5, characterized in that the vertical posture maintaining member comprises two horizontally long parallel rod-shaped members and two vertically long connecting plate members that connect the two end portions of the two parallel rod-shaped members to form a frame, and the two parallel rod-shaped members are arranged so as to sandwich the rod when viewed from a planar direction.

9. 9. The soil improvement device according to claim 8, wherein the rod-shaped members are H-shaped steel beams with their webs oriented vertically.

10. A ground improvement device as described in claim 4 or 5, characterized in that the vertical posture maintaining member consists of a pair of left and right vertical posture maintaining member pieces each having a semi-cylindrical flanged joint portion that connects to surround the rod and a main body portion, the main body portion consisting of a plurality of horizontally long parallel plate-shaped members and a blocking member that connects one end of the plate-shaped members, and the other end of the plate-shaped members is connected to the joint portion.

11. The ground improvement device described in claim 10 is characterized in that the horizontal length can be adjusted by adding, as necessary, a component unit consisting of a plurality of horizontally long parallel plate-like members and connecting plates connecting both ends of the plate-like members between the joint portion and the blocking member, instead of the plurality of horizontally long parallel plate-like members.

12. A ground improvement device as described in claim 4 or 5, characterized in that the vertical attitude maintaining member is formed in a rectangular shape in a plan view to improve cross-sectional rigidity, instead of a horizontally long vertical attitude maintaining member provided on the upper surface of the rotating device or the rod.

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