Water bottom ground improvement device

Abstract

To provide a water bottom ground improvement device capable of efficiently agitating and mixing without causing unevenness in quality of modified soil manufactured in a casing when rotating an agitation blade in the casing.SOLUTION: A water bottom ground improvement device 5 comprises: a casing 21 to take existing soil on a sea bottom into the inside thereof; a material feeding path 33 to feed a modifier into the casing 21; and an agitation blade 23 to agitate and mix the existing soil and the modifier in the casing 21. The agitation blade 23 comprises: a rotation axis 60 provided so as to be vertically movable in the casing 21; a center blade part 61c; and a long-short combined blade part having a long axis blade part and a short axis blade part. The center blade part 61c is disposed on the rotation axis 60 so as to be positioned below an exhaust port 34 of the modifier. A plurality of the long-short combined blade parts is disposed so as to be positioned in an end part direction of the rotation axis 60 across the center blade part.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a submarine ground improvement device used for improving submarine ground such as existing seabed ground made of clay soil. [Background technology]

[0002] FIG. 7 of Patent Document 1 discloses a ground improvement device that can be used to improve underwater ground, including seabed ground.

[0003] The ground improvement device disclosed in FIG. 7 of Patent Document 1 has a casing with an agitator blade, a material supply pipe for feeding a modifier such as steel slag into the casing, and a rod and gearbox for transmitting the rotational power of the auger motor to the agitator blade. The agitator blade has a horizontal rotating shaft and multiple blades of equal length. Multiple blades of the agitator blade are provided on both sides of the rotating shaft, with the gearbox in between. The gearbox is provided in the center of the rotating shaft of the agitator blade, and plays a role in changing the horizontal rotation of the rod into vertical rotation by the rotating shaft.

[0004] In seabed ground improvement using the ground improvement device disclosed in FIG. 7 of Patent Document 1, the device is pressed into the ground to take in the clayey soil from the seabed into a casing, and an improvement material is introduced into the casing through a material supply line. The clayey soil and improvement material in the casing are then mixed and stirred with an agitator blade to produce improved soil. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-190667 A (Fig. 7) Summary of the Invention [Problem to be solved by the invention]

[0006] However, when improving seabed ground using the ground improvement device shown in Figure 7 of Patent Document 1, the trajectory of the agitator blade when rotating inside the casing becomes a vertical straight line, which tends to result in a uniform flow in the vertical direction, resulting in a problem that the effect of dispersing the modifier in the horizontal direction is weak.

[0007] In addition, in conventional ground improvement devices, because a gearbox is located in the center of the rotating shaft of the impeller, it is not possible to provide a blade in the center of the impeller. In other words, the blade responsible for mixing is not provided in the center of the casing. As a result, the clayey soil remains in large lumps in the center of the casing without being subjected to the shearing action of the impeller, and it is not possible to mix the modifier evenly into the clayey soil located in the center of the casing. Therefore, in conventional ground improvement devices, there is a risk of bias in the quality of the modified soil produced in the casing.

[0008] Therefore, in order to evenly mix the modifier into the clayey soil inside the casing, it was considered to keep the mixing blades rotating for a long period of time. However, this posed problems such as a significant decrease in mixing efficiency and a long construction time.

[0009] In view of the above-mentioned problems, the object of the present invention is to provide a submerged ground improvement device that enables efficient mixing and stirring without bias in the quality of the improved soil produced within the casing when the mixing blades are rotated within the casing. [Means for solving the problem]

[0010] The above-mentioned object is achieved by a waterbed ground improvement device having a casing capable of taking in existing ground at the bottom of the water, a material supply passage for supplying a modifier toward the inside of the casing, and an agitating blade for agitating and mixing the existing ground taken into the inside of the casing and the modifier, the agitating blade having a horizontal rotating shaft supported at both ends and arranged so as to be able to rise and fall inside the casing below the material supply passage, and a long and short combined blade section having a pair of blade shafts of different lengths, the long and short combined blade section being a combination of a long shaft blade section provided at the tip of a long blade shaft protruding substantially upright from the rotating shaft, and a short shaft blade section provided at the tip of a short blade shaft protruding substantially upright from a position opposite the long blade shaft of the rotating shaft.

[0011] In the above-mentioned waterbed ground improvement device, the mixing blade further has a pair of central blade shafts having the same length protruding from approximately the center of the rotating shaft, and a center blade portion provided at the tip of the central blade shaft for moving the modifier supplied into the casing left and right. The long and short combined blade portions are provided so as to be located toward the end of the rotating shaft, sandwiching the center blade portion.

[0012] In the above-mentioned waterbed ground improvement device, the long axis wing portion, the short axis wing portion and the center wing portion are curved plate-like members.

[0013] In addition, in the above-mentioned waterbed ground improvement device, the axial lengths of the long and short blade shafts in the long and short combined blade section and the shapes of the long and short blade shafts are configured so that the stirring and mixing area produced by the long shaft blade section and the stirring and mixing area produced by the short shaft blade section do not overlap when the rotating shaft rotates once in the circumferential direction.

[0014] In the above-mentioned waterbed ground improvement device, the center wing portion is located below the discharge outlet of the material supply passage, and the axis length of the center wing shaft is set so as not to come into contact with the long axis wing portion.

[0015] In addition, in the above-mentioned waterbed ground improvement device, the long and short combined wing section is provided on the rotating shaft at a predetermined angle relative to other long and short combined wing sections located in front and behind it or the center wing section when viewed from the side.

[0016] In addition, in the above-mentioned submerged ground improvement device, the orientation of the plate-shaped members of the long and short combination wing section and the center wing section is set so as to cut into the modified soil or the native ground obtained by mixing and stirring the native ground and the modifying material as the rotating shaft rotates in the circumferential direction, and push out the modified soil approximately horizontally in the directions of both ends of the rotating shaft.

[0017] The water-bed ground improvement device further includes a rotating shaft holding portion that rotatably holds the rotating shaft.

[0018] The waterbed ground improvement device further includes a vertical rod that is rotatable laterally by a rotary drive device, and the rotary shaft holder includes a gear box that converts the horizontal rotation of the vertical rod into vertical rotation by the mixing blade. Effect of the Invention

[0019] By shortening one of the impeller shafts to create a long and short combined structure, a complex flow can be generated when the impeller rotates, enabling efficient mixing and mixing in a short time. If the impeller shaft length is uniform, there is a risk of clay or modified soil adhering to the inside of the blade, causing the soil and impeller to rotate together without mixing and mixing, but with the long and short combined structure, the area subjected to the shearing action of the impeller becomes complex, which also has the effect of suppressing the co-rotation phenomenon.

[0020] Furthermore, by providing a center blade portion approximately in the center of the rotating shaft, it is possible to provide a sufficient stirring and mixing effect to the clayey soil in the center of the casing, which could have been insufficiently stirred with conventional devices.

[0021] In addition, by preventing the mixing areas of the "long-axis blade section" and the "short-axis blade section" from overlapping, the mixing area per rotation of one "combined long and short blade section" can be expanded, enabling efficient mixing in a short amount of time.

[0022] In addition, by providing a center wing section below the discharge outlet of the material supply passage, the modifying material introduced into the casing can be distributed evenly to the left and right by the center wing section immediately after it is introduced, making it possible to spread the modified soil throughout the clayey soil inside the casing, thereby improving the quality of the modified soil produced within the casing.

[0023] In addition, by providing a combination of long and short blades with a predetermined angle difference, the modifier introduced into the center of the casing can be smoothly distributed to the corners of the casing. Also, the clayey soil around the mixing blades can be uniformly mixed.

[0024] In addition, by arranging the plate-shaped members of the long and short combination blade section and the center blade section so that they cut into the clayey soil as they rotate and push it out to both sides inside the casing, it is possible to finely chop up large, hard lumps of clayey soil and spread the modifier throughout the clayey soil inside the casing, thereby reducing the torque required to rotate the agitator blades and avoiding overload.

[0025] In addition, by providing a lift-type rotating shaft holding section within the casing, it becomes possible to raise and lower the agitator blade while rotating within the casing, thereby eliminating any bias in the quality of the modified soil produced in the vertical direction within the casing.

[0026] Furthermore, by providing a gear box to the rotating shaft holder, the mounting position of the rod that rotates the agitating blade can be shifted to the side. As a result, it becomes possible to provide a material supply path for supplying the modifier into the casing at the position where the rod was located in the conventional device (i.e., in the center of the casing). Furthermore, by connecting the gear box and the end of the rotating shaft of the agitating blade via a pulley and chain, it becomes possible to provide the blade parts at equal intervals all over the rotating shaft of the agitating blade, including the center. And by feeding the modifier toward the center of the casing, it becomes possible to distribute the modifier evenly between the left and right sides of the casing. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1A is a side view showing a work vessel (ground improvement vessel) equipped with the underwater ground improvement device of the present invention, and FIG. 1B is an enlarged side view showing the seabed ground improvement process using the underwater ground improvement device. [Diagram 2] FIG. 2(a) is a perspective view (enlarged front view) showing the subaqueous ground improvement device of the present invention, in which FIG. 2(a) shows the state in which the agitator blades in the casing are raised, and FIG. 2(b) shows the state in which the agitator blades are lowered. [Diagram 3] FIG. 3 is a perspective view (enlarged side view) showing the submarine ground improvement device of the present invention, in which FIG. 3(a) shows the grab at the lower end of the casing in an open state, and FIG. 3(b) shows the grab in a closed state. [Figure 4] 4 is an enlarged view showing an agitating blade provided in the waterbed ground improvement device shown in FIG. 2, FIG. 4(a) is a front view showing the agitating blade, and FIG. 4(b) is a side view showing the agitating blade. [Diagram 5] These are diagrams showing each blade portion of the agitator blade shown in Figure 4, where Figure 5(a) is a side view showing long and short combined blade portion 61a, Figure 5(b) is a side view showing long and short combined blade portion 61b, Figure 5(c) is a side view showing center blade portion 61c, Figure 5(d) is a side view showing long and short combined blade portion 61d, and Figure 5(e) is a side view showing long and short combined blade portion 61e. [Figure 6]FIG. 2 is a side view showing the effect of the agitator blades inside the casing of the underwater ground improvement device. [Figure 7] FIG. 1 is a process diagram showing an example of ground improvement using a subaqueous ground improvement device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The waterbed ground improvement device according to the present invention is mounted on a work ship 1 (ground improvement ship) as shown in Fig. 1(a). The work ship 1 has a leader 3 erected on the bow side and a waterbed ground improvement device 5 installed along the leader 3 so as to be able to move up and down freely.

[0029] As shown in FIG. 1(b), the underwater ground improvement device 5 can be used in ground improvement work, for example, to produce improved soil by stirring and mixing the existing seabed ground (clay soil) and improvement material in situ, and replacing the existing seabed ground with the improved soil.

[0030] The configuration of the waterbed ground improvement device 5 will be described below with reference to Figs. In addition, specific examples of the "bottom" in this application include the bottom of the ocean, the bottom of a river, and the bottom of a lake. In the following explanation of the present invention, the bottom of the ocean will be given as an example of the bottom of the ocean.

[0031] (Underwater soil improvement device) As shown in FIG. 1, the waterbed ground improvement device 5 is provided so as to be able to move up and down along the leader 3. Also, as shown in FIGS. 1 to 3, A casing 21 capable of incorporating the clayey soil (conventional soil) on the seabed inside; A mixing blade 23 for mixing the clayey soil and the modifier taken into the casing 21; A rotating shaft holder 25 that is provided in the casing 21 so as to be capable of ascending and descending and that holds the rotating shaft 60 of the agitating blade 23; A support tube 31 which is an outer tube of the multi-wall tube 30 and supports the casing 21; A material supply passage 33 which is an inner pipe of the multiple pipes 30 and supplies a modifier into the casing 21; A support tube 22 that supports one side of the top end of the rotating shaft holding portion 25; A support tube 41 which is an outer tube of the multiple tubes 40 and supports one side of the rotating shaft holding portion 25; A rod 43 which is an inner tube of the multiple tubes 40 and is oriented vertically to rotate the stirring blades 23; The auger motor 7 drives the agitating blade 23 via the rod 43, etc. It has.

[0032] The casing 21 is a box-shaped container-like component (rectangular casing) that is generally rectangular in plan view, and is configured so that the opening at the bottom can be opened and closed. A support tube 31, which is an outer tube of the multiple tubes 30, is connected to the center of the top end of the casing 21. The casing 21 can be raised and lowered by raising and lowering the support tube 31.

[0033] An openable grab 27 is provided at the tip (lower end) of the casing 21. The combination of the casing 21 and the grab 27 can be said to constitute one casing as a whole. When the grab 27 is opened, the bottom of the casing 21 is opened, and when the grab 27 is closed, the bottom of the casing 21 is closed and sealed. The grab 27 not only serves as a means for taking in the clayey soil layer on the seabed into the casing 21, but also serves as a lid for opening and closing the bottom of the casing 21 (a lid for sealing the bottom of the casing 21).

[0034] The grab 27 has, for example, a hydraulic cylinder as a means for opening and closing the grab. 3(a) shows the grab 27 in an open state. In this state, the bottom of the casing 21 is open. Then, through a series of operations when the grab 27 goes from an open state to a closed state, the clayey soil layer on the seabed can be taken into the inside of the grab 27 and the casing 21. 3(b) shows the state in which the grab 27 is closed. In this state, the bottom of the casing 21 is closed and the casing 21 is sealed. If the grab 27 is closed after taking clay soil into the casing 21, the casing 21 will be sealed and the clay soil will be trapped inside the casing 21.

[0035] The material supply passage 33, which is the inner pipe of the multiple pipes 30, has a modifying agent outlet 34 above (directly above) the agitating blade 23, and functions as a flow path for feeding the modifying agent toward the agitating blade 23 in the casing 21. The lower part of the material supply passage 33 protrudes from the upper bottom surface of the rotating shaft holding part 25, and the outlet 34 at its lower end is provided to face the center blade part 61c of the agitating blade 23 at a predetermined interval (for example, a predetermined interval of about several tens of cm). The outlet 34 of the material supply passage 33 is located at the center of the casing 21. A material inlet 35 (not shown) for feeding the modifying agent into the material supply passage is provided above the material supply passage 33.

[0036] The modifier fed from the material feed port 35 passes through the material supply path 33, is discharged from the discharge port 34 protruding into the casing 21, and is fed into the casing 21. The modifier fed into the casing 21 is distributed by the stirring blades 23 so as to be evenly distributed throughout the clayey soil taken into the casing 21.

[0037] 2(a) and 2(b), the material supply passage 33, which is an inner pipe, is provided so that the vertical position of its discharge port 34 follows the rising and falling movement of the agitating blade 23 in the casing 21. In other words, the agitating blade 23 and the material supply passage 33 are configured to be able to rise and fall together.

[0038] The multiple pipes 40 have a support pipe 41 made of an outer pipe that supports one upper side of the rotating shaft holding part 25, and a vertical rod 43 that is provided inside the support pipe 41 and is rotatable horizontally, that is, in the circumferential direction. The upper end of the rod 43 is connected to the auger motor 7, which is a rotation drive device, and the lower end of the rod 43 is connected to a gear box 51 of the rotating shaft holding part 25.

[0039] As shown in Fig. 1(a), the auger motor 7 is connected to the leader 3 so as to be able to move up and down freely, and its upper end is connected to the wire rope 4. By operating the wire rope 4 in the up and down direction, the entire waterbed ground improvement device 5 including the auger motor 7 moves up and down along the leader 3.

[0040] A hydraulic cylinder is provided near the auger motor 7 to raise and lower the rotating shaft holder 25 inside the casing 21. The support pipes 22, 41 move up and down due to the pushing and pulling action of this hydraulic cylinder, and the rotating shaft holder 25 moves up and down inside the casing 21 in conjunction with this movement.

[0041] The rotating shaft holding part 25 rotatably holds the rotating shaft 60 of the agitating impeller 23. In addition, the support pipes 22, 41 are connected to both sides of the top end of the rotating shaft holding part 25, and by moving the support pipes 22, 41 up and down, the rotating shaft holding part 25 moves up and down within the casing 21 in conjunction with the up and down movement. At that time, as shown in Figures 2(a) and (b), the rod 43 for rotating the agitating impeller 23 and the material supply path 33 for feeding the modifier into the casing 21 move up and down together with the rotating shaft holding part 25.

[0042] The rotating shaft holding part 25 is provided with a power transmission mechanism including a gear box 51, pulleys 53 and 54, and a chain 55. The gear box 51 is provided on the side of the upper part of the rotating shaft holding part 25, and the pulleys 53 and 54 and the chain 55 are provided on the side of the rotating shaft holding part 25.

[0043] The rotational power output from the auger motor 7 is transmitted to the rod 43 rotating in the horizontal direction, and is further transmitted to the rotating shaft 60 of the agitating blade 23 via a gear box 51, pulleys 53, 54, and a chain 55. The power transmission mechanism, which is comprised of the gear box 51, pulleys 53, 54, chain 55, etc., provided in the rotating shaft holding part 25, converts the circumferential rotation of the vertically oriented rod 43 into vertical rotation by the agitating blade 23.

[0044] The agitator 23 is rotatably held by the rotary shaft holder 25 within the casing 21, and is provided integrally with the rotary shaft holder 25 so as to be movable up and down within the casing 21. The agitator 23 mainly plays a role in stirring and mixing the seabed clayey soil taken into the casing 21 by the grab 27 and the modifier charged into the casing 21. The agitator 23 also plays a role in loosening (loosening) the clayey soil taken into the casing 21 before the above-mentioned stirring and mixing is performed.

[0045] The configuration of the stirring blade of the waterbed soil improvement device 5 will be specifically described below with reference to Figs.

[0046] (stirring blade) The agitating blades 23 play a role in agitating and mixing the clayey soil taken into the casing 21 and the modifier charged into the casing 21 .

[0047] As shown in FIG. 4 and FIG. 5, the stirring blade 23 is A horizontally oriented rotating shaft 60 that can be raised and lowered within the casing 21; A center blade portion 61c having center blade shafts 63, 63 of equal length; The rotor blade 61 has combined long and short blade portions 61a, 61b, 61d, and 61e each having a long axis blade portion 66 and a short axis blade portion 68.

[0048] The rotating shaft 60 is provided inside the casing 21 below the material supply passage 33 so as to be movable up and down, and both ends thereof are supported by the rotating shaft holders 25 .

[0049] In this embodiment, a center wing portion 61c is provided at approximately the center of the rotating shaft 60. In addition, long and short combined wing portions 61a and 61b are provided on the left side of the rotating shaft 60, and long and short combined wing portions 61d and 61e are provided on the right side of the rotating shaft 60. These wing portions 61a, 61b, 61c, 61d, and 61e are provided at equal intervals. Hereinafter, the long and short combined wing portions will be abbreviated as "long and short wing portions."

[0050] The center wing portion 61c is provided approximately in the center of the rotating shaft 60 via a pair of center wing shafts 63, 63 of equal length. The pair of center wing shafts 63, 63 protrude from approximately the center of the rotating shaft 60, and wing portions 64, 65 are provided at the tips of the center wing shafts 63, 63. In addition, the axial length of the center wing shafts 63, 63 is set so that the center wing portion 61c does not come into contact with the long axis wing portions 66 of the long and short wing portions 61b, 61d located in front and behind it.

[0051] Moreover, the center wing portion 61c is provided so as to be located immediately below the discharge port 34 of the material supply path 33. By providing the discharge port 34 of the material supply path 33 in the center within the casing 21 and providing the center wing portion 61c immediately below the discharge port 34, the modifier introduced into the casing 21 can be spread within the casing 21 in the direction toward both ends of the rotating shaft to the inner wall of the casing 21 in the shortest distance.

[0052] 5(c) and 6, the center wing portion 61c has a left wing portion 64 for distributing the modifier fed into the casing 21 from the discharge port 34 of the material supply path 33 to the left direction, which is one side of the end of the rotating shaft in the casing 21, and a right wing portion 65 for distributing the fed modifier to the right direction, which is the other side of the end of the rotating shaft. The lengths of the center wing shafts 63, 63 of the left wing portion 64 and the right wing portion 65 are equal.

[0053] 5(a), (b), (d), and (e), the long and short wing sections 61a, 61b, 61d, and 61e each have a pair of wing shafts 67 and 69 of different lengths. Each of the long and short wing sections 61a, 61b, 61d, and 61e is composed of a combination of a long wing section 66 provided at the tip of a long wing shaft 67 protruding from the rotating shaft 60 so as to stand upright, and a short wing section 68 provided at the tip of a short wing shaft 69 protruding from a position facing the long wing shaft 67 of the rotating shaft 60 so as to stand upright.

[0054] The long-shaft wing section 66, which is provided with the long and short wing sections 61a, 61b, 61d, and 61e, is provided on the rotating shaft 60 via a long wing shaft 67. The short-shaft wing section 68 is provided on the rotating shaft 60 via a short wing shaft 69. When the rotating shaft 60 rotates once in the circumferential direction, the stirring and mixing area A by the long-shaft wing section 66 is located on the outside, and the stirring and mixing area B by the short-shaft wing section 68 is located on the inside. In other words, the axial length of the wing shafts 67 and 69 and the shapes of the wing sections 66 and 68 are set so that the long-shaft wing section 66 and the short-shaft wing section 68 stir and mix in different stirring and mixing areas A and B. The stirring and mixing area A by the long-shaft wing section 66 and the stirring and mixing area B by the short-shaft wing section 68 may be partially overlapping areas, or may not be overlapping areas.

[0055] The blades 61a, 61b, 61c, 61d, and 61e are attached to the rotating shaft 60 at an angle that allows the modifier introduced into the casing 21 to be distributed approximately evenly in the left and right directions in the casing during one rotation of the agitating blade 23. That is, the blades 61a, 61b, 61c, 61d, and 61e are attached to the rotating shaft at a predetermined angle relative to the other blades located in front and behind them in a side view. In this embodiment, as shown in FIG. 4(b) as an example, the blades are attached to the rotating shaft 60 at equal angular intervals with an angle difference of 60 degrees in a side view.

[0056] Additionally, the wing portions 66, 68 provided at the tips of the long and short wing portions 61a, 61b, 61d, 61e and the wing portions 64, 65 provided at the tip of the center wing portion 61c are made of curved plate-like members. The orientation of each plate-like member constituting the wing portions 66, 68 and the wing portions 64, 65 is set so as to cut into the modified soil, which is made by mixing the modified material with the conventional ground, and the conventional ground as the rotating shaft 60 rotates in the circumferential direction, and to push the modified soil and the conventional ground substantially horizontally toward both ends of the rotating shaft 60.

[0057] Next, the function and action of each blade portion of the agitating blade 23 will be described mainly with reference to Figs.

[0058] 4, the blade sections 61a, 61b, 61c, 61d, and 61e of the agitator 23 not only mix the clayey soil and the modifier, but also cut into and push out modified soil obtained by mixing the clayey soil and the modifier, or clayey soil in the process of being mixed, to both sides of the casing 21. In addition, the blade sections 61a, 61b, 61c, 61d, and 61e of the agitator 23 mix the clayey soil and the modifier, as the agitator 23 rotates in the direction of arrow A in Fig. 4.

[0059] In addition to the above-mentioned roles, the center blade portion 61c also has the role of evenly distributing the modifier supplied into the casing 21 to the left and right directions within the casing 21 as the agitating blade 23 rotates in the direction of arrow A in Fig. 4. In this respect, the center blade portion 61c differs from the long and short blade portions 61a, 61b, 61d, and 61e. Therefore, the shapes of the blade portions 64 and 65 of the center blade portion 61c are different from the shapes of the blade portions 66 and 68 of the long and short blade portions 61a, 61b, 61d, and 61e.

[0060] That is, the blades 64, 65 of the center blade 61c and the blades 66, 68 of the long and short blades 61a, 61b, 61d, 61e are common in that they are plate-shaped members curved in the direction of rotation as a whole, but the long and short blades 61a, 61b, 61d, 61e do not have the role of distributing the modifier evenly to the left and right inside the casing 21 like the center blade 61c, so the blades 66, 68 of the long and short blades 61a, 61b, 61d, 61e have a tapered shape with a tip that tapers toward the direction of rotation. By giving the blades 66, 68 such a tapered shape, the cutting performance of the modified soil and clayey soil during the rotation of the agitator blade 23 is improved. On the other hand, the wing portions 64, 65 of the center wing portion 61c are made of curved rectangular members in order to prioritize the performance of distributing the modifier supplied into the casing 21 approximately evenly in the left and right directions, and do not have a tapered shape like the wing portions 66, 68.

[0061] In FIG. 6, the long and short wing section 61b located to the left of the center wing section 61c, in addition to the roles described above, also plays a role in moving further to the left the modifier distributed to the left by the left wing section 64 of the center wing section 61c and the clayey soil cut into small pieces by the center wing section 61c. The long and short wing section 61a, located to the left of the long and short wing section 61b, in addition to the functions mentioned above, has the role of further moving the modifier moved to the left by the long and short wing section 61b and the clayey soil that has been finely cut by the center wing section 61c and the long and short wing section 61b further to the left, so that they can be distributed to the inner wall of the casing 21.

[0062] The long and short wing section 61d located to the right of the center wing section 61c, in addition to the roles mentioned above, also plays a role in moving further to the right the modifier distributed to the right by the right wing section 65 of the center wing section 61c and the clayey soil that has been finely cut by the center wing section 61c. The long and short wing section 61e, located immediately to the right of the long and short wing section 61d, has the role, in addition to the roles mentioned above, of moving the modifier moved to the right by the long and short wing section 61d and the clayey soil that has been finely cut by the center wing section 61c and the long and short wing section 61d further to the right, so that they can be distributed to the inner wall of the casing 21.

[0063] By continuously stirring and mixing by the above-mentioned blades 61a, 61b, 61c, 61d, and 61e, a flow is generated in which the modified soil and clayey soil move from the center of the casing 21 toward both ends of the rotating shaft, and a flow is generated in which the modified soil and clayey soil collide with the inner wall of the casing 21 and move from the inner wall side to the center. As a result, a flow is generated in which the modified soil and clayey soil circulates within the casing 21 (a flow from the center of the casing 21 toward both ends of the rotating shaft, followed by a flow from the inner wall side of the casing 21 toward the center).

[0064] The rotation of the agitator blades 23 generates a circulating flow as described above within the casing 21, while the agitator blades 23 are raised and lowered within the casing 21, thereby making it possible to distribute the modified soil evenly throughout the clayey soil within the casing 21, and as a result, high-quality modified soil without any bias in quality can be produced within the casing 21.

[0065] In this embodiment, as an example, five blade portions are provided on the rotating shaft 60 of the agitating blade 23, but the number of blade portions is not particularly limited as long as the effects of the present invention can be achieved.

[0066] (Example of seabed ground improvement using underwater ground improvement equipment) Next, a specific example of seabed ground improvement work using the above-mentioned waterbed ground improvement device 5 will be described with reference to Fig. 7. Note that steps a to h described below correspond to Fig. 7(a) to (h).

[0067] Process a The grab 27 at the tip of the casing 21 is opened, and compressed air is sent into the casing 21 of the waterbed ground improvement device through the material supply path 33 to drain the seawater from the casing and make the inside of the casing 21 hollow. In other words, the air pressure ensures a space without seawater inside the casing 21. Thereafter, the air pressure keeps the casing 21 from flowing in.

[0068] Process b The tip of the underwater ground improvement device, i.e., the grab 27 at the tip of the casing 21, is pressed against the top of the clayey soil (conventional soil) on the seabed.

[0069] Process c Then, the hydraulically driven grab 27 at the tip of the casing 21 is repeatedly opened and closed to draw the clayey soil into the casing 21.

[0070] Process d Once the required amount of clay has been taken into the casing 21, the grab 27 at the end of the casing is closed, thereby sealing the casing 21 and isolating the clay taken into the casing 21 from the seawater and clay surrounding the casing.

[0071] Process e The agitator blades 23 in the casing 21 are lowered, and the clayey soil taken into the casing 21 is loosened by the rotation of the agitator blades 23. This loosens the hard clayey soil in the casing 21, making it possible to uniformly mix the clayey soil and the modifier in the subsequent step (step g).

[0072] process f With the tip (grab 27) of the casing 21 kept closed, a predetermined amount of modifier is fed into the casing 21 through the material supply path 33. For example, a material that reacts with clayey soil and hardens is used as the modifier. A specific example of such a material is a material that causes a hydration reaction, such as a calcia modifier. The calcia modifier is a material that has its components controlled and its particle size adjusted using converter steelmaking slag, a type of steel slag, as the raw material.

[0073] Process g After the modifier is poured into the casing 21, the agitator blades 23 inside the casing 21 are rotated and moved up and down inside the casing 21 to mix and stir the "clay soil taken into the casing 21" and the "modifier poured into the casing 21." By mixing and stirring these inside the casing 21, "modified soil" is produced.

[0074] Process h Next, the tip of the casing 21 (grab 27) is opened, and the casing 21 is pulled upward while the thoroughly mixed and stirred modified soil is discharged by dropping it from the casing 21, and the modified soil is backfilled in the original location (the location where the clayey soil was taken in). Through the above procedure, the existing ground consisting of clayey soil is replaced with the modified soil. When discharging the modified soil from the casing 21, if the modified soil does not fall well after the grab 27 is opened or if it is desired to forcibly discharge the modified soil, compressed air may be sent into the casing 21 as an auxiliary means. Also, the mixing blades 23 may be lowered without rotating to push the modified soil out of the casing 21.

[0075] Finally, the above-mentioned embodiment is an example of the present invention described in the claims, and the form of the present invention is not necessarily limited to this. The number of long and short combined blades 61a, 61b, 61d, and 61e having the above-mentioned long-shaft blade 66 and short-shaft blade 68 can also be changed according to the size of the casing 21 used. In addition, the application of the present invention is not limited to the improvement of the seabed, but can also be used for the improvement of the riverbed or lakebed. [Explanation of symbols]

[0076] 1. Work boat (ground improvement boat) 3. Leader 4. Wire Rope 5 Underwater soil improvement equipment 7 Auger motor 21 Casing 22 Support pipe 23 Stirring blade 25 Rotating shaft holder 27 Grab 30 multiple tubes 31 Support tube (outer tube) 33 Material supply path (inner pipe) 34 Outlet 35 Material input port 40 multiple tubes 41 Support tube (outer tube) 43 Rod (inner tube) 51 Gearbox 53 Pulley 54 Pulley 55 Chain 60 Rotational Axis 61a Long and short combined wing section (long and short wing section) 61b Long and short combined wing section (long and short wing section) 61c Center wing 61d Long and short combined wing section (long and short wing section) 61e Long and short combined wing section (long and short wing section) 63 Central wing axis 64 Left Wing 65 Right wing 66 Long axis wing section 67 Long wing shaft 68 Short axis wing section 69 Short wing shaft

Claims

1. A casing that can incorporate the existing ground at the bottom of the water into the inside, a material supply passage for supplying a modifier toward the inside of the casing; The casing has an agitator for agitating and mixing the existing ground and the modifier taken inside the casing, The stirring blade is a horizontal rotating shaft that is vertically movable inside the casing below the material supply passage and has both ends supported; A long-short combined wing section having a pair of wing shafts of different lengths, the long-shaft wing section being provided at the tip of the long wing shaft protruding from the rotating shaft so as to stand upright, and the short-shaft wing section being provided at the tip of the short wing shaft protruding from a position facing the long wing shaft of the rotating shaft so as to stand upright, A waterbed ground improvement device comprising:

2. The stirring blade further comprises: a pair of central blade shafts having equal lengths protruding from approximately the center of the rotating shaft; and a center blade portion provided at a tip of the central blade shaft for moving the modifier supplied into the casing to the left and right; The long and short combined wing portions are provided so as to be positioned toward the end portion of the rotation shaft across the center wing portion.

2. The waterbed ground improvement device according to claim 1.

3. The long axis wing portion, the short axis wing portion, and the center wing portion are curved plate-shaped members.

3. The waterbed ground improvement device according to claim 2.

4. The axial lengths of the long blade shaft and the short blade shaft in the long-short combined blade section and the shapes of the long blade shaft and the short blade shaft are configured so that the stirring and mixing area by the long blade shaft and the stirring and mixing area by the short blade shaft do not overlap when the rotating shaft rotates once in the circumferential direction. The waterbed ground improvement device according to any one of claims 1 to 3.

5. The center blade portion is located below the discharge port of the material supply passage, and the axis length of the center blade shaft is set so as not to contact the long axis blade portion.

3. The waterbed ground improvement device according to claim 2.

6. The long and short combined wing portion is provided on the rotating shaft at a predetermined angle with respect to other long and short combined wing portions located in front and behind the center wing portion in a side view.

3. The waterbed ground improvement device according to claim 2.

7. The orientation of the plate-shaped members of the long and short combination wing portion and the center wing portion is such that the modified soil or the modified soil obtained by mixing the modified soil and the modified material is cut into the modified soil or the modified soil as the rotating shaft rotates in the circumferential direction, and the modified soil is pushed out approximately horizontally toward both ends of the rotating shaft.

4. The waterbed ground improvement device according to claim 3.

8. The waterbed ground improvement device further includes: A rotating shaft holder that rotatably holds the rotating shaft is provided.

2. The waterbed ground improvement device according to claim 1.

9. The waterbed ground improvement device further has a vertical rod that is rotatable laterally by a rotary drive device, The rotating shaft holder is provided with a gear box that converts the rotation of the vertical rod into vertical rotation by the stirring blade. The waterbed ground improvement device according to claim 8.

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