JP3711351B2 - Bottom sediment mixing method and equipment - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a bottom sediment mixing method for a seabed, a riverbed, and the like, and an apparatus thereof, and more particularly, to a bottom sediment improvement method and a device for a seabed of a seabed, such as clams, a sea bream, a sea bass, and a riverbed. .

Recently, the amount of landed shellfish, such as coastal clams and larvae, has been decreasing. Possible causes include global warming, changes in ocean currents, and anaerobic conditions in the sediment. However, although it is difficult to artificially control the global warming phenomenon and ocean current changes, it is possible to improve the oxygen state of the sediment and improve the sediment.
For example, on the seabed showing a typical shallow terrain with a distance of 1.5km and a water depth of around 7m, for example, on a certain coast, the average slope is extremely gentle, about 1/350 to 1/260. The bottom sediment is about 75 to 80% of silt and clay, showing a very fine particle size in general, COD of 7.02 to 8.69 mg / g in chemical components, and sulfide. It is 0.130 to 0.277 mg / g.
And the sea condition shows a mud and shallow terrain with a large tidal range, and because the tidal range is large, a vast tidal flat is formed, but in developing a fishing ground for clams such as clams and tyrants in that tidal flat, Improvement of the bottom quality is essential.
However, it seems to be difficult to cope with ordinary construction methods such as sand cover, seabed cultivation, and earth and sand replacement.

Japanese Patent No. 3303169

However, according to this conventional sand-capping method, even if the sand is thin, for example, 10.0 cm to 20.0 cm, the sand is covered by the influence of the ocean current and the tidal range. I can't stay in the sand.
In addition, the sand itself may be buried in the silt layer due to its own weight.
Also, according to the method of submarine tillage, the ground can be improved using land machines at low tide, but heavy machinery work is impossible when the geology is 80% silt.
In addition, in the case of the earth and sand replacement method, there will be a problem of contamination of the sea surface when selecting and discarding dredged soil when replacing the earth and sand.

  Therefore, the main object of the present invention is to provide a bottom soil mixing method and apparatus capable of improving the oxygen-free state of the bottom sediment and improving / improving the bottom sediment.

According to claim 1 of the present invention, the bottom soil mixing method includes step 1 of enclosing a sediment such as sediment on the bottom layer of the bottom with a cage, and a bottom of sediment or the like in a region within the cage. Step 2 for fluidizing the object with a jet of water and Step 3 for pumping the sand into the cage along with the water stream on the surface of the bottom such as sediment fluidized in the region within the cage. And, in the region inside the cage, step 4 for agitating and mixing the pumped sand and the fluidized sediment bottom to improve the particle size of the bottom sediment. It is a bottom sediment mixing method.
The step 4 of the bottom soil mixing method according to claim 2 of the present invention includes agitating and mixing the sand fed by the water jet and the fluidized deposit with a stirring blade. Item 2. The bottom soil mixing method according to Item 1.
In the step 3 of the bottom soil mixing method according to claim 3 of the present invention, the cage having the agitator blades rotatably provided therein is pulled up to the vicinity of the bottom sediment surface of the water bottom, and then the sand is placed inside the cage. The bottom sediment mixing method according to claim 1 or 2, wherein the method is pumped into a partition wall.
In the step 4 of the bottom soil mixing method according to claim 4 of the present invention, the bottom of the bottom of the water bottom is pushed by the stirring blade while pushing down the cage in which the stirring blade is rotatably provided to the depth where the shellfish can live. The bottom sediment mixing method according to any one of claims 1 to 3, which improves the grain size of the quality.
The bottom soil mixing apparatus according to claim 5 of the present invention includes a stirring and mixing apparatus that settles on the bottom of the water and improves the stirring of the bottom of the water, a transport apparatus that transports the stirring and mixing apparatus to a specific area of the bottom of the water, and the stirring and mixing A water feeding device for sending water to the device, and a sand feeding device for sending sand to the stirring and mixing device, the stirring and mixing device comprising a cage in which a stirring blade is rotatably provided, and the water feeding device The apparatus is configured to fluidize bottom sediment such as sediment on the bottom by jetting water, and configured to send sand fed by the sand feeding apparatus to the stirring and mixing apparatus by jet water flow. It is a bottom soil mixing device.
In the sediment mixing device according to claim 6 of the present invention, the stirring and mixing device includes a partition provided in the cage that vertically separates the depth direction of the cage, and is provided in a region surrounded by the cage, the partition, and the water bottom. A high pressure water jet nozzle and a stirring blade are arranged, and a hose of a water feed device and a sand feed device is connected to the partition wall, and the high pressure water jet nozzle is formed so that sand is pumped from the hose by a jet water flow. The bottom sediment mixing device according to claim 5, wherein a hose of a water feeding device is connected, high pressure water is fed from the hose, and jet injection is performed.

According to the bottom soil mixed construction method according to the present invention, there is almost no water pollution at the time of construction, etc., even if there is a large difference in tidal area of construction sea, there is no outflow of sand, and the grain size of the construction site can be freely changed can do.
Moreover, even when the topography of the construction sea area is complicated or when the water depth of the construction sea area is deep, the construction management can be performed relatively easily. According to this construction method, it is possible to improve the bottom quality by consolidating the local board, stirring, and water pressure so that the bottom of the water is inverted 180 degrees up and down to send oxygen.
In addition, according to the bottom soil mixing apparatus according to the present invention, since the partition walls and the like have sufficient weight, they are not affected by water currents such as ocean currents, and almost cause problems such as contamination of water surfaces such as sea surfaces. Since there is nothing, there is little impact on shellfish fishing grounds.
In addition, sand loss is minimized because sand is pumped and filled to improve the bottom quality.

  The above-mentioned object, other objects, features, and advantages of the present invention will become more apparent from the following description of the best mode for carrying out the invention with reference to the drawings.

  FIG. 1 is an illustrative view showing a construction situation of a bottom soil mixing method using a bottom soil mixing device, FIG. 2 is a plan view of the bottom soil mixing device, and FIG. 3 is a sand feeding device. FIG. 4 is a side view of the sand feeder. FIG. 5 is a plan view illustrating a state where three sand feeding devices are connected, FIG. 6 is a front view illustrating a state where three sand feeding devices are connected, and FIG. It is an illustration figure which shows a connection state with other hose. FIG. 8 is a perspective view showing an example of the stirring and mixing device, FIG. 9 is a bottom view of the bottom soil mixing device, and FIG. 10 is a cross sectional view of the bottom soil mixing device.

The seabed bottom soil mixing device 10 includes a ground improvement ship 12 and a stirring mixing device 14.
The ground improvement ship 12 is divided into two halves. A hoist ship 12a constituting the ground improvement ship 12 is equipped with a transport device 16 and a water feed device 18, and a worker enters and performs a bottom sediment improvement work on the seabed. In the state where the stirring and mixing device 14 is suspended by the transporting device 16, the stirring and mixing device 14 is transported to the work site where the bottom sediment improvement method is performed.

The trolley 12b constituting the ground improvement ship 12 includes a sand storage area 22 on which the sand feeding device 20 is mounted and used for improving the bottom sediment, and the sand stored in the sand storage area 22 is sand transported. A backhoe 24 for carrying and feeding to 20 is loaded.
The trolley 12b is configured to be able to move on the sea by towing it with a tug with a propulsion power.

The transport device 16 includes a hoist 30, and is configured such that a wire 34 is hung from the tip of a boom 32 of the hoist 30, and the stirring and mixing device 14 is suspended from the tip of the wire 34.
The hoist 30 is mounted on a swivel base 36 that can rotate in a horizontal plane, and the swivel base 36 is fixed on the ground improvement ship 12.
The transporting device 16 is configured to lift the stirring and mixing device 14 with power, change the elevation angle of the boom 32 and rotate the swivel 36 to transport the stirring and mixing device 14 vertically and horizontally. ing.

The transporting device 16 is configured to measure the depth of the stirring and mixing device 14 with a built-in depth meter (not shown) and perform digital data management with the personal computer 28.
That is, the depth measurement by the depth meter is performed by measuring the number of revolutions of the drum 38 around which the wire 34 provided in the transport device 16 is wound, and measuring the length of the wire 34 that is lowered by the number of revolutions. The depth of the stirring and mixing device 14 is measured, and further, the personal computer 28 digitizes and manages the depth.

The water feeding device 18 includes a jet pump 40 fixed on the ground improvement ship 12, and water pressurized to a high pressure via a first hose 42 connecting the jet pump 40 and the stirring and mixing device 14 is supplied to the water feeding device 18. It is configured to be sent to the stirring and mixing device 14.
The first hose 42 is connected by a high-pressure valve 44, and the second hose 48 branched by a manifold 46 provided upstream from the high-pressure valve 44 is connected to the stirring and mixing device 14 via the sand feeder 20. ing.

The sand feeder 20 is a device that feeds sand into the jet water stream sent to the second hose 48 by the jet pump 40, and pressure-feeds the sand to the stirring and mixing device 14 by the jet water stream, and includes a hopper 50.
The hopper 50 is fixed to the carriage 12 b of the ground improvement ship 12 with a frame 52.
A vibration motor 54 is attached to the side wall of the hopper 50 so that the sand put in the hopper 50 is vibrated and the sand falls downward.
A shutter 56 is provided below the hopper 50, and the shutter 56 is configured to be opened and closed by a hydraulic cylinder 58. Further, a T-shaped elbow 60 is provided at the lower portion of the hopper 50, and a second hose 48 is connected to the elbow 60.

The vibration motor 54 is configured to select an optimal vibration force by adjusting the counterweight.
A control panel 62 for controlling the hopper 50 and the vibration motor 54 is provided on the front surface of the hopper 50. The control panel 62 is provided with a breaker, a selector switch, and the like.
The hydraulic cylinder 58 is controlled by a hydraulic line from the hydraulic unit 64.

  The ground improvement ship 12 includes a mobile station device 26 of GPS (Global Positioning System), uses this GPS, manages the position of the ground improvement ship 12 with an accuracy of 1 cm, and manages the water depth by the depth meter. In combination with data for digitizing the numerical values of the position of the ground improvement ship 12 and the agitating and mixing device 14 and the depth of the agitating and mixing device 14 in conjunction with the data for carrying out, the bottom soil improvement It is configured to manage the construction. The personal computer 28 includes a CPU (central processing unit), position control means for controlling the positions of the ground improvement ship 12 and the stirring and mixing device 14 by signals from the mobile station device 26, the elevation angle of the boom 32 of the transport device 16, and Elevation and turning angle control means for controlling the turning angle of the turntable 36, depth control means for controlling the depth of the stirring and mixing device 14 in conjunction with the depth meter, and storage means for storing software and data of the means The position of the ground improvement ship 12 and the stirring and mixing device 14 and the depth of the stirring and mixing device 14 are controlled.

  The stirring and mixing device 14 is formed by connecting three units 72 as shown in FIGS. Each unit 72 of this embodiment includes two stirring blades 74, and the apparatus as a whole provides a total of six stirring blades 74.

  Each unit 72 will be further described with reference to FIG. The unit 72 of the bottom soil mixing apparatus 10 includes a quadrangular cylindrical cage 76. The cage 76 holds each member described later and surrounds the periphery of the construction area. A motor 78 is installed on the wire mesh ceiling of the cage 76. For example, one end of a pipe-shaped rotating shaft 80 is suspended in the vertical direction and connected to the prime mover 78. The rotating shaft 80 is rotated around its central axis by the prime mover 78. An intermediate portion of the rotating shaft 80 is rotatably held by a bearing 82. The bearing 82 is fixed to the inner wall of the cage 76 via a crosspiece member 84.

  A stirring blade unit is connected to the lower end of the rotating shaft 80. The stirring blade 74 is provided so as to project around the lower end of the rotating shaft 80 in a direction substantially orthogonal to the central axis of the rotating shaft 80. The rotary shaft 80 has, for example, three blades, and the tips of the blades are surrounded by an annular member 86. The edge of the annular member 86 facing the water bottom is processed in a zigzag shape. Further, a space larger than the diameter of the seabed gravel is provided between the annular member 86 fixed to the tip of the stirring blade 74 and the inner wall of the cage 76. Thereby, when improving the bottom sediment of the seabed, gravel is sandwiched between the tip of the stirring blade 74 and the cage 76, and the rotation of the stirring blade 74 is not hindered. In this embodiment, an interval of 20 cm or more is provided between the stirring blades 74 and between the stirring blades 74 and the cage 76.

  The rotary shaft 80 of the stirring blade unit is provided with a high pressure water jet nozzle 88. The high-pressure water jet nozzle 88 is for jetting high-pressure water toward the bottom sediment while changing the jet direction of the high-pressure water by 360 ° as the rotary shaft 80 rotates. In this embodiment, the high-pressure water is ejected from the high-pressure water ejection nozzle 88, for example, approximately 45 ° obliquely downward with respect to the central axis of the rotating shaft 80. The high-pressure water is supplied to the high-pressure water jet nozzle 88 by a supply pipe provided in the rotary shaft 80. The supply is supplied from the supply pipe connected to the first hose 42 to the high-pressure water jet nozzle 88. It is made. The angle of the high-pressure water jet nozzle 88 can be selected appropriately to achieve the object of the present invention.

  A bowl-shaped protrusion 92 is provided at the lower end of the stirring blade unit. The projecting portion 92 is for piercing the bottom sediment of the water bottom and for positioning the bottom soil mixing device 10 during construction.

  A rectangular partition wall 90 that horizontally separates the depth direction is provided horizontally at the intermediate portion in the depth direction in the cage 76. The peripheral edge of the partition wall 90 is detachably fixed to a plurality of partition wall receivers 76a provided in the vertical direction at an appropriate interval on the inner wall of the cage 76 so that the distance from the lower end edge 76b of the cage 76 can be changed. It is configured. An annular gap 90 a is provided between the rotating shaft 80 penetrating the partition wall 90 and the partition wall 90. The gap 90 a is provided so that the rotation of the rotating shaft 80 is not hindered and water and air are circulated in the thickness direction of the partition wall 90. If the gap 90a is too large, the bottom material agitated and mixed at the time of construction leaks and contaminates the surrounding sea area. Therefore, the size of the gap 90a is minimized. The partition wall 90 is provided with a plurality of rectangular through holes 90b, and a filter member 94 is attached to the entire surface of the through holes 90b. The filter member 94 includes a rectangular frame 94a that is slightly larger than the rectangular through hole 90b, a mesh 94b attached to the upper edge of the frame 94a, and a mesh 94c attached to the lower edge. The water permeable mat 94d sandwiched between the meshes 94b and 94c is formed to drain and discharge water and air from the water permeable mat 94d and to remove contaminants. The water and air that have circulated through the through hole 90 b and the filter member 94 circulate out of the cage 76 through the wire mesh ceiling of the cage 76 and the through hole 76 c provided in the side wall of the cage 76. The water permeable mat 94d is formed by overlapping a plurality of cloth-like bodies made of knitted relatively thin synthetic fibers of polyamide.

  A through hole 90c is formed in the approximate center of the partition wall 90, and the second hose 48 is connected to the through hole 90c. And the sand sent by the jet water flow from the sand feeder 20 is supplied into the cage 76 under the partition wall 90.

Next, the bottom sediment mixing method using the bottom sediment mixing device 10 will be described with reference to FIGS.
This bottom soil mixing apparatus 10 is suitable for use in improving the habitat of shellfish such as clams and larvae, which are marine benthic animals.
First, the bottom soil mixing apparatus 10 moves the ground improvement ship 12 to the target construction water area based on the directions of the GPS, and reaches the target construction water area as shown in FIG. The stirring and mixing device 14 is put into seawater by the transport device 16.

The bottom soil to be improved (water sediment such as sediment) has a silt content of 80% or more, but the improved depth is 0.5 m, for example, that allows clams such as clams and snails to inhabit. In this case, the depth to be improved is 0.75 m, which is 1.5 times the depth at which shellfish can live. The depth to be improved is 1.5 times the depth at which the shellfish can live, but the depth to be improved is defined by the distance between the partition wall 90 and the lower edge 76b of the cage 76. Since the partition wall 90 is movable in the vertical direction, the partition wall 90 is appropriately moved up and down according to the depth to be improved.
First, according to GPS, the personal computer 28 moves the stirring and mixing device 14 to the center of the construction area, selects a spot according to the elevation angle of the boom 32 of the transport device 16 and the swing angle of the swivel base 36 of the hoist 30, and the transport device. 16 is operated, the wire 34 is extended, and the stirring and mixing apparatus 14 is immersed in seawater (step 1).

When the agitating and mixing device 14 reaches the seabed, the jet pump 40 of the water feeding device 18 is operated, water pressurized to high pressure is sent to the first hose 42, and high pressure water is ejected from the high pressure water ejection nozzle 88. And loosen the silt with a jet. Then, the silt is stirred by the stirring blade 74 while gradually lowering the stirring and mixing device 14 into the seabed (step 2).
By loosening the silt layer by the action of the water pressure and the stirring blade 74, the area subjected to the construction method is oxidized by the dissolved oxygen contained in the seawater and the stirring blade 74, and the chemical components of the sediment and the oxygen-free state are reduced. Improved.
Thereafter, the hoist 30 of the transport device 16 is operated, and the stirring and mixing device 14 is pulled up to near the surface of the bottom sediment.

On the other hand, the hydraulic line is operated to close the shutter 56 of the hopper 50 by actuating the hydraulic cylinder 58, and the sand is carried into the hopper 50 from the sand storage area 22 by the backhoe 24 and put in.
Next, the breaker of the power source is turned on, and the breaker of the control panel 62 of the hopper 50 is turned on.
Next, the jet pump 40 of the water feeder 18 is operated to supply high-pressure water from the first hose 42 to the second hose 48 via the manifold 46 and the high-pressure valve 44.
The selector switch of the control panel 62 of the sand feeder 20 is switched to operation, the hydraulic line is operated, and the shutter 56 of the hopper 50 is opened, whereby sand flows into the elbow 60. At this time, the vibration motor 54 is operated so that the sand descends downward by the vibration (step 3).

The sand feeding device 20 is actuated, and the sand is added to the lower region of the partition wall 90 in the stirring and mixing device 14 by the jet water flow flowing through the second hose 48, and the depth is such that clams such as clams and snails can live. The stirring and mixing device 14 is pushed down by rotating the stirring blade 74 up to 0.5 m to improve the particle size of the bottom sediment (step 4).
By this work, it becomes possible to improve the soil quality of the sediment having a silt content of 80% or more to the sediment having a particle size of 80% or more of the sand content.

If the bottom quality of one area is improved, the water feeding device 18 and the sand feeding device 20 are stopped, the conveying device 16 is moved, the stirring and mixing device 14 is pulled up from the seabed, and the conveying device 16 is placed in the next area. In operation, the stirring and mixing device 14 is submerged in the area of the seabed.
Then, the same operation as described above is repeated.

The depth measurement by the depth meter is performed by measuring the number of rotations of the drum 38 around which the wire 34 provided in the transport device 16 is wound, and measuring the length by which the wire 34 is lowered by the number of rotations. Since the depth of the stirring and mixing device 14 is measured and the personal computer 28 digitizes the depth and manages the depth, the improved depth confirmation management is accurate.
Moreover, the construction position can be managed with high accuracy by using GPS.
Also, sand loss is minimized because the sand is pumped into the stirring and mixing device 14 to fill the bottom and improve the bottom.

  By this method, the bottom sediment of the seabed is consolidated, stirred, and water pressure, the bottom sediment is inverted 180 degrees up and down to send oxygen, and the bottom sediment can be improved and improved even when the water depth is deep. It is possible and has excellent workability.

  In the stirring and mixing device 14, a partition wall 90 that vertically separates the depth direction of the cage is provided in the cage 76, and a high-pressure water jet nozzle 88 and a stirring blade 74 are disposed in a region surrounded by the cage 76, the partition wall 90, and the water bottom. Is placed. During construction of the bottom sediment mixing method, the high pressure water sprayed from the high pressure water jet nozzle 88 blows up the bottom sediment, and the blown up bottom sediment is mixed by the stirring blades 74, but the periphery of the construction area is caged. Since the upper part of the construction area is surrounded by the partition wall 90, the bottom sediment mixture hardly leaks into the surrounding sea area. In addition, since the periphery and upper part of the construction area are covered with the cage 76 and the partition wall 90, pressure is applied to the construction area due to the weight of the apparatus 10 during construction of the bottom sediment mixing method, and mixing is performed while increasing the density of the stirring mixture. Since it can stir, the efficiency of mixing stirring can be improved. Further, the stirring and mixing device 14 has a sufficient weight and is hardly affected by the ocean current.

1. The hoist ship 12a (70t (120t)) is equipped with a stirring and mixing device 14, a water feeding device 18, a hydraulic unit 64, and a generator, and a 500t loading vessel 12b is fed with sand, backhoe 24, and jet hopper 50. The apparatus 20 is loaded and installed.
2. The construction pattern is as follows.
1) Bottoming of stirring / mixing device 14 2) Start of improvement by jet injection by first hose 42 of water feeding device 18 and rotation of stirring blade of stirring / mixing device 14 (depth (thickness) to be improved is 0.5 m). Improvement time 3 minutes, 5 minutes, 7 minutes)
3) After completion of the improvement time, the spraying of the water feeding device 18 and the rotation of the stirring and mixing device 14 are stopped, and the stirring and mixing device 14 is pulled up until the lower end edge of the stirring and mixing device 14 reaches the vicinity of the bottoming surface. Switch to 48 jet water flow and throw sand (cage area (5m ² ) x depth (0.5m between partition wall and bottom edge)) 30% and 50% sand. Improvement rate 30% 50%) Addition is completed in about 1 to 2 minutes. 4) After completion of the addition, the stirring and mixing device 14 is started by improving the stirring and mixing device 14 (improvement time 3 minutes, 5 minutes and 7 minutes). Push down to the depth (thickness) to improve the stirring and mixing device 14 while rotating, and improve the bottom quality 5) After the improvement, return the stirring and mixing device 14 to the bottom position, and turn the stirring blades of the stirring and mixing device 14 on Stop and finish Table 1 shows the results of performing such enforcement with one area and six spots.

壱岐産砂を改良率３０％および５０％で投入、改良時間３分、５分、７分で底質地盤改良をしたところ、貝類の生息に適する砂分８０％以上に改良された。

Iki sand was introduced at an improvement rate of 30% and 50%, and when the soil quality was improved at 3 minutes, 5 minutes, and 7 minutes, the sand content improved to more than 80% suitable for shellfish habitat.

  The bottom soil mixing method and the apparatus according to the present invention can be applied mainly to the use of improving and recovering the fishing grounds for shellfish such as clams and Japanese larvae.

It is an illustration figure which shows the construction condition of the bottom sediment mixing method using a bottom sediment mixing apparatus. It is a top view solution diagram of a bottom ground mixing device. It is a front view solution figure of a sand feeder. It is a side view solution figure of a sand feeder. It is a top view solution figure which shows the state which connected three sand feeding apparatuses. It is a front illustration solution figure which shows the state which connected three sand feeding apparatuses. It is an illustration figure which shows the connection state of a hopper and a 2nd hose. It is a perspective view which shows an example of a stirring and mixing apparatus. It is a bottom view solution figure of a bottom sediment mixing device. (A) is a cross-sectional schematic view of a bottom soil mixing apparatus, and (B) is a partial cross-sectional schematic view of the apparatus. It is an illustration figure which shows the control method of a bottom ground mixing device. It is an illustration figure which shows the construction condition of the bottom sediment mixing method using a bottom sediment mixing apparatus. It is an illustration figure which shows the construction condition of the bottom sediment mixing method using a bottom sediment mixing apparatus. It is an illustration figure which shows the construction condition of the bottom sediment mixing method using a bottom sediment mixing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Bottom sediment mixing device 12 Ground improvement ship 12a Hoist ship 12b Barge 14 Stir mixing device 16 Transport device 18 Water feeder 20 Sand feeder 22 Sand storage area 24 Backhoe 26 GPS station mobile station device 28 Personal computer 30 Hoist 32 Boom 34 Wire 36 Swivel table 38 Drum 40 Jet pump 42 First hose 44 High pressure valve 46 Manifold 48 Second hose 50 Hopper 52 Frame 54 Vibration motor 56 Shutter 58 Hydraulic cylinder 60 Elbow 62 Control panel 64 Hydraulic unit 72 Unit 74 Stirring Blades 76 Cages 76a Bulkhead receptacles 76b Lower end edges 76c Through holes 78 Motors 80 Rotating shafts 82 Bearings 84 Crosspieces 86 Annular members 88 High pressure water jet nozzles 90 Bulkheads 90a Clearances 90b Through holes 90 Through hole 92 protrusion 94 filter member 94a frame 94b network (mesh)
94c Net (mesh)
94d Water permeable mat

Claims (6)

Surrounding the bottom of the bottom with a cage, such as sediment on the bottom of the bottom;
In a region in the cage, fluidizing a bottom such as sediment with a jet of water; and
Step 3 in which sand is pumped into the cage along with the water stream to the surface of a bottom such as sediment fluidized in the region within the cage;
Agitating and mixing the sand that has been pumped and a fluidized sediment or the like in a region within the cage to improve the particle size of the sediment or the like, and
Bottom sediment mixing method.   2. The bottom soil mixing method according to claim 1, wherein the step 4 includes agitating and mixing the sand pressure-fed by a water jet and the fluidized sediment with a stirring blade.   3. The step 3 according to claim 1 or 2, wherein after the cage in which the stirring blade is rotatably provided is pulled up to the vicinity of the bottom sediment surface of the water bottom, the sand is pumped into the partition wall in the cage. Bottom sediment mixing method.   The step 4 improves the particle size of the bottom sediment with the stirring blade while pushing down the cage having the stirring blade rotatably provided therein to a depth at which shellfish can live. The bottom sediment mixing method described in any of the above. An agitation and mixing device that reaches the bottom of the water and improves the agitation of the water bottom;
A transporting device for transporting the stirring and mixing device to a specific area of the bottom of the water;
A water feeding device for feeding water to the stirring and mixing device;
A sand feeding device for sending sand to the stirring and mixing device,
The stirring and mixing device includes a cage in which a stirring blade is rotatably provided,
The water feeding device is configured to fluidize water bottoms such as sediment on the bottom by jetting water, and to send sand sent by the sand feeding device to a stirring and mixing device by jet water flow. Constructed bottom sediment mixing device. The stirring and mixing device is provided with a partition wall that vertically separates the depth direction of the cage in the cage, and a high-pressure water jet nozzle and a stirring blade are disposed in a region surrounded by the cage, the partition wall, and the water bottom,
The partition is connected to a hose of a water feeding device and a sand feeding device, and is formed so that sand is pumped from the hose by a jet water flow,
The bottom sediment mixing device according to claim 5, wherein a hose of a water feeding device is connected to the high pressure water jet nozzle, and high pressure water is fed from the hose and jet sprayed.

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