Series of construction methods and dedicated work vessel for dredging, transportation, and unloading of soil to bottom of water or spreading work

Abstract

To solve the problem in which: greenhouse gas emissions are reaching record highs, and Japan's shallow bays are home to widespread deposits of sludge, which are a source of CO2 emissions; meanwhile, because large amounts of dredged soil are constantly being generated, environmental improvement projects are underway to improve water and bottom quality by making effective use of dredged soil; however, the economic viability of these projects cannot be ignored when expanding them as a global warming countermeasure.SOLUTION: A dedicated work vessel of this invention is a vessel for dredging, transporting, and unloading soil. A double-opening bottom slab of an extra-large bucket, equivalent to a mud bay of a soil transport vessel, opens 90 degrees to form a blade. During dredging, vibration pouring is performed in accordance with the speed at which the bottom slab closes to maintain the dredging depth at a tip of the blade, thereby drawing the bottom soil sandwiched between the blades into the bucket and finishing the dredged surface flat. The dedicated work vessel makes it possible to carry out large-scale dredging, transporting, and unloading of soil to the bottom of the water in a single operation without spreading pollution. The effect is environmental conservation, a significant shortening of construction time, and a significant reduction in project costs.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a construction method that includes a series of operations such as dredging, transporting, and discharging sediment onto the seabed or riverbed for expanding shipping lanes, berths, maintaining and deepening water depths in the seabed, riverbed, etc. of ships, and a dedicated work vessel used therefor. More specifically, it relates to the effective utilization of dredged sediment for sustainable development.

Background Art

[0002] Ports have supported the economic development of Japan, and their importance will not change in the future. As globalization of the world economy progresses, the trend towards larger container and bulk cargo transport ships has become established. In such a situation, in order to enable a global maritime transport network in Japan, it is essential to reorganize and expand port functions. Dredged sediment is generated along with the development and maintenance of shipping lanes and berths. During the period of high economic growth, dredged sediment was used for land reclamation as port-related and urban-related land in coastal areas. However, land reclamation in the current port area has been limited to what is essential from the perspective of industrial structure transformation and environmental considerations. For this reason, it has become an urgent issue to stably secure a disposal site for dredged sediment. In order to address such issues, the effective utilization of dredged sediment generated along with port improvement has been promoted.

[0003] On the other hand, the emissions of greenhouse gases that cause global warming have reached an all-time high and are causing climate change. Around the world, various damages and impacts have appeared on the natural environment and people's lives, and the term "climate crisis" has come to be used because of its severity. Today's climate change demands a decarbonized society without delay. Therefore, climate change policies are positioned as one of the top priorities. As global interest in climate change grows, Japan has announced a Carbon Neutral Port (CNP) policy. As a new measure against climate change in ports, measures such as a sand capping project (Sea Blue) that stably sequesters the organic carbon contained in seabed sediment by effectively utilizing dredged sediment are being implemented.

[0004] The ocean occupies three-fourths of the Earth's surface area, stores 97% of the Earth's water, and accounts for 99% of the living space on Earth in terms of volume. The ocean has absorbed approximately 30% of the carbon dioxide created by humans, mitigating the impact of global warming. However, the deterioration of coastal waters in recent years has become a source of carbon dioxide emissions rather than an absorption source. The carbon taken in as carbon dioxide by marine plants living in seaweed beds and other areas in coastal waters is called "blue carbon." In the transition to a decarbonized society, the carbon dioxide reduction effect of blue carbon is expected.

[0005] In Japan's closed sea areas and the like, with the increase in environmental load accompanying the concentration of population and industry, and the disappearance of tidal flats, shallow fields, etc. due to land reclamation, the loss of water purification functions is seen. In addition, there are countless large-scale submarine depressions where sediment has been mined for land reclamation materials. Due to the generation of oxygen-deficient water masses caused by these submarine depressions, red tides and blue tides are likely to occur continuously, and improvement of the water quality and sediment environment is required.

[0006] In Japan's inner bay and shallow sea areas, there are extensive sedimentary ground areas rich in organic matter, which are sources of carbon dioxide emissions. In addition, there are countless large-scale submarine depressions. The proposal here is the effective utilization of dredged sediment that is constantly generated in large quantities. Utilize high-quality dredged sediment to improve the water quality and sediment environment of the inner bay and shallow sea areas, and further expand blue carbon. Improving the growth and reproduction environment of seagrass and seaweed will lead to the expansion of blue carbon.

[0007] When using sediment as a covering material, filling material, embankment material, etc. on the seabed, the operator has the obligation to clarify that the sediment to be used is a valuable material rather than waste. The dredged sediment targeted here is high-quality and valuable. In addition, it is necessary to implement measures to prevent pollution diffusion. When discharging the sediment transported by a soil transport ship into a predetermined area on the seabed, a pollution diffusion prevention method using a double-pipe tremie pipe is known. (For example, refer to Patent Document 1)

[0008] As a measure against climate change, the utilization of dredged sediment includes covering soil (Seabule project), restoring the seabed topography by filling large-scale submarine depressions, and building artificial reefs on the seabed. The usual dredging and sediment removal methods involve dumping sediment not into disposal sites surrounded by landfill revetments, etc., but directly onto the seabed. For this reason, the use of pump dredgers that suck in sediment along with a large amount of water using pumps and drag suction dredgers (trailing suction hopper dredgers) is less common. Depending on the soil quality, the mud content is about 15%. Usually, grab dredgers or bucket dredgers are used. A grab dredger is a dredger that grabs and lifts the seabed sediment with a grab bucket and loads it onto the mud bin of its own ship or a soil transport ship moored alongside. Regarding the generation of pollution, turbidity occurs due to the lifting of sediment when cutting the seabed sediment from the seabed surface with a grab bucket, the diffusion of adhering soil when lifting it out of the water, and the sediment leaking from the bucket when lifting it to the water surface. A bucket dredger is a dredger that continuously excavates and lifts the seabed sediment by rotating a bucket line connecting a number of buckets and loads it onto a soil transport ship moored alongside. It is suitable for dredging a wide range of soil types from soft to hard, has features such as a flat dredging trace and good workability against wind and waves, and is mainly used for dredging navigation channels, berths, and rivers. Regarding the generation of pollution, it is almost the same as that of a grab dredger. Then, the sediment is transported by a soil transport ship, and sediment is dumped using a workboat equipped with a tremie pipe for sediment input. The tremie pipe method is a measure to prevent pollution diffusion by not directly dropping the dredged soil into the water. Currently, the critical path of the work processes of dredging work, transportation work, and seabed sediment dumping work is determined by the working time of the tremie pipe method.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] The present invention solves the problems of dredged sediment disposal sites and promotes measures to combat global warming. For example, it includes the elimination of carbon dioxide emission sources by covering floating mud and muddy ground in the inner bay and shallow sea areas with dredged sediment (Blue Sea Project), the improvement of water quality by filling large-scale submarine depressions, and the creation of shallow seaweed beds by building submarine embankments with dredged sediment to form seaweed beds that serve as carbon dioxide absorption sources. The creation of shallow seaweed beds involves enclosing the seabed with submarine breakwaters in areas where the sea depth exceeds the compensation depth for seaweed growth and building up the seabed with dredged sediment to a depth suitable for seaweed growth. With the formation of seaweed beds, a new growth environment for aquatic organisms is created. The creation of shallow seaweed beds uses dredged sediment as a material for building up the seabed and has significant advantages compared to the marine landfill disposal of dredged sediment. For example, marine landfill disposal is accompanied by the disappearance of natural coastlines, tidal flats, and seaweed beds in terms of the environment, and there are concerns about the deterioration of water quality and sediment due to changes in tidal currents. In terms of project costs, the construction costs of peripheral sea walls and the like are huge.

[0011] The improvement of water quality and sediment environment by re-evaluating high-quality dredged sediment as a valuable resource and the expansion of blue carbon projects must be sustainable development. Measures to combat global warming will not be effective unless they eliminate vast carbon dioxide emission sources and create vast carbon dioxide absorption sources. Projects to combat global warming are major projects. Problem 1 of the present invention is to take advantage of scale merits and significantly reduce project costs with new technologies. Problem 2 is that since dredging is carried out in waterways, berths, etc., the dredged surface should be finished flat. Problem 3 is that for dredging and the operation of discharging sediment to the seabed or spreading it, the measures to prevent pollution diffusion are effective. Means to be solved by the invention

[0012] Problem 1 is to significantly reduce operating costs. The solution is to streamline the processes of large-scale dredging, large-scale transportation, and large-scale sediment removal, and reduce operating costs by accelerating the processes with new technologies. Problem 2 is to achieve a flat finish for the dredged surface, and the solution is a new technology. Problem 3 is to prevent pollution diffusion. Pollution occurs because of fine clay particles and other suspended substances in the sediment, and these suspended substances float in the water. When a lump of sediment is thrown into the sea, it separates into finer pieces. The finer the pieces, the easier it is for the suspended substances to dissolve. Therefore, the pollution diffusion prevention measure is first to prevent the sediment from falling into the water. And it is to minimize the contact area between the sediment lumps and the water. The conventional dredging method causes pollution by breaking up the soil lumps.

[0013] The present invention is a construction method that combines a series of dredging, transportation, sediment dumping, or spreading operations for a large amount of underwater sediment, and a dedicated working ship for this construction method. The dedicated working ship is composed of a rectangular box-shaped bucket with a bottom plate that can be opened on both sides and is used for both dredging and transportation, a base ship with an inner space occupied by this bucket, and a lifting device for the bucket to move up and down in the underwater area below the inner space. The lifting device suspends the bucket with ropes connected to a plurality of winches on the base ship. In addition, a plurality of underwater vibration devices and a plurality of bottom plate opening and closing devices are installed on the bucket. When the bottom plate of the bucket is opened at a right angle, it becomes the blade of the bucket, and this bucket is vibrated and driven into the underwater ground in the blade state. The dredging method is that when the blade tip is vibrated and driven to the dredging depth, the bucket is vibrated and driven in accordance with the speed of closing the bucket bottom plate so as to maintain the depth of the blade tip, thereby taking the underwater ground (underwater sediment) inside the blade into the bucket and keeping the blade tip at the dredging depth to finish the dredged surface flat. It is a dedicated working ship used in a construction method that combines a series of dredging, transportation, sediment dumping, or spreading operations for a large amount of underwater sediment.

[0014] The dedicated working ship of the present invention is a bucket that combines dredging and transportation. The volume of the bucket enables it to be equivalent to the volume of the mud bin of a normal soil transport ship. That is, it is a super-large dredging that can also make the amount of dredged soil in one operation by the dedicated working ship equivalent to the amount of soil loaded in the mud bin of a normal soil transport ship. A number of winches are used for the lifting device of the bucket. However, since the dedicated working ship of the present invention has a structure that lifts the bucket inside the space of the mother ship, almost no eccentric load is generated due to the lifting load. This is very different from the grab dredger and bucket dredger that generate a large eccentric load, and the enlargement of the dedicated working ship is suppressed and the construction cost is reduced.

[0015] In addition, the dredging of the dedicated working ship of the present invention is carried out by closing the bottom plate of the bucket with the underwater ground. If only relying on winches for the energy to close the bottom plate, a large number of huge winches are required, and the cost performance is not good. Therefore, the dredging method of the present invention vibrates and drives the bucket in accordance with the speed of closing the bottom plate of the bucket so as to maintain the depth of the blade tip and also utilizes the ground reaction force. Thereby, the energy for closing the bottom plate becomes the combined energy of the power of the winch and the ground reaction force by the vibrating driving, ensuring reasonable dredging energy. The dedicated working ship of the present invention requires a number of winches, but they are ordinary winches.

[0016] Regarding the generation of pollution, the dredging by the dedicated working ship of the present invention is a dredging that does not break the lump of underwater soil and minimizes the contact surface between the lump of soil and water as much as possible. Therefore, the dedicated working ship of the present invention does not cause the upwelling of soil during the ground cutting of underwater soil from the seabed surface and the diffusion of adhering soil when pulling up in the water like a grab dredger or a bucket dredger. However, the dredging by the dedicated working ship of the present invention is not suitable for underwater ground with hard soil such as soft rock. In the case of such ground, it is necessary to crush it in advance. Although it is possible to increase the rigidity of the bucket of the present invention to be comparable to that of a grab bucket for soft rock, the cost performance is not good.

[0017] In the dedicated working vessel used in the construction method of the present invention, the dredging depth is determined by the depth of the blade tip, which is the bottom plate, in the soil. Therefore, the bottom plate width has a great influence on the dredging depth and the energy required to close the bottom plate. Considering these factors, the structure of the bucket is such that the longitudinal direction of the bucket is divided by a plurality of partition walls, and in accordance with the width of the divided bucket, the double-opening bottom plate is connected to the partition wall facing the outer peripheral wall at the front or rear of the bucket and the bottom of the opposing partition walls by a 90-degree movable hinge. And a double-opening bottom plate is provided for each of the plurality of divided buckets. It is a dedicated working vessel used in a construction method that includes a series of dredging work, transportation work, sediment discharging work to the underwater, or spreading work of a large amount of underwater sediment, characterized in that the width of the double-opening bottom plate is determined in consideration of the dredging depth and the energy required to close the bottom plate.

[0018] In the dedicated working vessel used in the construction method of the present invention, the lifting device constructs a three-dimensional portal frame structure on the pontoon, provides a plurality of fixed pulleys at regular intervals in this structure, and a rope is passed through the fixed pulleys to connect a plurality of winches on the pontoon and a plurality of lifting tools at the top end of the outer peripheral wall of the bucket and the free ends of the double-opening bottom plate that are paired with these winches. Then, it is characterized in that a plurality of winches are interlocked by controlling the tension of all the ropes to be constant to lift and lower and dredge the bucket. It is a dedicated working vessel used in a construction method that includes a series of dredging work, transportation work, sediment discharging work to the underwater, or spreading work of a large amount of underwater sediment.

[0019] In the dedicated working vessel used in the construction method of the present invention, the bucket structure is such that a double-opening bottom plate that also serves as a blade is connected to the bottom of the bucket by a 90-degree movable hinge. And the bottom plate opening and closing device vertically fixes two quarter-circular opening and closing auxiliary plates inside the bottom plate, further connects a rope to the lifting tool at the free end of the bottom plate, allows it to crawl in the groove of the arc of the opening and closing auxiliary plate, and connects it to the winch on the ship. The force to open the double-opening bottom plate is performed by the self-weight of the bottom plate and the opening and closing auxiliary plates and the rope operation of the winch on the ship. Also, the dredging of underwater sediment by the double-opening bottom plate opened at a right angle takes in the underwater sediment by rotating the double-opening bottom plate 90 degrees by the rope operation of the winch through the opening and closing auxiliary plates. As described above, the ground reaction force by vibration driving is utilized for the energy to close the double-opening bottom plate.

[0020] Here, the load direction of the underwater sediment on the double-opening bottom plate shifts from the horizontal direction to the vertical direction. In contrast, the tensile force of the winch rope for closing the bottom plate is vertically upward. The solution to this problem is the opening / closing auxiliary plate. The function of the opening / closing auxiliary plate is to convert the upward pulling force of the vertical winch into the force in the direction perpendicular to the free end of the bottom plate, smoothly corresponding to the shift in the load direction of the underwater sediment and securing the moment arm as the bottom plate width. It is a special working ship used in a series of construction methods for dredging, transporting, discharging sediment to the bottom, or spreading a large amount of underwater sediment, characterized by being equipped with such a bottom plate opening / closing device.

[0021] This is a series of descriptions of the processes of dredging work, transportation work, and sediment unloading work in the construction method of the present invention. In the dredging work of the said construction method, a bottom plate that also serves as a blade is lowered to the water bottom surface with it opened at a right angle. Next, the bucket is vibrated and driven into the underwater ground until the tip of the blade reaches the dredging depth. Then, the blade closes by utilizing the ground reaction force during driving in addition to the tensile force of the winch rope of the bottom plate opening and closing device. Here, by vibrating and driving the length of the blade in accordance with the speed of closing the bucket bottom plate so as to maintain the depth of the blade tip, the inner underwater ground (underwater sediment) sandwiched between the blades is taken into the bucket, and the dredging surface at the initial blade tip depth is finished flat. Next, the bucket is lifted to the position of the mother ship of the dedicated work vessel. At this time, the top end of the bucket is not lifted above the water surface. This is because the bucket does not have complete watertightness, and if it is lifted above the water surface, there is a risk of muddy water spilling out. Also, it is for making the sediment-loading bucket have an underwater weight by utilizing buoyancy. The next transportation work is to move the dedicated work vessel to the underwater sediment unloading position. The next sediment unloading work is to lower the bucket to the water bottom surface and lift the blade by the length of the blade in accordance with the speed of opening the bucket bottom plate, so as to unload sediment without separating the blade tip from the water bottom surface. The dedicated work vessel of the present invention combines dredging and transportation, and the volume of the bucket can be an extra-large size equivalent to the volume of the mud bin of a normal soil transport ship. Since it is a construction method that includes a series of large-scale dredging work, transportation work, and sediment unloading work to the underwater by such a dedicated work vessel, it is extremely efficient, greatly shortening the construction period and significantly reducing the business cost. The dredging surface is flat. Also, in the dredging work and sediment unloading work, the underwater sediment is not collapsed and not dropped underwater, so it is characterized by a high effect of suppressing pollution diffusion.

[0022] In the spreading operation of the construction method of the present invention, in the frontmost divided bucket of a dedicated working ship where the bucket is divided by a partition, both-opening bottom plates are opened at an angle corresponding to the spreading thickness of the earth and sand, and while keeping the free end of the bottom plate at the spreading depth of the earth and sand and advancing the dedicated working ship, the earth and sand up to the rearmost divided bucket are spread. It is a construction method that combines a series of dredging work, transportation work, and earth and sand spreading work on the underwater bottom. Note that the opening at an angle corresponding to the spreading thickness of the earth and sand is approximately equal to the spreading thickness, but there are differences depending on the soil quality. This will be corrected through actual implementation. Also, by keeping the free end of the bottom plate at the spreading depth of the earth and sand, an effect of suppressing the spreading of more excessive earth and sand is produced.

[0023] In the construction method of the present invention, when the surface layer of the underwater ground is soft and requires density increase, in this construction method, a rigid lid having a filter function is fixed to the upper surface of the bucket of the dedicated working ship used. And in the dredging process by this construction method, with the bottom plate also serving as the blade of the bucket opened at a right angle, it is vibrated and driven into the rigid lid of the bucket, and further, by continuously applying a dynamic compaction increasing load with the vibration load, the surface layer is rapidly consolidated and settled. If the required density increase is obtained, then, next, the bucket is pulled up by the length of the blade, and then, in accordance with the speed of closing the bucket bottom plate so as to maintain the depth of the blade tip, the length of the blade is vibrated and driven, thereby taking in the underwater ground inside the blade into the bucket and finishing the dredging surface at the original blade tip depth flat. It is a construction method that combines a series of dredging work, transportation work, earth and sand unloading work, or spreading work on the underwater bottom, characterized by increasing the density of the surface layer of the underwater ground with a vibration load.

[0024] In a construction method that includes a series of operations such as loading earth and sand from land, transporting it, and discharging earth and sand to the seabed using the dedicated working ship of the present invention, the earth and sand loading process involves loading earth and sand with the bottom plate of the bucket lifted above the water surface. This is to prevent the water accumulated inside the bucket from falling into the water. Next, a pollution diffusion prevention sheet is spread on the upper surface of the bucket, and then the bucket is gently lowered to just below the water surface in the transportation state and fixed in position. The next transportation operation is to move the dedicated working ship to the position where the earth and sand are discharged to the seabed. In the next earth and sand discharging process, the bucket is lowered to the seabed surface, and the blade tip is lifted by the length of the blade in accordance with the speed of opening the bottom plate of the bucket, so that the earth and sand are discharged without the blade tip leaving the seabed surface. In the loading and unloading of earth and sand, the occurrence of pollution is suppressed by minimizing the contact surface between the earth and sand and water by minimizing the falling of earth and sand into the water as much as possible. A construction method that includes a series of operations such as loading earth and sand from land, transporting it, and discharging earth and sand to the seabed. Note that the earth and sand mainly refer to earth and sand and stone materials used as materials for submerged breakwaters constructed on the seabed in the shallow sea area construction project of the seaweed bed. Effects of the invention

[0025] The dedicated working ship of the present invention is used for both dredging and transportation, and the volume of its bucket is extremely large to be equivalent to the volume of the mud bin of a normal earth transport ship. When the double-opening bottom plate of the extremely large bucket is opened 90 degrees, the bottom plate becomes the blade. The dredging method using the dedicated working ship is to vibrate and drive the bucket to the dredging depth of the seabed ground, and vibrate and drive the bucket in accordance with the speed of closing the bottom plate of the bucket so as to maintain the depth of the blade tip, thereby taking the inner seabed ground sandwiched between the blades into the bucket and finishing the dredging surface flat by keeping the blade tip at the dredging depth. The dedicated working ship equipped with the extremely large bucket enables a series of large-scale dredging work, transportation work, and earth and sand discharging work to the seabed of the underwater soil and sand. The effect is to provide a construction method and a dedicated working ship that result in a significant shortening of the construction period and a large reduction in the project cost.

[0026] The dredging of the extra-large bucket is carried out by closing the double-opening bottom plate. At this time, the load direction of the underwater soil and sand applied to the bottom plate shifts from the horizontal direction to the vertical direction. In contrast, the pulling force of the winch rope for closing the bottom plate is vertically upward, and the solution to this is the opening and closing auxiliary plate. The function of the opening and closing auxiliary plate is to convert the upward pulling force of the winch in the vertical direction into the force in the direction perpendicular to the free end of the bottom plate, so as to smoothly respond to the shift of the load direction of the underwater soil and sand and ensure the moment arm as the bottom plate width. The function of this opening and closing auxiliary plate plays a decisive role in the dredging of the extra-large bucket.

[0027] Moreover, if the energy for closing the bottom plate depends only on the winch, a large number of huge winches are required, and the cost performance is not good. Therefore, the dredging method of the present invention vibrates and drives the bucket in accordance with the speed of closing the bucket bottom plate so as to maintain the depth of the blade tip, and also utilizes the ground reaction force at this time. Thereby, the energy for closing the bottom plate becomes the combined energy of the power of the winch and the ground reaction force by vibration driving, ensuring reasonable dredging energy, and playing a great role in the dredging of the extra-large bucket.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying out the Invention

[0029] The embodiments of the present invention will be described below with reference to FIGS. 1 to 7.

[0030] The dedicated working ship 1 of the present invention is composed of a rectangular box-shaped bucket 2 with a bottom plate 23 that can be used for both dredging and transportation and is double-opening, a base ship 3 with an inner space occupied by this bucket 2, and a lifting device for the bucket to move up and down in the underwater area below the inner space. The lifting device suspends the bucket 2 with ropes 61 connected to a plurality of winches 6 on the base ship 3. In addition, a plurality of underwater vibration devices 4 and a plurality of bottom plate opening and closing devices 5 are installed on the bucket 2. FIG. 1 is a side view of the dedicated working ship of the construction method of the present invention. FIG. 2 is a plan view of the same. FIG. 3 is a vertical cross-sectional view in the short side direction (A-A in FIG. 1) of the same. FIG. 4 is a vertical cross-sectional view in the long side direction (B-B in FIG. 2) of the same. In the figures, 1 is the dedicated working ship of the construction method of the present invention, 2 is the bucket, 21 is the divided bucket, 22 is the outer peripheral wall of the bucket, 23 is the double-opening bottom plate of the bucket, 241 is the partition wall where the bottom plate is connected to the bottom, 242 is the partition wall where the rope guide is vertically attached, 3 is the base ship, 31 is the three-dimensional portal structure, 32 is the fixed pulley, 4 is the underwater vibration device, 5 is the bottom plate opening and closing device, 51 is the opening and closing auxiliary plate, 6 is the winch, 61 is the rope, 7 is the water surface, 8 is the water bottom surface, and 9 is the underwater ground or underwater sediment. The bottom plate opening and closing device 5 vertically fixes two quarter-circular opening and closing auxiliary plates 51 inside the bottom plate 2, further connects the rope 61 to the hanging tool at the free end of the bottom plate 23, makes it crawl in the arc groove of the opening and closing auxiliary plate 51, and connects it to the winch 6 on the ship. The bottom plate opening and closing device 5 is not shown in the drawing.

[0031] As shown in FIGS. 2 to 4, in the inner space of the pontoon 3 which is the floating body of the dedicated working ship 1, there is arranged an ultra-large bucket 2 which serves both for dredging and transportation. The bucket 2 is suspended by a rope 61 passed through a fixed pulley 32 of a three-dimensional portal frame structure 31 constructed on the pontoon 3. This rope 61 connects a plurality of winches 6 on the pontoon 3 and a plurality of suspension tools at the top ends of the outer peripheral wall 22 of the bucket 2 and the free ends of the both-opening bottom plates 23 which are paired with the winches 6. Then, the plurality of winches 6 are interlocked to raise and lower the bucket 2 by controlling so that the tensions of all the ropes 61 become constant. However, there are two types of winches 6. The winch 6 described with reference to the drawings is for the power to close the both-opening bottom plate 23 to take in the underwater soil and sand 9 into the bucket 2 during dredging of the bucket 2, and to lift the taken-in underwater soil and sand 9 to the position of the pontoon 3 with the bucket 2. On the other hand, a winch 6 for the power to suspend the weight equivalent to the self-weight of the bucket 2 is separately required. This winch 6 is omitted because the drawing becomes complicated. (Details will be described later.)

[0032] The width of the bottom plate 23 of the bucket 2 greatly affects the dredging depth and the energy for closing the bottom plate 23. Considering these, the structure of the bucket 2 is such that its longitudinal direction is divided by a plurality of partition walls 241, and the both-opening bottom plate 23 is connected to the partition wall 241 facing the outer peripheral wall 22 in the front or rear of the bucket 2 and the bottom portions of the opposing both partition walls 241 by 90-degree movable hinges in accordance with the width of the divided bucket 21. And the both-opening bottom plate 23 is provided for each of the plurality of divided buckets 21. The number of the divided buckets 21 shown in FIGS. 2 and 4 is 12. Note that there are two types of partition walls, i.e., partition walls 241 and 242. (Details will be described later.)

[0033] FIG. 5 is a vertical cross-sectional view showing the double-opening bottom plate 23 of the bucket 2 opened by 90 degrees to form a blade shape and vibration-driven into the underwater ground 9. When dredging the underwater ground 9 with the bucket 2, the double-opening bottom plate 23 also serving as a blade is lowered to the water bottom surface with the two plates opened at a right angle. The power for opening the bottom plate 23 is the self-weight of the bottom plate 23 and the two opening / closing auxiliary plates 51 fixed perpendicularly thereto. The bottom plate 23 generates an eccentric load due to the opening / closing auxiliary plates 51 and becomes vertical and opens at a right angle. At this time, the bucket 2 cannot be suspended by the winch 6 which serves as the power for closing the bottom plate 23. Therefore, a separate winch 6 for power to suspend an equivalent of the self-weight of the bucket 2 is required.

[0034] FIG. 6 is an explanatory view of a dredging operation for flattening the dredging surface by the bucket 2 of the present invention. This figure shows one of the divided buckets 21 shown in FIGS. 4 and 5 taken out. In the figure, 25 is a 90-degree movable hinge and 10 is the dredging depth. The method of dredging to flatten the dredging surface is to open the bottom plate 23 by 90 degrees to form a blade shape and vibrate and drive it by a length equivalent to the blade while closing the blade (bottom plate 23) so as to maintain the depth at the blade tip. Thereby, the inner underwater ground 9 (underwater sediment) sandwiched by the blade is taken into the bucket 2, and the dredging surface, which is the initial blade tip depth, is finished flat. Here, the opening / closing auxiliary plate 51 functions effectively. (Details will be described later) FIG. (a) shows a state where the bucket 2 is in a blade shape and the blade is vibration-driven into the underwater ground 9. FIG. (c) shows a state where the blade is rotated by 90 degrees to close the bottom plate 23. FIG. (b) is an intermediate state between them. While transitioning from FIG. (a) to FIG. (c), the vibration driving of the bucket 2 continues. And the rope 61 suspending an equivalent of the self-weight of the bucket 2 has the rope 61 of a length equivalent to the blade fed out from the winch 6. On the other hand, the winch 6 for closing the bottom plate 23 to take the underwater sediment 9 into the bucket 2 winds up the rope 61 by a length equivalent to the arc length of the opening / closing auxiliary plate 51. The figure shows a line of the dredging depth 10. The blade tip depth is controlled to always coincide with the line of the dredging depth 10.

[0035] Figure 7 is a functional explanatory diagram of the opening / closing auxiliary plate 51 of the double-opening bottom plate 2. In the figure, F1 is the vibration driving force, F2 is the tensile force of the rope 61 of the winch 6, R1 is the load of the underwater soil and sand 9, and R2 is the ground reaction force against the vibration driving force. The dredging of the bucket 2 is performed by closing the double-opening bottom plate 23. The energy for closing the bottom plate 23 is F2 and R2, and it is sufficient if F2 + R2 > R1 holds. As described above, vibration driving is performed by the length of the blade in accordance with the closing speed of the blade (bottom plate 23) so as to maintain the depth of the blade tip. At this time, the direction of the load R1 of the underwater soil and sand 9 applied to the bottom plate 23 changes. In FIG. 6, in FIG. (a), the bucket 2 is in a blade state and the blade is vibration-driven. Then, it is assumed that the moment when the bucket 2 starts to close. The direction of the load R1 of the underwater soil and sand 9 is horizontal. FIG. (c) shows the moment when the bucket 2 is closed by the tensile force F2 of the rope 61 of the winch 6. The direction of the load R1 is vertical. FIG. (b) is in the middle of these. The direction of the load R1 shifts from horizontal to vertical. On the other hand, the tensile force of the rope 61 of the winch 6 for closing the bottom plate 23 is vertically upward. The solution to this is the opening / closing auxiliary plate 51. Its function is to smoothly respond to the shift in the direction of the load R1 of the underwater soil and sand 9 by converting the upward pulling force of the winch 6 in the vertical direction into the force in the perpendicular direction of the free end of the bottom plate 23, and to secure the moment arm as the width of the bottom plate 23. Incidentally, the power of the winch 6 is reduced by the amount of the generated ground reaction force R2. The harder the underwater ground, the greater the energy for closing the bottom plate 23, but the ground reaction force R2 also becomes larger.

[0036] As confirmed in FIG. 7, there are two types of partition walls: the partition wall 241 to which the bottom plate 23 is hinge-connected, and a different partition wall 242. The rope 61 for transmitting F2 is connected to the winch 6 on the ship by being coupled to the hanging tool at the free end of the bottom plate 23 and running in the arc groove of the opening / closing auxiliary plate 51. This rope 61 requires a rope guide so as not to deviate from the groove of the opening / closing auxiliary plate 51, and the partition wall 242 is used to vertically attach this. Further, the tensile force F2 is used not only for closing the bottom plate 23 but also as the main force for pulling up the bucket 2 that has taken in the underwater ground 9 to the pontoon 3. A support member for transmitting F2 at the free end of the bottom plate 23 to the bucket 2 is fixed to the partition wall 242.

Description of Symbols

[0037] 1 Special working ship for the construction method of the present invention 2 Buckets 21 Split buckets 22 Outer peripheral wall of the bucket 23 Double-opening bottom plate of the bucket 241 Partition where the bottom plate is connected to the bottom 242 Partition where the rope guide is vertically installed 25 90-degree movable hinge 3 Mother ship 31 Three-dimensional portal structure 32 Fixed pulley 4 Submerged vibration device 5 Bottom plate opening and closing device 51 Opening and closing auxiliary plate 6 Winch 61 Rope 7 Water surface 8 Seabed surface 9 Seabed ground or seabed soil and sand 10 Dredging depth F1 Vibration driving force F2 Tensile force of the winch rope R1 Load of seabed soil and sand R2 Ground reaction force against the vibration driving force

Claims

1. In a special working ship used for a construction method that includes a series of dredging work, transportation work, sediment discharging work to the bottom of the water, or spreading work of a large amount of underwater soil and sand, the special working ship is composed of a rectangular box-shaped bucket with a bottom plate that is both openable and used for both dredging and transportation, a pontoon with an inner space occupied by this bucket, and a lifting device for the bucket to move up and down in the underwater area below the inner space. The lifting device suspends the bucket with ropes connected to a plurality of winches on the pontoon. A plurality of underwater vibration devices and a plurality of bottom plate opening and closing devices are installed on the bucket. When the bottom plate of the bucket is opened at a right angle, it becomes the blade of the bucket. This bucket is vibrated and driven into the underwater ground in the blade state. The dredging method is that when the blade tip is vibrated and driven to the dredging depth, the bucket is vibrated and driven in accordance with the speed of closing the bucket bottom plate so as to maintain the depth of the blade tip, thereby taking the inner underwater ground sandwiched between the blades into the bucket and finishing the dredging surface flat by maintaining the dredging depth at the blade tip. A special working ship used for a construction method that includes a series of dredging work, transportation work, sediment discharging work to the bottom of the water, or spreading work of a large amount of underwater soil and sand.

2. In the special working ship used for the construction method of Claim 1, since the dredging depth is determined by the soil depth at the blade tip which is the bottom plate, the width of the bottom plate greatly affects the dredging depth and the energy for closing the bottom plate. Considering these factors, the structure of the bucket is to divide the longitudinal direction of the bucket with a plurality of partition walls, and according to the width of the divided bucket, connect the double-opening bottom plate to the partition wall facing the front or rear outer wall of the bucket and the bottom of the two facing partition walls with a 90-degree movable hinge, and provide a double-opening bottom plate for each of the plurality of divided buckets. A special working ship used for a construction method that includes a series of dredging work, transportation work, sediment discharging work to the bottom of the water, or spreading work of a large amount of underwater soil and sand.

3. In the dedicated working vessel used in the construction method of Claim 1, the lifting device constructs a three-dimensional portal frame structure on the pontoon, provides a plurality of fixed pulleys at regular intervals in this structure, and passes ropes through the fixed pulleys to connect with a plurality of lifting tools at the top end of the outer peripheral wall of the bucket paired with a plurality of winches on the pontoon and at the free ends of both opening bottom plates. By controlling so that the tensions of all the ropes become constant, the plurality of winches are interlocked to lift and dredge the bucket, and it is a dedicated working vessel used in a construction method that includes a series of dredging work, transportation work, sediment discharging work to the bottom of the water, or spreading work of a large amount of underwater sediment.

4. In the dedicated working vessel used in the construction method of Claim 1, the bucket structure is one in which both opening bottom plates also serving as blades are connected to the bottom of the bucket by a 90-degree movable hinge, and the bottom plate opening and closing device vertically fixes two quarter-circular opening and closing auxiliary plates inside the bottom plate. Further, a rope is connected to the lifting tool at the free end of the bottom plate and made to crawl in the groove of the arc of the opening and closing auxiliary plate and connected to the winch on the ship. The opening of both opening bottom plates is performed by the self-weight of the bottom plate and the opening and closing auxiliary plates and the rope operation of the winch on the ship. Also, the dredging of underwater sediment by the both opening bottom plates opened at a right angle takes in the underwater ground by rotating the both opening bottom plates 90 degrees by the rope operation of the winch through the opening and closing auxiliary plates. Regarding the problem that the load direction of the underwater sediment applied to the both opening bottom plates at this time shifts from the horizontal direction to the vertical direction, the function of the opening and closing auxiliary plate converts the vertical pulling force of the winch into the force in the perpendicular direction of the free end of the bottom plate, and secures the moment arm as the bottom plate width. It is a dedicated working vessel used in a construction method that includes a series of dredging work, transportation work, sediment discharging work to the bottom of the water, or spreading work of a large amount of underwater sediment, characterized by being equipped with such a bottom plate opening and closing device.

5. In the construction method of claim 1, in the dredging work of the construction method, a bottom plate also serving as a blade is lowered to the water bottom surface with the bottom plate opened at a right angle. Next, the bucket is vibration-driven into the underwater ground until the tip of the blade reaches the dredging depth. Then, the blade closes by using the ground reaction force during driving in addition to the tensile force of the rope of the winch of the bottom plate opening / closing device. Here, by vibration-driving by the length of the blade in accordance with the closing speed of the bucket bottom plate so as to maintain the depth of the blade tip, the inner underwater ground sandwiched between the blades is taken into the bucket, and the dredging surface at the initial blade tip depth is finished flat. Next, the bucket is lifted to the position of the mother ship of the dedicated work ship. The next transportation work is to move the dedicated work ship to the position for discharging underwater sediment. The next sediment discharging work is to discharge sediment without separating the blade tip from the water bottom surface by lifting the blade by the length of the blade in accordance with the opening speed of the bucket bottom plate when the bucket is lowered to the water bottom surface. Further, the dedicated work ship of the present invention combines dredging and transportation, and the volume of the bucket is extremely large, equivalent to the volume of the mud bin of a normal soil transport ship, so it is extremely efficient, greatly reducing the construction period and significantly reducing the operating cost. It is characterized by flattening the dredging surface and having a high effect of suppressing the spread of pollution in the dredging work and the sediment discharging work. It is a construction method that includes a series of dredging work, transportation work, and sediment discharging work to the underwater of a large amount of underwater sediment.

6. In the spreading work of the construction method of claim 1, the double-opening bottom plate is opened from the foremost divided bucket in which the bucket of the dedicated work ship is divided by a partition at an angle corresponding to the spreading thickness of the sediment, and while keeping the free end of the bottom plate at the spreading depth of the sediment and advancing the dedicated work ship, the sediment up to the rearmost divided bucket is spread. It is a construction method that includes a series of dredging work, transportation work, and sediment spreading work to the underwater of a large amount of underwater sediment.

7. In the construction method of Claim 1, when the surface layer of the underwater ground is soft and requires density increase, the construction method fixes a rigid lid with a filtering function on the upper surface of the bucket of the dedicated working ship used. In the dredging process by this construction method, a bottom plate that also serves as a blade of the bucket is vibrated and driven to the rigid lid of the bucket with the blade opened at a right angle. Further, by continuously applying a dynamic compaction increasing load with the vibration load, the surface layer is rapidly consolidated and settled. When the required density increase is obtained, next, the bucket is lifted by the length of the blade, and then, in accordance with the speed of closing the bucket bottom plate so as to maintain the depth of the blade tip, the length of the blade is vibrated and driven, thereby taking the inner underwater ground sandwiched between the blades into the bucket and finishing the dredging surface at the initial blade tip depth to be flat. A construction method that combines a series of dredging work, transportation work, underwater soil discharge work, or spreading work of a large amount of underwater soil and sand, characterized by increasing the density of the surface layer of the underwater ground with a vibration load.

8. In the construction method that combines a series of loading work, transportation work, and underwater soil discharge work of soil and sand from land using the dedicated working ship of Claim 1, in the loading process of soil and sand, the soil and sand are loaded with the bottom plate of the bucket lifted above the water surface. Next, a pollution diffusion prevention sheet is spread on the upper surface of the bucket. Next, the bucket is gently lowered to just below the water surface in the transportation state and fixed in position. The next transportation work is to move the dedicated working ship to the underwater soil discharge position. The next soil discharge process is to lower the bucket to the water bottom surface and lift the length of the blade in accordance with the speed of opening the bucket bottom plate, thereby discharging the soil without separating the blade tip from the water bottom surface. In the loading and unloading of soil and sand, the generation of pollution is suppressed by minimizing the underwater fall of the soil and sand as much as possible and minimizing the contact surface between the soil and sand and water. A construction method that combines a series of loading work, transportation work, and underwater soil discharge work of soil and sand.

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