Thin layer sand cover construction method, sand cover work ship, sand cover replenishment bucket, and sand cover unloading bucket

Abstract

To solve the problem in which, even though an ideal thin layer sand cover construction method is to suppress generation of pollution and inroads of sand cover into a water bottom ground as much as possible, to maintain the planned shape and state of the thin layer sand cover, and to construct the thin layer sand cover in a short time, however, a thin layer sand cover construction method at present is at the stage of intending the suppression of generation of the pollution and spreading out the sand uniformly.SOLUTION: In the solution of this invention, formation of a thin layer sand cover is performed which secures the constitution of sand cover, a sand cover thickness and a density state that are plan requirements in a sand cover unloading bucket beforehand, on the ship of a sand cover work ship. Then, the bucket loading the formation sand cover is lowered to the water bottom and is landed calmly, the bucket is raised to a height of the sand cover thickness and an automatic opening / closing type bottom slab is opened at the same time, and the formation sand cover is unloaded calmly. In this method, the thin layer sand cover is constructed in a short time without a substantial underwater fall of the formation sand cover, while maintaining the shape and state of the sand cover and also suppressing the generation of pollution.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a thin layer sand capping method, which is the main method for purifying bottom sediment environments such as the seabed, and to a sand capping work vessel, a sand capping material supply bucket, and a sand capping material loading and unloading bucket used for this method. [Background technology]

[0002] Today, climate change caused by global warming has made it imperative to move towards a decarbonized society. SDG 13 calls for concrete measures to combat climate change, and SDG 14 calls for protecting and sustaining the life of the oceans and seas. Seaweed beds have been shown to reduce carbon dioxide emissions, purify water, and contribute to marine products. Carbon absorbed as carbon dioxide by marine plants living in seaweed beds is called "blue carbon," and the diverse effects of blue carbon are attracting attention.

[0003] Sludge-filled seabeds are widespread in Japan's coastal waters. Sludge-filled waters are carbon dioxide emitters. On the other hand, coastal waters with vegetation, such as seagrass beds, are carbon dioxide sinks. Converting sludge-filled coastal waters into vegetated coastal waters would significantly contribute to climate change countermeasures. Bottom sediment improvement is necessary to transform these sludge-filled seabeds into seaweed beds. Current bottom sediment improvement methods include dredging and sand capping. Bottom sediment improvement intended to combat climate change is a large-scale project. To ensure sustainability, cost-effectiveness must be considered while also taking the environment into account. Large-scale projects using current construction methods, such as dredging, face a shortage of final disposal sites. In any case, a major challenge is how to utilize the economies of scale of large-scale projects to improve cost-effectiveness. Against this social and environmental backdrop, the "Tenchi-gaeshi" method has been invented as a new technology for remediating seabed and other bottom sediment environments.

[0004] The "top-and-bottom turning" method involves turning over the bottom of the waterbed, replacing the poor soil layer on the surface with a good soil layer underneath. A major feature of this bottom sediment improvement method is that it can be completed within the improvement work area alone. In other words, unlike the dredging method, there is no need to transport bottom mud outside the work area. Also, unlike the soil covering method, there is no need to transport soil covering material from outside the work area. This method does not require the main steps of conventional bottom sediment improvement methods. As a result, the construction costs of bottom sediment improvement are significantly reduced. The significant reduction in project costs makes it possible to realize sustainable climate change countermeasure projects. (See Patent Document 1, pending application)

[0005] The principle of environmental improvement by turning the tandchi over is the same as that of sand-capping. In other words, by sealing the sludge with a lower layer of good soil instead of sand and preventing direct contact between the seawater and the sludge, harmful chemical components or nutrients that had been leaching from the seabed sludge into the seawater are suppressed. As eutrophication progresses, large amounts of red tide plankton appear, eventually dying and sinking, becoming sludge and accumulating on the seabed. Bacteria then actively decompose the organic matter in the sludge, consuming large amounts of dissolved oxygen in the water in the process, causing the bottom water to become oxygen-depleted. This vicious cycle continues. Sand-capping is intended to maintain good water quality and aquatic ecosystems in the aquatic area.

[0006] Sand-capping methods tend to use thin layers of sand, minimizing the thickness required, in order to reduce public works costs and conserve sand-capping materials. A common challenge in thin-layer sand-capping is achieving uniform and accurate sand thickness. Furthermore, minimizing contamination during construction is essential, especially if the bottom soil is contaminated. The thinner the sand, the more advanced the technology and management required. Traditionally, sand-capping materials were dumped directly from the water surface using backhoes or grab boats. However, in recent years, slit dumping has been implemented, which uses slits in the pollution prevention frame to reduce the impact of the dumping of the sand. Furthermore, a blind sand-capping method has been developed to improve the accuracy of sand thickness. This method involves installing a blind sand-capping device on the side of a sand-spreading barge, spreading and leveling sand in the device, and then opening the bottom of the device to perform sand-capping, aiming to achieve uniform sand-capping. A further development of this method is the slurry-type blind sand-capping method. This involves lowering a blind sand-capping device directly above the sand-capping location in the water, spreading the sand sent in a slurry form evenly over the device, reducing the occurrence of contamination when the sand falls and ensuring that the sand is reliably covered in the designated position (see Non-Patent Document 1). [Prior art documents] Patent applications pending

[0007] Patent application pending 1 Application date: February 5, 2024, Applicant name: Masayoshi Kondo Non-patent literature

[0008] [Non-Patent Document 1] Civil Engineering and Construction Technology Symposium 2003 Proceedings pp.61-68, 2003, Japan Society of Civil Engineers, Thin layer sand covering technology on contaminated bottom sediment "Slurry type blind sand covering method" Summary of the Invention [Problem to be solved by the invention]

[0009] Based on the cost-effectiveness of the Tenchi-gaeshi method, it has been estimated that the economic limit for the depth of Tenchi-gaeshi is 2.5 m. If a 50 cm thick covering soil is ensured, the limit for the sludge layer thickness is 2.0 m. In water areas with a sludge layer thickness greater than this, the Tenchi-gaeshi method becomes less cost-effective. Therefore, the challenge of this invention is to develop a thin layer of sand covering method that covers the Tenchi-gaeshi method in water areas with thick sludge layers, and to determine how to utilize the economies of scale of large-scale projects such as climate change countermeasure projects to increase cost-effectiveness and make the project environmentally friendly and sustainable.

[0010] An ideal thin layer sand capping method is one that minimizes the occurrence of pollution and the sinking of the sand into the bottom ground, maintains the planned shape and state of the thin layer sand, and constructs the thin layer sand in a short time. Conventional thin layer sand capping methods involve directly pouring the sand capping material from the water surface using a backhoe, clamshell bucket, etc. It is technically extremely difficult to spread a thin layer evenly with this method. Therefore, new thin layer sand capping methods have been developed. However, these are only at the stage of suppressing the occurrence of pollution and spreading the sand evenly. The objectives of the present invention are to minimize the occurrence of pollution and sinking of the sand in large-scale bottom sediment improvement using thin layer sand capping, maintain the planned configuration and shape of the sand capping, ensure the planned density of the sand capping, and construct the thin layer sand in a short time. Means that the invention aims to solve

[0011] The solution of this invention involves forming a thin layer of sand that meets the planned requirements in a sand-capping bucket aboard a sand-capping work vessel. That is, the thin layer of sand is formed while ensuring the planned sand-capping configuration, sand-capping thickness, and sand-capping density. Here, the sand-capping configuration assumes the use of multiple sand-capping materials with different effects. The bucket loaded with the formed sand is then gently lowered to the bottom of the water where the sand is to be covered, and the automatic opening and closing base plate is gently opened as the bucket is raised to the sand-capping height, and the formed sand is gently unloaded. The gentle landing and unloading of the bucket are intended to minimize pollution and sinking, and to maintain the planned sand-capping configuration, sand-capping shape, and sand-capping density. The size of the largest sand-capping unloading bucket is comparable to the mud shed of a typical soil-carrying vessel. This makes it possible to accommodate large-scale projects such as climate change countermeasures. Furthermore, miniaturizing the sand-capping work vessel would also be extremely effective in improving river bottom sediment by covering the sand.

[0012] The method of this invention is a sand-capping method that involves a series of steps on board, including the formation of sand capping that meets pre-planned requirements and the bottom loading and unloading of the formed sand capping. The main components of the sand-capping work vessel used in this method are a sand-capping unloading bucket, a barge with an opening for the bucket to ascend and descend, a barge integrated with the opening, a three-dimensional support column and lifting device for suspending the bucket, and a hopper-type sand-capping material supply bucket and an overhead crane for the bucket attached to the three-dimensional support column. The essential sand-capping unloading bucket has a box-shaped structure with an open top, and the bottom of the bucket is divided into a grid pattern by vertical plates, with an automatic opening and closing bottom plate connected by a hinge to match the width of one of the sections. The barge with an opening for the bucket to ascend and descend is two barges arranged side by side with a predetermined opening, rigidly joined together by a three-dimensional support column.

[0013] The sand-capping work vessel's sand-capping unloading bucket is suspended from a three-dimensional support column by a rope connected to the lifting winch of the lifting device on the barge. The sand-capping material supply bucket is a sand-capping material supply device that can be reciprocated along the entire length of the sand-capping material unloading bucket using an overhead crane installed on the three-dimensional support column. The thin-layer sand-capping method of the present invention is characterized in that the sand-capping material supply bucket reciprocates along the entire length of the sand-capping unloading bucket to systematically scatter sand. The sand-capping unloading bucket loaded with molded sand that meets the planned requirements is then lowered through the open space of the barge to the bottom of the water, where it gently lands. The bucket is then raised to the height of the sand-capping thickness, and the automatically opening and closing bottom slab opens in tandem with this lifting, allowing the molded sand to be gently unloaded. This prevents pollution caused by floating mud. Furthermore, the landing of the sand-capping unloading bucket provides a simple preload, reducing the sinking of the molded sand. Furthermore, the molded sand falls from zero to the width of the bottom slab, meaning that it essentially does not fall into the water. This is extremely important. This suppresses the occurrence of pollution at this stage and maintains the planned shape and state of the thin layer of sand capping. Furthermore, the thin layer sand capping method of the present invention is a thin layer sand capping method that combines the sand capping molding process and the bottom loading and unloading process of the molded sand capping, which meets the pre-planned requirements. This makes it possible to construct a thin layer of sand capping in a short period of time. Furthermore, since the center of gravity of the sand capping loading and unloading bucket of the present invention coincides with the buoyancy line of the sand capping work vessel, the bucket area can be made comparable to that of a normal soil transport vessel's mud hold, making it possible to carry out large-scale bottom sediment improvement in a short period of time.

[0014] The sand-capping bucket of the present invention has a rectangular box-shaped bucket with an open top, whose bottom is divided into a grid pattern by vertical plates. Multiple double-sided, automatic opening and closing bottom plates, each measuring half the width of the horizontal divisions (the short side of the bucket), are connected to the bucket bottom by hinges with a limited angle of just under 90 degrees. Furthermore, multiple bottom support girders are attached to the bottom of the bucket, perpendicular to the opening and closing bottom plates, and these support girders move up and down within the width of the bottom plate. When the bottom plate is closed, the weight of the bottom plate and the load are supported by these support girders. The support girders then descend, opening the bottom plate and gently unloading the formed sand capping. Subsequently, when the support girders rise, the necessary rotational moment is generated around the hinges in the closing direction, causing the bottom plate to close normally. Thus, the sand-capping bucket of the present invention is characterized by its ability to gently unload formed sand capping.

[0015] The fall height of the formed sand capping is determined by the width of the base slab. The bottom of the sand capping unloading bucket is divided to minimize the fall height. The same reason is also why automatic opening / closing base slabs are designed to open on both sides. The base slab support girder moves up and down using a support girder lifting device, for example a double-acting hydraulic cylinder. An automatic opening / closing base slab is connected to the bottom of the bucket by a hinge with a limit of just under 90 degrees. The reason for this is that when the base slab is opened vertically at 90 degrees and the support girder pushes the tip of the base slab vertically up, the direction of rotation of the base slab is not determined because there is no deviation in the direction of action. For example, if it is set to 85 degrees, the rise of the support girder will generate the necessary rotational moment in the closing direction around the hinge, and the base slab will close normally.

[0016] The sand capping material supply bucket of the present invention has a hopper-type structure, with vibrating devices fixed to both sides, and the width of the hopper's sand capping material outlet can be automatically adjusted. Furthermore, the sand capping material supply bucket is characterized by its ability to not only spread sand capping material to the sand capping material loading / unloading bucket, but also to level the sand capping material height and compact it. When forming sand that meets the planned requirements, the sand capping material supply bucket accurately distributes appropriate amounts of sand capping material without spreading large amounts. To achieve this, the width of the outlet must be adjusted based on the sand's moisture content, etc. Furthermore, the amount of sand to be spread cannot be adjusted by itself; it must be adjusted by adjusting the vibration strength of the vibrating device. Furthermore, uniform spreading of small amounts may result in loose sand compaction. Formed sand capping on a loose bottom may undergo compression and settlement over time. The normal relative density of sand is considered to be 30-70%. For example, if the regulation requires a relative density of 50 or more, compaction can be easily achieved by attaching an attachment to a sand-capping material supply bucket with a vibration function. However, compacting the soil to a relative density of 70% or more is not very effective, as it may loosen over the long term.

[0017] The sand capping material container of the present invention, which delivers sand capping material to the sand capping material supply bucket, is characterized by the fact that the type, weight, and volume of the sand capping material are standardized. Information about the sand capping material container is important in managing the construction of sand capping that meets planned requirements. It is possible to predict at the time of delivery for each sand capping material container, the level at which the required amount of formed sand has been reached, and whether the amount is appropriate to ensure the specified relative density of the sand. Therefore, direct checks of the sand capping thickness and relative density can be carried out in a planned manner, facilitating highly accurate construction management.

[0018] In the thin-layer sand capping method using a sand-capping work vessel of the present invention, the width of the sand-capping material supply bucket's outlet is first adjusted. Then, sand capping material is received from a standardized sand-capping material container. While adjusting its own vibration, the sand-capping material supply bucket moves back and forth along the entire length of the sand-capping unloading bucket, which is suspended from a three-dimensional support column by a rope connected to a lifting device, to systematically spread the sand capping material. During and at the end of the spreading process, the sand-capping unloading bucket's vibration function is used to vibrate and compress the spread sand capping material, leveling its height and forming a sand capping that meets the planned requirements. Next, the sand-capping unloading bucket loaded with the formed sand is lowered from the barge's opening space to the bottom and gently lands. Next, the bucket is raised to the height equivalent to the formed sand capping. During this raising, the bottom support supporting the retractable bottom slab from below is lowered the length of the bottom slab opening, gently opening the retractable bottom slab, allowing the formed sand to be gently unloaded. The gentle landing of the bucket suppresses the generation of pollution and reduces the sinking of the formed sand capping. Furthermore, since the formed sand does not fall into the water, the occurrence of pollution at this stage is suppressed and the planned shape and condition of the thin layer sand is maintained. Furthermore, the thin layer sand covering method of the present invention is a thin layer sand covering method that consists of a series of steps: forming the sand covering and loading and unloading the formed sand at the bottom of the water. This makes it possible to construct the thin layer sand in a short time.

[0019] When the submerged soil layer is a poor soil layer containing harmful substances, the thin sand capping method of the present invention involves adding a layer of modifier material to a sand capping layer that meets the pre-planned requirements in order to interpose a water purification material between the submerged soil layer and the sand capping layer. This formed sand capping is then unloaded, resulting in bottom sediment improvement that effectively prevents harmful substances from leaching out of the poor soil layer into seawater. Known water purification materials include seashells, steel slag, steelmaking slag, and foamed glass.

[0020] When the surface layer of the water bottom soil layer is extremely soft soil such as floating mud, the sand capping bucket used in the thin layer sand capping method of the present invention is equipped with an underwater vibration device, its outer wall is extended downward to form a low space below the bottom of the bucket, and a highly water-repellent drain sheet is attached to the outer surface of the bucket, the inner surface of the low space, and the automatically opening and closing bottom slab. As a step just before unloading the molded sand capping, the sand capping bucket is lowered to the water bottom and lands, and the sand capping bucket loaded with the molded sand is used to confine the extremely soft soil layer of the water bottom surface in the low space below the bottom of the bucket, which is then consolidated and settled by vibrating the load, eliminating the scattering of bottom mud when the molded sand is unloaded and minimizing uneven embedding of the molded sand into the water bottom ground.

[0021] The key points of this method are to confine the extremely soft soil layer in a low space below the bottom of the bucket, to preload it with a sand-loading bucket loaded with formed sand capping, and to use a highly water-repellent drain sheet for consolidation and drainage. Here, it is essential to provide many water-passing holes in the space walls. Also, the drain sheet is attached to the outer surface of the bucket because the low space is buried in the extremely soft layer. Also, consolidation does not necessarily target the entire extremely soft layer, as this would take too much time. The purpose is to prevent floating mud from flying up and to minimize the sinking of the formed sand capping into the waterbed ground. This is because the highly water-repellent drain sheet is less likely to clog. Effects of the invention

[0022] The latest thin-layer sand-capping method is a step in which sand is uniformly spread while suppressing the occurrence of pollution. The thin-layer sand-capping method of the present invention involves forming sand capping that meets the planned requirements in a sand-capping loading and unloading bucket on board a sand-capping work vessel in advance, and then lowering the bucket loaded with the formed sand to the bottom of the water where it will be covered, allowing it to land gently. The bucket is then raised to the height of the sand-covering thickness, and the bucket's automatic opening and closing bottom plate is gently opened accordingly, allowing the formed sand to be gently unloaded. This ensures that the formed sand does not fall into the water. The advantages of the thin-layer sand-capping method of the present invention are that sand capping that meets the planned requirements in advance on board the vessel, the sand-capping loading and unloading bucket is gently landed, and the formed sand does not fall into the water.

[0023] Forming sand capping that meets the planned requirements on board the ship facilitates advanced construction management. The gentle landing of the sand capping bucket prevents pollution caused by floating mud being stirred up. The landing of the bucket also provides a simple preload, reducing the tendency of the formed sand capping to sink. The most important thing is that there is no underwater falling, which maintains the shape and condition of the planned thin layer of sand capping. This prevents pollution, takes measures to prevent the sand capping from sinking, and is effective in constructing a thin layer that meets the planned requirements in a short period of time.

[0024] Furthermore, the center of gravity of the sand-capping loading / unloading bucket mounted on the sand-capping work vessel of the present invention coincides with the buoyancy line of the sand-capping work vessel, making it possible to give the bucket an area comparable to that of the mud hold of a normal soil-carrying vessel. This makes it possible to provide a sand-capping work vessel that can handle the scale of large-scale projects such as climate change countermeasures. [Brief explanation of the drawings]

[0025] [Figure 1] Side view of the sand-capping work vessel of the present invention [Figure 2] Plan view (cross section along line AA in Figure 1) [Figure 3] Cross section of line BB in Figure 1 [Figure 4] Side view of the sand-capping unloading bucket of the present invention [Figure 5] Also floor plan [Figure 6] Front and rear views of the same [Figure 7] Enlarged cross section of line CC in Figure 4 [Figure 8] Enlarged cross section of line DD in Figure 4 [Figure 9] Illustration of the loading and unloading of sand by a sand-capping work vessel DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

[0027] Figure 1 is a side view of the sand-capping work vessel of the present invention, Figure 2 is a plan view (cross-sectional view taken along line AA in Figure 1), and Figure 3 is a cross-sectional view taken along line BB in Figure 1. In the figures, reference numeral 1 denotes the sand-capping work vessel, 11 denotes a barge, 2 denotes a sand-capping loading / unloading bucket, 3 denotes a sand-capping material supply bucket, 4 denotes a three-dimensional support column, 41 denotes a portal-type support column, 42 denotes a box-type support column, 51 denotes a lifting winch, 52 denotes a pulley, 6 denotes an overhead crane, 61 denotes an overhead crane girder, 7 denotes a winch for moving the sand-capping work vessel, and A denotes the water surface. Here, the combination of lifting winch 51 and pulley 52 is referred to as lifting device 5. An example of the pulley 52 that can be used is a fixed pulley with two coaxial shafts and different radii.

[0028] As shown in Figures 1 to 3, the main components of the sand-capping work vessel 1 are the sand-capping unloading bucket 2, a barge 11 with an open space through which the bucket can be raised and lowered, a three-dimensional support column 4 and lifting device 5 that secure the open space and hold the barge together, and a hopper-type sand-capping material supply bucket 3 and an overhead crane 6 for the bucket, which is attached to the three-dimensional support column 4. The barge 11 with an open space is a barge formed by arranging two barges side by side with a certain open space secured and rigidly joining them with the three-dimensional support column 4. The three-dimensional support column 4 is formed by rigidly joining a portal-type support column 41 and a box-type support column 42 with a vertical beam to form a three-dimensional structure. In the plan view of Figure 2, a total of four box-type support columns 42 are attached to the front and rear of the barge 21, which secures the barge together. The three middle support columns 41 secure the lift space for the sand-capping unloading bucket 2. Winches 7 for moving the sand-capping work vessel 1 are installed at the four corners of the barge 11. Four anchors are anchored and ropes are tensioned and connected to a moving winch 7. In addition, the center of gravity of the sand-capping loading / unloading bucket 2 mounted on the sand-capping work vessel 1 coincides with the buoyancy line of the sand-capping work vessel 1, so it is possible to make the bucket area comparable in size to the mud hold of a normal soil transport vessel.

[0029] The sand-capping work vessel 1's sand-capping unloading bucket 2 is suspended from the three-dimensional support column 4 by a rope connected to the lifting winch 51 of the lifting device 5 on the barge 11. The sand-capping material supply bucket 3 is a sand-capping material supply device that can travel the entire length of the sand-capping unloading bucket 2 using an overhead crane 6 installed on the three-dimensional support column 4. The sand-capping material is transported in a sand-capping material container. A separate crane is provided to transfer the material from this container to the sand-capping material supply bucket 3. For example, if the container is a 2m cube, a crane with a lifting capacity of approximately 15 tons is required.

[0030] Figure 4 is a side view of the sand-capping unloading bucket 2 of the present invention, Figure 5 is a plan view of the same, and Figure 6 are front and rear views of the same. In the figures, 21 is an automatically opening / closing bottom slab, 22 is a bottom slab support girder, 23 is a support girder up / down movement device, and 24 is a bottom vertical slab. In the side view of Figure 4, the left side of the center line shows the automatic opening / closing bottom slab 21 in a closed state, and the right side shows the automatic opening / closing bottom slab 21 in an open state.

[0031] The sand-capping unloading bucket 2 has a rectangular box-shaped bucket with an open top, the bottom of which is divided into a grid pattern by vertical plates 24, and multiple double-hinged, automatically opening and closing bottom plates 21, each measuring half the length of the bucket's horizontal division width, are connected to the bucket bottom by hinges with an angle limit of just under 90 degrees. Furthermore, multiple bottom plate support girders 22 are attached to the bottom of the bucket, intersecting at right angles to the opening and closing bottom plates 21, and these bottom plate support girders 22 can move up and down the height of the bottom plate width. The bottom plate support girders 22 are moved up and down by a support girder lifting device 23, for example a double-acting hydraulic cylinder.

[0032] Figure 7 is an enlarged cross-sectional view of line CC in Figure 4, showing the automatic opening / closing base 21 in a closed state, and Figure 8 is an enlarged cross-sectional view of line DD in Figure 4, showing the automatic opening / closing base 21 in an open state. When the automatic opening / closing base 21 is in a closed state, the base slab's own weight and the load weight are supported by this base slab support girder 22, and as the base slab support girder 22 descends, the automatic opening / closing base slab 21 opens and the formed covering sand is gently unloaded.

[0033] Figure 9 is an explanatory diagram of the loading and unloading of sand capping by a sand-capping work vessel 1. In the figure, B is the water bottom, C is the water bottom ground, and D is the formed sand capping. Figure (a) shows the sand-capping unloading bucket 2 loaded with formed sand capping D suspended from the three-dimensional support column 4 by a rope connected to a lifting winch 51 in the opening space of the barge 11. Figure (b) shows the state in which the sand-capping unloading bucket 2 has descended from the opening space of the barge 11 to the water bottom B and gently landed. Figure (c) shows the state in which the sand-capping unloading bucket 2 has gently unloaded the formed sand capping D and has been pulled up into the opening space of the barge 11. [Explanation of symbols]

[0034] 1 Sand covering work boat 11 barge 2. Sand capping and unloading bucket 21 Automatic opening and closing bottom plate 22 Bottom support girder 23 Support girder up / down device 24 Bottom vertical plate 3 Sand capping material supply bucket 4 Three-dimensional support 41 Portal post 42 Box-shaped support 5 Lifting device 51 Lifting winch 52 Pulley 6. Overhead crane 61 Overhead Crane Girder 7. Winch for moving the sand-capping work vessel A water surface B Bottom surface C Underwater ground D Formed sand capping

Claims

1. The sand capping work vessel is used for a thin layer sand capping method, which is a series of sand capping work that meets the pre-planned requirements on board the vessel and the bottom loading and unloading of the formed sand capping. The main components of the sand capping work vessel are a sand capping unloading bucket, a barge with an opening space for the bucket to be raised and lowered, and the barge is integrated with the opening space secured, and the three-dimensional support and lifting device for suspending the bucket, and a hopper-type sand capping material supply bucket and an overhead crane for this bucket installed on the three-dimensional support. The essential sand capping unloading bucket has a box-shaped structure with an open top and the bottom of the bucket is divided into a grid pattern by vertical plates, In addition, an automatic opening / closing bottom slab is connected with a hinge to match the width of one of the sections, and the sand capping method using this sand capping work vessel involves a sand capping material supply bucket traveling back and forth along the entire length of the sand capping unloading bucket suspended from a three-dimensional support to systematically scatter sand capping material, and then the sand capping unloading bucket loaded with molded sand that meets the planned requirements is lowered from the opening space of the barge to the bottom of the water where it lands quietly, and the bucket is raised to the height of the sand capping thickness, and the automatic opening / closing bottom slab is opened in conjunction with this raising to quietly unload the molded sand.This is a sand capping work vessel used for a thin layer sand capping method.

2. In the sand-capping bucket of claim 1, the bucket structure is a rectangular box-shaped bucket with an open top, the bottom of the bucket is divided into a grid pattern by vertical plates, and multiple double-sided automatic opening and closing bottom plates, each measuring half the length of the horizontal division width (the short side of the bucket), are connected to the bottom of the bucket by hinges with an angle limit of just under 90 degrees, and multiple bottom plate support girders are attached to the bottom of the bucket, which are perpendicular to the automatic opening and closing bottom plate, and these support girders automatically move up and down in height within the bottom plate width.When the bottom plate is closed, the weight of the bottom plate and the load weight are supported by these support girders, and when the bottom plate support girders descend, the bottom plate opens and the molded sand is unloaded.Subsequently, when the bottom plate support girders rise, the necessary rotational moment in the closing direction is generated around the hinge, causing the bottom plate to close back to its original position.This sand-capping bucket is characterized by the fact that it allows the molded sand to be gently unloaded in this way.

3. The sand-capping material supply bucket of claim 1 is characterized in that the bucket has a hopper-type structure, has a plurality of vibration devices fixed to its side, and can automatically change the width of the hopper's sand-capping material discharge opening, and can also function as a top leveler and compactor for the sand-capping material discharged into the sand-capping material loading / unloading bucket.

4. 2. A sand-capping material container for carrying sand-capping material into the sand-capping material supply bucket of claim 1, wherein the type, weight, and volume of the sand-capping material are standardized.

5. 1. A thin layer sand capping method according to claim 1, wherein the sand capping material supply bucket mounted on the sand capping work vessel adjusts the width of its discharge opening before receiving sand capping material from a standardized sand capping material container, and while adjusting its vibration function, the sand capping material supply bucket moves back and forth along the entire length of the sand capping unloading bucket suspended from a three-dimensional support by a rope to systematically discharge the sand capping material, and uses its vibration function to level the height of the discharged sand material during and at the end of the discharge to form sand that meets the planned requirements, and then the sand capping unloading bucket loaded with the formed sand descends from the opening space of the barge to the bottom of the water and lands quietly, and then the bucket is raised to a height equivalent to the height of the formed sand capping, and at the same time, the bottom slab support supporting the automatic open-close bottom slab from below is lowered by the length that the open-close bottom slab opens, thereby opening the open-close bottom slab and quietly unloading the formed sand.

6. In the thin layer sand covering method of claim 1, when the bottom soil layer of the water is a poor soil layer containing harmful substances, this method involves forming a layer of modifying material that meets the planning requirements in advance to interpose a water quality purification material between the bottom soil layer of the water and the sand covering layer, and then unloading this formed sand covering, thereby improving the bottom sediment and strengthening the prevention of harmful components from leaching out of the poor soil layer into seawater.

7. In the thin layer sand capping method of claim 1, when the surface layer of the water bottom soil layer is extremely soft soil such as floating mud, the sand capping loading and unloading bucket used in this method is equipped with an underwater vibration device, and its outer wall is extended downward to form a low space under the bottom of the bucket. Furthermore, a highly water-repellent drain sheet is attached to the outer surface of the bucket, the inner surface of the low space, and the automatically opening and closing bottom plate. As a step just before unloading the molded cover sand, the sand capping bucket is lowered to the water bottom and lands, and the sand capping bucket loaded with the molded cover sand confines the extremely soft soil layer on the water bottom surface in the low space under the bottom of the bucket, and this is submerged by vibrating and loading this, eliminating the flying up of bottom mud when the molded cover sand is unloaded and minimizing uneven embedding of the molded cover sand into the water bottom ground. This is a thin layer sand capping method characterized by the above.

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