Vacuum bucket dredging method and vacuum bucket as well as vacuum bucket dredger

Abstract

To provide a vacuum consolidation dredging method that dredges the bottom water ground without stirring, generating no polluted mud, which is different from the other dredging method, to allow consolidation improvement for dredged mud with mud-content of 100%, wherein the method is intended for a large scale dredging construction without any function of rotational motion of a bucket so it is not suitable for a mid or small scale dredging construction which requires rotational motion of the bucket as the basic one.SOLUTION: A method of the present invention obtains a rotational function, using a character of a vacuum consolidation dredging method. This is achieved by installing a large rotational disk on a vacuum bucket dredger, wherein on the disk four support columns forming a three-dimensional structure are installed to fix two horizontal booms. The projection of the boom is to be shortened as much as possible in a stable and compact structure by hanging a vacuum bucket on one of tips of the booms and fixing a counter weight on the other of the tips. Further, associated apparatuses of the vacuum bucket rotate in synchronism with the rotation as the associated apparatuses are mounted on the disk, which eliminates complex motion between the vacuum bucket and the associated apparatuses.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a vacuum bucket dredging method, a vacuum bucket, and a vacuum bucket dredger. Specifically, the vacuum bucket of the present invention is a box-shaped dredging bucket with an open bottom, and the vacuum bucket dredger and vacuum bucket dredger use the suction force of vacuum pressure to hold the dredged soil. [Background technology]

[0002] Vacuum bucket dredging is a new method, while grab bucket dredging has been a popular method for some time. The grab bucket used in this method is extremely heavy considering the dredging volume. This is due to the mechanism of the dredging bucket. The shell-shaped grab bucket has a hinged structure like a clamshell. The bucket is hung from a crane and dropped under its own weight with its open end digging into the ground. When the bucket is lifted up, it closes due to its heavy weight and dredges the sediment. The grab dredger used for the operation is equipped with a crane with a winch mechanism that can rotate 360 ​​degrees, and it raises and lowers the grab bucket to dredge sediment from the bottom of the water. It has mainly been used for maintenance dredging work to ensure water depth.

[0003] In accordance with the Marine Pollution Prevention Act, offshore construction requires measures to prevent the spread of pollution. Pollution occurs when fine clay particles and other suspended solids in sediment disperse into the water. The finer the dredged sediment mass, the more easily suspended solids dissolve. Therefore, measures to prevent the spread of pollution must minimize the contact surface between the sediment mass being dredged and the water. However, the grab bucket dredging method involves dropping a large, heavy bucket into the waterbed while open, then closing the bucket to capture the sediment. While unavoidable, this method disturbs the ground, mixing it with water and kneading it. This artificially creates soft soil with a high water content, making it easier for suspended solids to disperse. The measure to prevent the spread of pollution when using grab bucket dredging involves installing a pollution prevention frame and dredging within it. The anti-pollution frame is a square frame with floats, and the frame is fitted with an anti-pollution membrane, and is used by connecting it to a construction ship. However, this method is still not sufficient.

[0004] Grab bucket dredging has been used primarily for dredging work to maintain water depth. In addition, there has been an increase in the dredging of bottom mud contaminated with heavy metals and dioxins. However, due to a lack of disposal sites for dredged soil and sand, there has been an increasing demand for dredging work that produces a thin, uniform, and flat layer of the minimum necessary thickness, leading to the development of the thin-layer dredging method. When dredging with a grab bucket, excess water is also captured inside the grab bucket along with the soil and sand. In particular, the thin-layer dredging method increases the bucket's airtightness, further increasing the amount of excess water. If the dredging is loaded onto a soil transport barge as is, the barge would have to carry a lot of water, which is inconvenient. Therefore, efforts have been made to reduce the excess water mixed into the bucket and increase the mud content. (See, for example, Patent Document 1.)

[0005] On the other hand, in 2018, a vacuum consolidation dredging method was developed that is completely different from grab bucket dredging. It uses a steel box bucket with a bottom-opening mechanism that utilizes vacuum pressure. Vacuum consolidation has traditionally been widely used as a ground improvement method on land. The distinctive feature of vacuum consolidation dredging for seabed ground is that the loaded ground surface is kept airtight in some way, and water pressure is used in addition to atmospheric pressure for the load. From an environmental perspective, this method's distinctive feature is that it increases the strength and reduces the volume of the seabed ground through consolidation settlement without causing in-situ water pollution. Vacuum consolidation dredging is a combination of vacuum consolidation ground improvement and dredging techniques. The vacuum consolidation dredging method is a method intended to dewater and improve the dredged soil in its original location on the riverbed or seabed as a civil engineering recycling material.

[0006] The vacuum consolidation dredging method uses a device called an airtight loading box. The airtight loading box is an airtight loading box for vacuum consolidation, and is a dredging bucket. The airtight loading box has a box-shaped structure with an open bottom, and an airtight water separation tank and box tower are attached to the center of the box's exterior top surface. In addition, a thin vacuum tank is installed on the interior ceiling surface, communicating with the airtight water separation tank. Directly below this, the tank is divided by box partitions with drainage functions to form multiple compartments, and water-permeable lids are installed on the top of the compartments (see, for example, Patent Document 2).

[0007] Since the vacuum consolidation dredging method is a new method that utilizes vacuum pressure, we will reconfirm the conditions under which the dredged soil (filled soil) taken into the airtight loading box can be held without falling. The falling force of the filled soil in the box is the weight of the filled soil itself. The forces that prevent it from falling against this are the vacuum suction force on the top surface of the filled soil and the adhesive force of the partition wall surface. A force that contributes to the falling of the filled soil is the pull-out force. This pull-out force is the adhesive force of the ground on the dredging surface when the box is pulled up and the negative pressure generated on the dredging surface. Here, we will reconfirm the balance between the falling force of the filled soil and the fall-prevention force.

[0008] The maximum height of the airtight loading box is 2m, and the wet unit weight of the fully consolidated soil is 16kN / m 3 The vacuum pump's vacuum suction force per unit area is 80kN / m2 So, 32kN / m 2 <80kN / m 2 Therefore, the vacuum suction force on the ceiling surface is sufficient to prevent the soil from falling. However, the vacuum suction force acts on the top surface of the fill soil. Therefore, this balance is subject to the condition that the fill soil is a single unit. In other words, it would be meaningless if only the top surface of the fill soil was lifted and the rest fell. The fill soil must be strong enough to separate under its own weight and not fall. This condition for the integrity of the fill soil was verified through model experiments and is the strength achieved by consolidating the fill soil until its natural moisture content is below the liquid limit. However, this means that it is safe if the moisture content is below the liquid limit; dredging is possible even near the liquid limit. However, since the adhesive strength near the liquid limit varies depending on the type of clay, it is necessary to check not only the moisture content but also the strength of the dredged clay.

[0009] In addition to its own weight, other factors that cause the fill soil to fall include the pull-out force of the fill soil on the dredged surface of the waterbed. In other words, with vacuum consolidation dredging, clay is removed from the dredged surface by pulling up the box. In addition, negative pressure (vacuum pressure) is generated on the removed dredged surface. The negative pressure acting on the dredged surface can be equivalent to the suction force on the top surface of the fill soil, but this is eliminated by water supplied from the vertical water pipe (see below). Furthermore, the adhesive force on the dredged surface rarely exceeds 100 kPa if the dredged surface is shallow, and even if it does exceed this force, with vacuum consolidation dredging, the suction force of the bulkheads with drainage functions is added, making the fall prevention force sufficiently greater.

[0010] Conventional vacuum consolidation dredging methods are designed for large-scale construction projects. The target submarine ground for dredging with this method is ground that can be vibrated with an airtight loading box, excluding hard soil and gravel ground. The target ground covers a wide range of ground, from extremely soft ground exceeding the liquid limit to unconsolidated sedimentary ground. Vacuum consolidation dredgers were developed to compete with large-scale drag suction dredgers. Drag suction dredgers travel at low speeds, using a dredging pump to suck in any type of sediment from the seabed along with seawater through a drag head grounded on the seabed, and then load the sediment into the mud hold on board for transport. Most of the material being transported is seawater with a low mud content. In contrast, the distinctive feature of vacuum consolidation dredgers is that they can increase the strength of the seabed and reduce its volume by consolidating and sinking it in situ. Naturally, the mud content is 100%. As no water is transported, the size of the mud tank is halved. Vacuum consolidation, which produces such great advantages, takes time to consolidate, but it is evaluated as having great benefits that outweigh this.

[0011] As mentioned above, grab buckets become extremely heavy as the bucket size increases. Dredging vessels equipped with these devices are subject to large eccentric loads, resulting in large sizes and increased costs. Therefore, development is underway for vibratory concrete-driving hydraulic excavating buckets and excavating equipment and dredging vessels equipped with these buckets. This excavating bucket minimizes pouring energy through vibratory concrete pouring. The excavated soil is held in place by a pair of hydraulically powered opening and closing wall members that clamp the soil in the direction of contraction at the bottom of the bucket, preventing the bucket from closing due to peripheral friction and soil deformation resistance. Only soft soil can be closed. Both clamping and closing energy are small. This construction method minimizes excavation energy and reduces the weight and size of each bucket stage. Furthermore, heavy equipment and dredging vessels are prevented from becoming large by correcting the large eccentric load with a movable counterweight, significantly reducing costs. However, this method does not produce a flat dredged surface like the grab bucket dredging method (see, for example, Patent Document 3). [Prior art documents]

[0012] [Patent Document 1] Patent No. 5335955 [Patent Document 2] Patent No. 6582361 [Patent Document 3] Problems that Patent No. 7186351 aims to solve

[0013] Currently, the existence of contaminated bottom sediment contaminated with heavy metals and dioxins is a problem. This contaminated bottom sediment is found in large quantities in urban rivers and the sea areas near estuaries. The thin layer dredging method is a countermeasure against this contaminated bottom sediment. Furthermore, the intensification of rainfall, thought to be caused by climate change, has caused large-scale flooding damage over a wide area. The principle of flood control is to lower the water level of rivers during floods to allow the floodwaters to flow safely. One method for achieving this is river dredging, a method in which the riverbed is dredged to increase the flow volume and lower the water level. While river dredging may require an estuary weir, it is the only effective countermeasure that can be implemented within the river channel. The countermeasures for both contaminated bottom sediment and large-scale flooding damage are dredging methods.

[0014] Dredging work on rivers is small to medium-sized compared to marine construction work. Currently, small to medium-sized dredging work is often carried out using grab bucket dredgers. As mentioned above, grab buckets are extremely heavy objects. They tend to disturb the excavated ground and spread pollution. In contrast, the airtight loading box itself used in the vacuum consolidation dredging method is a lightweight structure. This makes it possible to make the airtight loading box extremely large to accommodate large-scale dredging work.

[0015] Unlike other dredging methods, the vacuum consolidation dredging method does not mix the target ground with water and dredges the ground horizontally without disturbing it. Therefore, it generates very little pollution. It also dredges with a 100% mud content. However, current vacuum consolidation dredging methods are designed for large-scale dredging projects, and dedicated vacuum consolidation dredgers lack bucket rotation capabilities, making them unsuitable for small- to medium-sized dredging projects such as river dredging, where bucket rotation is essential. The problem that this invention aims to solve is the development of a vacuum bucket that utilizes the characteristics of the vacuum consolidation dredging method to acquire rotation functionality and enable horizontal dredging suitable for small- to medium-sized dredging projects. In other words, the development of a vacuum bucket dredging method that can be used to dredge contaminated bottom mud and areas affected by large-scale flooding.

[0016] Specifically, challenge 1 is that in dredging methods that use vacuum pressure, the higher the vacuum pressure, the more difficult it is to manage the vacuum equipment. Challenge 2 is achieving a bucket rotation function in dredging methods that use vacuum pressure. This presents a difficulty not present in vacuum consolidation methods on land. In other words, the vacuum bucket and related equipment, as well as the cables and hoses connecting them, all undergo complex movements in accordance with the movement of the vacuum bucket. Next, challenge 3 is that in the case of river dredging, in addition to the need to miniaturize the dredger, there are height restrictions on ships relative to bridges that cross rivers. Means to solve the challenges

[0017] The ground to be dredged using conventional vacuum consolidation dredging methods covers a wide range of ground conditions, from extremely soft ground exceeding the liquid limit to unconsolidated sedimentary ground that can be subjected to vibration pouring. For this reason, the vacuum equipment and vacuum-related equipment for this method are designed for extremely soft ground. Because the volume of consolidation wastewater is large, a large air-water separation tank is installed, and the vacuum equipment is large because it produces a large, high-vacuum capacity. However, among soft clayey ground, there are not many clays whose natural water content exceeds the liquid limit. In other words, common clays rarely exceed the liquid limit. Examples of clays that do exceed the liquid limit include floating mud organic mud, Ariake clay, and Higashi-Osaka alluvial clay.

[0018] The solution to Problem 1 of the present invention is to limit the ground to be dredged using a vacuum bucket to soft ground that does not exceed the liquid limit and to sedimentary ground that can be vibrated with a vacuum bucket. Second, vacuum pressure is not used for vacuum consolidation, but is limited to its function of suction force to prevent the dredged soil from falling under its own weight. The dredging vacuum bucket of the present invention has an open bottom, similar to the airtight loading box used in the vacuum consolidation dredging method. However, if the ground is strong enough for dredging, consolidation is not performed. For example, if the entire ground to be dredged exceeds the liquid limit, the idea is to perform ground improvement using the vacuum consolidation method in advance. However, such ground is rare among ordinary ground. Because of this rare ground, other measures are taken without combining multiple layers of ground.

[0019] In the vacuum bucket dredging method of this invention, the use of vacuum pressure is limited to the suction force required to prevent the dredged material from falling under its own weight. As mentioned above, another factor that can cause the dredged material to fall is the pulling force acting on the dredged material inside the vacuum bucket. When the bucket is raised, the bottom of the water is pulled away by the dredging surface. At this time, the adhesion (adhesion) of the ground resists the dredging surface. Furthermore, negative pressure is generated on the dredging surface. The adhesion of the bottom of the water to the dredging surface is cut horizontally with a water jet mixed with mineral particles, and the negative pressure generated on the dredging surface is eliminated by supplying water through a vertical water pipe. The only vacuum pressure required is the suction force required to prevent the dredged material from falling under its own weight. The vacuum bucket dredging method achieves a level of vacuum pressure that is extremely easy to manage. Furthermore, this method allows for the miniaturization of vacuum equipment. The required vacuum pressure is assumed to be about -40 kPa gauge pressure. A vacuum pressure of about -40 kPa is extremely easy to manage, and there will be almost no problems with the vacuum pressure. This benefit is immeasurable.

[0020] The vacuum bucket of this invention has a box-like structure with an open bottom. The top of the bucket is equipped with an underwater vibration device, a drainage check valve, a vacuum valve connected to a vacuum device, and an air pressure valve connected to a compressor. The ceiling inside the bucket is equipped with a ceiling drain connected to the vacuum valve, air pressure valve, and check valve. The interior space of the bucket is divided by a partition wall, leaving the bottom undivided. Inside the bucket wall is a vertical, one-way water pipe pointing downward, and a water jet pipe looped around the inside bottom. This pipe is connected to a compressor that pumps water mixed with mineral particles, and is equipped with numerous horizontal water jet nozzles.

[0021] The vacuum consolidation dredging method uses vacuum consolidation as its main process. The airtight loading box used in this method is compared with the vacuum bucket of the present invention. Because the vacuum bucket dredging method eliminates the need for vacuum consolidation in the ground, there is no large amount of consolidation wastewater generated by vacuum consolidation. Therefore, the large air-water separation tank was removed, and a new check valve was installed. Furthermore, the interior space of the vacuum bucket was divided into separate spaces by a partition wall, leaving the bottom intact. A vertical water pipe is installed inside the bucket wall, and a new loop-shaped water jet pipe is installed inside the bottom. The outer wall of the vacuum bucket is longer than the partition wall to improve sealing when using a water jet and to strengthen the prevention of contamination diffusion.

[0022] The underwater vibration device and drainage check valve are functions of the vacuum bucket of this invention and are used when pouring the bucket. When the vacuum bucket hits the bottom, the bucket is filled with water. When the vacuum bucket is vibrated into the bottom ground, the drainage water is drained through the check valve. As mentioned above, the factors that cause the dredged soil inside the vacuum bucket to fall include the weight of the dredged soil itself as well as the pull-out force. This pull-out force is the adhesion force of the ground on the dredged surface when the bucket is lifted and the negative pressure generated on the dredged surface. The water jet pipe sprays a water jet mixed with mineral particles horizontally when the bucket is lifted, horizontally cutting the adhesion force of the ground on the dredged surface. Even with a typical upper layer of alluvial clay ground, the adhesion force is 100kN / m 2In rare cases, the pressure can reach 1000m / s. This is to break such adhesion. The vertical water pipe supplies water to eliminate the negative pressure that occurs on the dredging surface when the bucket is lifted. The water jet pipe is a mixture of water with mineral particles, such as sand particles, to increase the cutting power.

[0023] In the dredging process using the vacuum bucket of the present invention, the vacuum bucket is hoisted by a crane, landed on the bottom of the water, and vibration pouring is continued until the top drain surface of the bucket touches the bottom of the water. The vacuum valve is then opened to reduce the pressure, and once a predetermined pressure reduction is reached, a horizontal water jet is sprayed to horizontally cut the ground on the dredging surface, and lifting of the vacuum bucket containing the dredged soil begins. The negative pressure on the dredging surface generated at this time is applied to the water jet and released by supplying water through a vertical water pipe, while the bottom of the water is dredged.

[0024] When the vacuum bucket is used for vibration pouring, the drainage is discharged through the check valve, but the bucket remains airtight. The specified pressure reduction is assumed to be around -40kPa. The height of the vacuum bucket is 1.5m, and the wet unit weight of the dredged soil (fill soil) is 16kN / m 3 Then, the weight of the filled soil per unit area is 24kN / m 2 The falling force of the filled soil in the vacuum bucket dredging method is only the weight of the filled soil, so it is 24kN / m 2 <40kN / m 2 It is sufficiently safe. When unloading the dredged soil onto the soil transport barge, the vacuum valve is closed and the air pressure valve is opened to push out the dredged soil with compressed air. The only resistance to pushing out the soil at this time is the adhesive force between the filled soil and the bucket wall, and pushing out with compressed air is easy because there is no increase in strength due to consolidation.

[0025] When the dredging ground is poor, e.g., ground that generates hydrogen sulfide, it is preferable to use iron-containing mineral particles, which dissolve in seawater and become iron salts, as the mixed mineral particles for the water jet. For example, blast furnace slag has been shown to be effective in suppressing the generation of hydrogen sulfide and turbidity. It is advisable to add blast furnace slag particles or blast furnace slag powder to the saltwater tank in the water jet pumping path in advance to promote the generation of iron salts. When dredging poor ground, iron-containing mineral particles double the effectiveness of the vacuum bucket dredging method of the present invention.

[0026] In principle, the vacuum bucket dredging method of the present invention is not applicable to bottom ground exceeding the liquid limit. However, it is common for only a small portion of the surface layer to be extremely soft and cohesive. To dredge such bottom ground, the vacuum bucket is placed on the bottom and vibrated while pouring concrete. Even when the vacuum bucket's ceiling drain surface touches the ground, vibratory pouring continues to vibrate and consolidate the surface layer of the bottom ground. Consolidated water is drained through a check valve. After consolidation is complete, the vacuum valve is opened to reduce pressure, generating suction on the ceiling drain surface and retaining the dredged soil. Thus, the vacuum bucket dredging method of the present invention achieves a division of roles: consolidation is performed by vibration load, while dredged soil retention is achieved by vacuum pressure. The required vacuum pressure is extremely easy to manage, e.g., -40 kPa, thereby enabling the miniaturization of the vacuum equipment.

[0027] In the vacuum bucket structure of the present invention, the ceiling drain is a multi-layered drain sheet that also serves as a screen. For example, by using a double-layered drain sheet, the drain function is enhanced at the overlapping portion of the sheets, making the ceiling drain extremely thin, and minimizing the vacuum target space, thereby shortening the decompression time and minimizing the size of the vacuum device.

[0028] Objectives 2 and 3 of the present invention are to utilize the advantages of the vacuum consolidation dredging method to acquire a swivel function and thereby reduce the size of the vacuum bucket dredger. To achieve this, a large swivel is installed on the dredger used in the vacuum bucket dredging method of the present invention. The swivel is installed forward, aligned with the longitudinal centerline of the barge. Four equidistant struts are erected around the periphery of the swivel, and their heads are connected by girders to form a three-dimensional support. Two horizontal booms are fixed in parallel to the top of the three-dimensional support, and at one end of each boom, a vacuum bucket is suspended by multiple ropes connected to multiple winches, and a counterweight is attached to the other end. The front and both sides of the vacuum bucket are positioned away from the barge as the swivel rotates. This is intended for dredging and loading / unloading the waterbed. Also, on the top of the slewing platform are the above-mentioned multiple winches, a vacuum device connected to the vacuum valve of the vacuum bucket, a water jet pipe, and a compressor connected to the compressed air valve. Furthermore, cables and hoses are handled by an automatic winding device. As the slewing platform rotates, the related equipment on the lathe moves in sync with the rotation. This allows the vacuum bucket dredger to feature an arrangement and structure of equipment that does not interfere with the rotation of the slewing platform.

[0029] The reason for using two horizontal booms is to prevent the vacuum bucket from rotating horizontally by suspending it from two beams. The reason for using a three-dimensional support is that, since both ends of the horizontal boom overhang, the overhanging parts are kept as short as possible to give the horizontal boom a stable structure with two-point support. This makes it easier to restrict height without the need for cable stays like in cable-stayed bridges, as in Patent Document 3. The three-dimensional support and horizontal boom can be disassembled and reassembled as needed. The vacuum bucket suspended from the horizontal beam on the slewing table is balanced by a counterweight, and the eccentric load of the barge is balanced by a counterweight installed at the rear inside the barge. In this way, the center of gravity of the vacuum bucket dredger is balanced, and because the vacuum bucket itself is not very heavy, height and size can be kept down. Effects of the invention

[0030] The vacuum bucket dredging method of the present invention limits the use of vacuum pressure to the suction force that prevents the dredged soil in the dredging bucket from falling under its own weight.The adhesive force of the dredged surface of the bottom ground when the dredging bucket is lifted, which contributes to this falling under its own weight, is cut horizontally with a water jet mixed with mineral particles, and the negative pressure generated on the dredged surface is eliminated by supplying water through a vertical water pipe, thereby reducing the required vacuum pressure to a level that is extremely easy to manage and further achieving the effect of miniaturizing the vacuum device.

[0031] In the case of poor ground that generates hydrogen sulfide, the mineral particles mixed with the water jet are mineral particles containing iron that dissolves in seawater and becomes iron salts, which suppresses the generation of hydrogen sulfide and pollution and doubles the effectiveness of the vacuum bucket dredging method of the present invention in poor ground.

[0032] In the vacuum bucket dredging method for underwater ground with an extremely soft surface, the surface is compacted using vibration load, while the dredged soil is held in place by the suction force of vacuum pressure. This division of roles reduces the required vacuum pressure to a level that is extremely easy to manage, and also has the effect of making the vacuum equipment smaller.

[0033] The vacuum bucket dredger of this invention has a large swivel mounted at the front of the barge. The winch, vacuum device, compressor, and other equipment required for the vacuum bucket are mounted on top of the swivel. This synchronizes the rotation of the related equipment, eliminating the complex mutual movements of the vacuum bucket and related equipment. A three-dimensional support is also mounted on the swivel, and two horizontal booms are attached in parallel to the top of the support. A vacuum bucket is suspended from one end of the boom, and a counterweight is attached to the other end. This balances the boom's center of gravity. Suspending the bucket from two supports prevents the bucket from rotating horizontally. The three-dimensional support minimizes the overhang of the horizontal boom, and the boom is supported at two points, creating a stable structure. The load of the barge's swivel is balanced by a counterweight installed at the rear of the barge. In this way, the overall center of gravity of the structure is balanced stably, and the vacuum bucket itself is not very heavy, so the height of the dredger can be reduced and the dredger can be made smaller. [Brief explanation of the drawings]

[0034] [Figure 1] FIG. 1 is a front view of the vacuum bucket of the present invention. [Figure 2] FIG. [Figure 3] This is also a side view. [Figure 4] Also shown is a vertical cross section (AA in Figure 2) and a system diagram of the vacuum bucket dredging method. [Figure 5] FIG. 1 is a side view of the vacuum bucket dredger of the present invention. [Figure 6] FIG. [Figure 7] FIG. 1 is a layout diagram of the turning table and the associated equipment for the vacuum bucket. [Figure 8] Plan view of unloading dredged soil from the vacuum bucket of a vacuum bucket dredger onto a soil transport barge DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

[0036] Figure 1 is a front view of an example of a vacuum bucket of the present invention. Figure 2 is a plan view of the same. Figure 3 is a side view of the same. Figure 4 is a vertical cross-sectional view (AA in Figure 2) and a system diagram of the vacuum bucket dredging method. In the figure, 1 is a vacuum bucket, 11 is a drainage check valve, 12 is a vacuum valve, 13 is an air pressure valve, 14 is an air pressure valve for a water jet, 15 is a vertical water pipe, 16 is a lifting device, 17 is a rope, 1a is an underwater vibration device, 1b is a winch, 1c is a vacuum device, 1d is a compressor, 1e is a small air-water separation tank, 1f is a mineral particle mixed water tank, 1g is a ceiling drain, 1h is a bulkhead, 1i is a water jet pipe, A is the water surface, B is the water bottom, and C is the bottom ground.

[0037] The vacuum bucket 1 shown here is suspended at two points. This prevents the vacuum bucket 1 from rotating horizontally and ensures stability. As shown in Figure 4, the vacuum bucket 1 is box-shaped with an open bottom. On its top are a submersible vibration device 1a, a drainage check valve 11, a vacuum valve 12 connected to a vacuum device 1c, and a compressed air valve 13 connected to a compressor 1d. The ceiling of the vacuum bucket 1 is equipped with a ceiling drain 1g connected to the vacuum valve 12, compressed air valve 13, and drainage check valve 11. The interior of the vacuum bucket 1 is divided into two compartments by a partition wall 1h, leaving the bottom uncovered. For example, if the vacuum bucket 1 is 1.5 m high, the horizontal cross-sectional area of ​​the compartment is approximately 1 m x 1 m. The inside of the vacuum bucket 1's outer wall is equipped with a vertical water pipe 15 pointing downward in one direction, and a water jet pipe 1i with numerous horizontal water jet nozzles connected to a compressor 1d, which is looped around the inside of the bottom and pumps water mixed with mineral particles. The bottom of the vertical water pipe 15 is sealed to prevent soil and sand from entering, and there is a water port with a hinged lid that opens when negative pressure is generated on the side of the bottom. The outer wall of the vacuum bucket 1 is longer than the bulkhead 11h to improve airtightness when using the water jet.

[0038] In the dredging process using the vacuum bucket 1 of the present invention, the vacuum bucket 1 is hoisted by a crane, landed on the water bottom ground C, and vibration pouring is continued until the ceiling drain 1g of the vacuum bucket 1 touches the water bottom ground C. The vacuum valve 12 is then opened to reduce pressure. Once a predetermined pressure reduction is reached, a horizontal water jet is sprayed from the water jet pipe 1i, horizontally cutting the ground on the dredging surface and starting the lifting of the vacuum bucket 1 containing the dredged soil. The negative pressure on the dredging surface generated at this time is applied to the water jet and released by the supply of water through the vertical water pipe 15, while the water bottom is dredged. The spraying of the horizontal water jet is illustrated in Figure 4. The bottom of the bulkhead 1h forms the dredging surface.

[0039] Figure 5 is a side view of an example of a vacuum bucket dredger according to the present invention. Figure 6 is a plan view of the same. Figure 7 is a layout diagram of the swivel base and related equipment for the vacuum bucket. In the figure, 2 is the vacuum bucket dredger, 21 is a barge, 22 is a support, 23 is a horizontal boom, 24 is a counterweight, 25 is a pulley, 2a is a swivel base, and 2b is an operation room. The vacuum bucket 1 mounted on the vacuum bucket dredger 2 in Figure 5 is in a state where it has been vibrated and poured into the bottom ground C up to the ceiling drain 1g of the vacuum bucket 1. The vacuum bucket 1 in Figure 4 is in a similar state. The swivel base 2a of the vacuum bucket dredger 2 rotates 360 degrees. As shown in Figure 6, the front and both sides of the vacuum bucket 1 are positioned away from the barge 21 due to the rotation of the swivel base 2a. This is intended for dredging the bottom ground C and unloading the dredged material.

[0040] During construction, vacuum consolidation equipment on land rarely moves. The exception is the air-water separation tank installed within the ground improvement area, which only moves vertically to compensate for the amount of subsidence caused by the ground subsidence. In contrast, the vacuum bucket 1 used to dredge the waterbed C moves vertically beyond the water depth. Furthermore, it rotates horizontally when unloading dredged soil onto a soil transport barge. This means that the vacuum bucket 1, its associated equipment, and the cables and hoses connecting them all move in a complex manner in response to its movement. The solution to this problem is the swivel 2a. Figures 4, 6, and 7 show the flow diagrams illustrating this solution. The winch 1b, vacuum device 1c, compressor 1d, small air-water separation tank 1e, and mineral particle mixed water tank 1f (shown in Figure 4) are located on top of the swivel 2a shown in Figure 7. The cables and hoses are handled by an automatic retractor. This eliminates the complex movement of the associated equipment. The small air-water separation tank 1e is not generally required, but is installed as a precaution.

[0041] Figure 8 is a plan view showing the process of unloading dredged soil from a vacuum bucket 1 mounted on a vacuum bucket dredger 2 onto a soil barge. In the figure, 3 is the soil barge. Figure 8 shows the situation in which the swivel table 2a rotates 90 degrees to unload dredged soil onto the soil barge 3. The operation room 2b is located in front of the vacuum bucket 1. [Explanation of symbols]

[0042] 1 vacuum bucket 11 Drain check valve 12 Vacuum valve 13 Compressed air valve 14. Water jet pressure valve 15 Vertical water pipe 16 Lifting equipment 17 Rope 1a Underwater vibration device 1b Winch 1c vacuum device 1d Compressor 1e Small air-water separation tank 1f Mineral particle mixed water tank 1g Ceiling drain 1h bulkhead 1i Water jet pipe 2 Vacuum Bucket Dredger 21 barge 22 Posts 23 horizontal boom 24 Counterweight 25 Pulley 2a Turning machine 2b Control room 3 Soil Carrier A water surface B Underwater C Underwater ground

Claims

1. In the vacuum bucket dredging method, the use of vacuum pressure is limited to the suction force that prevents the dredged soil in the vacuum bucket from falling due to its own weight.The adhesive force of the dredged surface of the bottom ground when the vacuum bucket is lifted, which contributes to this falling due to its own weight, is cut horizontally with a water jet mixed with mineral particles, and the negative pressure generated on the dredged surface is eliminated by supplying water through a vertical water pipe.This vacuum bucket dredging method is characterized by keeping the required vacuum pressure to a level that is extremely easy to manage and also by miniaturizing the vacuum equipment.

2. In the vacuum bucket of claim 1, the bucket has a box-like structure with an open bottom, and on the top of the bucket there are an underwater vibration device, a check valve for drainage, a vacuum valve connected to a vacuum device, and an air pressure valve connected to a compressor. On the ceiling inside the bucket there is a ceiling drain connected to the vacuum valve, air pressure valve, and check valve. The interior space of the bucket is divided into separate spaces by partitions, leaving the bottom part undivided. Inside the bucket wall there are a plurality of vertical water pipes pointing downward in one direction, and a water jet pipe with numerous horizontal injection holes connected to a compressor installed in a loop inside the bottom for pumping water mixed with mineral particles. The underwater vibration device and drainage check valve are used when pouring the bucket, the water jet pipe horizontally sprays a water jet mixed with mineral particles when the bucket is lifted, horizontally cutting the adhesion of the dredged surface to the ground, and the vertical water pipe supplies water to eliminate the negative pressure that occurs on the dredged surface when the bucket is lifted.By limiting the use of vacuum pressure to the suction force against the dredged soil falling under its own weight, the required vacuum pressure is kept to a level that is extremely easy to manage and the vacuum device is made smaller, this is a vacuum bucket characterized by these multiple functions.

3. A vacuum bucket dredging method for poor ground as claimed in claim 1, characterized in that the mixed mineral particles of the water jet are mineral particles containing iron that dissolve in seawater to become iron salts, thereby suppressing the generation of hydrogen sulfide and turbidity from the poor ground.

4. In the dredging method of claim 1 intended for a water bottom ground with an extremely soft surface, the vacuum bucket is landed on the water bottom ground and vibration poured, and even when the ceiling drain surface of the bucket comes into contact with the ground, vibration pouring is continued to vibrate and consolidate the surface layer of the ground, and after consolidation is completed, the vacuum valve is opened to reduce the pressure, generating a suction force on the ceiling drain surface to hold the dredged soil in place.By dividing the roles in this way, with consolidation being performed by vibration load and retention of the dredged soil by vacuum pressure suction force, the required vacuum pressure can be kept to a level that is extremely easy to manage, and the vacuum device can be made smaller.This is a vacuum bucket dredging method intended for a water bottom ground with an extremely soft surface, characterized in that the vacuum bucket is landed on the water bottom ground and vibration poured, and even when the ceiling drain surface of the bucket comes into contact with the ground, vibration pouring is continued to vibrate and consolidate the surface layer of the ground, and after consolidation is completed, the vacuum valve is opened to reduce the pressure, generating a suction force on the ceiling drain surface to hold the dredged soil in place.

5. 2. The vacuum bucket structure of claim 1, wherein the ceiling drain is a multi-layered drain sheet that also serves as a screen, making the ceiling drain extremely thin, thereby minimizing the vacuum space required to be evacuated and shortening the decompression time, thereby minimizing the size of the vacuum device.

6. 1. A vacuum bucket dredger for use in the vacuum bucket dredging method of claim 1, characterized in that the dredger's structure is such that a large swivel is installed forward in line with the longitudinal centerline of the barge, and four equidistant struts are erected around the periphery of the swivel to form a three-dimensional support column connected at the top by multiple girders, and two horizontal booms are fixed in parallel to the top of the three-dimensional support column, and a vacuum bucket is suspended at one end of each of these by multiple ropes connected to multiple winches, and a counterweight is attached to the other end, thereby creating a stable and compact structure, and the top of the swivel is equipped with a vacuum device and water jet pipe connected to the multiple winches and the vacuum valve of the vacuum bucket, and a compressor connected to the compressed air valve, etc., and the relationship between the vacuum bucket and related equipment is arranged and constructed so that the rotation of the swivel is not hindered.

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