Dredging facility and dredging method

Abstract

To provide a dredging facility and a dredging method that are less susceptible to the influence of wind and waves and enable efficient dredging.SOLUTION: A dredging facility 1 comprises a submerged breakwater 10 provided upstream of an intake 6, and a pier 30 extending from land to an upstream side of the submerged breakwater 10. The submerged breakwater 10 preferably comprises a main body 11 formed by stacking bags 14, 14 filled with stone, a concrete layer 12 covering the upstream side of the main body 11, and a scour prevention member 13 installed on an upper surface of the concrete layer 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a dredging facility and a dredging method. [Background technology]

[0002] In facilities that take in water from a partitioned area in the sea or a river, it is necessary to dredge sediment from the bottom of the water to prevent sediment from covering the intake. A known method of dredging the sea or river involves using a crane or backhoe bucket installed on a floating barge to scrape the bottom of the water and then sucking the sediment up through a sediment discharge pipe (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-97343 Summary of the Invention [Problem to be solved by the invention]

[0004] Dredging from a barge is susceptible to the effects of wind and waves, and measures to counter these must be taken, making the dredging work more complicated. From this perspective, an object of the present invention is to provide a dredging facility and a dredging method that are less susceptible to the effects of wind and waves and enable efficient dredging. [Means for solving the problem]

[0005] The first invention to solve these problems is a dredging facility characterized by comprising a submerged breakwater located upstream of the intake and a pier extending from land to the upstream side of the submerged breakwater. According to the dredging facility of the present invention, dredging can be carried out from a pier extending from land to the upstream side of the submerged breakwater, making it less susceptible to the effects of wind and waves and easier to carry out. Furthermore, dredging is carried out by damming up sediment with the submerged breakwater, allowing for efficient dredging. Furthermore, the submerged breakwater makes it difficult for sediment to flow into the intake, so it does not interfere with water intake work.

[0006] In the dredging facility of the present invention, the submerged breakwater preferably comprises a main body formed by stacking bags filled with stone, a concrete layer covering the upstream side of the main body, and a scour prevention member installed on the upper surface of the concrete layer. With this configuration, the submerged breakwater can be easily constructed, is less likely to collapse due to water currents, and is highly stable. In the dredging facility of the present invention, a sand barrier is preferably provided upstream of the submerged breakwater and the pier. The sand barrier may be formed, for example, by removing the upper part of a permeation prevention wall that prevents seawater from flowing into the managed area from the sea and positioning the upper end of the permeation prevention wall that remains in the sea between the seabed and the sea surface, thereby changing the state to allow seawater to flow into the managed area from the sea. With this configuration, the sand barrier can prevent sand from flowing into the managed area upstream of the submerged breakwater and the pier while allowing new water to flow in.

[0007] The second invention for solving the above problem is a dredging method characterized by depositing sediment upstream of a submerged breakwater installed upstream of a water intake, and dredging the sediment from a pier extending from land to the upstream side of the submerged breakwater. According to the dredging method of the present invention, dredging is performed from a pier extending from land to the upstream side of the submerged breakwater, making it less susceptible to wind and waves and easier to carry out. Furthermore, dredging is performed by damming up sediment with the submerged breakwater, allowing for efficient dredging. Furthermore, the submerged breakwater makes it difficult for sediment to flow into the intake, so it does not interfere with water intake work. [Effects of the Invention]

[0008] According to the dredging facility and dredging method of the present invention, dredging can be carried out efficiently without being affected by wind or waves. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a plan view showing a dredging facility according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view taken along line ii-ii in Figure 1, showing a submerged breakwater for dredging facilities relating to an embodiment of the present invention. [Figure 3] This is a cross-sectional view taken along line iii-iii in Figure 1, showing a submerged breakwater for dredging facilities according to an embodiment of the present invention. [Figure 4] FIG. 1 is a plan view showing a pier of a dredging facility according to an embodiment of the present invention. [Figure 5] 1 is a cross-sectional view showing a pier of a dredging facility according to an embodiment of the present invention. [Figure 6] 1 is a perspective view showing a sand barrier of a dredging facility according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] A dredging facility and a dredging method according to an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 is a plan view of the dredging facility, Figure 2 is a cross-sectional view of the submerged breakwater of the dredging facility taken along line ii-ii in Figure 1, Figure 3 is a cross-sectional view of the submerged breakwater of the dredging facility taken along line iii-iii in Figure 1, Figure 4 is a plan view of the pier of the dredging facility, Figure 5 is a cross-sectional view of the pier of the dredging facility, and Figure 6 is a perspective view of the sand protection bund of the dredging facility.

[0011] First, the configuration of the dredging facility will be described. As shown in FIG. 1, the dredging facility 1 of this embodiment is installed in an area 5 defined by a quay wall 2, a breakwater 3, and a partition wall 4. The breakwater 3 is a permeable breakwater formed by piling up wave-dissipating blocks, rocks, etc., and extends offshore from the quay wall 2. A water supply channel 7 is formed in the breakwater 3. The water supply channel 7 is used to supply water from the outside to the inside of the area 5. Gaps between the wave-dissipating blocks and other components that make up the breakwater 3 form the water supply channel 7. A partition wall 4 is installed on the right side (downstream side) of the quay wall 2. The partition wall 4 blocks water downstream of the water intake 6. A water intake 6 is formed in the quay wall 2 to draw water from within the area 5. It is preferable that sediment does not flow into the water intake 6. Within the area 5, the side closer to the water supply channel 7 is the upstream side, and the side closer to the water intake 6 is the downstream side.

[0012] The dredging facility 1 comprises a submerged breakwater 10, a pier 30, and a sand barrier levee 50. Submerged breakwater 10 is a breakwater that prevents sediment from flowing into the vicinity of intake 6 and is installed on the water bottom upstream of intake 6. Submerged breakwater 10 extends approximately perpendicular to quay wall 2. Submerged breakwater 10 extends from quay wall 2 to breakwater 3 (breakwater 3 extending left and right in Figure 1) facing quay wall 2. As also shown in Figures 2 and 3, submerged breakwater 10 comprises a main body 11, a concrete layer 12, and a scour prevention member 13. Main body 11 is formed by stacking bag bodies 14 filled with stone. Bag bodies 14 are cylindrical, weighing, for example, 1 ton, with a diameter of 1700 mm and a height of 400 mm. Bag bodies 14 are arranged in multiple rows on the water bottom along the extension direction of submerged breakwater 10. The number of bag bodies 14 decreases with each row toward the upper level, resulting in a triangular cross-section that narrows at the top. Specifically, the bag bodies 14 in the lowest tier are arranged in five rows, for a total of five tiers, and the bag bodies 14 in the top tier are arranged in a single row. The bottoms at both longitudinal ends of the submerged breakwater 10 are inclined so that they become higher toward the ends in accordance with the slope of the water bottom.

[0013] The concrete layer 12, which prevents the bag bodies 14 of the main body 11 from shifting, is laid upstream of the main body 11. The concrete layer 12 is a long plate extending in the longitudinal direction of the main body 11. The thickness of the concrete layer 12 is smaller than that of the bag bodies 14. Backfilling broken gravel 15 is spread on the step between the bag bodies 14 of the main body 11 located below the concrete layer 12, forming a flat inclined surface. The concrete layer 12 has a lower horizontal portion 16a, an inclined portion 16b, and an upper horizontal portion 16c. The lower horizontal portion 16a is laid on the bottom of the water upstream of the main body 11 and has a width of, for example, 2000 mm. The inclined portion 16b is continuous with the downstream end of the lower horizontal portion 16a and bends diagonally upward. The inclined portion 16b extends and slopes from the bottom of the water to the height of the top surface of the third bag body 14. The upper horizontal portion 16c is continuous with the downstream end (upper end) of the inclined portion 16b and is bent horizontally toward the downstream side. The downstream end of the upper horizontal portion 16c abuts against the upstream side surface of the fourth bag body 14. Scour prevention member 13 is intended to prevent scouring of the surface of concrete layer 12, and is composed of bags 17 filled with stone material. Bags 17 of scour prevention member 13 may be the same as bags 14 of main body 11, and are installed on the upper surface of concrete layer 12. Bags 17 are arranged in a row along the longitudinal direction of concrete layer 12 so as to cover the bend between lower horizontal portion 16a and inclined portion 16b of concrete layer 12. With scour prevention member 13, soil and sand that flows over the upper surface of lower horizontal portion 16a of concrete layer 12 is blocked by bags 17 and does not collide with the connection between lower horizontal portion 16a and inclined portion 16b, thereby preventing scouring of concrete layer 12.

[0014] The pier 30 is used to carry dredging heavy machinery 40 such as a crane and transport vehicles 41 such as dump trucks for dredging, and it projects from the quay 2 (land) toward the upstream side of the submerged breakwater 10. The pier 30 has a rectangular shape that is longer offshore. The pier 30 comprises a pier section 31, a frame section 32, and a deck section 33. The pier section 31 is the section that serves as the leg that supports the pier 30, and is equipped with a steel pipe pile 34a and an external pipe 34b. The upper end of the steel pipe pile 34a is located at a height that supports the frame section 32, and the lower end is buried to a depth that allows support in the water bottom 8. The external pipe 34b is a tubular member that is placed over the upper end of the steel pipe pile 34a, and serves to connect the frame section 32. Reinforcing braces 36 are suspended at appropriate positions between adjacent external pipes 34b, 34b.

[0015] The frame section 32 is the base for laying the deck section 33, and is installed on the pier section 31. The frame section 32 is equipped with a support girder 35a and a main girder 35b. The support girder 35a is a girder that supports the main girder 35b, and is connected to the upper end of the external pipe 34. The support girder 35a extends along the short side of the pier 30. The main girder 35b extends along the longitudinal direction of the pier 30 and is perpendicular to the support girder 35a in a plan view. The main girders 35b are arranged in multiple rows at predetermined intervals in the short side of the pier 30. Reinforcing braces 36 are arranged in a truss shape between adjacent main girders 35b, 35b. The deck 33 is made up of a flat rectangular covering plate and is suspended over the main girder 35b. Handrails 37 (see FIG. 5) are erected on the side edges and tip of the periphery of the pier 30.

[0016] The sand barrier dyke 50 is a dyke for preventing sediment from flowing into the area where the pier 30 and the submerged breakwater 10 are installed. As shown in FIG. 1 , the sand barrier dyke 50 is installed upstream of the submerged breakwater 10 and the pier 30 to prevent sediment from flowing in while allowing seawater to flow from the upstream side of the area 5 (the sea) to the downstream side of the area 5 (the management area). The sand barrier dyke 50 is made of steel sheet piles. The sand barrier dyke 50 of this embodiment is a modified version of an existing permeation prevention wall 51. Before being modified, the permeation prevention wall 51 was a water-impermeable wall for preventing seawater from flowing in from the sea to the management area, with its lower end buried in the waterbed 8 and its upper end protruding above the water surface. The sand barrier dyke 50 is constructed by removing the upper wall 52 of the permeation prevention wall 51 and positioning the upper end 53 of the permeation prevention wall 51, which remains in the sea, between the seabed 54 and the sea surface 55. The upper wall 52 of the permeation prevention wall 51 is removed by cutting the steel sheet pile horizontally at a predetermined height. The underwater cutting work is performed using oxygen arc cutting equipment.

[0017] Next, a dredging method using the dredging facility 1 according to this embodiment will be described. The dredging method according to this embodiment is characterized in that sediment is deposited upstream of a submerged breakwater 10 provided upstream of the intake 6, and the sediment blocked (deposited) by the submerged breakwater 10 is dredged from a pier 30 extending from the quay 2 (land) to the upstream side of the submerged breakwater 10. At the pier 30, a dredging machine 40 installed on the pier 30 scoops up the sediment from the bottom 8 of the water, and loads it onto a transport vehicle 41 for discharge.

[0018] The following describes the effects of the dredging facility 1 and dredging method of this embodiment. With this dredging facility 1, dredging can be performed from a pier 30 fixed to land, making dredging less susceptible to wind and waves and easier to carry out. Since the pier 30 extends upstream of the submerged breakwater 10, sediment held back by the submerged breakwater 10 can be efficiently dredged from the pier 30. Furthermore, the submerged breakwater 10 makes it difficult for sediment to flow into the intake 6, so it does not interfere with water intake work. Dredging may also be performed upstream of the sand barrier breakwater 50 from the pier 30. Submerged breakwater 10 can be easily constructed as it comprises a main body 11 formed by piling up bags 14 filled with stone, a concrete layer 12 covering the upstream side of main body 11, and scour prevention members 13 installed on the upper surface of concrete layer 12. Furthermore, the concrete layer 12 is less susceptible to scouring, and submerged breakwater 10 is less likely to collapse due to water flow, which increases the stability of submerged breakwater 10.

[0019] Furthermore, a sand barrier dyke 50 is provided upstream of the submerged breakwater 10 and the pier 30, which allows the inflow of new water while suppressing the inflow of sand upstream of the submerged breakwater 10 and the pier 30. This reduces the inflow of sediment around the pier 30, thereby reducing the amount of sediment to be dredged and the amount of work required. The sand barrier dyke 50 is formed by cutting the upper end of the existing permeation prevention wall 51, making construction easy.

[0020] Although the embodiments for carrying out the present invention have been described above, the present invention is not limited to these embodiments, and appropriate design changes are possible without departing from the spirit of the present invention. For example, in the above embodiment, the submerged breakwater 10 comprises a main body 11, a concrete layer 12, and a scour prevention member 13, but the present invention is not limited to these. The submerged breakwater only needs to be stably installed on the water bottom 8 and prevent sediment from flowing into the intake 6. In the above embodiment, the pier 30 includes a pier portion 31, a frame portion 32, and a floor plate portion 33, and is rectangular in plan view, but this is not limited to this. The pier may have a shape and configuration different from those in the above embodiment, as long as it is connected to the quay 2 and can carry the dredging heavy equipment 40 and the transport vehicle 41. In addition, the pier 30 may be formed on top of the sand barrier levee 50, or may be formed upstream of the sand barrier levee 50. The sand barrier levee 50 may be omitted. [Explanation of symbols]

[0021] 1 Dredging facilities 2. Quay (land) 6 Water Intake 8 Underwater (seafloor) 9 Water surface (sea surface) 10 Submerged Embankment 11 Main body 12 Concrete layer 13 Scour prevention material 14 Bag body 30 Pier 50 Sand control dike 51 Transmission prevention wall 53 Top

Claims

1. A submerged breakwater installed upstream of the intake; and a pier leading from the land to the upstream side of the submerged breakwater. A dredging facility characterized by:

2. The submerged breakwater comprises a main body formed by stacking bags filled with stone, a concrete layer covering the upstream side of the main body, and a scour prevention member installed on the upper surface of the concrete layer.

2. The dredging facility according to claim 1 .

3. A sand barrier is provided upstream of the submerged breakwater and the pier, The sand barrier was formed by removing the upper part of the permeation prevention wall that prevents seawater from flowing into the management area from the sea, and positioning the upper end of the permeation prevention wall that remains in the sea between the seabed and the sea surface, thereby changing the state to allow seawater to flow into the management area from the sea. The dredging facility according to claim 1 or 2.

4. Sediment is deposited upstream of the submerged breakwater located upstream of the intake. The soil and sand will be dredged from the pier leading from the land to the upstream side of the submerged breakwater. A dredging method characterized by the above.

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