Decomposition stable type filter method and sand prevention structure for harbor facility

Abstract

To provide a decomposition stable type filter method and a sand prevention structure for harbor facilities capable of exerting high sand prevention performance by simple construction.SOLUTION: A surface of a back-filling stone 12 is covered with a decomposition stable type filter 30. The decomposition stable type filter 30 composes a bag body 31 and a filter material 32, wherein the bag body 31 is formed by assembling a soluble or decomposable lower sheet 31a and an upper sheet 31b with sand prevention performance. The decomposition stable type filter 30 is installed while bringing the lower sheet 31a in contact with a surface of the back-filling stone 12, and after the lower sheet 31a of the decomposition stable type filter 30 is broken, the filter material 32 discharged from the decomposition stable type filter by its own weight forms a stone material filter layer by penetrating between stone materials in a surface layer part of the back-filling stone 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a decomposition-stabilization type filter construction method and a sand-control structure for port facilities. [Background technology]

[0002] As shown in Figure 7, a sand-control structure for a port facility is known in which a caisson body b is placed on a foundation mound a, and backfill stones c made of broken granite or the like, a sand-control sheet d, and fill soil e are formed in that order on the rear side (land side) of the caisson body b (Patent Documents 1 and 2). In this sand-control structure, the sand-control sheet d covering the surface of the backfill stone c prevents the fill soil e from being sucked out.

[0003] In actual construction, the fill soil e is not buried immediately after laying the sand control sheet d, and due to construction planning, it may take several years before backfilling with the fill soil e can begin. It is known that at such construction sites, after the sand-control sheet d is laid, it is left exposed for a long period of time.

[0004] Furthermore, the sand control structure of a port facility shown in Figure 8 is known. The sand control structure of this port facility is formed on the rear side (land side) of the caisson body b, in the following order: backfill stone c (broken granite stones, etc.), filter layer h, sand control sheet d, and fill soil e. The filter layer h is a stone material such as crushed stone having a diameter intermediate between the diameters of the backfill stone c and the fill soil e, and covers the back surface of the backfill stone c. In this sand control structure, the filter layer h and sand control sheet d work together to prevent the suction of fill soil e. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6283765 (Figure 8) [Patent Document 2] Patent No. 6327691 (Figure 1) Summary of the Invention [Problem to be solved by the invention]

[0006] The sand control technology for port facilities shown in Figure 7 involves the following problems: <1> In sand-control structures, sand-control sheets d are not only susceptible to damage during installation and while left unattended, but also after installation, they are damaged by repeated waves transmitted through the joints and the foundation mound. If the sand-control sheet d is damaged and breaks, there is a risk that the fill soil e will leak out through the broken part f. <2> When landfill soil e flows out, a cavity g is created inside the landfill soil e, and if cavity g grows large, there is a risk of it causing a sinkhole on the ground surface in the coastal area.

[0007] The sand control technology for port facilities shown in Figure 8 involves the following problems: <1> It is extremely difficult to lay stone material in a uniform thickness on the surface of the sloped backfill stone c to form a filter layer h. Therefore, the workability when forming the filter layer h is poor and the work cost is high. <2> The stone materials for the filter layer include a variety of large and small stones with different particle sizes. If these stones are dumped from the sea, smaller stones will be washed away during the settling process, resulting in stone loss. <3> When small-diameter stones are washed away, the filtering function of filter layer h decreases significantly in proportion to the amount of stones washed away. <4> In order to prevent small-diameter stones from being washed away, one method is to use a pipe to introduce stones for the filter layer, but forming a filter layer using a pipe requires a lot of time and effort, which poses problems in terms of ease of construction and construction costs. <5> If the sand-control sheet d is left exposed for a long period of time, it may tear, and the stones of the filter layer h may be susceptible to erosion and collapse at the water's edge.

[0008] In order to solve the above-mentioned problems, the present invention aims to provide a decomposable and stable filter construction method and a sand-control structure for port facilities that can exhibit high sand-control performance with simple construction. [Means for solving the problem]

[0009] The present invention is a decomposition-stable filter method for preventing the suction of the fill soil by installing a port facility on a foundation mound and providing backfill stones and fill soil on the rear side of the port facility, the surface of the backfill stones is covered with a decomposition-stable filter having a fail-safe function, the decomposition-stable filter is composed of a bag body formed by combining upper and lower sheets of different materials, and a stone filter material sealed in the bag body, the bag body has a bottomed structure combining a lower sheet made of a soluble or decomposable sheet material and an upper sheet having a sand-proofing function, the lower sheet of the decomposition-stable filter is laid in contact with the surface of the backfill stones, and the fill soil is filled and buried in contact with the upper sheet, and when the lower sheet is broken by the weight of the decomposition-stable filter, the filter material released from the decomposition-stable filter penetrates between the stones in the surface layer of the backfill stones to form a stone filter layer on the surface layer of the backfill stones, and the stone filter layer and the upper sheet work together to provide a sand-proofing function. The present invention is a sand-prevention structure for a port facility, in which a port facility is installed on a foundation mound, and backfill stones and fill soil are provided on the rear side of the port facility, the surface of the backfill stones is covered with a decomposable and stable filter having a fail-safe function, the decomposable and stable filter is composed of a bag body formed by combining upper and lower sheets of different materials, and a stone filter material sealed in the bag body, the bag body has a bottom structure combining a lower sheet made of a soluble or decomposable sheet material and an upper sheet having a sand-prevention function. The decomposition-stabilized filter has its lower sheet laid in contact with the surface of the backfill stone, and is buried in contact with the upper sheet with landfill soil. Before the lower sheet is torn, the filter material and upper sheet work together to provide a sand-proofing function, and after the lower sheet of the decomposition-stabilized filter is torn, the filter material released from the decomposition-stabilized filter under its own weight penetrates between the stones on the surface of the backfill stone, and the stone filter layer formed on the surface of the backfill stone works together with the upper sheet to provide a sand-proofing function. In another embodiment of the present invention, the lower sheet of the degradation-stabilized filter is made of a biodegradable sheet. In another embodiment of the present invention, the upper sheet of the decomposition-stabilized filter is any one of a high-strength multi-layered fabric, a high-strength nonwoven fabric sheet, and a high-strength civil engineering sheet. In another embodiment of the present invention, the overall shape of the decomposition-stabilizing filter is any one of a rod shape, a mat shape, and a cushion shape. In another embodiment of the present invention, the decomposition-stable filters are laid out on the surface of the backfill stone without any gaps. In another embodiment of the present invention, the filter material is a mixture of stones of different sizes, the size of which is smaller than that of the backfill stones and equal to or smaller than that of the landfill soil. In another aspect of the invention, the port facility is a new port facility or an existing port facility. Effect of the Invention

[0010] With the above-mentioned configuration, the present invention has at least one of the following effects. <1> The combination of a decomposition-stabilizing filter and backfill stones provides excellent sand-control performance. <2> The decomposable and stable filter, made by sealing the filter material in a bag, is simply laid on the surface of the backfill stone, allowing the work of forming the filter material in a uniform thickness on the sloping surface of the backfill stone and the work of laying the top sheet with sand-proofing properties to be carried out simultaneously. Therefore, sand control work on the rear side of the port facility can be carried out economically within a short period of time. <3> The decomposition-stable filter is designed so that after a certain period of time has passed since its installation, the filter material within the bag is released under its own weight. As a result, the internal filter material penetrates between the stones of the backfill stone, and a stone filter layer with extremely high filtering performance is automatically formed on the surface of the backfill stone without human assistance. <4> If the particle size of the filter material varies, 100% of the sand prevention function cannot be guaranteed, and if the upper sheet is damaged during installation, 100% of the sand prevention function cannot be guaranteed. The stone filter layer can eliminate the sand-proofing risks of these filter materials and the upper sheet, and can provide excellent durability and high filtering function. <5> Since the filter material is sealed in the bag, scattering of the filter material can be reliably prevented not only during application but also after application, and loss of the filter material can be eliminated. <6> Since the filter material is laid down in a state in which it is sealed in a bag in advance, the layer thickness of the filter material can be made uniform. <7> Until the lower sheet is torn, the filter material of the decomposition-stable filter works in cooperation with the upper sheet to provide high sand-proofing performance. <8> Even if the upper sheet is damaged, the stone filter layer can maintain its sand-prevention function, so that the suction of landfill soil can be prevented for a long period of time. <9> The present invention can be applied not only to new port facilities, but also to repair work on existing port facilities. [Brief description of the drawings]

[0011] [Figure 1] Diagram of the decomposition-stabilized filter method [Diagram 2]In this diagram, (A) is a model of a rod-shaped filter, (B) is a model of a mat-shaped filter, and (C) is a model of a cushion-shaped filter. [Diagram 3] Enlarged cross-sectional view of the boundary between the backfill stone, the decomposition-stabilized filter, and the landfill soil before the filter material is discharged. [Figure 4] Enlarged cross-sectional view of the boundary between the backfill stone and the decomposition-stabilized filter after the filter material is released. [Diagram 5] An explanatory diagram of a manufacturing example of a decomposition-stabilized filter [Figure 6] Diagram of the protective structure of a port facility with decomposition-stabilizing filters laid on the surface of the backfill stone [Figure 7] An explanatory diagram of a conventional sand-control structure for port facilities that prevents the suction of fill soil by using a sand-control sheet laid on the surface of backfill stones. [Figure 8] An explanatory diagram of the sand-control structure of other conventional port facilities, which uses a filter layer and sand-control sheet laid on the surface of the backfill stone to prevent the suction of fill soil. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will now be described with reference to the drawings.

[0013] <1> Port facilities Referring to FIG. 1, the port facility on which the present invention is based includes concrete revetments and quays.

[0014] In this example, a case will be described in which the port facility is a caisson-type revetment. A caisson body 10 is placed on a foundation mound 11, and backfill stones 12 (broken granite stones, etc.) and fill soil 20 are provided on the rear side (land side) of the caisson body 10.

[0015] <2> Decomposition-stable filter In the present invention, in order to prevent the suction of the fill soil 20, the surface of the backfill stones 12 is covered with a decomposable and stable filter 30 having a fail-safe function. The decomposition-stabilized filter 30 is a sand-prevention structure that is laid out without gaps on the surface of the backfill stones 12. The decomposition-stable filter 30 comprises a bag 31 in which upper and lower sheets are combined with different materials, and a stone filter material 32 sealed in the bag 31. The overall shape of the decomposition-stabilizing filter 30 is not particularly limited, and for example, any one of the shapes illustrated in FIG. 2 can be applied. FIG. 2A shows the decomposition-stabilized filter 30 in a rod-like overall shape, (B) shows a mat-like shape, and (C) shows a cushion-like shape (circular or square, etc.).

[0016] The mat-like form includes a form in which a plurality of rod-like bodies are arranged in parallel and integrated into a raft-like form. The cushion-like shape includes a shape having a circular or rectangular planar shape.

[0017] The capacity of the decomposition-stabilizing filter 30 can be appropriately selected.

[0018] <2.1> Bag body Explaining with reference to FIG. 3, the bag body 31 is a flexible bag body with a bottomed structure, and has a lower sheet 31a in contact with the surface of the backfill stones 12 and an upper sheet 31b in contact with the landfill soil 20. The lower sheet 31a and the upper sheet 31b are overlapped and their peripheral portions are joined to form a bag body having a bottom. A single or multiple openings are provided in a part of the bag 31, and the inside of the bag 31 is filled with the filter material 32 through these openings, thereby producing the disintegration-stable filter 30.

[0019] <2.1.1> Lower sheet The lower sheet 31a is made of a dissolvable or degradable sheet material so that it can disappear after the decomposition-stable filter 30 is laid down, thereby releasing the filter material 32. The material of the lower sheet 31a may be, for example, a biodegradable sheet. Although the entire surface of the lower sheet 31a is made of a soluble or decomposable material, the lower sheet 31a may be made of a soluble or decomposable material only in a portion thereof.

[0020] Until the installation of the decomposition-stable filter 30 is completed, the lower sheet 31a does not dissolve or decompose and maintains its function of containing the filter material 32. At a predetermined time after the installation of the decomposition-stable filter 30, the strength of the lower sheet 31a decreases significantly so that the filter material 32 can be released.

[0021] The time when the lower sheet 31a breaks and loses its function of containing the filter material 32 can be appropriately adjusted by selecting the material of the lower sheet 31a, the sheet thickness, etc.

[0022] The lower sheet 31a is configured to reduce its strength after the decomposition-stabilized filter 30 is laid in order to release the filter material 32 from the decomposition-stabilized filter 30 and form a stone filter layer 40 on the surface of the backfill stone 12 (Figure 4).

[0023] <2.1.2> Upper sheet The upper sheet 31b is a non-soluble or non-degradable high-strength sheet material having a sand-proofing function. As the upper sheet 31b, for example, a sheet-like material having a sand-proofing function, such as a high-strength multi-layered fabric, a high-strength nonwoven fabric sheet, or a high-strength construction sheet, can be used.

[0024] <2.2> Filter material The bag 31 contains a filter material 32 which is a stone material for a filter. The filter material 32 has an appropriate particle size ratio with respect to the backfill stones 12 and the landfill soil 20 . The particle size ratio of the filter material 32 to the backfill stones 12 is greater than the particle size ratio of the filter material 32 to the landfill soil 20 .

[0025] The filter material 32 is a mixture of stones of different sizes, each of which has a smaller diameter than the backfill stones and a particle size equal to or smaller than the landfill soil 20. As the filter material 32 that is actually used, in addition to using stone materials with different particle sizes, including soil particles and gravel, it is also possible to use soil with the same particle size as the landfill soil 20.

[0026] Since the filter material 32 is contained in the bag body 31 and used as a unit, separation or leakage of the filter material 32 in the sea during construction work or immediately after installation can be effectively prevented.

[0027] <3> Manufacturing method for decomposition-stable filter The decomposition-stable filter 30 is manufactured near the site or manufactured in a factory with a well-established manufacturing environment and then transported to the site for use.

[0028] A method for producing the decomposition-stabilized filter 30 illustrated in FIG. 5 will be described. A bag body 31 is prepared in which a plurality of tubes 33 each having a bottom structure are formed in a linked manner. The bag body 31 is supported vertically with the multiple filling ports 34 facing directly upward. The filter material 32 is stored in a filling hopper 35 disposed above the bag body 31 . After the filter material 32 is filled into the bag body 31 through the openings 34 in the filling hopper 35, the respective filling openings 34 are closed to produce the disassembly-stable filter 30. The manufacturing method of the decomposition-stable filter 30 is not limited to this example, and the filter 30 is manufactured taking into consideration the overall shape of the bag 31, the capacity of the bag 31, and the like.

[0029] [Decomposition-stable filter method] This paper explains the decomposable and stable filter method (a method for preventing sand buildup at port facilities).

[0030] 1. Application example for newly constructed port facilities The sand control method applied to the newly constructed port facilities will be explained with reference to Figure 6.

[0031] <1> Port facility construction work A caisson body 10 is placed on a foundation mound 11, and backfill stones 12 are formed on the rear side (land side) of the caisson body 10.

[0032] <2> Installation of decomposition-stable filters Next, the decomposition-stable filter 30 described above is laid on the surface of the backfill stone 12. A decomposition-stable filter 30 is laid on the surface of the backfill stone 12. At this time, the lower sheet 31a of the decomposition stable filter 30 is laid facing the backfill stone 12, and the upper sheet 31b is laid facing in the direction in which the backfill stone 12 is separated.

[0033] In the present invention, the filter material 32 of the decomposition-stable filter 30 is pre-packaged in a bag, so that the work of forming the filter material 32 with a uniform thickness on the surface of the backfill stone 12 and the work of laying the upper sheet 31b, which also serves as a sand-proof sheet, can be performed simultaneously by the simple task of simply laying the decomposition-stable filter 30. This results in much improved workability compared to performing these two tasks separately.

[0034] Furthermore, since the filter material 32 is sealed in the bag body 31, the filter material 32 can be reliably prevented from diffusing even if the decomposition-stable filter 30 is subjected to wave force, and not only is there no loss of the filter material 32, but the filter material 32 can also be effectively prevented from being eroded and destroyed.

[0035] 2. Application examples to existing port facilities With reference to Figure 1, we will explain the sand control method applied to existing port facilities. The decomposition-stable filter 30 can be applied not only to new port facilities, but also to repair works of existing port facilities.

[0036] When applied to repair work on existing port facilities, the process involves the first step of sealing and closing the joints in the caisson body 10, the second step of excavating the fill soil 20, the third step of laying a decomposable and stable filter 30 on the surface of the exposed backfill stone 12, and the fourth step of backfilling the fill soil 20.

[0037] [Sand-proof function of decomposition-stable filter] The sand-proofing function of the decomposition-stable filter 30 before and after the release of the filter material 32 will be described.

[0038] <1> Before release of filter material FIG. 3 shows an enlarged view of the boundary between the decomposition-stabilized filter 30 and the backfill stone 12 before the lower sheet 31a of the decomposition-stabilized filter 30 laid on the surface of the backfill stone 12 is broken.

[0039] Since the lower sheet 31a maintains a predetermined strength until a predetermined period of time has elapsed after the decomposition-stable filter 30 is laid, the filter material 32 is maintained in a contained state.

[0040] The filter material 32 has a sand-proofing function, and the upper sheet 31b has a sand-proofing sheet function (first fail-safe function). Therefore, when the rear side of the decomposition-stabilizing filter 30 is filled with landfill soil 20, the decomposition-stabilizing filter 30 as a whole functions as a sand-control structure, and can reliably prevent the landfill soil 20 from being sucked out.

[0041] <2> After the filter material is discharged FIG. 4 shows an enlarged view of the boundary between the decomposition-stabilized filter 30 and the backfill stone 12 when the lower sheet 31a of the decomposition-stabilized filter 30 laid on the surface of the backfill stone 12 is torn.

[0042] When a predetermined period of time has passed since the decomposition-stable filter 30 was laid, the lower sheet 31a dissolves or decomposes, causing a significant decrease in strength. When the strength of the lower sheet 31a is reduced, the filter material 32 breaks through the lower sheet 31a due to its own weight and falls. A portion of the filter material 32 released from the decomposition-stabilized filter 30 penetrates between the stones on the surface layer of the backfill stones 12 and forms a stone filter layer 40 on the surface layer of the backfill stones 12.

[0043] By adjusting the time when the lower sheet 31a disappears, the time when the stone filter layer 40 is roughly formed can be adjusted appropriately.

[0044] The stone filter layer 40, which is formed by combining the filter material 32 and the backfill stones 12, exhibits high sand-proofing properties. Furthermore, the upper sheet 31b that remains in the decomposition-stable filter 30 without being lost functions as a sand-proof sheet.

[0045] That is, the stone filter layer 40 and the upper sheet 31b cooperate to provide a sand-proofing function (second fail-safe function). Therefore, even if the upper sheet 31b is damaged, the stone filter layer 40 maintains its sand-proofing function and can prevent the suction of the fill soil 20 for a long period of time (long-term durability). [Explanation of symbols]

[0046] 10 Caisson structure 11. Foundation mound 12. Backfill stone 20. Landfill soil 30. Decomposition-stable filter 31...Bag body 31a Lower seat 31b Upper seat 32 Filter material 33... Tube 34...Inlet 35...Filling hopper 40 Stone filter layer

Claims

1. A decomposition and stabilization type filter method in which a port facility is installed on a foundation mound, backfill stones and fill soil are placed on the rear side of the port facility, and the fill soil is prevented from being sucked out, The surface of the backfill stone is covered with a decomposition-stable filter having a fail-safe function, The decomposition-stable filter is composed of a bag body in which upper and lower sheets are formed by combining different materials, and a stone filter material is enclosed in the bag body. The bag body has a bottom structure in which a lower sheet made of a soluble or decomposable sheet material and an upper sheet having a sand-proofing function are combined, The decomposition-stabilizing filter is laid in such a manner that the lower sheet is in contact with the surface of the backfill stone, and the upper sheet is in contact with the backfill soil and buried in the backfill. When the lower sheet is broken by the weight of the decomposition-stabilizing filter, the filter material released from the decomposition-stabilizing filter penetrates between the stones on the surface of the backfill stone to form a stone filter layer on the surface of the backfill stone, The stone filter layer and the upper sheet cooperate to exert a sand-proofing function. Decomposition-stabilized filter method.

2. A sand-prevention structure for a port facility in which a port facility is installed on a foundation mound and backfill stones and fill soil are provided on the rear side of the port facility. The surface of the backfill stone is covered with a decomposition-stable filter having a fail-safe function, The decomposition-stable filter is composed of a bag body in which upper and lower sheets are formed by combining different materials, and a stone filter material is enclosed in the bag body. The bag body has a bottom structure in which a lower sheet made of a soluble or decomposable sheet material and an upper sheet having a sand-proofing function are combined, The decomposition-stabilizing filter is laid in such a manner that the lower sheet is in contact with the surface of the backfill stone, and the upper sheet is in contact with the backfill soil and buried in the backfill. The decomposition-stable filter exerts a sand-proofing function by cooperation between the filter material and the upper sheet before the lower sheet is broken. After the lower sheet of the decomposition-stabilized filter is broken, the filter material released by its own weight from the decomposition-stabilized filter penetrates between the stones on the surface of the backing stone, and exerts a sand-proofing function in cooperation with the stone filter layer formed on the surface of the backing stone and the upper sheet. Sand control structures for port facilities.

3. 3. The sand control structure for a port facility according to claim 2, wherein the lower sheet of the decomposition-stable filter is made of a biodegradable sheet.

4. 3. The sand-proofing structure for port facilities according to claim 2, wherein the upper sheet of the decomposition-stable filter is any one of a high-strength multi-layered cloth, a high-strength nonwoven fabric sheet, and a high-strength civil engineering sheet.

5. 3. The sand control structure for a port facility according to claim 2, wherein the overall shape of the decomposition-stable filter is any one of a rod shape, a mat shape, and a cushion shape.

6. 3. The sand control structure for a port facility according to claim 2, wherein the decomposition-stable filters are laid out without gaps on the surface of the backfill stone.

7. 3. The sand control structure for a port facility according to claim 2, wherein the filter material is a mixture of stones of different sizes, the size of which is smaller than that of the backfill stones and smaller than that of the fill soil.

8. 3. The sand control structure for a port facility according to claim 2, wherein the port facility is a newly constructed port facility or an existing port facility.

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