JP6268637B2 - Underwater structure, bottom sediment improvement method, and amamo field construction method - Google Patents

Description

  The present invention relates to an underwater structure for suppressing the outflow of natural or artificial solid matter from a predetermined water area, a bottom quality improving method using the underwater structure, an ammo field creation method, and the like.

  In recent years, mainly in coastal areas, the amount of sediment deposited in the water area has become smaller than the amount of sediment that has flowed out. On the other hand, in order to prevent the outflow of earth and sand due to waves and the like, for example, measures such as installing a wave-dissipating block in the water area are widely adopted.

  In recent years, the deterioration of the water quality environment in relatively shallow water areas and the accompanying deterioration of the surrounding environment have become a problem. For example, when a large amount of eutrophication such as domestic wastewater flows into a specific water area in large quantities, plankton and the like grow and those dead bodies accumulate on the bottom of the water. These accumulated organic substances and the like are decomposed by aerobic microorganisms and the like, but at that time, a large amount of oxygen is consumed, so that the bottom sediment becomes hypoxic. If the sediment is hypoxic, the organisms that inhabit the area will die. Moreover, since anaerobic microorganisms generate odor components such as hydrogen sulfide, not only does the bottom of the water decay, but the water environment is deteriorated, and the surrounding environment is also deteriorated by bad odor. On the other hand, for example, measures are taken to improve the bottom sediment by covering the water area with sand / bottom sediment improving material, or by forming a mound by introducing bottom sediment improving material into the water area. ing.

  Furthermore, in recent years, it has not only prevented coastal erosion and environmental deterioration in the water area and its surroundings, but also restored the environment in relatively shallow water areas, thereby ensuring the growth of animals and plants, fry breeding and biodiversity. It is also required to promote the recovery of fishing grounds. On the other hand, for example, the creation of an Amamo field has been attempted. Amamo is a seed plant that grows in the sea. Traditionally, it grows naturally in the coastal sandy mudland and forms a large community called “Amamo field”. Amamo field is also a place where young fish and small animals grow. However, Amamo fields are decreasing due to land reclamation and revetment work in the coastal areas and water pollution. Therefore, for example, an attempt is being made to restore the environment and secure biodiversity by spreading the eelgrass base material in a specific water area and growing and recovering the eelgrass field in that water area. Yes.

  Including the above items, prevention of coastal erosion, revetment, improvement of water quality / bottom quality, prevention of bad odor, improvement of surrounding environment, environmental restoration, eelgrass development, growth of animals and plants, fry breeding, ensuring biodiversity For various purposes, such as recovery of fishing grounds, natural or artificial solids such as gravel, bottom sediment improving materials, sea eel formation base materials, etc. may be thrown into the bottom of the water or spread. In doing so, in order to achieve these objectives, it is often necessary to keep these natural or artificial solids in a given body of water for a long time.

As a means for holding solids in a predetermined water area for a long period of time, for example, a method of storing solids in a bag and placing it on the bottom of a water (see Patent Document 1, etc.), A method of installing on the bottom of the water (see Patent Document 2, etc.) is disclosed. Patent Document 3 describes seagrass growing means in which artificial seaweed is attached to a base net, and then the base net is laid on a seed mat and fixed to the bottom of the water.
JP 2011-252330 A JP 2012-117280 A JP 2002-119161 A

  As described above, when natural or artificial solids are added to the bottom of the water, the solids need to be held in a predetermined water area for a long period of time. However, in the case of the conventional means for keeping the solid matter in the predetermined water area, a complicated or robust configuration is often adopted, the installation work is complicated, and the installation cost is often high.

  Also, when considering the water quality environment, etc., if the circulation of water around the solid matter is hindered by installing means for holding the solid matter in the predetermined water area, the deterioration of the environment such as hypoxia will be rejected. It tends to happen. Therefore, it is preferable that the flow of water is maintained around the solid matter even after the means for holding the solid matter is installed. However, if the means for holding the solid material is configured in a complicated or robust manner, the water flow is hindered, and the water around the solid material tends to stagnate.

  Therefore, the present invention can be installed easily and at a low cost, for example, when a solid is put into a predetermined water bottom, and the solid is kept for a long time while maintaining the circulation of water around the solid. It aims at providing the solid substance holding means etc. which can be hold | maintained in a water area.

  In the present invention, there is an underwater structure formed on the bottom of the water, and an opening that is surrounded in a substantially rectangular shape by a frame that makes the back surface substantially in surface contact with the bottom of the water, and a number of elongates that stand from the surface of the frame. A structural unit comprising a plurality of rod-shaped parts, and a natural or artificial solid material is leveled in one or a plurality of the openings, and the plurality of rod-shaped members. An underwater structure in which outflow of the solid matter from the opening is suppressed is provided.

  In this underwater structure, for example, the structural units are aligned in a direction substantially parallel to the wave direction and a direction substantially perpendicular to each other, and the whole is formed in a substantially lattice shape. Each structural unit is formed by a frame and an opening surrounded by the frame, and a large number of elongated rod-like portions are erected on the surface of the frame.

  For example, when this underwater structure is installed on a predetermined bottom for the purpose of preventing coastal erosion or revetment, natural solids such as gravel that were originally deposited in the water area are located in each opening of the underwater structure. Is leveled. In addition, prevention of coastal erosion, revetment, improvement of water quality and bottom sediment, prevention of bad odor, improvement of surrounding environment, environmental restoration, eelgrass development, growth of flora and fauna, fry breeding, ensuring biodiversity, fishing grounds For various purposes such as recovery, by introducing or leveling natural or artificial solids such as gravel, bottom sediment improvement material, sea eel formation base material, etc., in the openings, those It is also possible to artificially create a state in which solids are leveled.

  In this underwater structure, a large number of elongated rod-like parts are erected on the surface of the frame, which is a substantially lattice-like frame part. For example, these solids are lifted or moved by external forces such as waves. Even if it does, those solid substances are obstructed by the rod-shaped part from escaping from the inside of the opening. Therefore, the outflow of the solids from the opening can be effectively suppressed, and the solids can be held in the predetermined water area for a long time. For example, even in the case of a solid having a specific gravity of 1.5 to 2.5, which has a specific gravity lower than that of sand and gravel, this configuration can effectively suppress outflow from the opening.

  According to the knowledge obtained by the present inventors, when a fine uneven topographic change occurs in the bottom of the water, the fine change triggers, moves to the shore, spreads throughout, and changes to large erosion. I found out that On the other hand, in the present invention, since the movement and escape of the solid matter is obstructed by the rod-shaped portion, it is possible to suppress the occurrence of minute unevenness in the opening and the spread to the whole. Thereby, since it can prevent that a big terrain change arises in an opening part, a solid substance can be hold | maintained in an opening part for a long period of time.

  Moreover, since each rod-shaped part is erected in a state having a gap, the flow of water around the solid matter in the opening is maintained. Therefore, even after the installation of the underwater structure, it is possible to prevent deterioration of the environment such as hypoxia and decay of the bottom of the water structure.

  Generally, when a structure is formed in water, a vertical vortex is generated near the wall surface, and the base part of the wall surface is swept away, so that the fixed state of the structure itself to the bottom is destabilized. . On the other hand, in this invention, since each rod-shaped part is erected in the state which has a clearance gap and water distribute | circulates the clearance gap, generation | occurrence | production of a vortex etc. can be suppressed. Thereby, since there is little topographic change in the base part of an underwater structure and a fixed state can be maintained stably, long-term installation is possible.

  The underwater structure is formed in a substantially lattice shape as described above, and is installed over a certain area. As a result, for example, even when terrain changes occur in some of the water bottoms in the installation area, the bottom of the water is stable in other areas, and the outflow of solids is suppressed. Do not zoom in. Therefore, the occurrence of sand surface fluctuation at the bottom of the water can be suppressed for a long time, and the topography of the bottom of the water can be stably maintained for a long time.

  Further, according to the knowledge obtained by the present inventors independently, when the underwater structure according to the present invention is installed on the bottom of the water, solid matter is deposited near the entire outer periphery, and a bulge is formed. The region is greatly depressed, and an inclination is formed from the peripheral region toward the underwater structure. As a result, the topography of the entire bottom of the water can be stabilized for a long time around and under the underwater structure, and the fixing means such as the foundation and anchors of the underwater structure can be prevented from being exposed and fixed. The state can be maintained stably. Solid matter in the inner region of the underwater structure is also retained in the opening for a long time.

  This underwater structure has a form that can be transported, and is relatively easy to install and fix to the bottom of the water. Each member can also be manufactured at a relatively low cost. Therefore, simple and low-cost construction is possible.

  For example, after installing this underwater structure on the bottom of the water, the bottom quality improving material is supplied to the predetermined water area easily and at low cost by introducing the bottom quality improving material as a solid into the opening of the underwater structure. In addition, it is possible to hold the bottom sediment improving material in the water area for a long time. Therefore, effective bottom quality improvement is possible.

  In addition, for example, after installing this underwater structure on the bottom of the water, as a solid matter, the base material for the formation of the eelgrass field is spread over the opening, so that the base material for the formation of the eelgrass field is maintained in the water area for a long time. Is possible. In this underwater structure, since a gap is formed between the rod-like portions, when the eel is grown, it can extend into the gap, and growth is not hindered. Therefore, the underwater structure according to the present invention is suitable for the formation of a group of eelgrass fields because it maintains a place necessary for the establishment and growth of eelgrass for a long time and does not inhibit the growth of eelgrass.

  In addition, the present invention can prevent coastal erosion, revetment, improvement of water quality and bottom sediment, prevention of bad odor, improvement of surrounding environment of water area, environmental restoration, eelgrass development, growth of animals and plants, fry breeding, biodiversity Applicable to all cases where natural or artificial solids including gravel are leveled to the bottom of the water for various purposes such as securing and recovery of fishing grounds.

  According to the present invention, a natural or artificial solid substance containing gravel can be kept in a predetermined water area for a long period of time at a simple and low cost, and the water around the solid substance can be maintained even after installation. Can be maintained.

<About the underwater structure according to the present invention>
The present invention is an underwater structure formed on the bottom of the water, and has an opening that is surrounded in a substantially rectangular shape by a frame whose back surface is substantially in surface contact with the bottom of the water, and a plurality of elongate members standing from the surface of the frame. A structural unit comprising a plurality of rod-shaped parts, and a natural or artificial solid material is leveled in one or a plurality of the openings, and the plurality of rod-shaped members. All the underwater structures in which the outflow of the solid matter from the opening is suppressed are included. Hereinafter, description will be made with reference to FIGS. 1 and 2. Note that the present invention is not limited to these embodiments.

  FIG. 1 is a schematic plan view showing an example in which an underwater structure according to the present invention is installed on the bottom of a water. FIG. 2 is a schematic partial perspective view of the underwater structure according to the present invention, and is a partial view centering on one constituent unit of the underwater structure.

  The underwater structure A in FIG. 1 is formed by vertically and horizontally aligning units formed by two structural units B and B on the water bottom W in the vicinity of the coastal area S, and is substantially parallel to the wave direction X1. A total of 24 structural units B are formed, three in the direction of 8 and 8 in the substantially vertical direction.

  The structural unit B in the underwater structure A in FIG. 2 has a large number of erected from the opening 2 surrounded by a frame 1 that makes the back surface 11 substantially in surface contact with the water bottom W and the surface 12 of the frame 1. An elongated rod-like portion 3.

  The underwater structure A has a configuration in which the structural units B are arranged in a substantially lattice shape, and is formed on the water bottom W as a whole. The underwater structure A only needs to be formed in a substantially lattice shape as a whole. For example, all the structural units B are continuously formed as one member, or a plurality of structural units B are continuously connected to form a unit. It includes everything formed and formed by aligning a plurality of units, and those formed by aligning independent structural units B.

  The underwater structure A has, for example, a configuration in which the structural unit B is aligned in a direction substantially parallel to the wave direction X1, 2 or more, 3 or more in a substantially vertical direction, a total of 6 or more, and more preferably, A configuration in which 3 or more in a direction substantially parallel to the wave direction X1 and 3 or more in a substantially vertical direction, or a total of 9 or more, may be arranged. The upper limit varies depending on the installation area and the like, and is not particularly limited. However, the upper limit is preferably 100 or less in each of the direction substantially parallel to the wave direction X1 and the direction substantially perpendicular to the wave direction X1.

  The underwater structure A is installed over a certain region by aligning the structural units B in a substantially lattice shape in a direction substantially parallel to the wave direction X1 and a direction substantially perpendicular to the wave direction X1. As a result, for example, even when terrain changes occur in some of the water bottoms in the installation area, the bottom of the water is stable in other areas, and the outflow of solids is suppressed. Do not zoom in. Therefore, the occurrence of sand surface fluctuation at the bottom of the water can be suppressed for a long time, and the topography of the bottom of the water can be stably maintained for a long time.

  In addition, in the structural units B1 to B2 to B3 to B4 located on the outer periphery of the underwater structure A, external forces such as waves are directly loaded (reference numerals X2 and X3), and therefore each structural unit B1 to B2 to B3 in the region. ~ B4 may cause some terrain fluctuation, but the external force does not reach the structural units B5 to B6 and B7 to B8 located in the inner area sufficiently (reference numerals X4 and X5), and the structural unit B5 In ~ B6 and B7-B8, the landform change hardly occurs. Therefore, by forming the underwater structure A by aligning a plurality of structural units B, the bottom terrain can be more stably stabilized for a long time in the structural units B5 to B6 and B7 to B8 located in the inner region. Can be maintained.

  The installation location of the underwater structure A is not particularly limited as long as it is a relatively shallow water area and can be appropriately determined according to the purpose. For example, it can be installed in seas, lakes, rivers, etc. in coastal areas.

  The installation / fixing means for the underwater structure A can be widely used and is not particularly limited. For example, it may be performed by hitting an anchor / pin member or the like, or the underwater structure A may be locked to a sandbag and submerged in the bottom of the water to be fixed. Further, for example, an asphalt mat or the like may be adopted for the frame body 1, the rod-shaped portion 3 may be formed on the surface 11, and the underwater structure A may be sunk and fixed in alignment with the bottom of the water.

  The frame 1 is a member that is a base of the underwater structure A, and is a skeleton part when formed in a substantially lattice shape. An opening 2 is formed in the frame. The back surface 11 of the frame 1 is a portion that is substantially in surface contact with the water bottom W, and a large number of rod-like portions 3 are erected from the surface 12.

  For example, when all the structural units B are continuously formed as one member, the frame 1 is formed in a substantially lattice shape, and when the plurality of structural units B are continuously formed, the frame 1 is opened. When the part 2 is formed as a substantially rectangular flat plate formed by the number of the structural units B, and one structural unit B is formed as an independent member, as a substantially rectangular flat plate formed with one opening 2 It is formed. Each crosspiece 13 forming the frame 1 may be a constituent element of one constituent unit B, or may be a common constituent element of two adjacent constituent units B and B.

  The material of the frame 1 can widely adopt a known flat plate material, and is not particularly limited. For example, a flat plate-like flexible member such as an asphalt mat can be suitably used. By adopting a flat plate-like flexible member such as asphalt mat as the material of the frame body 1, for example, a part of the bottom W is eroded by waves or the like, and the terrain in the installation area of the underwater structure A or its surroundings Even when the change occurs, the frame 1 can be bent in accordance with the terrain change, so that the frame 1 and the water bottom W can be maintained in a substantially intimate contact state between the frame 1 and the water bottom W. It is possible to minimize the formation of gaps. As a result, the spread of the topographic change at the bottom of the water W can be effectively suppressed, and the solid matter leveled in the opening 2 can be reliably retained for a long period of time. In many cases, a material that does not deteriorate even when installed in water for a long period of time is more preferable.

  The width of each crosspiece 13 forming the frame 1 is designed in consideration of the size of the opening 2 and the number and density of the rod-like portions 3 to be erected. If the width of the frame 1 is large, the portion covering the bottom W will be large, and if it is small, it will be difficult to stand a large number of rod-shaped portions 3 at appropriate intervals. For example, about 15 mm to 150 mm is preferable.

  The opening 2 is a portion where the water bottom W is exposed when the underwater structure A is installed in water, and is a portion surrounded by a frame 1 in a substantially rectangular shape.

  When the underwater structure A is installed on the bottom W, natural or artificial solids are leveled in at least one or a plurality of openings 2. That is, for example, when an underwater structure A is installed on a predetermined bottom W for the purpose of preventing coastal erosion, revetment, etc., gravel originally deposited in the water area W in each opening 2 of the underwater structure A Natural solids such as are leveled. In addition, for example, prevention of coastal erosion, revetment, improvement of water quality and bottom sediment, prevention of bad odor, improvement of surrounding environment, environmental restoration, eelgrass development, growth of animals and plants, securing biodiversity, recovery of fishing grounds When the underwater structure A is installed on the predetermined bottom W for the purpose of the above, natural or artificial solids such as gravel, bottom sediment improvement material, eelgrass base material, etc. are thrown in and spread out. ing.

  Since the bottom 2 is exposed in the opening 2, natural or artificial solids are scooped up or moved by an external force such as a wave. Even if it occurs, it is limited to the structural units B1 to B2 to B3 to B4 located on the outer periphery of the underwater structure A, and hardly occurs in the structural units B5 to B6 located in the inner region.

  The dimension of the opening 2, that is, the opening width d 1 of the frame 1 can be appropriately set depending on the purpose and application, and is not particularly limited. For example, if the opening width of the frame 1 is too large, the topographical fluctuation of the bottom W is likely to occur due to external forces such as waves. If it is too small, the work efficiency is lowered, and the exposed area of the bottom W becomes small. Cannot be achieved. For example, the opening width d1 of the frame 1 is preferably 200 to 1,000 mm.

  The rod-shaped portion 3 is a long and narrow portion formed in a rod shape or a needle shape. A large number are erected from the surface 12 of the frame 1 and are formed in a substantially comb shape. By forming the rod-shaped part 3, the outflow of the solid substance from the inside of the opening part 2 can be effectively suppressed.

  The rod-shaped portions 3 are formed at a predetermined interval, and a predetermined gap is formed between the rod-shaped portions 3. Since the gap is formed between the rod-shaped portions 3, the flow of water around the solid matter existing in the underwater structure A and the opening 2 is maintained. It is possible to suppress hypoxia and decay of the bottom of the water, and promote the growth of organisms. Moreover, since generation | occurrence | production of the vortex in the outer periphery of the underwater structure A etc. can be suppressed, the topographic change in the vicinity part of the frame 1 located in the outer periphery of the underwater structure A can be decreased. In addition, for example, when the present invention is applied to the eelgrass field construction, when the eelgrass grows, it can extend into the gaps, and the growth of the eelgrass is not hindered.

  The interval between the rod-like portions 3 is not particularly limited. For example, in the case where a solid substance having a particle size larger than that of sand or the like is present in the opening 2, by setting the solid particle size to be substantially the same (for example, the median particle size ± 10 mm), The loss from the gap between the rod-like parts 3 of the object can be suppressed. However, if the interval between the rod-shaped parts 3 is too narrow, the flow of water is hindered and it is disadvantageous for the growth of sea cucumbers.

  The arrangement of the rod-shaped portions 3 is not particularly limited. For example, it is more preferable to arrange a plurality of rows and arrange them so as to alternate with adjacent rows, rather than arranging them in a row in the longitudinal direction. Since the loss of the solid matter can be effectively suppressed, it is more preferable.

  The shape of the rod-shaped part 3 is not particularly limited as long as it is formed in an elongated shape. For example, a substantially cylindrical shape, a substantially cubic shape, a substantially cone shape, a substantially needle shape, a substantially polygonal shape, or the like can be appropriately employed.

  The length d2 of the rod-like portion 3 can also be set as appropriate and is not particularly limited. For example, the rod-shaped portion 3 having a length d2 of 100 to 500 mm can be suitably used.

  The solid matter leveled in the opening 2 includes natural solids such as gravel originally deposited in the water area where the underwater structure A is installed, gravel gravel that is thrown into or spread in the water area, bottom sediment improvement material, A wide range of solids leveled to the bottom of the water, such as natural or artificial solids including a shellfish base material, is not particularly limited. For example, it includes a wide range of sand, granular, pellet, substantially spherical, and those molded into a predetermined shape.

  The present invention can be applied not only to gravel and the like having a relatively high specific gravity but also to a solid having a specific gravity in the range of 1.5 to 2.5. When solids having a specific gravity in this range are present in the opening 2, these solids may be lifted up by an external force such as a wave, but the rod-like part 3 prevents escape of these solids. The

  Coal ash granulated material has a bottom sediment improvement function and is also suitable as a base material for eelgrass field construction. Therefore, it is suitable for this invention that a solid substance is a coal ash granulated material.

  Coal ash granulated material is made into a size of about 10 mm in diameter by adding about 90% coal ash, about 10% cement, and about 3% clay such as bentonite, and mixing with a continuous mixer. It is a grain.

  Coal ash granulates are known to have excellent nitrogen and phosphorus adsorption capacity and water / bottom sediment purification properties. As a substitute for water sand, coal ash granulates can be used to cover sand and mound. It is known that the bottom quality can be improved by doing so. Accordingly, the underwater structure A according to the present invention is installed at the bottom of the water, and the coal ash granule is held in a predetermined water area for a long time by spreading the coal ash granule as a solid in the opening 2 thereof. In addition, since it is possible to maintain the circulation of water around the coal ash granulated material, it is possible to effectively improve the bottom sediment.

  Moreover, as above-mentioned, a coal ash granule is suitable also for the base material for an ammo ground. For example, the underwater structure A according to the present invention is installed on the bottom of the water, and the coal ash granulated material is spread and solidified in the opening 2 so that sea eels are seeded and planted there and grown. By installing the underwater structure A on the bottom of the water, the coal ash granule can be kept in a predetermined water area for a long time and the circulation of water around the coal ash granule can be maintained. Can be grown. Moreover, in this underwater structure A, since the clearance gap is formed between the rod-shaped parts 3, the growth of a eel is not inhibited. In addition, eelgrass has the property of absorbing nitrogen and phosphorus, so it is possible to purify the water quality of the water area by creating an eelgrass field.

<About the sediment improvement method according to the present invention>
The present invention includes all bottom sediment improvement methods including the step of installing the above-mentioned underwater structure on the bottom of the water and the step of introducing the bottom sediment improvement material into the opening as the solid matter.

  As described above, the underwater structure according to the present invention is capable of maintaining a solid in a predetermined water area for a long period of time and maintaining the circulation of water around the solid present in the opening of the underwater structure. Have. Therefore, for example, by installing the underwater structure on the bottom of the water and introducing the bottom quality improving material as a solid into the opening of the underwater structure, the bottom quality can be effectively improved.

  A well-known thing can be widely employ | adopted for bottom material improvement material, It does not specifically limit. For example, you may apply said coal ash granulated material.

<About the Amamo field construction method according to the present invention>
The present invention includes all the ammo field creation methods including the step of installing the above-described underwater structure on the bottom of the water and the step of spreading an ammo field creation base material on the opening as the solid matter.

  As described above, the underwater structure according to the present invention is capable of maintaining a solid in a predetermined water area for a long period of time and maintaining the circulation of water around the solid present in the opening of the underwater structure. Have. Therefore, for example, an underwater structure is installed at the bottom of the water, and an ammo field creation base material is spread as a solid in an opening of the underwater structure, and an ammo field is planted there, thereby creating an ammo field. it can.

  A well-known thing can be widely employ | adopted as a base material for Amamo field construction, and it does not specifically limit. For example, you may apply said coal ash granulated material.

  In Example 1, a hydraulic model experiment with a geometric scale of 1/10 was performed.

  Solid matter was spread on the bottom of a two-dimensional water channel (width 0.2 m, length 8.0 m, height 0.3 m). The solid material was used after adjusting the particle size of granulated coal ash. The median particle size of the solid was 1.1 mm, there were many voids, and the apparent specific gravity was about 1.8.

  As a member for preventing erosion, rod-shaped portions having a diameter of 0.5 mm and a height of 15 mm were erected on the plate at intervals of 2 mm in length and width so as to be alternated with adjacent rows in 5 rows in the longitudinal direction.

  In the two-dimensional water channel, these two members for preventing erosion were installed perpendicular to the wave direction. The distance between them was 79 mm.

  Waves were applied under conditions of wave formation time of 47 minutes, wave period of 1.90 seconds, and wave height of 20 mm, and the erosion depth (mm) in and around the water area where the plate was installed was measured.

  As a result of installing erosion prevention members perpendicular to the wave direction at intervals of 79 mm, accumulation of 2 mm was observed in the vicinity of both erosion prevention members, and erosion was observed in the area sandwiched between both erosion prevention members. I couldn't. Moreover, the formation of vortices around both members was not observed.

  Since this is an experiment with a geometric scale of 1/10, this result shows that by installing a member with a large number of rod-shaped parts standing on the bottom at an interval of about 800 mm, erosion of the bottom in the area sandwiched between them can be prevented. Indicates.

  The present invention is configured to include an opening surrounded by a frame body in a substantially rectangular shape and a large number of elongated rod-like portions standing from the surface of the frame body, and the opening width of the frame body is 200 to 1,000 mm. . Therefore, the result of the present example suggests that the configuration according to the present invention can effectively prevent erosion of the water bottom due to the topographic change in the opening.

  In Example 2, an on-site application test was performed.

  An approximately rectangular frame having a large number of elongate rod-like portions standing on the surface was prototyped. The dimensions of the frame were 600 mm × 600 mm, and the length of the rod-shaped part was 150 mm. The rod-shaped portions were arranged in three rows in the longitudinal direction so that adjacent rows were staggered, the distance between adjacent rod-shaped portions in the same row was 30 mm, and the distance between adjacent rod-shaped portions was about 8 to 16 mm. .

  Part of the coastal area was divided into 1,200 mm × 1,200 mm in size with sandbags, and coal ash granules (center particle diameter 11 mm, specific gravity 2.2) were placed about 300 mm high in it. Two frames were placed side by side in the direction of the wave in half of the area, and anchors were driven to a depth of about 150 mm and fixed. The remaining half of the area was used as a control area without a frame. The erosion status was measured for about 5 months with the test area exposed to natural waves.

  As a result, in the area where the frame with the rod-shaped part installed was installed, there was less erosion compared to the initial installation, whereas on the side where the frame was not installed, the coal ash granulation was It was significantly eroded.

  In addition, out of the area where the frame with the rod-shaped part is installed, the frame installed on the shore side has less erosion than the frame installed on the shore, and about 5 months have passed. Even after that, the coal ash granulation in the frame was kept almost unchanged.

  This result shows that by using the underwater structure according to the present invention, it is possible to hold the solid matter spread in the water area for a long time, and the structural unit of the underwater structure By aligning two or more, it is possible to suppress the topographic change of the bottom of the water in the inner area.

  For example, when installing a wave-dissipating block in the coastal area for the purpose of coastal erosion prevention and revetment, the installation work is large and the cost is great. On the other hand, when installing the underwater structure according to the present invention at the bottom of the water, it is possible to construct it easily and at low cost, and because the gravel at the bottom of the water can be held in the water area for a long time, It is possible to effectively prevent sediment discharge.

  For example, when putting natural or artificial solids into the bottom of the water, in order to keep the solids in a predetermined water area for a long period of time, they are packed in gabion / bags and placed on the bottom of the water In this case, since the water flow around the solid matter cannot be sufficiently secured, the water quality environment is likely to be deteriorated, and the growth and reproduction of the organism are hindered. In addition, since the water flow collides with the wall surfaces of these containers to form vortices, the gravel on the base portion is easily eroded and the topography of the bottom of the water is likely to change. On the other hand, in this invention, since each rod-shaped part is standingly arranged in the state which has a clearance gap, the distribution | circulation of water is maintained. Therefore, even after this underwater structure is installed, deterioration of the water quality environment and the like can be suppressed, and generation of vortices on the outer periphery of the underwater structure A can be suppressed.

  For example, when a solid material or the like is attached to a mat-like base material and placed on the bottom of the water, the bottom of the water is covered with a base, so that the dissolved oxygen in water cannot be smoothly taken into the sand surface of the bottom of the water. Since it tends to cause deterioration of the water quality environment such as oxygenation and decay of the bottom of the water, the growth of organisms such as sea bream may be hindered. On the other hand, in the present invention, the bottom surface of the water is exposed by being formed in a substantially lattice shape, and the flow of water is also maintained by standing each rod-like portion in a state having a gap. . Therefore, according to the present invention, it is possible to create a water bottom environment that is favorable for the growth of organisms such as sea lions.

The plane schematic diagram which shows the example at the time of installing the underwater structure which concerns on this invention in the water bottom. The partial appearance perspective schematic diagram of the underwater structure concerning the present invention.

DESCRIPTION OF SYMBOLS 1 Frame 2 Opening part 3 Rod-shaped part A Underwater structure B Structural unit S Coastal area W Water bottom

Claims (7)

An underwater structure formed on the bottom of the water,
A configuration comprising: an opening surrounded in a substantially rectangular shape by a frame made of a flat plate-like flexible member whose surface is substantially in surface contact with the water bottom; and a plurality of elongated rod-like portions standing from the surface of the frame. It is a configuration in which the units are arranged in a substantially grid pattern,
An underwater structure in which molded solid matter is leveled in one or a plurality of the opening portions, and outflow of the solid matter from inside the opening portions is suppressed by the plurality of rod-shaped members.   2. The underwater structure according to claim 1, wherein the structural units are arranged in a total of 6 or more, 2 or more in a direction substantially parallel to the wave direction and 3 or more in a substantially vertical direction.   3. The underwater structure according to claim 1, wherein an opening width of the frame body is 200 to 1,000 mm, and a length of the rod-shaped portion is 100 to 500 mm.   The underwater structure according to any one of claims 1 to 3, wherein the solid has a specific gravity of 1.5 to 2.5.   The underwater structure according to any one of claims 1 to 4, wherein the solid matter is a coal ash granulated product. Installing the underwater structure according to any one of claims 1 to 5 on the bottom of the water;
Adding a bottom material improving material as the solid matter into the opening. Installing the underwater structure according to any one of claims 1 to 5 on the bottom of the water;
A process for creating an eelgrass field, comprising the step of spreading, as the solid matter, a base material for larva field formation on the opening.

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