Artificial shallow area

Abstract

To provide an artificial shallow area more suitable for the growth of seagrass and / or seaweed. [Solution] An artificial shallow area according to one aspect of the present invention is an artificial shallow area located underwater, comprising a first submerged breakwater having at least a surface of stone arranged on it, and a substantially horizontal first construction surface connected to the first submerged breakwater, wherein the surface layer of the first construction surface consists of one or more base materials selected from the group consisting of solidified soil, sand, gravel, and stone.

Description

Technical Field

[0001] The present invention relates to an artificial shallows located in water such as the sea.

Background Art

[0002] From the perspective of consideration for the natural environment, in recent years, in the sea area, construction of artificial tidal flats and shallows has been carried out.

[0003] For example, in Non-Patent Document 1, as an example of an artificial tidal flat, a biotic symbiosis type revetment "Shioiro no Nagisa" is described. "Shioiro no Nagisa" has a stepped tidal flat part where the upper stage is L.W.L + 1.00 m, the middle stage is L.W.L + 0.50 m, and the lower stage is L.W.L. And the upper, middle, and lower stages of this tidal flat part are all constructed as substantially horizontal planes, similar to natural tidal flats.

[0004] Also, regarding the construction of an artificial shallows, after installing a submerged breakwater in the offing, a filling material is put into the sea area from the submerged breakwater toward the shore, and further, sand is covered on the upper part of the layer of the filling material (referred to as "conventional shallows construction method"). This method is generally used. According to this method, a shallows having a gradient that becomes deeper toward the offing, similar to a natural shallows, is constructed.

[0005] That is, from the perspective of the gradient of the construction surface, the "Shioiro no Nagisa" described in Non-Patent Document 1 and the "conventional shallows construction method" have structures imitating natural tidal flats and shallows, respectively.

[0006] On the other hand, in Patent Document 1, a method for constructing a multi-purpose artificial reef, etc., is described, in which after constructing a wave-dissipating structure by laying wave-dissipating blocks on a mound constructed on the seabed, industrial waste is discarded in the sea area behind it to form a deposited layer of industrial waste.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

[0008] [Non-Patent Document 1] Construction Machinery Construction Vol.73, No.10, October 2021 [Overview of the project] [Problems that the invention aims to solve]

[0009] Incidentally, seagrasses and seaweeds that inhabit shallow waters have a suitable water depth for their growth, depending on the species. However, artificial shallow waters created by the "conventional shallow water creation method" described above have a gradient that becomes deeper as you move offshore, just like natural shallow waters. Therefore, for example, 1) if the gradient is steep, it is difficult to secure a large area of ​​shallow water where seagrasses and / or seaweeds can grow, or 2) it is difficult to secure a large area of ​​shallow water suitable for a particular type of seagrass or seaweed.

[0010] On the other hand, the multipurpose artificial reef described in Patent Document 1 has a substantially horizontally drawn construction surface (covering layer 9), as shown in Figure 1, for example. The covering layer 9 is formed by depositing an improvement material containing coal ash in order to function as a cover to prevent the scattering of various industrial wastes. Here, the viscous improvement material containing coal ash is obtained by adding a water-hardening solidifying agent (such as cement) and water to coal ash, and optionally adding construction-generated soil (paragraphs 0009 to 0010 of Patent Document 1). Consequently, the construction surface (covering layer 9) of the multipurpose artificial reef described in Patent Document 1 has problems such as difficulty for seaweed roots to penetrate, and at the same time, due to its strength, even if seaweed attaches, it easily peels off, making it difficult to form and maintain a stable ecosystem.

[0011] One aspect of the present invention has been made in view of the above-mentioned problems, and its object is to provide an artificial shallow area more suitable for the growth of seagrass and / or seaweed. [Means for solving the problem]

[0012] To solve the above problems, an artificial shallow area according to one aspect of the present invention is an artificial shallow area located underwater, comprising a first submerged breakwater having at least a surface of stone arranged on it, and a substantially horizontal first construction surface connected to the first submerged breakwater, wherein the surface layer of the first construction surface consists of one or more base materials selected from the group consisting of solidified soil, sand, gravel, and stone. [Effects of the Invention]

[0013] According to one aspect of the present invention, it is possible to provide an artificial shallow area more suitable for the growth of seagrass and / or seaweed. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a schematic diagram showing the structure of an artificial shallow area according to one aspect of the present invention, in comparison with the structure of a conventional artificial shallow area. [Figure 2] Figure 2 illustrates variations in the distribution of seagrasses and seaweed in an artificial shallow area structure according to one embodiment of the present invention. [Figure 3] Figure 3 shows the main parts of an artificial shallow-water structure according to another embodiment of the present invention. [Modes for carrying out the invention]

[0015] One embodiment of the present invention will be described in detail below with reference to the drawings.

[0016] [Embodiment 1] (overview) An artificial shallow area 20 according to one embodiment of the present invention, as shown in Figure 1(A), includes a submerged breakwater (first submerged breakwater) 21 and a substantially horizontal construction surface (first construction surface) 23 connected to the submerged breakwater 21. The artificial shallow area 20 is provided in the sea 111 (underwater). In the figure, the left side corresponds to the offshore side and the right side corresponds to the shore side, and the artificial shallow area 20 is formed on the shore side of the submerged breakwater 21.

[0017] (Structure of the submerged breakwater) The submerged breakwater 21 is constructed on the seabed 110. The submerged breakwater 21 may be entirely composed of stone materials, but it is sufficient as long as at least the surface is provided with stone materials. The stone materials arranged on the surface of the submerged breakwater 21 serve as an attachment base for seaweeds. The top width of the submerged breakwater 21 is not particularly limited. For example, it is 0.5 meters or more, or 1 meter or more. The upper limit of the top width of the submerged breakwater 21 is also not particularly limited. For example, it is 20 meters or less, or 5 meters or less. The length (submerged breakwater length) of the submerged breakwater 21 is not particularly limited. For example, it is within the range of 5 meters or more and 1000 meters or less. On the submerged breakwater 21, wave dissipating blocks may or may not be installed. If a more calm situation from waves is required, they may be installed. Note that the wave dissipating blocks can also serve as an attachment base for seaweeds.

[0018] (Structure of the reclaimed surface) The reclaimed surface 23 is a surface reclaimed in the area on the shore side of the submerged breakwater 21 among the areas partitioned by the submerged breakwater 21 and the seabed 110. It is composed of a backfill material layer 22 provided on the seabed 110 located on the shore side of the submerged breakwater 21 and a surface layer arranged on the backfill material layer 22. The backfill material layer 22 is configured to be thick on the offshore side (the side close to the submerged breakwater 21) and thin towards the shore side so that its upper surface is substantially horizontal. The surface layer of the reclaimed surface 23 arranged on the backfill material layer 22 is a substantially horizontal surface and is composed of one or more base materials selected from the group consisting of solidified treated soil, sand, gravel, and stone. These base materials enable the growth of seagrass and / or seaweeds. For example, sand and gravel serve as a growth base for seagrass (e.g., eelgrass, core eelgrass, etc.), and solidified treated soil, gravel, and stone serve as an attachment base for seaweeds (e.g., wakame, kombu, arame, kajime, hondawara, etc.). Note that as will be described later using FIG. 2, these base materials may be used alone or multiple types may be used on the same surface layer. For example, for the same surface layer of the reclaimed surface, the base material for seagrass may be arranged in the area where seagrass is desired to grow, and the base material for seaweeds may be arranged in the area where seaweeds are desired to grow.

[0019] Regarding the filling surface 23, the distance from the submerged dike 21 to the shore side is not particularly limited. For example, it is 1 meter or more, or 5 meters or more. The upper limit of the distance from the submerged dike 21 to the shore side is also not particularly limited. For example, it is 100 meters or less, or 300 meters or less.

[0020] Typically, the surface layer of the filling surface 23 is located below the low tide line. The water depth to the surface layer of the filling surface 23 is not particularly limited as long as seaweed and / or seaweed can grow. For example, it is up to 25 m based on the low tide line, preferably up to 20 m. The water depth to the surface layer of the filling surface 23 may be, for example, up to 15 m, 10 m, 5 m, or 2.5 m based on the low tide line. Although not particularly limited, when aiming to form a seaweed bed where at least seaweed grows, the water depth to the surface layer of the filling surface 23 may be preferably up to 10 m, 5 m, 2.5 m, or 0.5 m based on the low tide line. Note that the water depth to the surface layer of the filling surface may be appropriately designed according to the type of seaweed and / or seaweed targeted and the water transparency so that seaweed and / or seaweed can grow.

[0021] The surface layer of the filling surface 23 is substantially horizontal as described above. Substantially horizontal means that it may have an inclination with respect to the horizontal plane within a range that exhibits the same effect as the horizontal plane (for example, the advantages exemplified below). In a specific example, substantially horizontal includes, in addition to the horizontal plane, those with an inclination of 1 / 10 or less (preferably 1 / 50 or less, more preferably 1 / 100 or less) with respect to the horizontal plane within its scope.

[0022] (Examples of advantages compared with conventional configurations) The artificial shallows 200 shown in (C) of FIG. 1 includes a submerged dike 210 and a filling surface 230 connected to the submerged dike. The filling surface 230 is composed of a backfill layer 220 provided on the seabed 110 and a surface layer disposed on the backfill layer 220. Since the backfill layer 220 is substantially parallel to the seabed 110, the surface layer of the filling surface 230 has the same inclination (tilt with respect to the horizontal) as the seabed 110. Compared with the artificial shallows 200, the artificial shallows 20 has, for example, the advantages exemplified below.

[0023] (1) Each type of seagrass and seaweed has a suitable water depth for growth, and growth becomes difficult or impossible beyond a certain depth. Also, if the water is too shallow, growth becomes difficult or impossible due to factors such as drought at low tide. Since the artificial shallow area 20 has a roughly horizontal construction surface, by appropriately designing the water depth of the construction surface, a wider area for seagrass and / or seaweed growth can be secured compared to the artificial shallow area 200. This is a particularly significant advantage in urban areas with relatively low water clarity.

[0024] (2) In addition to the above water depth classifications, each type of seaweed has a suitable surface strength for attachment, and some cannot attach unless the strength is above a certain level. Furthermore, since different types of seaweed may prefer different substrates for attachment to the surface, such as some preferring rock and others preferring sand, the surface strength and type of substrate can be classified and constructed on the approximately horizontal surface of the artificial shallow area 20 to be suitable for the growth of seagrass and seaweed, thereby providing a more suitable growing environment for seagrass and seaweed.

[0025] (3) Since the artificial shallow area 20 has a nearly horizontal construction surface, the base material placed on the surface of the construction surface is less likely to be lost compared to the artificial shallow area 200, which has a sloping surface. This effect is particularly pronounced when the base material is relatively lightweight (sand, gravel, and in some cases, solidified soil). On the other hand, in the case of the artificial shallow area 200, which has a slope, erosion by natural waves and wake waves is more likely to occur, and in particular the sand and gravel that are the base for seagrass growth may be lost, making it difficult for seagrass or seaweed beds to form.

[0026] When solidified soil is used as a base material, the leaching of iron from the slag has a positive effect on growth. When artificial stone mixed with seaweed or compost is used as a base material, nitrogen, phosphorus, etc. leach out, promoting the growth of seagrass and seaweed.

[0027] (A configuration consisting of multiple nearly horizontal leveled surfaces) An artificial shallow area 50 according to one embodiment of the present invention, as shown in Figure 1(B), has a structure comprising two substantially horizontal construction surfaces 33 and 43 (the first and second construction surfaces, respectively), and these construction surfaces 33 and 43 are located at different water depths, forming a two-tiered shallow area 50. More specifically, the construction surface 33 located on the offshore side is designed to be deeper, and the construction surface 43 located on the shore side is designed to be shallower. Furthermore, the construction surface 33 is provided in connection with a submerged breakwater (first submerged breakwater) 31, and the construction surface 43 is provided in connection with a submerged breakwater (second submerged breakwater) 41.

[0028] The construction surface 33 and the submerged breakwater 31 are structures corresponding to the construction surface 23 and the submerged breakwater 21 shown in Figure 1(A), respectively. The construction surface 33 consists of a backfill material layer 32 provided on the seabed 110 located closer to the shore than the submerged breakwater 31, and a surface layer placed on top of the backfill material layer 32. The submerged breakwater 41 is provided on the backfill material layer 32 that constitutes the construction surface 33, and, like the submerged breakwater 31, has stone material placed on at least its surface. The construction surface 43 consists of a backfill material layer 32 located closer to the shore than the submerged breakwater 41, a backfill material layer 42 provided on the seabed 110, and a surface layer placed on top of the backfill material layer 42. The backfill material layer 42 is constructed so that its upper surface is approximately horizontal, with a roughly uniform thickness on the offshore side (the part closer to the submerged breakwater 41 where the backfill material layer 32 is based), and becomes thinner towards the shore (the part above the seabed 110). The surface layer of the construction surface 43, like the surface layer of the construction surface 33, consists of one or more base materials selected from the group consisting of solidified soil, sand, gravel, and stone.

[0029] In Figure 1(B), the structure of the shallow area 50 is illustrated as having two layers of approximately horizontal reclaimed surfaces located at different water depths. However, the shallow area can also have N layers (where N is an integer of 2 or more) of approximately horizontal reclaimed surfaces located at different water depths. Here, N is preferably in the range of 2 to 5, and may be preferably in the range of 2 to 4, or in the range of 2 to 3. When the submerged breakwater located furthest offshore is designated as the first submerged breakwater, the substantially horizontal construction surface connected to the first submerged breakwater is designated as the first layer, the submerged breakwater located furthest shore is designated as the Nth submerged breakwater, and the substantially horizontal construction surface connected to the Nth submerged breakwater is designated as the Nth layer, the Nth submerged breakwater is constructed on the construction surface of the (N-1) layer. In one example of construction, the work is carried out in the following order: the first submerged breakwater, the construction surface of the first layer (with the surface layer formed after the infill layer), the second submerged breakwater, the construction surface of the second layer, ..., the Nth submerged breakwater, and the construction surface of the Nth layer.

[0030] Furthermore, even if there are N layers of roughly horizontal construction surfaces, the water depth and size of the construction surfaces can be designed in the same way as, for example, as explained in Figure 1(A). In addition, it is desirable to determine the number of N layers by considering the types of seagrasses and seaweed growing in the sea area where the artificial shallow area 50 is to be created and the water depth of the area to be created.

[0031] The artificial shallow area 50 has the same advantages as the artificial shallow area 20 (Figure 1(A)) when compared to the conventional artificial shallow area 200 (Figure 1(C)). Furthermore, the artificial shallow area 50 has the advantages exemplified below when compared to the artificial shallow area 20.

[0032] (1) Because it has multiple nearly horizontal construction surfaces with different water depths, it is easy to provide an environment suitable for the growth of a wider variety of seagrasses and / or seaweed.

[0033] (2) The size of each individual breakwater can be reduced.

[0034] (3) By adopting a multi-tiered structure, it is possible to reduce the invasion and predation damage caused by sea urchins and other marine life. In one specific example, in an artificial shallow area, a seaweed bed is formed in which the distribution of seaweed species that serve as food for sea urchins and other marine life is discontinuous from the offshore side to the shore side. For example, if seaweed is expected to attach to the submerged breakwater located furthest offshore (first submerged breakwater: submerged breakwater 31), the approximately horizontal construction surface (first layer: construction surface 33) attached to this submerged breakwater is designed in such a way that seaweed is less likely to attach near the submerged breakwater. With such a design, even if the seaweed attached to submerged breakwater 31 serves as food for sea urchins and other marine life, the invasion of sea urchins and other marine life can be limited to submerged breakwater 31, preventing them from encroaching further towards the shore. Designs that make it difficult for seaweed to attach to the vicinity of the submerged breakwater include, for example, 1) covering the vicinity of the submerged breakwater with sand to form the surface layer on a nearly horizontal construction surface (first layer), or 2) leaving the infill material layer exposed to form the surface layer, but are not limited to these.

[0035] (Examples of seagrasses and seaweed that form seaweed beds) The types of seagrasses that grow in artificial shallow areas of 20-50 meters are not particularly limited, and the types that grow there are those that are appropriate to the sea area in which the shallow area is created. Seagrasses that belong to the families Zosteraceae, Posidoniaceae, Cymodoceaceae, Hydrocharitaceae, Zannichelliaceae, and Ruppiaceae are known, but among these, the plants belonging to the genus Zostera of the family Zosteraceae, such as Zostera marina, Zostera japonica, Zostera marina, Zostera maximowiczii, and Zostera marina, are representative. Zostera japonica prefers shallower water depths compared to Zostera marina.

[0036] The types of seaweed that grow in artificial shallow areas of 20-50 are not particularly limited, and the types that grow are those appropriate to the sea area where the shallow area is created. Seaweed is classified into brown algae, red algae, and green algae, but brown algae are preferred. Examples of brown algae include kelp species belonging to the genus Saccharina in the family Laminariaceae, such as Laminaria japonica, Laminaria tetrandra, Laminaria japonica, Laminaria mellea, and Laminaria japonica; wakame species belonging to the genus Undaria in the family Lamiaceae, such as Wakame, Hirome, and Aowakame; seaweed of the genus Ecklonia belonging to the family Laminariaceae, such as Kajime, Kurome, Arame, and Tsuruarame; seaweed of the genus Sargassum belonging to the genus Sargassum, such as Akamoku, Hondawara, and Hijiki; however, it is not limited to these. Among these, Arame, Sargassum, Wakame, Kelp, and Kajime are representative examples of seaweed. Arame prefers relatively shallow waters compared to other seaweeds, Sargassum and Wakame can grow at intermediate depths, and Kelp and Kajime can grow at relatively deep depths.

[0037] Figures 2(A) to (D) show an example of the distribution of seagrass and / or seaweed in an artificial shallow area 50 (see Figure 1(B)) with two layers of roughly horizontally constructed surfaces. Figure 2 corresponds to, for example, the construction of an artificial shallow area in front of an existing seawall, where the seabed is roughly horizontal. In this case, the infill material layer is constructed with roughly equal thickness on both the offshore and shore sides so that its upper surface is roughly horizontal. Although not shown in the figures, the seabed may be uneven if the length in the shore-offshore direction is long. Figure 2(A) shows that seaweed such as Arame and Wakame are attached to the surface of the submerged breakwater 31, and the surface of the construction surface 33 is almost entirely covered with sand, where eelgrass (Zostera marina) is growing. The surface of the construction surface 43 is also almost entirely covered with sand as a base material, where koazu (Zostera marina) is growing. The water depth of the construction surface 43 is set, for example, within the range of 0.5m to 2.5m, preferably within the range of 1m to 2m, based on the low tide line. The water depth of the construction surface 33 is set, assuming it is deeper than the construction surface 43, for example, within the range of 1.5m to 6m, preferably within the range of 2m to 5m or 2m to 4m, based on the low tide line.

[0038] Figure 2(B) shows that seaweed such as Arame and Wakame are attached to the surface of the submerged breakwater 31, and the surface of the construction surface 33 is covered with stones as a base material on the side closer to the submerged breakwater 31 (offshore side) and covered with sand as a base material on the side further from the submerged breakwater 31 (shore side). In the stone-covered area of ​​the surface of the construction surface 33, seaweed such as Arame and Wakame are attached, and in the sand-covered area, eelgrass is growing. The surface of the construction surface 43 is almost entirely covered with sand as a base material, and dwarf eelgrass is growing here. The water depth of the construction surface 43 is set, for example, within the range of 0.5m to 2.5m, preferably within the range of 1m to 2m, based on the low tide line. Assuming that the water depth of the construction surface 33 is deeper than that of the construction surface 43, the depth is set, for example, within the range of 1.5m to 6m, preferably within the range of 2m to 5m or 2m to 4m, based on the low tide line.

[0039] Figure 2(C) shows that seaweed such as kelp and Ecklonia coccinea grows on the surface of the submerged breakwater 31, and the surface of the construction surface 33 is almost entirely covered with stones as a base material, where kelp and Ecklonia coccinea also grow. Seaweed such as Arame and Wakame grows on the surface of the submerged breakwater 41, and the surface of the construction surface 43 is almost entirely covered with stones as a base material, where Arame and Wakame also grow. The water depth of the construction surface 43 is set, for example, within the range of 1.5m to 6m, preferably within the range of 2m to 5m or 2m to 4m, based on the low tide line. The water depth of the construction surface 33 is set, assuming that it is deeper than the construction surface 43, for example, within the range of 4m (or 5m) to 20m, preferably within the range of 4m (or 5m) to 15m or 4m (or 5m) to 10m, based on the low tide line.

[0040] Figure 2(D) shows that kelp and other seaweeds such as Ecklonia cuneata are attached to the surface of the submerged breakwater 31, and the surface of the construction surface 33 is almost entirely covered with stones as a base material, where kelp and other seaweeds also grow. Seaweed such as Arame and Wakame are attached to the surface of the submerged breakwater 41, and the surface of the construction surface 43 is covered with stones as a base material on the side closer to the submerged breakwater 41 (offshore side), and covered with sand as a base material on the side further from the submerged breakwater 41 (shore side). In the stone-covered area of ​​the surface of the construction surface 43, seaweed such as Arame and Wakame are attached, and eelgrass (seagrass) grows in the sand-covered area. The water depth of the construction surface 43 is set, for example, within the range of 1.5m to 6m, preferably within the range of 2m to 5m or 2m to 4m, based on the low tide line. Assuming that the water depth of the construction surface 33 is deeper than that of the construction surface 43, the depth is set, for example, within the range of 4m (or 5m) to 20m, preferably within the range of 4m (or 5m) to 15m or 4m (or 5m) to 10m, based on the low tide line.

[0041] (More specific examples of materials used to construct the submerged breakwater) The submerged breakwaters 21, 31, and 41 shown in Figure 1 are all constructed as submerged breakwaters with stone materials placed on their surfaces. The stone materials may be natural stone (for example, natural stone itself or natural stone crushed to an appropriate size) or artificial stone, and in certain embodiments, natural stone may be preferred. As will be described later, in this specification, "stone" refers to solid particles with a particle size equivalent to stone (coarse stone (particle size 75 mm to 300 mm) or boulder (particle size 300 mm or larger)) based on the particle size classification of soil particles in "Soil Mechanics: Basics and Guidelines (Third Revised Edition): Edited by the Japanese Geotechnical Society" (Japanese Geotechnical Society). As for the stone material, stones of an appropriate size and material should be selected depending on the type of seaweed to be attached.

[0042] The type of artificial stone is not particularly limited, but it is preferable to use a so-called low-carbon artificial stone that has low CO2 emissions and / or can store carbon.Specific examples of low-carbon artificial stones include artificial stones containing recycled materials such as slag as raw materials; artificial stones containing CO2-fixed slag (slag or slag-like products with fixed CO2) as raw materials; and artificial stones mixed with carbon materials.Examples of slag include steel slag (blast furnace slag powder or steelmaking slag, etc.), non-ferrous slag, or slag-like products, and an example of an artificial stone containing slag as a raw material is calcia artificial stone.Examples of artificial stones mixed with carbon materials include artificial stones mixed with at least one carbon material selected from the group consisting of biochar, seashells, calcium carbonate, rice husks, and seaweed (see, for example, Japanese Patent Application No. 2023-112063). Furthermore, from the perspective of aiming for carbon neutrality, if shallow areas are created using materials with high CO2 emissions, it will take a long time for the amount of CO2 sequestration by seaweed and seagrass to exceed that amount. Therefore, the use of materials with high CO2 emissions, such as concrete blocks and steel sheet piles, is undesirable.

[0043] Submerged breakwaters 21, 31, and 41 only need to have stone materials on their surface to allow seaweed to attach, and their interiors may be made of stone or other materials. If the interior of a submerged breakwater is made of stone, the same type of stone as the surface can be used. If the interior of a submerged breakwater is made of materials other than stone, examples of such materials include modified soil, such as the low-carbon solidified soil (calcia-modified soil, etc.) described later.

[0044] To prevent the submerged breakwater from settling, ground improvement may be carried out as needed before installing submerged breakwaters 21, 31, and 41. For example, for the first layer of submerged breakwaters (submerged breakwaters 21 and 31) to be installed on the seabed, ground improvement of the seabed where the submerged breakwater will be installed may be carried out using modified soil, such as the low-carbon solidified soil (calcia-modified soil, etc.) described later. Since the second layer of submerged breakwaters (submerged breakwater 41) will be installed on the construction surface (filling layer) of the first layer, the construction surface of the first layer should be formed with a strength that takes into account the weight of the submerged breakwater, etc. Higher-strength solidified soil (that provides the strength necessary to prevent the submerged breakwater from settling) may be placed only in the area of ​​the construction surface of the first layer where the submerged breakwater will be installed.

[0045] (Examples of materials used to construct the surface) The surface layers of the construction surfaces 23, 33, and 43 shown in Figure 1 consist of one or more base materials selected from the group consisting of solidified soil, sand, gravel, and stone. In this specification, sand, gravel, and stone refer to solid particles with particle sizes corresponding to sand (particle size 0.075 mm to 2 mm), gravel (particle size 2 mm to 75 mm), and stone (as described above), respectively, based on the particle size classification of soil particles in "Soil Mechanics: Basics and Guidelines (Third Revised Edition): Edited by the Japanese Geotechnical Society." The sand may be natural sand or artificial sand, and in some embodiments, natural sand may be preferred. The gravel may be natural gravel or artificial gravel, and in some embodiments, natural gravel may be preferred. Examples of artificial sand and artificial gravel include sand and gravel with the same components as the artificial stone described above used as material for submerged breakwaters. The sand and gravel that serve as the growth base for seagrass may consist of materials that have the capacity to supply essential elements and trace elements for plants. The stone may be natural stone or artificial stone, and in some embodiments, natural stone may be preferred. The stones used are the same as those described above, which are used as stone materials on the surface of the submerged breakwater. Examples of solidified soil include: 1) the same solidified soil that constitutes the infill layer, 2) solidified soil with an increased proportion of steelmaking slag (for example, solidified soil with the same composition as ordinary calcia-modified soil (with a steelmaking slag content of about 20-30% by volume), but with the steelmaking slag content increased to about 30-50% by volume), and 3) solidified soil with increased strength due to the addition of blast furnace slag fine powder (see Appendix 2-11 of the Calcia-Modified Soil Utilization Technology Manual). The solidified soil is equivalent to soft stone (compressive strength (JIS A 5006) of 9.8 N / mm²). 2 It is preferable that the strength is increased to less than 100 cm, for example, by applying it to the surface layer of the construction surface with a thickness of about 20 cm to 100 cm (average of about 50 cm).

[0046] The infill material layers 22, 32, and 42 shown in Figure 1 are placed beneath the surface layer of the construction surface. The type of infill material constituting the infill material layers 22, 32, and 42 is not particularly limited, and various types of solidified soil can be used, for example. If the infill material is solidified soil, the outflow of the infill material from the submerged breakwater is suppressed. It is preferable that the infill material be a so-called low-carbon material (such as low-carbon solidified soil) that has low CO2 emissions and / or can store carbon. Specific examples of low-carbon solidified soil include: solidified soil containing recycled materials such as slag as a raw material; solidified soil containing CO2-fixed slag (slag or slag-like products with fixed CO2) as a raw material; solidified soil mixed with carbon materials; and so on. The types of slag include, for example, iron slag (blast furnace slag fine powder, steelmaking slag, etc.), non-ferrous slag, or slag preparations with modified components or particle sizes. Examples of solidified soil containing slag as a raw material include calcia-modified soil. Examples of solidified soil containing CO2-fixed slag as a raw material include calcia-modified soil (see, for example, Japanese Patent Application No. 2023-104689). Examples of solidified soil mixed with carbon materials include calcia-modified soil mixed with at least one carbon material selected from the group consisting of biochar, seashells, calcium carbonate, rice husks, and seaweed (see, for example, Japanese Patent Application No. 2023-024865). Various types of calcia-modified soil are based on materials mixed with calcia modifiers in dredged soil, and calcia modifiers are materials obtained by controlling the components and particle size of converter-type steelmaking slag. For information on using calcia-modified soil or calcia-modified soil as a filling material, see, for example, the method described in Japanese Patent Publication No. 2011-208365, or refer to the website of the Calcia-Modified Soil Research Association.

[0047] (Construction location, etc.) The location where the artificial shallow area 20.50 is created is not particularly limited as long as it is underwater, but for example, it may be installed in the sea in front of the seawall or in the sea behind the breakwater.

[0048] [Embodiment 2] Other embodiments of the present invention will be described in detail below with reference to the drawings. Figure 3 shows a modified example of the artificial shallow area 20.50, illustrating the relationship between a submerged breakwater and a construction surface connected thereto. The submerged breakwater 61 is formed by stacking stones. The construction surface 63 consists of a filling material layer 62 and a surface layer placed on top of it. The filling material layer 62 is raised in a border-like manner in the area in contact with the submerged breakwater 61, and is a recessed, substantially horizontal plane in the area away from the submerged breakwater 61. The surface layer of the construction surface 63 (for example, a layer covered with sand or gravel as a base material) is placed on the recessed, substantially horizontal plane of the filling material layer 62. This configuration prevents the sand or gravel forming the surface layer of the construction surface 63 from flowing into the gaps between the stones forming the submerged breakwater 61. In particular, in the case of a shallow-water structure having N layers (where N is an integer of 2 or more) of roughly horizontal construction surfaces located at different water depths, the outflow of sand and gravel from the upper (shallower) construction surface to the lower construction surface via a submerged breakwater is prevented.

[0049] 〔summary〕 The scope of this invention also includes, for example, the following: 1) An artificial shallow area located underwater, comprising a first submerged breakwater having at least a surface covered with stone, and a first substantially horizontal construction surface connected to the first submerged breakwater, wherein the surface layer of the first construction surface consists of one or more base materials selected from the group consisting of solidified soil, sand, gravel, and stone. 2) An artificial shallow area according to 1), comprising a second submerged breakwater provided on the first construction surface and having at least stone material on its surface, and a substantially horizontal second construction surface connected to the second submerged breakwater, wherein the surface layer of the second construction surface consists of one or more base materials selected from the group consisting of solidified soil, sand, gravel, and stone. 3) The artificial shallow area described in 2), further comprising one or more substantially horizontal reclaimed surfaces located at a different depth than the first and second reclaimed surfaces. 4) An artificial shallow area as described in any of 1) to 3), wherein part or all of the base material of the surface layer of the first construction surface described above consists of stone. 5) An artificial shallow area as described in any of 1) to 4), where the surface water depth of the first reclaimed surface is up to 25m based on the low tide line. 6) An artificial shallow area according to any one of 1) to 5), wherein the filling material placed beneath the surface layer of the constructed surface is a low-carbon solidified soil, and / or one of the base materials constituting the surface layer of the constructed surface is a low-carbon artificial stone. 7) The low-carbon solidified soil described above is calcia-modified soil, or calcia-modified soil mixed with any of the following: CO2-fixed slag, biochar, seashells, calcium carbonate, rice husks, or seaweed, as described in 6). 8) The low-carbon artificial stone described above is an artificial stone made from steelmaking slag, an artificial stone made from blast furnace slag powder, or an artificial stone made by mixing any of the following: biochar, seashells, calcium carbonate, rice husks, or seaweed, as described in 6). 9) The surface of the above-mentioned constructed area is an artificial shallow area described in any of 1) to 8) with a slope of 1 / 10 or less relative to the horizontal plane. 10) If the surface layer of the above-mentioned construction surface consists of solidified soil, the solidified soil has strength equivalent to that of soft stone, and is an artificial shallow area as described in any of 1) to 9).

[0050] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0051] For example, taking into account the topography of the area where the artificial shallow area is to be installed and the tidal fluctuations of the sea area, the first and second construction surfaces may be installed in a T-shape or L-shape in plan view so that a predetermined water depth can be easily obtained.

[0052] Furthermore, with respect to a shallow area having a first and second construction surface located at different depths, although the above-described embodiment was explained assuming that the first construction surface is deeper than the second construction surface, the first construction surface may be shallower than the second construction surface. [Industrial applicability]

[0053] This invention can be used, for example, in fields such as marine civil engineering and fisheries. [Explanation of Symbols]

[0054] 20.50 Shallow water 21.31 Submerged breakwater (First submerged breakwater) 23.33. Reclaimed surface (first reclaimed surface) 41 Submerged breakwater (Second submerged breakwater) 43. Reclaimed surface (second reclaimed surface)

Claims

1. An artificial shallow area located underwater, A first submerged breakwater with at least stone materials placed on its surface, Including a substantially horizontal first construction surface connected to the first submerged breakwater described above, The surface layer of the first construction surface described above consists of one or more base materials selected from the group consisting of solidified soil, sand, gravel, and stone. An artificial shallow area.

2. A second submerged breakwater is provided on the first construction surface described above, and at least one of its surfaces is covered with stone materials. It includes a substantially horizontal second construction surface connected to the second submerged breakwater described above, The surface layer of the second construction surface described above consists of one or more base materials selected from the group consisting of solidified soil, sand, gravel, and stone. The artificial shallow area according to claim 1.

3. The artificial shallow area according to claim 2, further comprising one or more substantially horizontal reclaimed surfaces located at a different depth than the first reclaimed surface and the second reclaimed surface described above.

4. The artificial shallow area according to claim 1 or 2, wherein part or all of the base material of the surface layer of the first construction surface described above is made of stone.

5. The artificial shallow area according to claim 1 or 2, wherein the surface water depth of the first constructed surface is up to 25 m, based on the low tide line.

6. An artificial shallow pool according to any one of claims 1 to 3, wherein the filling material placed beneath the surface layer of the above-mentioned construction surface is a low-carbon solidified soil, and / or one of the base materials constituting the surface layer of the above-mentioned construction surface is a low-carbon artificial stone.

7. The above low-carbon solidified soil is calcia-modified soil, or CO ２ The artificial shallow area according to claim 6, which is a calcium-modified soil mixed with fixed slag, biochar, seashells, calcium carbonate, rice husks, or seaweed.

8. The artificial shallow area according to claim 6, wherein the low-carbon artificial stone is an artificial stone made from steelmaking slag, an artificial stone made from blast furnace slag fine powder, or an artificial stone mixed with any of biochar, seashells, calcium carbonate, rice husks, or seaweed.

9. The artificial shallow area according to claim 1 or 2, wherein the surface of the constructed area has a slope of 1 / 10 or less with respect to the horizontal plane.

10. The artificial shallow area according to claim 1 or 2, wherein the surface layer of the above-mentioned construction surface consists of solidified soil, and the solidified soil has a strength equivalent to that of soft stone.

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