Underwater submerged structure, manufacturing method of underwater submerged structure, and formwork used therefor

Abstract

To provide an underwater installation structure which allows sea weed and sea grass to perform adherence efficiently, even in a coastal sea area where sea desertification occurs.SOLUTION: An underwater installation structure comprises: a frustum-shaped substrate; and a step part which is formed in a step-shape on a whole inclination side surface of the substrate. A surface layer on a top surface of the substrate and the step part are formed of a cotton-like bamboo fiber-containing part in which, cotton-like bamboo fibers obtained by collapsing raw bamboo into a cotton-state are coagulated and cured using as a binder, mortar obtained by adding water or sea water to a mixture of cement and fine aggregate and kneading. A part other than the cotton-like bamboo fiber-containing part on the substrate is formed of a cotton-like bamboo fiber non-containing part in which, coarse aggregate is encapsulated by mortar and is cured and coagulated. A bottom face of the substrate is horizontal, and on the step part, a step cliff part which is formed in a surface structure which is inclined vertically or inclined inward of the substrate and is erected, and a terrace part formed in a horizontal or recessed surface structure are alternately repeatedly arranged on the whole periphery of the step part, and on each terrace part, along a circumferential direction, a recess groove is formed.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a submerged structure that is submerged in water and has a surface on which aquatic plants grow, a method for manufacturing the submerged structure, and a formwork used therefor. [Background technology]

[0002] As submerged structures that are submerged in water and have a surface on which aquatic plants grow or on which fish and shellfish gather, those described in Patent Documents 1 to 7 are known.

[0003] The "fish reef" described in Patent Document 1 is made by putting one or more kinds of fish reef materials, such as natural stones, broken stones, concrete waste, brick waste, slag, and shells, into a mixer, adding water to cement or cement and fine sand, and then putting it into a formwork to harden it into a fixed-shaped agglomerate fish reef. (See Patent Document Specification, page 3, line 1 in the upper left corner to line 18 in the lower left corner, and Figures 3 and 4.)

[0004] The "concrete molded body for fishing ground facilities" described in Patent Document 2 is made by forming a concrete formwork with an open top surface using a mesh-like base material and mesh-like side frames erected on the periphery of the base material, filling the inside of this concrete formwork with shells as aggregate, and spraying a paste-like solidifying agent (cement) onto the shells to form a form that exposes the shells on the surface (see Figures 1 and 2 of Patent Document 2). Patent Document 3 also describes a similar "artificial reef."

[0005] The "molded body for fishing ground facilities" described in Patent Document 4 is made by molding a hollow inner cylinder made of concrete, setting up a cylindrical formwork with water permeability so as to surround the inner cylinder, filling the space between the formwork and the inner cylinder with shells, spraying a paste-like solidifying agent (cement) onto the shells, and molding an outer cylinder that covers the outer periphery of the inner cylinder so that the shells are visible on the surface. (See Figures 1 and 2 of the Patent Document)

[0006] Patent Document 5 describes a concrete block for use in fish reefs, which is characterized by being formed by pouring concrete that contains at least one of shells or crushed pieces of pottery, porcelain, ceramic, concrete, and asphalt as aggregate.

[0007] Patent Document 6 describes a fish fly attractant for artificial fish reefs, which is characterized in that raw shellfish discarded in large quantities from cleaning seawater intake channels and oyster farms are washed and sorted to turn into scum-remaining shell fragments, and the shell fragments are then attached to the surface of the artificial fish reef components with adhesive, enlarging the gaps between the shell fragments and causing the shell fragments to protrude from the surface.

[0008] Patent Document 7 describes a structure for creating a seaweed bed, which comprises a skeletal structure having at least one columnar section erected on a block-shaped base, and a seaweed seed support device with seaweed seeds grown on a support base, which is attached in a roughly annular shape to an appropriate position on the outer periphery of the columnar section, and the seaweed seed support device is attached via an anti-slip means.

[0009] In addition, a structure for dumping shells on the seabed, although not for the purpose of growing underwater plants, is known as described in Patent Document 8. The "shell dumping container" described in Patent Document 8 is a shell dumping container formed by stretching a water-permeable net (steel or plastic net) on a three-dimensional outer frame to form a storage space, and filling it with shells and other waste materials. A water-permeable path is provided vertically or horizontally within the storage space, with an inlet and an outlet open on each side of the outer frame and a water-permeable net stretched on the inner surface that is continuous with the water-permeable net stretched on each side, and legs with a fixed base are provided on the bottom of the outer frame, and a movement prevention stake is further provided on the base. (See Figures 1 and 2 of Patent Document 8.) When waste materials such as oyster shells are stored in the storage space and dumped into the ocean, the waste filled in the storage space is washed into the storage space by ocean currents through the water-permeable net, promoting aquatic organisms and aerobic microbial decomposition. In addition, by providing a water passage, it is possible to allow ocean currents to reach corners of the storage space that would be difficult for the ocean currents to reach depending on the configuration of the outer frame. This is said to prevent the anaerobic decay of oyster meat, wisteria jars, seaweed, and other attached organisms that adhere to waste such as oyster shells, generating hydrogen sulfide and polluting seawater. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 56-099736 [Patent Document 2] JP 2003-061504 A [Patent Document 3] Japanese Patent Application Publication No. 11-225612 [Patent Document 4] JP 2003-092951 A [Patent Document 5] Japanese Patent Application Publication No. 11-46619 [Patent Document 6] Japanese Patent Application Publication No. 9-215459 [Patent Document 7] JP 2000-139267 A [Patent Document 8] Specification of Utility Model Registration No. 3031263 Summary of the Invention [Problem to be solved by the invention]

[0011] In recent years, the problem of rocky shore denudation, in which seaweed has significantly decreased and disappeared and does not grow abundantly, has become serious in coastal waters all over Japan. In coastal waters where rocky shore denudation has occurred, simply placing oyster shells or other shells in containers or structures made of cement solidified and fixed shells, as described in the Background Art section above, on the seabed is unlikely to result in the growth of seaweed or seagrass, and therefore is thought to have little effect in attracting marine organisms that use seaweed or seagrass communities as a feeding ground or habitat.

[0012] Therefore, an object of the present invention is to provide an underwater submerged structure that allows seaweed and seaweed to effectively grow in coastal waters where coastal barrenness has occurred, a manufacturing method for the underwater submerged structure, and formwork for use therein. [Means for solving the problem]

[0013] A first configuration of the underwater submerged structure according to the present invention is an underwater submerged structure for being submerged on the bottom of a body of water and for growing aquatic plants on its surface, a base body formed in a frustum shape having a lower surface portion, an upper surface portion having an area smaller than that of the lower surface portion, and an inclined side surface formed from the lower surface portion to the upper surface portion and inclined upward from the lower surface portion to the upper surface portion as a whole; A step portion formed in a step shape over the entire inclined side surface of the base body, The surface layer of the upper surface of the base and the step portion are composed of a cotton-like bamboo fiber-containing portion in which cotton-like bamboo fibers, which are made by crushing raw bamboo into a cotton-like form, are coagulated and hardened using a mortar made by adding water or seawater to a mixture of fine aggregate and cement as a binder. The portion of the base other than the portion containing cotton-like bamboo fiber is composed of a portion not containing cotton-like bamboo fiber, in which coarse aggregate is sealed with the mortar and set and hardened, When the bottom surface of the base is horizontal, the step portion has steps formed around the entire periphery, the steps being made up of alternating cliff portions formed in a surface structure that rises vertically or inclined toward the inside of the base and terrace portions formed in a horizontal or recessed surface structure, A recessed groove is formed in each of the terraces along the circumferential direction of the terrace.

[0014] According to this configuration, after the underwater submerged structure is installed on the bottom of the ocean, river, or lake, nitrogen fixing bacteria in the water are induced to grow in the cotton-like bamboo fiber contained in the cotton-like bamboo fiber-containing part of the surface layer and the step of the upper surface of the base, and nitrogen fertilizer components are accumulated over time. As a result, nitrogen compounds, which are essential fertilizer components for aquatic plants, are accumulated on the surface of the upper surface of the base and the surface of the step, promoting the growth of aquatic plants. Therefore, for example, even in coastal sea areas where seaweed denudation has occurred, the growth of aquatic plants is promoted on the surface of the upper surface of the base and the surface of the step, and it functions as a water bottom greening material or fish reef where seaweed and seaweed can effectively grow. In addition, since the underwater submerged structure is a concrete structure in which the cotton-like bamboo fibers are only contained in the stepped parts (sloping side parts) and the surface layer of the top part of the base, and no cotton-like bamboo fibers are contained deeper than the surface layer of the base (formed by sealing coarse aggregate in mortar and setting / hardening), the parts other than the parts containing the cotton-like bamboo fibers do not contain organic matter inside, and the strength of the entire structure is maintained for a long period of time.

[0015] In addition, the concave grooves formed on the terraces of the steps increase the surface area of ​​the steps of the submerged structure, which results in a larger contact area between the cotton-like bamboo fibers contained in the steps and the external water (surface area exposed to water), making it easier for nitrogen-fixing bacteria present in the water to attach to the cotton-like bamboo fibers, and the nitrogen-fixing bacteria attached to the cotton-like bamboo fibers can easily absorb the nitrogen present in the water. This allows for efficient accumulation of nitrogen fertilizer components. In addition, the protrusions create unevenness on the sides of the submerged structure, making it easier for seeds and spores of aquatic plants to settle on the sides of the submerged structure, which further promotes the attachment of aquatic plants.

[0016] Here, "frustum-shaped" does not mean a mathematically strict shape of a frustum (a three-dimensional figure obtained by removing a similarly reduced cone that shares a vertex from a cone), but a shape that has a bottom surface, a top surface, and inclined sides and is close to a frustum (allowing for the sides to have irregularities). "Frustrum-shaped" includes cones with various shapes of bottom and top surfaces, such as a circular truncated cone, an elliptical cone, and a polygonal truncated cone (triangular truncated cone, square truncated cone, etc.). "Cotton-like bamboo fiber obtained by crushing raw bamboo into a cotton-like shape" refers to cotton-like bamboo fiber produced by crushing raw bamboo with a twin-screw crusher until the cell walls are split open, and then cutting the bamboo with a cutter blade at the outlet of the twin-screw crusher. "Fine aggregate" refers to a supplementary material added to cement in mortar, such as sand, granite, sand-like clinker, and fly ash. Portland cement, blast furnace cement, magnesia cement, etc. can be used as "cement". In addition, additives may be added to the cement to improve physical properties such as water resistance and strength. In particular, if a phosphate compound is used as an additive, phosphorus, an essential fertilizer component for aquatic plants, can also be supplied at the same time, allowing seaweed and seaweed to grow more effectively. "Coarse aggregate" refers to aggregate with a large particle size, and includes coarse aggregates used in normal concrete such as gravel, stone blocks, and coarse clinker, as well as coarse waste materials having a calcium skeleton in the fishing or livestock industry such as shells, oyster shells, sea urchin shells, fish bones, and animal bones. "Concave groove" refers to a groove with a concave streak (a long, thin, continuous concave). "The step is formed around the entire circumference" includes the case where the step is formed in a ring shape around the entire circumference (see Examples 1 to 6) as well as the case where the step is formed in a spiral shape around the entire circumference (see Example 7).

[0017] A second configuration of the underwater submerged structure of the present invention is characterized in that, in the first configuration, each of the concave grooves has a cross-sectional shape formed into a V-shaped groove in which the groove width gradually increases with distance from the groove bottom, and when the bottom surface of the base is horizontal, the inner groove side surface is a vertical surface or an inclined surface that slopes upward toward the inside of the base and smoothly connects to the cliff portion without creating a step, and the outer groove side surface is a vertical surface or an inclined surface that slopes upward toward the outside of the base.

[0018] In this way, if the grooves are formed in a V-shaped groove, it becomes easy to hold the cotton-like bamboo fibers in the step and solidify them with mortar when manufacturing the submerged structure. In addition, the step of the submerged structure becomes a sawtooth step, and when the submerged structure is placed underwater, if there is a flow in the surrounding water, the flow becomes a vortex on the surface of the step and easily penetrates to the vicinity of the bottom of the groove. Therefore, the water in the groove is replaced well, and the nitrogen fixing bacteria attached to the cotton-like bamboo fibers can more easily absorb the nitrogen present in the water.

[0019] Here, "smoothly and continuously connected without creating a step" means that the boundary is connected as a continuous flat surface, curved surface, or bent surface without creating a step.

[0020] In the second configuration, the case where both the inner groove side surface and the outer groove side surface are vertical surfaces is of course excluded. If both groove side surfaces of the groove are vertical, the groove width becomes 0, and the groove does not have a "V-shaped groove shape."

[0021] The third configuration of the underwater submerged structure of the present invention is characterized in that, in the first configuration, each of the concave grooves has a cross-sectional shape formed like a U-shaped groove having a flat groove bottom, and, when the bottom surface of the base is horizontal, an inner groove side surface that rises from the inner end of the groove bottom, sloping vertically or upward toward the inside of the base, and an outer groove side surface that rises from the outer end of the groove bottom, sloping vertically or upward toward the outside of the base, and the inner groove side surface is smoothly and continuously connected to the cliff portion without creating a step.

[0022] In this way, if the grooves are formed in a U-shape with the outer side of the groove inclined upward toward the outside of the base and rising from the outer end of the flat groove bottom, when the underwater submerged structure is installed underwater, if there is a current in the surrounding water, the current will become a vortex on the surface of the step and easily penetrate to the vicinity of the groove bottom of the groove. Therefore, the water in the grooves is replaced well, and the nitrogen fixing bacteria attached to the cotton-like bamboo fibers can more easily absorb the nitrogen present in the water.

[0023] A fourth configuration of the underwater submerged structure of the present invention is characterized in that, in any one of the first to third configurations, a sand and mud discharge groove is formed on the sloping side of the base, which is a groove that intersects with the cliff portion and the terrace portion of the step portion from the upper part to the lower part of the slope.

[0024] According to this configuration, by providing the sand and mud flushing groove, after the underwater submerged structure is installed on the bottom of the water, the sand and mud that enters the grooves of the terrace part is discharged from the sand and mud flushing groove by the water current, so that the grooves are not easily buried by the sand and mud, and the reduction in the area of ​​the surface of the step part exposed to the water (exposed surface area) due to the covering of the sand and mud is suppressed. Therefore, the high nitrogen fixation function by the nitrogen fixing bacteria is maintained for a long period of time.

[0025] A first aspect of the manufacturing method of the submerged structure according to the present invention is a manufacturing method of a submerged structure for sinking to the bottom of water and growing aquatic plants on its surface, comprising the steps of: A box chamber is formed, the box chamber being in the shape of a box with a frustum-shaped internal space with a smaller area at the lower bottom than at the upper bottom, the upper bottom side being fully open, and with the open end of the box chamber facing upward, the entire periphery of the internal side wall surface of the box chamber is inclined upward from the center of the box chamber toward the outside, and a step structure is formed along the entire periphery of the internal wall side surface, in which a cliff portion formed in a planar structure that rises vertically or inclined upward from the center of the box chamber toward the outside, and a terrace portion formed in a concave planar structure are alternately repeated, and a structure forming frame having a groove formed along the circumferential direction of each terrace portion is installed so that the open end of the box chamber faces upward, The cotton-like bamboo fiber obtained by crushing raw bamboo into a cotton-like form is at least Structure forming frameA first step of laying the sheet so as to cover the concave portion of the concave and convex portions formed on the inner side wall surface of the chamber and the inner bottom surface of the chamber; The above Structure forming frame a second step of pouring coarse aggregate into the box chamber from the upward open end of the box chamber and packing the aggregate into the box chamber; The coarse aggregate is added to the Structure forming frame A mortar made by adding water or seawater to a mixture of fine aggregate and cement is poured into the box from the upward opening end of the box. Structure forming frame and a third step of filling the inside of the box chamber with the mortar.

[0026] According to this configuration, in the first step, the cotton-like bamboo fiber is Structure forming frame When installed on the inner side wall of Structure forming frame The bamboo fibers are piled up on the step terrace surface of the inner side wall and the inner bottom surface. Structure forming frame Coarse aggregate is poured in through the opening at the top and packed in, and then in the third process, mortar made by adding water or seawater to a mixture of fine aggregate and cement is poured in and filled in. After the mortar sets and hardens, Structure forming frame Once removed, the underwater submerged structure is manufactured. Structure forming frame After laying cotton-like bamboo fiber inside, coarse aggregate or filler is added, mortar is injected, and the work is left to set, so no special civil engineering machinery is required and even fishery workers without specialized civil engineering skills can easily carry out the work. Also, if marine waste such as shells, oyster shells, sea urchin shells, and fish bones are used as the coarse aggregate, it becomes possible to dispose of these marine wastes easily without spreading bad odors to the surrounding area, and since these marine wastes are sealed in mortar and sunk to the bottom of the water, they do not put a burden on the environment.

[0027] In addition, the underwater submerged structure to be manufactured has a side surface and a top surface ( Structure forming frameCotton-like bamboo fiber is only contained in the surface layer of the bamboo structure (the surface of the part that abuts the inner bottom surface of the bamboo structure), and cotton-like bamboo fiber is not contained in the deeper part of the structure below the surface, so that the overall strength is high. In addition, since cotton-like bamboo fiber is contained in the side and top parts, after installation on the bottom of the water, this cotton-like bamboo fiber induces nitrogen fixing bacteria in the water, and nitrogen fertilizer components accumulate over time, which promotes the attachment of underwater plants and functions as a water bottom greening material or fish reef.

[0028] Also, Structure forming frame Due to the grooves formed on the terraced portion of the step on the inner side wall, a step shape is formed on the side of the manufactured submerged structure, and a groove is formed around the entire periphery of the terraced portion of the step. This step contains a large amount of cotton-like bamboo fiber. The step structure with the grooves increases the surface area of ​​the side of the submerged structure, so that nitrogen fertilizer components can be efficiently accumulated. In addition, because the side of the submerged structure is uneven, it becomes easier for the seeds and spores of aquatic plants to settle on the side of the submerged structure, which further promotes the establishment of aquatic plants.

[0029] Here, "laying" refers to laying the cotton-like bamboo fibers. Specifically, the cotton-like bamboo fibers are sprinkled or sprayed on the bamboo. Structure forming frame This refers to spreading the material over the terraces on the inner walls and the bottom of the interior. "Sprinkling" refers to scattering the material by shaking it without rolling it. "Spraying" refers to applying pressure (spray pressure) to blow the material onto the surface.

[0030] A second configuration of the manufacturing method for an underwater submerged structure of the present invention is characterized in that, in the first configuration, within the groove of the concave groove provided in each of the terrace portions of the inner side wall surface of the box chamber of the structure forming frame used in the first step, a plurality of convex ridge portions formed as interrupted ridges are provided at intervals along a straight line that intersects across each of the cliff portions and each of the terrace portions from the upper to lower sloping portions of the inner side wall surface of the box chamber.

[0031] As a result, a sand and mud discharge groove is formed on the inclined side of the manufactured underwater submerged structure, which is a groove that intersects with the cliff portion and the terrace portion of the step portion from the upper to lower slope.

[0032] A first configuration of the structure forming formwork according to the present invention is a structure forming formwork used in the manufacturing method of the underwater submerged structure of the first configuration, A box-shaped chamber is formed, the lower surface of which has a small area compared to the upper surface, and the upper surface side is entirely open, When the open end of the chamber is the top, the entire circumference of the inner side wall surface of the chamber is inclined upward from the center of the chamber toward the outside, In addition, a step structure is formed in which a cliff portion formed in a plane structure that rises vertically or inclined upward from the center of the box chamber toward the outside and a terrace portion formed in a concave plane structure are alternately repeated around the entire circumference of the inner wall side surface, A recessed groove is formed in each of the terraces along the circumferential direction of the terrace.

[0033] The second configuration of the formwork for forming a structure according to the present invention is the first configuration, wherein the cross-sectional shape of each of the concave grooves is formed into a V-shaped groove shape in which the groove width gradually increases as it moves away from the groove bottom, Furthermore, when the inner bottom surface of the box chamber is horizontal, the outer groove side surface of the concave groove is a vertical surface or an inclined surface that slopes upward toward the outside of the box chamber and smoothly connects to the step cliff portion without creating a step, and the inner groove side surface of the concave groove is an inclined surface that slopes upward toward the inside of the box chamber.

[0034] The third configuration of the structure forming formwork according to the present invention is the first configuration, wherein each of the concave grooves has a cross-sectional shape formed into a U-shaped groove having a flat groove bottom, and an outer groove side surface that rises from the outer end of the groove bottom, either vertically or inclined upward toward the outside of the box chamber, when the inner bottom surface of the box chamber is horizontal, and an inner groove side surface that rises from the inner end of the groove bottom, either vertically or inclined upward toward the inside of the box chamber, The outer groove side surface is smoothly and continuously connected to the cliff portion without creating a step.

[0035] A fourth configuration of the structure forming formwork of the present invention, in any one of the first to third configurations, is characterized in that within the groove of the concave groove provided in each of the terrace portions of the inner side wall surface of the box chamber, a plurality of convex ridge portions formed as interrupted ridges are provided at intervals along a straight line that intersects across each of the cliff portions and each of the terrace portions from the upper to lower sloping portions of the inner side wall surface of the box chamber. Effect of the Invention

[0036] As described above, according to the present invention, the cotton-like bamboo fibers contained in the cotton-like bamboo fiber-containing portion of the surface layer and step of the upper surface of the base induce nitrogen-fixing bacteria in the water after installation on the bottom of the water, and nitrogen fertilizer components accumulate over time, thereby promoting the growth of underwater plants even in coastal waters where rocky shoreline bleaching has occurred, and providing a waterbed greening material or fish reef on which seaweed and seaweed can effectively grow. [Brief description of the drawings]

[0037] [Figure 1] 1A and 1B are perspective views of a structure forming formwork used in a manufacturing method for an underwater submerged structure according to a first embodiment of the present invention, respectively seen obliquely from above and from the front left, and seen obliquely from below and from the front right. [Diagram 2] 2A is a plan view of the structure forming formwork of FIG. 1, FIG. 2B is a cross-sectional view taken along line AA, and FIG. 2C is a cross-sectional view taken along line BB. [Diagram 3]1A to 1C are diagrams showing steps of a method for manufacturing the underwater submerged structure of Example 1. [Figure 4] (a) The raw material for cotton-like bamboo fiber, (b) the manufacturing process for cotton-like bamboo fiber, and (c) a photograph of the appearance of cotton-like bamboo fiber. [Diagram 5] This is an electron microscope photograph of cotton-like bamboo fibers. [Figure 6] FIG. 2A is an external perspective view of the underwater submerged structure of the first embodiment, and FIG. 2B is a cross-sectional perspective view. [Figure 7] 1 is a photograph showing the appearance of the surface of a specimen of the underwater submerged structure of Example 1. [Figure 8] FIG. 13 is an external perspective view of (a) a formwork for forming a structure and (b) an external perspective view of an underwater submerged structure, in which the number of steps of the cliff portion 5a of the inner side wall surface 5 is 12. [Figure 9] 1A and 1B are perspective views of a structure forming formwork used for manufacturing the underwater submerged structure of Example 2, respectively viewed from diagonally above and from the front left, and viewed from diagonally below and from the front right. [Figure 10] 10A is a plan view, FIG. 10B is a cross-sectional view, and FIG. 10C and FIG. 10D are partially enlarged cross-sectional views of the structure forming formwork of FIG. [Figure 11] FIG. 13A is an external perspective view of the underwater submerged structure of the second embodiment, and FIG. [Figure 12] 13A and 13B are oblique views of a structure forming formwork used for manufacturing the underwater submerged structure of Example 3, seen diagonally from above and from the front left, and from below and from the front right, respectively. [Figure 13] 13A is a plan view of the structure forming formwork of FIG. 12, (b) a cross-sectional view taken along line AA, (c) a cross-sectional view taken along line BB, and (d) a partially enlarged cross-sectional view. [Figure 14] 14A and 14B are perspective views of the exterior and cross-sectional views, respectively, of an underwater submerged structure of Example 3 manufactured using the structure molding formwork of FIGS. [Figure 15] 13A and 13B are oblique views of a structure forming formwork used for manufacturing the underwater submerged structure of Example 4, seen diagonally from above and from the front left, and from below and from the front right, respectively. [Figure 16]16A is a plan view of the structure forming formwork of FIG. 15, (b) a cross-sectional view taken along line AA, (c) a cross-sectional view taken along line BB, and (d) a partially enlarged cross-sectional view. [Figure 17] 17A and 17B are external perspective and sectional perspective views, respectively, of an underwater submerged structure of Example 4 manufactured using the structure molding formwork of FIGS. [Figure 18] 13A and 13B are oblique views of a structure forming formwork used for manufacturing the underwater submerged structure of Example 5, seen diagonally from above and from the front left, and from below and from the front right, respectively. [Figure 19] 19A is a plan view of the structure forming formwork of FIG. 18, (b) a cross-sectional view taken along line AA, (c) a cross-sectional view taken along line BB, and (d) a cross-sectional view taken along line CC. [Figure 20] 19A and 19B are an external perspective view and a cross-sectional perspective view, respectively, of an underwater submerged structure of Example 5, which is manufactured using the structure molding formwork of FIGS. [Figure 21] 13A and 13B are oblique views of a structure forming formwork used for manufacturing the underwater submerged structure of Example 6, seen diagonally from above and from the front left, and from below and from the front right, respectively. [Figure 22] 22A is a plan view of the structure-forming formwork 1 in FIG. 21, (b) is a cross-sectional view taken along line AA (line BB), and (c) is a partially enlarged cross-sectional view. [Diagram 23] 21 and 22. FIG. 22 shows (a) an external perspective view, (b) a cross-sectional perspective view, and (c) a partially enlarged cross-sectional view of an underwater submerged structure 10 of Example 6, which is manufactured using the structure forming formwork 1 of FIGS. [Figure 24] 13A and 13B are perspective views of a structure forming formwork 1 used for manufacturing an underwater submerged structure 10 of Example 7, respectively viewed obliquely from above and from the front left, and viewed obliquely from below and from the front right. [Diagram 25] 25A is a plan view of the structure-forming formwork 1 in FIG. 24, (b) is a cross-sectional view taken along line AA, and (c) is a partially enlarged cross-sectional view. [Figure 26] FIG. 13(a) is an external perspective view and (b) is a cross-sectional view of the underwater submerged structure 10 of Example 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. EXAMPLES

[0039] Fig. 1 is a perspective view of a structure-forming formwork used in a manufacturing method for an underwater submerged structure according to a first embodiment of the present invention, as viewed from diagonally above the left front and as viewed from diagonally below the right front. Fig. 2 is a plan view of the structure-forming formwork shown in Fig. 1, as viewed from an arrowed line AA (b), and as viewed from an arrowed line BB (c).

[0040] The structure-forming formwork 1 is made of metal or resin. The structure-forming formwork 1 in Fig. 1 is formed in an overall rectangular shape when viewed from above, and the four upper sides of the formwork body 2 in the center have rectangular frame-shaped legs 3 formed downward to prevent it from falling over. Note that Figs. 1 and 2 show an example in which the structure-forming formwork 1 is formed in a substantially square shape when viewed from above, but the length and width of the structure-forming formwork 1 can be set as desired. Also, the shape is not limited to a rectangular shape when viewed from above, and it can also be a polygon.

[0041] The formwork body 2 is formed in a box shape with a funnel-shaped box chamber 2a whose one end is fully open. With the open end of the box chamber 2a facing upward, the outer wall surface of the formwork body 2 has a rectangular prism-like upper surface and an inverted pyramid-like lower surface (see FIG. 1(b)). The upper surface of the outer wall surface of the formwork body 2 and the outer surface of the leg 3 are connected so as to be flush with each other. The inner wall surface of the box chamber 2a of the formwork body 2 is composed of a central rectangular planar inner bottom surface 4 at the bottom (innermost part) and inner side wall surfaces 5 formed in a stepped structure that slopes upward from the inside to the outside from each of the four sides of the inner bottom surface 4. This stepped structure is a structure in which a step cliff portion 5a that slopes vertically or outwardly upward and a terrace portion 5b in which a concave groove 5c is formed around the entire circumference are alternately repeated (see the partially enlarged view of FIG. 2(c)). The cliff sections 5a except for the lowest one are formed so as to be vertical when the formwork body 2 is placed with the inner bottom surface 4 horizontal. The cliff section 5a of the lowest one is formed so as to be inclined upward and outward when the formwork body 2 is placed with the inner bottom surface 4 horizontal (see Figs. 2(b) and (c)).

[0042] Here, the "terrace portion" in a step structure refers to the portion equivalent to the terrace cliff in a terrace structure, and the "terrace portion" refers to the portion equivalent to the terrace surface in a terrace structure (the portion other than the terrace portion). More precisely, a "step section" refers to a slope portion that corresponds to a section portion consisting of a set of points P on the slope section line, where, when a slope with a step structure is cut by a vertical plane including the normal to the slope, a directed line segment along the slope from the lowest point of the slope to the highest point of the slope is defined as the "slope section line," and a straight line connecting the lowest point of the slope to the highest point of the slope is defined as the "average slope line," and the slope direction (tangential vector) at point P is the same as the slope direction of the average slope line (directional vector from the lowest point of the slope to the highest point of the slope) (the positive and negative values ​​of the slope angle at point P relative to the horizontal plane (horizontal line) are the same as the positive and negative values ​​of the slope angle of the average slope line relative to the horizontal plane (horizontal line)), and there is no section higher than point P or the same height as point P in the section on the lower side of the slope from point P on the slope section line.

[0043] The cross section of the concave groove 5c formed in each terrace portion 5b is formed in such a shape that the outer portion 5c-2 and the inner portion 5c-3 rise vertically or outward from both sides of the flat groove bottom portion 5c-1 (see the partially enlarged view of FIG. 2(c)). The groove side surface of the outer portion 5c-2 is formed so as to be vertical when the formwork body 2 is placed with the inner bottom surface 4 horizontal, and is smoothly connected to the cliff portion 5a without creating a step. In addition, the groove side surface of the inner portion 5c-3 is formed so as to rise vertically from the groove bottom portion 5c-1 and curve inward and upward when the formwork body 2 is placed with the inner bottom surface 4 horizontal.

[0044] In the example shown in Figures 1 and 2, the groove side of the outer portion 5c-2 is perpendicular to the inner bottom surface 4, but as another example, when the formwork body 2 is placed with the inner bottom surface 4 horizontal, the groove side of the outer portion 5c-2 can be configured to incline outward and upward.

[0045] In addition, in Figures 1 and 2, for convenience of illustration, the number of steps on the inner side wall surface 5 is six, but the number of steps can be changed appropriately depending on the size of the underwater submerged structure to be manufactured.

[0046] Next, a method for manufacturing an underwater submerged structure using the above-mentioned structure forming formwork 1 will be described. Fig. 3 is a diagram showing steps of the method for manufacturing an underwater submerged structure according to Example 1. (S1) to (S5) in Fig. 3 show diagrams of each step.

[0047] First, in step (S1), the structure forming formwork 1 shown in Figs. 1 and 2 is placed on a horizontal ground surface so that the open end of the box chamber 2a faces upward.

[0048] Next, in step (S2), the cotton-like bamboo fiber 6 obtained by crushing raw bamboo into a cotton-like state is subjected to at least Structure forming frame The bamboo fibers are laid so as to cover the concave grooves 5c formed on the inner side wall surface 5 of the box chamber 2a of 1 and the inner bottom surface 4 of the box chamber 2a. The cotton-like bamboo fibers 6 may be laid by spraying, but as spraying requires a dedicated spraying machine, the cotton-like bamboo fibers 6 are laid by scattering (sprinkling) them. "Scattering (sprinkling)" refers to sprinkling them from above.

[0049] Here, "cotton-like bamboo fiber" refers to cotton-like bamboo fiber produced by crushing raw bamboo with a twin-screw crusher until the cell wall is split open, and then cutting it with a cutter blade at the outlet of the twin-screw crusher. Thinned bamboo forests can be used as raw bamboo. Figure 4 shows (a) the raw material for cotton-like bamboo fiber, (b) the manufacturing process of cotton-like bamboo fiber, and (c) a photograph of the appearance of cotton-like bamboo fiber. Figure 5 also shows an electron microscope photograph of the cotton-like bamboo fiber used in the present invention. As shown in Figure 5, the cotton-like bamboo fiber is in a state in which each bamboo fiber is disintegrated and the cell wall of the bamboo fiber is split open. When this cotton-like bamboo fiber is scattered in nature, nitrogen-fixing bacteria grow in the cell wall of the bamboo fiber, and nitrogen in the air and water is fixed inside the cotton-like bamboo fiber (see JP 2010-070963 A). As shown in Figure 4(c), cotton-like bamboo fiber is in a state where bamboo fibers are entangled like cotton, contains many gaps inside, and has a large angle of repose. Therefore, when cotton-like bamboo fiber is sprinkled from the upper opening end into the box chamber 2a of the structure molding formwork 1, the cotton-like bamboo fiber is deposited so as to fill the concave grooves 5c of the terrace portion 5b of the inner side wall surface 5 of the box chamber 2a, and is also deposited on the inner bottom surface 4 of the box chamber 2a. In this way, the cotton-like bamboo fiber is laid on the bottom and sides of the box chamber 2a.

[0050] Next, in step (S3), coarse aggregate is poured into the box chamber 2a of the structure forming formwork 1 from the upward opening end thereof to pack it into the box chamber 2a. "Coarse aggregate" refers to aggregate with a large particle size, and includes coarse aggregates used in normal concrete such as gravel, stone blocks, and coarse clinker, as well as coarse waste with a calcium skeleton from the fishing and livestock industries, such as shells, oyster shells, sea urchin shells, fish bones, and animal bones. In addition to the coarse aggregate, for example, inclusions such as fishing waste, such as fishing nets, wires, and crushed fiber-reinforced plastics, may be poured. Here, "inclusions" refers to objects to be enclosed inside the submerged structure.

[0051] Next, in step (S4), coarse aggregate is added. Structure forming frameFrom the upward opening end of the box chamber 2a of 1, mortar made by adding water or seawater to a mixture of fine aggregate and cement is injected and filled into the inside of the box chamber 2a. Fine aggregates used in normal cement mortars, such as sand and fly ash, are used as fine aggregates. In addition to normal Portland cement, magnesia cement can also be used as cement. When magnesia cement is used, a small amount of phosphate or ferrous sulfate can be used as an admixture to improve the water resistance of the cement and to provide a source of phosphorus and iron, which are essential nutrients for aquatic plants. The mortar injected into the box chamber 2a fills the gaps in the coarse aggregate 7 and also penetrates and fills the spaces between the fibers of the cotton-like bamboo fiber 6. As a result, the cotton-like bamboo fiber 6 deposited in the groove 5c and the inner bottom surface 4 is buried in the mortar, and the cotton-like bamboo fiber 6 also functions as a filler.

[0052] Next, in step (S5), the mortar filled in the box chamber 2a is cured for a period of time to allow it to sufficiently set and harden, and then the contents thereof, the submerged structure 10, is removed from the box chamber 2a of the structure forming formwork 1. The underwater structure 10 has the upper open end side of the box chamber 2a as its lower surface and the inner bottom surface 4 side of the box chamber 2a as its upper surface.

[0053] Fig. 6 shows (a) an external perspective view and (b) a cross-sectional perspective view of the submersible structure 10 to be manufactured. The cross section in Fig. 6(b) is a cross section cut along a vertical plane that passes through the central axis of the submersible structure 10 and is parallel to the front and rear sides of the bottom surface of the submersible structure 10. The submersible structure 10 to be manufactured has a configuration in which a stepped portion 10b having a multiple-step structure is formed in an annular shape on the inclined side surface of a quadrangular pyramidal base 10a (see Fig. 3(S5) and Fig. 6(b)). The upper surface portion 10c and the lower surface portion 10g of the base 10a are flat surfaces that are quadrangular in plan view. As shown in the partially enlarged view of FIG. 6(b), each step of the step portion 10b formed in a ring shape on the four inclined side surfaces of the base body 10a is composed of a vertically rising cliff portion 10d and a horizontal terrace portion 10e, and a V-shaped cross section of the concave groove 10f is formed on the inside of the terrace portion 10e. The concave groove 10f is formed in a V-shaped groove shape with an outer portion 10f-2 (outer groove side surface) and an inner portion 10f-3 (inner groove side surface) rising from a groove bottom portion 10f-1, which is a bending curve, toward the outside and inside of the base body 10a. The inner portion 10f-3 on the inside is a vertical surface that rises vertically when the base body 10a is placed with the lower surface portion 10g of the base body 10a horizontal, and is flush with the cliff portion 10d. The outer portion 10f-2 on the outside is formed so that the cross section is a curved arc shape toward the outside of the base body 10a. The upper edge of the outer portion 10f-2 of the groove 10f is located inside the outer edge of the terrace portion 10e, and a horizontal terrace flat portion 10e-1 is formed between the upper edge of the groove 10f and the outer edge of the terrace portion 5b.

[0054] The portion of the base 10a of the underwater structure 10 other than the upper surface 10c (the portion shown as region B in FIG. 6(b)) is configured such that the gaps between the coarse aggregate 7 are filled with mortar 8. The upper surface 10c and step portion 10b of the base 10a (the portion shown as region A (the region with a dotted line hatch (dotted line) downward to the left) in FIG. 6(b)) are configured such that the gaps between the cotton-like bamboo fibers 6 are filled with mortar 8, and the cotton-like bamboo fibers 6 are exposed on the surface. Hereinafter, region A will be referred to as the "cotton-like bamboo fiber-containing portion," and region B will be referred to as the "cotton-like bamboo fiber-free portion." Therefore, when the underwater structure 10 is installed on the bottom of the ocean or a lake, the cotton-like bamboo fibers 6 exposed on the surface of the upper surface 10c and step portion 10b of the base 10a will induce nitrogen fixing bacteria in the water, thereby fixing nitrogen. This makes it easier for aquatic plants to grow on the surfaces of the upper surface portion 10c and the stepped portion 10b of the base body 10a.

[0055] In addition, by making the side of the submersible structure 10 into a stepped structure having the grooves 10f, the surface area of ​​the submersible structure 10 exposed to the water is increased, which further promotes the induction of nitrogen-fixing bacteria in the water. The grooves 10f also attract polychaetes such as lugworms, and bottom-dwelling organisms such as crabs, sea urchins, and turban shells, improving the function of the structure as a fish reef. In addition, the seeds and spores of aquatic plants are easily trapped in the grooves 10f, which makes it easier for aquatic plants to attach to the structure.

[0056] In addition, if the underwater submerged structure 10 is installed on the bottom of the ocean or lake for several years, the part containing the cotton-like bamboo fiber 6 will gradually peel off or be scraped off, and the cotton-like bamboo fiber-containing part A will gradually decrease. However, since the peeled off or scraped off bamboo fiber is a natural material, unlike microplastics, it is harmless even if it is dispersed in the water. In addition, although the strength of the cement generally decreases when there is a lot of organic matter inside the cement, the part containing the cotton-like bamboo fiber 6 in the underwater submerged structure 10 is limited to the upper surface part 10c and the step part 10b of the base 10a (the part shown as region A in Figure 6 (b) (cotton-like bamboo fiber-containing part)), the strength of the part other than the upper surface part 10c of the base 10a (the part shown as region B in Figure 6 (b) (cotton-like bamboo fiber-free part)) is maintained for a long period of time. This prevents the base 10a from being destroyed, causing the underwater structure 10 to be washed away, and prevents the coarse aggregate 7 and other enclosed materials enclosed within the base 10a from being scattered underwater or into the water bottom.

[0057] Figure 7 is a photograph of the surface appearance of a specimen of the underwater submerged structure of Example 1. The specimen in Figure 7 is a test specimen for investigating the state of exposure of cotton-like bamboo fibers on the surface after cement mortar is injected and hardened, and the test formwork is not the one shown in Figures 1 and 2, but a small plastic formwork with an internal space in the shape of a truncated cone is used. The size of the test formwork is 120 mm in height, with an upper end (open end) inner diameter of 90 mmφ and a lower end inner diameter of 50 mmφ. The specimen was created using the following procedure.

[0058] (1) First, lay cotton-like bamboo fibers about 12 mm thick on the inside bottom of the test formwork. (2) Next, oyster shells as coarse aggregate are poured into the upper open end of the test formwork until it is full to the top of the test formwork. (3) Next, mortar made by adding water to a mixture of fine aggregate and cement is poured into the upper open end of the test form into which the coarse aggregate has been poured, filling the inside of the test form with mortar to create a test specimen. Here, the components of the mortar used in the test, other than water, are as follows: Sand (fine aggregate) 80wt% Magnesium oxide (MgO) 15wt% Anhydrous magnesium chloride (MgCl2) 3wt% Sodium chloride (NaCl) 2wt% To prepare mortar, 0.2 parts by weight of water is added to 1 part by weight of the mixture of the above ingredients and kneaded. Note that the cement binder made by mixing magnesium oxide (MgO) with magnesium chloride (MgCl2) is known as magnesium oxychloride cement (MOC). (4) Finally, the specimen is left in the air at room temperature for 24 hours to set and harden, then it is removed from the test form and left upside down outside for a week to harden further. Finally, it is washed with water to complete the specimen.

[0059] Figure 7(a) is an external photograph of the test specimen taken with the side containing cotton-like bamboo fiber (i.e., the side that corresponds to the inner bottom of the test formwork) facing up, and Figure 7(b) is an external photograph taken with the side not containing cotton-like bamboo fiber (i.e., the side that corresponds to the opening of the test formwork) facing up. Figures 7(c), (d), and (e) are enlarged photographs of the surface of the cotton-like bamboo fiber-containing part. Figures 7(a), (c), (d), and (e) show that the cotton-like bamboo fibers are exposed in a whisker-like form on the surface of the cotton-like bamboo fiber-containing part of the test specimen, and that the cement binder has sufficiently penetrated into the cotton-like bamboo fibers, and that the cotton-like bamboo fibers are sufficiently solidified by the cement binder, so that they do not easily peel off.

[0060] In addition, rather than later spraying the cotton-like bamboo fiber together with the cement binder onto the surface of the underwater submerged structure, the cotton-like bamboo fiber is placed inside the formwork from the beginning and the cement binder is poured in and hardened.As can be seen from the photographs in Figures 7(a) and (b), the cotton-like bamboo fiber-containing parts and the non-cotton-like bamboo fiber-containing parts are firmly bonded together by the cement binder, and the cotton-like bamboo fiber-containing parts will not easily peel off even if exposed to the effects of waves and water currents underwater.

[0061] By appropriately increasing the number of steps on the inner side wall surface 5 of the box chamber 2a of the structure forming formwork 1, more cotton-like bamboo fibers 6 can be easily trapped by the inner side wall surface 5, and the amount of cotton-like bamboo fibers 6 in the step portion 10b of the underwater submerged structure 10 can be increased, thereby improving the nitrogen fixation effect. Figure 8 shows an external perspective view of the structure forming formwork 1 when the number of steps of the step portion 5a of the inner side wall surface 5 is set to 12, and an external perspective view of the underwater submerged structure 10 manufactured by using it. When cotton-like bamboo fibers 6 are scattered from the top of the box chamber 2a of the structure molding formwork 1, the cotton-like bamboo fibers 6 are mainly trapped in the concave grooves 5c on the inner side wall surface 5 of the box chamber 2a. Therefore, by increasing the number of steps on the inner side wall surface 5 and increasing the number of concave grooves 5c, more cotton-like bamboo fibers 6 will be easily trapped on the inner side wall surface 5. However, if the number of steps is increased too much, the width of the concave grooves 5c will become too narrow, making it difficult to trap the cotton-like bamboo fibers 6, so it is necessary to set an appropriate number of steps so that the cotton-like bamboo fibers 6 are best trapped on the inner side wall surface 5. EXAMPLES

[0062] In the second embodiment, the shape of the underwater submerged structure 10 is a truncated cone. The manufacturing method of the underwater submerged structure 10 is the same as that of the first embodiment except for the shape of the structure forming formwork 1. FIG. 9 shows a perspective view of the structure forming formwork 1 used for manufacturing the underwater submerged structure 10 of the second embodiment, as viewed from the front upper left (a) and the front lower right (b). FIG. 10 shows a plan view of the structure forming formwork 1 of FIG. 9, a cross-sectional view of the structure forming formwork 1, and enlarged cross-sectional views of the structure forming formwork 1 of FIG. 9 (a), (b) and (c) and (d). The cross-sectional view of FIG. 10 (b) shows a cross-sectional view cut along a vertical plane passing through the central axis (axis of rotational symmetry) of the structure forming formwork 1. In FIG. 9 and FIG. 10, the same reference numerals are used for the components corresponding to those of FIG. 1 and FIG. 2 of the first embodiment.

[0063] Figure 11 shows (a) an external perspective view and (b) a cross-sectional perspective view of the underwater submerged structure 10 of Example 2, which is manufactured using the structure molding formwork 1 of Figures 9 and 10. The cross-sectional view of Figure 11(b) shows a cross-sectional view cut along a vertical plane passing through the central axis (axis of rotational symmetry) of the underwater submerged structure 10. In Figure 11, components corresponding to those in Figure 6 of Example 1 are given the same reference numerals. In Figure 11(b), region A is the part containing cotton-like bamboo fiber, and region B is the part not containing cotton-like bamboo fiber.

[0064] By configuring the underwater submerged structure 10 in this manner as a truncated cone shape, when it is installed on the bottom of the water, the resistance to the water flow is smaller than in the case of Example 1, and the underwater submerged structure 10 is less likely to tip over or be swept away in the water.

[0065] In this embodiment, the number of steps on the inner side wall surface 5 of the box chamber 2a of the structure forming formwork 1 (and the number of steps on the stepped portion 10b of the underwater submerged structure 10) can be appropriately changed so that the cotton-like bamboo fibers 6 are best trapped on the inner side wall surface 5, as in Example 1. EXAMPLES

[0066] In the third embodiment, the cross-sectional shape of each step of the step portion 10b of the underwater submerged structure 10 is a sawtooth shape. The manufacturing method of the underwater submerged structure 10 is the same as that of the first embodiment except for the shape of the structure forming formwork 1. FIG. 12 shows a perspective view of the structure forming formwork 1 used for manufacturing the underwater submerged structure 10 of the third embodiment, as viewed from diagonally above the left front and as viewed from diagonally below the right front. FIG. 13 shows a plan view of the structure forming formwork 1 of FIG. 12, as viewed from an arrowed view of line AA, as viewed from an arrowed view of line BB, and as viewed from an enlarged partial cross-sectional view. In FIG. 12 and FIG. 13, the same reference numerals are used for the components corresponding to those of FIG. 1 and FIG. 2 of the first embodiment.

[0067] In the structure forming form 1 of Fig. 12 and Fig. 13, the inner side wall surface 5 of the box chamber 2a of the structure forming form 1 is formed in a stepped shape that slopes upward toward the outside. If the inner bottom surface 4 of the box chamber 2a is horizontal, this step is structured by repeating a step cliff portion 5a formed to slope vertically or outwardly upward, and a terrace portion 5b in which a V-shaped groove 5c is formed. The step cliff portion 5a and terrace portion 5b of each step are formed in a square ring shape surrounding the inner bottom surface 4 of the box chamber 2a. The step cliff portion 5a adjacent to the inner bottom surface 4 of the lowest box chamber 2a is formed to slope outwardly and upward, and the other step cliff portions 5a are formed vertically. The V-shaped groove 5c is formed in a square ring shape surrounding the inner bottom surface 4 of the box chamber 2a. The cross section of the groove 5c is structured such that the outer portion 5c-2 rises vertically from the bottom of the groove, and the inner portion 5c-3 slopes upward from the bottom of the groove toward the inside. The outer portion 5c-2 of the groove 5c is smoothly connected to the cliff portion 5a without creating a step. Therefore, the cross section of the cliff portion 5a is sawtooth-shaped as a whole.

[0068] Figure 14 shows (a) an external perspective view and (b) a cross-sectional perspective view of the underwater submerged structure 10 of Example 3, which is manufactured using the structure molding formwork 1 of Figures 12 and 13. The cross-sectional view of Figure 14(b) shows a cross-sectional view cut by a vertical plane passing through the central axis of the underwater submerged structure 10 and parallel to the front and rear sides of the rectangular lower surface portion 10g of the underwater submerged structure 10. In Figure 14, components corresponding to each component of Figure 6 of Example 1 are given the same reference numerals. In Figure 14(b), region A is the part containing cotton-like bamboo fiber, and region B is the part not containing cotton-like bamboo fiber.

[0069] In this way, by forming the inner side wall surface 5 of the box chamber 2a of the structure forming formwork 1 in a sawtooth shape, the step portion 10b formed on the four inclined side surfaces of the base body 10a of the manufactured underwater submerged structure 10 becomes sawtooth. Cotton-like bamboo fibers 6 are contained in the sawtooth step portion 10b and in region A of the surface layer portion of the upper surface portion 10c (region with dotted line hatch (dotted fluff (hair)) pointing downward to the right in Figure 14 (b)), and cotton-like bamboo fibers 6 are not contained in the other portion of region B of the base body 10a.

[0070] Even with this configuration, similar effects to those of Example 1 can be obtained, such as the induction of nitrogen-fixing bacteria in the water on the surfaces of the upper surface 10c and the stepped portion 10b of the base 10a, thereby carrying out nitrogen fixation, and facilitating the attachment and growth of aquatic plants.

[0071] In this embodiment, the number of steps on the inner side wall surface 5 of the box chamber 2a of the structure forming formwork 1 (and the number of steps on the step portion 10b of the underwater submerged structure 10) can be appropriately changed, as in the first embodiment, so that the cotton-like bamboo fibers 6 are best trapped on the inner side wall surface 5. In addition, the planar shape of the box chamber 2a (and the underwater submerged structure 10) is not limited to a square, but can be appropriately changed to a rectangle, polygon, circle, ellipse, etc., depending on the application and required size. EXAMPLES

[0072] In the fourth embodiment, the cross-sectional shape of the concave groove 5c of each step of the step portion 10b of the underwater submerged structure 10 is a U-shaped groove shape with the inner side surface folded so that the upper part is expanded. The manufacturing method of the underwater submerged structure 10 is the same as that of the first embodiment except for the shape of the structure forming formwork 1. FIG. 15 is a perspective view of the structure forming formwork 1 used for manufacturing the underwater submerged structure 10 of the fourth embodiment, viewed from the left front diagonally upward and viewed from the right front diagonally downward. FIG. 16 is a plan view of the structure forming formwork 1 of FIG. 15, a cross-sectional view of the AA line arrow, a cross-sectional view of the BB line arrow, and a partially enlarged cross-sectional view of the same. In FIG. 15 and FIG. 16, the same reference numerals are attached to the components corresponding to those of FIG. 1 and FIG. 2 of the first embodiment.

[0073] In the structure forming form 1 of Fig. 15 and Fig. 16, the inner side wall surface 5 of the box chamber 2a of the structure forming form 1 is formed in a stepped shape inclined upward toward the outside. If the inner bottom surface 4 of the box chamber 2a is horizontal, this step is structured by repeating a step cliff portion 5a formed to be inclined vertically or outwardly upward, and a terrace portion 5b in which a concave groove 5c of a U-shaped groove is formed. The step cliff portion 5a and the terrace portion 5b of each step are formed in a square ring shape surrounding the inner bottom surface 4 of the box chamber 2a. The step cliff portion 5a adjacent to the inner bottom surface 4 of the lowermost box chamber 2a is formed to be inclined outwardly and upward, and the other step cliff portions 5a are formed vertically. The concave groove 5c of the U-shaped groove is formed in a square ring shape surrounding the inner bottom surface 4 of the box chamber 2a. The cross section of the groove 5c is structured such that an outer portion 5c-2 rises vertically from the outer end of the horizontally flat groove bottom 5c-1, and an inner portion 5c-3 rises vertically from the inner end of the groove bottom 5c-1, and is bent near the center of the inner portion 5c-3 and inclined upward toward the inside. The outer portion 5c-2 of the groove 5c is smoothly and continuously connected to the cliff portion 5a without creating a step.

[0074] Figure 17 shows (a) an external perspective view and (b) a cross-sectional perspective view of the underwater submerged structure 10 of Example 4, which is manufactured using the structure molding formwork 1 of Figures 15 and 16. The cross-sectional view of Figure 17(b) shows a cross-sectional view cut by a vertical plane passing through the central axis of the underwater submerged structure 10 and parallel to the front and rear sides of the rectangular lower surface portion 10g of the underwater submerged structure 10. In Figure 17, components corresponding to those in Figure 6 of Example 1 are given the same reference numerals. In Figure 17(b), region A is the portion containing cotton-like bamboo fiber, and region B is the portion not containing cotton-like bamboo fiber.

[0075] In this way, the cross-sectional shape of the concave groove 5c of each step of the step of the inner side wall surface 5 of the box chamber 2a of the structure forming formwork 1 is U-shaped groove with the inner side surface folded so that the upper part is expanded, so that the cross-section of the terrace portion 10e of each step of the step portion 10b formed on the four inclined side surfaces of the base 10a of the manufactured underwater submerged structure 10 has a structure in which, when the lower surface portion 10g of the underwater submerged structure 10 is horizontal, the outer side is a horizontal flat surface, and the part that contacts the inner step cliff portion 10d has a concave groove 10f that surrounds the central axis of the underwater submerged structure 10. The inner groove side wall of the concave groove 10f is vertical and is smoothly and continuously connected to the step cliff portion 10d without generating a step. The outer groove side wall of the concave groove 10f has a structure in which the upper part is vertical and the lower part is inclined downward toward the inside, and the groove bottom of the concave groove 10f is V-shaped. Cotton-like bamboo fibers 6 are contained in such step portions 10b and in region A of the surface portion of the upper surface portion 10c (the region indicated by a dotted hatch (dotted fuzz) pointing downward to the right in Figure 14(b)), while cotton-like bamboo fibers 6 are not contained in the other portions of region B of the base body 10a.

[0076] Even with this configuration, similar effects to those of Example 1 can be obtained, such as the induction of nitrogen-fixing bacteria in the water on the surfaces of the upper surface 10c and the stepped portion 10b of the base 10a, thereby carrying out nitrogen fixation, and facilitating the attachment and growth of aquatic plants.

[0077] In this embodiment, the number of steps on the inner side wall surface 5 of the box chamber 2a of the structure forming formwork 1 (and the number of steps on the step portion 10b of the underwater submerged structure 10) can be appropriately changed, as in the first embodiment, so that the cotton-like bamboo fibers 6 are best trapped on the inner side wall surface 5. In addition, the planar shape of the box chamber 2a (and the underwater submerged structure 10) is not limited to a square, but can be appropriately changed to a rectangle, polygon, circle, ellipse, etc., depending on the application and required size. EXAMPLES

[0078] In the fifth embodiment, a sand and mud discharge groove is provided in the step portion 10b of the inclined side surface of the base 10a of the submerged structure 10. The manufacturing method of the submerged structure 10 is the same as that of the first embodiment except for the shape of the structure forming formwork 1. FIG. 18 shows a perspective view of the structure forming formwork 1 used for manufacturing the submerged structure 10 of the fifth embodiment, as viewed from the upper left front and as viewed from the lower right front. FIG. 19 shows a plan view of the structure forming formwork 1 of FIG. 18, as viewed from the arrow AA, as viewed from the arrow BB, and as viewed from the arrow CC. In FIG. 18 and FIG. 19, the same reference numerals are used for the components corresponding to those of FIG. 1 and FIG. 2 of the first embodiment.

[0079] The structure forming formwork 1 of this embodiment has a similar configuration to the structure forming formwork 1 shown in FIG. 8(a) of the first embodiment, except that three convex stripes 14, 14, 14 are provided at intervals on each of the four inner side wall surfaces 5 of the box chamber 2a of the formwork main body 2 from the upper inclined portion to the lower inclined portion of the inner side wall surface 5. Each convex stripe 14 is perpendicular to the upper and lower sides of the inner side wall surface 5 on which the convex stripe 14 is located. The central convex stripe 14 of each inner side wall surface 5 is provided along the center line of the inner side wall surface 5 on which the convex stripe 14 is located (the straight line connecting the midpoint of the upper side and the midpoint of the lower side). The left and right convex stripes 14 are parallel to the center line of the inner side wall surface 5 on which the convex stripe 14 is located, and the left convex stripe 14 and the right convex stripe 14 are provided in positions that are symmetrical with respect to the center line. The cross-sectional shape of the convex rib portion 14 cut along a plane perpendicular to the stripes of the convex rib portion 14 is a square shape (bottomless rectangle), and the upper surface of the convex rib portion 14 is located at a position lower than the upper edge (terrace portion (see FIG. 19(c-1))) of the concave groove 5c provided in the terrace portion 5b of each step of the inner side wall surface 5. Therefore, the convex rib portion 14 of each strip is submerged inside the concave groove 5c, and is buried and interrupted in the inner side wall surface 5 in the portions other than the concave groove 5c, and is configured as an interrupted ridge overall (see FIG. 19).

[0080] Figure 20 shows (a) an external perspective view and (b) a cross-sectional perspective view of the underwater submerged structure 10 of Example 5, which is manufactured using the structure molding formwork 1 of Figures 18 and 19. The cross-sectional view of Figure 20(b) shows a cross-sectional view cut by a vertical plane passing through the central axis of the underwater submerged structure 10 and parallel to the front and rear sides of the rectangular lower surface portion 10g of the underwater submerged structure 10. In Figure 20, components corresponding to each component of Figure 6 of Example 1 are given the same reference numerals. In Figure 20(b), region A is the part containing cotton-like bamboo fiber, and region B is the part not containing cotton-like bamboo fiber.

[0081] The underwater submerged structure 10 of this embodiment has a similar structure to the underwater submerged structure 10 shown in Fig. 8(b) of the first embodiment, except that three sand and mud discharge grooves 15, 15, 15 are formed on each of the four inclined side surfaces of the base 10a. By providing three convex stripes 14, 14, 14 on each of the four inner side wall surfaces 5 of the box chamber 2a of the structure forming formwork 1 in Figs. 18 and 19, three sand and mud discharge grooves 15, 15, 15 are formed on each inclined side surface of the manufactured underwater submerged structure 10, and the concave stripe grooves 10f formed on each step of the step portion 10b of the inclined side surface open outward and obliquely downward at the portion of the sand and mud discharge grooves 15. As a result, when the underwater structure 10 is submerged in the bottom of the ocean, lakes, and other bodies of water, the sand and mud that enters each groove 10f is discharged from the groove 10f through the sand and mud discharge groove 15, making it difficult for sand and mud to accumulate inside each groove 10f. This prevents the surface area of ​​the surface of the underwater structure 10, which contains the cotton-like bamboo fibers 6, from decreasing due to the accumulation of sand and mud, making it possible to more effectively fix nitrogen by nitrogen-fixing bacteria.

[0082] In this embodiment, the number of steps on the inner side wall surface 5 of the box chamber 2a of the structure forming formwork 1 (and the number of steps on the step portion 10b of the underwater submerged structure 10) can be appropriately changed, as in the first embodiment, so that the cotton-like bamboo fibers 6 are best trapped on the inner side wall surface 5. In addition, the planar shape of the box chamber 2a (and the underwater submerged structure 10) is not limited to a square, but can be appropriately changed to a rectangle, polygon, circle, ellipse, etc., depending on the application and required size. EXAMPLES

[0083] In the sixth embodiment, the cross-sectional shape of the concave groove 5c of each step of the step portion 10b of the underwater submerged structure 10 is a U-shaped groove shape in which the outer side surface is curved (bent outward) so as to expand at the top, and the inner side surface is inclined inward so as to expand at the top, and the cliff portion 10d of each step is an inclined surface inclined inward. The manufacturing method of the underwater submerged structure 10 is the same as that of the first embodiment except for the shape of the structure-forming formwork 1. Figure 21 is a perspective view of the structure-forming formwork 1 used to manufacture the underwater submerged structure 10 of the sixth embodiment, viewed from an obliquely upper left front and viewed from an obliquely lower right front. Figure 22 is a plan view of the structure-forming formwork 1 of Figure 21, viewed from an arrowed view of the line AA (line BB) in (a), and viewed from an enlarged partial cross-sectional view in (c). 21 and 22, components corresponding to those in FIGS. 1 and 2 of the first embodiment are denoted by the same reference numerals.

[0084] The structure forming formwork 1 of this embodiment is basically the same as that of the first embodiment, but the structure of the step cliff portion 5a and the terrace portion 5b of the inner side wall surface 5 is different. In this embodiment, when the inner bottom surface 4 is horizontal and the formwork main body 2 is placed, the step cliff portion 5a is not vertical but is configured to be inclined upward toward the outside. Also, the concave groove 5c of the terrace portion 5b is a U-shaped groove in which the outer portion 5c-2 and the inner portion 5c-3 are bent and raised from the outside and inside of the groove bottom portion 5c-1, respectively, but the groove side surface of the outer portion 5c-2 is configured to be inclined upward toward the outside instead of vertical when the formwork main body 2 is placed with the inner bottom surface 4 horizontal, and is flush with the step cliff portion 5a. Furthermore, as in Example 1, the groove side surface of the inner portion 5c-3 is formed so that when the formwork body 2 is placed with the inner bottom surface 4 horizontal, it rises vertically from the groove bottom portion 5c-1 and curves inward, but the upper edge of the inner portion 5c-3 is located outside the inner edge of the terrace portion 5b, and a horizontal terrace flat portion 5b-1 is formed between the upper edge of the concave groove 5c and the inner edge of the terrace portion 5b.

[0085] Figure 23 shows (a) an external perspective view, (b) a cross-sectional perspective view, and (c) a partially enlarged cross-sectional view of the underwater submerged structure 10 of Example 6, which is manufactured using the structure molding formwork 1 of Figures 21 and 22. The cross-sectional view of Figure 23(b) shows a cross-sectional view cut by a vertical plane passing through the central axis of the underwater submerged structure 10 and parallel to the front and rear sides of the rectangular lower surface portion 10g of the underwater submerged structure 10. In Figure 23, components corresponding to each component of Figure 6 of Example 1 are given the same reference numerals. In Figure 23(b), region A is the part containing cotton-like bamboo fiber, and region B is the part not containing cotton-like bamboo fiber.

[0086] The underwater submerged structure 10 of this embodiment is basically the same as that of the first embodiment, but the structures of the cliff portion 10d and the terrace portion 10e of the step portion 10b are different. In this embodiment, when the base body 10a is placed with the lower surface portion 10g horizontal, the cliff portion 10d is not vertical, but is configured to incline upward toward the inside. In addition, the concave groove 10f of the terrace portion 10e is V-shaped in the first embodiment, whereas in this embodiment, the outer portion 10f-2 (outer groove side surface) and the inner portion 10f-3 (inner groove side surface) are bent and raised from the outer side and inner side of the groove bottom portion 10f-1 (groove bottom surface), which is a flat surface, to form a U-shaped groove. Furthermore, when the base 10a is placed with the lower surface 10g of the base 10a horizontal, the groove side of the inner portion 10f-3 of the groove 10f is not vertical, but is configured to be inclined upward toward the inside and is flush with the cliff portion 10d. Also, the groove side of the outer portion 10f-2 of the groove 10f is formed so that the cross-sectional shape is an arc curved toward the outside of the base 10a, as in Example 1. The upper edge of the outer portion 10f-2 of the groove 10f is located inside the outer edge of the terrace portion 10e, and a horizontal terrace flat portion 10e-1 is formed between the upper edge of the groove 10f and the outer edge of the terrace portion 5b.

[0087] In this way, by making the grooves 10f formed in each terrace portion 10e of the step portion 10b of the underwater submerged structure 10 into a U-shaped groove, water circulation near the bottom of the grooves 10f is facilitated, improving the nitrogen fixation effect of the nitrogen fixing bacteria.

[0088] In this embodiment, the number of steps on the inner side wall surface 5 of the box chamber 2a of the structure forming formwork 1 (and the number of steps on the step portion 10b of the underwater submerged structure 10) can be appropriately changed, as in the first embodiment, so that the cotton-like bamboo fibers 6 are best trapped on the inner side wall surface 5. In addition, the planar shape of the box chamber 2a (and the underwater submerged structure 10) is not limited to a square, but can be appropriately changed to a rectangle, polygon, circle, ellipse, etc., depending on the application and required size. EXAMPLES

[0089] In the seventh embodiment, the step portion 10b of the underwater structure 10 is formed continuously in a spiral shape on the inclined side surface from the top 10c to the bottom 10g of the base 10a. The manufacturing method of the underwater structure 10 is the same as that of the first embodiment except for the shape of the structure forming formwork 1. FIG. 24 shows a perspective view of the structure forming formwork 1 used for manufacturing the underwater structure 10 of the seventh embodiment, as viewed from the upper left front and as viewed from the lower right front. FIG. 25 shows a plan view of the structure forming formwork 1 of FIG. 24, a cross-sectional view of the AA line arrow and an enlarged cross-sectional view of the same part. In FIG. 24 and FIG. 25, the same reference numerals are used for the components corresponding to those of FIG. 1 and FIG. 2 of the first embodiment.

[0090] The structure forming formwork 1 of this embodiment differs from Example 1 in that the internal space of the box chamber 2a is formed in a truncated cone shape, and the step formed on the internal side wall surface 5 is formed along a continuous spiral line from the open end of the box chamber 2a to the edge of the internal bottom surface 4. Another difference from Example 1 is that the cliff portion 5a rises vertically from the terrace portion 5b and is formed in a folded surface shape that bends so as to incline outward near the center.

[0091] Figure 26 shows (a) an external perspective view and (b) a cross-sectional view of the underwater submerged structure 10 of Example 7, which is manufactured using the structure molding formwork 1 of Figures 24 and 25. The cross-sectional view of Figure 26(b) shows a cross-sectional view cut along a vertical plane that passes through the central axis of the underwater submerged structure 10 and is perpendicular to the underside 10g of the underwater submerged structure 10. In Figure 26, components corresponding to those in Figure 6 of Example 1 are given the same reference numerals. In Figure 26(b), region A is the part containing cotton-like bamboo fiber, and region B is the part not containing cotton-like bamboo fiber.

[0092] The underwater submerged structure 10 of this embodiment is different from that of the first embodiment in that the overall shape is formed in a truncated cone shape, and the cliff portion 10d and the terrace portion 10e of the step portion 10b on the inclined side surface of the base 10a are formed along a continuous spiral from the edge of the top portion 10c to the edge of the lower surface portion 10g. The terrace portion 10e is also different from that of the first embodiment in that the terrace portion 10e is formed by a substantially horizontal and flat terrace flat portion 10e-1 and a groove groove 10f formed in a groove shape inside the terrace flat portion 10e. As a result, the groove groove 10f formed in the terrace portion 10e is a spiral groove that continues from the upper end to the lower end of the step portion 10b on the inclined side surface of the base 10a. When the underwater submerged structure 10 is submerged in the bottom of the ocean, a lake, or a river, if sand and mud are deposited in the grooves 10f, a flow will be generated inside the grooves 10f along the spiral grooves 10f due to the influence of waves and water currents, and the sand and mud deposited in the grooves 10f will be swept downward and discharged, making it difficult for the sand and mud to accumulate in the grooves 10f. This prevents a decrease in the surface area exposed to water on the side of the base 10a caused by the deposition of sand and mud in the grooves 10f, and therefore maintains a high nitrogen fixation function by the nitrogen fixing bacteria for a long period of time. Furthermore, the improved circulation of water in the grooves 10f improves the nitrogen fixation function of the nitrogen fixing bacteria in the grooves 10f.

[0093] In this embodiment, the number of steps on the inner side wall surface 5 of the box chamber 2a of the structure forming formwork 1 (and the number of steps on the step portion 10b of the submerged structure 10) can be appropriately changed so that the cotton-like bamboo fibers 6 are best trapped on the inner side wall surface 5, as in the first embodiment. In addition, the planar shape of the box chamber 2a (and the submerged structure 10) is preferably circular in order to effectively generate the water circulation action in the grooves 10f, but it can also be appropriately changed to a square, rectangle, polygon, ellipse, etc., depending on the application and required size. [Explanation of symbols]

[0094] 1. Structure Forming Formwork 2 Formwork body 2a Box room 3 legs 4 Internal bottom 5 Inner side wall 5a Terrace 5b Terrace section 5b-1 Terrace flat area 5c Concave groove 5c-1 Groove bottom 5c-2 Outer part 5c-3 Inside part 6 Cotton-like bamboo fiber 7 Coarse aggregate 8. Mortar 10 Submerged structures 10a Base 10b Step 10c Top part 10d Cliff section 10e Terrace section 10e-1 Terrace flat area 10f concave groove 10f-1 Groove bottom 10f-2 Outside part 10f-3 Inside part 10g bottom part 14 Convex portion 15 Sand drainage mud groove Area A Cotton-like bamboo fiber containing part Area B Cotton-like bamboo fiber-free area

Claims

1. A submerged structure for submerging on the bottom of a body of water and for growing aquatic plants on its surface, a base body formed in a frustum shape having a lower surface portion, an upper surface portion having an area smaller than that of the lower surface portion, and an inclined side surface formed from the lower surface portion to the upper surface portion and inclined upward from the lower surface portion to the upper surface portion as a whole; A step portion formed in a step shape over the entire inclined side surface of the base body, The surface layer of the upper surface of the base and the step portion are composed of a cotton-like bamboo fiber-containing portion in which cotton-like bamboo fibers, which are made by crushing raw bamboo into a cotton-like form, are coagulated and hardened using a mortar made by adding water or seawater to a mixture of fine aggregate and cement as a binder. The portion of the base other than the cotton-like bamboo fiber-containing portion is composed of a cotton-like bamboo fiber-free portion in which coarse aggregate is sealed with the mortar and set / hardened, When the bottom surface of the base is horizontal, the step portion has steps formed around the entire periphery, the steps being made up of alternating cliff portions formed in a surface structure that rises vertically or inclined toward the inside of the base and terrace portions formed in a horizontal or recessed surface structure, A groove is formed in each of the terraces along the circumferential direction of the terrace. An underwater submerged structure characterized by:

2. The structure forming frame body according to claim 1, characterized in that the cross-sectional shape of each of the concave grooves is formed into a V-shaped groove shape in which the groove width gradually increases with increasing distance from the groove bottom, and when the bottom surface of the base is horizontal, the inner groove side surface is a vertical surface or an inclined surface that slopes upward toward the inside of the base and smoothly connects to the step cliff portion without creating a step, and the outer groove side surface is a vertical surface or an inclined surface that slopes upward toward the outside of the base.

3. The structure forming frame body according to claim 1, characterized in that each of the concave grooves has a cross-sectional shape formed like a U-shaped groove having a flat groove bottom, an inner groove side surface that rises from the inner end of the groove bottom, inclining vertically or upward toward the inside of the base when the bottom surface of the base is horizontal, and an outer groove side surface that rises from the outer end of the groove bottom, inclining vertically or upward toward the outside of the base, and that the inner groove side surface is smoothly and continuously connected to the cliff portion without creating a step.

4. An underwater submerged structure as described in any one of claims 1 to 3, characterized in that a sand and mud discharge groove is formed on the inclined side surface of the base body from the upper part to the lower part of the slope, which is a groove that intersects with the cliff portion and the terrace portion of the step portion.

5. A method for manufacturing an underwater submerged structure for submerging on the bottom of a body of water and growing aquatic plants on its surface, comprising the steps of: A box chamber is formed, the box chamber being in the shape of a box with a frustum-shaped internal space with a smaller area at the lower bottom than at the upper bottom, the upper bottom side being fully open, and with the open end of the box chamber facing upward, the entire periphery of the internal side wall surface of the box chamber is inclined upward from the center of the box chamber toward the outside, and a step structure is formed along the entire periphery of the internal wall side surface, in which a cliff portion formed in a planar structure that rises vertically or inclined upward from the center of the box chamber toward the outside, and a terrace portion formed in a concave planar structure are alternately repeated, and a structure forming frame having a groove formed along the circumferential direction of each terrace portion is installed so that the open end of the box chamber faces upward, A first step of laying cotton-like bamboo fibers obtained by crushing raw bamboo into a cotton-like state so as to cover at least the concave portions of the concave and convex portions formed on the inner side wall surface of the box chamber of the structure forming frame body and the inner bottom surface of the box chamber; a second step of pouring coarse aggregate into the box chamber from an upward opening end of the box chamber of the structure forming frame body to pack the box chamber therein; a third step of pouring mortar, which is made by adding water or seawater to a mixture of fine aggregate and cement, into the upward opening end of the box chamber of the structure forming frame into which the coarse aggregate has been poured, and filling the inside of the box chamber of the structure forming frame; A method for manufacturing an underwater submerged structure comprising:

6. A manufacturing method for an underwater submerged structure as described in claim 5, characterized in that within the groove of the concave groove provided in each terrace portion of the inner side wall surface of the box chamber of the structure forming frame used in the first step, a plurality of convex ridge portions configured as interrupted ridges are provided at intervals along a straight line that intersects across each cliff portion and each terrace portion from the upper sloping top to the lower sloping bottom of the inner side wall surface of the box chamber.

7. A structure forming form used in the manufacturing method of the underwater submerged structure according to claim 5, A box-shaped chamber is formed, the lower surface of which has a small area compared to the upper surface, and the upper surface side is entirely open, When the open end of the chamber is the top, the entire circumference of the inner side wall surface of the chamber is inclined upward from the center of the chamber toward the outside, In addition, a step structure is formed in which a cliff portion formed in a plane structure that rises vertically or inclined upward from the center of the box chamber toward the outside and a terrace portion formed in a concave plane structure are alternately repeated around the entire circumference of the inner wall side surface, A formwork for forming a structure, characterized in that each of the terrace portions has a concave groove formed along a circumferential direction of the terrace portion.

8. Each of the concave grooves has a cross-sectional shape formed in a V-shape such that the groove width gradually increases with increasing distance from the groove bottom, The structure forming formwork described in claim 7, characterized in that when the inner bottom surface of the box chamber is horizontal, the outer groove side surface of the concave groove is a vertical surface or an inclined surface that slopes upward toward the outside of the box chamber, which smoothly and continuously connects to the step cliff portion without creating a step, and the inner groove side surface of the concave groove is an inclined surface that slopes upward toward the inside of the box chamber.

9. Each of the concave grooves is formed into a U-shaped cross-sectional shape having a flat groove bottom, an outer groove side surface rising from the outer end of the groove bottom, either vertically or inclined upward toward the outside of the box chamber when the inner bottom surface of the box chamber is horizontal, and an inner groove side surface rising from the inner end of the groove bottom, either vertically or inclined upward toward the inside of the box chamber; 8. The formwork for forming a structure according to claim 7, wherein the outer groove side surface is smoothly and continuously connected to the cliff portion without creating a step.

10. A structural molding formwork as described in any one of claims 7 to 9, characterized in that within the groove of the concave groove provided in each of the terrace portions of the inner side wall surface of the box chamber, a plurality of convex ridge portions configured as interrupted ridges are provided at intervals along a straight line that intersects across each of the cliff portions and each of the terrace portions from the upper sloping portion to the lower sloping portion of the inner side wall surface of the box chamber.

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