JP5245241B2 - Submerged dike construction method and submerged dike - Google Patents

Description

  The present invention relates to a submerged dike construction method and a submerged dike installed for the purpose of coastal conservation and shallow ground creation.

  For the purpose of coastal conservation (prevention of coastal erosion), shallow ground creation, artificial reef, sea wave extinction, etc., a submerged dike is mainly installed at the bottom of the coastal sea area. Such a submerged dike is generally constructed by stacking rubble and concrete blocks on the bottom of the water. In some cases, a rubble foundation is installed at the bottom of the water, and concrete blocks are stacked on top of it to construct a submerged dike.

However, it is difficult to procure natural crushed stone used as rubble every year. Generally, large stones with high resistance to waves are required for offshore construction, but the procurement of such natural stones is becoming particularly difficult. Furthermore, recently, the destruction of natural stones has also become a problem. In addition, the concrete block has a problem of high cost, and further, there is a problem that the environment of the installation sea area is temporarily deteriorated because the block surface is dense and there is no gap, and thus the initial biocompatibility is inferior.
On the other hand, massive steel-making slag having a particle diameter of about 20 to 50 mm has been manufactured as civil engineering materials such as roadbed materials. Patent Document 1 describes the construction of a submerged dike using such massive steel-making slag. Has been shown to do. Steelmaking slag is slag generated in the steel manufacturing process, and has an advantage that it can be procured inexpensively and in large quantities.
JP 2002-238401 A

However, when a massive steelmaking slag having a particle size of about 20 to 50 mm is used as a submerged levee material as in Patent Document 1, the submerged levee material is washed away by a large wave or the like, and the submerged levee is greatly damaged or severe. The submarine itself collapses and disappears. That is, there is a problem that the submerged dike constructed with massive steelmaking slag has low wave stability.
Therefore, an object of the present invention is to provide a submerged dike construction method and a constructed submerged dike that can construct a robust submerged dike having high wave stability without using a large amount of natural stone at low cost. It is in.

In order to solve the above problems, the present inventors have studied from both sides of the submerged dike material to be used and the construction method, and as a result, a granular or massive Ca-containing material such as steel slag is formed on the bottom of seawater or brackish water. Building a dike structure using the main submerged dike material and forming a shell-like film mainly composed of magnesium hydroxide precipitates or magnesium hydroxide and calcium hydroxide precipitates on the surface of the dike structure In addition, the present inventors have found that a solid submerged bank having high wave stability can be constructed at low cost by covering the bank structure with this shell-shaped coating.
Furthermore, as measures to prevent the leakage of submerged levee materials until the constructed dam structure is consolidated, (1) a method of covering the levee structure with a covering for preventing spillage, and (2) A method for preventing the outflow and covering with a covering that decomposes or corrodes over time in water, and after the shell-like film is formed on the surface layer of the bank structure, the covering is naturally lost by decomposition or corrosion Was found to be preferred.

The present invention has been made on the basis of the findings as described above, and has the following gist.
[1] By laminating a submerged dike material on the bottom of seawater or brackish water area, at least the outer layer part contains submerged dike material A containing 50 mass% or more of granular or / and massive Ca-containing material (however, granular or / and massive Ca (Including the case of a submerged levee material consisting only of inclusions), and the surface layer of the levee structure is mainly composed of magnesium hydroxide precipitates or magnesium hydroxide and calcium hydroxide precipitates. a method of applying Sentsutsumi that Ru to produce a shell-like coating,
The submerged dike material A contains 40 mass% or more of steelmaking slag having a particle size of 2 mm or less .
[2] Submerged levee material A (however, granular or / and massive Ca containing at least 50 mass% of granular or / and massive Ca-containing material in the outer layer by stacking the latent dam material on the bottom of seawater or brackish water) (Including the case of a submerged levee material consisting only of inclusions), and the surface layer of the levee structure is mainly composed of magnesium hydroxide precipitates or magnesium hydroxide and calcium hydroxide precipitates. It is a construction method of a submerged dike that generates a shell film.
The submerged dike material A contains 20 mass% or more of granulated blast furnace slag having a particle size of 1 mm or less.
[3] A construction method for a submerged dike characterized in that in the construction method of [1] or [2] , the granular or / and massive Ca-containing material is slag generated in a steel production process.

[4] [1] to [3] construction methods of Sentsutsumi, characterized in that in any one of the construction methods, the average thickness of the surface layer in the resulting shell-like coating of the bank structure is 0.5mm or more .
[5] The construction method according to any one of [1] to [4] , wherein at least a part of the constructed dyke structure is covered with a covering for preventing the loss of the submerged levee material A. How to construct a submerged dike .

[6] In the construction method according to any one of the above [1] to [6] , at least a part of the constructed bank structure is a covering for preventing the leakage of the submerged bank material A and is underwater After covering with a covering that decomposes and / or corrodes with time, and forming a shell-like film on the surface layer of the bank structure covered with the covering, at least the main part of the covering is lost by decomposition or / and corrosion. A method of constructing a submerged dike.
[7] In the construction method according to any one of [1] to [6] above, the submerged dike A is placed in a container that is water-permeable and decomposes or / and corrodes over time in water, and the containers are stacked Construction of a submerged levee characterized by constructing at least a part of the outer layer portion of the levee structure and generating a shell-like film on the surface of the submerged levee material A in the container, and then disassembling or / and corroding the container Law.
[8] A submerged levee material A (provided that the outer layer portion contains 50 mass% or more of granular or / and massive Ca-containing material, which is constructed by stacking the submerged levee material on the bottom of seawater or brackish water (particulate or / and A dike structure including a case of a submerged dike material composed only of massive Ca-containing material, and deposits of magnesium hydroxide or magnesium hydroxide and calcium hydroxide on the surface layer of the dike structure It is a submerged dike created by the main shell film ,
The submerged levee material A contains 40 mass% or more of steelmaking slag having a particle diameter of 2 mm or less .
[9] A submerged levee material A (provided that the outer layer portion contains 50 mass% or more of granular or / and massive Ca-containing material, which is constructed by stacking the submerged levee material on the bottom of seawater or brackish water. A dike structure including a case of a submerged dike material composed only of massive Ca-containing material, and deposits of magnesium hydroxide or magnesium hydroxide and calcium hydroxide on the surface layer of the dike structure It is a submerged dike created by the main shell film,
The submerged dike material A contains 20 mass% or more of granulated blast furnace slag having a particle size of 1 mm or less.

  According to the present invention, since the submerged levee material mainly composed of granular and massive Ca-containing material is used, the submerged levee can be constructed at a low cost, and the precipitate of magnesium hydroxide or the hydroxide is formed on the surface layer of the dam structure. A shell-like film composed mainly of magnesium and calcium hydroxide precipitates was generated, and the dam structure was covered with this shell-like film, so it was possible to construct a robust submerged bank with high wave stability. it can.

  Fig. 1 shows an example of installation of a submerged dike (longitudinal section). Fig. 1 (A) is a submerged dike for coastal protection (for coastal erosion prevention), and Fig. 1 (B) is a submerged dike for shallow field creation. It is a dyke. The inside (shore side) of this submerged submerged dike is generally covered with sand or a filling material and covered with sand. In addition to the above, the submerged dike is installed for various purposes such as artificial reef formation, coastal wave extinction, and water purification.

In the construction method of a submerged dike of the present invention, a dike structure is constructed by throwing submerged dike material into water from a transport ship or the like and stacking it on the bottom of the seawater or brackish water. This bank structure is composed of a submerged bank material A whose outer layer portion is mainly composed of granular or / and massive Ca-containing material (see FIG. 4 for the outer layer portion and inner layer portion of the bank structure). And a shell-like film mainly composed of magnesium hydroxide precipitates or magnesium hydroxide and calcium hydroxide precipitates is formed on the surface layer of the bank structure, and the bank structure is covered with the shell film. By doing so, high wave stability is obtained.
Examples of granular or / and massive Ca-containing materials include slag (hereinafter referred to as steel slag) generated in the steel manufacturing process, waste concrete, and the like, and one or more of these can be used.
Hereinafter, the present invention will be described by way of example in which steel slag is used as the granular and massive Ca-containing material, but the following description will be replaced with the steel slag, or together with the steel slag, other granular and massive Ca-containing materials (for example, Applicable when using waste concrete).

  A shell-like film mainly composed of magnesium hydroxide precipitates or magnesium hydroxide and calcium hydroxide precipitates is formed on the surface layer of the dike structure whose outer layer is composed of the submerged dike material A mainly composed of steel slag. The mechanism to perform is as follows. That is, steel slag contains a relatively large amount of CaO, and when such steel slag is placed in water, Ca ions are eluted and raise the pH of the water around the bank structure. The ion solubility of water changes due to this pH increase, and Mg ions in the water (seawater or brackish water) are converted into hydroxide (magnesium hydroxide) as a hydroxide (magnesium hydroxide). ) To form a relatively hard film (precipitate layer). Further, when magnesium hydroxide is precipitated in this way, floating mud, sediment (containing alumina, silicic acid, organic matter, etc.), slag particles (part of the submerged dam material A), etc. may be involved. In this case, they are also part of the shell film. Furthermore, when magnesium hydroxide is deposited in a layered manner on the surface layer of the bank structure and the seawater exchange of pore water in the bank structure is reduced, the pH of the pore water in the submerged bank material A increases, Calcium hydroxide may be deposited on the inner surface of the cavity formed in the deposited layer. In this case, the precipitate of calcium hydroxide also becomes part of the shell film. In addition to magnesium hydroxide or calcium hydroxide, a small amount of hydrate containing silicic acid or alumina may be deposited as a part of the shell film. Therefore, the shell film formed on the surface layer of the bank structure is mainly composed of magnesium hydroxide precipitates or magnesium hydroxide and calcium hydroxide precipitates generated as described above (that is, these precipitates are 50% by mass or more), and in some cases, a film containing non-precipitates of components derived from precipitates of hydrates including silicic acid and alumina, floating mud / sediment, slag particles (part of submerged dike material A), etc. is there.

  Magnesium hydroxide is first deposited between the material particles of the submerged levee material A constituting the outer layer portion of the bank structure, and then generated so as to fill the gap between the particles and finally cover the entire bank structure. A shell film is formed. FIG. 2 schematically shows a cross section of the shell-like film, where x is the shell-like film and y is the material particle of the submerged dike material A. FIG. 3 is an SEM image of a cross-section of the shell-like film formed on the surface layer of the submerged dike material A (slag) installed in seawater, and an image obtained by performing surface analysis of Mg and Ca using the SEM. In each of the surface analysis images, the portions mainly composed of Mg and the portions mainly composed of Ca are shown whitish. This shell-like film is produced in one month by placing a material obtained by mixing steelmaking slag (dephosphorization slag) and granulated blast furnace slag at a mass ratio of 7: 3 in the sea.

Since the shell-like film is composed mainly of precipitates, it is relatively dense and hard and has a certain level of strength. The bank structure covered with such a shell-like film is highly resistant to water currents such as waves. Stability is obtained.
The shell-like film may be generated so that the bank structure is covered and can be held integrally. Therefore, there is no special limitation on the thickness of the film. Since the strength against external force may be insufficient, the average thickness is preferably 0.5 mm or more. For example, as shown in FIG. 8, the average thickness t of the shell-like film is obtained by measuring a film cross-sectional area S in the thickness direction in a predetermined length range L, and [average thickness t = film cross-sectional area S / length L]. Can be sought. In general, the length L is preferably 300 mm or more.

In the construction method of the present invention, the stability of the dam structure against waves and the like is basically ensured by covering the surface layer of the dam structure with a shell film, but depending on the type and composition of the steel slag, After the formation of the film, the dam structure itself may be consolidated by the hydraulic action of the slag. That is, when a shell-like film is formed on the surface layer of the bank structure by the mechanism as described above, the seawater exchange of pore water in the outer layer portion of the bank structure disappears, so that the pH rises and SiO originates from the slag component. _{A 2-} CaO—H ₂ O gel is generated and fills the space between the material particles, so that the entire outer layer portion of the bank structure is consolidated (hydrated and cured). Such hydration hardening is likely to occur particularly when blast furnace granulated slag is included, and in addition to the formation of a shell-like film, the inside of the bank structure (at least the outer layer) is consolidated, so higher wave stability is obtained. .

As the steel slag constituting the submerged dam material A, blast furnace granulated slag, blast furnace slow-cooled slag (however, this blast furnace slow-cooled slag is preferably sufficiently aged to prevent S from eluting in water) Various slags such as steelmaking slag and ore reduction slag can be used. Steelmaking slag includes hot metal pretreatment slag such as dephosphorization slag, desulfurization slag, and desiliconization slag, decarburization slag, cast slag, electric furnace slag, and the like. As the steelmaking slag, decarburization slag and dephosphorization slag are particularly suitable.
The submerged dam material A has a granular or / and massive shape, and a particle size of about 100 mm or less is usually usable. Normally used steelmaking slag has a particle size of 85 mm or less, and blast furnace granulated slag has a particle size of 5 mm or less. However, when it is already consolidated, a particle having a larger particle size can be used.

  The submerged dam material A may be composed of only the above steel slag, but one or more kinds of granular materials and aggregates other than steel slag, such as natural sand, natural crushed stone, artificial sand processed natural crushed stone, It can be included in a range that does not hinder the film forming ability of the slag. However, since the present invention is to generate a shell-like film on the surface of the bank structure utilizing elution of Ca ions from the steel slag, the submerged bank material A is mainly composed of steel slag, that is, The ratio of steel slag needs to be 50 mass% or more, preferably 70 mass% or more.

The shell-like film is preferably generated in a relatively short time in water. For example, the shell-like film having a predetermined thickness is formed within 6 months, preferably within 3 months after the submerged dike A is installed in water. Preferably it is formed.
In order to appropriately generate the shell film in a relatively short period of time, it is necessary to sufficiently ensure the elution of Ca ions from the steel slag. The elution of Ca ions varies depending on the type and particle size of the steel slag. The smaller the slag particle size, the easier the Ca ions to elute, and the steelmaking slag more easily elutes Ca ions than blast furnace granulated slag. For this reason, when using steelmaking slag, it is preferable that the submerged dike material A contains 10 mass% or more of steelmaking slag having a particle size of 2 mm or less. It is preferable to contain 20 mass% or more of granulated blast furnace slag having a diameter of 1 mm or less. Moreover, steelmaking slag and blast furnace granulated slag may be mixed, and in this case, it is preferable to satisfy any of the above conditions.

  In the submerged dike constructed according to the present invention, the entire dike structure may be constituted by the submerged dike material A, but the outer layer portion is constituted by the submerged dike material A, and the inner layer portion is constituted by another submerged dike material B. It may be configured. FIG. 4 shows such a submerged dike (longitudinal section). As the submerged dike material B constituting the inner layer portion of the bank structure, one or more kinds of arbitrary materials such as construction residual soil, dredged soil, and massive steel-making slag can be used.

Further, in the method of the present invention, after the bank structure is constructed, the submerged bank material may flow out due to waves or the like until a shell-like film is formed on the surface of the bank structure. One or more of the following methods can be taken as a measure for preventing the leakage of the submerged levee material.
(I) At least a part of the constructed levee structure is covered with a covering for preventing the loss of latent levee material, and a shell-like film is formed on the surface layer of the dam structure covered with the covering, and then the covering is formed. How to remove.
(Ii) At least a part of the constructed levee structure is covered with a covering for preventing the loss of latent levee material and being decomposed or / corroded over time in water, and the dam structure covered with this covering A method in which after a shell-like film is formed on the surface layer of the body, at least the main part of the covering disappears by decomposition or / and corrosion (natural disappearance).
(Iii) The submerged levee material A is placed in a container that is water permeable and decomposes or / and corrodes over time in water, and by building up the container, at least a part of the outer layer portion of the levee structure is constructed, A method in which at least a main part of a container disappears by decomposition or / and corrosion (natural disappearance) after a shell-like film is formed on the surface layer of the submerged levee material (= the outer layer part of the bank structure).

FIG. 5 shows an embodiment (longitudinal dike longitudinal section) of the above methods (i) and (ii), and 3 is a covering for preventing the loss of submerged dike material. In any of the above methods (i) and (ii), the covering 3 can be formed of a net or a sheet. On the other hand, in order to generate a shell-like film on the surface layer of the bank structure, Mg ions need to be supplied to the surface layer of the bank structure, and therefore the coating body 3 has water permeability and is coated. It is preferable that the seawater is exchanged appropriately inside and outside the body 3.
The covering body 3 should just coat | cover all or one part of the bank structure 1 in the form which can prevent the loss of a submerged bank material. Moreover, the fixing method of the coating | covering body 3 is also arbitrary, For example, what is necessary is just to fix to a water bottom with a suitable anchor means.

In the method (i), after the shell-like film is formed on the surface layer of the bank structure 1, the covering 3 is removed and collected by underwater work of a diver.
On the other hand, in the method (ii), after the shell-like film is formed on the surface layer of the bank structure 1 covered with the covering 3 by using the covering 3 that decomposes and / or corrodes with time in water. Then, at least the main part of the covering 3 is made to disappear (natural disappearance) by decomposition or / and corrosion. In this way, the covering 3 is made of a material that decomposes and / or corrodes over time in water, and eventually disappears spontaneously to prevent the covering 3 from becoming dusty and causing environmental pollution. In order to make the submerged levee a suitable environment for living and growing organisms (underwater animals and plants), it is necessary that the submerged levee material A is exposed (rock surface state) on the surface of the submerged levee, For such as.

Here, as the covering 3 that decomposes and / or corrodes over time in water, for example, a biodegradable plastic sheet or net, a plant or plant fiber sheet or net (for example, straw, linen cloth, etc.) ), A metal foil made of steel, a metal net, or the like can be used, but is not limited thereto. In water (especially in seawater), for example, for several months to one year, at least the main part gradually decomposes and / or corrodes and eventually spontaneously disappears, and the decomposition and corrosion is underwater. Those that do not adversely affect the environment are preferred.
The covering 3 does not disappear before the shell-like film is formed on the surface layer of the bank structure 1, and the type, composition, thickness, etc. may be selected in order to fulfill the necessary loss prevention function. The biodegradable plastic will be described in detail later.

FIG. 6 shows an embodiment (longitudinal dike longitudinal section) of the above method (iii), and 4 is a container (bag) containing the dike material A. In the method (iii), the submerged levee material A is placed in a container 4 that is water permeable and decomposes or / and corrodes over time in water. In general, the operation of putting the submergence material A into the container 4 is performed on land or on a ship.
As the container 4, a bag is particularly preferable for the reason described later, but a container having a certain degree of rigidity (for example, a box, a basket, etc.) may be used.

  Also in this method, after the shell 4 is generated on the surface layer of the submerged dike material A (= the outer layer portion of the bank structure) in the container 4 using the container 4 that decomposes and / or corrodes with time in water, the container 4 At least the main part of the material is lost (naturally disappeared) by decomposition or / and corrosion. In this way, the container 4 is made of a material that decomposes and / or corrodes over time in water, and eventually disappears spontaneously to prevent the container 4 from becoming polluted and causing environmental pollution. In order to make the submarine a suitable environment for living and growing organisms (underwater animals and plants), it is necessary that the submerged dike surface A is exposed (rock surface), etc. Because.

  The material of the container 4 is the same as that of the covering 3 of the method (ii). That is, the container 4 uses, for example, a biodegradable plastic sheet or net, a plant or plant fiber sheet or net (for example, a bag, hemp cloth, etc.), a metal foil made of steel, a metal net, or the like. However, the present invention is not limited to this. In water (especially in seawater), for example, for several months to one year, at least the main part gradually decomposes and / or corrodes and eventually spontaneously disappears, and the decomposition and corrosion is underwater. Those that do not adversely affect the environment are preferred.

  In order to form a shell-like film on the surface layer of the submerged dike material A in the container, it is necessary that Mg ions are appropriately supplied to the surface layer of the submerged dike material. For this reason, the container has water permeability (water permeability). It is necessary that the seawater exchange for the material surface layer is performed appropriately. Here, the container having water permeability is a gap that allows water to permeate into the container although the material constituting the container is non-permeable, in addition to the material itself constituting the container having water permeability. And containers having holes. In such a container, water permeates into the container through the gap or hole.

Further, in order to build up a structure or the like by stacking containers according to the shape of the water bottom or the like, the container containing the material A is preferably deformable, and from this viewpoint, the container is preferably a bag body. A container (for example, a box, a basket, etc.) having a certain degree of rigidity may be used.
Moreover, in order to build up the bank structure by stacking the containers 4 in accordance with the shape of the bottom of the water, it is preferable that the container 4 containing the submerged bank material A can be deformed. From this viewpoint, the container 4 is a bag body. Although it is preferable, there may be a container (for example, a box, a basket, etc.) having a certain degree of rigidity.
In view of the above, the container is particularly preferably a cloth bag or a net bag. As the cloth bag, for example, a so-called flexible container bag (preferably, a bag that is not waterproofed) can be used.

In addition, the type, composition, and thickness of the container 4 are selected so that they do not disappear before the shell-like film is formed on the surface layer of the submerged dike material in the container 4 so as to perform the necessary loss prevention function. do it.
7 shows another embodiment (longitudinal dike longitudinal section) of the above method (iii), in which the outer layer portion of the dike structure 1 is filled with a container 4 containing a submerged dike material A (especially a bag body). The inner layer portion is constructed by stacking the submerged dike material A. Moreover, you may use the submerged dike material B other than the submerged dike material A for an inner layer part similarly to FIG.

The biodegradable plastic used in the covering 3 of the method (ii) and the container 4 of the method (iii) is decomposed by microorganisms when placed in an environment such as soil or seawater, and finally It refers to plastic that becomes water and carbon dioxide. This type of plastic has functions (strength, etc.) equivalent to other general plastics under normal use conditions.
There are no particular restrictions on the type of biodegradable plastic used, but for example, polylactic acid mainly made from plant starch such as corn, PHB produced by microorganisms, and bacterial cellulose can be used. When these are used, for example, bacterial cellulose having a high decomposition rate and polylactic acid having a low decomposition rate are mixed, and the mixing rate is adjusted to adjust the decomposition rate of the covering 3 or the container 4. it can.

The biodegradable plastic covering 3 or container 4 is placed in water and then decomposed over time by the microorganisms in the water and eventually disappears. However, the type and composition of the biodegradable plastic and the thickness of the coating By selecting the size, the decomposition / disappearance period in water can be set.
Biodegradable plastic decomposes into CO ₂ and water, so there is no risk of adverse effects on the natural environment.

  In addition, the biodegradable plastic covering 3 and the container 4 are partially mixed with or physically combined with substances other than the biodegradable plastic, in addition to those composed entirely of biodegradable plastic. The thing (namely, the covering and container which mainly consisted of biodegradable plastics) is also contained. It is preferable that the main constituent material or the biodegradable plastic which is a constituent member decomposes and disappears over time, so that the main part of the covering 3 and the container 4 can disappear.

In the above-mentioned methods (ii) and (iii), the covering 3 and the container 4 are those that spontaneously disappear due to decomposition or / and corrosion. For this, a covering 3 or a container 4 that does not easily disappear naturally may be used. Therefore, the covering 3 covering the bank structure may not be removed as in the method (i) above, but may be left as it is after the shell-like film is formed on the surface layer of the bank structure.
The water area where the submerged dike of the present invention is constructed includes not only coastal sea areas such as harbors and inland seas, but also rivers, estuaries, lakes and marshes in brackish water areas.

  The submerged dike of the present invention obtained by the construction method as described above is constructed by stacking submerged dike material on the bottom of the water, and at least the outer layer portion is mainly composed of granular or / and massive Ca-containing materials (steel slag, etc.). A dike structure composed of a submerged dike material A (including a case of a submerged dike material composed only of granular or / and massive Ca-containing material), and precipitation of magnesium hydroxide on the surface layer of the dike structure Or a submerged dike in which a shell-like film composed mainly of precipitates of magnesium hydroxide and calcium hydroxide is formed.

[Example 1]
Using the submerged dike materials (1) to (10) shown in Table 1, in the actual sea area (water depth of 4.0 to 4.5 m) in the inner bay where the wave conditions are relatively calm, the height is 2 m, the width is 5 m, and the length. A 5m submerged dike was constructed. In the submerged dike materials (1) to (8), steelmaking slag having a particle size of 2 mm or less is 40 mass%, and blast furnace granulated slag having a particle size of 1 mm or less is 80 mass%. It was. Moreover, about the submerged dike materials (9) and (10), the steelmaking slag and the blast furnace granulated slag of the particle size described in the margin of Table 1 were used.
Cover the surface of the embankment structure piled up with submerged levee material with a plastic covering mesh (mesh opening 1mm), and remove the covering mesh one month after the construction of the submerged levee. The thickness of the generated shell film was examined at a plurality of locations, and the average value was obtained. The results are shown in Table 1.

  In addition, the average thickness t of the shell-like film is obtained by measuring the film cross-sectional area S in the thickness direction in a predetermined length range L as shown in FIG. 8, and [average thickness t = film cross-sectional area S / length L]. Asked. That is, the shell-shaped film cross section of the sample collected from a plurality of locations of the bank structure was polished, and the film cross-sectional area S in the length range L of about 500 mm to 800 mm arbitrarily selected was measured. In the measurement of the film cross-sectional area S, a grid of 1 mm square was applied to the image magnified 10 times, the squares of the grid containing the shell-shaped film part were counted, and the film cross-sectional area S was obtained from the number. In addition, about the square containing a shell-like film | membrane part and an other than that part, it counted as 1/2. Further, non-precipitates such as slag particles contained in the shell-like film part were also counted as a part of the film (however, the cavity part was not counted).

[Example 2]
A plurality of specimens made of a single steelmaking slag material were placed in a water-permeable hemp sack, and a plurality of specimens were installed on the seabed at a depth of about 10 m in the coastal sea area assuming a submerged dike. After four and a half years, the state of installation was investigated, but the hemp slag containing the slag was kept in the almost installed state without being swept away by the waves, and the slag inside was kept in a solid state. It was.
When the inside of some hemp bags was opened and the inside was confirmed, a relatively thick shell film (several mm or more) was formed on the surface of the specimen (slag), and the slag inside the shell film was about 20 cm. It was consolidated by thickness. This shell-like film + slag consolidated part (20 cm × 10 cm × 30 cm) was taken as a sample for compression test, uniaxial compression strength was measured, and adhesive strength was evaluated based on the result.

The adhesive strength is generally determined by a triaxial compression test (for example, JGS0524, Geotechnical Society Standard), but a value corresponding to 1/4 to 1/5 of the compressive strength determined by a uniaxial compression test (JIS-A-1216). It may be used. The present inventors have conducted experiments in advance, and if this adhesive force (a value corresponding to 1/4 to 1/5 of the uniaxial compressive strength) is 20 kN / m ² or more, preferably 35 kN / m ² or more, high wave stability. It was confirmed that it functions sufficiently as a submerged dike.
As a result of the compression test, the uniaxial compressive strength of the sample was 390 kN / m ² . From this result, it was estimated that the adhesive strength was about 80 to 100 kN / m ² , and it was confirmed that high wave stability was obtained as a submerged dike.

Explanatory drawing showing an example of installation form (longitudinal section) of submarine Explanatory drawing which shows typically the cross section of the shell-like film | membrane produced | generated in the surface layer of a bank structure in the construction method of this invention SEM image of the cross-section of the shell-like film generated on the surface of the submerged levee material (slag) installed in seawater, and surface analysis images of Mg and Ca using SEM Explanatory drawing which shows one Embodiment (submerged dike longitudinal section) of the method of this invention Explanatory drawing which shows other embodiment (submersible longitudinal section) of this invention method Explanatory drawing which shows other embodiment (submersible longitudinal section) of this invention method Explanatory drawing which shows other embodiment (submersible longitudinal section) of this invention method Explanatory drawing which shows typically the thickness direction cross section of the shell-shaped film | membrane produced | generated in this invention method

Explanation of symbols

1 Levee structure 2 Block 3 Covering body 4 Container x Shell-like film y Material particles

Claims (9)

By laminating a submerged dike material on the bottom of seawater or brackish water, at least the outer layer part contains a granular or / and massive Ca-containing material of 50 mass% or more. However, only the granular or / and massive Ca-containing material is contained. (Including the case of a submerged levee material), and a shell-like film mainly composed of precipitates of magnesium hydroxide or magnesium hydroxide and calcium hydroxide on the surface layer of the dam structure It is a construction method of Sentsutsumi that Ru to generate,
The submerged dike material A contains 40 mass% or more of steelmaking slag having a particle size of 2 mm or less . By laminating a submerged dike material on the bottom of seawater or brackish water, at least the outer layer part contains a granular or / and massive Ca-containing material of 50 mass% or more. However, only the granular or / and massive Ca-containing material is contained. (Including the case of a submerged levee material), and a shell-like film mainly composed of precipitates of magnesium hydroxide or magnesium hydroxide and calcium hydroxide on the surface layer of the dam structure It is a construction method of Sentsutsumi that Ru to generate,
The submerged dike material A contains 20 mass% or more of granulated blast furnace slag having a particle size of 1 mm or less . The submerged bank construction method according to claim 1 or 2, wherein the granular or / and massive Ca-containing material is slag generated in a steel manufacturing process. The method for constructing a submerged embankment according to any one of claims 1 to 3, wherein the average thickness of the shell-like film formed on the surface layer of the embankment structure is 0.5 mm or more. The construction method of a submerged levee according to any one of claims 1 to 4 , wherein at least a part of the constructed levee structure is covered with a covering for preventing the submerged levee material A from being washed away. At least a part of the constructed levee structure is covered with a covering for preventing the leakage of the submerged levee material A and decomposed or / corroded over time in water, and covered with the covering The method for constructing a submerged levee according to any one of claims 1 to 5 , wherein after the shell-like film is formed on the surface layer of the broken levee structure, the covering is removed by decomposition or / and corrosion. The submerged levee material A is placed in a container that is water-permeable and decomposes or / and corrodes over time in water, and the container is stacked to construct at least a part of the outer layer portion of the levee structure. The method for constructing a submerged dike according to any one of claims 1 to 6, wherein after the shell-like film is formed on the surface layer of A, the container is removed by decomposition or / and corrosion. A submerged levee material A (provided that at least the outer layer part contains granular or / and massive Ca-containing material of 50 mass% or more constructed by stacking the submerged dike material on the bottom of seawater or brackish water (however, granular or / and massive Ca A dike structure including a case of a submerged dike material composed only of inclusions, the main layer of which is a precipitate of magnesium hydroxide or a precipitate of magnesium hydroxide and calcium hydroxide on the surface layer of the dike structure A submerged dike created by a shell-like film ,
The submerged levee material A contains 40 mass% or more of steelmaking slag having a particle diameter of 2 mm or less . A submerged levee material A (provided that at least the outer layer part contains granular or / and massive Ca-containing material of 50 mass% or more constructed by stacking the submerged dike material on the bottom of seawater or brackish water (however, granular or / and massive Ca A dike structure including a case of a submerged dike material composed only of inclusions, the main layer of which is a precipitate of magnesium hydroxide or a precipitate of magnesium hydroxide and calcium hydroxide on the surface layer of the dike structure A submerged dike created by a shell-like film ,
The submerged dike material A contains 20 mass% or more of granulated blast furnace slag having a particle size of 1 mm or less .