JPH074125B2 - Construction method of undersea structure using sludge - Google Patents

Description

The present invention relates to a method for constructing an undersea structure for constructing a structure on the seabed. More specifically, for the purpose of improving the marine environment as a fishing ground and creating a fishing ground environment, (a) sediments in rivers and sea areas, and soft excavated soil, incineration ash, fly ash, blast furnace slag, etc. that are generated in civil engineering works (Hereinafter, abbreviated as “sludge” in the present specification) is effectively used as a resource, and (b) suitable for a growth environment of plankton, which is indispensable for fish habitation, for example, upwelling circulation flow is generated. The present invention relates to a method for constructing an undersea structure (so-called seamount) in the sea.

[Prior Art] With the era of 200 nautical miles along the coast, there are high expectations for the development of advanced utilization technology that considers appropriate environmental conservation in the area.

On the other hand, the seabed purification technology for the conservation of the marine environment has been sought after, because the increase and deterioration of the bottom sediment due to the development and the artificial increase and the integration due to the recent rapid growth have caused adverse effects.

Development of technology for improving bottom sediment due to deterioration of bottom sediment in the sea area is an important issue for marine environment conservation. As an enormous amount of bottom sediment improvement, although civil engineering techniques such as removal, solidification, and replacement of the bottom sediment and microbiological techniques have been proposed,
No definitive solution has been found yet. As conventional methods for improving bottom sediment, it has been attempted to use soil (cover soil), tillage, and dredging. The soil is a method of suppressing the elution of nutrient salts from the sediment and the generation of organic matter by spraying and coating new sediment on the sediment that has accumulated organic matter. In addition, tillage is a method of forcibly agitating and reversing by towing a tiller in a hardened bottom area or a bottom area where organic matter is accumulated. Next, for the dredging, the target area is the accumulated dust and sediment, removal of sediment that inhibits seawater flow within the fishing ground, removal of sediment containing a large amount of organic matter,
It is a method of excavating the seabed to maintain an appropriate growth depth for aquatic products.

On the other hand, in the fisheries world, in order to respond to the era of 200 nautical miles, a shift from "fishing" to "creating" is aimed. In other words, the development of cultivation and fisheries and marine farm technology is desired.

Conventional aquaculture has mainly used shallow water such as seaweed and shellfish cultivation, fish cultivation, and fish reef installation on the shallow coast, but in recent years, the shallow sea area that is easy to develop has decreased, and deep-sea nutrient salts have been developed. The development of a good fishing ground development technology that retains floating fish, such as mackerel, yellowtail, bonito, and tuna, by raising the abundant cold water of the bottom of the lake to propagate plankton, has become an issue.

Living organisms in the ocean are unevenly distributed on the surface of the ocean, but their distribution is greatly affected by ocean currents, that is, ocean currents (horizontal currents) and upwelling currents (vertical currents). The marine organisms are under the ecosystem in which higher order plant chains are formed by feeding plankton. As the ocean nutrient supply mechanism used for the lower stage of this plankton, in addition to the inflow of inland water, there is an upwelling supply from the deep ocean. This is because the nutrient is deeper than the ocean surface. Upwelling plankton high production areas are said to have 10 times the productivity of other sea areas. Because of this, good fishing grounds in the ocean have a close relationship with upwelling areas. This can be understood from the fact that despite the upwelling area covering 0.1% of the total sea area, fish production accounts for half of the total sea area.
By the way, the upwelling areas found in the waters around Japan include the eolian upwelling areas,
Three types of topographical upwelling areas and mixed types of both are recognized.

For the above reasons, the construction of undersea structures, especially artificial upwelling facilities, becomes a major issue. As such facilities, consideration will be given to causing upwelling by installing concrete structures, submarine fences, Venturi pipes, etc. on the seabed, and using wind power, wave power, or solar energy to pump deep seawater by power. Has been done.

[Problems to be Solved by the Invention] However, in the above-described conventional upwelling facility,
For example, when constructing a concrete structure, the material and construction are large and the cost is high, and it is difficult to construct in a short time. There are problems in navigation, and there are problems in cost, certainty, and feasibility, etc., and none have been realized at present. In addition, no effective technology has been proposed that can simultaneously solve the required purification technology and sludge treatment technology for conservation and advanced utilization technology.

[Means for Solving the Problems] In view of the above-mentioned conventional problems, the present inventor has proposed a structure for forming a seabed at a low cost, which can be used for a long time even in the sea while purifying the seabed and effectively using sludge. As a result of various studies to develop a construction method capable of constructing an object, the present invention has been achieved.

That is, according to the present invention, in the construction of the undersea structure, when filling a mixture of a sludge containing nutrients with a solidifying material into a container installed at a predetermined position on the seabed, the mixture is injected into the container to rise. With a seal to
Provided is a method for constructing an undersea structure in which a pipe body is hung in the container and a mixture is injected through the pipe body.

As a result, it is possible to purify the harmful sea area and dispose of a large amount of sludge, and at the same time, construct a structure in the sea.

The undersea structure targeted by the present invention mainly targets upwelling currents, but can be a stable nutrient salt supply structure over a long period to the oligotrophic sea area. Furthermore, this undersea structure can also be utilized as a fish reef.

The sludge used in the present invention refers to the sediment of rivers and sea areas, and a mixture of this sediment with soft excavated soil, incineration ash, fly ash, blast furnace slag, etc. generated in civil engineering work. In particular, sediment is large in amount, contains a large amount of water, is difficult to dry naturally, and produces a foul odor due to the decomposition of organic matter. Therefore, it is not easy to treat economically, and the method of treatment is established. Is an urgent task. In particular, the treatment of bottom sediment that increases environmental pollution is not done, there is no definitive solution, and the current situation is to avoid occasional problems.

Therefore, by utilizing the bottom sediment as a construction material of the present invention, it is very useful in terms of environmental protection.

Further, in the present invention, the container may be made of steel, cloth, a film or a sheet, or a waste ship or the like. When filling a mixture of sludge and solidifying material into a container installed at a predetermined position, a pipe is hung from the ship to the inside of the container and the mixture is filled into the container through this pipe to prevent seawater contamination. It is preferable because it can be surely put on the surface and the design position.

When the sludge to be mixed is rich in organic matter, the mixture of sludge and solidifying material is itself a nutrient salt supply, unlike the structure of natural stone or concrete, and as a function of the structure. It has a function as a nutrient supply.

[Embodiment] Next, an example of the construction method of the present invention will be described with reference to FIGS.

In the present invention, when constructing a structure in the sea, a container (or tank) 9 (see FIG. 1), which acts as a formwork, is filled with a mixture of sludge and a solidifying material, and a predetermined amount of the sea floor is filled. Install in position.

The cross-sectional shape of the container (or tank) 9 may be circular or rectangular and is not particularly limited. As the material, a metal material such as a steel plate, plastics, a film, a sheet or the like can be used.

Next, when filling the mixture in a container installed at a predetermined position on the seabed, a steel tank 9 was installed on the seabed as shown in FIGS. 1 and 2, and a nutrient salt was contained from the sludge carrier 2 or the like. The mixture 14 obtained by mixing the sludge with the solidifying material is injected into the steel tank 9 through the injection transport pipe 10 to form a structure. 3
Is a treatment plant in which the solidifying material is mixed with the sludge containing nutrient salts.

Although the size of the tank 9 is determined by the installation water depth and the scale of the structure, for example, the unit is 20 m (diameter) × 4 m (height), and these are stacked and installed to construct a predetermined structure. . In the case of a tank having a diameter larger than the above, the height is not particularly limited, but may be set to about 1/5 the diameter. Further, in order to prevent contamination during injection and diffusion of the mixture, inside the tank 9 is provided a seal 11 that moves up and down as the mixture is injected. In addition, in FIG. 1 and FIG.
Indicates a seal ring.

In the present invention, when an undersea structure is constructed by curing a mixture of sludge and a solidifying material, the cured product itself has abundant nutrient salts, and organisms that require these nutrient salts grow. Since the living environment (ecosystem) is formed and nutrient salts are indirectly used, it has excellent characteristics as an undersea structure that cannot be obtained by conventional concrete or steel structures.

As the solidifying material, various conventionally known materials can be used, but a material mainly composed of three materials of gypsum, a pozzolanic material and a cement material is preferable. The solidifying material is characterized in that even if the target sludge contains an organic substance or a phosphate that inhibits the setting reaction of Portland cement, the solidification material reacts effectively to achieve the purpose. When the solidifying material is mixed with sludge, the components of the solidifying material and water and fine soil particles contained in the sludge (a) ion exchange reaction of fine soil particles (b) ettringite formation reaction (c) Pozzolanic reaction that produces a tobermonite mineral-like phase (d) Calcium carbonate formation reaction (e) Formation reactions of amorphous gel-like substances due to various reactions occur in parallel, and the skeleton and adhesive non-crystalline form required for soil stability Substances are generated in sludge, which is chemically improved and solidified.

If sludge is a mixture of soft excavated soil, incineration ash, fly ash, blast furnace slag, etc., which is generated in civil engineering work, the blast furnace slag, etc. is effective as a filler or aggregate depending on the site conditions. Is preferred.

[Effects of the Invention] As described above, according to the method for constructing an undersea structure of the present invention, the following effects can be obtained.

It can detoxify a large amount of sludge due to normal treatment and effectively use it.

It is possible to construct a new development facility with seabed purification and a structure that uses sludge as a material.

Sludge from eutrophic waters can be moved to oligotrophic waters to build a nutrient supply facility.

Large undersea structures can be constructed economically.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a seabed container used in the construction method of the present invention, and FIG. 2 is an overall schematic view showing an example of the construction method of the present invention using a seabed container. 2 ... Sludge carrier, 3 ... Treatment plant, 9 ... Submarine tank,
10 ... injection transport pipe, 11 ... seal, 12 ... seal ring, 14 ...
blend.

Claims (2)

[Claims] 1. When constructing an undersea structure, when a mixture of a sludge containing nutrients and a solidifying material is filled in a container installed at a predetermined position on the seabed, a seal that rises by injecting the mixture into the container is used. A method for constructing an undersea structure, characterized in that the pipe body is provided over the container and the mixture is injected through the pipe body. 2. The construction method according to claim 1, wherein the undersea structure is an artificial upwelling facility.