JPH0765304B2 - Tidal flat creation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a method for constructing a landfill tidal flat in a coastal sea area, a lake or the like (collectively referred to as a coastal sea area in the present specification), and more specifically, in a coastal sea area. The present invention relates to a method of effectively utilizing soft mud and dredged soil (generally referred to as bottom sediment in this specification) to construct a tidal flat.

[Prior Art] In Japan, where the land is small and the resources are scarce, the vast marine space surrounding it is a valuable land resource. Therefore, conservation of the marine environment and appropriate advanced utilization of coastal waters are important issues.

Improving bottom sediment, which is part of the conservation of the marine environment, is indispensable because the amount of deposits in the inner bay and inland sea area is enormous, and it is necessary to use civil engineering techniques such as removal, solidification, and replacement of the bottom sediment. Microbiological methods are being proposed and developed. However, no definitive solution has yet been found.

Conventionally, as a method for improving the bottom sediment, the soil (cover soil), the tillage, and the dredging have been tried. The soil is a method in which the sediment is the target area, and new sediment is sprinkled on the seabed to cover the generation of harmful substances with the soil. In addition, tillage is a method of cutting back, crushing or agitating the seabed soil using a bulldozer or a ship, targeting the hardened bottom area.
Next, the dredging targets the accumulated dust and sediment as the target area, and removes the sediment that blocks the seawater flow in the fishing ground, removes the sediment containing a large amount of organic matter, and It is a method of digging into the seabed to maintain the growth water depth.

In addition, various proposals have been made for advanced utilization of coastal waters, but among them, many requests have been made to reclaim the coastal waters to create tidal flats and to provide shellfish breeding grounds, mainly for clams and clams. ing. Conventionally, tidal flats are generally constructed by constructing a masonry revetment at the outer edge (tip) of the planned sea area, and then burying the area up to the coast.
It is done by covering it with sand.

[Problems to be Solved by the Invention] The bottom sediment has (1) a large amount, (2) a large amount of water and is difficult to be naturally dried, and (3) an offensive odor is generated due to decay of organic matter, etc. There is a problem. Therefore, in the present invention, the bottom sediment is effectively used to conserve the marine environment and to make advanced use of coastal waters.

The conventional problems in extending a breeding ground toward the offshore and creating a tidal flat are as follows. In other words, (1) the offshore tip of the tidal flat must be a particularly strong revetment because the loss and damage caused by external forces such as tidal currents and waves are large, and (2) the construction of a vast tidal flat. It requires a large amount of earth and sand, and (3) it is not practical because it requires a large amount of money to cope with these (1) and (2).

[Means for Solving the Problem] Therefore, in order to solve the problems in the above-described conventional tidal flat creation method, the present inventor has focused on utilization of bottom sediment and has proposed the present invention.

That is, according to the present invention, in forming a tidal flat in the coastal sea area, (a) the outer edge portion of the tidal flat building area is filled with a bottom material to which a solidifying material is added in an uncured state and formed into a rod shape. Then, the rod-shaped formation is put into the sea and then cured, and then the uncured rod-shaped formation is sequentially stacked on the cured rod-shaped formation to form a revetment, (b) the tidal flat formation area The step of adding the bottom sediment to (c) the step of increasing the strength of the upper layer of the bottom sediment input to the tidal flat formation area, and (d) the step of laying sand on the upper part of the strength increasing treatment. A method of creating a tidal flat comprising the steps of ,.

[Operation] In the present invention, when forming a tidal flat in the coastal sea area, after strengthening the bottom sediment at the outer edge (tip) of the tidal flat building area to form a revetment, the area from this revetment to the coast The bottom sediment of the seabed is put in, then the strength of the upper layer of the bottom sediment is increased, and then sand or the like is further coated on it for habitation of shellfish.

In this way, by using the bottom sediment and these strength-increasing treatment products in combination, the outer edge of the tidal flat is protected by the bottom sediment strength-increasing treatment product, so it may be washed away or damaged by ocean currents, waves, etc. There is no. In addition, since a large amount of seabed sediment is used, it is possible to remove sediment that causes many harmful effects and effectively utilize it, which can be useful for improving the sea environment.

In the present invention, the strength increasing treatment of the bottom sediment put into the tidal flat planned area is carried out by adding various solidifying materials to the bottom sediment and putting it into the sea in an uncured state to harden (increase strength) in the sea, or After curing it into a predetermined shape, put it in the sea, etc.
Either method may be used, and it is decided in consideration of the state of the ocean current and the seabed.

Further, in the present invention, the outer edge of the tidal flat construction is filled with a solidified material bottom material in an uncured state into a bag to form a rod, and the outer rod-shaped product is put into the sea and then cured. Next, the revetment is formed by successively stacking the bar-shaped products in which the filler (bottom material and solidifying material) is uncured on the hardened bar-shaped products. The revetment formed in this way becomes strong and protects the outer edge of the tidal flat even under severe conditions such as tidal currents. The shape and height of the revetment, the strength of the hardening part, etc. are determined by the local conditions such as tidal current, waves, depth and topography.

The material of the bag body described above is not particularly limited, and various materials are used. For example, natural fiber, regenerated fiber, semi-synthetic fiber, synthetic fiber, or inorganic fiber is used as the fiber material, and synthetic or semi-synthetic polymer sheet is used as the plastic material. These materials, alone or as a composite, are processed into a bag having shapeability.

As the solidifying material used for hardening the sediment of the present invention, a cement-based solidifying material is usually used. However, when the sediment contains a small amount of an organic substance or a cement setting inhibitor such as a phosphate (generally 2% or less of the organic substance). Can use the cement specified by JIS standard. The cement-based solidifying material is not specified by JIS standards or the like, but is developed as a special purpose.

In the present invention, the most suitable solidifying materials for hardening the bottom material include those having three main materials of gypsum, a pozzolanic material and a cement material as main materials. This is characterized in that even if the sediment contains organic substances or phosphates that inhibit the setting reaction of Portland cement, it reacts effectively and achieves the purpose. When this solidifying material is mixed with the sediment, the components of the solidifying material and the water and fine soil particles contained in the sediment (a) Ion exchange reaction of fine soil particles (b) Ettringite formation reaction ( c) Hozolane reaction that forms a tobermonite mineral-like layer (d) Calcium carbonate formation reaction (e) Formation reactions of amorphous gel-like substances by various reactions occur in parallel, and the skeleton and the adhesive A crystalline substance is generated in the sediment, and the sediment is chemically improved and hardened (increased strength).

In addition to the solidifying material, a filler may be added as an additive. When the filler is mixed as an additive for the strength increasing treatment of the bottom sediment, the tensile strength of the obtained strength increasing treated product is improved, which is preferable. Various fillers are used, but among them, steel fiber, glass fiber, carbon fiber, or aramid fiber has a great effect when used as the filler.

The bottom sediment used for the development of tidal flats for the propagation of shellfish, etc. was confirmed to be safe by carrying out a pollutant elution test based on the elution test of the "Bottom Sediment Survey Method" (Kanmizukan No. 127 dated September 8, 1988). To use. By the way, as the elution test method, the Environmental Agency Notification No. 13 (Matters that determine the test method for hazardous substances contained in industrial waste) and No. 14 (Marine pollution prevention) based on the Marine Pollution Control Law concerning waste dumping into the ocean There is a test method based on the items specified in the inspection method for harmful substances contained in waste to be discharged to landfill sites, etc. specified in Article 5, Paragraph 1 of the Law Enforcement Order. However, the elution time and pH of the eluate are slightly different from those obtained by the “sediment investigation method”.

In addition, sewage sludge, incineration ash, fly ash and the like can be added to the bottom material of the present invention.

[Examples] Hereinafter, the present invention will be described in more detail based on the illustrated examples, but the present invention is not limited to these examples.

FIG. 1 is a schematic cross-sectional view showing the tidal flat construction method of the present invention in a coastal sea area.

First, a mixture of bottom material and a solidifying material is filled in a bag 2 made of synthetic fiber to form a building member 3. Next, with the filling 1 of the building member 3 in an uncured state, the seabed 5 on which the seawall 4 is to be constructed
Place them on top of each other. Then, after the filler 1 of the installed building member 3 becomes a solidified body, the "building member in which the filler is uncured" produced under the same conditions as above is sequentially stacked on the installed building member 3.

The curing period for hardening the mixture of the solidifying material and the bottom material to be filled in the bag body 2 can be arbitrarily selected, and the strength gradually develops while being placed and laid on the seabed 5, and the strength of the hardened body Therefore, the work of stacking the building members 3 may be performed as long as the solidification strength of the filling material reaches a predetermined strength. The predetermined strength at this time is determined by the size and shape of the cross section of the building member and the specific gravity.

The final strength of this packing 1 is usually the number of uniaxial compressive strength + kg
It is desirable to set f / cm ² or more.

Further, the work of filling the mixture 2 of the solidifying material and the bottom material into the bag body 2 can be performed on the ground, but is usually performed in water. When the filling work is performed in water, there are advantages that workability and operability are improved due to a derivative effect caused by buoyancy, and a load applied to the bag body used in the present invention is reduced.

Next, the bottom material is put into a tidal flat construction to a predetermined thickness to form the bottom layer portion 6, and then an uncured product or a cured product of a mixture of the bottom material and a solidifying material is laid to a predetermined thickness to form a middle layer. Part 7
To form. The final strength of this middle layer is 0 for uniaxial compressive strength.
It is desirable to be 5 to 5 kgf / cm ² . Furthermore, sand or the like on which shellfish and the like can live is coated to a predetermined thickness on the upper layer 8
And In the sand covering of the upper layer portion 8, if pebbles as large as adzuki grains are sprayed on the surface at the same time, it is effective for the deposition of juveniles.

The thicknesses of the lower layer portion 6, the middle layer portion 7 and the upper layer portion 8 described above are determined in consideration of local conditions, soil conditions and the like.

[Effects of the Invention] As described above, according to the tidal flat creation method of the present invention,
Since the bottom sediment and the strength-increasing treated material in which the bottom sediment is hardened by the solidifying material are used, the tidal flat can be protected from being washed away or destroyed by the ocean current or waves. Particularly, in a place where the conditions such as ocean current are severe at the outer edge of the tidal flat, a strong revetment can be constructed by using a bag body filled with a mixture of bottom material and a solidifying material.

Further, according to the method for creating a tidal flat according to the present invention, a large amount of seabed sediment that causes many harmful effects can be removed, and the undiscovered sediment can be effectively used as a material to construct a vast tidal flat. This will effectively improve the sea environment for two birds with one stone.

By the way, the artificial tidal flat provides a fishing ground that is labor-saving in breeding management in a fishing ground environment suitable for the initial generation of low-living organisms and improvement of the survival rate.

In other words, the effects of artificial tidal flats include the following.

(a) It has an accumulation effect on floating larvae such as bivalves.

(b) In addition to bivalve molluscs, it serves as a place of establishment for childish shrimp and scissors, and has a high survival rate after establishment.

(c) It is easy to manage the growth of living things.

(d) Other.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a tidal flat constructed according to the present invention. 1 ... filling, 2 ... bag, 4 ... revetment, 6 ... lower layer, 7 ... middle layer, 8 ... surface layer.

Claims (1)

[Claims] 1. When constructing a tidal flat in the coastal sea area, (a) the bottom edge of the tidal flat construction area is filled with a solidifying material in the uncured state and filled into a bag to form a bar. A step of forming a revetment by successively stacking uncured rod-shaped formations on the cured rod-shaped formations after the rod-shaped formations are put into the sea and then cured, (b) bottom sediment in the tidal flat formation area , (C) a step of increasing the strength of the upper layer of the bottom sediment put in the tidal flat formation area, and (d) a step of laying sand on the upper layer of the strength increasing treatment. A tidal flat creation method characterized by comprising steps.