JP2000265450A - Artificial ground consisting of porous housing and construction method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely support the building frame in the water bottom of the soft ground, and eliminate an adverse effect to the environment of peripheral water area and the ecosystem. SOLUTION: An artificial ground is composed of a bottom slab 5 having a buoyancy adjustable space, side slabs 4, and an upper slab 3 located above water. Through holes 8 wherein a steel pipe pile can be inserted are formed on the bottom slab 5 and the upper slab 3. Housing units 2 formed a space 6 which can flow water to its inside are arranged by joining the housing units adjacent to each other on the water bottom ground 10 leveled out. The supporting means is so constituted that the steel pipe pile 7 penetrated into the water bottom ground 10 are passed through the through holes 8 to join with the housing units 2 for supporting, or a horizontal resistance slab is protruded to a lower side of the bottom slab 5 of the housing unit 2 to soft-land on the water bottom ground 10 leveled out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-scale artificial ground installed on a relatively shallow water surface in soft ground such as the sea, rivers and lakes, and a method for constructing the same. The present invention relates to an artificial ground that has no adverse effect on the environment of the surrounding water area.

[0002]

2. Description of the Related Art In recent years, various large-scale artificial ground plans have been proposed in response to the need for effective use of the sea space. Conventionally, artificial ground has been constructed by constructing a deadline and then landfilled with waste and earth and sand. Recently, however, artificial ground using a large-scale floating body (mega float) has been proposed, and floating airports and various industries have been proposed. Use for facilities, leisure facilities, etc. has been proposed and has become a hot topic. This floating type artificial ground is constructed by joining a large number of box-shaped units made in yards and docks on the sea by levitation and towing, and mooring the larger ones to the seabed with pontoons and mooring lines.

[0003] As another prior art similar to the present invention, there is a "method of constructing artificial ground" disclosed in JP-A-8-232251. As shown in FIG. 13, this artificial ground has an inverted T-shaped vertical wall 24 which rises at the center of a horizontal base 23, and has a hollow air chamber 25 inside its frame, and an air vent plug (not shown). ) Is manufactured on land. After leveling the seabed ground at the construction point of the artificial ground horizontally, the inverted T-shaped unit 21 is towed to the construction point, the adjacent vertical wall portions 24 are arranged orthogonally, the air plug is opened, and the base portion 23 is moved to the seabed ground. Land on. The floor slab 22 is formed on the sea surface above the vertical wall portion 24.

[0004]

Among the conventional techniques, the landfill method requires a long construction period, influences on the environment due to collection and transportation of sediment and sand, land subsidence after landfill, and landfill. There are issues such as adverse effects on the ecosystem in the surrounding waters.

Also, in the case of the floating body method, the level of the upper surface of the artificial ground changes following sea level fluctuations due to tide changes, and when applied to shallow water, the bottom surface of the box-shaped floating body approaches the water bottom surface. Therefore, there is a concern that the flow of water will be obstructed and the ecosystem in the surrounding water area will be adversely affected. In addition, it is said that this floating body type can demonstrate economy at deep water depth,
There is also a problem that it becomes economically disadvantageous when applied to shallow water.

On the other hand, an "artificial ground" (shown in FIG. 13) disclosed in Japanese Patent Application Laid-Open No. H8-232251 floats an inverted T-shaped unit 21 manufactured on land to a construction point of the artificial ground, and pulls an air plug. Since the open buoyancy is released and the base portion 23 lands on the seabed and is installed, the construction period on site can be shortened. Also, an inverted T-shaped unit 21 installed on the seabed ground
Has good stability, and furthermore, the adjacent vertical wall portions 24 are arranged orthogonally to form the floor slab 22 on the sea surface above the vertical wall portions 24, so that the flow of water under the artificial ground is not hindered. It states that underwater ecosystems are preserved.

However, in this artificial ground, the base 23 is landed and supported on the seabed ground. Therefore, sufficient supporting force cannot be obtained on soft ground, and uneven settlement is likely to occur, and large-scale ground improvement is required. In addition, it is easy to move horizontally when it receives horizontal external force such as an earthquake. In addition, the upper slab 22 provided on the inverted T-shaped unit 21 is difficult to join, and since the work is performed on site, the construction period is not shortened. further,
Since the flow of water under the artificial ground passes through the gap between the adjacent vertically arranged vertical wall portions 24, there is a problem that the water flow is refracted and a smooth flow cannot be obtained.

The artificial ground of the present invention solves the above-mentioned problems,
The artificial ground is reliably supported even on the bottom of soft ground, and the flow of water under the artificial ground is smooth so that there is no adverse effect on the environment and ecosystem in the surrounding water area, further shortening the construction period of on-site construction It is intended to provide a construction method.

[0009]

The artificial ground of the present invention that achieves the above object has the following constitution. Explaining with reference to an example shown in FIG. 1 and the following, in the artificial ground 1 of the present invention,
The bottom plate 5 and the upper plate 3 are constituted by a bottom plate 5 having a space 11 capable of adjusting buoyancy, a side plate 4 and an upper plate 3 located on the water surface, and a plurality of through holes 8 into which the pile 7 can be inserted are formed. A plurality of box units 2 each having a space 6 through which water can pass inside are arranged on the leveled underwater ground 10 by joining adjacent box units 2 to each other. The box unit 2 is supported by being connected to a plurality of piles 7 penetrating into the bottom of the water floor, or the horizontal resistance plate 9 is projected below the bottom plate 5 of the box unit 2 to level the water floor. You may make it soft-bottom on the ground 10.

The bottom plate 5 of the box unit 2
The side plate 4 may be manufactured by fixing a stiffener 13 of a mold steel to an outer shell material 12 made of a steel plate, and filling all or a part of the internal space with a medium-filled concrete 15. further,
When the bottom plate 5, the side plate 4, and the upper plate 3 are made of the outer shell material 12 made of a steel plate, a corrosion-resistant metal sheet is lined on a submerged portion, a tidal portion, and a splash portion of the housing unit surface 2 to prevent corrosion. .

The method for constructing the artificial ground according to the present invention will be described with reference to FIGS. 10 (a) and 10 (b), FIGS. 11 (a) and 11 (b).
As shown in FIGS. 12A and 12B, the following (1) to
It comprises the step (7). In other words, (1) a box unit 2 which is composed of a bottom plate 5 having a space capable of adjusting buoyancy, a side plate 4 and an upper plate 3 located on the water surface and having a space 6 through which water can pass, is used as a land yard or dock. Produced at (2) Excavate and level the bottom of the water floor at the place where the box unit is to be installed to a predetermined water depth. (FIG. 10, a) (3) The box unit 2 manufactured in the land yard or dock is levitated and towed to the installation location. (FIGS. 10, b) (4) The buoyancy is reduced by pouring water into the buoyancy adjusting space 11 of one or both of the bottom slab 5 and the side slab 4, and the box unit 2 is submerged on the leveled water bottom ground 10. I do. (FIG. 11,
a) (5) The pile 7 is inserted into the through hole 8 of the box unit 2 from above and penetrates into the underwater ground 10, and the pile head is connected to the box unit with the bonding material 16. (FIGS. 11, b, 12, a) Alternatively, the horizontal resistance plate 9 is projected below the bottom plate of the box unit. In this case, in the step of reducing the buoyancy by injecting water into the buoyancy adjusting space 11 described in the preceding paragraph, the buoyancy is left so that the weight of the box does not become heavy, the bottom is softly settled, and the load on the underwater ground 10 is reduced. (6) After the second and subsequent box units 2 are arranged adjacent to the existing box unit, the level is adjusted and joined with the joining material 17. (12, b) (7) After placing the box unit 2 on the water floor, concrete 15 is filled into the bottom plate 5 and a part of the buoyancy adjusting space 11 of the side plate 4 of the box unit 2 to fill them. This is a method for constructing artificial ground comprising a water-permeable box, which is constructed by the above steps.

[0012]

The artificial ground 1 according to the present invention is greatly characterized in that the space 6 through which water can flow inside the box unit 2 is provided. In other words, the presence of the water-permeable space 6 does not obstruct water flow such as river water at the estuary and tidal currents at the shore, thereby causing a change in the surrounding flow condition. It does not disturb the growth environment of aquatic organisms such as fish and shellfish. Further, since the water flow acting on the box unit 2 is received only by the side plate 4, the pressure receiving area received from the water flow is small, and the design external force can be reduced.

The buoyancy adjusting space 1 of the box unit 2
1 gives buoyancy when floating and towing a box unit 2 manufactured in a land yard or a dock, and after submerging on the underwater ground 10, softly settles on the underwater ground 10 to support the box unit 2. Reduce the applied load. In the case where the box unit 2 is supported by a pile, the vertical load on the pile 7 can be reduced.

Since the box unit 2 is towed with the upper plate 3 positioned above the water surface, only the submerged portion below the bottom plate 5 and the lower portion of the side plate 4 can use buoyancy. For this reason, the stiffener 13 of a mold steel is fixed to the outer shell 12 made of a steel plate so that the bottom plate 5 and the side plate 4 can easily obtain a larger buoyancy. It is preferable that the space 11 is formed and the rigidity is secured. In this case, after the box unit 2 is submerged on the underwater ground 10, all or a part of the internal space is filled with the solid concrete 15.
It is better to fill in the material to secure further rigidity. In addition, the outer shell material 12 made of a steel plate acts as a permanent formwork during the filling operation of the filled concrete 15.

When the bottom plate 5 and the side plate 4 are made of an outer shell material 12 made of a steel plate, in order to prevent corrosion and maintenance, a corrosion-resistant thin metal plate is provided on a submerged portion, a tidal portion and a splash portion on the surface of the box unit 2. Better lining.

In the method of constructing an artificial ground according to the present invention, the box unit 2 is manufactured in a land-like yard or a dock in a state close to a completed form, towed to an installation place, and then leveled in advance. After being laid in the ground 10, the pile 7 is inserted into the through hole 8 of the box unit 2, and the pile 7 is penetrated into the underwater ground 10 and joined, or the horizontal resistance plate 9 is protruded to construct the construction. And the construction period can be shortened.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment for constructing an artificial ground according to the present invention will be described below with reference to the drawings. FIG. 1 is a partial perspective view of an embodiment of an artificial ground 1 according to the present invention, in which a box unit 2 that allows water to flow inside is supported by a pile. This artificial ground 1 is, for example, implemented as an artificial ground installed at the estuary 19 as shown in a perspective view in FIG.
As shown in a plan view in FIG. If an artificial ground is constructed at the above-mentioned location using a conventional landfill method or a box that does not have a water flow space, floods will occur during heavy rains to reduce the river width, and the flow will change. May be changed and scavenging and sedimentation of the riverbed and the surrounding seashore may disturb the growth environment of fish and shellfish, but the present invention does not cause such adverse effects on the environment.

This will be further described with reference to FIG. In the artificial ground 1 of the present invention, a frame formed by joining a plurality of box units 2 is installed on a submarine ground 10 and supported by a steel pipe pile 7 penetrating into a support layer below the submarine ground 10. The box unit 2 forming the frame is composed of an upper plate 3, a side plate 4, and a bottom plate 5 which become the artificial ground surface 1, and the side plate 4 is opened to form a space 6 through which water can pass inside the box unit. I have. The water flow space 6 may be provided in the direction of the water flow 19 such as river water or tidal flow. However, when the water flow 19 does not move or is not determined, it is better to allow water to flow in the orthogonal direction as in the illustrated example.

FIG. 2 is a perspective view of the box unit 2. The box unit 2 is manufactured in a land yard or a dock, floated and towed to the site, and then laid down. For this reason, as shown in FIG. 4B, a buoyancy adjusting space 11 having a pouring / draining valve 14 is provided in the bottom plate 5. When the buoyancy is insufficient with only the bottom slab 5, a buoyancy adjustment space 11 is provided below the side slab 4 as shown in FIG.

The buoyancy adjusting space 11 is a housing unit 2
After being submerged on the water floor at the site, concrete 15 is filled and filled with the concrete 15 except for a portion that retains appropriate buoyancy. (FIG. 5
The box unit 2 is entirely reinforced concrete structure,
Although it may be a composite structure of steel or steel plate and concrete,
As shown in FIG. 4 (a), an upper plate 3 shown in FIG. 4 (b), a bottom plate 5 shown in FIG. 4 (b), and a side plate 4 shown in FIG. In addition, the weight of the box unit 2 with respect to the rigidity can be reduced as compared with concrete, and the buoyancy adjusting space 11 of the bottom plate 5 can be increased. In addition, in all or a part of the buoyancy adjusting space 11 in the outer shell material 12 made of steel shell, the filling concrete 15
Is filled.

As shown in FIG. 2, a steel pipe pile 7 can be inserted into the upper plate 3 and the bottom plate 5 from the upper plate 3 through the bottom plate 5 at a position near the side plate 4, as shown in FIG. A plurality of through holes 8 are provided. Steel pipe pile 7 is box unit 2
Is placed on the underwater ground 10 and penetrates into the underwater ground 10 through the upper and lower through holes 8. The through hole 8 and the steel pipe pile 7 are joined to the buoyancy adjusting space 11 of the box unit 2 so as to be watertight, and water does not flow into the space 11 from this through portion. . Upper version 3 and bottom version 5
The steel pipe pile 7 inserted into each of the through holes 8 is cut at a position penetrating the through hole 8 of the bottom slab 5, and the cut head of the steel pipe pile 7 is attached to the box unit 2 as shown in FIG. Is firmly connected to the bottom slab 5. Although a detailed description is omitted for this connection, known means such as welding via the connection members 16 and 16a, concrete 15 or grout with studs or shear keys interposed therebetween may be used. The through hole 8 on the bottom plate upper surface is closed by a lid 26. The upper part of the steel pipe pile 7 extends to the upper surface of the upper plate 3,
It may be cut at that position and subjected to a water-tight joining process. Further, the steel pipe pile 7 may be a concrete pile. As shown in FIGS. 6 and 7, the artificial ground 1 is configured by joining adjacent box units 2 at the same level in a state where they are installed on the underwater ground 10. Since it is difficult for the joining means to position the end face of the adjacent box unit 2 with high accuracy, it is better to use a method that can join even if there is a certain installation error. Specific joining means between the box units 2 include joining members such as bolt joints and welding (in the drawing, schematically shown as joint members 17),
Use PC steel rods and wires. Further, the joint may be integrated with a dowel (not shown) provided in the box unit 2 by the filling concrete 15.

The submerged, tidal, and splashed portions of the outer surface of the box unit 2 are exposed to a severely corrosive environment. Therefore, when a steel box is used, it is necessary to prevent corrosion. As the anticorrosion means, conventional heavy anticorrosion coating and submerged portions can be used in combination with electric anticorrosion, but maintenance such as repainting for aging deterioration is required. Therefore, it is desirable to adopt an anticorrosion method of lining a corrosion-resistant thin metal such as titanium or stainless steel which can maintain the anticorrosion performance without maintenance for many years.

Next, the method for constructing the artificial ground according to the present invention will be described with reference to FIGS. 10 (a) and 10 (b), FIGS. 11 (a) and 11 (b).
Referring to FIGS. 12A and 12B, the following (1) to (8)
The steps will be described in this order. (1) The depth of the water floor at the artificial ground installation location is shallow, and if the box unit 2 cannot be pulled in, the ground is excavated to a predetermined depth in advance to level the ground. (Shown in Fig. 10 (a)) (2) Box unit 2 manufactured by land yard or dock
Is lifted with the buoyancy adjusting space 11 emptied and floated to the installation location. (See FIG. 10B) (3) When the vehicle reaches the predetermined installation location, the exhaust valve and the water injection valve 14 (shown in FIG. 4B) are opened, and the buoyancy adjusting space 1 is opened.
The buoyancy is reduced by injecting water into 1 and the box unit 2 is gradually submerged and landed on the leveled underwater ground 10.
At this time, it is possible to reduce the supporting force burden of the steel pipe pile 7 by leaving the box unit softly and leaving a certain amount of buoyancy without water being injected into the entire buoyancy adjustment space 11. (FIG. 11
(Shown in (a)) (4) Next, a steel pipe pile 7 is inserted into the through hole 8 of the box unit 2 and the underwater ground 10 is hammered or pressed in.
Let it penetrate inside. Although the connection extension of the steel pipe pile 7 is usually performed by a welding method, it is desirable to adopt a quick joint method such as screwing in for quick construction. (FIG. 11 (b)
(5) When all the steel pipe piles 7 have been penetrated, the steel pipe piles 7
And the box unit 2 are connected by welding via a connecting member 16, a stud dowel, concrete 15 with shear key, grout or the like. The extra length of the steel pipe pile 7 is cut off, and a lid 26 is placed on the upper surface of the box bottom plate 5. (FIG. 12
(Shown in (a)) (6) In the case of the steel box unit 2, the buoyancy adjusting space 11
Is filled with concrete 15 during filling through the above-mentioned injection / drain valve. (7) The second and subsequent box units 2 are placed side by side with the existing box unit 2 adjacent thereto and positioned in the underwater ground 10.
After being laid on the top, the level is adjusted, and the ends of the box unit 2 are joined by a joining material 17 to be integrated. (FIG. 12
(Shown in (b)) (8) Finishing is performed by applying a finishing material 27 (shown in FIGS. 1 and 7) such as concrete or asphalt on the upper surface of the box unit 2.

FIG. 3 shows an example of a box unit for artificial ground of a system not using a pile for the box unit 2. The method of the present invention leaves sufficient buoyancy in the box unit 2 and does not apply a large load to the water bottom ground because it is softly settled on the water bottom ground 10, but the horizontal resistance is reduced by that much, so that the box unit 2
Can easily slide on the bottom of the water. As a countermeasure, in the example of FIG. 3, a horizontal resistance plate 9 is projected below the bottom plate 5 instead of the steel pipe pile 7. If the horizontal resistance plate 9 is an obstacle when towing the shallow water,
A hole similar to the through hole 8 of the pile 7 is provided in advance in the box unit bottom plate 5 so that it can be installed after installation. Using the hole, the underwater ground 10 below is excavated, and a horizontal resistance plate made of steel is installed, or a horizontal resistance plate formed by casting reinforced concrete is provided.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following is an example of the data of a specific embodiment of the artificial ground according to the present invention. When constructing an artificial ground having a plane area of 500 m x 300 m on a soft ground having a depth of 4 m, 30 box units of 50 m x 100 m are joined and configured. Box unit 2 is 11m in height
The interior is a space through which water can pass in both directions. The box unit is provided with a steel pipe pile support or a horizontal resistance plate and is installed on a soft bottom. The upper plate level is +7 m (water surface) and the bottom plate level is -4 m (water surface).

[0026]

The artificial ground according to the present invention reliably supports the artificial ground even at the bottom of the soft ground, and smoothes the flow of water under the artificial ground so that there is no adverse effect on the environment and ecosystem in the surrounding water area. This is a construction method that can further shorten the construction period of on-site construction, and has a great effect when applied to the following location conditions.

In the case where the soil of the underwater ground is soft and the water depth is relatively shallow (seaside part). The body unit that forms the artificial ground body is securely supported mainly by piles on the support layer below the bottom of the water floor, or the bottom of the body is supported on the bottom of the water with soft bottom, so the soil of the bottom of the water is soft. However, no sinking occurs. In addition, since a horizontal bottom plate is provided for a case in which a bottom plate is supported on a submerged ground without using a pile, the horizontal displacement does not occur due to a horizontal load during an earthquake or the like.

A place where there is running water, such as an estuary or a shore. The box unit, which forms the artificial ground frame, has a space through which water can pass, so even if it is installed at the river mouth and narrows the river width, it does not impede the flow of water under the artificial ground, so there is no possibility of flooding. In addition, there is no change in the flow condition of river water or tidal current in the water area around the estuary or the shore, and there is no adverse effect on the environment that disturbs the ecosystem of aquatic organisms such as fish and shellfish.

In the case of expansion of existing facilities and structures such as airports. Because the body of the artificial ground is fixedly supported,
Unlike Floating Artificial Ground, the level does not change due to tidal changes or overburden load, and there is no step that fluctuates with existing facilities and structures. When the bottom plate and the side plate of the box unit are formed by fixing a stiffener made of a steel plate to an outer shell made of a steel plate, the weight of the box unit can be reduced and large buoyancy can be easily obtained. When the bottom plate and the side plate are made of a shell material made of a steel plate, corrosion-resistant maintenance-free can be achieved by lining a submerged portion, a tidal portion, and a splash portion on the surface of the box unit with a corrosion-resistant metal sheet.

Further, in the method for constructing artificial ground according to the present invention, since the box unit is manufactured in a land yard or a dock in a state close to a completed form and towed to the site for installation, the construction period of the site construction can be shortened. . Further, since the box units are joined to each other by landing on the leveled underwater ground, the work can be performed easily and reliably.

[Brief description of the drawings]

FIG. 1 is a partial perspective view of an embodiment of an artificial ground according to the present invention.

FIG. 2 is a perspective view of a first example of a box unit (pile support type).

FIG. 3 is a perspective view of a second example of the box unit (soft bottom type).

FIG. 4 (a) is a cross-sectional view of the upper plate when the box unit has a steel shell structure. (B) is a sectional view of the bottom plate when the box unit has a steel shell structure.

FIG. 5 is a cross-sectional view of an example of a connection structure between a bottom plate and a pile (steel pipe pile).

FIG. 6 is a joining diagram of the box unit.

FIG. 7 is an enlarged sectional view of a portion (c) of FIG. 6;

FIG. 8 is a perspective view of an example in which the artificial ground of the present invention is installed at an estuary.

FIG. 9 is a perspective view of an example in which the artificial ground of the present invention is installed at a seaside part.

FIGS. 10A and 10B are first and second process diagrams according to the artificial ground installation method of the present invention.

FIGS. 11A and 11B are third and fourth process diagrams according to the method of installing an artificial ground according to the present invention.

12A and 12B are fifth and sixth process diagrams according to the method for installing an artificial ground according to the present invention.

FIG. 13 is a perspective view of a conventional example.

[Explanation of symbols]

 Reference Signs List 1 artificial ground 2 box unit 3 upper plate 4 side plate 5 bottom plate 6 water passage space 7 pile (steel pipe pile) 8 through hole 9 horizontal resistance plate 10 water bottom ground 11 space for buoyancy adjustment 12 steel plate (steel shell) 13 stiffener 14 Injection / drainage valve 15 Concrete 16 Coupling member 17 Joining material 18 Estuary 19 Water flow 20 Seaside 21 Reverse T-shaped unit 22 Floor slab 23 Base 24 Vertical wall 25 Air chamber 26 Cover 27 Finishing material

Claims (6)

[Claims] 1. A plurality of box units, each of which is composed of a bottom plate having a space capable of adjusting buoyancy, a side plate and an upper plate located on the water surface, and having a space through which water can flow, are leveled. An artificial ground made of a water-permeable box, wherein adjacent box units are installed on the underwater ground. 2. A box unit having a plurality of through holes into which a pile can be inserted into a box unit, and installed on the underwater ground,
The artificial ground comprising a water-permeable box as claimed in claim 1, wherein the artificial ground is connected to and supported by a plurality of piles penetrating into the underwater ground through the through holes. 3. The box unit according to claim 1, wherein a horizontal resistance plate projects below the bottom plate of the box unit, and the box unit is softly settled on the leveled underwater ground. Artificial ground made of a water-permeable box. 4. The bottom plate and the side plate of the box unit are manufactured by fixing a stiffener made of a steel plate to an outer shell made of a steel plate, and a part of the inner space is filled with a filling concrete. An artificial ground comprising a water-permeable box according to any one of claims 1 to 3. 5. The artificial ground comprising a water-permeable box as set forth in claim 4, wherein a corrosion-resistant metal sheet is lined on a submerged portion, a tidal portion, and a splash portion on the surface of the box unit to prevent corrosion. 6. The following steps (1) to (7): (1) A bottom plate having a space capable of adjusting buoyancy, a side plate, and an upper plate located on the water surface, and water can be passed inside. The box unit as a space will be manufactured in the land yard or dock. (2) Excavate the water bottom ground at the place where the box unit is installed so as to have a predetermined water depth and level the ground. (3) The box unit manufactured in the land yard or dock is levitated and towed to the installation location. (4) An appropriate amount of water is injected into the buoyancy adjusting space of one or both of the bottom plate and the side plate to reduce the buoyancy, and the box unit is softly settled on the leveled underwater ground. (5) After the pile is inserted into the through hole of the box unit and penetrated into the underwater ground, the box unit and the pile are connected, or the horizontal resistance plate is projected below the bottom plate of the box unit. (6) After the second and subsequent box units are arranged adjacent to the existing box unit, the box units are joined to each other by adjusting the level. (7) After the box unit is installed on the bottom of the water, concrete is filled into a part of the buoyancy adjusting space of the bottom plate and the side plate of the box unit and is filled with the concrete. A method for constructing artificial ground comprising a water-permeable box, which is constructed by the above steps.