JPH0711656A - Erection of artificial island - Google Patents

Abstract

PURPOSE:To provide a preferable airport in the construction cost and period in the case of construction of an artificial island for an airport in the offing. CONSTITUTION:Air bags 4 are arranged in the rooms 2 of a caisson 1 provided with a number of rooms partitioned like a lattice and opened at the upper and lower sides in order to give a buoyant force. And it is towed to the construction site of an artificial island. After water has been charged in the rooms 2 of caisson 1 to settle on the bottom, the air bagss are deaerated and removed and further, sand 11 is charged in the respective rooms 2 of caisson 1 to stably set it. This procedure is repeated to treat a number of caisssons as an outer peripheral breakwater 12 of the construction site of artificial island. In the inland sea 15 surrounded by these caissons, a number of other caissons in which no sand is charged in the respective rooms 2 are anchoraged on the bottom by repetition of these procedures. After that, concrete slabs 17 are laid down on the whole upper face of caissons 1 and fixed thereto to form the ground of artificial island.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method for constructing an artificial island,
More specifically, it relates to a method of constructing a ground portion in an artificial island for an airfield constructed on the sea, for example.

[0002]

2. Description of the Related Art Conventionally, when constructing an airfield or the like on the sea, a planned area has been filled up. In general,
When constructing an artificial island by land reclamation, a breakwater was constructed around the area to be the artificial island, that is, a section, and the area surrounded by this breakwater was filled up. The breakwater is constructed by removing mud from the sea floor and laying gravel to stabilize it, and then improving the ground. The width of the ground improvement portion is determined by the ground condition, but may be extremely large in some cases. The landfill inside the breakwater is usually done by sediment, but this landfill was constructed from a large-scale sediment collection site using an efficient transportation method.

[0003]

However, the conventional method for constructing an artificial island has a serious problem when the artificial island construction area is soft ground. That is, when a breakwater or a landfill embankment on the inside of the breakwater, that is, the inland sea, is formed on soft ground, compaction settlement and uneven settlement occur over a long period of time due to the load of the breakwater and the embankment, and the amount of subsidence is also extremely large.
Therefore, there is a problem that pretreatment for soft ground improvement is required over the entire artificial island, which is extremely disadvantageous both in terms of construction cost and construction period.

An object of the present invention is to solve the above conventional problems, and it is an object of the present invention to provide a method for constructing an artificial island which is very advantageous in terms of construction cost and construction period.

[0005]

The present invention is basically a method of constructing an artificial island, for example, an artificial island for an airfield to be constructed on the sea. To solve the above-mentioned technical problems, it is as follows. Is configured. That is, the artificial island construction method of the present invention, an air bag is arranged at the bottom of a part of a caisson provided with a large number of rooms that are partitioned in a grid pattern and open at the top and bottom, and the caisson is provided with buoyancy over the sea. Towing to the artificial island construction area, injecting water into the room of this caisson, sinking the caisson to the seabed, then deflating the air bag to remove the air bag, and throwing gravel into each room of the caisson. Stable installation, repeating this method to make a large number of the caisson as the outer breakwater part of the artificial island construction area, and in the inland sea surrounded by these outer breakwater parts, a large number of other caisson that does not throw gravel into each room The method is repeated to settle on the seabed, and then a concrete plate is laid on the upper surfaces of all the caisson and fixed to the caisson to make the ground of the artificial island.

In the artificial island construction method of the present invention as described above, the sea bottom of the artificial island construction area in which the caisson, which serves as the outer breakwater, is installed is preliminarily ground-improved and the sea bottom of the inland sea is covered with mud. After removing the gravel, gravel is spread, and the caisson that does not throw gravel into the respective rooms is installed thereon.

[0007]

According to the artificial island construction method of the present invention, a reinforced concrete caisson having a large number of compartments partitioned in a lattice shape and open at the top and bottom is prepared and prepared in advance in a caisson yard on land. An air bag or balloon is placed at the bottom of some of the caisson rooms and is pulled out to sea. The caisson pulled out to the sea is given buoyancy at least by a balloon and is towed to the artificial island construction area.

When this caisson is positioned at the outer peripheral position of the artificial island construction area, water is poured into each room and the caisson is submerged in the seabed. After that, the air in the balloon is deflated and removed, and gravel is put into each room of the caisson for stable installation. Repeating this method, a large number of caisson are made into the outer breakwater part of the artificial island construction area, and a large number of other caisson that does not put gravel into each room in the inland sea surrounded by these outer breakwater parts is repeated on the seabed by repeating the above method. After placing it in place, a concrete plate is laid over the top surface of all caisson and fixed to the caisson to form the artificial island ground.

[0009]

EXAMPLES The method for constructing an artificial island of the present invention will be described below in more detail with reference to the examples shown in the drawings. In the artificial island construction method according to one embodiment of the present invention, as shown in FIGS. 1 and 2, a reinforced concrete caisson 1 provided with a large number of rooms partitioned in a grid shape and opened at the top and bottom is a caisson yard on land in advance. It is produced and prepared in.

As is apparent from FIG. 2, there are a total of 30 chambers 2 formed in the caisson 1, and a bottom plate 3 is attached to a part of these chambers 2, that is, the bottoms of the four chambers 2. The lower part is closed. An air bag, that is, a balloon 4 is arranged at the bottom of the other room 2 and an air supply pipe 5 extending from each balloon 4 is connected to an air supply source (not shown). A valve 6 is installed in these air supply pipes 5 and is closed when the air pressure inside the balloon 4 is maintained.

The four chambers 2 in which the bottom plate 3 is arranged surrounds the center of gravity of the caisson 1, and the chamber 2 is selected at a position where the center of gravity is balanced when lifted as a whole. On the outer surface of these bottom plates 3, a power fluid device 7 is installed. The power-fluose device 7 is a device for injecting compressed air from a nozzle 8 and levitating the caisson 1 by its reaction force.

Balloons 4 are arranged in a room 2 other than the room 2 to which the bottom plate 3 is attached, and the caisson 1 in which these balloons 4 are filled with air is discharged from the nozzle 8 by the above-mentioned power fluid device 7. It is levitated from the ground surface by the injection of compressed air, and is pulled out from the caisson yard to the sea 10 along the slideway 9. The caisson 1 pulled out to the sea is the buoyancy provided by the balloon 4 itself, and each room 2 closed by the balloon 4 and the bottom plate 3.
It floats in the sea due to the buoyancy obtained from its volume. Then, the caisson 1 is towed by a tugboat or the like to a predetermined offshore artificial island construction area.

This caisson 1 is positioned at an outer peripheral position of the artificial island construction area in order to form the outer breakwater portion of the artificial island construction area, and water is poured into the room 2 of the caisson 1 at that position as shown in FIG. After the caisson 1 is submerged in the sea floor by water load, the air in each balloon 4 is gently drawn out by the operation of the valve 6 to purify it, and then each balloon 4 is removed and collected.

Next, as shown in FIG. 4, gravel 11 is put into each room 2 of the caisson 1 and stably installed so that it can withstand a wave load. Then, this method is repeated to install a large number of caisson 1 at the outer peripheral position of the artificial island construction area as shown in FIG. 5 to form the outer breakwater portion 12 of the artificial island construction area. At that time, as shown in FIG. 3 and FIG. 4, the sea bottom where these caisson 1 is installed has mud removed in advance and gravel 13 has been spread, and the lower part has ground improvement (shown by reference numeral 14). It

Thus, as shown in FIG. 5, a large number of caisson 1 are installed in the outer peripheral position of the artificial island construction area by the above-mentioned procedure in the inner side or the inland sea 15 surrounded by the large number of outer peripheral breakwaters 12. A large number of other caisson 1 in which no gravel is put into each room 2 is placed on the seabed by repeating the above-described method, and is formed as an inland sea side skeleton portion 16. At this time, as shown in FIG. 4, the bottom of the inland sea is simply laid with gravel after removing mud, and the ground is not particularly improved. The reason is that the caisson itself is not so heavy and there is no need to improve the ground because gravel or the like is not put into each room 2 of the caisson 1.

As described above, the artificial island construction area is provided in each room 2
The caisson 1, which is the outer breakwater portion 12 by being filled with gravel, and the caisson 1, which is installed in the inner sea 15 surrounded by these and is the inner sea side skeleton portion 16, are filled up. Then, after that, a precast concrete slab 17 is spread over the upper surfaces of all the caissons 1 as shown in FIG. 6, and fastened to each caisson 1 with bolts or the like.

This precast concrete slab 17
Are slightly larger than the upper surface area of one caisson 1 and are spread so as to be abutted against each other at the gaps between adjacent caisson 1 so that no gap is created between the caissons 1. As a result, the concrete slab 17 spread over and fastened to all the caisson 1 functions as the ground or floor plate of the artificial island.

In the artificial island construction method according to this embodiment, a caisson having a large number of vertically open rooms formed by partition walls is installed in the artificial island construction area, and the caisson installed on the outer periphery of the artificial island construction area at that time is installed. In each room, gravel was introduced to make this caisson a breakwater that can withstand wave loads to enhance its stability.On the other hand, in the inland sea, the caisson was installed only by its own weight. It is very effective in terms of construction period and construction cost because it is not necessary to improve the ground.

Further, in the artificial island construction method of this embodiment,
Since many caissons are installed in the inland sea and the inland sea part is not reclaimed as in the past, there is no need for large-scale sediment collection from the sediment collection site and transportation of this to the sea.
From this point of view, it is a very effective construction method.

[0020]

As described above, according to the method for constructing an artificial island of the present invention, a balloon is installed at the bottom of a caisson, which has a large number of open and closed rooms, to give buoyancy and tow over the sea. By doing so, the structure of the caisson can be made very simple. Moreover, only caisson installed on the outer circumference of the artificial island construction area is gravel-filled into the room to improve stability and form a breakwater section.Don't pour gravel into each room in the inland sea surrounded by these outer breakwater sections. Since another caisson of No. 1 is set on the seabed, it is not necessary to reclaim the inland sea with sand and sand, so that the artificial island can be constructed very effectively both in terms of construction period and construction cost.

As described above, in the artificial island construction method of the present invention, the caisson in which a large number of rooms are formed is arranged as it is, particularly in the inland sea, so that the artificial island itself has a small weight and, as a result, the soft ground. Even in this case, the total subsidence amount and the unequal subsidence amount can be reduced, and the time until the subsidence can be shortened can be shortened.

[Brief description of drawings]

FIG. 1 is a structural explanatory view schematically showing a state in which a caisson is pulled out to the sea in an artificial island construction method according to an embodiment of the present invention.

FIG. 2 is a plan view showing a caisson used in the artificial island construction method according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a state in which a caisson is installed on an outer peripheral portion of the caisson to form a breakwater portion in an artificial island construction region.

FIG. 4 is a cross-sectional view showing a state where gravel is thrown into each room of the caisson shown in FIG. 3 and a caisson to which no gravel is thrown is installed on the inward sea side.

FIG. 5 is a plan view of the artificial island construction region showing a state in which a large number of caissons are arranged on the outer periphery of the artificial island construction region to form a breakwater portion.

FIG. 6 is a cross-sectional view showing a state in which a precast concrete slab is arranged on the upper surfaces of all the caissons installed in the artificial island construction area and fastened to the caissons.

[Explanation of symbols]

 1 Caisson 2 Room 3 Bottom plate 4 Air bag or balloon 5 Air pipe 6 Valve 7 Power fruse device 8 Nozzle 9 Slideway 10 Ocean 11 Gravel 12 Perimeter breakwater section 13 Gravel 14 Ground improvement section 15 Inland sea 16 Inland sea side body section 17 Precast concrete Slab

Claims (2)

[Claims] 1. An air bag is arranged at the bottom of the room of a part of a caisson having a large number of rooms divided into a lattice and open at the top and bottom, and the sea is towed to an artificial island construction area while giving buoyancy to the caisson. Then, after pouring water into the room of this caisson and submerging the caisson to the seabed, the air in the air bag is removed and the air bag is removed, and gravel is put into each room of the caisson for stable installation. Repeat the method to make a large number of the caisson as the outer breakwater part of the artificial island construction area, and in the inland sea surrounded by these outer breakwater parts, a large number of other caissons that do not throw gravel into each room are repeated by the above method. A method for constructing an artificial island, which comprises placing the concrete caisson on the upper surface of all the caisson and fixing it to the caisson to make the ground of the artificial island. 2. The sea bottom of the artificial island construction area in which the caisson is installed as the outer breakwater is ground-reformed in advance, and the sea bottom of the inland sea is covered with gravel after removing mud. The artificial island construction method according to claim 1, wherein the caisson that does not throw gravel is installed in each of the rooms.