JPS6145010A - Formation of reclamation site - Google Patents

Abstract

PURPOSE:To shorten the period of construction by a method in which soft sludge is taken in the form of lumps without causing disturbance and slowly charged into a reclamation site to form a soft sludge layer, and sand is deposited on the soft sludge layer by spraying. CONSTITUTION:Soft sludge (a) of the bottom under water is taken in the form of lumps without disturbance by the grab of a grab dredger and loaded on a soil barge to move it to a reclamation area. The soft sludge (a) is slowly dropped onto the bottom under water in the reclamation area to form a soft sludge layer. Sand (b) is sucked up by a pump ship 3, supplied through a sand feed pipe 6 into the pipe 4 of a sand discharge pipe 5, and sprayed onto the soft sludge layer for deposition.

Description

[Detailed Description of the Invention] The present invention relates to a method for creating a reclaimed land, in particular, dividing a certain area of a lake by a seawall, filling the divided area with soft mud, and then compacting it with sand. This invention relates to a method for creating a reclaimed land in which the ground is formed by improving the handling of soft mud and its construction method, as well as the construction method for sand.

Reclaimed land is created by reclaiming certain areas of oceans and lakes. This type of reclamation can be done by dumping industrial waste into a landfill area, but there is also a dredging method in which soil taken from the ocean floor, river bed, or lake bed is dumped into a landfill area. The method is also widely used.

In this case, if the sand on the seabed, riverbed, or lakebed is hard, a pump boat with a cutter is used to loosen it, and even if the loosened material is sucked up and placed in a landfill area, its specific gravity is still low. Because it is large, it naturally settles and accumulates quickly, so the formation of the ground occurs quickly. Even if this is replaced by fine sand, it settles quickly and the ground can be formed quickly. However, although it is desirable to perform landfilling using only high-quality soil mixed with an appropriate amount of clayey soil, it is usually difficult in reality to secure a dumping site for clayey soil and perform landfilling using only high-quality soil. However, a large amount of soft mud is also used as landfill soil.

However, with the method of extracting this soft mud using a conventional pump-type dredger and depositing it in a reclaimed area, the soft mud fluidizes when the pump dredge sucks the soil into a slurry. In other words, soft mud is composed of silt, clay, and other colloidal sediments, which were originally suspended or floating in water and then settled and deposited over a long period of time. The layers have been compacted over time, resulting in mud particles that are loosely bound to each other and can be extracted as chunks. However, when a large force is applied to this clod, the loose bonds between the particles break down and the particles break apart, making the mud more likely to become fluid.

When this fluidized mud is introduced into a landfill area by a pump ship, the volume of the mud has expanded, for example, by several times, so that it occupies a large proportion of the landfill area, which reduces the volume of subsequent soft mud input. As a result, other soft mud cannot be added until the previously introduced soft mud has settled. Moreover, when such slurry water is poured into a landfill area, the mud particles are suspended in the water and do not easily settle, resulting in a significant slowdown in the rate of soil formation. It would take many years for this settled mud to have the same compacted structure as the mud that formed the original ground.

Therefore, in order to form a solid ground with this soft mud,
It is also possible to place a layer of sand with a high specific gravity on top of the piled up soft mud and press the soft mud layer with this layer of sand.
In this case, the sand is often blown out at one location in the reclaimed area, so the blown out sand with a high specific gravity may push the soft mud with a low specific gravity to the upper layer.
For this reason, not only does the soft mud have to settle again, but
There are places where the sand layer and soft mud layer are reversed, and it takes a long time to make the soft mud layer dense as mentioned above.
There are places where the thickness of the soft mud and sand layers is uneven, and it takes a lot of time to correct them.

In this way, the method of adding soft mud, letting it settle to the bottom of the water, and then compacting this soft mud with sand to form the ground takes, for example, one year to add soft mud. It takes several months for the mud to settle, and then several months to improve the ground with sand, making the construction process longer. If it takes time to prepare the reclaimed ground in this way, it not only results in poor work efficiency and a heavy burden on the construction contractor, but also results in delays in the effective use of the reclaimed land, resulting in a large loss in terms of economic effects.

In this case, even if you try to shorten the construction period by sucking up soft mud and sand at the same time using a pump ship and putting them into the landfill area together, only the sand with a higher specific gravity will settle first, and the surface layer of the reclaimed land will be covered with soft mud. As a result, the ground tends to be soft, making it unsuitable as a site for a heavy building, which is undesirable.

Furthermore, in the case of the conventional dredging and reclamation method, polluted water may flow out of the reclamation area along with drainage of surplus water, polluting the outside world, for example, the ocean.

Because of this, it is possible to immediately carry out ground improvement work with sand without allowing the soft mud to settle, and to move the soft mud to the landfill area without turning it into a slurry so as not to pollute the outside world. Development of a method for creating a reclaimed land that can create a solid reclaimed land that does not cause the layer to reverse with the sand layer, and also prevent soft mud and sand from being skewed and forming a reclaimed layer due to sand blowing out. It was wanted.

As described above, the present invention aims to improve the problems of the conventional method of reclaiming land using soft mud and compacting it with sand to create a reclaimed land.
The soft mud is moved and put in such a way that the structure of the soft mud does not collapse, and then a layer of sand is layered on top of the soft mud pile by multi-point blowing to compact the soft mud layer, thereby improving the efficiency of the construction work of the reclaimed land. At the same time, it was possible to obtain reclaimed land with solid ground.

Next, one embodiment of the present invention will be described based on FIGS. 1 to 4.

FIG. 1 is a diagram showing the state in which soft mud from the ground that has already formed the ground on the seabed or river bed is taken out and loaded onto an earth transport vessel, and the grab 1 is installed at the tip of the crane 1a of the grab vessel
By b, the soft mud a from the water bottom is collected without disturbing its structure, and this soft mud is loaded onto the earth transport vessel 2 by the rotation of the crane 1a. At this time, the soft mud is loaded onto the ship quietly so as not to disturb its structure. In this way, the soft mud is sequentially loaded into the earth transport vessel 2, and when this vessel is full,
This ship will be moved to the reclaimed area as shown in Figure 2.

The bottom of the moved earth carrier is opened and the loaded soft mud is dumped onto the water bottom. At this time, drop the lumps of soft mud individually so that they fall naturally as quietly as possible. This process is carried out one after another in all parts of the landfill area, and the soft mud is spread everywhere so that there is no place where the soft mud will not be dumped. By repeating this process, the soft mud layer is gradually heaped up as much as possible by the soil transport vessel 2.

Then, as shown in FIG. 3, the sand is sucked up by the pump ship 3 and the sand is blown into the reclaimed area. That is, as shown in FIG. 3, a sand discharge pipe 5 is formed by connecting pipes 4, 4, etc. at both ends with a gap between them, and a sand transport pipe 6 is connected to one end of the pipe. The sand sucked up by the pump ship 3 is supplied to the sand pipe 6 of the lever. In this way, the sand flows through the sand pipe 6 and is pushed out from its end. A part of this extruded sand leaks out from the gap between the sand pipe 6 and the adjacent pipe 4 at the end of the sand discharge pipe 5, and is scattered on the soft mud layer in the reclaimed area. In this way, the sand is blown off. On the other hand, the remaining part of the pushed out sand is sent to the next adjacent pipe 4, and as in the case above, a part of it leaks and is blown away, and the remaining part is further sent to the next adjacent pipe 4. sent to.

Thereafter, similar leakage blowing is performed from the gaps between other pipes as well.

Sand is sprayed in this way, and in order to spray sand to all parts of the reclaimed area, piping is installed as shown in FIG. 4. That is, sand discharge pipes 5.5... are branched and connected in parallel to the sand conveyance pipe 6 shown in FIG. The sand discharge pipes 5a, 5a, . . . , 5b, 5b, . . . are branched and provided.

In addition, 7 is a seawall.

When sand is leaked and blown from such sand discharge pipes 5.5..., 5a, 5a... and 5b, 5b, etc., the same procedure as above is applied to the entire area between the pipes 4 and 4 shown in Fig. 3. You can also scatter sand, but if you do this, the sand scattered from adjacent gaps may overlap and a large amount of sand may fall onto the soft mud layer at once, and if this happens, the relatively light soft mud will The impact of the sand causes it to rise to the upper layer, so spray every other gap, and when this cycle has been completed, spray again in the opposite direction to the previous one. It is more preferable to layer them one after another. At this time, in the gaps where no leakage occurs, the flanges of adjacent pipes may be brought into close contact with each other and bolted.

When sand is sprinkled on the soft mud layer as described above, the sand particles will fall into the soft mud layer in pieces, so the soft mud will not be thrown up, and since sand has a higher specific gravity than the soft mud, it will spread between the soft mud clods. It penetrates into the soft mud and expels that much water, and this expelled water rises through the gaps in the sand by capillary action and is removed. In this way, the structure of the soft mud becomes denser, and the sand is bound together by the sticky soft mud component, making the soft mud layer stronger.

Next, another embodiment shown in FIGS. 5 and 6 will be described.

FIG. 5 shows the installation state of the piping 5', in which the reclaimed area is divided into small areas by the base-like piping 5', and sand is blown out for each division. The distance between opposing sides of each section of piping is, for example, 50 to 150.
It is located within m.

With this piping condition, if sand is blown out from multiple points as shown in Figure 3, the large sand particles will settle out as shown in Figure 6.
; Because sand velocity is fast, sand tends to accumulate near the blowout point, and for this reason, (lJt tl) is formed, and sand with a slow settling speed accumulates in the far direction.And as the sand blowout continues, the sand The tips of the sand deposits extend far away, and the tips of the sand deposits blown out from the blow-off points on opposite sides of the pipe approach each other, creating a deposit layer that forms four parts in the shape of an inverted oblate pyramid. The four parts of this sedimentary layer are leveled with the surrounding sand to create a created area.
5'a is a receiving frame.

Forming the reclaimed ground in this way not only saves on piping, but also consolidates the soft mud at the bottom. The degree of consolidation is such that, for example, the sand deposit layer at the second sand blowout point of the soft mud layer is 2.5 m long, and the tip of the sand deposit layer is 2.5 m long.
In the case where the sand extends far away, the water content of the soft mud at the point, middle and tip of the sand is 50-60%, 60-80% and 70-90% of the solid content, respectively.
The soft mud has a denser structure compared to the original pile where the soft mud was taken out before it was spread, where the water content is 100% of the solid content.

In addition, in Fig. 5, the piping is arranged in the shape of the base plate, but in Figs.
As shown in Figure 9, the subdivisions of the landfill area are divided into parallel pipes of 5°, U-shaped pipes of 5°, and orthogonal pipes of 5°.
It may be classified according to 1.

According to the present invention, soft mud is poured into a landfill area without disturbing its structure to form a soft mud layer, and a layer of sand is further formed on top of this soft mud layer by multi-point blowing. Since there is no outflow to the outside world, the formation speed of the soft mud layer can be increased, and the strength of the ground can also be increased. This will improve the efficiency of the landfill work and shorten the construction period. In particular, compared to the conventional method of creating a landfill by dredging, not only is there no need for a period for settling soft mud, but the soft mud layer that forms the ground retains its original compacted structure. The construction period for consolidation with sand can be shortened, and after forming a soft mud layer, the construction period for consolidation with sand, which conventionally required six months, ie, the period for soil improvement work, can be shortened to one month, for example. As a result, the reduction in the construction period required for mud settling in the conventional method and the reduction in the construction period for ground improvement using this sand means that if the construction period for the conventional method of creating a dredged and reclaimed land is, for example, two years, approximately This means that a landfill can be created in half the time of 1a month.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a part of the apparatus used in one embodiment of the method of the present invention, FIG. 2 is an explanatory diagram of another part of the apparatus, and FIG.
The figures also include some other explanatory diagrams, Figure 4.
The figure corresponds to FIG. 4 in another embodiment, FIG. 6 is an explanatory diagram corresponding to FIG. 2 of the ground formation process in this embodiment, and FIGS. 7 to 9 each correspond to still another embodiment. FIG. 4 is a diagram corresponding to FIG. 4 in FIG. In the diagram, 1 is a grab ship, 2 is an earth carrier, 3 is a pump ship, and 5.
5a, 5b, 5゛, 5゛, 5pa, 5+111 are sand discharge pipes, a is soft mud, and b is sand. Figure 1 Figure 2

Claims (2)

[Claims] (1) Collect the compacted soft mud that forms the ground at the bottom of the water without disturbing it as a clod, load it onto an earth transport ship without disturbing it, and gently place the loaded clod in the reclamation area. A multi-point sand blowing device is provided above this layer to blow out sand at multiple points, and the sand blown out by this multi-point sand blowing device is deposited on the soft mud layer. A method of creating a reclaimed land characterized by forming a compacted ground. (2) The multi-point blowing device is composed of sand discharge pipes that blow sand from multiple locations, and the sand discharge pipes are piped to divide the reclaimed area into small areas, and the sand blowing points of the pipes are placed at locations spaced apart from each other. 2. The method of creating a reclaimed land according to claim 1, wherein the sand is provided so that when the sand is blown out, the tips of the sand piles overlap or are close to each other.