JPS60175611A - Reclaiming method - Google Patents

Abstract

PURPOSE:To facilitate vertical holding of a drain, by a method wherein flexible drain pipes are disposed on the bottom of the sea, a deep well is formed to lay sand, sludge is charged, water is drained through drains, and sandy earth is laid thereon. CONSTITUTION:The one end sudes of flexible drain pipes 8 are sunk, in order, on the bottom of the sea, and a drain pump 10 is located on the revetment 9 side to intercommunicate the pipes and the pump. Secondary, sand 2 is laid between the pipes 8, sludge is charged thereon to form a primary reclamation layer 12, and drains 14 are driven in the laid sand 2. With the drain pump 10 driven, a moisture content in the primary reclamation layer 12 is drained through the drains 14, the laid sand 2, the flexible drain pipes 8, and the deep well 10. This enables increasing of an amount of sludge disposed in a recalmation land, and improves a drain effect produced during driving of the drain pump.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a landfill method for filling soft mud with a high water content (hereinafter referred to as sludge) in a coastal landfill using a pump dredger or the like.

If the sludge that has accumulated on the seabed is dredged using a pump dredger, etc., and the sludge sucked up along with the water is thrown into a planned reclamation site that has divided the nearby sea area to create a reclaimed land, the reclaimed land will be extremely soft. In order to create a solid foundation and use it as land.

Naturally, the ground must be improved.

Therefore, as one of the conventional ground improvement methods, there is a method as shown in Fig. 1. This method involves placing two pieces of sand on top of the seabed in the reclaimed land.
Furthermore, a drainage pipe 3 is laid in this sand bed, and then a rope drain 4, which is a type of vertical drain used for improving soft ground, is attached with an anchor 5 at its tip, and the drainage pipe 3 is laid in the sand bed 2.
The upper end of the rope drain 4 is connected to the float 6 so that the entire rope drain 4 is held vertically, and the rope drain 4 is then placed in a landfill with water using a pump or the like on the sand 2. 1. Next, connect a vacuum pump to the drainage pipe 3 via an appropriate pipe, and operate the vacuum pump to drain the moisture in the sludge 7 to the rope drain 4.
Bedding sand 2. The reclaimed ground is improved by dewatering the drainage pipes 3 one after another.

However, the conventional method has drawbacks such as difficulty in maintaining the rope drain 4 vertically because the rope drain 4 moves due to flowing sludge and water flow during the sludge reclamation work.

The object of the present invention is to obtain a reclamation method that eliminates these drawbacks.

The reclamation method of the present invention includes a step of arranging a flexible drainage pipe on the seabed, a step of providing a deep well communicating with the drainage side of a drainage mechanism whose water absorption side is connected to the flexible drainage pipe, and A step of applying sand between the flexible drainage pipes;
A step of injecting sludge onto the litter to form a primary fill layer, and driving a drain into the sand through the secondary fill layer so that the head of the drain is buried in the secondary fill layer. a step of activating the drainage mechanism; a step of further injecting sludge onto the secondary reclaimed layer to form a secondary reclaimed layer; and a step of overturning sandy soil on the secondary reclaimed layer. It is characterized by consisting of a process.

The present invention will be described in detail below with reference to the drawings.

In the present invention, first, as shown in FIGS. 2 and 3, a flexible drainage pipe 8 is floated on the sea using a buoy or the like.
Flexible drainage pipes are arranged in a net shape on the seabed 1 by sequentially lowering one end of the pipes from the sea to the seabed. Here, the flexible drainage pipe is a pipe in which the surface of a plastic coil is covered with a coarse canvas, and is similar to a so-called drain hose that is conventionally used for the purpose of draining water near the ground surface.

Next, a drainage pump 10 is arranged on the seawall 9 side, and its water suction side is connected to one end of the flexible drainage pipe 8. A deep well 11 communicating with the drainage side is provided using the seawall 9. Apply sand 2 between the flexible drainage pipes 8.

After the construction of the sand bed 2, sludge is poured onto it using a pump dredger to form a primary reclaimed layer 12. Also, the next landfill layer 12
shall be constructed so that its top surface is approximately 3m below sea level. Next, a mandrel 15 having a stirring blade 13 and a vertical drain 14 such as a chemical board drain inserted therein is connected to the drain 14 with a cone 16 attached to its lower end.
Next, the sand is poured into the bedding 2 through the reclamation layer 12.

Here, the upper end of the drain 14 is submerged by about 1 m into the primary landfill layer 12, and then the drainage pump 10 is operated to remove moisture in the secondary landfill layer 12 from the drain 14° to the bedding sand 2.
．． Flexible drainage pipe 8. Drain through deep well 11.

Incidentally, since the upper end of the drain 14 is sufficiently buried in the primary landfill layer 12, when the drain pump 10 is operated, -
Since the water level lowering and negative pressure effects in the next reclaimed layer 12 are promoted, the increase in consolidation load (effective stress) due to these is also significantly promoted, and the improvement effect is further promoted. If the drainage pump 10 is operated for a certain period of time, the primary landfill layer 12 will be consolidated and its volume will decrease, so the operation of the drainage pump 10 will be stopped and sludge will be poured onto the primary landfill layer 12 again by a pump ship, and the secondary landfill layer 17 is formed, and then sandy soil 18 is further covered thereon. In the above, the drain pump l
The secondary landfill layer 17 may be constructed while continuing the operation of the O.

Since the construction method of the present invention is as described above, it has the following advantages.

+8) In the conventional construction method, sludge mud with a high velocity is pumped between the drains that are lined up in the water, making it difficult to hold the drains and also causing problems with the piping of the sand discharge pipe for introducing the mud, etc. Although there was a fatal flaw in construction, in the present invention, the drain is installed after the primary reclamation, so the problems in construction that occur with conventional construction methods can be solved.

(bl After installing the vertical drain 14 in the primary landfill layer 12 made of sludge, the drainage pump l of the deep well 11
By operating O, the volume of the primary landfill layer 12 is reduced, so the secondary landfill layer 1 is made up of more sludge.
7 can be constructed. Therefore, compared to conventional methods, the amount of sludge that can be disposed of in the limited volume of the landfill can be increased.

(C) Vertical drain 1 in the primary landfill layer 12 due to sludge
4, the upper end of the vertical drain 14 is buried in the next landfill layer, so that the drainage effect is good when the drainage pump 10 of the deep well 11 is operated immediately after the construction of the vertical drain 14.

(dl Flexible drainage pipes are arranged in a net shape on the bottom of the water throughout the entire area of the landfill, sand is placed between the arranged flexible drainage pipes, and one end of the flexible drainage pipes is placed close to the seawall. As a result, the deep well can be placed near the seawall.Therefore, there is no need to install drainage equipment for the deep well in a reclaimed land with poor footing.

+8) Normally, when the sea surface is filled with sludge by a pump ship, the sludge forms flocs and settles, so the volume of the accumulated sludge increases due to the formation of a skeleton by the flocs (fluff structure). Therefore, if the skeleton is disturbed to the point where it is destroyed, the soil structure becomes lower and the volume decreases, causing subsidence.

In the method of the present invention, after the primary reclamation is completed, the mandrel 15 with the disturbance H13 is penetrated from the barge and the drain 14 is driven into the bottom drainage sand layer. As a result, the ground will sink even if the sludge skeleton is destroyed. However, it is possible to increase the amount of soil to be reclaimed afterwards.

(') Since the reclaimed ground has been considerably improved before it is covered with sandy soil as the final step of the method of the present invention, it is possible to plan for early use of the reclaimed ground.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the conventional construction method, Figure 2 is a plan view showing the arrangement of flexible drainage pipes etc. used in the construction method of the present invention, Figure 3 is a sectional view explaining the construction method of the present invention, and Figure 4 is a diagram illustrating the construction method of the present invention. A front view of the lower part of the mandrel used in the construction method of the present invention, and FIG. 5 is a cross-sectional view thereof. 1... Seabed, 2... Sand, 3... Drainage pipe, 4
... Lobe drain, 5 ... Anchor, 6 ... Float, 7 ... Landfill sludge, 8 ... Flexible drainage pipe, 9 ... Seawall, 1゜ ... Drainage pump, 11・
...Deep well 512...-Next landfill layer, 13...
- Disturbing blade, 14... Vertical drain, 15... Mandrel, 16... Cone, 17... Secondary reclaimed layer, 18
...Sandy soil. 4FI mouth■ -2m

Claims (1)

[Claims] A step of arranging a flexible drainage pipe on the seabed. A step of providing a deep well communicating with the drainage side of a drainage mechanism whose water absorption side is connected to the flexible drainage pipe, a step of applying sand between the flexible drainage pipes, and pouring sludge onto the sand. forming a primary fill layer; and driving a drain into the litter through the secondary fill layer so that the head of the drain is buried in the secondary fill layer. activating the drainage mechanism; further adding sludge onto the secondary landfill layer to form a secondary landfill layer;
This reclamation method is characterized by comprising the step of overturning sandy soil on top of this secondary reclamation layer.