JPH0414209B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sludge reclamation method in which sludge is reclaimed while being consolidated and drained using osmotic force.

(Conventional technology) In the conventional sludge reclamation method, a certain area of water is divided by a seawall, and sludge (soft soil) from the ocean floor, which has been sucked up along with water by a dredging device, is poured into the divided reclaimed area through a pipeline. Then, the sludge is allowed to settle within the landfill, and the supernatant is drained out, thereby creating a landfill using the sludge.

(Problem to be solved by the invention) However, in the conventional sludge landfill method, the dredged sludge contains a large amount of water, which increases the volume of the sludge, making it difficult to dispose of the sludge satisfactorily even in large-capacity landfills. In addition to the problems, reclaimed land exhibits a very soft ground condition when it is first reclaimed, and in order to use it as land, it is necessary to improve the ground using paper drain methods, etc., and it takes a considerable period of time to improve the ground. In addition, it is necessary to bring equipment for ground improvement into the reclaimed land, and for this purpose, the surface of the reclaimed land is generally covered with sandy soil, but it takes two years until the bearing capacity is generated to be able to carry out this work. The problem was that the sludge landfill had to be left alone for a long period of time and had to wait for the surface of the reclaimed land to dry in the sun, resulting in a very long period of time before the sludge reclaimed land could be used as land.

It is an object of the present invention to be able to dispose of a large amount of sludge in a landfill with a limited volume, and also to be able to efficiently drain the reclaimed sludge from the ground while reclamation. The purpose of the present invention is to provide a sludge reclamation method that can be used as a sludge reclamation method.

(Means for Solving the Problems) The sludge reclamation method according to the present invention forms a seawall 2 on a lower drainage sand layer 3, and a water-blocking layer 4 is formed on the inner wall surface of the seawall 2 along the wall surface. A vertical drainage layer 5A continuous to the lower drainage sand layer 3 is provided on the surface of the impermeable layer 4, and a first horizontal drainage sand layer 6A is provided on the reclaimed bottom surface inside the revetment 2. , the first horizontal drainage sand layer 6A is connected to the vertical drainage layer 5A, sludge is reclaimed thereon to form a first precipitated sludge layer 7A, and then water is poured into the reclaimed land to raise the water level to the above level. The water level is raised higher than the water level outside the seawall 2, and water permeates from the upper surface to the lower surface of the first precipitated sludge layer 7A by the osmotic pressure generated by the water level difference between the inside and outside of the seawall 2, and this permeated water is transferred to the First horizontal drainage sand layer 6A, vertical drainage layer 5A,
A second horizontal drainage sand layer 6B is provided on the first settled sludge layer 7A which is continuously drained to the outside of the seawall 2 through the lower drainage layer 3 and osmotic-consolidated by the permeated water, and then a second horizontal drainage sand layer 6B is provided. Sludge is reclaimed on the sand layer 6B in the same manner as above to form a second precipitated sludge layer 7B.
The water level inside the reclaimed land is made higher than that outside the seawall 2, and the precipitated sludge layer is consolidated by osmotic consolidation using the water level difference, and thereafter horizontal drainage sand layers and precipitated sludge layers are alternately formed in the same manner. The sludge reclamation method is characterized by proceeding with the reclamation to a predetermined height, and then draining the water accumulated in the reclaimed land.

(Function) In this way, the drainage sand layer 3 under the seawall and the vertical drainage layer 5
A to 5C, horizontal drainage sand layers 6A, 6B... are provided,
When sludge is reclaimed on the horizontal drainage sand layers 6A, 6B... inside the rear revetment 2 and the water level is raised higher than the water level outside the revetment 2, the horizontal drainage sand layers 6A, 6B... 6B..., sludge layers 7A, 7B that were drained outside the seawall 2 through the vertical drainage layer 5 and the lower seawall drainage sand layer 3, and precipitated at that time.
... is gradually consolidated by osmotic consolidation, making it possible to obtain a stable reclaimed layer.

(Example) Examples of the present invention will be described below with reference to FIGS. 1 to 3.

As shown in Fig. 1, the planned location of the revetment 2 on the reclaimed surface 1 is dug down and replaced with sand, or as shown in Fig. 2, the lower revetment drainage layer 3 is formed, for example. Form to a thickness of 1 m to 3 m. A seawall 2 is placed on top of this seawall drainage sand layer 3 with stones, etc.
Build. Next, on the reclaimed surface 1 inside the seawall 2, a first horizontal drainage sand layer 6A is provided, for example, with a thickness of 15 to 40 cm, continuous with the lower seawall drainage sand layer, using a sand removal boat. At the same time, a water-blocking layer 4 is created by laying a water-blocking sheet or the like along the inner wall surface of the seawall 2.
A first vertical drainage layer 5A is provided, and the first vertical drainage layer 5A is continuous with the first horizontal drainage sand layer 6A by filling sand on the front side.
form. In this case, the height of the vertical drainage layer 5A is set lower than the first sedimentation layer 7A, which will be described later, as shown in FIG. 2A. In this state, the first sludge is reclaimed on the horizontal drainage sand layer 6A inside the seawall 2, and the water level _H1 inside the reclaimed land is raised and maintained higher than the water level _H2 outside the seawall 2. ,
Through the osmotic action that utilizes the water level difference (H ₁ − H ₂ ),
Drainage is made from the horizontal drainage sand layer 6A to the outside of the seawall 2 via the lower seawall drainage sand layer 3. At this time, the sludge is precipitated on the horizontal drainage sand layer 6A, and water permeates through the sludge to form a precipitated sludge layer 7A having a pressure of about 2 m and subjected to osmotic consolidation. Next, the next horizontal drainage sand layer 6B is placed on the precipitated sludge layer 7A, e.g.
At the same time, a second vertical drainage layer 5B is provided by connecting it to the first vertical drainage layer previously provided, and then the sludge is reclaimed on the newly formed horizontal drainage sand layer 6B. . In this case, the water level in the reclaimed land will be maintained higher than the water level _H2 outside the seawall. In order to obtain the required water level, a raised mound 8 is placed on top of the seawall 2 as shown in the figure, or the height of the seawall 2 is set to the required height from the beginning. A water-blocking layer is also provided on the raised earth 8 using a water-blocking sheet or the like (not shown). The _horizontal drainage sand layers 6A, _6B and the vertical drainage layer 5 are
A, 5B Water is drained out of the seawall 2 through the sand layer 3 under the seawall. The sludge is precipitated on the horizontal drainage sand layer 6B, and the sludge is osmotic-consolidated by the drainage to form a precipitated sludge layer 7B with a thickness of about 2 m. Then, on top of the precipitated sludge layer 7B, the next horizontal drainage sand layer 6C
A vertical drainage layer 5C is formed, and the reclamation work is repeated in the same manner.

Next, a precipitated sludge layer 7C is formed on the horizontal drainage sand layer 6C in the same manner as described above.

When the top surface of the sludge 7C reaches the planned reclamation height, drain the water accumulated in the landfill, spread a canvas sheet over the sludge 7C, and cover it with soil to a thickness of about 1 m. I do.

Raised embankment 8 can be used for covering soil.

Further, the vertical drainage layers 5A, 5B, etc. are not limited to sand, but can also be formed by laying a sheet-like drainage material, such as a resin drainage material, as shown in FIG.

(Effect of the invention) As explained above, in the present invention, a drainage sand layer under the revetment is provided under the revetment, a vertical drainage layer is provided on the inner wall of the revetment via an impermeable layer, and the reclaimed surface inside the revetment is A horizontal drainage sand layer is provided on top, and sludge is reclaimed on top of the horizontal drainage sand layer. At that time, the water level in the reclaimed land is made higher than the water level outside the seawall, so the water accumulated in the reclaimed land is drained into the sludge layer and horizontal drainage. Drainage is carried out to the outside of the revetment through the sand layer, vertical drainage layer, and under-revetment drainage sand layer, and as a result, the sludge layer is consolidated by the osmotic pressure of water, and the consolidation of each of the precipitated sludge layers is ensured during the reclamation work. It will be done.

In addition, in the present invention, since a horizontal drainage sand layer is formed between the settled sludge layers, even after the completion of the reclamation, there is no need to perform ground improvement work such as paper drain construction as in the conventional method. Consolidation of the precipitated sludge layer is completed in about two months, and a sufficiently improved reclaimed ground is obtained, so the reclaimed land can be used quickly.

Furthermore, in the present invention, since the sludge is sufficiently consolidated during the reclamation work, a larger volume of sludge than before can be put into the landfill, and in view of the fact that there are few disposal sites for sludge that has been dredged and removed for various purposes in recent years. A large amount of sludge can be disposed of at one landfill, and its effectiveness is surprising.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of implementation of the present invention;
FIGS. 2A to 2B are partial longitudinal sectional views showing intermediate steps, and FIGS. 3 and 4 are partial longitudinal sectional views showing different embodiments. 1... Reclamation surface, 2... Bank protection, 3... Bank drainage layer, 4... Impermeable layer, 5A to 5C... Vertical drainage layer, 6A to 6C... Horizontal drainage sand layer, 7A to 7C...
...Settled sludge layer, 8...Large embankment.

Claims (1)

[Claims] 1. A revetment under-drainage sand layer is formed at the bottom of the revetment in contact with the open water area, an impermeable layer is provided along the inner wall surface of the revetment, and a water-blocking layer is provided on the surface of the revetment layer that is continuous with the revetment under-drainage sand layer. A first horizontal drainage sand layer is provided on the reclaimed bottom surface inside the revetment, and the first horizontal drainage sand layer is connected to the vertical drainage layer, and sludge is deposited on top of the first horizontal drainage sand layer. A first precipitated sludge layer is formed by filling the reclaimed land, and then water is injected into the reclaimed land to make the water level higher than the water level outside the revetment so that the first precipitated sludge layer flows from the upper surface to the lower surface of the revetment. Water is permeated by the osmotic pressure generated by the difference in water level between the inside and outside, and this permeated water is continuously drained to the water area outside the revetment through the first horizontal drainage sand layer, the vertical drainage layer, and the lower drainage layer of the revetment. A second precipitated sludge layer is placed on top of the first precipitated sludge layer, which is then osmotically consolidated.
A horizontal drainage sand layer is provided, and then sludge is reclaimed on the second horizontal drainage sand layer in the same manner as described above to form a second precipitated sludge layer, and the water level inside the reclaimed land is made higher than outside the seawall to reduce the water level difference. Consolidate the precipitated sludge layer using the osmotic consolidation effect, and thereafter proceed with the landfill by alternately forming horizontal drainage sand layers and precipitated sludge layers to a predetermined height, and then drain the water accumulated in the reclaimed land. The sludge reclamation method is characterized by: