JP4291891B2 - Cover structure of sludge layer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a covering structure for a sludge layer, and more particularly, to a covering structure for a sludge layer installed so as to cover a sludge layer deposited on a water bottom.
[0002]
[Prior art]
For example, sludge, which is soft sludge containing insoluble organic matter, may be deposited in water areas with poor flow on the bottom of rivers, lakes, and harbors adjacent to factories. Such sludge may cause the water pollutant to elute into the water and cause deterioration of the water quality. Therefore, according to the conventional method, such a water pollutant is coated with a layer of sand, for example. Elution is prevented.
[0003]
[Problems to be solved by the invention]
However, according to the conventional method of covering sludge with sand, the sand has a water permeability of about 10 ⁻² to 10 ⁻³ cm / sec. It is necessary to secure a thickness of about 30 cm, and sand is poured into water to form a sand layer. Therefore, in consideration of construction accuracy, a thickness of about 50 cm is actually secured. It is necessary to construct.
[0004]
Therefore, since a sand layer with such a large thickness is formed on the bottom of the water, the effective water storage amount is reduced and the necessary water depth cannot be secured, and a large amount of sand is required in consideration of the loss during construction. There was a problem of becoming uneconomical.
[0005]
In addition, it is conceivable to use fine-grained soil such as viscous soil with a low hydraulic conductivity as an alternative material for covering sand, but there are problems such as water pollution during construction, re-mudging in water, and poor workability. It was.
[0006]
Therefore, the present invention has been made by paying attention to such a conventional problem, and can reduce the thickness of the layer covering the sludge and easily ensure the effective water storage amount and the necessary water depth, The object of the present invention is to provide a sludge layer covering structure that can be constructed economically and easily without using a large amount of earth and sand.
[0007]
[Means for Solving the Problems]
The present invention has been made in order to achieve the above object, the gist is a covering structure of the sludge layer which is placed over the sludge layer to be deposited on the sea bed, the interior of the bag body, 74 microns or less The sludge is characterized by laying a mat-like member including fine-grained soil having a grain size of 50% or more and a water permeability coefficient of 10 ⁻⁴ cm / sec or less on the surface of the sludge layer. In the covering structure of the layer.
[0008]
Here, as the bag body, for example, a woven or non-woven fabric or the like, It is permitted to use those that do not flow out fines soil is content.
[0009]
Moreover, it is preferable that the covering structure of the sludge layer of this invention plants aquatic plants on the surface of the said mat-shaped member.
[0010]
In order to vegetate such aquatic plants, for example, it is possible to easily form vegetation by encapsulating plant seeds in fine-grained soil, and germinating and growing the plant seeds. it can.
[0011]
According to the covering structure of the sludge layer of the present invention, the fine-grained soil has a low water permeability of, for example, about 10 ⁻⁴ cm / sec and is applied to the top surface of the sludge layer without flowing out by the bag. Since the covering layer is formed and held, even if the thickness is reduced, elution of water pollutants from the sludge layer can be easily suppressed, and the thickness can be, for example, about 10 cm.
[0012]
Moreover, if an aquatic plant is vegetated on the surface of the laid mat-like member, the aquatic plant has a property of absorbing substances that cause eutrophication of water quality such as nitrogen and phosphorus. Therefore, it becomes possible to demonstrate the effect of improving the water quality.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The covering structure 10 of the sludge layer according to the present invention is installed so as to cover the sludge layer 11 deposited on the bottom of the water. The mat-like member 14 includes a fine-grained soil 13 inside a bag body 12 made of a woven fabric or a non-woven fabric. Is laid on the surface of the sludge layer 11.
[0014]
Moreover, according to this embodiment, since the fine-grained soil 13 stuffed inside the bag body 12 contains seeds of aquatic plants, the surface of the mat-like member 14 has aquatic plants 15 as time passes. Will be vegetated.
[0015]
Here, the bag body 12 has a planar shape having a width of about 2.0 m and a length of about 5.0 m, and the width is stopped so that the thickness of the inner space is about 10 cm. By filling and rolling the fine-grained soil 13 such as cohesive soil into the inside, the hydraulic conductivity of the fine-grained soil 13 is made smaller than 10 ⁻⁴ cm / sec, and by filling the fine-grained soil 13 in this way, A mat member 14 having a width of about 2.0 m, a length of about 5.0 m, and a thickness of about 10 cm is formed.
[0016]
In order to lay such a mat-like member 14 so as to cover the sludge layer 11, for example, the mat-like member 14 transported by a trolley or the like is lifted by a crane or the like and is submerged in water, and guided by a diver. However, by performing the laying work, it can be easily laid and installed at a predetermined position.
[0017]
Further, in order to prevent the mat-like member 14 laid in this way from being lifted or laterally moved, a grating 16 as a weight is appropriately installed on the surface of the mat-like member 14 or a work for driving a pile is performed. .
[0018]
And according to the covering structure of the sludge layer 11 of this embodiment provided in this way, the fine-grained soil 13 stuffed inside the bag body 12 has a low water permeability coefficient of about 10 ⁻⁴ cm / sec, for example. In addition, since the contact with water itself is restricted, even if the thickness of the mat-like member 14 covering the sludge layer 11 is about 10 cm, the water quality deteriorates such as water pollutants from the sludge layer 11. The elution of the substance causing the above can be easily suppressed.
[0019]
Moreover, since the aquatic plant 15 is vegetated on the surface of the mat-like member 14 laid, it absorbs substances that cause eutrophication of water quality such as nitrogen and phosphorus and other substances that cause deterioration of water quality. Or decompose to exert an effect of improving water quality.
[0020]
Therefore, according to this embodiment, the thickness of the covering layer covering the sludge layer 11 can be reduced, and an effective water storage amount and a necessary water depth can be easily secured, and economical without using a large amount of earth and sand. And it becomes possible to construct easily.
[0021]
In addition, this invention is not limited to the thing of the aspect of the said embodiment, A various change can be employ | adopted within the range of the structure described in each claim. For example, it is not always necessary to vegetate the aquatic plant 15 on the surface of the mat-like member 14, and in order to cover the sludge layer 11 with the mat-like member 14, the mat-like member 14 previously filled with the fine-grained soil 13 is set down. In addition to the method of laying down, it is also possible to employ a method of injecting the fine-grained soil 13 into the bag body 12 that is previously installed covering the sludge layer 11.
[0022]
【The invention's effect】
As described above in detail, the covering structure of the sludge layer of the present invention is configured by laying a mat-like member containing fine-grained soil inside the bag body on the surface of the sludge layer. By reducing the thickness of the covering layer, it is possible to easily secure an effective water storage amount and a necessary water depth, and it is possible to construct economically and easily without using a large amount of earth and sand. And the thickness of the mat-like member which covers the sludge layer by using a soil component having a particle size of 74 microns or less occupying 50% or more as a fine-grained soil and having a water permeability coefficient of 10 ⁻⁴ cm / sec or less. Is about 10 cm, elution of substances causing water quality deterioration such as water pollutants from the sludge layer can be easily suppressed.
[0023]
Moreover, if an aquatic plant is vegetated on the surface of the laid mat-like member, the aquatic plant has a property of absorbing substances that cause eutrophication of water quality such as nitrogen and phosphorus. Therefore, the water quality improvement effect can be exhibited.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the configuration of a sludge layer covering structure according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Covering structure 11 Sludge layer 12 Bag body 13 Fine grain soil 14 Mat-like member 15 Aquatic plant 16 Grating

Claims (2)

It is a covering structure of a sludge layer that is installed over a sludge layer that accumulates on the bottom of the water, and the soil component with a particle size of 74 microns or less occupies 50% or more inside the bag , and the hydraulic conductivity is 10 ⁻⁴ cm. The covering structure of the sludge layer characterized by laying the mat-like member containing the fine-grained soil which is below / sec on the surface of the sludge layer.   2. The sludge layer covering structure according to claim 1, wherein aquatic plants are vegetated on the surface of the mat member.

Images