JP2744579B2 - Paddy soil structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paddy field soil structure capable of effectively preventing water from leaking to the lower ground.

[0002]

2. Description of the Related Art A paddy field has a cultivated soil layer suitable for rice cultivation on a lower ground. As is well known, in the paddy field, the surface portion of the cultivated soil layer is made into an ooze state by irrigation, and rice is planted in a flooded state.While rice is growing, water is always held on the surface. You. Therefore, as a soil structure of a paddy field, it is desired that water is not easily leaked from the cultivated soil layer to the lower ground, in other words, the upper part of the lower ground has a low permeability soil.

[0003]

However, since the underlying ground is the original soil of the land, it is not necessarily a soil having low water permeability, and sometimes has good water permeability. If the lower ground is a soil with good permeability as described above, water leakage from the cultivated soil layer to the lower ground will increase, and it will be necessary to increase the amount of water distribution, and a great deal of expense will be required, In addition, there is a possibility that the cultivation of rice may be hindered.

[0004] By the way, for example, sludge and general surplus soil discharged by excavation of the ground during construction work are conveyed to a treatment facility for treatment. In the treatment, gravel is separated and removed from the mud. , And the residue is discharged as cake-like solid clay. This solid clay has been landfilled, for example, as industrial waste. In recent years, however, it has been desired to effectively use the solid clay as a resource from the viewpoint of resource protection and environmental protection.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a paddy soil structure capable of effectively preventing water from leaking to the lower ground. At the same time, it aims to make effective use of solid clay as a resource.

[0006]

The soil structure of a paddy field according to the present invention is such that a poorly permeable layer made of solid clay is disposed below a cultivated soil layer of a paddy field.
Separation and removal of gravel from sludge and general surplus soil discharged from
Removed, neutralized and dehydrated to obtain
Those having features was constructed. in this case,
The water-impermeable layer should be provided with a thickness of 75 cm or more.
Is desirable.

[0007]

The present inventor repeatedly conducted research to effectively use solid clay obtained by separating and removing sand and gravel and water from sludge and general residual soil, and as a result, focused on the poor water permeability of solid clay. By laying solid clay beneath the cultivated soil layer of the paddy field, it was confirmed that the paddy field would have extremely low water leakage to the lower ground.

That is, since solid clay is composed of fine particles such as clay and silt, the porosity is extremely small.
Has poor water permeability. Therefore, by arranging the impervious layer made of the solid clay below the cultivated soil layer, the impervious layer prevents the water in the cultivated soil layer from leaking to the lower ground, and allows the cultivated soil layer to sufficiently retain water. The state can be obtained. In addition, if solid clay obtained from sludge discharged from a construction site or the like or general surplus soil is used to form a poorly permeable layer, resources can be effectively used. At this time, sludge and general surplus soil are generally
Because it is strongly alkaline, it is necessary to neutralize it.
More solid clay suitable for use in paddy fields.
Wear. According to the tests and researches of the present inventor, the poorly permeable layer
Provide solid clay with thickness of 75cm or more
That water leakage can be effectively prevented.
Was confirmed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. First, with reference to FIG. 2, an outline of a procedure of a process for obtaining solid clay from sludge discharged from a construction site or the like or general residual soil will be described. For example, when soil excavation is performed at a construction site, mud A such as sludge or general residual soil is discharged. For example, the following processing is performed on mud A that has been confirmed by a dissolution test to be free of various harmful substances such as cadmium, total cyanide, and PCB.

That is, the mud A is transported to the processing facility and stored in the hopper 1. Mud A stored in hopper 1
Is first sent to the trommel 2 where the gravel B having a relatively large particle size is separated and removed while being washed with fresh water. Next, the muddy water from which the gravel B has been removed is sent to the classifier 3, where the sand C having a relatively small particle size is separated and removed while being washed with water. In this case, fresh water for washing in the trommel 2 and the classifier 3 is supplied from a circulating water storage tank 4. The gravel B and the sand C are classified into various grades according to the particle size, and are used as aggregates of ready-mixed concrete.

Then, the gravel is separated and removed in this way, and the muddy water containing clay, silt, etc.
To be housed. At this time, the muddy water is generally strongly alkaline, and a primary drug such as polyaluminum chloride is added to lower the pH. With this, p
The H, neutralization treatment is performed Ru lowered to about 6-7. This muddy water is then sent to the thickener 6, where a certain dewatering process is performed. At this time, for example, a secondary medicine such as Alonflock is charged, and mud and fresh water are separated. The separated fresh water is sent to the circulating water storage tank 4.

Further, the muddy water having a reduced water content and turned into a slurry is accommodated in a slurry tank 7 and then filtered under pressure by a filter press 8 to remove fresh water. The residue becomes cake-like solid clay D. This solid clay D is composed of fine particles such as clay and silt.

The fresh water separated by the filter press 8 is also sent to the circulating water storage tank 4 via the thickener 6, and the above-described trommel 2 and classifier 3
It is used repeatedly as fresh water for washing. Thus, effective recycling of water can be achieved.

FIG. 1 schematically shows the soil structure of a paddy field 11 according to this embodiment. Here, a flat lower ground 13 for the paddy field 11 surrounded by the ridges 12 is constructed by, for example, farmland development. Then, the solid clay D obtained by the above-mentioned process of treating the mud A is spread and compacted on the lower ground 13 to form the poorly permeable layer 14. In this case, the height (depth) dimension of the water-impermeable layer 14 is, for example, 1 to 1.5 m. Further, on the poorly permeable layer 14, a soil suitable for rice cultivation is laid to form a cultivated soil layer 15.

Thus, the paddy field 11 having the soil structure in which the poorly permeable layer 14 is disposed below the cultivated soil layer 15 is formed. In this case, the height dimension of the water-impermeable layer 14 is
It is preferably 75 cm or more.
Is preferably 30 cm or more.

In the paddy field 11 having such a soil structure, the poorly permeable layer 14 is composed of solid clay D which is an aggregate of fine particles such as clay and silt, so that the porosity is extremely small. Has poor water permeability. For this reason, the water supplied to the cultivated soil layer 15 is prevented from leaking to the lower ground 13 side as much as possible by the poorly permeable layer 14, and a sufficient water holding state in the cultivated soil layer 15 is ensured. is there.

Therefore, according to the embodiment, the provision of the impervious layer 14 made of the solid clay D allows the lower ground 13 to be transferred from the cultivated soil layer 15 to the lower ground 13 irrespective of the nature of the lower ground 13. Water can be effectively prevented.
As a result, unlike the conventional paddy soil structure, the cultivated soil layer 15
Paddy field 11 that is very suitable for rice cultivation because of the advantage that the amount of water supplied to
Can be provided.

At the same time, the hardly permeable layer 14 is formed from solid clay D discharged by treating mud A discharged from a construction site or the like. The solid clay D, which has been treated as, can be effectively reused as a resource. As a result, it is possible to greatly contribute to solving the problem of securing resources and the problem of environmental protection as well as the advantage in cost.

In the above embodiment, the hardly permeable layer 14 made of the solid clay D is formed on the lower ground 13 at the time of farmland creation. The soil may be temporarily removed, and an improvement may be made such that after forming a poorly permeable layer made of solid clay, the soil is returned again to form a cultivated soil layer. Further, in the above embodiment, the soil quality of the ridge 12 was not touched. However, it is more effective to use a soil material having low water permeability in the ridge 12 as well.

In addition, the present invention is not limited to the above-described embodiment. For example, various modifications can be made to the processing step of obtaining solid clay from mud, for example, it may be appropriately changed without departing from the gist. It can be implemented.

[0021]

As is apparent from the above description, according to the paddy field soil structure of the present invention, the construction
Gravel and gravel from sludge and general surplus soil discharged from construction sites, etc.
Was treated neutralized with separated off, since the placing impermeable layer consisting resulting <br/> solid clay dehydration, can be effectively prevented leakage to the underlying ground, and this together,
If solid clay can be effectively used as a resource ,
This is an excellent effect .

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention and is a longitudinal sectional view schematically showing a soil structure of a paddy field.

FIG. 2 is a diagram showing a procedure for treating mud.

[Explanation of symbols]

In the drawing, 11 is a paddy field, 12 is a ridge, 13 is lower ground, 1
Reference numeral 4 denotes a poorly permeable layer, 15 denotes a cultivated soil layer, A denotes mud, and D denotes solid clay.

Claims (2)

(57) [Claims] Claims: 1. An impervious layer made of solid clay is arranged below a cultivated soil layer of a paddy field , wherein the solid clay is
Gravel from sludge and general surplus soil discharged from construction sites, etc.
And then neutralized and dehydrated.
The soil structure of a paddy field, characterized by the fact that 2. The water-impermeable layer has a thickness of 75 cm or more.
The soil structure of a paddy field according to claim 1, which is provided with a law .