JPH0317002B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention is used to remove suspended fine soil particles in surface water that flows over the surface of bare land, such as reclaimed land, while eroding it during rainfall. .

<Prior Art> Conventionally, in order to remove the above-mentioned suspended fine soil particles, a method has been proposed in which surface water is collected in a pond and subjected to coagulation and sedimentation. This is not just a matter of collecting them in a pond.
This is because suspended fine soil particles electrically repel each other and do not easily settle.

<Problems to be solved by the invention> When trying to solve the problem of turbid water flowing out from bare land such as reclaimed land due to rainfall and having a negative impact on downstream areas, the conventional method of coagulation and sedimentation uses chemicals. Therefore, there are problems such as being expensive, requiring treatment of precipitates, and making the water acidic. Therefore, it has not been put into practical use.

<Means for Solving the Problems> The means according to the present invention is to arrange a vertical wall that accommodates sand by arranging engineered fiber cloth capable of retaining sand on both sides and the lower end surface so that the vertical wall is approximately perpendicular to the direction of flow of surface water. A crushed stone layer is provided under the vertical wall so as to span the upstream and downstream sides and reach the ground surface on the downstream side. A sand bed reaching the earth's surface is provided above the crushed stone layer, and engineered fiber cloth similar to the above is installed between the crushed stone layer and the sand bed, and at the boundary between the earth surface formation surface and other strata. It is.

The sand in the vertical wall and the sand bed above is standard sand, river sand,
You can use either sea sand. This sand is a concept based on the Japan Unified Soil Classification by the Japan Society of Soil Engineering.
It may be either fine sand or coarse sand or a mixture thereof, but it is required to be clean.
In addition, the above-mentioned engineering fiber cloth is a durable fiber cloth used in soil in civil engineering.
Its materials include nylon, polyester, polyethylene, polypropylene, polyvinyl chloride,
Polystyrene, etc. The roughness of the engineering fiber cloth may be such that it can retain the sand used so as not to be washed away and has good water permeability.

<Operation> According to the means of the present invention, when turbid surface water reaches the position where the fence is installed, the water passes through the sand layer and the crushed stone layer in sequence and exits to the downstream side. During this time, the sand layer traps suspended fine soil particles, thereby removing turbidity from the water. The sand layer exists in a roughly L-shape in the vertical wall and the sand bed in a cross section along the flow direction, and a crushed stone layer with better permeability than the sand layer is adjacent to it below and downstream. Since the sand layer is provided so that water flows into any position of the sand layer, it easily flows out to the crushed stone layer side. That is, surface water passes not only through the vertical wall but also through the sand bed upstream of the vertical wall.

<Example> In the figure, 1 is a vertical wall, 2 is a crushed stone layer, and 3 is a sand bed.

As shown in FIG. 3, the vertical wall 1 is installed vertically, for example, approximately along one of the contour lines 10 of the bare land that has been created, and as shown schematically in FIG.
Engineered fiber cloth 11 is placed on both the upstream and downstream surfaces and the bottom end surface, and sand 12 is placed inside to increase the permeability coefficient.
It is filled with river sand at a rate of about 10 ^-1 cm/sec. As the engineering fiber cloth 11, T1000, which is commercially available under the trade name Terram (manufactured by Imperial Chemical Industries Ltd. in the UK) and has a grain that can hold fine sand, was used. The retention of the engineering fiber cloth 11 is as follows:
As shown in the figure, pillars 13 are driven into the ground at appropriate intervals and planted, and a wire mesh 14 is stretched over the pillars 13 and sewn to the wire mesh 14 with wire. This vertical wall 1 has a height of about 1 m from the ground surface and a thickness of about 30 cm.

As shown in FIG. 1, the crushed stone layer 2 is provided under the vertical wall 1 so as to span the upstream side and the downstream side, and reach the ground surface on the downstream side. The hydraulic conductivity of this crushed stone layer 2 is approximately 10 ² cm/sec. This crushed stone layer 2 is in a state in which the entire circumference in the illustrated cross section is surrounded by the engineering fiber cloth 11.

As shown in FIG. 1, the sand bed 3 is provided on the crushed stone layer 2 on the upstream side of the vertical wall 1, and its upper surface is at the same position as the ground surface. This sand bed 3 is also made of the same river sand as described above, and in the illustrated cross section, the entire circumference is surrounded by the engineering fiber cloth 11. 11a, 11 in the figure
b is an engineering fiber cloth extending to the ground surface on the upstream and downstream sides, and is sewn to the engineering fiber cloth 11. In addition, 15 is a drain pipe, using a vinyl chloride pipe,
It slopes slightly downward from the downstream end of the crushed stone layer 2 and reaches the ground surface on the downstream side. The outlet side of this drain pipe 15 may be connected to a suitable drain. 16 is a streamline of surface water.

When turbid surface water from rain passes through this fence, suspended soil particles are captured within the sand layer and flow out as wash water. Turbid water with a turbidity of 200 to 300 becomes clean water with a turbidity of about 10 after passing through Fuens. In addition,
Since suspended soil particles are particles of clay or silt, the amount of suspended soil particles attached to Fuens sand increases as time passes, causing clogging, but crushed stone layers are similar to sand layers and other geological formations. and engineered fiber cloth, no clogging occurs, and the soil particle removal capacity is therefore restored only by replacing the sand. It is possible to use an ejector for sand replacement work.

In the above example, a wire mesh was used to hold the engineering fiber cloth, but a hard vinyl chloride plate with many small holes may also be used. A structure in which it is sandwiched between two sheets may also be used.

<Effects of the Invention> This fence for removing suspended soil particles has a suspended soil particle removal effect on both the vertical wall and the sand bed, and has a large effective water permeable area that has a turbidity removal effect compared to the height of the fence. It can cover a wide range of bare land. Moreover, since no chemicals are used to purify turbid water, the quality of the water does not change.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view of one embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 3 is a plan view of the same embodiment. 1... Vertical wall, 2... Crushed stone layer, 3... Sand bed, 1
1... Engineering fiber cloth, 13... Support, 14... Wire mesh.

Claims (1)

[Claims] 1. A vertical wall with engineered fiber cloth capable of retaining sand placed on both sides and the bottom end to hold sand inside is installed approximately perpendicular to the direction of flow of surface water, with the lower part located below the ground surface. A crushed stone layer is provided below the vertical wall spanning the upstream and downstream sides and reaches the ground surface on the downstream side, a sand bed reaching the ground surface is provided above the crushed stone layer on the upstream side of the vertical wall, and the crushed stone A fence for removing suspended soil particles, which is constructed by installing engineered fiber cloths similar to those described above between layers and sand beds, and between the surface formation surface and the boundary surface with other strata.