JP2559460B2 - Filtration drainage device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an embankment slope, a ground,
The present invention relates to a filtration / drainage device used in residential areas.

[Conventional technology]

In recent years, in order to prevent excessive water pressure in soil structures such as soft ground and the back of a retaining wall in civil engineering work, a filter drainage device for burying a fiber filter and filtering and draining has been widely used.

It is known that when filter drainage is performed by this filter drainage device, a filter cake layer is formed in the following process.

(1) In the initial stage, the fiber filter prevents the water in the soil from being naturally drained and prevents the water pressure in the soil structure from becoming excessive. In this process, large particles do not flow through, but fine particles flow along with water through the gaps of the fiber filter.

(2) Next, when this natural drainage is satisfactorily fiberized, a large particle of soil remaining on the outer surface of the fiber filter gradually forms a layer having a bridge structure (bridge layer).

(3) Next, when this bridge layer is formed,
By reducing the water contained in the soil particles behind the bridge layer, a stable soil layer (filter cake layer) is gradually formed on the outer surface of the bridge layer.

(4) When this filter cake layer is sufficiently formed 6 months to several years after embedding the fiber filter, water flows through the filter cake layer, but soil particles, even fine particles, flow through the filter cake layer. It will be difficult. Not only does this process prevent the water pressure in the soil structure from becoming excessive, but the particle characteristics of the soil in the soil structure are also maintained constant.

As is clear from the above process, the important function required for the fiber filter used in the filtration / drainage device is not only to filter and drain the water in the soil but also to provide a good period until the filter cake layer is sufficiently formed. It is necessary to maintain proper filtered drainage.

However, when the fiber filter used in the conventional filtration and drainage device is used for a long period of time, soil particles adhere to the surface or the voids, so that it is easy to cause clogging and clogging. Since the backflow or turbulent flow of the wastewater occurs near the fiber filter due to this soaking or clogging, the filter cake layer is not sufficiently formed, and the soil particles move, and in extreme cases, the ground moves or sinks. It caused the destruction of the soil structure such as.

[Problems to be Solved by the Invention]

The present inventors have used a fiber material containing a specific water-soluble fiber as a fiber filter in a filtration and drainage device for burying a fiber filter and filtering and draining the water-soluble fiber after burying to be gradually dissolved and removed by natural drainage. As a result, a new gap is formed in the fiber filter, so it is difficult for the soil particles to cause clogging and clogging, and as a result, a stable filter cake layer is sufficiently formed to maintain good filtration and drainage. It was found that the present invention was achieved.

[Means for solving the problem]

That is, the present invention is characterized by using a fiber material containing a water-soluble fiber having a melting temperature in water of 25 ° C. or more as a fiber filter in a drainage device for filtering and draining water by burying a fiber filter in a soil structure. It is a filtration drainage device.

The fiber filter used in the filtration / drainage device of the present invention is embedded in a soil structure such as soft ground or a rear portion of a retaining wall to perform filtration / drainage.

The fiber material used as the fiber filter needs to include water-soluble fibers having a melting temperature in water of 25 ° C or higher. Examples of the water-soluble fiber include water-soluble vinylon fiber having a dissolution temperature in water of 25 ° C. or higher, alginic acid fiber, and pullulan fiber, and the water-soluble fiber can be arbitrarily set and can be stably obtained. Vinylon fibers are preferred. Fibers having a water-soluble fiber dissolution temperature of 25 to 95 ° C. are preferred.

When natural drainage is performed by the embedded fiber filter, a filter cake layer is formed through the following steps.

(1) Initially, the water in the soil is naturally drained by the fiber filter. The thickness of the fiber filter is usually 2 to 30 cm
It is a degree. In this process, large particles of soil do not flow through, but fine particles flow along with water through the pores of the fiber filter.

(2) Next, since this natural drainage is favorably maintained for a long period of time, due to the large particles of soil remaining on the outer surface of the fiber material,
A layer having a bridge structure (bridge layer) is gradually formed.

(3) Next, as the bridge layer is formed, the water contained in the soil particles behind the bridge layer decreases, so that a stable soil layer (filter cake layer) is gradually formed on the outer surface of the bridge layer. Is formed. The layer thickness of the bridge layer is usually about 3 to 20 cm.

(4) Usually 6 months after embedding the fiber filter
When the filter cake layer is sufficiently formed after several years, water flows through the filter cake layer but soil particles, even fine particles, are hard to flow through. The layer thickness of the filter cake layer is usually about 3 to 20 cm. Only when this process is reached, not only is the water pressure in the soil structure excessively prevented, but also the soil properties in the soil structure are maintained constant.

In the above process, if the fibrous material used for the fiber filter contains water-soluble fibers having a melting temperature in water of 25 ° C or higher and less than 25 ° C, the water-soluble fibers will be dissolved in a short time after burying. Since it is removed, the fiber filter is likely to be clogged or clogged thereafter, which causes backflow or turbulent flow of the drainage and cannot reach the step (4). If the fiber material using the fiber filter does not contain water-soluble fibers, the fiber filter is likely to be clogged or clogged, which causes backflow or turbulent flow of the wastewater to reach the process (4) above. I don't get it. On the other hand, if the fibrous material used for the fiber filter contains water-soluble fibers with a melting temperature in water of 25 ° C or higher, the water-soluble fibers will gradually dissolve and be removed over a long period after embedding. Also gradually expands and is unlikely to cause bleeding or clogging, and thus the process (4) above can be reached completely. The fiber material used for the fiber filter may or may not contain a non-water-soluble fiber in addition to the water-soluble fiber, but from the viewpoint of economy and handleability, it is preferable to include the drainage-soluble fiber.

Non-water soluble fibers include natural fibers such as cotton and hemp, recycled fibers such as rayon, semi-synthetic fibers such as acetate, nylon,
Examples thereof include synthetic fibers such as vinylon, polyester, and acrylic.

When these water-soluble fibers and water-insoluble fibers are used in combination, both are mixed in the state of raw materials, mixed and spun, mixed twisted, mixed woven, mixed knitted, etc. to be uniformly mixed and used.

When these water-soluble fibers and water-insoluble fibers are used in combination, the mixing ratio of the water-soluble fibers differs depending on the water-filled state of the fiber-filter buried portion, the woven fabric of the fiber filter, etc., but generally 5% by weight or more. If the water-soluble fiber content is less than 5% by weight, the effect of the present invention that the water-soluble fiber is dissolved and removed after embedding to maintain a good drainage condition tends to be reduced.

The form of the woven fabric or the like of the fiber filter is not particularly limited, and a generally known non-woven fabric, woven fabric, knitted fabric, string, filament winding, or the like is used. As the product form of the fiber filter, in consideration of handling in construction, a sheet fiber filter and a reinforcing material are used together as shown in Fig. 1 (a), and a hollow fiber filter using the reinforcing material together. It is possible to use a net-like material coated (b). In FIG. 1, 1 is a fiber filter used in the present invention, 2 is a reinforcing material (core material) having a mesh or hole structure made of polyethylene, polypropylene or the like, and 3 is a net-like cover made of polyethylene or the like.

An example of a practical form of the filtration and drainage device of the present invention is shown in FIG. FIG. 2 (a) shows a state in which the fiber filter used in the present invention is embedded substantially horizontally. In (a),
11 is the embankment, 12 its slope, and 13 is a fiber filter.
(B) of FIG. 2 is an enlarged view of the vicinity of the fiber filter 6 months to several years after the embedding of the fiber filter. In (b), 14 is a fiber filter, 15 is a bridge layer, 16 is a filter cake layer, and 17 is ordinary soil.

FIG. 3 shows another example of the practical form of the filtration and drainage device of the present invention. FIG. 3A shows a state in which the fiber filter used in the present invention is embedded almost vertically. In (a), 21 is the soil behind the retaining wall, 22 is the concrete retaining retaining wall,
23 is a drainage pipe and 24 is a fiber filter. (B) of FIG. 3 is an enlarged view of the vicinity of the fiber filter 6 months to several years after the fiber filter is embedded, and 14 to 17 are the same as (B) of FIG.

 Hereinafter, the present invention will be described with reference to examples.

Example 1 A fiber filter having a length of 1.8 m, a diameter of 15 cm, and a 2 cm square mesh-shaped cylindrical polyethylene core material coated with a nonwoven fabric made of water-soluble vinylon fiber having a melting temperature of 36 ° C. in water to a thickness of 10 cm. It was made. When this fiber filter was buried for drainage behind the soil retaining wall, the drainage condition was good even after 2 years, and when excavated on a trial basis, it was adjacent to the outer peripheral surface of the fiber filter and the outer periphery of the bridge layer and bridge layer. Adequate formation of a filter cake layer was seen adjacent to the face. In addition, the non-woven fabric used has a 45% weight loss,
No pickling or clogging due to soil particles was observed.

Comparative Example 1 When a non-woven fabric filter made of polypropylene fiber was buried in place of the non-woven fabric made of water-soluble vinylon fiber in Example 1, drainage failure occurred after about 1.5 years, and the dug non-woven fabric was soiled. Blinding with particles and clogging were observed, and formation of a bridge layer and a filter cake layer was not observed.

Comparative Example 2 Instead of the non-woven fabric made of water-soluble vinylon fiber having a water-melting temperature of 36 ° C. in Example 1, a non-woven fabric fiber filter of the same type made of water-soluble vinylon fiber having a water-melting temperature of 16 ° C. was embedded for 3 months. In the course of the process, poor drainage occurred, and the dug-up non-woven fabric had almost no original form, and formation of a bridge layer and a filter cake layer was not observed at all.

Example 2 50% by weight of water-soluble vinylon fiber having a melting temperature of 40 ° C. was used in place of the nonwoven fabric made of water-soluble vinylon fiber in Example 1.
When a fiber filter in which a core material was coated with a mixed knitted fabric composed of 50% by weight of polypropylene fiber in a thickness of 15 cm was buried in the same manner, the drainage condition was good even after 2 years, and the outer periphery of the fiber filter was excavated. The formation of a bridge layer adjacent to the surface and a sufficient filter cake layer was observed adjacent to the outer peripheral surface of the bridge layer. Further, the fiber filter dug up was not so clogged with soil particles as it was pickled. The weight loss of the knitted fabric was 28%.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, the filter drainage device which is the defect of the conventional civil engineering fiber material (geotextile) fiber filter embedding, the drainage failure by clogging and clogging of the fiber filter (filter cake due to clogging and clogging). Thus, a filtration drainage device can be obtained which solves (layer formation failure), forms a filter cake layer sufficiently, and can maintain good drainage semipermanently. Therefore, there is an effect that reinforcement work by drainage such as embankment and soft ground can be easily performed.

[Brief description of drawings]

FIG. 1 is an example of a manufacturing form of a fiber filter used in the filtration and drainage device of the present invention. FIG. 2 is an example of a practical mode of the filtration and drainage device of the present invention. FIG. 3 is another example of the practical mode of the filtration and drainage device of the present invention. In the figure, 1 ... Fiber filter, 2 ... Reinforcing material (core material),
3 …… Net-like cover, 11 …… Embankment, 12 …… Slope of embankment,
13 …… Fiber filter, 14 …… Fiber filter, 15 ……
Bridge layer, 16 …… Filter cake layer, 17 …… Normal soil, 21 …… Behind retaining wall, 22 …… Concrete retaining retaining wall,
23 ... drainage pipe, 24 ... fiber filter.

Claims (1)

(57) [Claims] 1. A filtration and drainage device for burying a fiber filter in a soil structure for filtering and draining, wherein a fiber material containing water-soluble fibers having a melting temperature in water of 25 ° C. or higher is used as the fiber filter. Filter drainage device.