JPH06185068A - Method of preventive construction of change into salt water of ground water by ultra water-absorbing fiber sheet - Google Patents

Abstract

PURPOSE:To improve the efficiency of operation by burying an ultra water- absorbing fiber sheet into a trench constructed on the boundary section of ground water and salt water, extruding salt water with the lapse of time by utilizing the characteristics of water-absorbing fibers and manufacturing a waterproof wall. CONSTITUTION:An ultra water-absorbing fiber sheet 1 absorbing fresh water, being swollen to a high degree and being shrunk by salt water and an alkaline aqueous solution is buried into a trench built on the boundary section (a salt water wedge section) of ground water 3 and salt water 4. The water level of ground water 3 rises with the lapse of time and the sheet 1 is swollen and brought to a water permeable state, and salt water 4 having larger specific gravity is extruded from a sheet section 2 not swollen while the sheet 1 is downward swollen gradually, thus completing a water impermeable waterproof wall. Accordingly, the efficiency of execution can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing salinization of groundwater using a super absorbent fiber sheet.

[0002]

2. Description of the Related Art Conventionally, the following two methods have been adopted to prevent salinization of groundwater.

A steel sheet pile is driven to construct a waterproof wall.
A concrete continuous underground wall will be constructed for waterproofing.

However, in the case of (1), if the impermeable layer exists deep in the ground, the steel sheet pile cannot be driven in, making it impossible to construct a waterproof wall. In addition, water leakage from the steel sheet pile joint easily occurs, and complete waterproofing cannot be expected. in the case of,
Although it can be expected to be completely waterproof, it requires a large amount of work. Furthermore, both of them require that the salt water remaining on the groundwater side be pumped out during and after construction of the waterproof wall.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for simply and completely preventing the salinization of groundwater.

[0006]

SUMMARY OF THE INVENTION The present invention is a method for preventing salinization of groundwater by embedding a super absorbent fiber sheet in a trench constructed at the boundary between saltwater and groundwater (saline wedge). Based on the above, the characteristics of super absorbent fibers are utilized to more completely prevent salinization of groundwater over time.

The super absorbent fiber used in the present invention is, for example, a fiber having an acrylate unit and an acrylamide unit obtained by reacting an acrylonitrile polymer with an aqueous solution of an alkali metal hydroxide, polyvinyl acetate and acrylic. Copolymer fibers of vinyl alcohol and acrylate obtained by hydrolyzing a copolymer with acid ester, fibers of acrylic acid graft-polymerized on cellulose fibers, etc. ~ A fiber having a property of swelling several thousand times. These super absorbent fibers can be obtained by copolymerizing a crosslinkable monomer such as ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, N, N'-methylenebisacrylamide, or divinyl ether, or by appropriately crosslinking the fibers. A crosslinking structure may be introduced by crosslinking with an agent, radiation or the like. Further, the super-absorbent fiber may be a single-layer fiber in which the entire fiber has super-absorbency or a multi-layer fiber in which only the outer layer of the fiber has super-absorbency. Examples of commercially available super absorbent fibers include Lanseal-F (registered trademark manufactured by Toyobo Co., Ltd.).
There is.

Due to their ionic structure, these super-absorbent fibers absorb fresh water and swell to a high degree, but they have the property of shrinking with salt water or an aqueous alkaline solution. It utilizes the swelling / shrinking properties of the super absorbent polymer.

The super absorbent fiber is vertically embedded in the trench as a sheet of woven fabric, non-woven fabric, knitted fabric or the like.

The sheet can be made only from superabsorbent fibers, but can also be made by blending with other fibers (for example, various plant fibers, synthetic fibers, etc.), and is made from superabsorbent fibers. It can also be produced by laminating a sheet and a sheet made of another fiber or another water permeable material.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings.

The trench is dug from the ground surface to the impermeable layer underground, and a super absorbent fiber sheet is vertically embedded in the trench. In the initial stage of burial, the upper part of the super absorbent fiber sheet is in contact with groundwater and the lower part is in contact with salt water. The upper part of the sheet, which is in contact with groundwater, swells due to water absorption and becomes impermeable, but the lower part is permeable because it has not yet swelled. (Fig. 1) With the passage of time, groundwater is supplied and the water level on the groundwater side rises, changing the saltwater balance, pushing saltwater with a large specific gravity toward the sea side, and the contact between the seat and groundwater gradually goes down. It expands, and the impermeable part gradually expands to the lower part. (FIG. 2) This expansion of the water impermeable portion is continuously repeated, and finally the entire sheet becomes water impermeable to complete the waterproof wall.
(Figure 3)

[0013]

EFFECTS OF THE INVENTION The construction method of the present invention is simple in construction, not only does the work of pumping out salt water unnecessary, but it is also possible to reliably replace ground water with salt water.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a construction method of the present invention at the beginning of construction.

[Fig. 2] After the construction of the construction method of the present invention, some time has passed,
It is a longitudinal cross-sectional view showing a state in which the swelling of the super-absorbent fiber sheet spreads downward and salt water is pushed out toward the sea.

[Fig. 3] After the construction of the construction method of the present invention, more time has passed,
It is a longitudinal cross-sectional view showing a state in which the swelling of the super absorbent fiber sheet has spread to the bottom and the waterproof wall is completed.

[Explanation of symbols]

1 ... Swelled super absorbent fiber sheet, 2 ... Unabsorbed super absorbent fiber sheet, 3 ... Groundwater, 4
... Salt water, 5 ... Impermeable layer

Claims (1)

[Claims] 1. A method for preventing salinization of groundwater using a superabsorbent fiber sheet, characterized in that a superabsorbent fiber sheet is embedded in a trench constructed at a boundary portion (saltwater wedge portion) between groundwater and saltwater.