JP3579894B2 - Insulation sheet inspection method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for inspecting a seepage control sheet at a managed landfill site constructed by laying a seepage control sheet such as a synthetic resin sheet or a synthetic rubber sheet.
[0002]
[Prior art]
Conventionally, in an artificially managed final disposal site using a water-blocking sheet, a construction method that builds the water-blocking inside the disposal site by performing fusion splicing of a band-shaped high-density polyethylene sheet as the water-blocking sheet is used. Has been. In other words, strip-shaped high-density polyethylene sheets are laid, and their adjacent edges are fusion-spliced to cover the entire disposal site.
[0003]
Here, in the case where construction failure occurs in the fusion of the impermeable sheet, the contaminated liquid in the disposal site leaks, causing groundwater contamination and pollution problems. For this reason, the following methods have been proposed as inspection methods at the stage of fusing the water impermeable sheet. Utilizing the fact that the impermeable sheet is an electrically insulating material, a central electrode and a ring-shaped electrode are arranged so as to orbit around the central electrode on the upper side, and a voltage is applied between them to apply a voltage between them. By measuring the presence or absence and the magnitude of the current flowing through the third electrode disposed on the lower side, a defect in the fusing cylinder is detected.
[0004]
Hereinafter, the inspection method described above will be described with reference to FIGS.
[0005]
FIG. 3 shows a cross section at the time of completion of an example of a managed landfill. The configuration of the bottom of the disposal site is, from the top, a protective layer 31, a nonwoven fabric 32, an upper waterproof sheet 33, an intermediate layer 34, a nonwoven fabric 35, a lower waterproof sheet 36, a nonwoven fabric 37, and an original ground 38. Sand is usually used for the protective layer 31 and the intermediate layer 34.
[0006]
In the inspection method proposed above, regarding the upper impermeable sheet 33, the inspection and measurement of the upper impermeable sheet 33 are performed in a state in which water is injected into the nonwoven fabric 32 before the uppermost protective layer 31 is applied. Is assumed.
[0007]
FIG. 4 is a diagram showing a configuration for realizing the inspection method proposed above. FIG. 4 is a plan view showing the electrode structure and the state of electrical connection. The disk-shaped electrode 41 is arranged on the upper water-impervious sheet 33 (FIG. 3), and the ring-shaped electrode 42 is arranged so as to go around the electrode. A voltage from an AC power supply 43 is applied between the disc-shaped electrode 41 and the ring-shaped electrode 42. Further, by connecting the lower electrode (not shown) provided on the intermediate layer 34 (FIG. 3) to the reference potential of the AC power supply 43 via the ammeter 44, the current flowing through the broken portion of the upper water-impervious sheet 33 is reduced. Measure.
[0008]
Of course, when inspecting the lower water-impervious sheet 36, the inspection is performed before the middle layer 34 to the upper layer are constructed.
[0009]
[Problems to be solved by the invention]
However, in the inspection method proposed above, it is important to arrange an electrode for current detection below the impermeable sheet. For this reason, in order to inspect the place where the high-density polyethylene sheet has already been fused, it is necessary to install the lower electrode on the unprocessed part and connect it to the measurement circuit via electric wires. Condition. For this reason, there has been a drawback that when all of the fusion work has been completed, it is necessary to cut a part of the water-impervious sheet and arrange the electrodes.
[0010]
Therefore, an object of the present invention is to provide a water-impervious sheet inspection method that does not require an electrode to be installed below the water-impervious sheet.
[0011]
[Means for Solving the Problems]
According to the present invention, it includes first and second electrodes provided on the surface side of a water-blocking sheet made of an electrically insulating material, wherein the first electrode is used as a fixed electrode and the second electrode is used as a moving electrode. Then, by connecting an AC power supply between the first and second electrodes via an ammeter, when the second electrode moves and comes to a defective portion of the impermeable sheet, the first electrode and the Inspection of the impermeable sheet is performed from the surface side of the impermeable sheet by utilizing the fact that electrostatic coupling occurs between the lower side of the impermeable sheet and a current path is formed and current flows. A sheet inspection system is provided.
[0012]
[Action]
In this water-impervious sheet inspection system, the first electrode forms a current path that flows through the capacitive component of the water-impervious sheet, and the second electrode forms a current path that flows through the poorly fused portion of the water-impervious sheet. For this reason, unlike the proposed method, it is not necessary to dispose the current detection electrode below the impermeable sheet.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
1 and 2, an embodiment of a seepage control sheet inspection system according to the present invention will be described. FIG. 1 is a diagram showing a configuration for realizing a water-blocking sheet inspection system according to the present invention. Here, a case will be described in which the upper impermeable sheet 33 is inspected in the management type final disposal site as described in FIG. This inspection is performed in a state where water is injected onto the upper water-impervious sheet 33 before the nonwoven fabric 32 is applied.
[0014]
In this inspection method, the first electrode 11 is disposed as a fixed electrode on the upper water-impervious sheet 33 made of synthetic resin or synthetic rubber as an electrically insulating material, and the second electrode 12 moves on the upper water-impervious sheet 33. Moving electrode to be used. An AC power supply 13 and an ammeter 14 are connected between the first electrode 11 and the second electrode 12. Note that the first electrode 11 and the second electrode 12 are preferably plate-shaped having a certain area, but their shapes are not limited.
[0015]
The AC power supply 13 outputs an AC signal having a frequency of 10 kHz or more. In such a connection state, when the second electrode 12 is moved on the upper water-impervious sheet 33, when the second electrode 12 comes to a defective or broken portion of the upper water-impervious sheet 33, the intermediate layer 34 is moved. A passed current path is formed, and the current value increases. As a result, a defective construction site of the upper waterproof sheet 33 is found.
[0016]
FIG. 2 is a diagram showing the configuration of FIG. 1 by an equivalent circuit. 2, the capacitance of the upper water-impervious sheet 33 is C, the resistance of the sand layer constituting the intermediate layer 34 is R1, the resistance of the damaged part of the upper water-impervious sheet 33 is R2, and the output voltage of the AC power supply 13 is V0. Then, the current I flowing from the AC power supply 13 is expressed by the following equation.
[0017]
I = V0 / {(R1 + R2) ² + (1 / ωC) ² } ^1/2
Here, trial calculation results are shown for the flowing current value. Substituting R1 + R2 = 10 (kΩ), C = 10 ⁻⁸ (F), f = 10000 (Hz), and V0 = 10 (V) into the above equation as calculation conditions, the flowing current is about 1 (mA). . If the upper impermeable sheet 33 is not damaged or defective, the resistance R2 becomes infinite and the current value becomes zero.
[0018]
Of course, when this inspection method is performed on the lower water-impervious sheet 36 made of the same material as the upper water-impervious sheet 33, it is performed before applying a layer above the nonwoven fabric 35. In addition, since the nonwoven fabric easily conducts electricity by water injection, the present inspection method may be performed after the nonwoven fabric is constructed.
[0019]
As mentioned above, although the embodiment of the present invention was described about the case of the management type final disposal site including the upper impermeable sheet and the lower impermeable sheet, the present invention is applied to the managed type final disposal site as described in FIG. The present invention is not limited to this, and can be applied to any disposal site of a type in which a waterproof sheet such as a synthetic resin sheet or a synthetic rubber sheet is laid.
[0020]
【The invention's effect】
As is clear from the above description, according to the present invention, as a method of inspecting the impermeable sheet immediately before constructing the protective layer and the intermediate layer of the disposal site, the impermeable sheet is formed by the electrostatic coupling effect using the capacity component of the impermeable sheet. Poor fusion or minute breakage can be detected from one side of the water sheet, and there is no need to install electrodes on the back side of the water-impermeable sheet, so the economic effect obtained is significant.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an embodiment of a seepage control sheet inspection system according to the present invention.
FIG. 2 is a diagram showing an equivalent circuit of the configuration of FIG.
FIG. 3 is a cross-sectional view of an example of a managed landfill at the time of completion, to which the present invention is applied.
FIG. 4 is a diagram showing a configuration of a proposed example of a water-blocking sheet inspection method.
[Explanation of symbols]
11 First electrode 12 Second electrode 13, 43 AC power supply 14, 44 Ammeter 31 Protective layer 32, 35, 37 Non-woven fabric 33 Upper waterproof sheet 34 Middle layer 36 Lower waterproof sheet 38 Original ground

Claims (1)

First and second electrodes installed on the front side of the water-insulating sheet made of an electrically insulating material, wherein the first electrode is used as a fixed electrode and the second electrode is used as a moving electrode, and the first and second electrodes are used. By connecting an AC power supply via an ammeter between the second electrodes, when the second electrode moves and comes to a defective portion of the impermeable sheet, the first electrode and the impermeable sheet below the impermeable sheet. A water-blocking sheet inspection method, wherein the water-blocking sheet is inspected from the front side of the water-blocking sheet by utilizing the fact that a current path is formed by the occurrence of electrostatic coupling therebetween and the current flows.

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