JPH0663901B2 - Leakage detection method for impermeable structures - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for electrically detecting the presence or absence of water leakage and the water leakage position in a waste final disposal site and other water-impervious structures.

<Prior Art> As a geological survey technology, an electric survey is known in which an electric current is passed through the ground to search the geology based on the difference in the electrical properties of rocks and strata.

In electrical exploration, the specific resistance method (Wenner method) is known, which searches the geology based on the measured electric resistance of each layer.

The specific resistance method will be briefly described. As shown in FIG. 3, the electrodes A, B, N, and M are set at four points on the ground, and a current is passed through the electrodes A and B arranged on the outermost side, and the outermost side is set. The voltage between the electrodes N and M arranged in the middle of the electrodes A and B arranged in 1 is measured.

When the installation distances L between the electrodes A, B, N, and M are equal, the specific resistance ρ of the ground is calculated by the following equation.

In the above equation, I is the value of the current that flows between the electrodes AB, and V is the voltage (potential difference) obtained between the electrodes N and M.

In the United States, the above-mentioned electrodes are installed on the water surface of a water tank, one of the electrodes N and M is fixed, the other electrode M is moved, or several electrodes other than the electrode M are set. However, there is a method of detecting a water leak by measuring the potential difference between both electrodes.

FIG. 4 shows the method of arranging the electrodes by this water leakage detection technology.

Reference numeral a denotes a water tank having a rubber water blocking sheet b attached to the front surface of the inner circumference.

Electrodes A and B are arranged at the center of the water surface of the water tank a and outside the water surface, respectively, and a reference electrode N is set at the center of the water surface, and an electrode M for measurement is connected to the end of the electrode N.

Then, a current is caused to flow between the electrodes A and B, the potential difference between the electrodes NM is measured while moving the electrode M, and a distribution chart of the measurement result is created.

If there is no damage to the water-blocking sheet b, a concentric equipotential line distribution centered on the energized portion of the electrode A can be obtained as shown in FIG. Further, if the water-impervious sheet b has a damage such as d, a distribution having a characteristic distortion is obtained as shown in the D portion of FIG. 6, and d on the water-impermeable sheet b corresponding to this distortion portion D is obtained. The position of can be detected as a damaged part. Note that this distortion refers to a change in potential distribution caused by breakage.

<Problems to be Solved by the Present Invention> The water leakage detection technology introduced in the United States has the following several problems.

(B) When the storage of the water-impervious structure is a solid, the uniformity of the solid as a whole is inferior to that of water, so the current flowing for measurement may be disturbed and detection of water leakage may be difficult. .

<Object of the Present Invention> The present invention detects a water leak in a water-impervious structure by installing a potential electrode for measurement in the vicinity of an impermeable tank in the ground and measuring the potential difference.

<Structure of the Present Invention> The water leakage detection method of the present invention will be described below with reference to the drawings.

(A) Object to be Measured The object that can be measured in the present invention is a structure whose material is a high resistance material, and is, for example, a final disposal site of a water-shielded waste, an underground structure of a building, or the like.

(B) Measurement principle In the present invention, a power supply electrode is arranged outside and inside a water shield member provided in a water shield structure to apply a voltage, and a reference potential electrode is provided outside or inside the water shield member. On the other hand, the measuring potential electrodes are arranged in a mesh shape in the vicinity of the water-impervious member.

Then, the presence or absence of water leakage is determined based on the presence or absence of characteristic strain in the potential distribution measured by the measurement potential electrode, and the leakage position is obtained from the characteristic strain position.

The connection position of the supply electrode may be any current flow method as long as a potential difference can be generated between the reference potential electrode and the measurement potential electrode.

<Example> In this example, an experiment assuming a final disposal site for waste will be described (Figs. 1 and 2). (A) Structure of entire model of final disposal site for waste Various disposals for a final disposal site of management type. Impermeable tanks will be formed in the entire landfill site to prevent the infiltration of environmental pollutants generated from materials.

As the low water-permeable material used for the water shield tank, clay, asphalt are used alone or as a laminate thereof in addition to water shield sheets such as concrete and synthetic rubber / plastic.

Recently, as shown in the figure, it is the mainstream to use the water blocking sheet 1.

Specifically, the clay-based low water-permeable soil 3 is laid on the front surface of the base 2, the water-permeable sheet 1 is laid on the upper surface of the low-water-permeable soil 3, and finally the entire surface of the water-permeable sheet 1 is shielded. A cover soil 31 is laid to protect the water sheet 1 from damage.

(B) Impermeable Sheet In this embodiment, a case where the impermeable sheets 1 are laminated in two layers, one on top of the other, will be described.

Fill the space between the two water-impervious sheets 1 with sand etc.
And the drainage pipes 34 and 35 are embedded in the soil cover 31 and the drainage tank 32 above the water-blocking sheet 1, respectively.

(C) Electrode installation position A large number of electrodes 4 are embedded in a mesh shape between the upper and lower two water-blocking sheets 1.

In this embodiment, a case where the electrode 4 is provided on the lower surface of the upper water-blocking sheet 1 will be described.

These electrodes 4 correspond to the above-mentioned potential electrodes for measurement, and low resistance materials such as iron, stainless steel, brass and carbon can be used.

Guide the output cable connected to each electrode 4 to the control room,
Configured so that the potential difference can be measured and the potential distribution can be created in the control room.

On the other hand, the reference potential electrode 5 is connected to the central part of the final disposal site.

In order to generate a potential difference between the electrodes 4 and 5, another supply electrode is placed in the waste 6 dumped at the final disposal site.

(D) Detection method An electric current is applied from the center of the final disposal site, and the potential difference between the potential electrodes 4 and 5 is sequentially measured.

A potential distribution map is created based on the measured locations at each measured point, and the presence or absence of water leakage and the position of water leakage are detected from the created potential distribution map.

When the water shield sheet 1 is not damaged and has no water leakage, a concentric potential distribution centered on the energized position is obtained.

In addition, when a part of the water-blocking sheet 1 is damaged and leaks water, as shown in FIG. It will be central.

<Other Examples> In the above-described examples, the case where the water-blocking sheet 1 is double-laid has been described, but the number may be one.

When the waterproof sheet 1 is used as a single layer, a large number of electrodes 4 are embedded in a mesh shape on the lower surface side or the upper surface side of the waterproof sheet 1.

<Effects of the Present Invention> Since the present invention is as described above, the following effects can be expected.

(B) Because the measurement electrode is installed in the ground to obtain the potential difference, it is not necessary to move the measurement potential electrode, and it can be buried in a short distance of the water-impervious structure and at a certain distance.
The potential difference can be measured accurately.

(B) Since the measurement electrodes are installed as described above, the leak location can be accurately detected even if it has a size that cannot be detected by US technology.

(C) If it is adopted in the final disposal site of waste and the facility that stores various harmful substances, the leak position of the harmful substances can be accurately detected, and the countermeasures can be taken early.

Therefore, environmental pollution can be minimized.

(D) It can be used in many fields such as water leak detection at the roof waterproof part of the building, and its application range is wide.

[Brief description of drawings]

Fig. 1: Cross-sectional view of the final disposal site of waste Fig. 2: Potential distribution diagram when water leakage occurs Fig. 3: Conceptual diagram of electric exploration Fig. 4: Explanatory diagram of conventional leak detection technology Fig. 5: Conventional Potential distribution diagram when there is no water leakage by the conventional water leakage detection technology Fig. 6: Electric potential distribution diagram when water leakage occurs by the conventional water leakage detection technology

Continuation of the front page (56) Reference JP-A-55-107947 (JP, A) US Patent 4435525 (US, A) US Patent 3526831 (US, A)

Claims (1)

[Claims] 1. A water-impervious structure having an electrically high-impervious water-impervious layer, an inner region surrounded by the water-impermeable layer, having a solid storage, and an outer region outside the water-impervious layer. In the method for detecting water leakage of an object, power feeding electrodes for generating an electric field between the inner region and the outer region are arranged in the inner region and the outer region, respectively, and a voltage is applied between the power feeding electrodes to interrupt the shielding. A large number of measuring potential electrodes are embedded in a mesh shape in the vicinity of the water layer, and a reference potential electrode is embedded in the internal region or the external region as an electrode separate from the power feeding electrode, and the reference electrode and each of the reference electrodes are embedded. A water-impervious structure characterized in that the potential difference between the measurement potential electrodes is sequentially measured, the potential distribution near the water-impervious layer is obtained, and the leak position of the water-impermeable layer is obtained from the distortion of the potential distribution. Leakage detection method for objects.