JP2000283877A - Water leakage detecting method in final waste disposal plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a water leakage detecting method, in a final waste disposal plant, in which the existence of a leak of water, in an extreme trace amount, permeating through clay at a time when a liner sheet is damaged and the position of the leakage of water can be detected at an early stage in the disposal plant which adopts a double water cutoff structure by the liner sheet and by the clay. SOLUTION: A water collecting and discharge pipe which is composed of medium-diameter pipes 11 extended from a tunnel 10 for observation to the lower part of a clay layer and many small-diameter pipes 12 branched from the medium-diameter pipes 11 is arranged and installed. A self-propelled device 20 which is provided with a monitoring function and a water collecting function is introduced into the medium-diameter pipes 11. Then, whether water exists or not in connection parts of the medium-diameter pipes 11 to the small-diameter diameter pipes 12 is monitored. The water is collected so as to be analyzed. When a leakage of water is detected, it is estimated that a sheet damage part exists in a water collecting region in the small-diameter pipe from which the leak of water flows out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting water leakage at a final waste disposal site, and more particularly, to a method for detecting a water leakage at a final waste disposal site employing a double water-blocking structure of a water-blocking sheet and clay (water-blocking layer). The present invention relates to a method for early detection of the presence and location of a very small amount of water leaking through a clay when a sheet is damaged.

[0002]

2. Description of the Related Art In the revision of the technical standards for final disposal sites, which came into effect in June 1998, two types of water-impervious sheets, water-impervious sheets and clay (thickness of clay layer) :
Either duplexing with 50 cm or more, permeability coefficient of 10 ^-6 cm / sec or less, or duplexing with a water-blocking sheet + asphalt concrete is required. Among them, the above-mentioned water-blocking structure is particularly effective for disposal sites because of the permanent stability of clay.When clay is used as a water-blocking layer, the amount of water leakage at the time of sheet breakage, It becomes extremely small compared to the case of breakage. However, even a very small amount of water leaking through such a clay layer,
Residents around the disposal site are expected to require reliable detection of the leak.

In the above water-blocking structure, as a method of detecting water leakage through the clay layer, it is conceivable to apply a known electric method or a water leakage collecting method. However, the electric type has a problem in guaranteeing long-term maintenance and management. In addition, since the amount of water that permeates through the clay layer is extremely small in the water collection method as described above, a considerable amount of water is required to leak continuously to the end of the drainage pipe, which is the point where the presence or absence of water leakage is checked and detected. It becomes possible only when it occurs. Therefore, in this case, the detection is performed after the leakage is expanded, and the repair measures are greatly delayed.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to quickly determine the presence and location of a very small amount of water leaking through a clay when a sheet breaks in a disposal site that employs a dual water-shielding structure of a water-impervious sheet and clay. It is an object of the present invention to provide a method of detecting water leakage at a final waste disposal site that can be detected at a time.

[0005]

According to the present invention, there is provided a waste final disposal site employing a double water-blocking structure having a water-blocking sheet and a clay layer laid under the water-blocking sheet. Alternatively, a drainage pipe capable of collecting and draining by gravity flow is disposed in the clay layer, a camera function capable of remotely monitoring the inside of the drainage pipe in the drainage pipe, and water sampling capable of sampling water in the pipe. The present invention provides a method for detecting water leakage at a final waste disposal site by introducing a self-propelled device having a function and detecting the presence or absence of water leakage from water sampled by the device.

That is, according to the present method, a camera and a self-propelled device having a sampling function are inserted into a drainage pipe disposed under or in a clay layer, and the presence or absence of water in the pipe is remotely monitored. Continue, if you find water, sample the water,
The salinity of the water is analyzed to evaluate and determine whether or not the water is leachate (leakage) originating from inside the disposal site. Note that a CCD camera or the like can be preferably used as a camera function, and a water sampling device with a nozzle can be used as a water sampling function. The water sampling device is connected to a vacuum pump and a tube at the downstream end of a collection / drainage pipe. By operating the pump, water can be taken from the nozzle and water can be sent from the water sampler to the end of the pipe, which is the analysis point, through the tube.

When the drainage pipe is disposed below the clay layer, a water collecting and distributing layer is provided below the clay layer. When the drainage pipe is interposed between the clay layers, the drainage pipe is located above the drainage pipe. It is desirable to secure the thickness of the clay layer portion of 50 cm or more.

In this method, the collecting and draining pipe comprises a medium-diameter pipe into which the device can be introduced, and a small-diameter pipe branched from the medium-diameter pipe by a large number. It is possible to monitor the presence or absence of water at the connection with the filter and sample the water present at the connection. That is, the medium-diameter pipe is used as a monitoring / sampling pipe for running the self-propelled device, and a large number of small-diameter pipes are branched from the medium-diameter pipe so that water can be collected as densely as possible throughout the clay layer.
The self-propelled device monitors the flow of water flowing from the small-diameter pipe end hole to the medium-diameter pipe at the connection between the medium-diameter pipe and the small-diameter pipe.If water is found, the water is sampled and analyzed, and leakage is detected. When it is detected, it can be estimated that a sheet breakage exists in a region where the small-diameter pipe that has flowed out the water leak collects water.

[0009] The downstream end of the medium diameter pipe is connected to a large diameter pipe or tunnel for observation, and the self-propelled device is introduced into the medium diameter pipe from the large diameter pipe or tunnel. At the site, the end of the medium-diameter pipe penetrates the disposal site dam, and the self-propelled device can be introduced into the medium-diameter pipe from outside the disposal site.

[0010]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an explanatory cross-sectional view of a seepage control portion of a final waste disposal site. The left half (cross-sectional structure type 1) and the right half (cross-sectional structure type 2) of a central observation tunnel 10 are shown. For convenience, separate cross-sectional aspects are shown. That is, in the left half type 1, the clay layer 2 (thickness 50c)
m, permeability coefficient 10 ^-7 cm / sec), and the clay layer 2
A drainage collection layer 3 is installed below the storage area. The collecting and draining layer 3 is provided in a sand layer 3 'laid under the clay layer 2 in a collecting and draining pipe (11, 12).
Is arranged. Further, an auxiliary sheet 4 is provided below the water collecting and distributing layer 3.
Is laid, but the sheet 4 may be replaced with clay.

On the other hand, in the type 2 in the right half, a clay layer 2 ′ (thickness: 80 cm, water permeability: 10 ⁻⁷ cm) is provided below the impermeable sheet 1.
/ Second) and a collection and distribution pipe (1
1 ′, 12 ′) are interposed. The thickness of the clay layer above the drainage pipe is about 50 cm.

FIG. 2 is an explanatory plan view showing a piping configuration of the collecting and distributing pipe (natural flow type). In this drawing, the left half (piping type 1) and the right half (piping type) of the central observation tunnel 10 are also shown. Type 2) shows a separate piping mode for convenience. Therefore, the drainage pipe of the sectional structure type 1 or 2 in FIG. 1 can be arranged in either the left or right piping type in FIG. 2, but for convenience, the medium diameter pipe in the left half and the right half in FIGS. Have the same reference numbers.

In the piping type 1 (dense type), a perforated medium-diameter pipe 11 (φ20 to 30 cm) for monitoring and sampling branches about 20 m pitch from the observation tunnel 10 in a direction around the disposal site almost perpendicular to the tunnel 10. It is stretched, and a number of perforated small-diameter pipes 12 (φ2 to 3 cm) are branched from both the medium-diameter pipes 11 at a pitch of about 2 m on both left and right sides.

In the piping type 2 (crossing type), the medium diameter pipe 11 '
Is arranged in the same manner as in the type 1 except that the small-diameter pipes 12 ′ are branched right and left from each medium-diameter pipe 11 ′ at a pitch of about 4 m, and the length of each small-diameter pipe 12 ′ is the length of the small-diameter pipe 12 of the type 1. And is arranged so that a small-diameter pipe branched from one medium-diameter pipe intersects a small-diameter pipe branched from another medium-diameter pipe.

FIG. 3 shows a medium-diameter pipe 11 for monitoring and sampling.
An example of a self-propelled device 20 with a camera sampling function to be introduced into 11 'is schematically shown. The device 20 includes a CCD camera 21 and a water sampler 22, and the CCD camera 21 is for monitoring the inside of the tube with a monitor device in a separate room. The water sampler 22 is a container having a water sampling nozzle 23, and is connected to a vacuum pump (not shown) at a water sampling analysis point set in the tunnel 10 via a water sampling pipe 24. The operation of the vacuum pump causes the nozzle 23
And water can be sent to the analysis point through the pipe 24. Reference numeral 25 denotes a cable for controlling running, zooming and swinging a camera, changing the direction of a nozzle, and the like, and a power supply.

In the present invention, the self-propelled device 20 is introduced from the observation tunnel 10 into each of the medium-diameter tubes 11, 11 ', and each connection between the medium-diameter tubes 11, 11' and each of the small-diameter tubes 12, 12 '. In the section, the presence or absence of water flowing down from the small-diameter pipe end hole to the medium-diameter pipe side is monitored. Such monitoring is continued on a regular basis. Then, when the outflow of water is confirmed at any of the connection portions, the water is supplied to the device 2
A predetermined analysis is performed by sampling at 0. As a result of the analysis,
If it is confirmed that the water is leaking, it can be estimated that a sheet damaged portion exists in the water collecting area of the small diameter pipe from which the water has flowed out.

Further, in the piping type 2, one medium-diameter pipe 11 '
When water leakage is detected at one connection portion 13A in A, the other small-diameter tubes 12'B, 12'C, and 12'D that intersect with the small-diameter tube 12'A branching from the connection portion 13 are connected. The presence or absence of water leakage is also confirmed at each of the connection portions 13B, 13C, and 13D in the middle diameter pipe 11'B. And, for example, the connection unit 1
When water leakage is detected only at 3C, it can be estimated that a sheet damaged portion is present in an overlapping portion (see hatching) between the water collecting area of the small diameter pipe 12'A and the water collecting area of the small diameter pipe 12'C. .

[0019]

As described above, according to the method for detecting water leakage in a final waste disposal site according to the present invention, the sheet leaking method is adopted in a disposal site that employs a double water-impervious structure composed of a water-impervious sheet and clay (water-impervious layer). The very small amount of water leaking through the impermeable layer at the time of damage can be detected at an early stage by installing and monitoring the necessary equipment inside the collection / drainage pipe. It is possible to respond promptly to abnormal situations such as an increase.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view schematically showing a water shielding structure in a disposal site, and shows different modes on the left and right for convenience.

FIG. 2 is an explanatory plan view of a collecting / draining pipe, showing different modes on the left and right for convenience.

FIG. 3 is an explanatory view schematically showing an example of a self-propelled device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Waterproof sheet 2 Clay layer 3 Drainage layer 3 'Sand layer 4 Auxiliary sheet 10 Observation tunnel 11, 11' Medium-diameter pipe 12, 12 ', 12'A, 12'B, 12'C, 12'D
Small-diameter pipes 13A, 13B, 13C, 13D Connection part 20 Self-propelled device 21 CCD camera 22 Water sampling device 23 Water sampling nozzle 24 Water sampling pipe 25 Cable

Claims (2)

[Claims] 1. A waste final disposal site employing a dual water-impervious structure having a water-impervious sheet and a clay layer laid under the water-impervious sheet, in a natural flow manner under the clay layer or in the clay layer. A self-propelled device having a camera function capable of remotely monitoring the inside of the pipe and a water sampling function capable of sampling water in the pipe. A method for detecting water leakage at a final waste disposal site, comprising detecting whether water is leaked from water introduced and sampled by the device. 2. The collection / drainage pipe comprises a medium diameter pipe into which the apparatus can be introduced, and a small diameter pipe branched from the medium diameter pipe by a large number. The method for detecting water leakage at a final waste disposal site according to claim 1, wherein the presence or absence of water at the connection part is monitored and the water present at the connection part is sampled.