JP3965505B2 - Underground air survey method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an underground air survey method and apparatus for surveying geological contamination of a relatively surface layer of the ground.
[0002]
[Prior art]
Methods for investigating geological contamination of the relatively surface layer of the ground include underground air sampling methods that collect underground air by inserting underground air sampling tubes and gas detection tubes into the excavated holes, and gas surveys that directly suck the atmosphere. Although there is a method, there is no in-situ underground air survey method having the characteristics as in the present invention in which the ground air is sucked by grounding the container composed of the multi-layered chamber and making the inside of the container have a negative pressure.
[0003]
[Problems to be solved by the invention]
Such conventional techniques have the following drawbacks.
(1) Ground air suction using a drilling hole requires in-situ boring, requires a long time from the start of construction to completion of the survey, and is very uneconomical, including boring costs. This is a destructive test with a high environmental impact.
Even when making a sampling hole with a simple driving device, there are differences in scale, but there are similar disadvantages.
(2) Ground air suction using a drilling hole requires extubation of the drill rod after excavation to a predetermined depth. At that time, the underground air is disturbed by the inflow of air into the hole, The investigation cannot be performed.
[0004]
(3) The ground air suction method using the excavation hole is to collect ground air containing volatile gas from an area with a hole diameter of about φ100 mm in plan view. When making, the area is very small with a hole diameter of about φ10 mm. For this reason, it becomes a “spot” evaluation area, and it is necessary to conduct excavation surveys at many locations when identifying a geological contamination source in a vast factory site.
(4) The gas survey method that directly sucks in the atmosphere has a flow due to wind or the like, and the source of contamination cannot be specified.
[0005]
The object of the present invention is to solve the above-mentioned conventional problems by omitting a high-cost and in-situ destruction process such as boring, and at a low cost, easily and reliably in a short time. An object of the present invention is to provide an underground air survey method and apparatus capable of surveying.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention is to investigate by installing a collection container having an opening on the ground surface in a prone state and collecting the underground air in the collection container at a pressure lower than atmospheric pressure. The sampling container has at least a double structure consisting of an outer container and an inner container, and the ground air disturbed by the inflowing outside air and the inflowing outside air is exposed from the space formed by the outer surface of the inner container and the inner surface of the outer container. It is characterized by collecting and investigating underground air that is not disturbed by inflowing outside air into the inner container.
[0007]
In addition, an apparatus for surveying by collecting a ground container in the collection container by setting a collection container having an opening on the ground surface in a prone state and setting the interior of the collection container to a pressure lower than atmospheric pressure, the collection container comprising: The outer container that maintains the pressure difference with the outside air and that can discharge the ground air disturbed by the inflowing outside air and the outside air and the inner container that collects the ground air that is not mixed with the inflowing outside air. It is characterized by at least a double structure.
[0008]
In addition, a communication hole that communicates with the inside of the outer container is formed in the inner container, and the outer container is connected to a decompression unit to maintain a pressure difference from the outside air.
[0009]
Further, the outer container is provided with sealing means for blocking at least the inside of the outer container and the outside air.
[0010]
The sealing means may be an elastic material attached to the entire outer peripheral edge of the opening of the outer container.
[0011]
Further, the sealing means is a cylindrical sealing cylinder pressed into the ground from the opening of the outer container.
[0012]
In addition, an underground air sampling hole into which a gas sampling tube for sucking and sampling the underground air in the inner container can be inserted is formed in the inner container and the outer container.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.
As shown in FIG. 1, the underground air survey device according to the embodiment of the present invention is configured such that a sampling container 1 having an opening 1 a is placed on the ground surface G in a prone state, and the inside of the sampling container 1 is under atmospheric pressure. An apparatus for collecting and investigating underground air 10 in a collection container 1 at a low pressure, wherein the collection container 1 maintains a pressure difference from the outside air and is disturbed by the inflowing outside air 11 and the inflowing outside air 11. It has at least a double structure including an outer container 2 that can discharge (mixed air 12) to the outside and an inner container 3 that collects underground air 10 that is not mixed with the inflowing outside air 11.
[0014]
The outer container 2 is provided with sealing means 2b for blocking the inside of the outer container 2 from the outside air.
Furthermore, it is desirable that the inner container 3 is provided with a sealing means 3b that shuts off the inside of the inner container 3 and the inside of the outer container 2.
The sealing means 2b and 3b are rubber or polymer materials which are attached to the entire outer peripheral edges of the openings 2a and 3a of the outer container 2 and the inner container 3 and closely adhere to the unevenness of the ground surface G and have a sealing function. Elastic material.
[0015]
Further, although not shown, the sealing means 2b and 3b according to another embodiment of the present invention are pushed into the ground from the openings 2a and 3a of the outer container 2 and the inner container 3 to an appropriate depth, and have a sealing function. It may be a cylindrical seal cylinder having
[0016]
The outer container 2 and the inner container 3 are a kind of low-vacuum container in which the inside is maintained at a pressure lower than the atmospheric pressure. Therefore, the outer container 2 and the inner container 3 are best formed in a thin and light, substantially spherical tank structure with excellent buckling strength.
As shown in FIG. 2, the outer container 2 and the inner container 3 have a gas sampling pipe 6 that sucks and collects the underground air 10 in the inner container 3 (inner container interior 3 d), so that the underground air can be inserted in an airtight manner. Sampling holes 2d and 3c are formed.
[0017]
As shown in FIG. 1, the outer container 2 is connected to a decompression means 5 such as a vacuum pump through an exhaust pipe 5a connected to an exhaust hole 2c provided at the top, and the collection container is connected by the decompression means 5. 1 is discharged and the pressure difference (negative pressure) from the outside air is maintained.
When the air inside the collection container 1 is discharged by the decompression means 5, the gas collection pipe 6 is removed, and the underground air collection hole 2d of the outer container 2 is sealed by a plug member 7 such as a plug. The underground air sampling hole 3 c of the inner container 3 is a communication hole that communicates with the inside of the outer container 2.
[0018]
Next, an underground air investigation method for collecting underground air at a predetermined original position using the above-described underground air investigation device of the present invention will be described with reference to FIGS. 1 to 3.
[0019]
As shown in FIG. 1, the decompression means 5 receives the pressure signal from the pressure gauge 8 provided in the exhaust pipe 5a and is controlled by the controller 9, and as shown schematically in FIG. The pressure 20 and the pressure holding time can be arbitrarily set.
[0020]
As schematically shown in FIG. 1, the pressure in the collection container 1 has a negative pressure distribution 20 having a slope that gradually decreases from the atmospheric pressure due to the influence of the inflowing external air 11 from the vicinity of the sealing means 2 b of the outer container 2. Show.
[0021]
Therefore, the inflowing outside air 11 from the vicinity of the sealing means 2b of the outer container 2 becomes the mixed air 12 with the underground air 10, and the space portion 4 between the outer surface of the inner container 3 and the inner surface of the outer container 2 is used as a flow path. The pressure reducing means 5 discharges the air from the exhaust hole 2c of the outer container 2 to the outside.
On the other hand, the inner container interior 3d is set to be sufficiently smaller than the outer container 2 so that the underground air 10 is stored without being mixed with the inflowing outside air 11 in the inner container interior 3d.
The size of the inner container 3d can be easily realized, for example, with a diameter of 300 mm or more, though it depends on the size of the decompression means 5 in consideration of the size of the geological contamination investigation target ground at the original position, transportation and handling, etc.
[0022]
Thereafter, as shown in FIG. 2, the gas sampling pipe 6 is inserted into the underground air sampling holes 2 d and 3 c of the outer container 2 and the inner container 3, and the underground air 10 inside the inner container 3 d is not mixed with the inflowing outside air 11. Collect by aspiration in the state.
[0023]
Although not shown, the gas sampling tube 6 is preferably a gas detection tube having a gas suction hole for sucking air (gas) from the tip.
The gas detector tube is well known and will not be described in detail. However, the gas detector tube is connected to the detector tube via a stainless steel conduit and the like, and is equipped with a vacuum metering pump that sucks air (gas). It consists of an extended collection tube consisting of a flexible tube connected to the set.
[0024]
【The invention's effect】
As described above, according to the present invention described in detail, the following excellent effects are obtained.
(1) Compared to conventional underground air suction using a drilling hole, a boring process accompanied by destruction at the original position can be omitted at high cost. For this reason, it is possible to conduct a geological contamination survey easily and in a short time at a low cost.
(2) There is no inflow of air in the inner container, and undisturbed underground air can be collected, so a reliable geological contamination survey can be performed.
(3) The diameter of the inner container 3d can be easily realized to be 300 mm or more, and the area is 900 to 9 times larger than the existing excavation hole having a diameter of 10 to 100 mm. When specifying as “surface evaluation”, the number of survey points can be greatly reduced compared to conventional survey methods, which is very efficient.
[0025]
(4) Compared with the gas survey method that directly sucks in the air, it is not affected by the flow of wind and so on, so it is possible to conduct a reliable geological survey.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing the concept of an underground air survey method and apparatus according to an embodiment of the present invention.
FIG. 2 is a partial longitudinal sectional view showing the concept of an underground air survey method and apparatus according to an embodiment of the present invention.
FIG. 3 is an operation diagram schematically showing a pressure change and a process in the collection container in the underground air survey method according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sampling container 1a, 2a, 3a Opening part 2 Outer container 2b, 3b Sealing means 2c Exhaust hole 2d Underground air sampling hole 3 Inner container 3a Aeration flow path 3c Underground air sampling hole (communication hole)
3d Inner vessel interior 4 Outer vessel space 5 Depressurizing means 5a Exhaust pipe 6 Gas sampling pipe 6a Opening 7 Plug member 8 Pressure gauge 9 Controller 10 Ground air 11 Inflowing outside air 12 Mixed air 20 Ground negative pressure distribution line G Ground surface

Claims (7)

A method of investigating by installing a collection container having an opening on the ground surface in a prone state, collecting the underground air in the collection container at a pressure lower than atmospheric pressure in the collection container,
The sampling container has at least a double structure composed of an outer container and an inner container, and the ground air disturbed by the inflowing outside air and the inflowing outside air is discharged to the outside from the space formed by the outer surface of the inner container and the inner surface of the outer container. An underground air survey method characterized by collecting and investigating underground air that is not disturbed by the inside of the inner container. A device for installing a sampling container having an opening on the ground surface in a prone state, collecting the underground air in a sampling container at a pressure lower than the atmospheric pressure, and investigating it,
The outer container, wherein the collection container maintains a pressure difference with the outside air and is capable of releasing the ground air disturbed by the inflowing outside air and the inflowing outside air to the outside;
An underground air survey apparatus having an at least double structure including an inner container for collecting underground air in a state where it is not mixed with inflowing outside air. A communication hole communicating with the inside of the outer container is formed in the inner container,
The underground air survey device according to claim 2, wherein the outer container is connected to a decompression means to maintain a pressure difference from outside air. The underground air survey device according to claim 2, wherein at least the outer container is provided with a sealing means for blocking the inside of the outer container from outside air. The underground air survey device according to claim 4, wherein the sealing means is an elastic material attached to the entire outer peripheral edge of the opening of the outer container. 5. The underground air survey apparatus according to claim 4, wherein the sealing means is a cylindrical sealing cylinder that is pushed into the ground from the opening of the outer container. The underground air survey according to claim 2, wherein a ground air sampling hole through which a gas sampling tube for sucking and collecting the underground air in the inner container can be inserted is formed in the inner container and the outer container. apparatus.

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