JPH10221225A - Soil gas sampling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soil gas sampling device which allows establishment of the sampling efficiency compatible with sampling accuracy. SOLUTION: A sampling pipe 12 is connected to the first pipe end of a manifold 1, and the second pipe end is blocked by a rubber plate 2, and with a third pipe end a hand pump 3 is connected through a gas suction pipe, and a pressure gauge 4 is mounted on a fourth pipe end. By the hand pump 3, purging is conducted around two times so that the air is exhausted from the sampling pipe 12 and the sampling space (gap between a bit 22 and holder 23), and when the pressure gauge 4 permits confirming that the inside of the manifold 1 is restituted to the atmospheric pressure, the condition is generated where the soil gas G oozing at the surrounding earth wall is sucked out and stagnates in the manifold 1. This soil gas G is sucked by a syringe S. This enables sampling immediately when a sufficient quantity of soil gas G has stagnated in the manifold 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soil gas collecting apparatus, and more particularly to a soil gas collecting apparatus capable of achieving both high efficiency and high accuracy.

[0002]

2. Description of the Related Art A soil gas sampling device is a device for sampling gas present in the soil, and is used, for example, for investigating soil contamination by an organic solvent. FIG. 5 is a configuration diagram illustrating an example of a conventional soil gas sampling device. The soil gas sampling device 500 includes a bit 22 and a holder 23 driven into the soil by a driving pipe 21, a sampling plug 64 screwed into the holder 23, and a holder that passes through the driving pipe 21 from the inlet of the driving pipe 21. A tube 71 serving as a supporting medium for lowering the sampling plug 64 to 23 and attaching the sampling plug 64 to the holder 23 and also serving as a ventilation pipe for sucking the soil gas G, and an air pump 81 for sucking the soil gas G through the tube 71. And a soil gas collecting unit 50 for sucking the soil gas G into the syringe S by penetrating the needle of the syringe S into the rubber plate 51 on the upper surface while collecting the sucked soil gas G. The depth D from the ground surface E to the position where the bit 22 is driven is, for example, about 1 m to 15 m.

Next, a description will be given of a procedure for forming a sampling space (K in FIG. 7) in the soil. First, as shown in FIG. 6, a holder 23 is fixed to the tip of the driving pipe 21 and a bit 22 is detachably attached to the tip of the holder 23 so that the bit 22 has a predetermined depth (D in FIG. 5). Drive into the ground until it reaches. Also, the tube 71
The sampling plug 64 is attached to the tip of the pipe, and the sampling plug 64 is lowered from the entrance of the driving pipe 21 through the driving pipe 21 to the holder 23. The outer diameter φ1 of the tube 71 is, for example, 6 mm, and the inner diameter φ2 is, for example, 4 mm. The material of the tube 71 is, for example, a fluororesin. Next, the sampling plug 64 is turned by turning the tube 71, and the sampling plug 64 is screwed into the holder 23. Thereafter, as shown in FIG. 7, the driving pipe 21 is slightly pulled up to
The holder 23 is slightly lifted from 2 to form a sampling space K.

FIG. 8 is a flow chart showing a procedure for collecting soil gas. In step U1, the air pump 81
, The air in the tube 71 and the air in the sampling space K are exhausted. As a result, FIG.
Soil gas G seeps out of the surrounding soil wall into the sampling space K.

In step U2, when a predetermined evacuation time T1 has elapsed, the process proceeds to step U2, but if not, the process returns to step U1 to continue the evacuation. The evacuation time T1 is determined as a time required for the air in the tube 71 to be replaced with the soil gas G in consideration of the suction force of the air pump 81. In step U3, the exhaust of air by the air pump 81 is stopped.

In step U4, the process waits until a predetermined waiting time T2 has elapsed. The reason why it is necessary to wait is that immediately after stopping the exhaust of air,
Since the soil gas G has not yet accumulated sufficiently and the gas pressure is lower than the atmospheric pressure, not only is it difficult to suck into the syringe S, but also when air is mixed in from the needle tip when the syringe S is removed. This is because the sampling accuracy tends to deteriorate. The waiting time T2 is determined in consideration of the geology (the degree of leaching of soil gas varies depending on the geology) and the like.

In step U5, a needle of a syringe is inserted through the rubber plate 51 of the soil gas sampling unit 50 to suck the soil gas G into the syringe S. Thereafter, the syringe S is pulled out.

[0008] Another conventional technology relating to a soil gas device is described in, for example, Japanese Patent Application Laid-Open No. 59-122926.

[0009]

In the above-mentioned conventional soil gas sampling apparatus 500, if the exhaust time T1 and the waiting time T2 are lengthened, the soil gas G is not mixed with impurities such as air.
However, it takes a long time to collect the soil gas G into the syringe S, and there is a problem that the collection efficiency is reduced.
On the other hand, if the evacuation time T1 and the waiting time T2 are shortened, the time until the soil gas G is collected can be shortened. However, impurities such as air easily enter the soil gas G in the syringe S, and the soil gas G is collected. There is a problem that accuracy is reduced. Therefore, it is necessary to prevent the time required for collecting the soil gas G from being too short or too long. However, it is difficult to set the time, and there is a problem that it is difficult to achieve both the collection efficiency and the collection accuracy. Accordingly, an object of the present invention is to provide a soil gas sampling device that can achieve both sampling efficiency and sampling accuracy.

[0010]

SUMMARY OF THE INVENTION In a first aspect, the present invention is directed to a method in which soil gas leached from a soil wall around a sampling space formed in soil is sucked to collect the soil gas. In the soil gas sampling device, a ventilation pipe for sucking the soil gas is connected to one opening of a branch pipe having a plurality of openings, and an air pump is connected to one of the other openings of the branch pipe. One of the other openings in the tube
The present invention provides a soil gas sampling apparatus characterized in that a pressure gauge is attached to one of them. In the soil gas sampling device according to the first aspect, when air in the ventilation pipe and the sampling space is exhausted by the air pump, the air in the ventilation pipe is replaced with the soil gas, and the soil gas is sucked into the branch pipe through the ventilation pipe. Since the pressure in the branch pipe can always be grasped by the pressure gauge, it is possible to accurately grasp the degree of soil gas accumulated in the branch pipe, and to collect immediately when sufficient soil gas has accumulated in the branch pipe. Can be done. Thus, it is possible to prevent the time required for collecting the soil gas from being excessively long and thereby reduce the collection efficiency, and to prevent the time required for collecting the soil gas from being insufficient and the collection accuracy from being lowered. That is, there is no excess or deficiency in the time until the soil gas is collected, and both the collection efficiency and the collection accuracy can be increased. In addition, since it is possible to suck the soil gas into the syringe or the like after confirming that the pressure in the branch pipe and the outside world are equal to each other (atmospheric pressure), impurities such as air are mixed due to a pressure difference between the inside of the branch pipe and the outside world. Can be prevented. Also in this respect, the sampling accuracy can be improved. Further, since the suction of the soil gas is minimized, a pump having a high suction force is not required, and the cost can be reduced.

According to a second aspect, the present invention relates to a soil gas sampling apparatus for sucking soil gas leached from a soil wall around a sampling space formed in the soil and sampling the soil gas. A vent pipe for sucking the soil gas is connected to one opening of a branch pipe having a plurality of openings, a hand pump is connected to one of the other openings of the branch pipe, and still another of the branch pipe is connected. A soil gas sampling device is provided, wherein a pressure gauge is attached to one of the openings. In the soil gas sampling device according to the second aspect, the hand pump is used as the air pump, so that the cost can be further reduced. In particular, when a sampling pipe having an outer diameter smaller than the inner diameter of the tube and being passed through the tube is used as the ventilation pipe, the inner volume of the ventilation pipe is reduced when the tube is used as the ventilation pipe. The air in the sampling pipe is replaced with soil gas, so the amount of exhaust gas is small, the exhaust time is short, and high suction power is not required. It can be easily performed, and is highly useful.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited by this.

FIG. 1 is a configuration diagram of a soil gas sampling apparatus according to one embodiment of the present invention. This soil gas sampling device 1
00 is a bit 22 and a holder 23 driven into the soil by a driving pipe 21, a sampling plug 24 screwed into the holder 23, and a sampling plug 24 from the entrance of the driving pipe 21 through the driving pipe 21 to the holder 23. Tube 11 serving as a support medium for attaching sampling plug 24 to holder 23, sampling pipe 12 serving as a ventilation pipe for sucking soil gas G, and hand pump 3 for sucking soil gas G through sampling pipe 12. And a manifold 1 for accumulating the sucked soil gas G and penetrating the needle of the syringe S into the upper rubber plate 2 to suck the soil gas G into the syringe S. . The manifold 1 is a branched thin tube, and is housed in a case 10. The manifold 1
The first pipe end is connected to the sampling pipe 12, the second pipe end is closed with a rubber plate 2, and the third pipe end is connected to the hand pump via a gas suction pipe. 3 is connected, and a pressure gauge 4 is attached to the fourth pipe end. The depth D from the ground surface E to the position where the bit 22 is driven is, for example, about 1 m to 15 m.

Next, a description will be given of an operation procedure until a sampling space (K in FIG. 3) is formed in the soil. First, as shown in FIG. 2, a holder 23 is fixed to the tip of the driving pipe 21 and a bit 22 is detachably attached to the tip of the holder 23 so that the bit 22 has a predetermined depth (D in FIG. 1). Drive into the ground until it reaches. Further, the sampling plug 24 is attached to the tip of the sampling pipe 12 and to the tip of the tube 11, and the sampling plug 24 is lowered from the entrance of the driving pipe 21 through the driving pipe 21 to the holder 23. The outer diameter φ1 of the tube 11 is, for example, 6 mm, and the inner diameter φ2 is, for example, 4 mm. The outer diameter φc of the sampling pipe 12 is, for example, 3.5 mm.
And the inner diameter φd is, for example, 1.5 mm. The material of the tube 11 is, for example, polyethylene. Further, the material of the sampling pipe 12 is, for example, a fluororesin. Next, turn the tube 11 and turn the sampling plug 2
Turn 4 to screw the sampling plug 24 into the holder 23. Thereafter, as shown in FIG.
1 is slightly lifted, and the holder 23 is slightly lifted from the bit 22 to form a sampling space K.

FIG. 4 is a flowchart showing an operation procedure for collecting soil gas. In step S1, the hand pump 3
The air in the sampling pipe 12 and the air in the sampling space K are exhausted by purging the air about twice. As a result, the soil gas G seeps out of the surrounding soil wall into the sampling space K in FIG. 3, and the soil gas G is sucked into the manifold 1 through the sampling pipe 12. The internal volume of the collection pipe 12 (for example, the tube 11 and the collection pipe 1
2 airtightly shut off, the outer diameter of the sampling pipe 12 = 3.5 mm,
When inner diameter = 1.5mm, length = 10m, internal volume = about 18
cc) is the internal volume when the tube is used as a vent tube (for example, the outer diameter φ1 of the tube 71 in FIG.
2 = 4mm, length = 10m, internal volume = about 126cc)
The air in the collection pipe 12 can be sufficiently replaced with the soil gas G by two purges.

In step S2, the pressure gauge 4 is observed, and the process waits until the inside of the manifold 1 returns to the atmospheric pressure, and then proceeds to step S3. When the pressure returns to the atmospheric pressure, the soil gas G is sufficiently accumulated in the manifold 1. In step S3,
The needle of the syringe S penetrates the rubber plate 2 of the manifold 1 to suck the soil gas G into the syringe S. Thereafter, the syringe S is pulled out.

According to the above soil gas sampling apparatus 100,
Since collection can be performed immediately when sufficient soil gas G has accumulated in the manifold 1, there is no excess or deficiency in the time until the soil gas G is collected. After confirming that the inside of the manifold 1 has reached the atmospheric pressure, the syringe S
Since the soil gas G can be sucked into the inside, it is possible to prevent impurities such as air from being mixed due to a pressure difference between the inside of the manifold 1 and the outside. Furthermore, since the soil gas G is sucked up using the small hand pump 3, the cost can be reduced as compared with the case where a pump having a high suction force is used. Further, the needle of the syringe S is connected to the manifold 1 by the tip of the needle.
Can be inserted deeply until it reaches the branch point of the branch pipe (the branch pipe whose end is closed by the rubber plate 2), so that the syringe S can be sucked in a stable state, and the workability is improved.

[0018]

According to the soil gas sampling apparatus of the present invention, whether or not soil gas has sufficiently accumulated in the branch pipe can be determined based on the air pressure in the branch pipe. Can be prevented, and both the collection efficiency and the collection accuracy can be improved. In addition, since the sampling using a gas sampling device such as a syringe can be performed in a state where the atmospheric pressure in the branch pipe and the outside pressure are equal (atmospheric pressure),
It is possible to prevent impurities such as air from entering the gas sampling instrument. Further, since the exhaust state of the ventilation pipe and the sampling space can be grasped by the air pressure in the branch pipe, it is not necessary to continue the exhaust for an unnecessarily long time. Therefore, a simple air pump such as a hand pump can be adopted, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a soil gas sampling device according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a bit and a holder, a tube, and a sampling pipe that are driven into soil.

FIG. 3 is an explanatory diagram showing a state in which a sampling space is formed.

FIG. 4 is a flowchart showing an operation procedure for collecting soil gas by the soil gas collecting device of FIG. 1;

FIG. 5 is a configuration diagram showing an example of a conventional soil gas sampling device.

FIG. 6 is an explanatory view showing a bit and a holder driven into the soil and a tube.

FIG. 7 is another explanatory diagram showing a state in which a sampling space is formed.

8 is a flowchart showing an operation procedure for collecting soil gas by the soil gas collecting device of FIG.

[Explanation of symbols]

 Reference Signs List 100 Soil gas sampling device 1 Manifold 2 Rubber plate 3 Hand pump 4 Pressure gauge 10 Case 11 Tube 12 Sampling pipe 21 Driving pipe 22 Bit 23 Holder 24 Sampling plug G Soil gas K Sampling space S Syringe

Claims (2)

[Claims] 1. A soil gas sampling device for sucking soil gas leached from a soil wall around a sampling space formed in the soil and sampling the soil gas, the branch pipe having a plurality of openings. A ventilation pipe for sucking the soil gas is connected to one of the openings, an air pump is connected to one of the other openings of the branch pipe, and a pressure gauge is attached to one of the other openings of the branch pipe. A soil gas sampling device, characterized in that: 2. A soil gas collecting apparatus for sucking soil gas leached from a soil wall around a sampling space formed in the soil to collect the soil gas, wherein the branch pipe having a plurality of openings. A vent pipe for sucking out the soil gas is connected to one of the openings, a hand pump is connected to one of the other openings of the branch pipe, and a pressure gauge is connected to one of the other openings of the branch pipe. A soil gas sampling device characterized by being attached.