A method for detecting the concentration of volatile organic compounds in cracks of barrier barriers in contaminated sites

Abstract

The present invention provides a method for detecting the concentration of volatile organic compounds in cracks of a barrier barrier of a contaminated site, comprising the following steps: step 10, opening a sampling hole at the crack of a horizontal barrier barrier, wherein the sampling hole penetrates the horizontal barrier barrier; step 20, placing a gas tank filled with inert gas in the sampling hole; step 30, opening the opening at the bottom of the gas tank, so that the volatile organic compounds in the contaminated foundation diffuse into the gas tank; real-time detection of the concentration of the inert gas at different heights in the gas tank, when the concentration of the inert gas at different heights is the same, closing the opening at the bottom of the gas tank; step 40, taking the gas tank out of the sampling hole, and measuring the concentration of the volatile organic compounds in the gas tank. The method for detecting the concentration of volatile organic compounds in cracks of a barrier barrier of a contaminated site provided by the present invention can detect the concentration of volatile organic compounds in the gap of a broken barrier barrier in situ, thereby improving the detection accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of structure performance detection in contaminated sites, and in particular, relates to a method for detecting the concentration of volatile organic matter in cracks of a barrier of a contaminated site. Background Art

[0002] Horizontal structures such as production workshops, tank areas, road surfaces or ground in production enterprises often have the dual functions of bearing external loads and blocking the migration of pollutants, which are called horizontal barriers. These structures are mostly made of concrete materials, which are prone to cracking under the external loads and corrosion of production waste liquids, resulting in a large number of cracks, which become the dominant channels for the migration of pollutants. In sites with volatile organic compound pollution, volatile organic compounds migrate to the production workshop or the atmosphere through cracks, posing a threat to the health of production personnel.

[0003] During the production and control work, it is required to monitor the horizontal structures such as production workshops, tank areas, road surfaces or ground to evaluate their service performance. A large number of cracks are generated after the above-mentioned horizontal structures are damaged. The concentration of volatile organic compounds in the structural cracks is an important basis for judging the degree of structural damage and formulating subsequent repair and management measures. At present, the evaluation of barrier barriers mainly adopts visual inspection and core sampling test methods. The visual inspection method mainly monitors the integrity of the structure and the degree of crack development by visual inspection. It has the disadvantages of high subjectivity and difficulty in quantifying monitoring data. The core sampling test method is mainly for areas with small cracks. After collecting the core sample of the structure, the permeability coefficient or diffusion coefficient of the structure is obtained through indoor tests. Since the area with more serious damage is the key focus area of ​​pollutant migration, the cracks in this area are connected and it is impossible to obtain a complete core sample, so the core sampling test method cannot be applied. Moreover, the concentration of organic matter in the damaged cracks of the structure is an important parameter to characterize the ability of pollutants in the soil under the horizontal structure to migrate to the outside world, which can truly reflect the migration of pollutants through the in-situ cracks. However, there is currently no corresponding detection method that can detect the concentration of organic matter in cracks after damage to horizontal structures such as production workshops, tank areas, road pavements or ground in production enterprises. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for detecting the concentration of volatile organic compounds in cracks of a barrier barrier in a contaminated site, which can detect the concentration of volatile organic compounds in the cracks of a damaged barrier barrier in situ and improve the detection accuracy.

[0005] To solve the above technical problems, the embodiments of the present invention adopt the following technical solutions:

[0006] The embodiment of the present invention provides a method for detecting the concentration of volatile organic compounds in cracks of a barrier of a contaminated site, comprising the following steps:

[0007] Step 10, opening a sampling hole at the crack of the horizontal barrier, wherein the sampling hole penetrates the horizontal barrier;

[0008] Step 20, placing a gas storage tank filled with inert gas in the sampling hole;

[0009] Step 30, opening the opening at the bottom of the gas storage tank, so that the volatile organic matter in the contaminated foundation diffuses into the gas storage tank; detecting the inert gas concentration at different heights in the gas storage tank in real time, and closing the opening at the bottom of the gas storage tank when the inert gas concentrations at different heights are the same;

[0010] Step 40, taking the gas storage tank out of the sampling hole and measuring the concentration of volatile organic compounds in the gas storage tank.

[0011] As a further improvement of the embodiment of the present invention, step 10 also includes continuing to open a moisture absorption hole of a preset depth below the sampling hole, and filling the moisture absorption hole from bottom to top to form a bottom sand layer, a middle filter layer and an upper sand layer.

[0012] As a further improvement of the embodiment of the present invention, step 10 further includes sealing the gap on the side wall of the sampling hole.

[0013] As a further improvement of the embodiment of the present invention, the following is further included between step 10 and step 20: step 11, closing the opening at the bottom of the gas storage tank, introducing inert gas from the first air inlet pipe at the top of the gas storage tank, so that the air in the gas storage tank is discharged through the first air outlet pipe; real-time detection of the inert gas concentration at different heights in the gas storage tank, when the inert gas concentrations at different heights are the same, closing the opening at the bottom of the gas storage tank, stopping the introduction of inert gas, and sealing the pipe openings of the first air inlet pipe and the first air outlet pipe.

[0014] As a further improvement of the embodiment of the present invention, the step 20 further includes: sealing the gap between the gas storage tank and the sampling hole.

[0015] As a further improvement of the embodiment of the present invention, step 20 further includes:

[0016] Cover the sampling hole with a sealing cover, and seal the joints between the sealing cover and the horizontal barrier. Inert gas is introduced into the sealing cover until all the air in the sealing cover is exhausted, and the introduction of inert gas is stopped.

[0017] As a further improvement of the embodiment of the present invention, in the step 20, after the introduction of the inert gas is stopped, the openings of the second air inlet pipe and the second air outlet pipe are closed.

[0018] As a further improvement of the embodiment of the present invention, in step 10, the center of the top surface of the sampling hole is located on the gap of the horizontal barrier.

[0019] As a further improvement of the embodiment of the present invention, the diameter of the tank body of the gas storage tank is 25 to 50 times the maximum width of the gap of the horizontal barrier.

[0020] As a further improvement of an embodiment of the present invention, the opening of the bottom of the gas tank specifically includes: rotating the rotating diaphragm at the bottom of the gas tank so that the rotating connecting hole coincides with the fixed connecting hole; the closing of the opening at the bottom of the gas tank specifically includes: rotating the rotating diaphragm at the bottom of the gas tank so that the rotating barrier completely covers the fixed connecting hole.

[0021] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0022] The present invention provides a method for detecting the concentration of volatile organic compounds in cracks of a barrier barrier of a contaminated site. A sampling hole is opened at the gap of a horizontal barrier barrier, and a gas tank is placed in the sampling hole to collect volatile organic compounds. After the volatile organic compounds are completely diffused into the gas tank, the concentration of the volatile organic compounds in the gas tank is measured. The method of the present invention collects volatile organic compounds in situ in the gap of the horizontal barrier barrier. The volatile organic compounds in the cracks can migrate to the tank body of the gas tank by diffusion, and the concentration of inert gas at different heights in the gas tank is detected in real time. When the concentration of inert gas at different heights is the same, the concentration of volatile organic compounds in the tank body is the same as the concentration of organic compounds in the cracks, thereby improving the detection accuracy and effectively overcoming the test error caused by the disturbance of the sample core in the existing coring test process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart of a method for detecting the concentration of volatile organic compounds in cracks of a barrier of a contaminated site according to an embodiment of the present invention;

[0024] Figure 2 is a front view of a gas storage tank in an embodiment of the method of the present invention;

[0025] Figure 3 (a) Yes Figure 2 A-A' cross-sectional schematic diagram of the bottom opening of the gas storage tank shown in a closed state;

[0026] Figure 3 (b) Yes Figure 2 A schematic diagram of a BB' cross section of the gas storage tank shown in a closed state with the bottom opening thereof;

[0027] Figure 3 (c) Figure 2 A schematic diagram of the A-A' cross section of the gas storage tank shown in the open state with the bottom opening;

[0028] Figure 3 (d) Figure 2A schematic diagram of a BB' cross section of the gas storage tank shown in the open state of the bottom opening;

[0029] Figure 3 (e) Figure 2 The C-C' cross-sectional schematic diagram of the gas storage tank shown is in a closed state with the bottom opening;

[0030] Figure 4 (a) Figure 2 A schematic diagram of the structure of the fixed barrier sheet of the fixed diaphragm;

[0031] Figure 4 (b) Figure 2 A schematic diagram of the structure of the rotating barrier of the rotating diaphragm;

[0032] Figure 4 (c) Yes Figure 3 (e) Schematic diagram of the D-D' section;

[0033] Figure 5 (a) is a top view of a horizontal barrier with cracks in an embodiment of the present invention;

[0034] Figure 5 (b) is a front view of a horizontal barrier barrier with cracks in an embodiment of the present invention;

[0035] Figure 6 is a front view of a horizontal barrier after the sampling holes and moisture absorption holes are constructed at the cracks in a specific example of the present invention;

[0036] Figure 7 It is a front view of the horizontal barrier after the moisture absorption holes are filled and the side walls of the sampling holes are sealed with films in a specific example of the present invention;

[0037] Figure 8 It is a structural schematic diagram of the testing process in the specific implementation of the present invention.

[0038] In the figure: gas storage tank 1, tank body 11, rotating shaft 12, rotating diaphragm 13, rotating connecting hole 131, rotating blocking piece 132, first limiting seal 133, fixed diaphragm 14, fixed connecting hole 141, fixed blocking piece 142, second limiting seal 143, sealing piston 15, first air inlet pipe 16, first air outlet pipe 17, helium measuring probe 18, servo motor 19, fixing buckle 110, bracket 111, horizontal blocking barrier 2, crack 21, contaminated foundation 3, pollutant 31, sampling hole 4, moisture absorption hole 5, bottom sand layer 51, middle filter layer 52, upper sand layer 53, diaphragm 6, sealing cover 7, information exchanger 71, second air inlet pipe 72, second air outlet pipe 73. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is described in detail below.

[0040] The embodiment of the present invention provides a method for detecting the concentration of volatile organic compounds in cracks of a barrier of a contaminated site, such as Figure 1 As shown, the following steps are included:

[0041] Step 10: opening a sampling hole 4 at the crack 21 of the horizontal barrier 2 , wherein the sampling hole 4 penetrates the horizontal barrier 2 .

[0042] Step 20 , placing the gas storage tank 1 filled with inert gas in the sampling hole 4 .

[0043] Step 30, open the opening at the bottom of the gas tank to allow the volatile organic matter in the contaminated foundation to diffuse into the gas tank. Real-time detection of the inert gas concentration at different heights in the gas tank, when the inert gas concentration at different heights is the same, close the opening at the bottom of the gas tank.

[0044] Step 40, taking the gas storage tank 1 out of the sampling hole 4, and measuring the concentration of volatile organic compounds in the gas storage tank.

[0045] Among them, the inert gas is preferably helium.

[0046] The method of this embodiment opens a sampling hole at the gap of the horizontal barrier, puts the gas tank into the sampling hole to collect volatile organic compounds, and after the volatile organic compounds are completely diffused into the gas tank, measures the concentration of the volatile organic compounds in the gas tank. The method of the present invention collects volatile organic compounds in situ at the gap of the horizontal barrier. The volatile organic compounds in the crack can migrate to the tank body of the gas tank through diffusion, and the concentration of volatile organic compounds in the tank body is the same as that in the crack. The concentration of volatile organic compounds in the crack of the damaged horizontal barrier can be accurately detected, the detection accuracy can be improved, and the test error caused by the disturbance of the sample core in the existing sampling test process can be effectively overcome, providing support for the service performance detection of similar horizontal barrier barriers in production enterprises.

[0047] The gas storage tank in this embodiment, such as Figure 2 As shown, the tank body 11 is cylindrical with a closed top and an open bottom. A fixed diaphragm 14 is provided at the bottom opening of the tank body 11. Figure 3 (b) and Figure 3 As shown in (d), the fixed diaphragm 14 includes a fixed disc, on which a plurality of fan-shaped fixed connecting holes 141 are evenly spaced, and between two adjacent fixed connecting holes 141 is a fan-shaped fixed blocking piece 142, and the fixed connecting holes 141 and the fixed blocking pieces 142 are equal in size and number. A rotating diaphragm 13 is provided in the tank body 11, and the rotating diaphragm 13 is located above the fixed diaphragm 14 and abuts against the fixed diaphragm 14. Figure 3 (a) and Figure 3As shown in (c), the rotating diaphragm 13 includes a rotating disc, on which a plurality of fan-shaped rotating communication holes 131 are evenly spaced, and between two adjacent rotating communication holes 131 there is a fan-shaped rotating blocking piece 132, and the rotating connecting holes 131 and the rotating blocking piece 132 are equal in size. The rotating connecting hole 131 and the fixed connecting hole 141 are equal in size, and the rotating blocking piece 132 and the fixed blocking piece 142 are equal in size.

[0048] This embodiment uses a rotating diaphragm and a fixed diaphragm arranged up and down with the same structure. The position of the rotating diaphragm relative to the fixed connecting hole is changed by rotating the rotating diaphragm. When the rotating diaphragm is opposite to the fixed connecting hole, the fixed connecting hole is covered, and the opening between the bottom of the tank body and the outside world is closed; when the rotating connecting hole is opposite to the fixed connecting hole, the fixed connecting hole is opened as the opening between the bottom of the tank body and the outside world. Moreover, multiple fixed connecting holes are closed or opened at the same time, and are evenly distributed at the bottom of the tank body. The rotating diaphragm rotates horizontally to close the opening. Compared with the pull-type opening and closing structure, it is easy to control, and the total opening area is large, the air intake per unit time is large and the air intake is uniform, which is conducive to the rapid and smooth entry of volatile organic compounds into the tank body.

[0049] Preferably, Figure 4 As shown, a first limiting seal 133 is provided at the bottom edge of the rotating barrier piece, and a second limiting seal 143 is provided at the top edge of the fixed barrier piece 142. When the bottom opening of the tank body is closed, the rotating diaphragm is rotated so that the first limiting seal of the rotating barrier piece abuts against the second limiting seal of the fixed barrier piece. The first limiting seal and the second limiting seal both play a role of rotation limiting, so that the rotating barrier piece completely covers the fixed connecting hole, and the rotating connecting hole is completely covered by the fixed barrier piece; moreover, the gap between the rotating barrier piece and the fixed barrier piece can be sealed to prevent the leakage of volatile organic matter in the tank body after the collection is completed, thereby affecting the detection accuracy.

[0050] The servo motor 19 is fixedly mounted on the top of the tank body 11 by a fixing buckle 110. The servo motor 19 is connected to one end of the rotating shaft 12, and the other end of the rotating shaft 12 is inserted into the tank body 11 and connected to the rotating diaphragm 13. The rotating shaft 12 and the through hole on the top surface of the tank body 11 are sealed by a sealing piston 15. The top of the tank body 11 is provided with a first air inlet pipe 16 connected to the inside of the tank body 11. One end of the first air outlet pipe 17 is located at the bottom of the tank body 11, and the other end is located outside the tank body 11. A plurality of helium measuring probes 18 are arranged at intervals along the height direction on the inner wall of the tank body 11. A bracket 111 is provided at the bottom of the tank body 11.

[0051] Considering that the volatile organic compounds in the cracks can migrate to the tank body 11 of the gas tank by diffusion, and achieving the same concentration of volatile organic compounds in the tank body 11 as the concentration of organic compounds in the cracks is the key to the characterization test of the concentration of organic compounds in the cracks. Preferably, before step 10, the diameter of the tank body of the gas tank is designed according to the width of the cracks of the horizontal barrier, and the height of the gas tank is designed according to the thickness of the horizontal barrier. Specifically, the diameter of the tank body 11 of the gas tank is 25 to 50 times the maximum width of the gap 21 of the horizontal barrier, and the height is the thickness of the horizontal barrier 21. If the diameter of the tank body 11 of the gas tank is too large, it will take a long time to achieve the balance between the concentration of volatile organic compounds in the tank body 11 and the concentration of organic compounds in the cracks, and the detection efficiency is low; moreover, if the diameter of the tank body 11 is too large, it is necessary to open a larger sampling hole on the horizontal barrier, which will cause greater damage to the horizontal barrier. If the diameter of the tank body 11 of the gas storage tank is too small, the amount of volatile organic matter collected in the tank body 11 is small, resulting in a large error in the detection result. Therefore, this embodiment uses a tank body 11 with a diameter of 25 to 50 times the maximum width of the gap 21 of the horizontal barrier, which can improve the detection accuracy and the detection efficiency.

[0052] In step 10, a sampling hole 4 is opened at the crack 21 of the horizontal barrier 2. Preferably, the sampling hole 4 is cylindrical, and the center of the top surface of the sampling hole 4 is located on the gap 21 of the horizontal barrier. This arrangement can ensure that the volatile pollutants in the contaminated foundation under the horizontal barrier can smoothly diffuse and migrate to the tank body 11 of the gas tank, shorten the equilibrium time between the concentration of volatile organic matter in the tank body 11 and the concentration of organic matter in the cracks, and improve the detection efficiency. The diameter of the sampling hole 4 is larger than the diameter of the tank body 11, and the difference does not exceed 0.5 cm. It is ensured that there is a gap between the tank body 11 and the sampling hole, so that the gas tank can be placed in the sampling hole and taken out of the sampling hole; at the same time, the gap between the tank body 11 and the sampling hole is small, which is convenient for blocking, so as to prevent the volatile organic matter in the contaminated foundation from migrating upward through the gap between the tank body 11 and the sampling hole.

[0053] As a preferred example, step 10 also includes, after the sampling hole 4 is opened, a moisture absorption hole 5 of a preset depth is further opened below the sampling hole 4 (i.e., the contaminated foundation under the horizontal barrier), and the bottom sand layer 51, the middle filter layer 52 and the upper sand layer 53 are sequentially filled in the moisture absorption hole 5 from bottom to top. Among them, quartz sand with a particle size of 2-8 mm is used to fill the bottom sand layer 51; inorganic water-absorbing materials, such as one or more of anhydrous calcium chloride and anhydrous magnesium chloride, are used to fill the middle filter layer 52; and quartz sand with a particle size of 5-8 mm is used to fill the upper sand layer 53. Among them, the quartz sand is washed with distilled water to remove floating dust and dried.

[0054] In this embodiment, a moisture absorption hole 5 is opened on the contaminated foundation below the sampling hole 4, and a bottom sand layer 51, a middle filter layer 52 and an upper sand layer 53 are filled. When the volatile organic matter in the contaminated foundation migrates upward, it first passes through the moisture absorption hole 5, and the moisture absorption hole absorbs the water vapor therein, so that the volatile organic matter entering the tank body 11 does not contain water vapor or contains very little water vapor, thereby eliminating the influence of water vapor on concentration detection and improving the detection accuracy of the concentration of volatile organic matter.

[0055] As a preferred example, step 10 also includes sealing the gap on the side wall of the sampling hole 4. Specifically, the gap can be sealed by sticking a diaphragm 6 on the sampling hole. The diaphragm 6 is made of glass fiber, Teflon and other materials that do not absorb organic matter. The diaphragm 6 is stuck to the side wall of the sampling hole 4 by an inorganic adhesive material. The inorganic adhesive material can use cement slurry, bentonite slurry or a mixture of the two. Measure the radial span of the crack. If the radial span of the crack is less than 1 / 3 of the circumference of the sampling hole 4, a strip-shaped diaphragm 6 is used to seal the side wall where the crack is located. If the radial span of the crack is greater than or equal to 1 / 3 of the circumference of the sampling hole 4, a circle of the side wall is sealed.

[0056] In this embodiment, the gaps in the side walls of the sampling hole are blocked to prevent volatile organic compounds in the contaminated foundation from entering the sampling hole and migrating through the gaps in the side walls of the sampling hole instead of entering the tank body 11, thereby affecting the detection of the concentration of volatile organic compounds; at the same time, the outside atmosphere is prevented from entering the sampling hole through the gaps in the side walls of the sampling hole and entering the tank body 11, thereby affecting the detection of the concentration of volatile organic compounds.

[0057] As a preferred example, between step 10 and step 20, it also includes: step 11, closing the opening at the bottom of the gas tank, and introducing helium from the first air inlet pipe 16 at the top of the gas tank, so that the air in the gas tank is discharged through the first air outlet pipe 17. The helium concentration at different heights in the gas tank is detected in real time by multiple helium measuring probes 18. When the helium concentration at different heights is the same, the opening at the bottom of the gas tank is closed, and the introduction of helium is stopped at the same time, and the first air inlet pipe 16 and the first air outlet pipe 17 are sealed, so that the tank body 11 is filled with helium. This embodiment uses inert gas helium as the background gas, which can overcome the interference of volatile organic compounds contained in the detection environment air on the detection. During the detection process, the volatile organic compounds in the cracks of the horizontal barrier diffuse into the tank body 11 of the gas tank. At the same time, the helium in the tank body 11 migrates to the pores of the soil of the underlying contaminated foundation, and finally achieves a balance between the concentration of volatile organic compounds in the tank body 11 and the concentration of volatile organic compounds in the underlying contaminated foundation.

[0058] Step 20, placing the gas storage tank 1 filled with helium in the sampling hole 4. The tank body 11 is coaxially arranged with the sampling hole 4, and the outer wall of the tank body does not contact the inner wall of the sampling hole.

[0059] Preferably, step 20 further includes: blocking the gap between the gas storage tank 1 and the top of the sampling hole 4. This prevents the volatile organic matter in the polluted foundation from migrating through the gap between the sampling hole and the tank body without entering the tank body 11, thereby affecting the detection of the concentration of the volatile organic matter; at the same time, it prevents the outside atmosphere from entering the sampling hole through the gap between the sampling hole and the tank body and entering the tank body 11, thereby affecting the detection of the concentration of the volatile organic matter.

[0060] Considering that there are also volatile organic compounds in the atmosphere of the production enterprise, in order to prevent the volatile organic compounds in the atmosphere from entering the tank body 11 through the gap between the side wall of the tank body 11 of the gas storage tank and the side wall of the sampling hole 4, as a preferred example, step 20 also includes:

[0061] Cover the sampling hole with a sealing cover 7, and seal the joint of the sealing cover and the horizontal barrier 2. Introduce helium into the sealing cover 7 until all the air in the sealing cover is exhausted, and stop introducing helium, so that the sealing cover 7 is filled with helium. Close the second air inlet pipe 72 and the second air outlet pipe 73.

[0062] In this embodiment, a sealing cover 7 is covered above the sampling hole and helium is introduced to isolate the tank body 11 of the gas storage tank from the surrounding atmospheric environment, thereby eliminating the influence of volatile organic compounds in the atmospheric environment on the detection results.

[0063] Step 30, collecting volatile organic compounds. Specifically, the opening at the bottom of the gas tank is opened to allow the volatile organic compounds in the contaminated foundation to diffuse into the gas tank. The helium concentration at different heights in the gas tank is detected in real time. When the helium concentration at different heights is the same, that is, the volatile organic compounds are evenly diffused in the tank body 11, the opening at the bottom of the gas tank is closed and the collection is stopped.

[0064] In step 30, the opening at the bottom of the gas storage tank is opened, specifically comprising: rotating the rotating diaphragm 13 at the bottom of the gas storage tank so that the rotating connecting hole 131 and the fixed connecting hole 141 overlap in height, such as Figure 3 (c) and Figure 3 As shown in (d), the inside and outside of the gas storage tank are connected. Volatile organic matter in the contaminated foundation enters the tank body through the fixed connecting hole 141 and the rotating connecting hole 131.

[0065] Closing the opening at the bottom of the gas storage tank specifically includes: rotating the rotating diaphragm 13 at the bottom of the gas storage tank, such as Figure 3 (a) and Figure 3 As shown in (b), the rotating blocking piece 132 and the fixed communicating hole 141 overlap in height, all the fixed communicating holes 141 are covered by the rotating blocking piece 132, and the rotating communicating holes 131 are covered by the fixed blocking piece 142, as shown in FIG. Figure 3 As shown in (e), the inside and outside of the gas storage tank are isolated.

[0066] Step 40, taking the gas storage tank 1 out of the sampling hole 4, and measuring the concentration of volatile organic matter in the gas storage tank, that is, obtaining the concentration of volatile organic matter in the crack of the horizontal barrier.

[0067] A specific example is provided below.

[0068] The preliminary site survey found that the concrete floor in the study area was severely cracked. Figure 5 (a) and Figure 5 As shown in (b), the volatile organic compounds in the underlying contaminated foundation 3 migrate upward, which is harmful to the health of production personnel. According to field tests, the maximum width of the concrete crack 21 in the study area is 0.5 cm, and the thickness of the cracked concrete floor is 25 cm.

[0069] According to the width of the cracks in the concrete floor and the thickness of the concrete floor, the diameter of the gas tank body is designed to be 15 cm and the height of the gas tank body is 25 cm.

[0070] 1. Construction of sampling holes 4

[0071] The diameter of the sampling hole 4 is designed to be 15.5 cm, and the height of the sampling hole 4 is designed to be 25.5 cm.

[0072] like Figure 6 As shown, after the sampling hole 4 is excavated, the contaminated foundation 3 under the horizontal barrier 2 is excavated to a depth of 15 cm to form a moisture absorption hole 5, as shown in FIG. Figure 6 (b) shown.

[0073] 2. Filling of moisture absorption holes 5

[0074] From bottom to top, quartz sand with a particle size of 2-8 mm is filled to form a bottom sand layer 51 with a thickness of 5 cm, anhydrous calcium chloride is filled to form a middle filter layer 52 with a thickness of 5 cm, and quartz sand with a particle size of 5-8 mm is filled to form an upper sand layer 53 with a thickness of 5 cm. Figure 7 shown.

[0075] 3. Seal the side wall of sampling hole 4

[0076] The diaphragm 6 made of glass fiber is pasted to the gap of the side wall of the sampling hole 4 by cement slurry to seal the gap. Figure 7 shown.

[0077] 4. Tank emptying

[0078] The servo motor 19 is controlled to work, and the rotating diaphragm 13 is driven to rotate through the rotating shaft 12, so that the rotating blocking piece 132 overlaps with the fixed connecting hole 141, and the rotating connecting hole 131 overlaps with the fixed blocking piece 142, so that the tank body is closed. Helium is introduced from the first air inlet pipe 16, and the helium enters the tank body. The air in the tank body enters the first air outlet pipe 17 from the bottom pipe opening, and then is discharged.

[0079] The signal values ​​of all helium measuring probes 18 are collected and converted into helium concentration values. When the helium concentration values ​​measured by all helium measuring probes 18 are the same, it means that the air in the tank is exhausted, the input of helium is stopped, and the pipe openings of the first air inlet pipe 16 and the first air outlet pipe 17 are closed.

[0080] 5. Gas tank 1 installation

[0081] Place the gas storage tank 1 in the sampling hole 4, and adjust the tank body position so that the center of the tank body cross section coincides with the center of the sampling hole cross section, and the outer wall of the tank body does not contact the inner wall of the sampling hole. The gap between the top edge of the sampling hole 4 and the tank body is sealed with a sealing ring.

[0082] 6. Coverage

[0083] The information exchanger 71 is installed on the sealing cover 7, and the sealing cover 7 is placed above the sampling hole 4, and the cross-sectional center of the sampling hole 4 coincides with the cross-sectional center of the sealing cover 7. The joint between the sealing cover 7 and the horizontal barrier 2 is sealed with cement mortar, such as Figure 8 Helium is introduced from the second air inlet pipe 72, and the helium enters the sealing cover 7, and the air in the sealing cover 7 is discharged from the second air outlet pipe 73. When the air in the sealing cover 7 is emptied, the introduction of helium is stopped, and the second air inlet pipe 72 and the second air outlet pipe 73 are closed.

[0084] 7. Gas collection

[0085] The servo motor 19 is controlled to work, and the rotating diaphragm 13 is driven to rotate via the rotating shaft 12, so that the rotating connecting hole 131 and the fixed connecting hole 141 overlap, and the volatile pollutants in the contaminated foundation are freely diffused into the tank body.

[0086] The information exchanger 71 collects the signal values ​​of all helium measuring probes 18 and converts them into helium concentration values. When the helium concentration values ​​measured by all helium measuring probes 18 are the same, it indicates that the volatile organic compounds are completely diffused in the tank. The servo motor 19 is controlled to work, and the rotating diaphragm 13 is driven to rotate through the rotating shaft, so that the rotating blocking piece 132 overlaps with the fixed connecting hole 141, and the rotating connecting hole 131 overlaps with the fixed blocking piece 142, so that the tank is closed.

[0087] 8. Disassembly of the device

[0088] Open the sealing cover 7 and take out the tank body. After the other components are disassembled, take them out of the site together.

[0089] 9. Volatile organic compound concentration test

[0090] The first gas outlet pipe 17 is connected to a gas chromatography-mass spectrometer to test and obtain the concentration of volatile organic compounds.

[0091] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above specific embodiments, and the descriptions in the above specific embodiments and the specification are only for further illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed for protection.

Claims

1. A method for detecting the concentration of volatile organic compounds in cracks of a barrier at a contaminated site, characterized in that: The following steps are involved: Step 10, opening a sampling hole (4) at the crack (21) of the horizontal barrier (2), wherein the sampling hole (4) penetrates the horizontal barrier (2); Step 20, placing the gas storage tank (1) filled with inert gas in the sampling hole (4); Step 30, opening the opening at the bottom of the gas storage tank, so that the volatile organic matter in the contaminated foundation diffuses into the gas storage tank; detecting the inert gas concentration at different heights in the gas storage tank in real time, and closing the opening at the bottom of the gas storage tank when the inert gas concentrations at different heights are the same; Step 40, taking the gas storage tank (1) out of the sampling hole (4) and measuring the concentration of volatile organic matter in the gas storage tank; The step 10 also includes sealing the gap on the side wall of the sampling hole (4); The step 20 further comprises: sealing the gap between the gas storage tank (1) and the sampling hole (4); In step 10, the center of the top surface of the sampling hole (4) is located on the crack (21) of the horizontal barrier.

2. The method for detecting the concentration of volatile organic compounds in cracks of a contaminated site barrier according to claim 1, characterized in that: The step 10 further comprises: continuing to open a moisture absorption hole (5) of a preset depth below the sampling hole (4), and filling the moisture absorption hole (5) from bottom to top to form a bottom sand layer (51), a middle filter layer (52) and an upper sand layer (53).

3. The method for detecting the concentration of volatile organic compounds in cracks of a contaminated site barrier according to claim 1, characterized in that: The method further includes the following steps between step 10 and step 20: step 11, closing the opening at the bottom of the gas storage tank, introducing an inert gas from a first air inlet pipe at the top of the gas storage tank, so that the air in the gas storage tank is discharged through a first air outlet pipe; detecting the concentration of the inert gas at different heights in the gas storage tank in real time, and when the concentrations of the inert gas at different heights are the same, closing the opening at the bottom of the gas storage tank, stopping the introduction of the inert gas, and sealing the pipe openings of the first air inlet pipe and the first air outlet pipe.

4. The method for detecting the concentration of volatile organic compounds in cracks of a contaminated site barrier according to claim 1, characterized in that: Step 20 also includes: A sealing cover (7) is placed above the sampling hole, and the joint between the sealing cover and the horizontal barrier (2) is sealed. Inert gas is introduced into the sealing cover (7) until all the air in the sealing cover is exhausted, and the introduction of inert gas is stopped.

5. The method for detecting the concentration of volatile organic compounds in cracks of a contaminated site barrier according to claim 4, characterized in that: In step 20, after the introduction of the inert gas is stopped, the openings of the second air inlet pipe and the second air outlet pipe are closed.

6. The method for detecting the concentration of volatile organic compounds in cracks of a contaminated site barrier according to claim 1, characterized in that: The diameter of the tank body (11) of the gas storage tank is 25 to 50 times the maximum width of the crack (21) of the horizontal barrier.

7. The method for detecting the concentration of volatile organic compounds in cracks of a contaminated site barrier according to claim 1, characterized in that: The opening at the bottom of the gas storage tank specifically comprises: rotating the rotating diaphragm (13) at the bottom of the gas storage tank so that the rotating communication hole (131) overlaps with the fixed communication hole (141); and the closing of the opening at the bottom of the gas storage tank specifically comprises: rotating the rotating diaphragm (13) at the bottom of the gas storage tank so that the rotating blocking plate (132) completely covers the fixed communication hole (141).

Images