Barrier construction for underground pollution vapor control and method of making same

Abstract

The application provides a barrier construction for underground pollution vapor control and a preparation method thereof. The barrier construction comprises a cushion layer, an adsorption layer and a barrier layer arranged in sequence from bottom to top. The barrier construction for underground pollution vapor control and the preparation method thereof have good barrier sealing performance, high durability and stability, and can effectively prevent harmful gases such as volatile organic compounds from escaping.

Description

Technical Field

[0001] This invention belongs to the field of pollution control and treatment technology, specifically, it relates to a barrier structure for controlling underground pollutant vapors and its preparation method. Background Technology

[0002] Currently, soil and groundwater remediation technologies in my country are experiencing rapid development. Various methods, including microbial remediation, phytoremediation, and chemical / physical remediation, are widely used, with a trend towards integrated approaches to improve efficiency and effectiveness. However, despite progress, the increasing complexity of pollution problems and underground geological structures makes it difficult to completely remove pollutants during investigation and remediation. Therefore, cutting off and controlling pollution sources and preventing the spread of pollution has become a new remediation strategy. Contaminated site barriers are a commonly used technology for controlling the migration and diffusion of pollutants in soil and groundwater. Barriers typically use highly alkaline cementitious materials such as cement to treat the in-situ soil, reducing its permeability and thus controlling the migration of pollutants to the external environment. Soil-bentonite, cement-bentonite, and cement-soil vertical barriers, as well as soil-geomembrane composite horizontal barriers, are frequently used in risk management engineering. However, these barriers have poor sealing performance and cannot effectively block underground pollutant vapors. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a barrier structure for controlling underground pollutant vapors and a method for preparing the same. The barrier structure has good sealing performance, strong durability and stability, and can effectively prevent the escape of harmful gases such as volatile organic compounds.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] In a first aspect, the present invention provides a barrier structure for controlling underground pollutant vapors, comprising a cushion layer, an adsorption layer and a barrier layer arranged sequentially from bottom to top.

[0006] As a further improvement of the present invention, the adsorption layer is made of activated carbon.

[0007] As a further improvement of the present invention, the thickness of the adsorption layer is 1 to 5 cm.

[0008] As a further improvement of the present invention, the barrier layer includes a first fiber layer, a polymer anti-permeability coating and a second fiber layer arranged sequentially from top to bottom.

[0009] As a further improvement of the present invention, both the first fiber layer and the second fiber layer are made of geotextile; the polymer anti-permeability coating is formed by applying emulsified asphalt, epoxy resin or high-density polyethylene.

[0010] As a further improvement of the present invention, the adsorption layer is provided with an exhaust pipe; the exhaust pipe includes several ring pipes, which are arranged at intervals from the inside to the outside with the pollution source as the center, and adjacent two ring pipes are connected by several branch pipes.

[0011] As a further improvement of the present invention, the diameter of the exhaust pipe is 0.3 to 0.5 times the thickness of the adsorption layer, and the layout density of the exhaust pipe is calculated according to formula (1):

[0012] Equation (1)

[0013] In the formula, L This indicates the density of exhaust pipe installations, expressed in m / m. 2 ; L 0 indicates the density of the foundation for the exhaust pipe layout, in m / m. 2 The value ranges from 0.2 to 0.6; A This represents the pollutant vapor concentration adjustment coefficient, with a value ranging from 1.1 to 1.5. This represents the arithmetic mean of soil pollutant concentrations at several soil survey points in a contaminated site, expressed in mg / kg. C ST Indicates the concentration threshold of soil pollutants at contaminated sites, in mg / kg; This represents the arithmetic mean of the groundwater pollutant concentrations at several groundwater survey points in the contaminated site, expressed in mg / L. C WT This indicates the concentration threshold of pollutants in the groundwater of a contaminated site, expressed in mg / L.

[0014] As a further improvement of the present invention, the spacing between the soil survey points is 10-40m, and the spacing between the groundwater survey points is 20-80m.

[0015] Secondly, the present invention also provides a method for preparing a barrier structure for controlling underground pollutant vapors, comprising the following steps:

[0016] Step 10: Lay a subbase over the foundation of the contaminated site;

[0017] Step 20: Lay an adsorption layer on top of the subbase, and simultaneously lay an exhaust pipe in the adsorption layer.

[0018] Step 30: Lay a barrier layer on top of the adsorption layer;

[0019] Step 40: Lay a concrete floor over the barrier layer.

[0020] As a further improvement of the present invention, in step 30, the prefabricated barrier blocks are spliced ​​and laid to form a barrier layer, and the adjacent two prefabricated barrier blocks are treated by hot melt welding process.

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

[0022] (1) The barrier structure for controlling underground pollutant vapors provided by this invention and its preparation method are as follows: The barrier structure is horizontally arranged and includes a cushion layer, an adsorption layer, and a barrier layer arranged sequentially from bottom to top. The cushion layer is located at the bottom as a support, improving the stability and durability of the entire barrier structure. The adsorption layer is located above the cushion layer, and the barrier layer is located above the adsorption layer. Underground pollutant vapors first pass through the cushion layer and rise to the adsorption layer. Most of the pollutant vapors are adsorbed by the adsorption layer, and only a very small amount of pollutant vapors pass through the adsorption layer to reach the bottom of the barrier layer, where they are blocked by the barrier layer and cannot rise to the ground surface. The horizontally arranged barrier structure provided by this embodiment has good sealing performance and can effectively prevent the escape of harmful gases such as volatile organic compounds. It is easy to prepare, reducing construction complexity and time costs. For buildings constructed on contaminated sites, the horizontally arranged barrier structure provided by this embodiment can significantly reduce the concentration of pollutants in indoor air and improve the safety of the living and working environment. By eliminating or mitigating the impact of pollution, land that was previously unusable can regain its value for development and utilization, promoting urban renewal and development, while providing safer safeguards for already restored sites.

[0023] (2) The present invention lays exhaust pipes in the adsorption layer and optimizes the layout density of exhaust pipes according to the concentration of pollutants in the contaminated site. This can effectively control the vapor concentration of pollutant vapor in the in-situ soil pores, adsorption layer and exhaust pipes, and exhaust the pollutant vapor from the site pollution source area to the barrier structure, thereby reducing the breakdown time of the adsorption layer in the pollution source area and extending the overall service life of the barrier structure. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the barrier structure provided in an embodiment of the present invention;

[0025] Figure 2 for Figure 1 A schematic diagram of the exhaust pipe structure.

[0026] In the diagram, 1 is the cushion layer, 2 is the adsorption layer, 3 is the barrier layer, 31 is the first fiber layer, 32 is the polymer anti-permeability coating, 32 is the second fiber layer, 4 is the exhaust pipe, 401 is the ring pipe, 402 is the branch pipe, 403 is the main pipe, 5 is the concrete floor, and 6 is the boundary of the barrier structure. Detailed Implementation

[0027] The technical solution of the present invention will be described in detail below.

[0028] This invention provides a barrier structure for controlling underground pollutant vapors, such as... Figure 1 As shown, the structure comprises, from bottom to top, a cushion layer 1, an adsorption layer 2, and a barrier layer 3. The cushion layer 1 can be formed by laying sand and gravel. Located at the bottom, the cushion layer 1 provides support, improving the stability of the entire barrier structure and protecting the barrier layer. Simultaneously, because the cushion layer 1 is formed by laying sand and gravel, the gaps between the gravel particles facilitate the uniform distribution of pollutant vapors within the cushion layer 1, i.e., a uniform distribution below the adsorption layer, preventing accumulation in one area and thus reducing the adsorption burden on the adsorption layer and affecting its effectiveness. The adsorption layer 2 is located above the cushion layer 1. Underground pollutant vapors rise to the adsorption layer after passing through the cushion layer, where they are adsorbed. The barrier layer 3 is located above the adsorption layer 2. This barrier layer blocks the very small amount of pollutant vapors that may pass through the adsorption layer, preventing them from rising to the surface.

[0029] Preferably, the adsorption layer 2 is made of activated carbon. Preferably, the thickness of the adsorption layer 2 is 1 to 5 cm.

[0030] As a preferred embodiment, the barrier layer 3 includes a first fiber layer 31, a polymer anti-permeability coating 32, and a second fiber layer 33 arranged sequentially from top to bottom. Both the first fiber layer 31 and the second fiber layer 33 are made of geotextile. The polymer anti-permeability coating 32 is formed by applying emulsified asphalt, epoxy resin, or high-density polyethylene.

[0031] In this embodiment, an emulsified asphalt, epoxy resin, or high-density polyethylene is applied between the first and second fiber layers to form a polymeric anti-permeability coating 32. This coating has extremely low permeability and can effectively prevent pollutant vapors from passing through. The first fiber layer 31 and the second fiber layer 33, made of geotextile, are located on the upper and lower surfaces of the polymeric anti-permeability coating 32, respectively, protecting the intermediate layer. The entire barrier layer has high tensile and tear strength, resisting underground physical stresses such as soil pressure and groundwater flow. It also exhibits stable performance under different temperature conditions and is not prone to deformation or cracking. Furthermore, it has good corrosion resistance to common pollutants and chemicals, maintaining its anti-permeability function for a long time in polluted environments.

[0032] Preferably, the barrier structure in this embodiment also includes a gas sensor, which is located between the adsorption layer 2 and the barrier layer 3. By using the gas sensor to detect the concentration of pollutant vapor below the barrier layer in real time, the barrier can be maintained in a timely manner.

[0033] As a preferred example, the adsorption layer 2 is provided with an exhaust pipe 4. The lower surface of the exhaust pipe 4 has an air inlet, and the outlet end of the exhaust pipe 4 is located above the ground surface. Pollutant vapor rises into the adsorption layer after being distributed by the pad layer 1, then enters the exhaust pipe 4 through the air inlet, and is discharged above the ground surface under the guidance of the exhaust pipe 4, where it is collected. The exhaust pipe 4 guides most of the pollutant vapor to the ground surface, facilitating collection and treatment, reducing the burden on the adsorption layer, and preventing the adsorption layer from becoming saturated and causing pollutant vapor to accumulate below the barrier layer. If the accumulation is too large, it may escape from both sides of the barrier layer to the ground surface or into structures, causing harm to users.

[0034] Preferred, such as Figure 2 As shown, the exhaust duct 4 includes several ring pipes 401, which are arranged sequentially from the inside out with the pollution source as the center. Adjacent ring pipes 401 are connected by several branch pipes 402. This arrangement allows for zoning based on pollutant concentration in the contaminated site, enabling the collection of pollutants from different zones. Furthermore, it facilitates zoned maintenance during later stages. Compared to other arrangements, such as parallel strip distributions, this reduces the impact of later localized maintenance and repairs on the entire barrier layer structure. One ring pipe 401 is connected to one end of a main pipe 403, the other end of which extends above the ground. Preferably, the outermost ring pipe is connected to the main pipe 403.

[0035] Preferably, the diameter of the exhaust pipe 4 is 0.3 to 0.5 times the thickness of the adsorption layer 2. This ensures that the exhaust pipe 4 is completely enclosed in the adsorption filler of the adsorption layer 2, avoiding direct contact between the exhaust pipe 4 and the cushion layer 1 and the barrier layer 3 after structural deformation caused by foundation settlement, which would cause puncture or wear of the cushion layer 1 and the barrier layer 3, thereby weakening the air-tight function of the barrier structure.

[0036] Preferably, the layout density of the exhaust pipe 4 is calculated according to formula (1):

[0037] Equation (1)

[0038] In the formula, L This indicates the density of exhaust pipe installations, specifically the effective length of exhaust pipes per unit area of ​​the contaminated site, expressed in meters (m / m). 2 . L 0 indicates the density of the foundation for the exhaust pipe layout, in m / m. 2 The value ranges from 0.2 to 0.6. A This represents the pollutant vapor concentration adjustment factor, with a value ranging from 1.1 to 1.5. The more types of pollutants, the higher the adjustment factor. A The larger the value, the better. This represents the arithmetic mean of soil pollutant concentrations at several soil survey points at a contaminated site, expressed in mg / kg. C ST This indicates the concentration threshold of soil pollutants at a contaminated site, expressed in mg / kg. This represents the arithmetic mean of the groundwater pollutant concentrations at several groundwater survey points at the contaminated site, expressed in mg / L. C WT This indicates the concentration threshold of pollutants in the groundwater of a contaminated site, expressed in mg / L.

[0039] This embodiment optimizes the layout density of the exhaust pipe 4 according to the concentration of pollutants in the contaminated site. It can effectively control the vapor concentration of pollutant vapor in the in-situ soil pores, adsorption layer 3 and exhaust pipe 4, and exhaust the pollutant vapor from the pollution source area of ​​the site to the barrier structure, thereby reducing the breakdown time of adsorption layer 3 in the pollution source area and extending the overall service life of the barrier structure.

[0040] Preferably, the spacing between soil survey points is 10–40 m, and the spacing between groundwater survey points is 20–80 m.

[0041] This invention also provides a method for preparing a barrier structure for controlling underground pollutant vapors, comprising the following steps:

[0042] Step 10: Lay a cushion layer 1 on top of the foundation of the contaminated site.

[0043] Step 20: Lay an adsorption layer 2 on top of the pad 1, and at the same time, lay an exhaust pipe 4 in the adsorption layer 2.

[0044] Step 30: Lay a barrier layer 3 on top of the adsorption layer 2.

[0045] Step 40: Lay concrete floor 5 on top of barrier layer 3.

[0046] As a preferred embodiment, the barrier layer 3 includes a first fiber layer 31, a polymer anti-permeability coating 32, and a second fiber layer 33 arranged sequentially from top to bottom. Both the first fiber layer 31 and the second fiber layer 33 are made of geotextile. The polymer anti-permeability coating 32 is formed by applying emulsified asphalt, epoxy resin, or high-density polyethylene.

[0047] In step 30, there are two options for laying the barrier layer 3:

[0048] In the first method, a second fiber layer 33 is laid on top of the adsorption layer 2, a polymer anti-permeability coating 32 is coated on the upper surface of the second fiber layer 33, and a first fiber layer 31 is laid on the upper surface of the polymer anti-permeability coating 32 to form a barrier layer.

[0049] The second method involves first preparing prefabricated barrier blocks. Specifically, a polymer anti-permeability coating is applied to the upper surface of the second fiber block, and then the first fiber block is laid on top of this coating to form the prefabricated barrier block. The prefabricated barrier blocks are then laid on top of the adsorption layer and spliced ​​together to form the barrier layer. Compared to the first method, this second approach offers higher construction efficiency. Adjacent prefabricated barrier blocks are joined using a hot-melt welding process to ensure there are no gaps or defects between them, effectively blocking pollutant vapors.

[0050] The method for preparing a barrier structure for controlling underground pollutant vapors provided in the above embodiments involves a horizontally arranged barrier structure, comprising a base layer, an adsorption layer, and a barrier layer arranged sequentially from bottom to top. The base layer is located at the bottom as a support, improving the stability and durability of the entire barrier structure. The adsorption layer is located above the base layer, and the barrier layer is located above the adsorption layer. Underground pollutant vapors first pass through the base layer and rise to the adsorption layer. Most of the pollutant vapors are adsorbed by the adsorption layer, and only a very small amount of pollutant vapors pass through the adsorption layer to reach the area below the barrier layer, where they are blocked by the barrier layer and cannot rise to the surface. The horizontal barrier structure prepared by the method of this invention has good sealing performance and can effectively prevent the escape of harmful gases such as volatile organic compounds. It is easy to prepare, reducing construction complexity and time costs. For buildings constructed on contaminated sites, the horizontal barrier structure prepared by the method of this embodiment can significantly reduce the concentration of pollutants in indoor air, improving the safety of the living and working environment. By eliminating or mitigating the impact of pollution, land that was previously unusable can regain its value for development and utilization, promoting urban renewal and development, while providing safer safeguards for already restored sites.

[0051] The following is a specific example.

[0052] Example 1

[0053] A wastewater treatment plant in a chemical industrial park leaked, causing pollution to surrounding land. Pollutants such as vinyl chloride in the soil and groundwater exceeded safe levels. To prevent these harmful volatile organic compounds from evaporating and rising as soil vapor, thus affecting the surrounding environment and residents' health, a pollutant vapor barrier structure was constructed within the contaminated area.

[0054] A pollution survey was conducted at the contaminated site, with soil survey points spaced 40m apart and groundwater survey points spaced 80m apart. Based on the soil and groundwater survey results, the maximum concentration of vinyl chloride in the soil and groundwater exceeded the threshold concentration (an unacceptable concentration for human health), with an area exceeding the limit of approximately 600m². 2 This allows us to determine the boundaries of horizontally arranged barrier structures.

[0055] The maximum concentration of vinyl chloride in soil was 25 times the soil vinyl chloride threshold, and the maximum concentration of vinyl chloride in groundwater was 237 times the soil vinyl chloride threshold. L The value of 0 is 0.4m / m 2 , A The value is 1.3. Based on equation (1), the layout density of the exhaust pipes is calculated to be 1.96 m / m. 2 Therefore, based on the site area, the length of the exhaust pipe is calculated to be 600 × 1.96 = 1170 m. To ensure the exhaust pipe can capture pollutant vapors to the maximum extent, it is divided into two loops arranged at intervals from the inside out, centered on the pollution source. These two loops are connected by eight branch pipes, such as... Figure 2 As shown. The lengths of the two ring pipes are 450m and 250m respectively, and the total length of the eight branch pipes is 470m.

[0056] Considering future planning, the site will be developed into a production plant. Based on the planned foundation depth of 3 meters, and considering the extent of groundwater pollution, the soil within a 3.35-meter horizontal barrier will be excavated first. After excavation, a 30cm thick sand and gravel layer will be laid at the bottom of the excavated pit. Following this, an absorbent layer will be laid, with exhaust pipes embedded within it. The absorbent layer will be 5cm thick, and the exhaust pipes will have a diameter 0.5 times the absorbent layer thickness (2.5cm). After the absorbent layer is completed, a 2cm thick emulsified asphalt layer will be laid on top, compacted using light rollers, and then a non-woven fabric layer will be laid as a protective layer. Finally, cement concrete will be poured to form a concrete floor, serving as the foundation for the upper structures.

[0057] The effectiveness of the vapor barrier structure was verified using gas detection methods. Specifically, after the foundation pit excavation was completed, the vinyl chloride content in the gas at the bottom of the pit was monitored. After the vapor barrier structure was constructed, vinyl chloride concentration was detected above the barrier structure and at the main exhaust outlet. Detection was conducted once a month, and the gas concentrations are shown in the table below.

[0058] Table 1. Detection concentration of vinyl chloride in gases at different locations (mg / L)

[0059] Monitoring location / time (month) 0 1 2 Bottom of the excavation pit (mg / L) 0.3 - - Above the barrier structure (mg / L) Not detected Not detected Not detected Main discharge outlet (mg / L) 0.23 0.27 0.33

[0060] Based on the on-site construction situation, after the excavation of the foundation pit was completed, there was a distinct pungent odor at the bottom of the pit. After the vapor barrier structure was built, the odor was significantly eliminated. Furthermore, according to the test results, no vinyl chloride was detected above the vapor barrier structure, indicating a significant barrier effect.

[0061] The verification data based on the above construction parameters and barrier effects show that the barrier structure effectively blocked the upward volatilization of volatile organic compounds (VOCs) from the contaminated site, significantly improving the surrounding environment and the health of residents. Monitoring data shows that the pollutant concentration at the main exhaust outlet increased significantly and continuously, which facilitates the organized emission after treatment. The barrier structure achieved the expected barrier effect, ensuring environmental safety.

[0062] The foregoing has shown and described 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 specific embodiments described above. The specific embodiments and descriptions in the specification are merely for further illustrating the principles of the invention. The basic principles, main features, and advantages of the present invention have been shown and described above without departing from the spirit and scope of the invention. Those skilled in the art should understand that various changes and modifications will be made, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A barrier structure for controlling underground pollutant vapors, characterized in that, It includes a padding layer (1), an adsorption layer (2), and a barrier layer (3) arranged from bottom to top. The subbase (1) is formed by laying sand and gravel; The adsorption layer (2) is provided with an exhaust pipe (4); the lower surface of the exhaust pipe (4) is provided with an air inlet, and the outlet end of the exhaust pipe (4) is located above the ground surface; the exhaust pipe (4) includes several ring pipes (401), the ring pipes (401) are arranged from the inside to the outside with the pollution source as the center, and adjacent two ring pipes (401) are connected by several branch pipes (402); The diameter of the exhaust pipe (4) is 0.3 to 0.5 times the thickness of the adsorption layer (2), and the layout density of the exhaust pipe (4) is calculated according to formula (1): Equation (1) In the formula, L This indicates the density of exhaust pipe installations, expressed in m / m. 2 ; L 0 indicates the density of the foundation for the exhaust pipe layout, in m / m. 2 The value ranges from 0.2 to 0.6; A This represents the pollutant vapor concentration adjustment coefficient, with a value ranging from 1.1 to 1.

5. This represents the arithmetic mean of soil pollutant concentrations at several soil survey points in a contaminated site, expressed in mg / kg. C ST Indicates the concentration threshold of soil pollutants at contaminated sites, in mg / kg; This represents the arithmetic mean of the groundwater pollutant concentrations at several groundwater survey points in the contaminated site, expressed in mg / L. C WT This indicates the concentration threshold of pollutants in the groundwater of a contaminated site, expressed in mg / L.

2. The barrier structure according to claim 1, characterized in that, The adsorption layer (2) is made of activated carbon.

3. The barrier structure according to claim 1, characterized in that, The thickness of the adsorption layer (2) is 1 to 5 cm.

4. The barrier structure according to claim 1, characterized in that, The barrier layer (3) includes a first fiber layer (31), a polymer anti-permeability coating (32), and a second fiber layer (33) arranged sequentially from top to bottom.

5. The barrier structure according to claim 4, characterized in that, The first fiber layer (31) and the second fiber layer (33) are both made of geotextile; the polymer anti-permeability coating (32) is formed by applying emulsified asphalt, epoxy resin or high-density polyethylene.

6. The barrier structure according to claim 1, characterized in that, The spacing between the soil survey points is 10–40 m, and the spacing between the groundwater survey points is 20–80 m.

7. A method for preparing a barrier structure for controlling underground pollutant vapors, characterized in that, Includes the following steps: Step 10, lay a cushion layer (1) on top of the foundation of the contaminated site; the cushion layer (1) is formed by laying sand and gravel; Step 20: Lay an adsorption layer (2) on top of the pad (1) and lay an exhaust pipe (4) in the adsorption layer (2). Step 30: Lay a barrier layer (3) on top of the adsorption layer (2); Step 40: Lay a concrete floor (5) on top of the barrier layer (3); The lower surface of the exhaust pipe (4) is provided with an air inlet, and the outlet end of the exhaust pipe (4) is located above the ground surface; the exhaust pipe (4) includes several ring pipes (401), the ring pipes (401) are arranged from the inside to the outside with the pollution source as the center, and adjacent two ring pipes (401) are connected by several branch pipes (402); The diameter of the exhaust pipe (4) is 0.3 to 0.5 times the thickness of the adsorption layer (2), and the layout density of the exhaust pipe (4) is calculated according to formula (1): Equation (1) In the formula, L This indicates the density of exhaust pipe installations, expressed in m / m. 2 ; L 0 indicates the density of the foundation for the exhaust pipe layout, in m / m. 2 The value ranges from 0.2 to 0.6; A This represents the pollutant vapor concentration adjustment coefficient, with a value ranging from 1.1 to 1.

5. This represents the arithmetic mean of soil pollutant concentrations at several soil survey points in a contaminated site, expressed in mg / kg. C ST Indicates the concentration threshold of soil pollutants at contaminated sites, in mg / kg; This represents the arithmetic mean of the groundwater pollutant concentrations at several groundwater survey points in the contaminated site, expressed in mg / L. C WT This indicates the concentration threshold of pollutants in the groundwater of a contaminated site, expressed in mg / L.

8. The preparation method according to claim 7, characterized in that, In step 30, the prefabricated barrier blocks are spliced ​​and laid to form a barrier layer (3), and the adjacent two prefabricated barrier blocks are treated by hot melt welding process.

Images