Barrier structure for underground pollution steam control and preparation method thereof

Abstract

The invention provides a barrier structure for underground pollution steam control and a preparation method of the barrier structure. The barrier structure comprises a cushion layer, an adsorption layer and a barrier layer which are sequentially arranged from bottom to top. According to the barrier structure for underground pollution steam control and the preparation method of the barrier structure, the barrier sealing performance is good, durability and stability are high, and volatile organic compounds and other harmful gases can be effectively prevented from escaping.

Description

Technical Field

[0001] The present invention belongs to the technical field of pollution control and treatment. Specifically, it relates to a barrier structure for controlling underground pollution vapor and a preparation method thereof. Background Art

[0002] At present, the technologies for remediating contaminated soil and groundwater are undergoing a rapid development stage in China. A variety of methods such as microbial remediation, phytoremediation, and chemical / physical remediation have been widely applied, and tend to adopt comprehensive means to improve the treatment efficiency and effect. However, despite certain progress, in the face of increasingly complex pollution problems and complex underground stratum structures, it is difficult to completely remove pollutants during the investigation and remediation implementation processes. Therefore, cutting off and controlling pollution sources and preventing the spread of pollution have become a new remediation idea. The pollution site barrier can effectively control the migration and diffusion of pollutants in soil and groundwater, and is a commonly used pollution site treatment technology. The barrier usually uses highly alkaline cementitious materials to treat in-situ soil, reducing the permeability coefficient of in-situ soil, thereby controlling the migration of pollutants to the external environment of the site. Soil-bentonite, cement-bentonite, cement-soil vertical barrier and soil-geomembrane composite horizontal barrier are more commonly used in risk control projects. However, the above-mentioned barriers have poor sealing performance and cannot effectively block underground pollutant vapor. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: to provide a barrier structure for controlling underground pollution vapor and a preparation method thereof, 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 technical problems, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a barrier structure for controlling underground pollution vapor, including a cushion layer, an adsorption layer, and a barrier layer arranged in sequence from bottom to top.

[0005] As a further improvement of the present invention, the adsorption layer is made of activated carbon.

[0006] As a further improvement of the present invention, the thickness of the adsorption layer is 1 - 5 cm.

[0007] As a further improvement of the present invention, the barrier layer includes a first fiber layer, a polymer impermeable coating, and a second fiber layer arranged in sequence from top to bottom.

[0008] As a further improvement of the present invention, both the first fiber layer and the second fiber layer are made of geotextile; the polymer impermeable coating is formed by coating emulsified asphalt, epoxy resin, or high-density polyethylene.

[0009] As a further improvement of the present invention, an exhaust duct is provided in the adsorption layer; the exhaust duct includes a plurality of annular ducts, and the annular ducts are arranged at intervals from the inside to the outside with the pollution source as the center, and adjacent two annular ducts are communicated through a plurality of branch ducts.

[0010] As a further improvement of the present invention, the diameter of the exhaust duct is 0.3 to 0.5 times the thickness of the adsorption layer, and the layout density of the exhaust duct is calculated according to formula (1): Formula (1) In the formula, L represents the layout density of the exhaust duct, and the unit is m / m 2 ; L 0 represents the basic layout density of the exhaust duct, and the unit is m / m 2 , and the value ranges from 0.2 to 0.6; A represents the pollutant vapor concentration adjustment coefficient, and the value ranges from 1.1 to 1.5; represents the arithmetic mean of the soil pollutant concentrations at several soil investigation points in the polluted site, and the unit is mg / kg; C ST represents the concentration threshold of the soil pollutants in the polluted site, and the unit is mg / kg; represents the arithmetic mean of the groundwater pollutant concentrations at several groundwater investigation points in the polluted site, and the unit is mg / L; C WT represents the concentration threshold of the groundwater pollutants in the polluted site, and the unit is mg / L.

[0011] As a further improvement of the present invention, the spacing between the soil investigation points is 10 to 40 m, and the spacing between the groundwater investigation points is 20 to 80 m.

[0012] Second, the present invention also provides a preparation method for a barrier structure for controlling underground pollution vapor, including the following steps: Step 10, laying a cushion layer above the foundation of the polluted site; Step 20, laying an adsorption layer above the cushion layer, and at the same time laying an exhaust duct in the adsorption layer; Step 30, laying a barrier layer above the adsorption layer; Step 40, laying a concrete floor above the barrier layer.

[0013] As a further improvement of the present invention, in step 30, prefabricated barrier blocks are spliced and laid to form a barrier layer, and the adjacent two prefabricated barrier blocks are processed by a hot melt welding process.

[0014] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) The barrier structure for controlling underground polluted vapor and its preparation method provided by the present invention are horizontally arranged, including a cushion layer, an adsorption layer and a barrier layer arranged in sequence 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. The underground pollutant vapor first rises through the cushion layer to the adsorption layer, and most of the pollutant vapor is adsorbed by the adsorption layer. Only a very small amount of pollutant vapor passes through the adsorption layer to reach the lower part of the barrier layer and is blocked by the barrier layer, unable to rise through the barrier layer to the ground surface. The horizontally arranged barrier structure provided by the embodiment of the present invention has good sealing performance, can effectively prevent harmful gases such as volatile organic compounds from escaping. It is easy to prepare, reducing the construction complexity and time cost. For buildings built on polluted sites, the horizontally arranged barrier structure provided by this embodiment can significantly reduce the pollutant concentration in indoor air and improve the safety of the living and working environment. By eliminating or reducing the pollution impact, the land that was originally unusable can regain the value of development and utilization, promoting urban renewal and development, and at the same time providing more secure safeguard measures for the already repaired sites.

[0015] (2) The present invention lays exhaust pipes in the adsorption layer and optimizes and adjusts the layout density of the exhaust pipes according to the concentration of pollutants in the polluted site, which can effectively regulate the vapor concentration of polluted vapor in the in-situ soil pores, adsorption layer and exhaust pipes, discharge the polluted vapor in the pollution source area of the site out of the barrier structure, thereby reducing the breakthrough time of the adsorption layer in the pollution source area and prolonging the overall service life of the barrier structure for airtight service. Brief Description of the Drawings

[0016] Figure 1 is a schematic structural diagram of the barrier structure provided by the embodiment of the present invention; Figure 2 is Figure 1 the schematic structural diagram of the exhaust pipe in

[0017] In the figure, cushion layer 1, adsorption layer 2, barrier layer 3, first fiber layer 31, high molecular anti-permeation coating 32, second fiber layer 32, exhaust pipe 4, ring pipe 401, branch pipe 402, main pipe 403, concrete floor 5, boundary 6 of the barrier structure. Detailed Embodiments

[0018] The technical solution of the present invention will be described in detail below.

[0019] The embodiment of the present invention provides a barrier structure for controlling underground polluted vapor, such as Figure 1As shown in the figure, it includes a cushion layer 1, an adsorption layer 2, and a barrier layer 3 arranged in sequence from bottom to top. Among them, the cushion layer 1 can be formed by laying sand and gravel. The cushion layer 1 is located at the bottom as a support to improve the stability of the entire barrier structure and protect the barrier layer. At the same time, since the cushion layer 1 is formed by laying sand and gravel, there are specific gaps between the sand and gravel, which facilitates the uniform distribution of pollutant vapors in the cushion layer 1, that is, uniformly distributed under the adsorption layer, rather than accumulating in a certain place, increasing the adsorption burden of the adsorption layer at that place and affecting the adsorption effect. The adsorption layer 2 is located above the cushion layer 1. The underground pollutant vapors rise to the adsorption layer after passing through the cushion layer, and the adsorption layer 2 adsorbs the pollutant vapors. The barrier layer 3 is located above the adsorption layer 2. The barrier layer blocks the extremely small amount of pollutant vapors that pass through the adsorption layer, so that the pollutant vapors cannot pass through the barrier layer and rise to the ground surface.

[0020] Preferably, the adsorption layer 2 is made of activated carbon. Preferably, the thickness of the adsorption layer 2 is 1 - 5 cm.

[0021] As a preferred example, the barrier layer 3 includes a first fiber layer 31, a polymer impermeable coating 32, and a second fiber layer 33 arranged in sequence from top to bottom. Among them, both the first fiber layer 31 and the second fiber layer 33 are made of geotextile. The polymer impermeable coating 32 is formed by coating emulsified asphalt, epoxy resin, or high-density polyethylene.

[0022] In this embodiment, the polymer impermeable coating 32 is formed by coating emulsified asphalt, epoxy resin, or high-density polyethylene between the first fiber layer and the second fiber layer, which has an 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 surface and the lower surface of the polymer impermeable coating 32 respectively, protecting the polymer impermeable coating 32 in the middle. The entire barrier layer has a high tensile strength and tear strength, and can resist underground physical stresses, such as soil pressure and groundwater flow. At the same time, it has stable performance under different temperature conditions and is not prone to deformation or cracking. It has good corrosion resistance to common pollutants and chemical substances and can maintain the impermeable function in a polluted environment for a long time.

[0023] Preferably, the barrier structure of this embodiment further includes a gas sensor, and the gas sensor is located between the adsorption layer 2 and the barrier layer 3. The gas sensor is used to detect the concentration of pollutant vapors below the barrier layer in real time, and the barrier can be maintained in a timely manner.

[0024] As a preferred example, an exhaust duct 4 is provided in the adsorption layer 2. An air inlet hole is provided on the lower surface of the exhaust duct 4, and the outlet end of the exhaust duct 4 is located above the ground surface. The pollutant vapor rises into the adsorption layer after being distributed by the cushion layer 1, and then enters the exhaust duct 4 through the air inlet hole. Under the guiding action of the exhaust duct 4, it is discharged above the ground surface and thus collected. By providing the exhaust duct 4, most of the pollutant vapor can be discharged above the ground surface, which is convenient for collection and treatment, reduces the burden on the adsorption layer, and prevents the pollutant vapor from accumulating under the barrier layer due to the saturation of the adsorption layer. When the accumulation amount is too large, it will escape from both sides of the barrier layer to the ground surface or into the structure, causing physical harm to users.

[0025] Preferably, as Figure 2 shown, the exhaust duct 4 includes a plurality of annular pipes 401, and the annular pipes 401 are arranged at intervals from the inside to the outside in sequence with the pollution source as the center. A plurality of branch pipes 402 are connected between two adjacent annular pipes 401. Such an arrangement can partition according to the concentration of pollutants in the polluted site, so as to collect pollutants in different partitions; in addition, during the later maintenance process, it is also convenient to perform partition maintenance in units of partitions. Compared with other setting methods, such as parallel strip distribution, it can reduce the impact of later local maintenance and repair on the entire barrier structure. One of the annular pipes 401 is connected to one end of the main pipe 403, and the other end of the main pipe 403 extends out of the ground. Preferably, the outermost annular pipe is connected to the main pipe 403.

[0026] Preferably, the diameter of the exhaust duct 4 is 0.3 to 0.5 times the thickness of the adsorption layer 2. Thus, it is ensured that the exhaust duct 4 is completely wrapped in the adsorption filler of the adsorption layer 2. After avoiding the structural deformation caused by the foundation settlement, the direct contact between the exhaust duct 4 and the cushion layer 1 and the barrier layer 3 is avoided, resulting in puncture or abrasion of the cushion layer 1 and the barrier layer 3, and further weakening the airtight function of the barrier structure.

[0027] Preferably, the layout density of the exhaust duct 4 is calculated according to formula (1): Formula (1) In the formula, L represents the layout density of the exhaust duct, specifically the effective length of the exhaust duct per unit area of the polluted site, with the unit of m / m 2 . L 0 represents the basic layout density of the exhaust duct, with the unit of m / m 2 , and the value ranges from 0.2 to 0.6. A represents the pollutant vapor concentration adjustment coefficient, with the value ranging from 1.1 to 1.5. The more types of pollutants, A the larger the value. represents the arithmetic mean of the soil pollutant concentrations at several soil investigation points in the polluted site, with the unit of mg / kg.C ST Indicates the concentration threshold of soil pollutants in the contaminated site, with the unit of mg / kg. Indicates the arithmetic mean of the groundwater pollutant concentrations at several groundwater investigation points in the contaminated site, with the unit of mg / L. C WT Indicates the concentration threshold of groundwater pollutants in the contaminated site, with the unit of mg / L.

[0028] In this embodiment, the layout density of the exhaust pipe 4 is optimized and adjusted according to the pollutant concentration in the contaminated site, which can effectively control the vapor concentration of the contaminated vapor in the in-situ soil pores, the adsorption layer 3 and the exhaust pipe 4, discharge the contaminated vapor in the source area of the site out of the barrier structure, thereby reducing the breakthrough time of the adsorption layer 3 in the source area and prolonging the overall service life of the barrier structure with airtightness.

[0029] Preferably, the spacing between soil investigation points is 10 - 40 m, and the spacing between groundwater investigation points is 20 - 80 m.

[0030] The embodiment of the present invention also provides a preparation method for a barrier structure for controlling underground contaminated vapor, including the following steps: Step 10, laying a cushion layer 1 above the foundation of the contaminated site.

[0031] Step 20, laying an adsorption layer 2 above the cushion layer 1. Meanwhile, an exhaust pipe 4 is laid in the adsorption layer 2.

[0032] Step 30, laying a barrier layer 3 above the adsorption layer 2.

[0033] Step 40, laying a concrete floor 5 above the barrier layer 3.

[0034] As a preferred example, the barrier layer 3 includes a first fiber layer 31, a polymer impermeable coating 32 and a second fiber layer 33 arranged in sequence from top to bottom. Among them, both the first fiber layer 31 and the second fiber layer 33 are made of geotextile. The polymer impermeable coating 32 is formed by coating emulsified asphalt, epoxy resin or high-density polyethylene.

[0035] In step 30, when laying the barrier layer 3, there are two schemes: The first one is to lay the second fiber layer 33 above the adsorption layer 2, coat the upper surface of the second fiber layer 33 to form the polymer impermeable coating 32, and lay the first fiber layer 31 on the upper surface of the polymer impermeable coating 32 to form the barrier layer.

[0036] Second, prepare prefabricated barrier blocks first. Specifically, a polymer anti-permeation coating block is formed by coating the upper surface of the second fiber block, and the first fiber block is laid on the upper surface of the polymer anti-permeation coating layer to form a prefabricated barrier block. The prefabricated barrier block is laid above the adsorption layer, and the prefabricated barrier blocks are spliced and laid to form a barrier layer. Compared with the first solution, the second solution has high construction efficiency. The hot melt welding process is used to process between two adjacent prefabricated barrier blocks to ensure that there are no gaps or defects between adjacent prefabricated barrier blocks, effectively blocking pollutant vapors.

[0037] The preparation method of the barrier structure for underground pollution vapor control provided by the above embodiments, the prepared barrier structure is horizontally arranged, including a cushion layer, an adsorption layer and a barrier layer arranged in sequence from bottom to top. The cushion layer is located at the bottom as a support to improve 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 rise through the cushion layer to the adsorption layer. Most of the pollutant vapors are adsorbed by the adsorption layer. Only a very small amount of pollutant vapors pass through the adsorption layer to reach the lower part of the barrier layer and are blocked by the barrier layer and cannot rise to the ground surface through the barrier layer. The horizontally arranged barrier structure prepared by the method of the embodiment of the present invention has good sealing performance and can effectively prevent harmful gases such as volatile organic compounds from escaping. It is easy to prepare, reducing construction complexity and time costs. For buildings built on polluted sites, the horizontally arranged barrier structure prepared by the method of this embodiment can significantly reduce the pollutant concentration in indoor air and improve the safety of the living and working environment. By eliminating or reducing the pollution impact, the land that was originally unusable can regain the value of development and utilization, promoting urban renewal and development, and at the same time providing more secure safeguard measures for the already repaired sites.

[0038] One specific example is provided below.

[0039] Example 1 Due to the leakage of a sewage treatment tank in a chemical industrial park, the surrounding plots were polluted, and the pollutants such as vinyl chloride in the soil and groundwater of the plots seriously exceeded the standard. In order to prevent these harmful volatile organic compounds from volatilizing to form soil vapor and migrating upward, affecting the surrounding environment and the health of residents, a pollutant vapor barrier structure project was implemented in the polluted plot area.

[0040] The pollution status was investigated in the polluted site. The spacing of soil investigation points was 40 m, and the spacing of groundwater investigation points was 80 m. According to the investigation of the soil and groundwater of the plot, the maximum concentrations of the soil and groundwater of the plot exceeded the vinyl chloride concentration threshold (the critical concentration unacceptable for human health), and the area of the exceeded standard range was about 600 m 2 , thereby determining the boundary of the horizontally arranged barrier structure.

[0041] The maximum vinyl chloride concentration in the soil is 25 times the vinyl chloride threshold of the soil, and the maximum vinyl chloride concentration in the groundwater is 237 times the vinyl chloride threshold of the soil. L 0 The value is 0.4 m / m 2 , A is 1.3. According to Equation (1), the layout density of the exhaust pipes is calculated to be 1.96 m / m 2 . Thus, according to the site area, the length of the exhaust pipes is calculated to be 600 × 1.96 = 1170 m. To ensure that the exhaust pipes can capture pollutant vapors to the greatest extent, the exhaust pipes are divided into two loop pipes and arranged at intervals from the inside to the outside centered on the pollution source, and the two loop pipes are connected by 8 branch pipes, as Figure 2 shown. The lengths of the two loop pipes are 450 m and 250 m respectively, and the total length of the 8 branch pipes is 470 m.

[0042] Considering the later planning, the plot will be built into a production plant in the future. According to the foundation planning of the plant, the depth of the foundation is 3 m. According to the scope of groundwater pollution, first, the soil within 3.35 m in the horizontal barrier range is excavated. After the excavation is completed, the bottom of the excavation pit is first constructed with a cushion layer. The thickness of cushion layer 1 is 30 cm, and a sand and gravel cushion layer is used. After the cushion layer is laid, an adsorption layer is laid, and at the same time, exhaust pipes are buried in the adsorption layer. The thickness of the adsorption layer is 5 cm, and the diameter of the exhaust pipes is 0.5 times the thickness of the adsorption layer, that is, 2.5 cm. After the adsorption layer is built, an emulsified asphalt layer is laid on its upper part. The thickness of the asphalt layer is 2 cm. After it is laid, it is rolled and formed with a light rolling equipment, and then the upper non-woven fabric is laid as a protective layer. The top layer is poured with cement concrete to form a concrete floor as the bottom of the upper building foundation.

[0043] The effect of the barrier structure is verified by gas detection. Specifically, after the excavation of the foundation pit is completed, the vinyl chloride content in the gas at the bottom of the foundation pit is monitored. After the vapor barrier structure is built, the vinyl chloride concentration is detected above the barrier structure and at the discharge port of the main pipe, once every 1 month. The gas detection concentrations are shown in the following table: Table 1 Vinyl chloride detection concentrations in gas at different positions (mg / L) Monitoring location / time (month) 0 1 2 Bottom of foundation pit (mg / L) 0.3 - - Above the barrier structure (mg / L) Not detected Not detected Not detected Main pipe discharge port (mg / L) 0.23 0.27 0.33 Judging from the on-site construction situation, after the excavation of the foundation pit is completed, there is an obvious pungent smell at the bottom of the foundation pit. After the vapor barrier structure is built, the smell is significantly eliminated. At the same time, according to the detection results, vinyl chloride is not detected above the vapor barrier structure, and the barrier effect is obvious.

[0044] From the verification data of the above construction parameters and barrier effects, it can be seen that the barrier structure effectively blocks the upward volatilization of volatile organic compounds (VOCs) in the contaminated site, significantly improving the surrounding environment and the health of residents. The monitoring data shows that the pollutant concentration at the main exhaust port has been continuously increasing significantly, which is conducive to organized emissions after treatment. The barrier structure has achieved the expected barrier effect and ensured environmental safety.

[0045] The above 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 by the above specific embodiments. The above specific embodiments and the descriptions in the specification are only for further explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, there will still be various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A barrier structure for underground contaminated vapor control, characterized in that: It comprises a cushion layer (1), an adsorption layer (2) and a barrier layer (3) which are arranged in sequence from bottom to top.

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 adsorption layer (2) has a thickness of 1 to 5 cm.

4. The barrier structure according to claim 1, characterized in that: The barrier layer (3) comprises a first fiber layer (31), a polymer anti-permeation coating (32), and a second fiber layer (33) which are arranged in sequence 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 geotextiles; the polymer anti-permeability coating (32) is formed by coating emulsified asphalt, epoxy resin or high-density polyethylene.

6. The barrier structure according to claim 1, characterized in that: An exhaust pipe (4) is provided in the adsorption layer (2); the exhaust pipe (4) comprises a plurality of annular pipes (401), the annular pipes (401) are arranged at intervals from the inside to the outside with the pollution source as the center, and two adjacent annular pipes (401) are connected via a plurality of branch pipes (402).

7. The barrier structure according to claim 6, characterized in that: The diameter of the exhaust pipe (4) is 0.3 to 0.5 times the thickness of the adsorption layer (2). The layout density of the exhaust pipe (4) is calculated according to formula (1): Formula (1) In the formula, L Indicates the layout density of the exhaust duct, in m / m 2 ; L 0 represents the basic density of exhaust pipe layout, the unit is m / m 2 , the value is 0.2~0.6; A It represents the pollutant vapor concentration adjustment coefficient, and its value ranges from 1.1 to 1.5; It represents the arithmetic mean of soil pollutant concentrations at several soil survey points in the contaminated site, in mg / kg; C ST It indicates the concentration threshold of soil pollutants in the contaminated site, in mg / kg; It represents the arithmetic mean of the groundwater pollutant concentrations at several groundwater survey points in the contaminated site, in mg / L; C WT It indicates the concentration threshold of groundwater pollutants in contaminated sites, in mg / L.

8. The barrier structure according to claim 7, characterized in that: The spacing between soil survey points is 10 to 40 m, and the spacing between groundwater survey points is 20 to 80 m.

9. A method for preparing a barrier structure for controlling underground contaminated vapor, characterized in that: The following steps are involved: Step 10, laying a cushion layer (1) on the foundation of the contaminated site; Step 20, laying an adsorption layer (2) on the cushion layer (1), and laying an exhaust pipe (4) in the adsorption layer (2); Step 30, laying a barrier layer (3) on the adsorption layer (2); Step 40: laying a concrete floor (5) above the barrier layer (3).

10. The preparation method according to claim 9, characterized in that: In the step 30, the prefabricated barrier blocks are spliced ​​and laid to form a barrier layer (3), and a hot-melt welding process is used between two adjacent prefabricated barrier blocks.

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