A method for constructing emergency isolation barriers for contaminated sites based on 3D printing

Abstract

The present invention provides a method for constructing an emergency barrier barrier for a contaminated site based on 3D printing, comprising the following steps: step 10, collecting pollution information of the contaminated site; step 20, determining a printing scheme for the barrier barrier according to the pollution information; step 30, using printing slurry as a raw material, and using 3D printing technology to print and generate a barrier barrier on the surface of the contaminated site according to the printing scheme. The present invention provides a method for constructing an emergency barrier barrier for a contaminated site based on 3D printing, which can quickly form a barrier barrier at a contaminated site to meet the emergency control needs of sudden environmental pollution.

Description

Technical Field

[0001] The present invention belongs to the technical field of contaminated site remediation, and specifically relates to a method for constructing an emergency isolation barrier for a contaminated site based on 3D printing. Background Art

[0002] The emergency response to sudden environmental pollution incidents is a difficult problem. Sudden environmental pollution incidents are characterized by uncertainty and concentrated emission of pollutants in a short period of time. If not controlled in time, they will have adverse effects on environmental media such as surface soil, groundwater, and atmosphere, as well as surrounding humans, vegetation, and organisms. Cutting off and controlling pollution sources and preventing the spread of pollution are effective methods for dealing with sudden soil pollution.

[0003] Pollution barriers can effectively control the migration of pollutants or block the exposure pathways of pollutants, and are the most commonly used and effective technology for risk control of polluted sites. At present, compacted clay and soil-geomembrane composite horizontal barriers are widely used in risk control projects. However, unlike the risk control of conventional polluted sites, the emergency control and post-disposal of sudden environmental pollution incidents require that the construction of the barrier be completed quickly and that the emergency disposal machinery and equipment have good traffic capacity after laying. Traditional compacted clay and soil-geomembrane composite horizontal barriers require compaction construction and long-term maintenance to control pollutants, which makes it difficult to meet the emergency disposal needs of sudden environmental pollution incidents. Therefore, it is urgent to develop a rapid construction method that meets the emergency control needs of sudden environmental pollution. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for constructing an emergency isolation barrier at a contaminated site based on 3D printing, which can quickly form an isolation barrier at a contaminated site to meet the needs of emergency control of sudden environmental pollution.

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

[0006] An embodiment of the present invention provides a method for constructing an emergency barrier for a contaminated site based on 3D printing, comprising the following steps:

[0007] Step 10, collecting pollution information of the polluted site;

[0008] Step 20, determining a printing scheme for the barrier according to the pollution information;

[0009] Step 30, using the printing slurry as a raw material and utilizing 3D printing technology to print a barrier on the surface of the contaminated site according to a printing plan.

[0010] As a further improvement of the embodiment of the present invention, the step 20 specifically includes:

[0011] Step 201, determining the contaminated boundary of the contaminated site according to the soil odor, the groundwater odor, the soil color and the groundwater color; and determining the printing boundary of the isolation barrier according to the contaminated boundary.

[0012] As a further improvement of the embodiment of the present invention, in step 201, the printing boundary extends 3 to 10 m outward from the contaminated boundary.

[0013] As a further improvement of the embodiment of the present invention, in step 201, the printed boundary of the isolation barrier located upstream in the groundwater flow direction of the contaminated site extends 3 to 5 meters outward from the contaminated boundary, and the printed boundary located downstream in the groundwater flow direction of the contaminated site extends 5 to 10 meters outward from the contaminated boundary.

[0014] As a further improvement of the embodiment of the present invention, the step 20 further includes:

[0015] Step 202: Divide the site within the printing boundary into a plurality of printing units, and determine the printing thickness of each printing unit according to the pollutant concentration of each printing unit.

[0016] As a further improvement of the embodiment of the present invention, the print thickness of each print unit is calculated using formula (1) according to the pollutant concentration of each print unit:

[0017] T i =0.2+S i ×0.1+W i ×0.1+Max[S i ,W i ]×0.1+A i ×0.1 Formula (1)

[0018] Where, T i Indicates the printing thickness of the i-th printing unit, in m; S i represents the binary value of soil pollution in the ith printing unit. If the concentration of the soil contaminant in the ith printing unit is less than the second-class land use screening value corresponding to the soil contaminant, then S i = 0; if the concentration of the soil contaminant of the i-th printing unit in the soil is greater than or equal to the second-class land use screening value corresponding to the soil contaminant, then S i =1; the soil pollutant is the pollutant with the largest ratio between the concentration of the pollutant in the soil and the corresponding Class II land use screening value of the pollutant among all pollutants;

[0019] W i represents the binary value of groundwater pollution of the ith printing unit. If the concentration of the groundwater pollutant marked in the ith printing unit in the groundwater is less than the Class IV groundwater limit corresponding to the marked groundwater pollutant, then W i=0; if the concentration of the groundwater pollutant marked in the i-th printing unit in the groundwater is greater than or equal to the Class IV groundwater limit corresponding to the groundwater pollutant marked, then W i =1; it indicates that the groundwater pollutant is the pollutant with the largest ratio between the concentration of the pollutant in groundwater and the Class IV groundwater limit corresponding to the pollutant among all pollutants;

[0020] A i represents the binary value of soil gas pollution of the ith print unit. If the concentration of the soil gas pollutant marked by the ith print unit in the soil gas is less than the concentration corresponding to the olfactory threshold of the soil gas pollutant marked by the ith print unit, then A i = 0; if the concentration of the soil gas pollutant marked by the i-th printing unit in the soil gas is greater than or equal to the concentration corresponding to the olfactory threshold of the soil gas pollutant, then A i =1; it indicates that the soil gas pollutant is the pollutant with the largest ratio between the concentration of the pollutant in the soil gas and the olfactory threshold corresponding to the pollutant among all pollutants.

[0021] As a further improvement to the embodiment of the present invention, each printing unit has a width of 1.0-2.0 m and a length of 10-20 m; each printing unit is printed in layers, and the printing thickness of each layer is 0.1-0.2 m.

[0022] As a further improvement of the embodiment of the present invention, the step 20 further includes:

[0023] Step 203, determining the printing direction according to the maximum ground slope of the contaminated site;

[0024] Specifically, if the maximum ground slope of the contaminated site is ≥10‰, it will be printed from low to high; if the maximum ground slope of the contaminated site is <10‰, it will be printed from the location of the pollution source to the printing boundary.

[0025] As a further improvement of the embodiment of the present invention, the present invention further includes:

[0026] In step 40, the surface of the barrier is covered with clay soil.

[0027] As a further improvement of the embodiment of the present invention, the thickness of the clay soil is 0.1-0.3 m, the compaction degree is 50%-75%, and the water content is 20%-40%.

[0028] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0029] (1) The present invention provides a method for constructing an emergency barrier for a contaminated site based on 3D printing. The method uses 3D printing technology and printing slurry as raw material to print a barrier on the surface of the contaminated site. The barrier can be quickly formed without the need for heavy equipment to press and construct, thus meeting the needs of emergency control of sudden environmental pollution.

[0030] (2) The method of the present invention performs printing in units, and determines the printing thickness of each unit according to the type and concentration of the site polluted medium of each printing unit. Under the premise of ensuring effective isolation of pollutants, it can reduce the use of slurry and shorten the printing construction time, thus providing more time for emergency disposal of environmental pollution incidents.

[0031] (3) The method of the present invention designs the thickness of the barrier by considering the olfactory threshold of the pollutant, thereby effectively avoiding the impact of pollutants with a low olfactory threshold on the sensory health of emergency response personnel and increasing the efficiency of emergency response.

[0032] (4) The method of the present invention optimizes the printing direction of the barrier according to the terrain slope of the contaminated site. If the terrain is relatively flat, the barrier is printed from the location of the pollution source to the pollution boundary, so that the barrier can be formed in time at the location of the pollution source to quickly block the pollutants; if the terrain slope is large, the barrier is printed from low to high. After the barrier formed by printing at low places is quickly formed, it can prevent the slurry from flowing to low places under the action of gravity when printing at high places, thereby reducing the deformation of the barrier, enhancing the bonding strength of the seams between adjacent printed strips, and ensuring the printing quality of the barrier. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A flow chart of a method for constructing a 3D printed emergency barrier for a contaminated site provided by an embodiment of the present invention;

[0034] Figure 2 It is a top view of the contaminated site in Example 1;

[0035] Figure 3 It is a side view of the first layer printing of the five printing units located at the AA' section in Example 1;

[0036] Figure 4 It is a side view of the five printing units located at the A-A' section in Example 1;

[0037] Figure 5 This is a side view of the five printing units located at the AA' section in Comparative Example 2 when they are completed.

[0038] The figure includes: pollution boundary 101, printing boundary 102 of the blocking barrier, groundwater flow direction 103, printing unit 201, first seam position 301, and second seam position 302. 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 constructing an emergency barrier for a contaminated site based on 3D printing, such as Figure 1 As shown, the following steps are included:

[0041] Step 10: Collect pollution information of the polluted site.

[0042] Specifically include: recording soil odor, groundwater odor, soil color and groundwater color. Sampling soil, groundwater and soil gas for testing to obtain the types and concentrations of soil pollutants, groundwater pollutants and soil gas pollutants. Consulting data to obtain the direction of groundwater flow at the contaminated site. Measure the maximum ground slope of the contaminated site.

[0043] Step 20, determining a printing plan for the barrier according to the pollution information.

[0044] Specifically include:

[0045] Step 201, determining the pollution boundary of the polluted site and the location of the pollution source according to the soil odor, groundwater odor, soil color and groundwater color.

[0046] According to the pollution boundary, the printing boundary of the barrier is determined. Preferably, the printing boundary extends 3 to 10 meters outward from the pollution boundary. The printing boundary of the barrier is outside the pollution boundary, so that the printing area is larger than the pollution area, and the barrier can completely cover the pollution area. Moreover, the distance between the printing boundary and the pollution boundary is 3 to 10 meters. Even if the pollutants migrate outward from the pollution boundary to a certain extent during the printing process, the barrier can also completely cover them, thereby effectively controlling the migration of pollutants.

[0047] It is further preferred that the printed boundary of the barrier located upstream of the groundwater flow direction of the contaminated site extends 3 to 5 meters outward from the contaminated boundary. Considering that under the action of groundwater flow, pollutants migrate downstream in the groundwater flow direction. In order to ensure that the barrier can fully block the pollutants, the printed boundary located downstream of the groundwater flow direction of the contaminated site extends 5 to 10 meters outward from the contaminated boundary.

[0048] Step 202: Divide the site within the printing boundary into a plurality of printing units, and determine the printing thickness of each printing unit according to the pollutant concentration of each printing unit.

[0049] Specifically, the printing thickness of each printing unit is calculated using formula (1):

[0050] Ti =0.2+S i ×0.1+W i ×0.1+Max[S i ,W i ]×0.1+A i ×0.1,i=1,2,…,n Formula (1)

[0051] Where, T i It indicates the printing thickness of the i-th printing unit, in m; n indicates the total number of printing units.

[0052] S i represents the binary value of soil pollution in the ith print unit. If the concentration of the marked soil pollutant in the ith print unit is less than the second-class land use screening value corresponding to the marked soil pollutant, then S i = 0. If the concentration of the marked soil pollutant in the i-th printing unit is greater than or equal to the second-class land use screening value corresponding to the marked soil pollutant, then S i = 1. Among all pollutants, the pollutant with the largest ratio between the concentration of the pollutant in the soil and the corresponding Class II land use screening value of the pollutant is used as the marker soil pollutant. The Class II land use screening value is determined with reference to the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard (Trial)" (GB 36600-2018).

[0053] W i Represents the binary value of groundwater pollution in the ith print unit. If the concentration of the groundwater pollutant in the ith print unit is less than the Class IV groundwater limit corresponding to the groundwater pollutant, then W i = 0. If the concentration of the groundwater pollutant marked in the i-th printing unit is greater than or equal to the Class IV groundwater limit corresponding to the groundwater pollutant marked, then W i = 1. Among all pollutants, the pollutant with the largest ratio between the concentration of the pollutant in groundwater and the corresponding Class IV groundwater limit value is used as the marker groundwater pollutant. The Class IV groundwater limit value is determined with reference to the Groundwater Quality Standard (GB / T14848-2017).

[0054] A i A represents the binary value of soil gas pollution of the ith print unit. If the concentration of soil gas pollutants marked in the ith print unit is less than the concentration corresponding to the olfactory threshold of soil gas pollutants marked, then A i = 0. If the concentration of the soil gas pollutant marked in the i-th printing unit is greater than or equal to the concentration corresponding to the olfactory threshold of the soil gas pollutant marked, then A i=1. Among all pollutants, the pollutant with the largest ratio between the concentration of the pollutant in the soil gas and the olfactory threshold corresponding to the pollutant is used as the marker soil gas pollutant. The olfactory threshold is determined with reference to the "Three-point comparison odor bag method for the determination of odor in ambient air and exhaust gas" (HJ 1262-2022). Under 20°C conditions, the concentration (C, in mg / L) corresponding to the olfactory threshold (A, dimensionless value) of the pollutant is calculated as follows: C = a×A×M (a represents the conversion coefficient, the value is 4.16×10 -5 mg L -1 ·mol -1 ; M represents the molecular mass of the pollutant, in g·mol -1 ).

[0055] For example, in an environmental emergency, only one pollutant is ethylbenzene, which is used as a soil pollutant, a groundwater pollutant, and a soil gas pollutant. The screening value of ethylbenzene for Class II land use is 28 mg / kg, the limit value of ethylbenzene for Class IV groundwater is 0.6 mg / L, and the concentration of ethylbenzene corresponding to the olfactory threshold is 7.94×10 -5 mg / L. The concentration of ethylbenzene in the soil of the sixth printing unit in the printing area is 55 mg / kg, the concentration of ethylbenzene in groundwater is 0.23 mg / L, and the concentration of ethylbenzene in soil gas is 0.0023 mg / L. Then in formula (1), S6=1, W6=0, A6=1, and the printing thickness of the sixth printing unit is T6=0.5m.

[0056] For example, in another environmental emergency, there were two pollutants, ethylbenzene and toluene. The corresponding Class II land use screening values ​​of the two pollutants were 28 mg / kg and 1200 mg / k, respectively, and the corresponding Class IV groundwater limits were 0.6 mg / L and 1.4 mg / L, respectively. The pollutant concentrations corresponding to the olfactory thresholds were 7.94×10 -5 mg / L, 3.74×10 -4mg / L. In the soil of the third printing unit in the printing area, the concentrations of ethylbenzene and soil toluene are 22mg / kg and 1350mg / kg respectively. The ratio of the toluene concentration to its corresponding Class II land use screening value (1350 / 1200=1.125) is greater than that of ethylbenzene (22 / 28=0.79), so toluene is used as a marker soil pollutant. The concentration value of toluene in soil is greater than its corresponding Class II land use screening value, so S3=1. In groundwater, the concentrations of ethylbenzene and toluene are 0.66mg / L and 1.21mg / L respectively. The ratio of the ethylbenzene concentration to its corresponding Class II land use screening value (0.66 / 0.6=1.1) is greater than that of toluene (1.21 / 1.4=0.86), so ethylbenzene is used as a marker groundwater pollutant. The concentration value of ethylbenzene in groundwater is greater than its corresponding Class II land use screening value, so W3=1. The concentrations of ethylbenzene and toluene in soil gas are 0.66 mg / L and 1.21 mg / L, respectively. The concentration of ethylbenzene in both is close to the corresponding olfactory threshold (1.55×10 -5 / 7.94×10 -5 =0.20) is higher than toluene (2.67×10 -4 / 3.74×10 -4 =0.71) is larger, so ethylbenzene is used as the marker soil gas pollutant. The concentration of ethylbenzene in soil gas is less than its corresponding second-class land use screening value, so A3 = 0. Using formula (1), the printing thickness of the third printing unit is obtained as T3 = 0.5m.

[0057] Preferably, each printing unit has a width of 1.0 to 2.0 m and a length of 10 to 20 m. Each printing unit is printed in layers, and the thickness of each layer is 0.1 to 0.2 m.

[0058] Step 203: Determine the printing direction according to the maximum ground slope of the contaminated site.

[0059] Specifically, if the maximum ground slope of the contaminated site is ≥10‰, printing is performed from low to high, that is, printing is performed at the lowest point of the contaminated site first, and then gradually printing upward.

[0060] If the maximum slope of the contaminated site is less than 10‰, print from the location of the pollution source to the printing boundary. That is, print at the location of the pollution source now, and then gradually print toward the printing boundary.

[0061] The printing boundary, the printing thickness of each printing unit and the printing direction are determined to form a printing plan.

[0062] Step 30, steel slag powder, carbide slag powder and red mud powder are fully mixed by dry method, water is added to prepare slurry as printing raw material, and according to the printing plan, 3D printing technology is used to print on the surface of the contaminated site to generate a barrier.

[0063] Step 40, covering the surface of the barrier with clay soil to prevent the barrier from cracking due to rapid water loss.

[0064] Preferably, in order to ensure that the barrier does not lose free water before hardening and forming, the thickness of the clay soil is 0.1-0.3 m, the compaction degree is 50%-75%, and the moisture content is 20%-40%.

[0065] One example and two comparative examples are provided below.

[0066] Example 1

[0067] A transport vehicle carrying ethylbenzene overturned, causing a sudden soil pollution incident. Through on-site exploration, the contaminated site boundary was determined based on the soil odor, groundwater odor, soil color, and groundwater color101. Figure 2 As shown, the printing boundary 102 of the isolation barrier is determined in combination with the pollution boundary 101 and the groundwater flow direction 103.

[0068] Along the groundwater flow direction (i.e. Figure 2 In the direction to the left of the center, the span of the pollutant is 40m. In the upstream direction of the groundwater flow, the printed boundary is determined as the pollution boundary extending 3.5m outward; in the downstream direction of the groundwater flow, the printed boundary is determined as the pollution boundary extending 6.5m outward; therefore, the span of the barrier in the direction of groundwater flow is 50m.

[0069] Perpendicular to the groundwater flow direction (i.e. Figure 2 The pollutant span is 28m, and extends 2.0m outward along the pollution boundary on both sides; therefore, the span of the barrier perpendicular to the groundwater flow direction is 32m.

[0070] The barrier is constructed in units, and each printing unit 201 is 2.0m wide and 10m long; each printing unit 201 is printed in layers, and the thickness of each layer is 0.1m. Therefore, the entire barrier is divided into 80 printing units. The height of the slurry outlet of the printing nozzle is 0.1m and the width is 0.2m, so the thickness of each printing strip is 0.1m and the width is 0.2m. Each printing unit requires 10 printing strips.

[0071] The following Figure 2 Taking the five printing units where the A-A' section is located as an example, the printing process is explained in detail.

[0072] Soil, groundwater and soil gas samples were collected at the center of each printing unit, and their concentrations were quickly tested on site. The results are shown in Table 1.

[0073] Table 1 Concentrations of ethylbenzene in soil, groundwater and soil gas corresponding to the five printed units

[0074]

[0075] We can get S in formula (1) i , W i , A i The values ​​are shown in Table 2.

[0076] Table 2 Parameter values ​​in formula (1) corresponding to the five printing units

[0077] Printing unit 1 2 3 4 5 <![CDATA[S i ]]> 0 0 0 1 1 <![CDATA[W i ]]> 0 0 1 1 0 <![CDATA[A i ]]> 0 0 1 1 0

[0078] The printing thickness of each printing unit is calculated using formula (1). Since the thickness of each printing tape in this example is 0.1 m, the number of printing layers of each printing unit can be calculated, see Table 3.

[0079] Table 3 Printing thickness and number of printing layers corresponding to the five printing units

[0080] Printing unit 1 2 3 4 5 Print thickness 0.2 0.2 0.4 0.5 0.3 Number of layers 2 2 4 5 3

[0081] The slope of the contaminated site is 13‰, so it is printed from low to high, that is, along the direction of a→b→c→d→e. Figure 3 As shown. Therefore, the first layer printing order is a→b→c→d→e, the second layer printing order is a→b→c→d→e, the third layer printing order is c→d→e, the fourth layer printing order is c→d, and the fifth layer printing order is d. So far, the printing process is complete. Figure 1 The printing of the five printing units where the A-A' section is located is as follows: Figure 4 shown.

[0082] Finally, the surface of the barrier is covered with clay soil with a thickness of 0.2 m, a compaction degree of 60%, and a moisture content of 30%.

[0083] The emergency personnel stood on the isolation barrier, and there was no obvious abnormality in the air above them, which did not cause olfactory discomfort to the emergency personnel.

[0084] Print the 5 printing units where the A-A' section is located, using a total of 64m of printing material 3 .

[0085] Samples were collected at the first joint position 301 of the two leftmost printing units to test the permeability coefficient of the barrier. The diameter of the sample collected was 20 cm, the height was 20 cm, and the center of the sample cross section was located at the joint position of the two printing units. The permeability coefficient test was carried out in accordance with the "Testing Procedures for Cement and Cement Concrete for Highway Engineering" (JTG 3420-2020). The permeability coefficient of the sample obtained by the test was 3.75×10 -7 cm / s.

[0086] Comparative Example 1

[0087] The traditional compaction method of clay is used, and heavy rolling machinery is used to compact the covering soil. Usually the thickness of the covering soil is 0.8 to 1.2 m. This comparative example takes the average value, that is, the thickness is 1.0 m. Figure 1 The soil volume corresponding to the five printing units where the A-A' section is located is 20×5×1.0=100m 3 The permeability coefficient of traditional compacted clay is 2.0~7.0×10 - 6 cm / s.

[0088] By comparing Example 1 with Comparative Example 1, it can be found that the method of the present invention can significantly reduce the volume of printed materials (36% less) and reduce the construction time of the barrier. Moreover, the permeability coefficient of the prepared barrier is significantly lower than that of traditional compacted clay (about 1 order of magnitude lower).

[0089] Comparative Example 2

[0090] The difference between this comparative example and Example 1 is that when calculating the thickness of the barrier, the olfactory threshold of the pollutant is not considered, that is, only the contaminated soil and contaminated groundwater are considered. The printing thickness of each printing unit is calculated using formula (2):

[0091] T i =0.2+S i ×0.1+W i ×0.1+Max[S i ,W i ]×0.1 Formula (2)

[0092] For the convenience of comparison, the barrier barriers of the five printing units where the A-A' section is located in Example 1 are removed, and the printing thickness of each printing unit is calculated again according to formula (2) for printing.

[0093] The results of the soil and groundwater samples tested at the center of the five printing units are shown in Table 4.

[0094] Table 4 Concentrations of ethylbenzene in soil and groundwater corresponding to 5 printing units

[0095]

[0096]

[0097] We can get S in formula (2) i , W i The values ​​are shown in Table 5.

[0098] Table 5 Parameter values ​​in formula (2) corresponding to 5 printing units

[0099] Printing unit 1 2 3 4 5 <![CDATA[S i ]]> 0 0 0 1 1 <![CDATA[W i ]]> 0 0 1 1 0

[0100] The printing thickness of each printing unit is calculated using formula (2). Since the thickness of each printing tape in this comparative example is 0.1 m, the number of printing layers of each printing unit is calculated, as shown in Table 6.

[0101] Table 6 Printing thickness and number of printing layers corresponding to 5 printing units

[0102] Printing unit 1 2 3 4 5 Print thickness 0.2 0.2 0.3 0.4 0.3 Number of layers 2 2 3 4 3

[0103] Print from low to high, that is, print along the direction of a→b→c→d→e. Therefore, the printing order of the first layer is a→b→c→d→e, the printing order of the second layer is a→b→c→d→e, the printing order of the third layer is c→d, and the printing order of the fourth layer is d. So far, the printing is complete. Figure 1 The printing of the five printing units where the A-A' section is located is as follows: Figure 5 shown.

[0104] Finally, the surface of the barrier is covered with clay soil with a thickness of 0.2 m, a compaction degree of 60%, and a moisture content of 30%.

[0105] The emergency personnel stood on the isolation barrier, and there was obvious smell in the air above. The emergency response personnel had obvious olfactory discomfort when they surveyed the scene.

[0106] By comparing Comparative Example 2 with Example 1, it can be found that the method of the present invention takes into account the olfactory threshold of the pollutant and optimizes the thickness of the barrier, which is superior.

[0107] Comparative Example 3

[0108] This comparative example Figure 2The five printing units where the B-B' section is located are printed. The ethylbenzene concentrations in the soil, groundwater and soil gas at the corresponding positions of the five printing units where the B-B' section is located are similar to those in the soil, groundwater and soil gas at the corresponding positions of the five printing units where the A-A' section is located. Therefore, the thickness of each printing unit calculated according to formula (1) is the same as that of the five printing units where the A-A' section is located, that is, from left to right, the number of printing layers is 2 layers, 2 layers, 4 layers, 5 layers and 3 layers respectively.

[0109] In the process of printing and constructing the cross-sectional barrier in Comparative Example 2, except for the printing direction of the barrier, the remaining steps are implemented in the same manner as in Example 1.

[0110] The barrier is printed from high to low, that is, along the direction of e→d→c→b→a. Therefore, the first layer printing order is e→d→c→b→a, the second layer printing order is e→d→c→b→a, the third layer printing order is e→d→c, the fourth layer printing order is d→c, and the fifth layer printing order is d. So far, the printing process is complete. Figure 1 Printing of the five printing units where the B-B' section is located.

[0111] Similarly, samples were collected at the second seam position 302 of the two leftmost printing units, and the permeability coefficient of the test barrier was 1.61×10 -6 cm / s.

[0112] By comparing Example 1 with Comparative Example 3, it can be found that for a contaminated site with a maximum ground slope of ≥10‰, the printing direction of Example 1 can change the bonding strength of two adjacent unit sections, thereby causing the permeability coefficient of the sample at the section to increase by about 4.3 times, which is beneficial to the isolation of pollutants.

[0113] The basic principles, main features and advantages of the present invention are shown and described above. 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 constructing an emergency barrier for a contaminated site based on 3D printing, characterized in that: The following steps are involved: Step 10, collecting pollution information of the polluted site; Step 20, determining a printing scheme for the barrier according to the pollution information; Step 30, using the printing slurry as a raw material and according to the printing plan, using 3D printing technology to print a barrier on the surface of the contaminated site; The step 20 specifically includes: Step 201, determining the contaminated boundary of the contaminated site according to the soil odor, groundwater odor, soil color and groundwater color; Determine the printing boundary of the isolation barrier according to the pollution boundary; Step 202, dividing the site within the printing boundary into a plurality of printing units, and determining the printing thickness of each printing unit according to the pollutant concentration of each printing unit; According to the pollutant concentration of each printing unit, the printing thickness of each printing unit is calculated using formula (1): Formula (1) In the formula, Indicates i The printing thickness of each printing unit, in m; Indicates i The soil pollution binary value of the printing unit, if the i If the concentration of the soil contaminant in the soil of the printed unit is less than the second-class land use screening value corresponding to the soil contaminant, then ; If i If the concentration of the soil contaminant in the soil of the printed unit is greater than or equal to the second-class land use screening value corresponding to the soil contaminant, then ; The soil pollutant marked is the pollutant with the largest ratio of the concentration of the pollutant in the soil to the corresponding Class II land use screening value of the pollutant among all pollutants; Indicates i The binary value of groundwater pollution in the printed unit. i If the concentration of the marked groundwater pollutant in the groundwater of the printed unit is less than the Class IV groundwater limit corresponding to the marked groundwater pollutant, then ; If i If the concentration of the marked groundwater pollutant in the groundwater of the printed unit is greater than or equal to the Class IV groundwater limit corresponding to the marked groundwater pollutant, then ; The groundwater pollutant marked is the pollutant with the largest ratio between the concentration of the pollutant in groundwater and the Class IV groundwater limit corresponding to the pollutant among all pollutants; Indicates i The soil air pollution binary value of each printing unit. i If the concentration of the soil gas pollutant marked by the printed unit in the soil gas is less than the concentration corresponding to the olfactory threshold of the soil gas pollutant marked by the printed unit, then ; If i If the concentration of the soil gas pollutant marked by the printed unit in the soil gas is greater than or equal to the concentration corresponding to the olfactory threshold of the soil gas pollutant marked by the printed unit, then ; The soil gas pollutant is the pollutant with the largest ratio between the concentration of the pollutant in the soil gas and the olfactory threshold corresponding to the pollutant among all pollutants.

2. The method for constructing an emergency barrier for a contaminated site based on 3D printing according to claim 1, characterized in that: In step 201, the printing boundary extends 3 to 10 m outward from the contaminated boundary.

3. The method for constructing an emergency barrier for a contaminated site based on 3D printing according to claim 2, characterized in that: In step 201, the printed boundary of the barrier located upstream of the groundwater flow direction of the contaminated site extends 3 to 5 m outward from the contaminated boundary, and the printed boundary located downstream of the groundwater flow direction of the contaminated site extends 5 to 10 m outward from the contaminated boundary.

4. The method for constructing an emergency barrier for a contaminated site based on 3D printing according to claim 1, characterized in that: The width of each printing unit is 1.0 to 2.0 m, and the length is 10 to 20 m; each printing unit is printed in layers, and the printing thickness of each layer is 0.1 to 0.2 m.

5. The method for constructing an emergency barrier for a contaminated site based on 3D printing according to claim 1, characterized in that: The step 20 further comprises: Step 203, determining the printing direction according to the maximum ground slope of the contaminated site; Specifically, if the maximum ground slope of the contaminated site is ≥10‰, it will be printed from low to high; if the maximum ground slope of the contaminated site is <10‰, it will be printed from the location of the pollution source to the printing boundary.

6. The method for constructing an emergency barrier for a contaminated site based on 3D printing according to claim 1, characterized in that: Also includes: In step 40, the surface of the barrier is covered with clay soil.

7. The method for constructing an emergency barrier for a contaminated site based on 3D printing according to claim 6, characterized in that: The thickness of clay soil is 0.1 to 0.3 m, the compaction degree is 50% to 75%, and the moisture content is 20% to 40%.

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