A simple method for confirming and treating low-permeability contaminated soil

Abstract

The application discloses a simple confirmation method for low-permeability contaminated soil, which comprises the following steps: inserting a first drain board into the contaminated soil as a water injection board, arranging a second drain board at a predetermined distance from the water injection board, draining water through a water-permeable section of the second drain board which is arranged on one side and faces the first drain board, injecting water into the water injection board, connecting the second drain board with a vacuum pump for water drainage, inserting the second drain board layer by layer and recording the water discharge amount after a predetermined time of water pumping layer by layer, obtaining the water discharge amount of each region of the contaminated soil within the same pumping time layer by layer and comparing the water discharge amount, and confirming the low-permeability region. When the conditions of some contaminated soil are relatively complex, the internal permeability difference is relatively large, and the soil remediation liquid such as an oxidant is injected through the injection method to carry out soil remediation, the permeation efficiency is different, and the treatment effect is poor. The application can identify and confirm the low-permeability region to take measures. The application further discloses a treatment method for locally low-permeability contaminated soil.

Description

TECHNICAL FIELD

[0001] The present application relates to a simple method for identifying low-permeability contaminated soil, and also relates to a treatment method for treating locally low-permeability contaminated soil. BACKGROUND

[0002] Regardless of whether leaching or injecting soil remediation liquid is used for harmless treatment by oxidation, in-situ treatment of soil relies on the penetration and diffusion of the treatment liquid and remediation liquid of the soil, and the penetration and diffusion is affected by the permeability coefficient of the soil. In order to improve the permeability, the prior art usually provides injection wells and extraction wells to improve the permeability. Patent document CN201810559905.0, a system for in-situ remediation of contaminated soil and application method, discloses a technology for further improving the permeability and in-situ treating low-permeability soil by using drainage plates and a vacuum pump. However, in practice, the internal composition and structure of the contaminated soil are relatively complex, resulting in uneven permeability of the soil in the contaminated area or the remediation area. Such permeability difference at least includes: 1. stratified structure of the soil, which usually includes topsoil layer, subsoil layer and bottom soil layer. The topsoil layer can be divided into upper topsoil layer and plough sole. The upper topsoil layer is generally porous, and the wet and dry conditions change frequently, the temperature changes greatly, and the permeability is good. However, the typical plough sole is very compact, has small porosity, and has few non-capillary pores (large pores) and many capillary pores (small pores). Therefore, the aeration is poor, the water permeability is poor, and the structure is often in sheet shape, and even has obvious horizontal bedding. 2. Due to soil compaction and other reasons, local permeability coefficient uneven soil is formed in the same stratified structure of the soil. Since the distribution of the internal permeability coefficient, especially the local uneven phenomenon in the same stratification, cannot be directly understood, engineers usually tend to use ordinary injection wells and extraction wells for treatment based on cost considerations. The soil remediation liquid such as oxidant may not be able to penetrate into this part of the contaminated soil, and the water sample extracted by the extraction well cannot reflect the true value of the pollutants in this part of the soil. The soil is mistakenly considered to have met the requirements without being fully treated, and under the action of other factors, the pollutants diffuse again, causing the treated soil to be contaminated again. SUMMARY

[0003] In view of the above problems, the present application aims to provide a simple method for identifying low-permeability contaminated soil, and also aims to provide a treatment method for low-permeability contaminated soil.

[0004] To this end, the present application provides a simple method for identifying low-permeability contaminated soil, which comprises inserting a first drain board into the contaminated soil as a water injection board, and arranging a second drain board at a predetermined distance from the water injection board, wherein the second drain board is arranged to draw water through a water-permeable section on one side and towards the first drain board, water is injected into the water injection board, the second drain board is connected to a vacuum pump for water drawing, the second drain board is inserted layer by layer and the water volume after a predetermined time of water drawing is recorded layer by layer, the water volume in each region of the contaminated soil is obtained and compared within the same water drawing time, and the low-permeability region is identified.

[0005] Further, the method comprises the following steps:

[0006] (1) inserting a water injection board at the boundary of the contaminated soil;

[0007] (2) inserting a second drain board downward at a predetermined distance from the water injection board to a predetermined length;

[0008] (3) injecting water into the water injection board, connecting the second drain board to the vacuum pump for water drawing, recording the corresponding water volume after a predetermined time of water drawing, stopping water injection, and continuing water drawing for a period of time and then stopping;

[0009] (4) continuing to insert the second drain board downward by the same length, and repeating step (3);

[0010] (5) repeating step (4) until the lower end of the second drain board exceeds the lower boundary of the contaminated soil and then stopping;

[0011] (6) pulling out the sleeve of the second drain board upward, using it as a water injection board, and repeating steps (2) to (5);

[0012] (7) comparing the water volume in each region within the same water drawing time, and identifying the low-permeability contaminated soil region.

[0013] Further, the second drain board comprises a water-impermeable sleeve, which has a shielding surface for covering the surface of the drain board, wherein the length of one shielding surface of the sleeve is less than the length of the drain board, so that the unshielded surface of the drain board forms a water-permeable section.

[0014] Further, the sleeve is sleeved on the second drain board in such a way that the sleeve is separated from the second drain board by external pulling.

[0015] Further, a sheath is arranged on the outside of the second drain board, and the sheath comprises an inner cavity and a moving plate, wherein the moving plate can move vertically relative to the second drain board arranged in the inner cavity to make the water-permeable section contact or separate from the soil.

[0016] Further, the sheath comprises a sheath body and a tapered head, the upper end of the sheath body is provided with a long hole for the moving plate to pass through, the upper surface of the tapered head is provided with a groove matched with the moving plate, the tapered head comprises a separable upper stopper and a lower tapered head, the upper stopper is provided with a through hole for the second drainage plate to pass through, the second drainage plate is fixed on the lower tapered head through the through hole, the upper stopper limits the lower tapered head to pass through the through hole, and the sheath is fixed with the sleeve body.

[0017] The application further discloses a treatment method of the local low-permeability contaminated soil confirmed by the method.

[0018] (a) confirming the boundary of the low-permeability area of the contaminated soil;

[0019] (b) retaining the inserted drainage plate of the contaminated soil, and any two adjacent drainage plates, wherein one is used for injecting soil remediation liquid, and the other is connected with a vacuum pump for pumping;

[0020] (c) inserting a pair of electrode drainage plates arranged at two ends or the middle of the boundary of the low-permeability area to replace the common drainage plates, wherein the drainage plate at one end is used for injecting soil remediation liquid and connected with a positive electrode, and the drainage plate at the other end is connected with a negative electrode and connected with a vacuum pump for pumping.

[0021] Further, the method for confirming the boundary of the low-permeability area of the contaminated soil in step (a) comprises the following steps: determining the initial boundary of the low-permeability area, when the recorded drainage amount first appears a low value, confirming the corresponding initial boundary by gradually approaching the corresponding water injection plate with the second drainage plate and recording the corresponding drainage amount.

[0022] Further, the method for confirming the boundary of the low-permeability area of the contaminated soil in step (a) comprises the following steps: determining the terminal boundary of the low-permeability area, when the recorded drainage amount appears a low value and then restores to normal, taking the water injection plate matched with the second drainage plate with the normal drainage amount as a current water injection plate, inserting the second drainage plate between the current water injection plate and the previous drainage plate, and confirming the corresponding terminal boundary by gradually moving the second drainage plate away from the water injection plate and recording the drainage amount.

[0023] The application has the following beneficial effects:

[0024] (1) The invention inserts two mutually cooperating drainage plates into the contaminated soil, wherein the first drainage plate serves as a water injection plate, and the second drainage plate is spaced apart from the water injection plate by a predetermined distance, the second drainage plate is provided with a water permeable section that is single-sidedly permeable to water and is arranged towards the first drainage plate, water is injected into the water injection plate, and the second drainage plate is connected to a vacuum pump for drainage. When there is a large volume of low-permeability soil between the water injection plate and the water permeable section of the second drainage plate, the amount of drainage through the second drainage plate is greatly reduced, so the location of the low-permeability soil can be determined accordingly. By inserting the drainage plates at equal distances and layer by layer, the location of the low-permeability soil in different layers can be found. By sequentially inserting the water injection plate and the second drainage plate in the contaminated soil area in order, the low-permeability soil in the entire area can be found, and targeted measures can be taken.

[0025] (2) In a specific embodiment of the invention, the second drainage plate includes a water-impermeable sleeve, the sleeve has a shielding surface for covering the surface of the drainage plate, wherein the length of one shielding surface of the sleeve is less than the length of the drainage plate so that the unshielded surface of the drainage plate forms a water permeable section, and the outer side of the second drainage plate is provided with a sheath, the sheath includes an inner cavity and a moving plate, the moving plate can move vertically relative to the second drainage plate arranged in the inner cavity so that the water permeable section is in contact with or separated from the soil. The sheath is used to protect the drainage plate when the drainage plate is inserted into the soil, and the moving plate is used to open the water permeable section for drainage.

[0026] (3) In a specific embodiment of the invention, the sheath includes a sheath body and a tapered head, the upper surface of the tapered head is provided with a groove matched with the moving plate, the tapered head is composed of a separable upper stopper and a lower tapered head, the upper stopper is provided with a through hole for the second drainage plate to pass through, the second drainage plate is fixed on the lower tapered head through the through hole, the upper stopper limits the lower tapered head from passing through the through hole, and the sheath is fixed with the sleeve. The drainage plate needs to be inserted layer by layer in multiple times, and a centrifugal pump needs to be connected for drainage during the process. The sheath allows the pile machine to be separated from the sheath and then reconnected for further pressing the sheath. The lower tapered head allows the sheath body to be pulled upwards after being inserted in place, and the wedge-shaped lower tapered head prevents the drainage plate from being displaced during the process of pulling out the sheath body. In addition, the sleeve is pulled out together with the sheath during the pulling-out process. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Schematic diagram of the principle of local permeability difference of the same layer of soil

[0028] Figure 2 Schematic diagram of the second drainage plate

[0029] Figure 3 Schematic diagram of the cross section of the sheath

[0030] Figure 4 Schematic diagram of the distribution of ordinary drainage plates and electrode drainage plates in contaminated soil

[0031] Figure 5 Fig. 2 is a schematic view of a cross section of a second drainage plate;

[0032] Figure 6 Fig. 3 is a schematic view of a difference in soil layer permeability.

[0033] Fig. 1 is a schematic view of a polluted soil area; Fig. 2 is a schematic view of a cross section of a first drainage plate; Fig. 3 is a schematic view of a cross section of a second drainage plate; Fig. 4 is a schematic view of a cross section of a third drainage plate; Fig. 5 is a schematic view of a pile machine; Fig. 6 is a schematic view of a drainage plate with electrodes. DETAILED DESCRIPTION

[0034] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined object, the specific embodiments, structures, features and effects according to the present application are described in detail below in combination with the drawings and preferred embodiments.

[0035] Referring to Fig. 1, a simple confirmation method of low-permeability polluted soil according to the present application includes the following steps: Figures 1 to 4 (1) A first drainage plate is inserted as a water injection plate 2 at the boundary of the polluted soil area 1; the determination of the boundary of the polluted soil area 1 belongs to the prior art and can be determined by taking soil or water samples in the area for examination;

[0036] (2) A second drainage plate 3 is inserted at a distance of 1.0-10.0 m from the water injection plate 2, and the length of the insertion is 30-60 cm, as shown in Fig. 2.

[0037] Figure 2 Figure 5 As shown in Fig. 3, the second drainage plate 3 includes a sleeve 301 made of impermeable material, the sleeve 301 is sleeved on the second drainage plate 3 and can be separated from the second drainage plate 3 under the action of external force, the sleeve 301 has a shielding surface 302 for covering the surface of the second drainage plate 3, wherein the length of one shielding surface 302 of the sleeve 301 is less than the length of the second drainage plate 3 so that the unshielded drainage plate surface forms a permeable section 303, the length of the permeable section 303 is 30-60 cm and faces the water injection plate 2, a sheath 4 is provided on the outside of the second drainage plate 3, the sleeve 301 is provided on the inside of the sheath 4, the sheath 4 includes an inner cavity 401 and a moving plate 402, the moving plate 402 can move vertically relative to the second drainage plate 3 provided in the inner cavity 401 so that the permeable section 303 is exposed or isolated.

[0038] ​​(3) water injection to the water injection plate 2, the second drainage plate 3 is connected to the vacuum pump for pumping, pumping for a certain period of time, record the corresponding pumping water, stop water injection, and continue pumping for a period of time to stop;

[0039] (4) continue to insert the second drainage plate 3 downward, the insertion length is the same as the previous insertion length, which is also 30-60cm, repeat step (3);

[0040] (5) repeat step (4) until the lower end of the second drainage plate 3 reaches the lower boundary of the contaminated soil, stop, and obtain the drainage data of different layers in the region. The upper and lower boundaries of the contaminated soil can be determined by pre-sampling detection.

[0041] (6) pull out the sleeve 301 of the second drainage plate 3, use it as the water injection plate 2, insert the second drainage plate 3 at a distance of 1.0-10.0m from the water injection plate 2, repeat steps (2) to (5), and obtain the drainage data of each layer in each region in turn;

[0042] (7) compare the pumping water in each region in the same pumping time, remove the values significantly lower or higher than the normal drainage, and calculate the average value. When a certain value is significantly lower than the average value, such as 1 / 2, it is identified as a low permeability area. After preliminary confirmation, other techniques can be used for determination and verification, such as sampling detection. Since the application has preliminarily determined the approximate area of the low permeability area 101, the workload of confirmation by sampling detection will be greatly reduced.

[0043] In the above embodiment, when the local soil permeability in the same layer is poor, refer to Figure 3As shown, the sheath 4 includes an upper platform 403, a sheath body 406 and a tapered head 405, the pile grab of the pile driver 5 can be pressed into by embracing the outer wall of the sheath 4, in this embodiment, the upper platform 403 of the sheath 4 is connected with the pressing cylinder of the pile driver 5 to press the sheath 4 into the soil, the upper end of the sheath body 406 is provided with a long hole for the moving plate 402 to pass through, the upper end of the moving plate 402 can be connected with a hydraulic or pneumatic device to control its movement, the upper surface of the tapered head 405 and the side wall of the sheath 4 are provided with a groove 404 matched with the moving plate 402, the tapered head 405 includes a combined upper stop block 4051 and a lower tapered head 4052, the longitudinal section of the lower tapered head 4052 is a quadrilateral symmetrical along the vertical center line, the upper stop block 4051 is provided with a through hole 4053 for the second drainage plate 3 to pass through, the second drainage plate 3 is fixed on the lower tapered head 4052 through the through hole 4053, the upper stop block 4051 limits the lower tapered head 4052 to pass through the through hole 4053, and the sheath 4 is fixed with the sleeve body 301. The working process of this embodiment is as follows: the sheath 4 is connected with the pile driver 5, the second drainage plate 3 is fixed with the lower tapered head 4052 through the through hole 4053, the pile driver 5 presses the sheath 4 into the soil body, and the sheath 4 protects the sleeve body 301 and the second drainage plate 3 during the pressing process; after reaching the target position, the moving plate 402 is pulled up to open the water permeable section 303 for pumping and draining; after the pumping and draining is completed, the moving plate 402 is reset, the moving plate 402 can include a protruding section, a soil discharge hole 4054 can be arranged below the groove 404, and the soil in the groove 404 can be discharged by the protruding section during the resetting process of the moving plate, so that the soil adhered to the water permeable section 303 is avoided, and the pile driver 5 continues to press the sheath 4 into the soil body, the above process is repeated multiple times to reach the lower boundary of the contaminated soil for pumping and draining, after the pumping and draining is completed, the pile driver 5 pulls the sheath 4 upward, the sheath 4 drives the upper stop block 4051 and the sleeve body 301 to move upward, since the second drainage plate 3 is fixed with the lower tapered head 4052, the lower tapered head 4052 is affected by the friction force of the soil body, so that the second drainage plate 3 does not move, the sleeve body 301 is separated from the second drainage plate 3, the second drainage plate 3 restores the permeability and can be used as a water injection plate, after the soil treatment is completed, the second drainage plate 3 can be pulled out, the lower tapered head 4052 is actually two tapered heads facing in opposite directions, which facilitates the discharge of the soil above and the pulling out of the lower tapered head 4052. It should be noted that the above drainage plate can also be replaced by a PVC pipe with holes on the surface, and a geomembrane is laid on the outside of the PVC pipe as a filtration membrane.

[0044] If the permeability difference is caused by stratification, and has similar drainage capacity at the same depth, corresponding measures can be taken in different layers. When there is a local permeability difference in the same soil layer, a method for treating a local low-permeability contaminated soil according to the present application includes the following steps:

[0045] (1) Confirm the boundary of the low permeability area of the contaminated soil. When the recorded drainage amount appears a low value, the second drainage plate 3 is gradually approached to the corresponding water injection plate 2, water is injected to the water injection plate 2, the second drainage plate 3 is connected to the vacuum pump for drainage, and the drainage amount corresponding to the same drainage time is recorded to confirm the corresponding initial boundary. That is, when the drainage amount returns to the normal value during the process of gradually approaching the second drainage plate 3 to the corresponding water injection plate 2, it can be simply determined that the position of the second drainage plate 3 is the initial boundary of the low permeability area 101. When the recorded drainage amount appears a low value, the drainage amount of the subsequent second drainage plate 3 returns to normal again, the water injection plate matched with the second drainage plate with the normal drainage amount is used as the current water injection plate, the second drainage plate 3 is inserted between the current water injection plate 2 and the previous drainage plate, water is injected to the current water injection plate 2, the second drainage plate 3 is connected to the vacuum pump for drainage, and the drainage amount is recorded. By gradually moving the second drainage plate 3 away from the current water injection plate 2, when the drainage amount of the second drainage plate 3 appears a low value, it can be simply considered that the previous position of the second drainage plate 3 is the terminal boundary of the low permeability area 101. In this embodiment, gradually approaching and gradually moving away means that the drainage plates are inserted in the area for multiple times, and the distance between the positions of the subsequent order and the positions of the previous order is in an arithmetic progression.

[0046] (2) As shown in FIG. 2, the drainage plates inserted in the contaminated soil area 1 are reserved, and any two adjacent drainage plates are used for injecting soil remediation liquid and connecting the vacuum pump for drainage. Figure 4

[0047] (3) A pair of electrode drainage plates 6 are inserted at both ends and / or the middle of the boundary of the low permeability area 101 to replace the ordinary drainage plates, one of which is used for injecting soil remediation liquid and connecting a positive electrode, and the other of which is connected to a negative electrode and the vacuum pump for drainage.

[0048] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, as long as the changes or modifications do not deviate from the technical solution of the present application. Any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present application are still within the scope of the technical solution of the present application.​

Claims

1. A simple method for confirming low permeability of contaminated soil, characterized by: The first drain board is inserted into the contaminated soil as a water injection board, and the second drain board is arranged at a predetermined distance from the water injection board, the second drain board drains water through the water permeable section arranged on one side and facing the first drain board, water is injected into the water injection board, the second drain board is connected to the vacuum pump for drainage, the second drain board is inserted layer by layer and the drainage amount after a predetermined time of pumping is recorded layer by layer, the drainage amount of each region of the contaminated soil within the same pumping time is obtained and compared, and the low permeability region is confirmed. The method comprises the following steps: S1: inserting a water injection board at the boundary of the contaminated soil; S2: inserting a second drain board downward at a predetermined distance from the water injection board to a predetermined length; S3: injecting water into the water injection board, connecting the second drain board to the vacuum pump for pumping, recording the corresponding pumping amount after a predetermined pumping time, stopping water injection, and continuing pumping for a period of time and then stopping; S4: continuing to insert the second drain board downward by the same length, and repeating step (3); S5: repeating step (4) until the lower end of the second drain board exceeds the lower boundary of the contaminated soil and then stopping; S6: pulling out the sleeve of the second drain board upward, using it as a water injection board, and repeating steps (2) to (5); S7: comparing the pumping amount of each region within the same pumping time to confirm the low permeability region of the contaminated soil. The second drain board comprises a water-impermeable sleeve, the sleeve has a shielding surface for covering the surface of the drain board, and the length of one shielding surface of the sleeve is less than the length of the drain board, so that the unshielded surface of the drain board forms a water permeable section.

2. The method according to claim 1, characterized in that: The sleeve is sleeved on the second drain board in such a way that the sleeve is separated from the second drain board by pulling out.

3. The method according to claim 2, wherein the method is characterized by: The outer side of the second drain board is provided with a sheath, and the sheath comprises an inner cavity and a moving plate, the moving plate can move vertically relative to the second drain board arranged in the inner cavity to make the water permeable section contact or separate from the soil.

4. The method according to claim 3, wherein the method is characterized by: The sheath comprises a sheath body and a tapered head, the upper end of the sheath body is provided with a long hole for the moving plate to pass through, the upper surface of the tapered head is provided with a groove matched with the moving plate, the tapered head comprises a separable upper stopper and a lower tapered head, the upper stopper is provided with a through hole for the second drain board to pass through, the second drain board is fixed on the lower tapered head through the through hole, the upper stopper limits the lower tapered head to pass through the through hole, and the sheath is fixed with the sleeve.

5. A method for treating a locally low-permeable contaminated soil, comprising identifying a low-permeable zone in the contaminated soil using the simple method for identifying a low-permeable contaminated soil according to claim 4, characterized in that: The method comprises the following steps: (a) confirming the boundary of the low permeability region of the contaminated soil; (b) retaining the inserted drain board of the contaminated soil, and any two adjacent drain boards, one of which is used to inject soil remediation liquid, and the other is connected to the vacuum pump for pumping; (c) inserting the drain board with electrodes at both ends of the low permeability region instead of the ordinary drain board, and the drain board at one end is used to inject soil remediation liquid and connected to the positive electrode, and the drain board at the other end is connected to the negative electrode and connected to the vacuum pump for pumping.

6. A method of treating a locally low permeable contaminated soil according to claim 5, characterized in that: The method of step (a) for confirming the boundary of the low permeability region of the contaminated soil comprises: determining the initial boundary of the low permeability region, when the recorded drainage amount first appears a low value, the corresponding initial boundary is confirmed by gradually approaching the corresponding water injection board with the second drain board and recording the corresponding drainage amount.

7. A method of treating a locally low permeability contaminated soil according to claim 5, characterized in that: The step (a) of confirming the boundary of the low permeability zone of the contaminated soil includes: determination of the terminal boundary of the low permeability zone, when the recorded drainage volume appears a low value and the drainage volume is recovered again, a water injection plate matched with a second drainage plate of the recovered drainage volume is used as a current water injection plate, the second drainage plate is inserted between the current water injection plate and the previous drainage plate, and the corresponding terminal boundary is confirmed by gradually moving the second drainage plate away from the current water injection plate and recording the drainage volume.

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