A saline-alkali soil remediation system capable of reducing alkali and salt and a laying method thereof

Abstract

The application discloses a saline-alkali soil remediation system capable of reducing alkali and salt discharge and a laying method thereof, and relates to the technical field of saline-alkali soil remediation. The saline-alkali soil remediation system comprises a leaching device, a salt-preventing and separating structure, a negative pressure air extraction device and a salt discharge device. The salt-preventing and separating structure comprises a salt-preventing and separating layer which is embedded in a soil main body to separate the soil main body into a surface layer and a bottom layer arranged in the up-down direction. The negative pressure air extraction device is at least partially embedded in the surface layer. The salt discharge device comprises at least one salt discharge pipeline which is embedded in the surface layer and is in communication with the negative pressure air extraction device. The outer surface of the salt discharge pipeline is provided with a water absorption side which is formed by a part of the outer surface of the salt discharge pipeline facing the leaching device. A plurality of water absorption holes are arranged on the water absorption side, and each water absorption hole is provided with non-woven fabric for allowing leaching liquid to enter. The system can effectively remediate saline-alkali soil and stabilize the salt content of the saline-alkali soil at a treatment requirement level.

Description

Technical Field

[0001] This invention relates to the field of saline-alkali soil remediation technology, and in particular to a saline-alkali land remediation system for reducing alkali and removing salt, and its laying method. Background Technology

[0002] Saline-alkali land is a general term for various saline and alkaline soils, as well as soils with different degrees of salinization and alkalization. Its characteristics are high soil salt content and high groundwater salt content. As water evaporates, salt accumulates in the soil, which leads to a decrease in soil structure and soil compaction.

[0003] Current strategies for saline-alkali soil remediation include five aspects: equipment, development of efficient soil conditioners, improvement of soil desalination technology, plant planting, and fertilizers. However, their effects are not significant and the remediation efficiency is low. Summary of the Invention

[0004] The main objective of this invention is to propose a saline-alkali land remediation system that reduces alkali and salt content, aiming to solve the problem of low remediation efficiency of saline-alkali soil in existing technologies.

[0005] To achieve the above objectives, this invention proposes a saline-alkali land remediation system for reducing alkali and removing salt, used to remediate the main body of the soil, comprising:

[0006] A rinsing device is used to spray liquid onto the exterior of the soil mass so that the liquid penetrates downward from the surface of the soil mass.

[0007] A salt-proof structure includes a salt-proof layer, which is embedded in the soil body to divide the soil body into a surface layer and an inner layer arranged in the vertical direction.

[0008] A negative pressure extraction device, said negative pressure extraction device being at least partially extended into said surface layer; and...

[0009] A salt removal device includes at least one salt removal pipe, which is embedded in the surface layer and connected to the negative pressure air extraction device. The outer surface of the salt removal pipe facing the rinsing device forms a water absorption side, and a plurality of water absorption holes are provided on the water absorption side. Each water absorption hole is provided with non-woven fabric for allowing rinsing liquid to enter.

[0010] In one embodiment, the rinsing device includes a plurality of rinsing pipes arranged at intervals in a horizontal direction, and the portion of the outer surface of each rinsing pipe facing the brine discharge pipe forms a water outlet side, and a plurality of rinsing holes are provided on the water outlet side.

[0011] In one embodiment, the interval between any two adjacent rinse pipes is 0.5–1.5 m; and / or,

[0012] The inner diameter of each of the rinse tubes is 8–12 mm; and / or,

[0013] The interval between any two adjacent rinse holes is 0.3–0.7 m; and / or,

[0014] The inner diameter of each of the rinse holes is 2 to 5 mm.

[0015] In one embodiment, the salt discharge device includes a plurality of salt discharge pipes, which are arranged at intervals in a horizontal direction, with a spacing of 4 to 6 meters between each adjacent salt discharge pipe; and / or,

[0016] The distance between the salt drainage pipe and the upper surface of the main soil mass is 45-55 cm; and / or,

[0017] The salt drainage pipe is installed at an incline, with a burial slope of 0.8% to 1.2%; and / or,

[0018] The inner diameter of the salt discharge pipe is 100–160 mm; and / or,

[0019] The opening ratio of the salt discharge pipe is 2% to 4%; and / or,

[0020] The inner diameter of each of the aforementioned water-absorbing holes is 4–8 mm; and / or,

[0021] The interval between two adjacent water absorption holes is 1 to 3 cm.

[0022] In one embodiment, the saline-alkali land remediation system for reducing alkali and removing salt further includes a filter layer disposed on the outer surface of the water-absorbing side of the salt removal pipe, the filter layer being used to prevent soil particles from entering the salt removal pipe.

[0023] In one embodiment, the filter media of the filter layer comprises a mixture of sand, gravel, and pebbles, wherein the sand has a particle size of 0.5–2 mm, the gravel has a particle size of 2–4 mm, and the pebbles have a particle size of 4–8 mm; and / or,

[0024] The thickness of the filter layer is 80-100 mm.

[0025] In one embodiment, the negative pressure suction device includes a suction pump and a plurality of suction pipes arranged at intervals in the horizontal direction.

[0026] Each of the aforementioned air extraction pipes extends vertically, with one end connected to the air extraction pump and the other end connected to the salt discharge pipe. At least one air extraction hole is provided on the lower outer surface of each of the aforementioned air extraction pipes, and a filter screen is provided in the air extraction hole to enable the air extraction pipe to draw in gas from the soil while preventing soil particles from clogging the air extraction hole.

[0027] In one embodiment, the inner diameter of each of the suction pipes is 60–80 mm; and / or,

[0028] The interval between two adjacent extraction pipes is 4–6 m; and / or,

[0029] The interval between two adjacent air extraction holes is 8-10 cm; and / or,

[0030] The inner diameter of each of the aforementioned air extraction holes is 4–8 mm.

[0031] In one embodiment, the distance between the impermeable and salt-barrier layer and the upper surface of the main soil mass is 45–55 cm; and / or,

[0032] The thickness of the impermeable and salt-barrier layer is 10–20 cm; and / or,

[0033] The impermeable and salt-barrier layer is composed of saline-alkali soil, solidifying agent, alkali activator, sugarcane pith, and water.

[0034] The present invention also provides a method for laying a saline-alkali land remediation system for reducing alkali and desalination. Based on the aforementioned saline-alkali land remediation system for reducing alkali and desalination, the saline-alkali land remediation system for reducing alkali and desalination further includes a filter layer disposed on the outer surface of the water absorption side of the desalination pipe. The filter layer is used to prevent soil particles from entering the desalination pipe.

[0035] The method for laying the saline-alkali land restoration system for reducing alkali and desalination includes the following steps:

[0036] S10. Remove part of the surface layer of saline-alkali soil in the main soil mass to form a depression on the surface of the main soil mass.

[0037] S20. Lay the anti-seepage and salt-barrier layer at the bottom of the concave part, and backfill on top of the anti-seepage and salt-barrier layer to obtain the first soil layer structure;

[0038] S30. Lay a salt drainage pipe above the first soil layer structure, and perform a second backfill on the side of the salt drainage pipe on the water absorption side to cover it, so that the water absorption side of the salt drainage pipe is exposed.

[0039] S40. Lay a filter layer on the water-absorbing side of the salt discharge pipe and backfill on top of the filter layer so that the concave part is filled to obtain a second soil layer structure.

[0040] S50. Lay a rinsing device on the surface of the second soil layer structure.

[0041] The technical solution of this invention employs a leaching device to spray liquid into the soil matrix, allowing the liquid to permeate downwards from the surface of the soil matrix. Since the soil matrix is ​​characterized by saline-alkali soil, the permeating leaching liquid contains salts from the soil matrix. A pre-embedded anti-seepage and salt-barrier structure within the soil matrix divides it into a surface layer and an inner layer arranged vertically. This anti-seepage and salt-barrier layer severs the connection between the lower (inner) and upper (surface) layers of water, inhibiting the entry of salts from the lower layer into the upper layer, thereby effectively suppressing the increase of salt content in the upper surface soil. A salt drainage pipe is pre-embedded in the soil surface layer. Multiple suction holes on the absorbent side of the drainage system can collect leachate containing salt from the topsoil, which is then discharged through the desalination pipe. Furthermore, non-woven fabric placed inside each suction hole effectively prevents soil particles from entering or clogging the suction port. By connecting the desalination pipe to a negative pressure extraction device, the device draws air from the pipe and even from the soil near the suction holes, creating a pressure difference between the inside of the pipe and the surrounding soil. This allows the salt-containing leachate from the outer soil to enter the desalination pipe through the suction holes, improving the efficiency of salt removal from the topsoil. This remediation system, through the combined use of a leaching device, a desalination device, and a negative pressure extraction device, quickly and efficiently removes salt from the topsoil, purifying it. Furthermore, by placing a seepage-proof salt-barrier layer at the bottom of the topsoil layer, it inhibits the upward evaporation of salt from the inner soil layers with moisture. Therefore, this invention ensures that the salt content in the soil reaches a stable value required for saline-alkali land management (i.e., soil salt content <0.2%) by accelerating the discharge of surface salt and inhibiting the evaporation of inner salt. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0043] Figure 1 A schematic diagram of an embodiment of the saline-alkali land remediation system for reducing alkali and removing salt provided by the present invention;

[0044] Figure 2 For the present invention Figure 1 A magnified view of part A in the image.

[0045] Explanation of icon numbers:

[0046] 100. Saline-alkali land remediation system for reducing alkali and removing salt; 1. Leaching device; 11. Leaching pipe; 2. Anti-seepage and salt-barrier structure; 21. Anti-seepage and salt-barrier layer; 3. Negative pressure air extraction device; 31. Air extraction pipe; 311. Air extraction hole; 312. Filter screen; 4. Salt removal device; 41. Salt removal pipe; 411. Water absorption hole; 5. Filter layer; a. Surface layer; b. Inner layer.

[0047] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] Saline-alkali land is a general term for various saline and alkaline soils, as well as soils with different degrees of salinization and alkalization. Its characteristics are high soil salt content and high groundwater salt content. As water evaporates, salt accumulates in the soil, which leads to a decrease in soil structure and soil compaction.

[0050] Current strategies for saline-alkali soil remediation include five aspects: equipment, development of efficient soil conditioners, improvement of soil desalination technology, plant planting, and fertilizers. However, their effects are not significant and the remediation efficiency is low.

[0051] In view of this, such as Figure 1 As shown, this invention provides a saline-alkali land remediation system 100 for reducing alkali and desalination, used to remediate the main body of the soil, including:

[0052] The rinsing device 1 is used to spray liquid onto the outside of the soil body so that the liquid penetrates downward from the surface of the soil body;

[0053] The seepage-proof and salt-barrier structure 2 includes a seepage-proof and salt-barrier layer 21, which is embedded in the soil body to divide the soil body into a surface layer a and an inner layer b arranged in the vertical direction.

[0054] A negative pressure extraction device 3, which is at least partially embedded in the surface layer a; and a salt removal device 4, which includes at least one salt removal pipe 41, which is pre-embedded in the surface layer a and communicates with the negative pressure extraction device 3. The outer surface of the salt removal pipe 41 facing the rinsing device 1 forms a water-absorbing side, and a plurality of water-absorbing holes 411 are provided on the water-absorbing side. Each water-absorbing hole 411 is provided with non-woven fabric for allowing rinsing liquid to enter.

[0055] In the technical solution of this invention, a leaching device 1 is used to spray liquid into the soil body, so that the liquid penetrates downward from the surface of the soil body. The soil body is soil that meets the characteristics of saline-alkali land, so the leaching liquid that penetrates down contains salt from the soil body. A seepage-proof and salt-barrier structure 2 is pre-embedded in the soil body to divide the soil body into a surface layer a and an inner layer b arranged in the vertical direction. The seepage-proof and salt-barrier layer 21 can cut off the connection between the water in the lower part (i.e., the inner layer b of the soil body) and the upper part (i.e., the surface layer a of the soil body), inhibiting the salt in the water in the lower part from entering the upper part, thereby effectively inhibiting the increase of salt in the upper surface layer a soil. A salt drainage pipe 41 is pre-embedded in the soil surface layer a, and the salt drainage pipe 41 has a water absorption side. Multiple suction holes 411 are provided to collect the leachate containing salt from the top layer a soil, and the leachate is discharged through the salt drainage pipe 41. In addition, by placing non-woven fabric in each suction hole 411, soil particles can be effectively prevented from entering or clogging the suction port. By connecting the salt drainage pipe 41 to the negative pressure suction device 3, when the negative pressure suction device 3 is running, it will draw out the air in the salt drainage pipe 41 and even the air in the soil near the suction holes 411 through the suction holes 411 of the salt drainage pipe 41, so that a pressure difference is formed between the inside of the salt drainage pipe 41 and the soil outside it. This allows the leachate containing salt in the soil outside to enter the salt drainage pipe through the suction holes 411, thereby improving the salt removal efficiency in the top layer a soil. The aforementioned remediation system, through the combined arrangement of a rinsing device 1, a salt removal device 4, and a negative pressure extraction device 3, rapidly and efficiently removes salt from the top layer (a) of soil, thus purifying the top layer (a). Furthermore, by placing an impermeable salt-barrier layer 21 at the bottom of the top layer (a), it inhibits the upward evaporation of salt from the inner layer (b) with water. Therefore, this invention, through accelerating the removal of salt from the top layer (a) and inhibiting the evaporation of salt from the inner layer (b), ensures that the salt content in the soil reaches a stable value required for saline-alkali land remediation (i.e., soil salinity <0.2%). After being remediated by the remediation system of this invention, the top layer (a) of the main soil body can be used for planting.

[0056] It should be noted that, as Figure 1 As shown, the length of the salt discharge pipe 41 extends horizontally, with an opening at both its left and right ends. One of the openings is blocked, and the other is connected to the waste liquid pool.

[0057] In one embodiment, the rinsing device 1 includes a plurality of rinsing pipes 11 arranged at intervals along a horizontal direction. The outer surface of each rinsing pipe 11 facing the brine discharge pipe 41 forms a water outlet side, and a plurality of rinsing holes are provided on the water outlet side. For example... Figure 1 As shown, the rinsing device 1 can be installed on the surface of the soil body (i.e., the upper surface of surface layer a), or it can be installed at a certain distance above the surface of the soil body, as long as it achieves the purpose of spraying the soil body. The lower surface of each rinsing pipe 11 is the water outlet side, and multiple rinsing holes on the water outlet side are used to spray rinsing liquid into the soil body. The rinsing liquid can dissolve the salt in the soil body. Therefore, as the rinsing liquid flows downward into the desalination pipe 41 under the action of gravity, it will carry away the salt in the soil body, thereby reducing the salt content in the soil body. The rinsing pipe 11 can be installed one-to-one with the desalination pipe 41 (e.g., Figure 1 As shown in the diagram, the arrangement does not necessarily need to be one-to-one, as long as the rinsing solution can smoothly enter the desalination pipe 41. Preferably, each rinsing pipe 11 is provided with a desalination pipe 41 directly below it, i.e., one-to-one correspondence.

[0058] In one embodiment, the interval between any two adjacent rinsing pipes 11 is 0.5 to 1.5 m. This interval of 0.5 to 1.5 m ensures that while saving on the cost of the rinsing pipes 11, a good spraying effect is achieved, increasing the area of ​​the soil surface wetted by the rinsing liquid.

[0059] In one embodiment, the inner diameter of each of the rinsing pipes 11 is 8 to 12 mm. An inner diameter of 8 to 12 mm ensures higher internal pressure, resulting in a larger coverage area of ​​the soil surface after the rinsing liquid is sprayed out, thus increasing the spraying area.

[0060] In one embodiment, the interval between any two adjacent leaching holes is 0.3 to 0.7 m. This interval ensures that the leaching solution can effectively contact the soil matrix and dissolve and remove salts from the soil.

[0061] In one embodiment, the inner diameter of each of the rinse holes is 2 to 5 mm. An inner diameter of 2 to 5 mm ensures smooth liquid flow, preventing clogging due to small holes and excessive flow rate or volume due to large holes, thus effectively controlling the distribution and spraying of the rinse fluid.

[0062] In one embodiment, the desalination device 4 includes a plurality of desalination pipes 41, which are arranged horizontally at intervals, with a spacing of 4 to 6 meters between each adjacent pair of desalination pipes 41. This 4-6 meter interval between adjacent pairs of desalination pipes 41 ensures that they do not interfere with each other and maintains the stability of the remediation system. Furthermore, it ensures that the leachate containing the main salts of the soil is evenly discharged from the soil into the desalination pipes 41, avoiding localized accumulation.

[0063] In one embodiment, the distance between the salt drainage pipe 41 and the upper surface of the soil body is 45-55 cm. This distance avoids damage to the soil structure, ensures the pipe is not easily damaged by mechanical tillage, and facilitates regular maintenance by personnel.

[0064] In one embodiment, the brine drainage pipe 41 is installed at an incline with a burial slope of 0.8% to 1.2%. The incline of the brine drainage pipe 41 facilitates the rapid outflow of the brine-containing leachate to the outlet. The burial slope of the brine drainage pipe 41 within the range of 0.8% to 1.2% ensures that the leachate flows naturally out along the interior of the pipe, reducing the accumulation of leachate within the pipe. The slope also helps to remove solid salts and impurities from the pipe, maintaining its unobstructed flow.

[0065] In one embodiment, the inner diameter of the salt drainage pipe 41 is 100-160 mm. An inner diameter of 100-160 mm allows the salt drainage pipe 41 to withstand greater external loads without easily being damaged, while also reducing the likelihood of salt, soil, and other solid particles depositing inside the pipe, thus lowering the risk of pipe blockage.

[0066] In one embodiment, the opening ratio of the brine drainage pipe 41 is 2% to 4%. An opening ratio of 2% to 4% ensures smooth brine drainage while avoiding an excessively large opening ratio, which could degrade the mechanical properties of the brine drainage pipe 41 and reduce its load-bearing capacity. The total area of ​​the openings (i.e., the holes for water flow) on the brine drainage pipe 41 is the proportion of the total surface area of ​​the brine drainage pipe 41.

[0067] In one embodiment, the inner diameter of each water absorption hole 411 is 4 to 8 mm. An inner diameter of 4 to 8 mm for each water absorption hole 411 can ensure sufficient absorption of water from the soil body; if the opening is too small, the water absorption rate is slow and the salt discharge rate is slow; if the opening is too large, the mechanical properties of the salt discharge pipe 41 deteriorate, and there is a risk of collapse.

[0068] In one embodiment, the interval between two adjacent water absorption holes 411 is 1 to 3 cm. This interval of 1 to 3 cm ensures proper absorption of moisture from the soil matrix without compromising the mechanical properties of the desalination pipe 41.

[0069] In one embodiment, the saline-alkali land remediation system 100 for reducing alkali and removing salt further includes a filter layer disposed on the outer surface of the salt removal pipe 41 on the water absorption side. The filter layer is used to prevent soil particles from entering the salt removal pipe 41. By setting the filter layer, large particles in the soil mass can be prevented from entering the salt removal pipe 41, thereby avoiding soil loss. At the same time, it can prevent the salt removal pipe 41 from becoming clogged, thus affecting the salt removal efficiency of the salt removal pipe 41.

[0070] In one embodiment, the filter media of the filter layer comprises a mixture of sand, gravel, and pebbles, wherein the sand has a particle size of 0.5–2 mm, the gravel has a particle size of 2–4 mm, and the pebbles have a particle size of 4–8 mm. By adjusting the particle sizes of the sand, gravel, and pebbles, the pore size of the filter layer can be reduced to block large solid particles in the soil mass while allowing water to pass through the filter layer quickly.

[0071] In one embodiment, the thickness of the filter layer is 80-100 mm. A filter layer thickness of 80-100 mm allows water to pass through quickly while still blocking soil, preventing water accumulation in the filter layer due to excessive thickness, which would reduce water absorption efficiency.

[0072] In one embodiment, the negative pressure extraction device 3 includes an extraction pump and a plurality of extraction pipes 31 arranged at intervals in the horizontal direction. Each extraction pipe 31 extends vertically, with one end connected to the extraction pump and the other end connected to the salt drainage pipe 41. At least one extraction hole 311 is provided on the lower outer surface of each extraction pipe 31, and a filter screen 312 is provided in the extraction hole 311 to allow the extraction pipe 31 to draw in gas from the soil while preventing soil particles from clogging the extraction hole 311. When the extraction pump starts running, the gas in the exhaust pipe and the gas in the soil body outside the extraction hole 311 are extracted through the extraction pipe 31, resulting in a lower pressure inside the salt drainage pipe 41 and the extraction pipe 31. At this time, the soil body is connected to the external environment with a higher pressure, creating a pressure difference between the two. This causes the air and leachate in the soil body to quickly enter the negative pressure space formed by the salt drainage pipe 41 and the extraction pipe 31, promoting the discharge of the salt-containing leachate and improving the salt removal efficiency.

[0073] In one embodiment, the inner diameter of each of the air extraction pipes 31 is 60-80 mm. The inner diameter of each air extraction pipe 31 is in the range of 60-80 mm, which can ensure that the air in the soil mass near the salt drainage pipe 41, air extraction pipe 31 and air extraction hole 311 is quickly extracted, and a negative pressure space is quickly formed in the pipe; at the same time, it prevents large solid particles in the soil mass from entering the air extraction pipe 31.

[0074] In one embodiment, the interval between two adjacent air extraction pipes 31 is 4 to 6 meters. This interval of 4 to 6 meters ensures that air in the soil near the air extraction hole 311 can be quickly drawn into the air extraction pipe 31, ensuring high extraction efficiency while saving costs.

[0075] In one embodiment, the interval between two adjacent air extraction holes 311 is 8 to 10 cm. This interval of 8 to 10 cm ensures that air in the soil mass near the air extraction hole 311 can be extracted evenly and efficiently, and prevents solid matter in the soil from entering the pipe.

[0076] In one embodiment, the inner diameter of each of the air extraction holes 311 is 4 to 8 mm. An inner diameter of 4 to 8 mm for each air extraction hole 311 ensures that air in the soil mass near the air extraction hole 311 can be efficiently extracted, and prevents large solid particles in the soil from entering the pipe and affecting the extraction efficiency.

[0077] In one embodiment, the distance between the seepage-proof and salt-barrier layer 21 and the upper surface of the soil body is 45-55 cm. This distance effectively prevents salt in the inner layer b from rising to the soil surface a via capillary action, and provides ample and suitable planting space (i.e., the surface layer a of the soil body).

[0078] In one embodiment, the thickness of the seepage-proof and salt-barrier layer 21 is 10–20 cm. A thickness of 10–20 cm effectively severs the connection between the inner layer b and the surface layer a, preventing the salt content of the surface layer a from rising again, thus inhibiting soil salinization in the surface layer a. Furthermore, by limiting the thickness of the seepage-proof and salt-barrier layer 21, it can better adapt to surface and underground movement and deformation, possessing a certain degree of plasticity while maintaining its integrity and seepage-proof effect; simultaneously, it gives the seepage-proof and salt-barrier layer 21 a certain degree of elasticity, which can absorb and alleviate surface and underground stress and deformation, reducing the risk of leakage. Leakage refers to the phenomenon of liquid or gas flowing from one area into another without permission through defects, gaps, or other weak points in materials, structures, or devices.

[0079] In one embodiment, the seepage-proof and salt-barrier layer 21 is composed of saline-alkali soil, a solidifying agent, an alkali activator, sugarcane pith, and water. The seepage-proof and salt-barrier layer 21 has a low permeability coefficient, meaning it has good impermeability and can prevent salt-containing vapors from evaporating upwards.

[0080] The present invention also provides a method for laying a saline-alkali land remediation system 100 for reducing alkali and desalination. Based on the aforementioned saline-alkali land remediation system 100 for reducing alkali and desalination, the saline-alkali land remediation system 100 for reducing alkali and desalination further includes a filter layer disposed on the outer surface of the water absorption side of the desalination pipe 41. The filter layer is used to prevent soil particles from entering the desalination pipe 41.

[0081] The method for laying the saline-alkali land remediation system 100 for reducing alkali and removing salt includes the following steps:

[0082] S10. Remove part of the saline-alkali soil in the top layer a of the main soil mass to form a depression in the top layer a of the main soil mass.

[0083] S20. Lay the anti-seepage and salt-barrier layer 21 at the bottom of the concave part, and backfill on top of the anti-seepage and salt-barrier layer 21 to obtain the first soil layer structure.

[0084] S30. A salt drainage pipe 41 is laid above the first soil layer structure. A second backfill is carried out on the side of the salt drainage pipe 41 on the water absorption side to cover it, and the water absorption side of the salt drainage pipe 41 is exposed.

[0085] S40. Lay a filter layer on the water absorption side of the salt discharge pipe 41, and backfill on top of the filter layer so that the concave part is filled to obtain a second soil layer structure.

[0086] S50. Lay a rinsing device 1 on the surface of the second soil layer structure.

[0087] In the above-mentioned laying method, backfilling is performed after laying the impermeable and salt-barrier layer 21, after laying the salt drainage pipe 41, and after laying the filter layer. Through three backfillings, the supporting structure between the impermeable and salt-barrier layer 21, the salt drainage pipe 41, and the filter layer is strengthened, the mechanical properties of the saline-alkali land remediation system 100 for reducing alkali and draining salt are improved, and each structure can perform its function and cooperate with each other to filter and absorb water in the soil into the drainage pipe. By laying the rinsing device 1 on the surface of the second soil layer structure, the salt in the second soil layer structure is dissolved and absorbed into the drainage pipe with water, thereby reducing the salt content in the soil.

[0088] It should be noted that, specifically in step S30, a salt drainage pipe 41 is laid above the first soil layer structure, and the air extraction pipe 31 is connected to the water absorption side of the salt drainage pipe 41, so that the other side of the air extraction pipe 31 is outside the soil body and connected to an air pump. That is, the water absorption side of the salt drainage pipe 41 not only has a water absorption hole 411, but also a connection hole with the same diameter as the air extraction pipe 31 for the air extraction pipe 31 to connect with the salt drainage pipe 41. The salt drainage pipe 41 and the air extraction pipe 31 can also be integrally formed.

[0089] In one embodiment of the present invention, the method for preparing the impermeable and salt-barrier layer 21 material includes the following steps:

[0090] After drying the slag, fly ash and desulfurized gypsum to constant weight, they were sieved.

[0091] Dry slag, fly ash and desulfurized gypsum are mixed and ball-milled to obtain a mixed powder.

[0092] The lumpy saline-alkali soil is mixed to become granular saline-alkali soil.

[0093] The mixed powder is added to the granular saline-alkali soil to obtain a premix;

[0094] An alkali activator, sugarcane fiber, and water are added to the premix to obtain a mixture.

[0095] The mixture is spread out and repeatedly rolled into blocks and then dried and cured to obtain the anti-seepage and salt barrier layer 21 material.

[0096] In one embodiment of the present invention, the step of mixing desulfurized gypsum, slag, and fly ash to obtain a mixed powder includes:

[0097] Desulfurized gypsum, slag and fly ash are dried to constant weight at 100-110℃ and then sieved. The desulfurized gypsum, slag and fly ash are then mixed in a certain proportion and stirred at medium speed of 100-400r / min for 5-10min to obtain mixed powder.

[0098] In one embodiment of the present invention, the step of ball milling the mixed powder includes:

[0099] The mixed powder is placed in a ball mill and ball-milled for 60-90 minutes to obtain the ball-milled mixed powder.

[0100] In one embodiment of the present invention, the step of stirring saline-alkali soil containing lumps into granular saline-alkali soil includes:

[0101] The lumpy saline-alkali soil is stirred and mixed at a medium speed of 100-400 r / min for 5-10 min to form granular saline-alkali soil.

[0102] In one embodiment of the present invention, the step of adding the mixed powder to the saline-alkali soil and stirring to obtain a premix includes:

[0103] Add the mixed powder to the saline-alkali soil and mix at high speed at 600-1000 r / min for 15-20 min.

[0104] In one embodiment of the present invention, the content of the curing agent is 20-25% of the total mass of the saline-alkali soil, the content of water is 15-20% of the total mass of the saline-alkali soil, the content of sugarcane pith is 1-2% of the total mass of the saline-alkali soil, and the activator is Ca(OH)2, accounting for 0.5% of the total mass of the curing agent.

[0105] In one embodiment of the present invention, the step of adding Ca(OH)2 to the premix and mixing it with water and sugarcane pith to obtain a mixture includes:

[0106] Prepare a saturated solution of Ca(OH)2 using distilled water, then mix it evenly with sugarcane pith and add it to the premix. Stir at high speed at 600-1000 r / min for 15-20 min to obtain the mixture.

[0107] In one embodiment of the present invention, the step of spreading the mixture and repeatedly rolling it into blocks and then drying and curing it to obtain the impermeable and salt-barrier layer 21 material is as follows:

[0108] The mixture, after being crushed, forms blocks with a thickness of not less than 10 cm.

[0109] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0110] Example 1

[0111] This embodiment proposes a comprehensive improvement system for saline-alkali land, the preparation method of which includes the following steps:

[0112] Step 1: Use an excavator to remove the saline-alkali soil to be improved, forming a depression, with a digging depth of 65-70cm;

[0113] Step 2: Laying the anti-seepage and salt-barrier layer 21. This includes the following steps:

[0114] After drying the slag, fly ash and desulfurized gypsum to constant weight, they were sieved.

[0115] Dry slag, fly ash and desulfurized gypsum are mixed and ball-milled to obtain a mixed powder.

[0116] The lumpy saline-alkali soil is mixed to become granular saline-alkali soil.

[0117] The mixed powder is added to the granular saline-alkali soil to obtain a premix;

[0118] An alkali activator, sugarcane fiber, and water are added to the premix to obtain a mixture.

[0119] The mixture is spread out and repeatedly rolled into blocks and then dried and cured to obtain the anti-seepage and salt barrier layer 21 material.

[0120] Slag, fly ash, and desulfurized gypsum are mixed to obtain a mixed powder, wherein slag accounts for 60% of the total dry mass, fly ash accounts for 25%, and desulfurized gypsum accounts for 15%. The specific steps are as follows: slag, desulfurized gypsum, and fly ash are dried separately at 100–110℃ to constant weight and then sieved. Then, the desulfurized gypsum and fly ash are mixed at a medium speed of 100–400 r / min for 5–10 min to obtain the mixed powder.

[0121] The mixed powder was placed in a ball mill and ball-milled for 60 minutes to obtain the ball-milled mixed powder.

[0122] The first step involves mixing the lumpy saline-alkali soil excavated in the first step into granular saline-alkali soil. The specific steps are as follows: the soil containing lumps is mixed at a medium speed of 100-400 r / min for 5-10 minutes to form granular saline-alkali soil.

[0123] A premixed material is obtained by adding a mixed powder consisting of slag, fly ash and desulfurized gypsum to the granular saline-alkali soil and stirring it. The specific steps are as follows: the mixed powder is added to the saline-alkali soil and stirred at high speed at 600-1000 r / min for 15-20 min.

[0124] The step of adding Ca(OH)2 to the premix and mixing it with water and sugarcane pith to obtain a mixture is as follows: the content of the curing agent is 20-25% of the total mass of the saline-alkali soil, the content of water is 15-20% of the total mass of the saline-alkali soil, the content of sugarcane pith is 1-2% of the total mass of the saline-alkali soil, and the activator is Ca(OH)2, accounting for 0.5% of the total mass of the curing agent. Specifically, the steps are: preparing a saturated solution of Ca(OH)2 using distilled water, then mixing it evenly with sugarcane pith and adding it to the premix; stirring at high speed at 600-1000 r / min for 15-20 min to obtain the mixture.

[0125] The mixture is spread out and repeatedly rolled into blocks and then dried and cured to obtain the seepage-proof and salt-barrier layer 21 material.

[0126] Step 3: Lay the salt drainage pipe 41 above the impermeable salt barrier layer 21. First, backfill with saline-alkali soil above the salt barrier layer, with a backfill thickness of about 30-40cm. Then, place a layer of sand and gravel filter material with different particle sizes, about 30-50mm thick, at the location where the salt drainage pipe 41 will be laid. Lay the salt drainage pipe 41 on top of the filter material. The salt drainage pipe 41 is a PE corrugated pipe with a diameter of 100-160mm. The spacing between each pipe is 5m, the burial slope is 1%, and a layer of non-woven fabric is wrapped around the outside of the salt drainage pipe 41.

[0127] Step 4: Connect the vacuum extraction pipe 31 to the pre-drilled hole at the top of the salt drainage pipe. After connecting, use a salt-alkali resistant adhesive to bond the salt drainage pipe to the extraction pipe 31, and wrap it tightly with non-woven fabric. The salt-alkali resistant adhesive used is WELD-ON 717 transparent adhesive from IPS in the United States.

[0128] Step 5: Continue the second backfilling of saline-alkali soil on both sides of the drainage pipe, and lay a filter layer consisting of 2-4 layers of sand, gravel and pebbles on the upper part of the pipe. The filter layer is laid in an inverted cone shape.

[0129] Step 6: Perform the third backfilling of saline-alkali soil on top of the sand filter layer;

[0130] Step 7: Lay a drip irrigation pipe every 1m on the soil surface. The drip irrigation pipe is a PE flexible hose with a diameter of 10mm, and holes are made at the bottom of the pipe every 0.5m.

[0131] Example 2

[0132] This embodiment proposes a comprehensive improvement system for saline-alkali land, the preparation method of which includes the following steps:

[0133] Step 1: Use an excavator to remove the saline-alkali soil to be improved, forming a depression, with a digging depth of 65-70cm;

[0134] Step 2: Laying the anti-seepage and salt-barrier layer 21. This includes the following steps:

[0135] After drying the slag, fly ash and desulfurized gypsum to constant weight, they were sieved.

[0136] Dry slag, fly ash and desulfurized gypsum are mixed and ball-milled to obtain a mixed powder.

[0137] The lumpy saline-alkali soil is mixed to become granular saline-alkali soil.

[0138] The mixed powder is added to the granular saline-alkali soil to obtain a premix;

[0139] An alkali activator, sugarcane fiber, and water are added to the premix to obtain a mixture.

[0140] The mixture is spread out and repeatedly rolled into blocks and then dried and cured to obtain the anti-seepage and salt barrier layer 21 material.

[0141] Slag, fly ash, and desulfurized gypsum are mixed to obtain a mixed powder, wherein slag accounts for 55% of the total dry mass, fly ash accounts for 25%, and desulfurized gypsum accounts for 20%. The specific steps are as follows: slag, desulfurized gypsum, and fly ash are dried separately at 100–110℃ to constant weight and then sieved. Then, the desulfurized gypsum and fly ash are mixed at a medium speed of 100–400 r / min for 5–10 min to obtain the mixed powder.

[0142] The mixed powder was placed in a ball mill and ball-milled for 75 minutes to obtain the ball-milled mixed powder.

[0143] The first step involves mixing the lumpy saline-alkali soil excavated in the first step into granular saline-alkali soil. The specific steps are as follows: the soil containing lumps is mixed at a medium speed of 100-400 r / min for 5-10 minutes to form granular saline-alkali soil.

[0144] A premixed material is obtained by adding a mixed powder consisting of slag, fly ash and desulfurized gypsum to the granular saline-alkali soil and stirring it. The specific steps are as follows: the mixed powder is added to the saline-alkali soil and stirred at high speed at 600-1000 r / min for 15-20 min.

[0145] The step of adding Ca(OH)2 to the premix and mixing it with water and sugarcane pith to obtain a mixture is as follows: the content of the curing agent is 20-25% of the total mass of the saline-alkali soil, the content of water is 15-20% of the total mass of the saline-alkali soil, the content of sugarcane pith is 1-2% of the total mass of the saline-alkali soil, and the activator is Ca(OH)2, accounting for 0.5% of the total mass of the curing agent. Specifically, the steps are: preparing a saturated solution of Ca(OH)2 using distilled water, then mixing it evenly with sugarcane pith and adding it to the premix; stirring at high speed at 600-1000 r / min for 15-20 min to obtain the mixture.

[0146] The mixture is spread out and repeatedly rolled into blocks and then dried and cured to obtain the seepage-proof and salt-barrier layer 21 material.

[0147] Step 3: Lay the salt drainage pipe 41 above the impermeable salt barrier layer 21. First, backfill with saline-alkali soil above the salt barrier layer, with a backfill thickness of about 30-40cm. Then, place a layer of sand and gravel filter material with different particle sizes, about 30-50mm thick, at the location where the salt drainage pipe 41 will be laid. Lay the salt drainage pipe 41 on top of the filter material. The salt drainage pipe 41 is a PE corrugated pipe with a diameter of 100-160mm. The spacing between each pipe is 5m, the burial slope is 1%, and a layer of non-woven fabric is wrapped around the outside of the salt drainage pipe 41.

[0148] Step 4: Connect the vacuum extraction pipe 31 to the pre-drilled hole at the top of the salt drainage pipe. After connecting, use a salt-alkali resistant adhesive to bond the salt drainage pipe to the extraction pipe 31, and wrap it tightly with non-woven fabric. The salt-alkali resistant adhesive used is WELD-ON 717 transparent adhesive from IPS in the United States.

[0149] Step 5: Continue the second backfilling of saline-alkali soil on both sides of the drainage pipe, and lay a filter layer consisting of 2-4 layers of sand, gravel and pebbles on the upper part of the pipe. The filter layer is laid in an inverted cone shape.

[0150] Step 6: Perform the third backfilling of saline-alkali soil on top of the sand filter layer;

[0151] Step 7: Lay a drip irrigation pipe every 1m on the soil surface. The drip irrigation pipe is a PE flexible hose with a diameter of 10mm, and holes are made at the bottom of the pipe every 0.5m.

[0152] Example 3

[0153] This embodiment proposes a comprehensive improvement system for saline-alkali land, the preparation method of which includes the following steps:

[0154] Step 1: Use an excavator to remove the saline-alkali soil to be improved, forming a depression, with a digging depth of 65-70cm;

[0155] Step 2: Laying the anti-seepage and salt-barrier layer 21. This includes the following steps:

[0156] After drying the slag, fly ash and desulfurized gypsum to constant weight, they were sieved.

[0157] Dry slag, fly ash and desulfurized gypsum are mixed and ball-milled to obtain a mixed powder.

[0158] The lumpy saline-alkali soil is mixed to become granular saline-alkali soil.

[0159] The mixed powder is added to the granular saline-alkali soil to obtain a premix;

[0160] An alkali activator, sugarcane fiber, and water are added to the premix to obtain a mixture.

[0161] The mixture is spread out and repeatedly rolled into blocks and then dried and cured to obtain the anti-seepage and salt barrier layer 21 material.

[0162] Slag, fly ash, and desulfurized gypsum are mixed to obtain a mixed powder, wherein slag accounts for 50% of the total dry mass, fly ash accounts for 30%, and desulfurized gypsum accounts for 20%. The specific steps are as follows: slag, desulfurized gypsum, and fly ash are dried separately at 100–110℃ to constant weight and then sieved. Then, the desulfurized gypsum and fly ash are mixed at a medium speed of 100–400 r / min for 5–10 min to obtain the mixed powder.

[0163] The mixed powder was placed in a ball mill and ball-milled for 90 minutes to obtain the ball-milled mixed powder.

[0164] The first step involves mixing the lumpy saline-alkali soil excavated in the first step into granular saline-alkali soil. The specific steps are as follows: the soil containing lumps is mixed at a medium speed of 100-400 r / min for 5-10 minutes to form granular saline-alkali soil.

[0165] A premixed material is obtained by adding a mixed powder consisting of slag, fly ash and desulfurized gypsum to the granular saline-alkali soil and stirring it. The specific steps are as follows: the mixed powder is added to the saline-alkali soil and stirred at high speed at 600-1000 r / min for 15-20 min.

[0166] The step of adding Ca(OH)2 to the premix and mixing it with water and sugarcane pith to obtain a mixture is as follows: the content of the curing agent is 20-25% of the total mass of the saline-alkali soil, the content of water is 15-20% of the total mass of the saline-alkali soil, the content of sugarcane pith is 1-2% of the total mass of the saline-alkali soil, and the activator is Ca(OH)2, accounting for 0.5% of the total mass of the curing agent. Specifically, the steps are: preparing a saturated solution of Ca(OH)2 using distilled water, then mixing it evenly with sugarcane pith and adding it to the premix; stirring at high speed at 600-1000 r / min for 15-20 min to obtain the mixture.

[0167] The mixture is spread out and repeatedly rolled into blocks and then dried and cured to obtain the seepage-proof and salt-barrier layer 21 material.

[0168] Step 3: Lay the salt drainage pipe 41 above the impermeable salt barrier layer 21. First, backfill with saline-alkali soil above the salt barrier layer, with a backfill thickness of about 30-40cm. Then, place a layer of sand and gravel filter material with different particle sizes, about 30-50mm thick, at the location where the salt drainage pipe 41 will be laid. Lay the salt drainage pipe 41 on top of the filter material. The salt drainage pipe 41 is a PE corrugated pipe with a diameter of 100-160mm. The spacing between each pipe is 5m, the burial slope is 1%, and a layer of non-woven fabric is wrapped around the outside of the salt drainage pipe 41.

[0169] Step 4: Connect the vacuum extraction pipe 31 to the pre-drilled hole at the top of the salt drainage pipe. After connecting, use a salt-alkali resistant adhesive to bond the salt drainage pipe to the extraction pipe 31, and wrap it tightly with non-woven fabric. The salt-alkali resistant adhesive used is WELD-ON 717 transparent adhesive from IPS in the United States.

[0170] Step 5: Continue the second backfilling of saline-alkali soil on both sides of the drainage pipe, and lay a filter layer consisting of 2-4 layers of sand, gravel and pebbles on the upper part of the pipe. The filter layer is laid in an inverted cone shape.

[0171] Step 6: Perform the third backfilling of saline-alkali soil on top of the sand filter layer;

[0172] Step 7: Lay a drip irrigation pipe every 1m on the soil surface. The drip irrigation pipe is a PE flexible hose with a diameter of 10mm, and holes are made at the bottom of the pipe every 0.5m.

[0173] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A saline-alkali land remediation system for reducing alkali and removing salt, used to remediate the main body of the soil, characterized in that, include: A rinsing device is used to spray liquid onto the exterior of the soil mass so that the liquid penetrates downward from the surface of the soil mass. A salt-proof structure includes a salt-proof layer, which is embedded in the soil body to divide the soil body into a surface layer and an inner layer arranged in the vertical direction. A negative pressure extraction device, said negative pressure extraction device being at least partially extended into said surface layer; and... A salt removal device includes at least one salt removal pipe, which is embedded in the surface layer and connected to the negative pressure air extraction device. The outer surface of the salt removal pipe facing the rinsing device forms a water absorption side, and a plurality of water absorption holes are provided on the water absorption side. Each water absorption hole is provided with non-woven fabric for allowing rinsing liquid to enter. A filter layer is disposed on the outer surface of the water-absorbing side of the salt discharge pipe, and the filter layer is used to prevent soil particles from entering the salt discharge pipe. The method for laying the saline-alkali land restoration system for reducing alkali and desalination includes the following steps: S10. Remove part of the surface layer of saline-alkali soil in the main soil mass to form a depression on the surface of the main soil mass. S20. Lay the anti-seepage and salt-barrier layer at the bottom of the concave part, and backfill on top of the anti-seepage and salt-barrier layer to obtain the first soil layer structure; S30. Lay a salt drainage pipe above the first soil layer structure, and perform a second backfill on the side of the salt drainage pipe on the water absorption side to cover it, so that the water absorption side of the salt drainage pipe is exposed. S40. Lay a filter layer on the water-absorbing side of the salt discharge pipe and backfill on top of the filter layer so that the concave part is filled to obtain a second soil layer structure. S50. Lay a rinsing device on the surface of the second soil layer structure.

2. The saline-alkali land remediation system for reducing alkali and removing salt as described in claim 1, characterized in that, The rinsing device includes multiple rinsing pipes arranged at intervals along the horizontal direction. The portion of the outer surface of each rinsing pipe facing the salt discharge pipe forms a water outlet side, and multiple rinsing holes are provided on the water outlet side.

3. The saline-alkali land remediation system for reducing alkali and removing salt as described in claim 2, characterized in that, The interval between any two adjacent rinse pipes is 0.5~1.5m; and / or, The inner diameter of each of the rinse tubes is 8-12 mm; and / or, The interval between any two adjacent rinse holes is 0.3~0.7m; and / or, The inner diameter of each of the rinse holes is 2~5mm.

4. The saline-alkali land remediation system for reducing alkali and removing salt as described in claim 1, characterized in that, The salt discharge device includes a plurality of salt discharge pipes, which are arranged at intervals along a horizontal direction, with a spacing of 4-6 meters between each adjacent salt discharge pipe; and / or, The distance between the salt drainage pipe and the upper surface of the main soil mass is 45-55 cm; and / or, The salt drainage pipe is installed at an incline, with a burial slope of 0.8% to 1.2%; and / or, The inner diameter of the salt discharge pipe is 100~160mm; and / or, The opening rate of the salt drainage pipe is 2%~4%; and / or, The inner diameter of each of the aforementioned water-absorbing holes is 4~8mm; and / or, The interval between two adjacent water absorption holes is 1~3cm.

5. The saline-alkali land remediation system for reducing alkali and removing salt as described in claim 1, characterized in that, The filter media of the filter layer comprises a mixture of sand, gravel, and pebbles, wherein the sand has a particle size of 0.5-2 mm, the gravel has a particle size of 2-4 mm, and the pebbles have a particle size of 4-8 mm; and / or, The thickness of the filter layer is 80~100mm.

6. The saline-alkali land remediation system for reducing alkali and removing salt as described in claim 1, characterized in that, The negative pressure air extraction device includes an air extraction pump and multiple air extraction pipes arranged at intervals in the horizontal direction. Each of the aforementioned air extraction pipes extends vertically, with one end connected to the air extraction pump and the other end connected to the salt discharge pipe. At least one air extraction hole is provided on the lower outer surface of each of the aforementioned air extraction pipes, and a filter screen is provided in the air extraction hole to enable the air extraction pipe to draw in gas from the soil while preventing soil particles from clogging the air extraction hole.

7. The saline-alkali land remediation system for reducing alkali and removing salt as described in claim 6, characterized in that, The inner diameter of each of the aforementioned suction tubes is 60~80mm and / or, The interval between two adjacent extraction pipes is 4-6 m; and / or, The interval between two adjacent air extraction holes is 8-10 cm; and / or, The inner diameter of each of the aforementioned air extraction holes is 4~8mm.

8. The saline-alkali land remediation system for reducing alkali and removing salt as described in claim 1, characterized in that, The distance between the impermeable and salt-barrier layer and the upper surface of the main soil body is 45-55 cm; and / or, The thickness of the seepage-proof and salt-barrier layer is 10~20cm.

9. A method for laying a saline-alkali land remediation system for reducing alkali and desalinizing, based on the saline-alkali land remediation system for reducing alkali and desalinizing as described in any one of claims 1 to 8, characterized in that, The method for laying the saline-alkali land restoration system for reducing alkali and desalination includes the following steps: S10. Remove part of the surface layer of saline-alkali soil in the main soil mass to form a depression on the surface of the main soil mass. S20. Lay the anti-seepage and salt-barrier layer at the bottom of the concave part, and backfill on top of the anti-seepage and salt-barrier layer to obtain the first soil layer structure; S30. Lay a salt drainage pipe above the first soil layer structure, and perform a second backfill on the side of the salt drainage pipe on the water absorption side to cover it, so that the water absorption side of the salt drainage pipe is exposed. S40. Lay a filter layer on the water-absorbing side of the salt discharge pipe and backfill on top of the filter layer so that the concave part is filled to obtain a second soil layer structure. S50. Lay a rinsing device on the surface of the second soil layer structure.

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