Well-pipe coordinated saline-alkali land improvement system and construction method thereof

Abstract

The present invention discloses a well-pipe coordinated saline-alkali land improvement system and a construction method thereof, and belongs to the technical field of saline-alkali land management. The system includes a forced drainage well and a precipitation well set on the soil, and a drainage ditch set vertically in the underground runoff. The forced drainage well and the precipitation well are arranged in a grid node manner along the drainage direction, and are connected by drainage pipes to form a well network. The precipitation well discharges water into the drainage ditch through the drainage pipe. When the groundwater level rises rapidly, the groundwater level is quickly dropped by extracting water from the forced drainage well. After the water is drawn from the water diversion trough, it is filtered and enters the drainage pipe. The filter layer wrapped around the drainage pipe reduces the amount of sediment entering the pipe. At the same time, the sedimentation effect of the precipitation well avoids sediment deposition in the drainage pipe during small water flows, thereby blocking the drainage pipe. At the same time, a spare fifth filter layer is provided to extend the service life of the facility.

Description

Technical Field

[0001] The present invention belongs to the technical field of saline-alkali land treatment, and in particular relates to a well-pipe coordinated saline-alkali land improvement system and a construction method thereof. Background Art

[0002] Saline-alkali land has hindered the high-quality development of my country's agriculture, especially in the arid and semi-arid regions of Northwest China, where high groundwater levels and high evaporation rates make soil salinization extremely likely. Saline-alkali land improvement typically involves lowering the groundwater level. Currently, the most common drainage method involves laying underground pipes, which collect water and discharge it into drainage ditches. However, the drainage depth controlled by these pipes remains constant. Rapidly rising groundwater levels can lead to poor drainage and secondary salinization. Furthermore, underground drainage often becomes clogged with sediment, and there is a lack of long-term mechanisms to extend the service life of these pipes. Summary of the Invention

[0003] The purpose of the present invention is to provide a well-pipe coordinated saline-alkali land improvement system composed of a forced drainage well, a precipitation well, a drainage pipe, a water diversion trough and a drainage ditch. Water is drawn in by the water diversion trough, drained by the drainage pipe, sediment and water are precipitated by the precipitation well, and the forced drainage well is drained quickly. When the groundwater level rises rapidly, the water body of the forced drainage well is extracted to make the groundwater level drop rapidly. After the water is drawn in by the water diversion trough, it enters the drainage pipe through filtration, and the filter layer wrapped outside the drainage pipe reduces the amount of sediment entering the pipe. At the same time, the sedimentation effect of the precipitation well avoids the sediment deposition in the drainage pipe during small water flow and clogging the drainage pipe. At the same time, a spare fifth filter layer is provided to extend the service life of the facility.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] The well-pipe coordinated saline-alkali land improvement system is characterized in that it includes forced drainage wells and precipitation wells set on the soil, and drainage ditches set vertically in the underground runoff. The forced drainage wells and precipitation wells are arranged in a grid node manner along the drainage direction and are connected by drainage pipes to form a well network, wherein 12 precipitation wells are arranged around each forced drainage well, and the precipitation wells discharge water into the drainage ditch through the drainage pipe. Each drainage ditch controls no more than 3 rows of forced drainage wells, and a water diversion trough is provided on the upper part of the drainage pipe in the vertical direction of the drainage ditch. The fourth filter layer abutting the drainage pipe is provided downward from the water diversion trough at the intersection of the water diversion trough and the vertical space of the drainage pipe, and a fifth filter layer abutting the drainage pipe at the bottom is provided at the intersection of the center line of two adjacent water diversion troughs and the vertical space of the drainage pipe. The drainage pipe is a corrugated pipe full of holes, and the outside of the drainage pipe is wrapped with a third filter layer.

[0006] As a further description of the above technical solution:

[0007] The slope of the soil surface meets the requirement of 5‰ to 10‰, and the slope direction is consistent with the groundwater flow direction; the slope and slope direction of the water diversion trough are consistent with the soil surface, the drainage pipe is consistent with the slope of the soil surface along the direction of the soil, the specifications of the forced drainage wells are consistent, the specifications of the precipitation wells are consistent, the height of the forced drainage wells exposed to the ground is consistent, and the height of the precipitation wells from the ground is consistent.

[0008] As a further description of the above technical solution:

[0009] The precipitation well is buried underground, and each precipitation well is composed of a second circumferentially arranged filter layer supported by a precipitation well support column, the precipitation well support column is inserted into the ground, and a precipitation well cover is provided on the upper part of the precipitation well. The burial depth of the precipitation well cover is greater than the depth of the water diversion trough, and the covering radius of the precipitation well cover is greater than the radius of the second filter layer. A through hole is opened on the precipitation well cover, and a ventilation pipe is inserted in the through hole. The part of the ventilation pipe located inside the precipitation well is covered with holes, and the part of the ventilation pipe located outside the precipitation well is a retractable pipe body with a cover; the upper part of the forced drainage well is exposed to the outside of the soil, and each forced drainage well is composed of a first circumferentially arranged filter layer supported by a forced drainage well support column, the forced drainage well support column is inserted into the ground, and the periphery of the part of the forced drainage well support column exposed to the ground is prefabricated with permeable concrete, and a forced drainage well cover is provided on the upper part of the forced drainage well, and a forced drainage pump is arranged inside the forced drainage well, and the outlet of the forced drainage pump is led to the ground through a pipe.

[0010] As a further description of the above technical solution:

[0011] There are 8 supporting columns for the forced drainage well and the precipitation well, which are arranged in an array of equal-radius circles. The length of the part inserted into the underground is not less than 50 cm. A M-shaped frame is provided on the upper part of the forced drainage well and the precipitation well, which abuts against the outer walls of the 8 supporting columns. The 8 branches of the M-shaped frame are composed of 2 solid pipes with external threads and 1 threaded sleeve with internal threads. The end of the threaded solid pipe located on the outside is provided with an abutment joint, which is C-shaped and has a rubber layer on the outside. The length of a single drainage pipe does not exceed 50 m, and the distance between the pipe mouth of the drainage pipe and the bottom elevation of the precipitation well is not less than 100 cm, and the distance between the pipe mouth and the bottom elevation of the forced drainage well is not less than 250 cm.

[0012] As a further description of the above technical solution:

[0013] The third filter layer includes a third coarse sand layer, a third medium sand layer and a third fine sand layer arranged in sequence from the inside to the outside; the fourth filter layer includes a fourth fine sand layer, a fourth medium sand layer and a fourth coarse sand layer arranged in sequence from the top to the bottom; the structure of the fifth filter layer is completely consistent with that of the fourth filter layer; the first filter layer includes a first coarse sand layer, a first medium sand layer and a first fine sand layer arranged in sequence from the inside to the outside; the structure of the second filter layer is completely consistent with that of the first filter layer except for the height difference; the sand of the filter layer is selected from the surface covering sand of the sand pressing land, and is used in the filter layer after screening and grading.

[0014] As a further description of the above technical solution:

[0015] The three layers of sand in the third filter layer are all wrapped with geotextile to form a sand blanket, and are tied layer by layer to the outside of the corrugated pipe with binding tape; the length of a single drainage pipe is 15 to 20 meters in severely saline-alkali land, 20 to 30 meters in moderately saline-alkali land, and no more than 50 meters in slightly saline-alkali land; the top of the precipitation well is not less than 60 cm from the ground, the water diversion trough is filled with a mixture of gravel and straw, the filling depth is not less than 20 cm, and the top of the water diversion trough is not less than 40 cm from the ground.

[0016] As a further description of the above technical solution:

[0017] A mud collecting trough is provided at the bottom of the drainage ditch, a gravel layer is provided on the left bank of the drainage ditch, and gabion cages are provided outside the gravel layer. The thickness of the gravel layer is 10 cm, and the thickness of the gabion cages is 30 cm. Only gabion cages are provided on the right bank of the drainage ditch, and the thickness of the gabion cages is 30 cm. Ecological holes are also provided on the left bank of the drainage ditch.

[0018] The present invention also provides a construction method of a well-pipe coordinated saline-alkali land improvement system, which is characterized by comprising the following steps:

[0019] S1. Soil chemical analysis and groundwater survey: Select the restoration area and divide it into multiple plots. Use the five-point sampling method to collect five soil columns from each plot. Test the soil salt content, salt composition, and soil particle size composition at different depths to determine the type and degree of salinization. Monitor the groundwater in the restoration area and analyze the groundwater quality and flow direction.

[0020] S2. Land leveling and drainage ditch excavation: Drainage ditches shall be excavated vertically along the groundwater flow direction, and the soil in the restoration area shall be leveled to ensure that the land slope is consistent with the groundwater flow direction and the land slope meets the requirements of 5‰ to 10‰;

[0021] S3. Locating, excavating, and laying out drainage wells, dewatering wells, and drainage pipes: Design and excavate the spacing, number, and depth of drainage wells and dewatering wells based on the type and degree of salinization and the area of ​​the remediation site. Ensure that the length of a single drainage pipe does not exceed 50 meters, the top of the dewatering well is at least 60 cm above the ground, and all underground structures are arranged in a parallelogram in vertical space. After excavation, construct the drainage wells, dewatering wells, and drainage pipes.

[0022] S4. Installation of the fourth and fifth inverse filter layers: After the drainage pipes are laid, determine the location of the diversion troughs. When backfilling the soil, first backfill and install the fourth inverse filter layer at the intersection of the diversion trough and the vertical space of the drainage pipe. Then, backfill and install the fifth inverse filter layer at the intersection of the center line of two adjacent diversion troughs and the vertical space of the drainage pipe.

[0023] S5. Deep plowing and rotary tillage: After the soil is backfilled, spread organic fertilizer to a thickness of not less than 15 cm, and then deep plowing and rotary tillage should be carried out. The depth of deep plowing and rotary tillage should be near the top of the fourth and fifth filter layers to allow the organic fertilizer to fully blend with the soil.

[0024] S6. Water diversion trough layout: excavate the water diversion trough and fill it with a mixture of gravel and straw to a depth of not less than 20 cm, with the top of the water diversion trough not less than 40 cm from the ground. After filling, backfill with soil;

[0025] S7. Drainage ditch lining: concrete lining is used for the bottom of the drainage ditch and the mud collecting trough, crushed stone layer and gabion stone cage are used for the left bank of the drainage ditch, and gabion stone cage is used for the right bank of the drainage ditch.

[0026] As a further description of the above technical solution:

[0027] The following steps are also included:

[0028] S8. Setting of ridges: Before planting crops, set ridges on the soil surface. The direction of the ridges should be consistent with the direction of the drainage ditch. The height of the ridges should be 15 to 25 cm. One ridge should be set every 5 meters or so. It must be set near the side of the strong drainage well close to the drainage ditch.

[0029] As a further description of the above technical solution:

[0030] The steps include:

[0031] S9. Reconstruction of water diversion trough: When the facility has been used for a certain number of years and the water diversion trough is blocked, resulting in poor water diversion effect, the original water diversion trough shall be abandoned and a new water diversion trough shall be excavated and set up in the center line of two adjacent water diversion troughs, so that the new water diversion trough is located above the fifth filter layer.

[0032] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0033] 1. In the present invention, water is drawn in through a water diversion trough, which improves the water collection effect. After the water is drawn in, it is filtered through the fourth filter layer. Combined with the three layers of sand set on the drainage pipe, a large amount of fine-grained soil is prevented from entering the drainage pipe, achieving the effect of only discharging salt and less mud. A small amount of sediment entering the pipeline will also be precipitated through the precipitation well, avoiding sediment deposition in the drainage pipe during small water flows. When the groundwater level rises rapidly, the groundwater level can be quickly lowered by extracting water from the forced drainage well. At the same time, the water extracted from the forced drainage well can be transported to the ventilation pipe to disturb the sediment deposited at the bottom of the precipitation well, thereby cleaning the precipitation well. The fifth filter layer is introduced. When the water diversion effect of the first water diversion trough is not good, a new water diversion trough is opened and the spare fifth filter layer is activated, thereby extending the service life of the facility.

[0034] 2. In the present invention, the soil surface slope satisfies 5‰ to 10‰, and the slope direction is consistent with the groundwater flow direction. The appropriate slope is conducive to drainage, preventing summer rainstorms from causing floods, soil erosion and soil erosion. All underground structures are arranged in a parallelogram in vertical space. That is, in the vertical direction, the relative positions of each structure are on the upper and lower parallel lines of the parallelogram, that is, the position of the structure relative to the ground surface remains unchanged, so that the water flow in the drainage pipe always maintains a relatively stable slope, preventing congestion and stagnation, and improving drainage efficiency.

[0035] 3. In the present invention, each precipitation well is composed of a second filter layer arranged circumferentially supported by precipitation well support columns. The same strong drainage well structure is similar. The gaps between the support columns are arranged to facilitate water seepage, which not only ensures the stability of water seepage but also ensures the stability of the structure. The coverage radius of the precipitation well cover is larger than the radius of the second filter layer, which can prevent soil from entering the well at the position of the well cover, giving full play to the role of the second filter layer. The outer periphery of the strong drainage well support column exposed to the ground is prefabricated with permeable concrete. The prefabricated concrete is permeable concrete, which can prevent surface runoff from directly entering the strong drainage well and filtering through the permeable concrete. When heavy rainfall occurs, the alkaline water in the strong drainage well can be discharged in advance and infiltrated with fresh water or brackish water, which not only realizes the storage of rainwater resources, but also reduces the concentration of underground saline-alkali water through fresh water, accelerating the improvement of saline-alkali land. When sediment is deposited at the bottom of the strong drainage well, it can be directly extracted from the well in the form of mud through the disturbance of the strong drainage pump, realizing the cleaning of the strong drainage well. A ridge is set up near the drainage ditch on one side of the strong drainage well to retain a certain amount of water during rainfall. The gravity potential energy of the water body accelerates infiltration, promoting salt drainage and water storage.

[0036] 4. In the present invention, the eight branches of the M-shaped frame are composed of two solid tubes with external threads and one threaded sleeve with internal threads. The end of the threaded solid tube located on the outside is provided with an abutment joint. The abutment joint is C-shaped and has a rubber layer on the outside. Due to the inevitable errors in field construction, the length of the M-shaped frame branch is adjusted by twisting the threaded sleeve with internal threads so that the abutment joint can fully contact with the support column.

[0037] 5. In the present invention, the bottom of the drainage ditch and the mud collecting trough are lined with concrete. The concrete lining is conducive to mechanical cleaning of silt on the one hand, and can also play a certain role in water storage on the other hand, laying the foundation for the development of saline-alkali fishery farming (such as saline-alkali water crab farming, etc.) in the drainage ditch in the future. A layer of waterproof cloth is set on the right bank. The installation of the waterproof cloth can realize modular management and prevent the saline-alkali water produced by the upper saline-alkali land from entering the next level of fields. The sand of the filter layer is selected from the surface covering sand of the sand-pressing land, and is used for the filter layer after screening and grading, realizing the comprehensive utilization of the sand in the depressurized sand field.

[0038] 6. The present invention has a simple structure, simple construction process, low cost, and long service life, which is conducive to the large-scale promotion and application of saline-alkali land treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the well-pipe-trench plan layout of the present invention;

[0040] Figure 2 For the present invention Figure 1 Schematic diagram of the control range of the strong drainage well in center A;

[0041] Figure 3 This is a schematic structural diagram of the drainage pipe and the outer filter material of the present invention;

[0042] Figure 4 This is a schematic diagram of the cross-sectional structure of the forced drainage well of the present invention (the cross-sectional structure of the precipitation well is consistent with this);

[0043] Figure 5 This is a schematic diagram of the arrangement of the forced drainage wells of the present invention;

[0044] Figure 6 This is a schematic diagram of the arrangement of the precipitation wells of the present invention;

[0045] Figure 7 This is a schematic diagram of the arrangement of the fourth filter layer of the present invention;

[0046] Figure 8 This is a schematic diagram of the arrangement of the fifth filter layer of the present invention;

[0047] Figure 9 This is a schematic diagram of the M-shaped frame branch structure of the present invention;

[0048] Figure 10 It is a schematic diagram of the cross-sectional structure of the drainage ditch of the present invention.

[0049] Legend:

[0050] 1. Soil; 2. Forced drainage well; 21. Forced drainage well support column; 22. First filter layer; 221. First coarse sand layer; 222. First medium sand layer; 223. First fine sand layer; 23. Forced drainage well cover; 3. Dewatering well; 31. Dewatering well support column; 32. Second filter layer; 321. Second coarse sand layer; 322. Second medium sand layer; 323. Second fine sand layer; 33. Dewatering well cover; 34. Ventilation pipe; 4. Drain pipe; 41. Corrugated pipe; 42. Third filter layer; 421. Third coarse sand layer; 422 .Third medium sand layer; 423. Third fine sand layer; 43. Fourth filter layer; 431. Fourth fine sand layer; 432. Fourth medium sand layer; 433. Fourth coarse sand layer; 44. Fifth filter layer; 441. Fifth fine sand layer; 442. Fifth medium sand layer; 443. Fifth coarse sand layer; 45. Solenoid valve; 5. Drainage ditch; 51. Gabion stone cage; 52. Gravel layer; 53. Mud collecting trough; 6. Water diversion trough; 7. Strong drainage pump; 8. M-shaped frame; 81. Solid pipe; 82. Threaded sleeve; 83. Butt joint. DETAILED DESCRIPTION

[0051] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0052] See also Figure 1-10 The present invention provides a well-pipe coordinated saline-alkali land improvement system. Figure 1, the arrows in the figure indicate the direction of water flow. The system includes a strong drainage well 2 and a precipitation well 3 set on the soil 1, and a drainage ditch 5 set vertically in the underground runoff, that is, the direction of the drainage ditch 5 is perpendicular to the direction of groundwater flow, which is conducive to full and efficient interception. The strong drainage well 2 and the precipitation well 3 are arranged in a grid node manner along the drainage direction and are connected by a drainage pipe 4 to form a well network. Each grid is an equilateral rhombus. The strong drainage well 2 is deeper and has a larger catchment area. When it is necessary to quickly lower the groundwater level, the water in the strong drainage well 2 can be extracted to make the groundwater funnel-shaped, which can be quickly lowered. As shown in Figure A, 12 precipitation wells 3 are arranged around each forced drainage well 2. The precipitation wells 3 discharge water into the drainage ditch 5 through the drainage pipe 4. On the one hand, the function of the precipitation well 3 is to deposit sediment. Fine sediment particles will seep out of the drainage pipe 4, but the water flow in the drainage pipe 4 is sometimes very small, so the pipe will be clogged. Therefore, the precipitation well 3 is set to allow fine sediment to settle without affecting drainage. When the sediment accumulates to a certain extent, it can be discharged through flushing with large amounts of water. On the other hand, it serves to collect water and lower the groundwater level. The number of forced drainage wells 2 controlled by each drainage ditch 5 does not exceed 3 rows. Generally, the control range of 2 rows can optimize the project cost and the improvement effect of saline-alkali land. When the actual area design is greater than 2 rows but less than 3 rows, it is not necessary to set a third row of forced drainage wells 2. Only precipitation wells 3 are required. Please refer to Figure 2 , a water diversion trough 6 is provided at the upper part of the drainage pipe 4 in the vertical direction of the drainage ditch 5. The function of the water diversion trough is to guide water so that the water body can be collected at the upper part of the drainage pipe 4 and then seep into the drainage pipe 4. A fourth inverted filter layer 43 is provided downward from the water diversion trough 6 at the intersection of the vertical space of the drainage pipe 4. The inverted filter layer can allow the water body to directly reach the water diversion trough 6, while reducing the soil obstruction and preventing a large number of fine soil particles from entering the drainage pipe 4. A fifth inverted filter layer 44 is provided at the intersection of the center line of the two adjacent water diversion troughs 6 and the vertical space of the drainage pipe 4, the lower part of which is inverted filter layer 44. The purpose of the fifth inverted filter layer 44 is to serve as a backup. As the operation time increases, the water diversion trough 6 and the fourth inverted filter layer 43 will inevitably become clogged. If a new inverted filter layer is re-installed, the cost will increase and the construction will be difficult. Therefore, a spare fifth inverted filter layer 44 is provided. When blockage occurs, it is only necessary to re-install the water diversion trough 6 at the upper part of the reserved position, which greatly reduces the cost and improves the efficiency. Please refer to Figure 3Drain pipe 4 is a corrugated pipe 41 with holes throughout. The bellows 41 has good pressure resistance and is not easily crushed. A third filter layer 42 is wrapped around the outside of the drain pipe 4. This layer, directly wrapped around the outside of the bellows 41, further isolates sediment, reducing the amount of sediment entering the pipe. This layer allows small particles less than 0.1 mm in diameter, with a particle content of less than 5%, to be carried away by seepage without affecting the stability of the soil skeleton, but without clogging the pores of the filter layer. A solenoid valve 45 is installed at the outlet of the drainage ditch 5 to achieve controlled drainage, adjusting it according to the crop growth period to avoid excessive drainage and waste of water resources.

[0053] In the embodiment of the present invention, the surface slope of the soil body 1 satisfies 5‰ to 10‰, and the slope direction is consistent with the groundwater flow direction. The appropriate slope facilitates drainage and prevents summer rainstorms from causing flooding, which can cause soil erosion and water and soil loss. At the same time, the slope should not be too large, as a large slope will cause a large amount of water loss and fail to achieve the infiltration and alkali drainage effect. This slope is achieved through leveling. The slope and slope of the water diversion trough 6 are consistent with the surface slope of the soil body 1. The drainage pipe 4 is consistent with the surface slope of the soil body 1 along the direction of the soil body 1. The specifications of the forced drainage well 2 and the precipitation well 3 are consistent. The height of the forced drainage well 2 above the ground is consistent, and the height of the precipitation well 3 from the ground is consistent. Ensure that all underground structures are arranged in a parallelogram in vertical space. That is, in the vertical direction, the relative positions of each structure are on the upper and lower parallel lines of the parallelogram, that is, the positions of the structures relative to the ground surface remain unchanged, so that the water flow in the drainage pipe 4 always maintains a relatively stable slope and does not cause congestion and stagnation.

[0054] In the embodiment of the present invention, please refer to Figure 3-6And 9, the precipitation well 3 is buried underground, occupying as little arable land as possible, which is conducive to later farming. Each precipitation well 3 is composed of a precipitation well support column 31 supporting a circumferentially arranged second filter layer 32. The gap between the support columns facilitates water seepage, which not only ensures the stability of water seepage, but also ensures the stability of the structure. The precipitation well support column 31 is inserted into the ground, and a precipitation well cover 33 is provided on the upper part of the precipitation well 3. The burial depth of the precipitation well cover 33 is greater than the depth of the water diversion trough 6, and the covering radius of the precipitation well cover 33 is greater than the radius of the second filter layer 32, which can prevent soil from entering the well at the position of the well cover, and give full play to the role of the second filter layer 32. A through hole is provided on the precipitation well cover 33, and a vent pipe 34 is inserted into the through hole. The part of the vent pipe 34 located inside the precipitation well 3 is full of holes, and the part of the vent pipe 34 located outside the precipitation well 3 is a retractable tube body with a cover. When used daily, the cover is opened and the vent pipe 34 produces ventilation to avoid negative pressure and hinder drainage. When farming is required, a high-pressure water gun can be used to flush the surrounding area of ​​the tube body, cover the cover, and bury the retractable covered tube body to a suitable depth below the ground. If a corrugated retractable tube is used, it can be contracted by pressing down to avoid affecting farming such as mechanical harvesting, rotary tillage, etc. It can be dug out or flushed out after farming is completed. When there is a lot of sediment accumulated inside the precipitation well 3, when the groundwater level is high or the drainage pipe 4 has a large drainage volume, the water in the strong drainage well 2 can be extracted and connected to the vent pipe 34 to act as a water supply disturbance, so that the sediment accumulated at the bottom is stirred into mud, which is flushed out into the drainage ditch 5 with the large water flow, thereby achieving the flushing of the precipitation well 3.

[0055] The upper portion of the forced drainage well 2 is exposed outside the soil body 1. Each forced drainage well 2 consists of a first filter layer 22 arranged circumferentially supported by a forced drainage well support column 21. The forced drainage well support columns 21 are inserted into the ground. The portion of the forced drainage well support column 21 exposed above ground is prefabricated with permeable concrete. The upper portion of the forced drainage well 2 is provided with a forced drainage well cover 23. The interior of the forced drainage well 2 is equipped with a forced drainage pump 7, and the outlet of the forced drainage pump 7 is led to the ground through a pipe. The forced drainage well 2 has the same structure and function as the precipitation well 3. The prefabricated concrete is permeable concrete, which can prevent surface runoff from directly entering the forced drainage well 2. The permeable concrete is filtered. When heavy rainfall occurs, the alkaline water in the forced drainage well 2 can be drained in advance and infiltrated with fresh water or slightly brackish water. This not only achieves rainwater conservation, but also reduces the concentration of underground saline water with fresh water, accelerating the improvement of saline-alkali land. When sediment accumulates at the bottom of the forced drainage well 2, it can be directly pumped out of the well in the form of mud through the disturbance of the forced drainage pump 7, achieving the cleaning of the forced drainage well 2.

[0056] In the embodiment of the present invention, the forced drainage well 2 and the dewatering well 3 both have 8 support columns, which are arranged in an array of equal-radius circles and have better stability. The length of the part inserted into the underground is not less than 50 cm, which depends on the soil quality. Since the support columns are customized in advance, the length of the columns inserted into the underground in the same repair area is consistent, thereby ensuring that the relative positions of the structures remain unchanged. A M-shaped frame 8 is provided on the upper part of the forced drainage well 2 and the dewatering well 3, which abuts against the outer walls of the 8 support columns. The 8 branches of the M-shaped frame 8 are composed of 2 solid tubes 81 with external threads and 1 threaded sleeve 82 with internal threads. The end of the threaded solid tube 81 located on the outside is provided with a butt joint 83, which is C-shaped and has a rubber layer on the outside. Due to the inevitable errors in field construction, the length of the branches of the M-shaped frame 8 is adjusted by twisting the threaded sleeve 82 with internal threads, so that the butt joint 83 can fully contact the support column. The length of a single drainage pipe 4 should not exceed 50 meters. The length of a single drainage pipe 4 is 15-20 meters in severely saline-alkali land, 20-30 meters in moderately saline-alkali land, and no more than 50 meters in slightly saline-alkali land. The length should be adjusted based on the type and size of the saline-alkali land to ensure both effective restoration and reduced project investment. The outlet of the drainage pipe 4 should be at least 100 cm from the bottom elevation of the drainage well 3 and at least 250 cm from the bottom elevation of the forced drainage well 2, leaving ample space to improve drainage and provide ample space for sediment deposition.

[0057] In the embodiment of the present invention, please refer to Figure 3-8The third filter layer 42 includes a third coarse sand layer 421, a third medium sand layer 422 and a third fine sand layer 423 arranged in sequence from the inside to the outside. The three layers of sand in the third filter layer 42 are all wrapped with geotextile to form a sand blanket, and are tied layer by layer to the outside of the corrugated pipe 41 with binding tape, which is convenient for construction and conducive to ensuring the stability of the filter layer; the fourth filter layer 43 includes a fourth fine sand layer 431, a fourth medium sand layer 432 and a fourth coarse sand layer 433 arranged in sequence from top to bottom. The structure of the fifth filter layer 44 is exactly the same as that of the fourth filter layer 43. The first filter layer 22 includes a first coarse sand layer 221, a first medium sand layer 222 and a first fine sand layer 223 arranged in sequence from the inside to the outside. The second filter layer 32 is exactly the same as the first filter layer 22 except for the height difference. The sand of the filter layer is selected from the surface covering sand of the sand pressure land, and is used for the filter layer after screening and grading, thereby realizing the reuse of sand in the depressurized sand field and helping to protect the ecological environment. The side of the filter layer that contacts the soil is filled with fine sand. The main purpose is to prevent a large amount of fine particles in the soil from entering the pipe and maintain the stability of the soil structure. The top of the precipitation well 3 is at least 60 cm above the ground to ensure that it is below the root layer of most crops. The water diversion trough 6 is filled with a mixture of gravel and straw to a depth of at least 20 cm, and the top of the water diversion trough 6 is at least 40 cm above the ground. This ensures drainage, ensures that daily rotary tillage will not damage the soil, and ensures that the straw is decomposed to add organic matter to the soil. Gravel is also preferably used as the surface covering sand and gravel for sand-pressing land.

[0058] In the embodiment of the present invention, please refer to Figure 10 , a mud collecting trough 53 is provided at the bottom of the drainage ditch 5, a gravel layer 52 is provided on the left bank of the drainage ditch 5, a gabion gabion cage 51 is provided on the outside of the gravel layer 52, the thickness of the gravel layer 52 is 10 cm, the thickness of the gabion gabion cage 51 is 30 cm, and only the gabion gabion cage 51 is provided on the right bank of the drainage ditch 5, the thickness of the gabion gabion cage 51 is 30 cm, and the left bank of the drainage ditch 5 is also provided with ecological holes. The depth of excavation of the drainage ditch 5 should be deep to meet the drainage requirements. Wherein the left bank of the drainage ditch 5 is directly excavated into a trapezoid, and the right bank is first excavated into a rectangle. After excavation, a layer of waterproof cloth is set on the right bank. The buried depth of the waterproof cloth should be greater than the depth of the drainage ditch 5, and at least extend more than 100 cm to the lower part of the drainage ditch 5. The purpose of building the slope protection is to facilitate the maintenance of the drainage ditch 5 in the later stage, to avoid soil collapse after long-term use, which causes it to lose its drainage effect. In areas with soft, easily collapsed soil, the left bank of drainage ditch 5 needs to be anchored with anchor rods, with the lining height approximately 10 cm above the soil surface. The bottom of drainage ditch 5 and sludge collection trough 53 are lined with concrete. The lower portion of sludge collection trough 53 is a standard rectangular shape. This concrete lining facilitates mechanical sludge removal and serves as a water storage facility, laying the foundation for future development of saline-alkali aquaculture (such as crab farming) within drainage ditch 5. Ecological holes are reserved in the lining to facilitate the habitat of aquatic life.

[0059] The construction method of the well-pipe coordinated saline-alkali land improvement system provided by the present invention specifically includes the following steps:

[0060] S1. Soil Chemical Analysis and Groundwater Survey: Select remediation areas and use drone hyperspectral analysis to conduct preliminary identification and classification of saline-alkali land. Drone hyperspectral analysis is a mature technology and will not be described in detail here. Based on the initial hyperspectral classification results, saline-alkali land of the same type will be grouped together as closely as possible, following the principle of proximity. After this initial classification, five soil columns are collected from each plot using the five-point sampling method. The columns are preferably 100 cm deep, with samples separated every 20 cm. Soil salinity, salt composition, and soil particle size are measured at different depths to further assess the saline-alkali land. This avoids the drawback of hyperspectral inversion, which only reflects the surface layer, and allows for more accurate classification and verification of saline-alkali land types. Simultaneously, groundwater in the study area is monitored to analyze groundwater quality and flow. Based on the groundwater flow, quality, and verified saline-alkali land type, the project overview and specific parameters are designed using empirical methods, expert evaluation, or other mathematical models available in the literature. Generally, each drainage ditch (5) is required to control no more than three rows of forced drainage wells (2), preferably two.

[0061] S2. Land Leveling and Drainage Ditch 5 Excavation: Use a bulldozer or rotary tiller to level the soil surface in the remediation area based on the actual ground flatness. Ensure that the land slope aligns with the groundwater flow direction and that the land slope is 5‰ to 10‰. A suitable slope facilitates drainage and prevents summer rainstorms from causing flooding, which can cause soil erosion and water and soil loss. At the same time, the slope should not be too steep, as this will cause a large amount of water loss and fail to achieve the infiltration and alkali drainage effect. The water will eventually drain into Drain 5, so it is necessary to excavate Drain 5. During excavation, the excavation should be vertical to the groundwater flow direction to intercept the groundwater. The Drain 5 should be deep enough to meet drainage requirements. The left bank of drainage ditch 5 is directly excavated into a trapezoidal shape, while the right bank is first excavated into a rectangular shape. After excavation, a layer of tarpaulin is placed on the right bank. The tarpaulin should be buried deeper than the depth of drainage ditch 5, extending at least 100 cm below the bottom of drainage ditch 5. The installation of tarpaulin allows for modular management and prevents saline-alkali water from the upper saline-alkali land from entering the fields below. Backfill is then carried out to form a trapezoidal shape. A mud collection trough 53 is excavated at the bottom of drainage ditch 5. Because fine soil is carried over time during drainage, it accumulates in the ditch. The mud collection trough 53 facilitates mechanical removal.

[0062] S3. Positioning, excavation and layout of forced drainage wells 2, precipitation wells 3 and drainage pipes 4: Design and excavate the spacing, number and depth of forced drainage wells 2 and precipitation wells 3 according to the type and degree of salinization and the area of ​​the repair area, and ensure that the length of a single drainage pipe 4 does not exceed 50m to avoid excessive length, which will reduce the effectiveness of precipitation and alkali drainage. The length of a single drainage pipe 4 is generally 15-20m in severe saline-alkali land, 20-30m in moderate saline-alkali land, and not more than 50m in mild saline-alkali land. The top of the precipitation well 3 should be no less than 60cm from the ground. Sufficient space should be reserved on the upper part of the precipitation well 3, which should exceed the tillage layer to avoid damage to the precipitation well 3 during the operation of large machinery, such as collapse, obstruction of rotary tillage, etc. Ensure that all underground structures are arranged in a parallelogram in vertical space, that is, in the vertical direction, the relative positions of each structure are on the upper and lower parallel lines of the parallelogram. For example, under the conditions that the specifications of the forced drainage well 2 and the specifications of the precipitation well 3 are consistent, the height of the forced drainage well 2 exposed to the ground is consistent, the distance between the bottom and the ground is consistent, the height of the upper part of the precipitation well 3 from the ground is consistent, and the height of the lower part from the ground is consistent; use an excavator to dig the well slots for the forced drainage well 2 and the precipitation well 3, and try to dig them into cylindrical slots during excavation to reduce the workload of subsequent filling. Use a trencher to excavate the buried slot for the drainage pipe 4 to connect it with the well slots of the forced drainage well 2 and the precipitation well 3, and then carry out the construction of the forced drainage well 2, the precipitation well 3 and the drainage pipe 4. During the construction of the forced drainage well 2 and the dewatering well 3, the dewatering well support column 31 and the forced drainage well support column 21 are first inserted into the corresponding positions in the well by machinery. There are 8 support columns, which are arranged in an array of equal arc circles. The length of the underground part is not less than 50cm. After the insertion is completed, a layer of geotextile is wrapped around the outer circle of the support column. The specification of the geotextile is not less than 300g / m 2 A M-shaped frame 8 is set at the upper part of the well, abutting the outer walls of the 8 support columns. The abutment 83 is C-shaped and is provided with a rubber layer on the outside. Due to the inevitable errors in field construction, the length of the branch of the M-shaped frame 8 is adjusted by screwing the threaded sleeve 82 with an internal thread, so that the abutment 83 can fully contact with the support column.

[0063] After the layout is completed, the drainage pipe 4 is arranged. The pipe mouth of the drainage pipe 4 extends into the well and is tied at the position where it passes through the geotextile to prevent external filter material from entering the well. Before the drainage pipe 4 is arranged, the third filter layer 42 needs to be tied. The filter layer includes a third coarse sand layer 421, a third medium sand layer 422 and a third fine sand layer 423 arranged from the inside to the outside. The three layers of sand in the third filter layer 42 are all wrapped into a sand blanket with geotextile, and then tied to the corrugated pipe 41 with a tying tape. The thickness of each layer is not less than 5 cm. The gradation of the outermost third fine sand layer 423 is designed according to the soil particle size.

[0064] After the drainage pipe 4 is arranged, the first filter layer 22 and the second filter layer 32 are arranged. During the arrangement, the thin steel plates are processed into C-shapes of different specifications. The first coarse sand layer 221, the first medium sand layer 222, the first fine sand layer 223, and the second coarse sand layer 321, the second medium sand layer 322, and the second fine sand layer 323 are separated and backfilled layer by layer through the steel plates. After backfilling, they are compacted to avoid excessive subsequent collapse. The well slot is opened larger and the outside of the fine sand layer is backfilled with soil. After backfilling, the C-shaped steel plate is pulled out and used for upper backfill or reused in other wells. The purpose of the C-shape is to prevent the arranged drainage pipe 4 from affecting the backfill, and the drainage pipe 4 is reserved through the C-shaped gap. When the water is filled to the upper part of the precipitation well 3, the prefabricated precipitation well cover 33 is covered on the upper part of the second inverted filter layer 32, and the vent pipe 34 is inserted into the through hole opened on the precipitation well cover 33. The vent pipe 34 is about 20 cm away from the bottom of the precipitation well 3. The coverage radius of the precipitation well cover 33 is larger than the radius of the second inverted filter layer 32, which can prevent soil from entering the well at the position of the well cover and give full play to the role of the second inverted filter layer 32. When the water is filled to the upper part of the strong drainage well 2, the first inverted filter layer 22 is no longer filled about 10 cm from the ground. The upper part is set up in the form of precast concrete, so that the outer periphery of the strong drainage well support column 21 exposed to the ground is precast with concrete and extends about 10 cm into the soil. The precast concrete is permeable concrete, which can prevent surface runoff from directly entering the strong drainage well 2 and filtering it through the permeable concrete. When heavy rainfall occurs, the alkaline water in the strong drainage well 2 can be discharged in advance and infiltrated into fresh water or brackish water, which not only realizes the storage of rainwater resources, but also reduces the concentration of underground saline water through fresh water, thereby accelerating the improvement of saline-alkali land.

[0065] S4. Setting of the fourth inverted filter layer 43 and the fifth inverted filter layer 44: After the drainage pipe 4 is laid out, determine the position where the water diversion trough 6 needs to be laid out. When backfilling the soil, first backfill and set the fourth inverted filter layer 43 at the intersection of the water diversion trough 6 and the vertical space of the drainage pipe 4, and backfill and set the fifth inverted filter layer 44 at the intersection of the center line of two adjacent water diversion troughs 6 and the vertical space of the drainage pipe 4. When backfilling, use a thick PVC pipe and put it into the position where the fourth inverted filter layer 43 and the fifth inverted filter layer 44 need to be laid out. Fill the outside of the pipe with soil and fill the inside of the pipe with sand layer by layer. The filling height is calculated according to the depth of the water diversion trough 6 to be buried. After filling, the thick PVC pipe is pulled out for other uses.

[0066] S5. Deep plowing and rotary tillage of the soil: After the soil is backfilled, organic fertilizer is spread. The organic fertilizer can be fermented chicken manure, cow manure, sheep manure, crop straw, etc. The thickness of the organic fertilizer is not less than 15 cm. Then deep plowing is carried out. The depth of deep plowing and rotary tillage of the soil is preferably near the top of the fourth filter layer 43 and the fifth filter layer 44 to fully integrate the organic fertilizer with the soil. At the same time, avoid damaging the filter layer due to deep plowing, and avoid damaging the ventilation pipe 34.

[0067] S6. Layout of water diversion trough 6: Use a trencher to dig the water diversion trough 6, fill the water diversion trough 6 with a mixture of gravel and straw, the filling depth is not less than 20 cm, and the top of the water diversion trough 6 is not less than 40 cm from the ground, and backfill with soil after filling.

[0068] S7, lining of drainage ditch 5: After excavation is completed, drainage ditch 5 is lined. The purpose of building slope protection is to facilitate the maintenance of drainage ditch 5 in the later stage and to prevent soil collapse after long-term use, which causes it to lose its drainage function. On the left bank of drainage ditch 5, a gravel layer 52 is set, and gabion gabions 51 are set outside the gravel layer 52. The thickness of gravel layer 52 is about 10 cm, and the thickness of gabion gabions 51 is about 30 cm. On the right bank of drainage ditch 5, only gabion gabions 51 are set, and the thickness of gabion gabions 51 is about 30 cm. For areas with soft soil and easy collapse, the left bank of drainage ditch 5 also needs to be anchored with anchor rods, and the height of the lining is about 10 cm higher than the soil surface. The bottom of drainage ditch 5 and mud collecting trough 53 are lined with concrete. On the one hand, concrete lining is conducive to mechanical cleaning of silt, and on the other hand, it can play a certain role in water storage, laying the foundation for the development of saline-alkali fishery farming (such as saline-alkali water crab farming, etc.) in the drainage ditch 5 in the later stage. If necessary, ecological holes should be reserved during lining to facilitate the habitat of aquatic organisms.

[0069] After the lining is completed, the field needs to be thoroughly irrigated. The soil must be irrigated thoroughly so that the upper soil can be thoroughly cleaned by the irrigation water, which greatly reduces the salt content of the soil in the cultivated layer. Crop planting can be achieved in the year of restoration. The preferred crop types in the year of planting are salt-alkali tolerant crops such as corn and sunflower. Through the setting of this system, increased production and income can be achieved in the year of planting.

[0070] S8. Setting of ridges: Before planting crops, ridges are set on the soil surface. The direction of the ridges is consistent with the direction of the drainage ditch 5. The height of the ridges is 15 to 25 cm. One ridge is set every 5 meters or so. It must be set near the side of the strong drainage well 2 close to the drainage ditch 5. The purpose of setting ridges is to retain a certain amount of water during rainfall, accelerate infiltration through the gravitational potential energy of the water body, and promote salt drainage.

[0071] S9. Reconstruction of water diversion trough 6: When the facility has been used for a certain number of years and the water diversion trough 6 is blocked, resulting in poor water diversion effect, the original water diversion trough 6 is abandoned, and a new water diversion trough 6 is excavated and set up in the center line of two adjacent water diversion troughs 6, so that the new water diversion trough 6 is located on the upper part of the fifth filter layer 44. The new water diversion trough 6 is also filled with a mixture of gravel and straw, the filling depth is not less than 20 cm, and the top of the water diversion trough 6 is not less than 40 cm from the ground. After filling, backfill with soil. This setting increases the service life of the facility and reduces the later operation and maintenance costs.

[0072] In the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "plurality" refers to two or more, unless expressly limited otherwise. Terms such as "installed," "connected," "connected," and "fixed" should be interpreted broadly. For example, "connected" can mean a fixed connection, a detachable connection, or an integral connection; "connected" can mean a direct connection or an indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0073] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. Well-pipe coordinated saline-alkali land improvement system, characterized by: The invention comprises a forced drainage well (2) and a precipitation well (3) arranged on a soil body (1), and a drainage ditch (5) arranged vertically in the direction of underground runoff, wherein the forced drainage well (2) and the precipitation well (3) are arranged in a grid node manner along the drainage direction and are connected through a drainage pipe (4) to form a well network, wherein 12 precipitation wells (3) are arranged around each forced drainage well (2), and the precipitation well (3) discharges water into the drainage ditch (5) through the drainage pipe (4), and each drainage ditch (5) controls no more than 3 rows of forced drainage wells (2), and the drainage pipe (4) is arranged at a height of 12 meters. A water diversion trough (6) is provided at the upper portion in a vertical direction extending along the drainage ditch (5); a fourth inverted filter layer (43) is provided downwardly from the water diversion trough (6) at the intersection of the vertical space of the drainage pipe (4) and the water diversion trough (6), and the fourth inverted filter layer (43) is provided abutting the drainage pipe (4); a fifth inverted filter layer (44) is provided at the intersection of the center line of two adjacent water diversion troughs (6) and the vertical space of the drainage pipe (4); the drainage pipe (4) is a corrugated pipe (41) covered with holes, and the outside of the drainage pipe (4) is wrapped with a third inverted filter layer (42).

2. The well-pipe coordinated saline-alkali land improvement system according to claim 1, characterized in that: The surface slope of the soil (1) satisfies 5‰ to 10‰, and the slope direction is consistent with the groundwater flow direction; the slope and slope direction of the water diversion trough (6) are consistent with the surface slope of the soil (1); the drainage pipe (4) is consistent with the surface slope of the soil (1) in the direction of the soil (1); the specifications of the forced drainage well (2) are consistent; the specifications of the precipitation well (3) are consistent; the height of the forced drainage well (2) exposed above the ground is consistent; and the height of the precipitation well (3) from the ground is consistent.

3. The well-pipe coordinated saline-alkali land improvement system according to claim 2, characterized in that: The precipitation well (3) is buried underground. Each precipitation well (3) is composed of a precipitation well support column (31) supporting a circumferentially arranged second filter layer (32). The precipitation well support column (31) is inserted into the ground. A precipitation well cover (33) is provided on the upper part of the precipitation well (3). The buried depth of the precipitation well cover (33) is greater than the depth of the water diversion trough (6). The coverage radius of the precipitation well cover (33) is greater than the radius of the second filter layer (32). A through hole is opened on the precipitation well cover (33). A vent pipe (34) is inserted into the through hole. The vent pipe (34) is located inside the precipitation well (3). The strong drainage well (2) is provided with a cover and a retractable pipe body; the upper part of the strong drainage well (2) is exposed outside the soil (1); each strong drainage well (2) is composed of a first filter layer (22) arranged circumferentially supported by a strong drainage well support column (21); the strong drainage well support column (21) is inserted into the ground; the outer periphery of the strong drainage well support column (21) exposed to the ground is prefabricated with permeable concrete; the upper part of the strong drainage well (2) is provided with a strong drainage well cover (23); the interior of the strong drainage well (2) is provided with a strong drainage pump (7); the water outlet of the strong drainage pump (7) is led out of the ground through a pipeline.

4. The well-pipe coordinated saline-alkali land improvement system according to claim 3, characterized in that: The strong drainage well (2) and the dewatering well (3) both have eight supporting columns, which are arranged in an array of equal arcs. The length of the part inserted into the underground is not less than 50 cm. A cross-shaped frame (8) is provided on the upper part of the strong drainage well (2) and the dewatering well (3), which abuts against the outer walls of the eight supporting columns. The eight branches of the cross-shaped frame (8) are composed of two solid pipes (81) with external threads and one threaded sleeve (82) with internal threads. The end of the threaded solid pipe (81) located on the outside is provided with an abutment joint (83). The abutment joint (83) is C-shaped and has a rubber layer on the outside. The length of a single drainage pipe (4) does not exceed 50 m. The distance between the pipe opening of the drainage pipe (4) and the bottom elevation of the dewatering well (3) is not less than 100 cm, and the distance between the pipe opening of the drainage pipe (4) and the bottom elevation of the strong drainage well (2) is not less than 250 cm.

5. The well-pipe coordinated saline-alkali land improvement system according to claim 4, characterized in that: The third filter layer (42) includes a third coarse sand layer (421), a third medium sand layer (422) and a third fine sand layer (423) arranged in sequence from the inside to the outside; the fourth filter layer (43) includes a fourth fine sand layer (431), a fourth medium sand layer (432) and a fourth coarse sand layer (433) arranged in sequence from the top to the bottom; the fifth filter layer (44) has the same structure as the fourth filter layer (43); the first filter layer (22) includes a first coarse sand layer (221), a first medium sand layer (222) and a first fine sand layer (223) arranged in sequence from the inside to the outside; the second filter layer (32) has the same structure as the first filter layer (22) except for the height difference; the sand of the filter layer is selected from the surface covering sand of the sand pressing land and is used in the filter layer after screening and classification.

6. The well-pipe coordinated saline-alkali land improvement system according to claim 5, characterized in that: The three layers of sand in the third filter layer (42) are all wrapped with geotextile to form a sand blanket, and are tied layer by layer to the outside of the corrugated pipe (41) with binding tape; the length of a single drainage pipe (4) is 15 to 20 meters in severe saline-alkali land, 20 to 30 meters in moderate saline-alkali land, and no more than 50 meters in mild saline-alkali land; the top of the precipitation well (3) is not less than 60 cm from the ground, the water diversion trough (6) is filled with a mixture of gravel and straw, the filling depth is not less than 20 cm, and the top of the water diversion trough (6) is not less than 40 cm from the ground.

7. The well-pipe coordinated saline-alkali land improvement system according to claim 6, characterized in that: A mud collecting trough (53) is provided at the bottom of the drainage ditch (5), a gravel layer (52) is provided on the left bank of the drainage ditch (5), a gabion cage (51) is provided outside the gravel layer (52), the thickness of the gravel layer (52) is 10 cm, the thickness of the gabion cage (51) is 30 cm, only the gabion cage (51) is provided on the right bank of the drainage ditch (5), the thickness of the gabion cage (51) is 30 cm, and ecological holes are also provided on the left bank of the drainage ditch (5).

8. The construction method of the well-pipe coordinated saline-alkali land improvement system according to any one of claims 1 to 7, characterized in that The steps include: S1. Soil chemical analysis and groundwater survey: Select the restoration area and divide it into multiple plots. Use the five-point sampling method to collect five soil columns from each plot. Test the soil salt content, salt composition, and soil particle size composition at different depths to determine the type and degree of salinization. Monitor the groundwater in the restoration area and analyze the groundwater quality and flow direction. S2. Land leveling and drainage ditch (5) excavation: dig drainage ditches vertically along the groundwater flow direction, and level the soil in the repair area to ensure that the land slope is consistent with the groundwater flow direction and the land slope meets 5‰ to 10‰; S3. Positioning, excavation and layout of forced drainage wells (2), dewatering wells (3) and drainage pipes (4): Design and excavate the spacing, number and depth of forced drainage wells (2) and dewatering wells (3) based on the type and degree of salinization and the area of ​​the repair area, and ensure that the length of a single drainage pipe (4) does not exceed 50m, the top of the dewatering well (3) is not less than 60cm from the ground, and all underground structures are arranged in a parallelogram in vertical space; after excavation, construct forced drainage wells (2), dewatering wells (3) and drainage pipes (4); S4, setting of the fourth inverted filter layer (43) and the fifth inverted filter layer (44): after the drainage pipe (4) is laid out, the position where the water diversion trough (6) needs to be laid out is determined. When backfilling the soil, the fourth inverted filter layer (43) is backfilled and set at the intersection of the vertical space of the water diversion trough (6) and the drainage pipe (4), and the fifth inverted filter layer (44) is backfilled and set at the intersection of the center line of two adjacent water diversion troughs (6) and the vertical space of the drainage pipe (4); S5, deep tillage and rotary plowing of the soil: after the soil backfill is completed, organic fertilizer is spread, and the thickness of the organic fertilizer is not less than 15 cm, and then deep tillage is performed. The depth of deep tillage and rotary plowing of the soil is preferably near the top of the fourth filter layer (43) and the fifth filter layer (44), so that the organic fertilizer is fully integrated with the soil; S6. Layout of water diversion trough (6): excavate the water diversion trough (6), fill the water diversion trough (6) with a mixture of gravel and straw, the filling depth of which is not less than 20 cm, and the top of the water diversion trough (6) is not less than 40 cm from the ground, and backfill with soil after filling; S7. Lining of the drainage ditch (5): lining the bottom of the drainage ditch (5) and the left and right banks of the drainage ditch (5).

9. The construction method of the well-pipe coordinated saline-alkali land improvement system according to claim 8, characterized in that The following steps are also included: S8. Setting of ridges: Before planting crops, set ridges on the soil surface. The direction of the ridges is consistent with the direction of the drainage ditch (5). The height of the ridges is 15 to 25 cm. One ridge is set every 5 meters. It must be set near the side of the strong drainage well (2) close to the drainage ditch (5).

10. The construction method of the well-pipe coordinated saline-alkali land improvement system according to any one of claims 9, characterized in that The steps include: S9, reconstruction of the water diversion trough (6): When the facility has been used for a certain number of years and the water diversion trough (6) is blocked, resulting in poor water diversion effect, the original water diversion trough (6) is abandoned, and a new water diversion trough (6) is excavated and set at the center line of two adjacent water diversion troughs (6), so that the new water diversion trough (6) is located on the upper part of the fifth filter layer (44).

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