Well pipe cooperative type saline-alkali soil improvement system and construction method thereof

Abstract

The invention discloses a well pipe cooperative saline-alkali soil improvement system and a construction method thereof, and belongs to the technical field of saline-alkali soil treatment. The system comprises a forced drainage well, a dewatering well and a drainage ditch, the forced drainage well and the dewatering well are arranged on a soil body, the drainage ditch is arranged in the vertical direction of underground runoff, the forced drainage well and the dewatering well are arranged in a grid node mode in the drainage direction and are communicated through a drainage pipe to form a well network, and the dewatering well drains water into the drainage ditch through the drainage pipe. When the underground water level rapidly rises, the underground water level rapidly falls back by pumping the water body of the forced drainage well, the water guide groove guides water and then filters the water to enter the drainage pipe, the filtering layer wrapping the drainage pipe reduces the amount of silt entering the pipe, and meanwhile the desilting effect of the dewatering well prevents the silt from depositing in the drainage pipe and blocking the drainage pipe during small water flow. And meanwhile, a standby fifth inverted filter layer is arranged, so that the service life of the facility is prolonged.

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 restricted the high-quality development of my country's agriculture, especially in the arid and semi-arid areas of the northwest, where the groundwater level is high and the evaporation is large, making soil salinization very likely to occur. The improvement of saline-alkali land usually adopts the method of lowering the groundwater level. The current commonly used drainage method is to lay underground pipes, collect water through the underground pipes, and discharge the water collected by the underground pipes into the drainage ditch. However, the drainage depth controlled by the underground pipes is constant. When the groundwater level rises rapidly, the drainage effect will be poor, resulting in secondary salinization. At the same time, underground pipe drainage often has the phenomenon of sediment blocking the underground pipes, and there is a lack of long-term mechanism to increase the service life of underground 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 in the precipitation well, and the forced drainage well is drained quickly. When the groundwater level rises rapidly, water is extracted from the forced drainage well 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 from being deposited in the drainage pipe during small water flow and clogging the drainage pipe. At the same time, a spare fifth anti-filtration 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] A well-pipe coordinated saline-alkali land improvement system, characterized in that it includes forced drainage wells and precipitation wells arranged on the soil body, and drainage ditches arranged vertically in the underground runoff, wherein the forced drainage wells and precipitation wells are arranged in a grid node manner along the drainage direction, and are connected through 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, and each drainage ditch controls no more than 3 rows of forced drainage wells, and a water diversion trough is arranged on the upper part of the drainage pipe in the vertical direction of the drainage ditch, and a fourth anti-filter layer abutting the drainage pipe is arranged downward from the water diversion trough at the intersection of the vertical space of the drainage pipe, and a fifth anti-filter layer abutting the drainage pipe at the bottom is arranged at the intersection of the center line of two adjacent water diversion troughs and the vertical space of the drainage pipe, and the drainage pipe is a corrugated pipe covered with holes, and the outside of the drainage pipe is wrapped with a third anti-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 heights of the forced drainage wells above the ground are consistent, and the heights of the precipitation wells from the ground are consistent.

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

[0009] The precipitation wells are buried underground, and each precipitation well is composed of a second filter layer arranged circumferentially supported by precipitation well support columns, the precipitation well support columns are inserted into the ground, a precipitation well cover is arranged 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, 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, 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 outside the soil body, and each forced drainage well is composed of a first filter layer arranged circumferentially 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, a forced drainage well cover is arranged on the upper part of the forced drainage well, a forced drainage pump is arranged inside the forced drainage well, and the water outlet of the forced drainage pump is led to the ground through a pipeline.

[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-arc circles, and the length of the underground part 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 casing 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 fifth filter layer has the same structure as 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 second filter layer has the same structure as the first filter layer except for the height inconsistency, and 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 of the third filter layer are all wrapped with geotextile to form a sand blanket, and are tied to the outside of the corrugated pipe layer by layer with binding tapes; the length of a single drainage pipe 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 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 arranged at the bottom of the drainage ditch, a gravel layer is arranged on the left bank of the drainage ditch, and gabion cages are arranged 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 arranged on the right bank of the drainage ditch. The left bank of the drainage ditch is also provided with ecological holes.

[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 5 soil columns in each plot to detect 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 are excavated vertically along the groundwater flow direction, and the soil in the restoration area is leveled to ensure that the land slope is consistent with the groundwater flow direction and the land slope meets 5‰~10‰;

[0021] S3. Location, excavation and layout of drainage wells, drainage wells and drainage pipes: Design and excavate the spacing, quantity and depth of drainage wells and drainage wells according to the type and degree of salinization and the area of ​​the restoration area, and ensure that the length of a single drainage pipe does not exceed 50m, the top of the drainage well is not less than 60cm from the ground, and all underground structures are arranged in a parallelogram in vertical space; after excavation, construct drainage wells, drainage wells and drainage pipes;

[0022] S4, setting of the fourth and fifth inverted filter layers: after the drainage pipe is laid, determine the location where the water diversion trough needs to be laid, and when backfilling the soil, first backfill and set the fourth inverted filter layer at the intersection of the water diversion trough and the vertical space of the drainage pipe, and backfill and set the fifth inverted filter layer at the intersection of the center line of two adjacent water diversion troughs and the vertical space of the drainage pipe;

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

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

[0025] S7. Drainage ditch lining: concrete lining is used for the bottom and mud trough of the drainage ditch, crushed stone layer and gabion stone cage is 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 is 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 channel: When the facility has been used for a certain number of years and the water diversion channel is blocked, resulting in poor water diversion effect, the original water diversion channel will be abandoned and a new water diversion channel will be excavated and set up on the center line of two adjacent water diversion channels, so that the new water diversion channel is located on the upper part of 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 through a water diversion trough, which improves the water collection effect. After the water is drawn, 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 part of the sediment entering the pipeline will also be precipitated through the precipitation well to prevent sediment from being deposited in the drainage pipe during small water flows. When the groundwater level rises rapidly, the water from the strong drainage well can be pumped to make the groundwater level fall rapidly. At the same time, the water pumped from the strong drainage well can be transported to the ventilation pipe to disturb the sediment deposited at the bottom of the precipitation well, so as to achieve the cleaning of 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 to extend the service life of the facility.

[0034] 2. In the present invention, the slope of the soil surface meets 5‰ to 10‰, and the slope direction is consistent with the groundwater flow direction. The appropriate slope is conducive to drainage, avoiding rainstorms in summer, which will cause 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, and does not cause congestion and retention, thereby improving the drainage effect.

[0035] 3. In the present invention, each precipitation well is composed of a second filter layer arranged in a circumference supported by a precipitation well support column. The same strong drainage well structure is similar. This type of arrangement in the gap of the support column is convenient for 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 greater than the radius of the second filter layer, 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. The outer part 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 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 can not only realize the storage of rainwater resources, but also reduce the concentration of underground saline-alkali water through fresh water, and accelerate the improvement of saline-alkali land. When silt 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, and the gravity potential energy of the water body accelerates infiltration, promoting salt drainage and water storage effects.

[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 ends of the threaded solid tubes located on the outside are provided with abutments. The abutments are C-shaped and have a rubber layer on the outside. Due to the inevitable errors in field construction, the length of the branches of the M-shaped frame can be adjusted by twisting the threaded sleeve with internal threads so that the abutments 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 sludge on the one hand, and can play a certain role in water storage on the other hand, laying the foundation for the development of saline-alkali fishery breeding (such as saline-alkali water crab breeding, etc.) in the drainage ditch in the later stage. A layer of waterproof cloth is set on the right bank. The setting 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 anti-filter layer is selected from the surface covering sand of the sand-pressing land, and is used for the anti-filter layer after screening and grading, realizing the comprehensive utilization of the sand of the depressurized sand field.

[0038] 6. The 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 It 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 It is a schematic diagram of the structure 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 strong 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 strong drainage well 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] Fig. 9 This is a schematic diagram of the M-shaped frame branch structure style of the present invention;

[0048] Fig.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. Strong drainage well; 21. Strong drainage well support column; 22. First filter layer; 221. First coarse sand layer; 222. First medium sand layer; 223. First fine sand layer; 23. Strong 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 .The third medium sand layer; 423. The third fine sand layer; 43. The fourth filter layer; 431. The fourth fine sand layer; 432. The fourth medium sand layer; 433. The fourth coarse sand layer; 44. The fifth filter layer; 441. The fifth fine sand layer; 442. The fifth medium sand layer; 443. The 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 casing; 83. Butt joint. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are 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 body 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 A in the figure, 12 precipitation wells 3 are arranged around each strong drainage well 2. The precipitation wells 3 discharge water into the drainage ditch 5 through the drainage pipe 4. The precipitation well 3 is used to deposit silt. Fine silt 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 blocked. Therefore, the precipitation well 3 is set to allow fine silt to settle without affecting drainage. When the silt accumulates to a certain extent, it can be discharged by flushing with large amounts of water. On the other hand, it serves to collect water and lower the groundwater level. The number of strong 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 the third row of strong drainage wells 2, and only precipitation wells 3 are required. Please refer to Figure 2 , a water diversion trough 6 is arranged at the upper part of the drainage pipe 4 in the vertical direction along the drainage ditch 5. The function of the water diversion trough is to guide water so that the water body can gather at the upper part of the drainage pipe 4 and then seep into the drainage pipe 4. A fourth filter layer 43 is arranged downward from the water diversion trough 6 to abut against the drainage pipe 4 at the intersection of the vertical space of the water diversion trough 6 and the drainage pipe 4. The setting of the filter layer can make the water body directly reach the water diversion trough 6, while weakening the soil obstruction and preventing more fine particles of soil from entering the drainage pipe 4. A fifth filter layer 44 is arranged at the intersection of the center line of the two adjacent water diversion troughs 6 and the vertical space of the drainage pipe 4, and the lower part abuts against the drainage pipe 4. The purpose of the fifth filter layer 44 is to play a backup role. As the operation time increases, the water diversion trough 6 and the fourth filter layer 43 will inevitably be blocked. If a new filter layer is set, the cost will increase and the construction will be difficult. Therefore, a spare fifth filter layer 44 is set. When blockage occurs, it is only necessary to reset 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 3The drainage pipe 4 is a corrugated pipe 41 full of holes. The corrugated pipe 41 has good pressure resistance and will not be flattened. The outside of the drainage pipe 4 is wrapped with a third filter layer 42. The third filter layer 42 is directly wrapped on the outside of the corrugated pipe 41, which can further isolate the sediment and reduce the amount of sediment entering the pipe. Small particles with a particle content of less than 5% and a particle size of less than 0.1 mm are allowed to be carried away by seepage, which does not affect the stability of the soil skeleton, but must not block the pores of the filter layer. The drainage pipe 4 is provided with a solenoid valve 45 at the outlet of the drainage ditch 5, which can realize controlled drainage and adjust 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 is conducive to drainage, avoiding rainstorms in summer, causing soil erosion and soil loss. At the same time, the slope should not be too large, which will lead to a large amount of water loss and fail to achieve the effect of infiltration and alkali drainage. The slope is satisfied by leveling; the slope and slope direction of the water diversion trough 6 are consistent with the surface 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 are consistent, the specifications of 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 the 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 4 always maintains a relatively stable slope, and does not cause congestion and retention.

[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 is convenient for 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, in which a vent pipe 34 is inserted. The part of the vent pipe 34 located inside the precipitation well 3 is covered with holes, and the part of the vent pipe 34 located outside the precipitation well 3 is a retractable tube body with a cover. During daily use, the cover is opened, and the vent pipe 34 produces ventilation to avoid negative pressure and hinder drainage. When tillage 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 an appropriate depth below the ground. If a corrugated retractable tube is used, it can be contracted by pressing down to avoid affecting tillage such as mechanical harvesting, rotary tillage, etc. It can be dug out or flushed out after tillage is completed. When there is a lot of silt deposited inside the precipitation well 3, when the groundwater level is high or the drainage pipe 4 has a large discharge volume, the water in the forced drainage well 2 can be extracted and connected to the ventilation pipe 34 to act as a water supply disturbance, so that the silt deposited at the bottom is stirred into mud, which is flushed out into the drainage ditch 5 with the large water flow, thereby flushing the precipitation well 3.

[0055] The upper part of the strong drainage well 2 is exposed outside the soil body 1. Each strong drainage well 2 is composed of a first anti-filter layer 22 arranged in a circumference supported by a strong drainage well support column 21. The strong drainage well support column 21 is inserted into the ground. The outer part 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 strong drainage well 2 is arranged with a strong drainage pump 7. The outlet of the strong drainage pump 7 is led out of the ground through a pipeline. The strong drainage well 2 has the same structure and function as the precipitation well 3. The prefabricated concrete is permeable concrete, which can prevent the surface runoff from directly entering the strong drainage well 2 and filtering through the permeable concrete. When heavy rainfall occurs, the alkaline water in the strong drainage well 2 can be discharged in advance and infiltrated with fresh water or slightly brackish water, which can not only realize the storage of rainwater resources, but also reduce the concentration of underground saline-alkali water through fresh water, and accelerate the improvement of saline-alkali land. When silt is deposited at the bottom of the strong drainage well 2, it can be directly extracted from the well in the form of mud through the disturbance of the strong drainage pump 7, so that the cleaning of the strong drainage well 2 is realized.

[0056] In the embodiment of the present invention, the strong drainage well 2 and the precipitation well 3 both have 8 supporting columns, which are arranged in an equal-arc circular array with 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 supporting columns are customized in advance, the length of the underground insertion in the same repair area is consistent, thereby ensuring that the relative positions of the structures remain unchanged. A cross-shaped frame 8 is provided on the upper part of the strong drainage well 2 and the precipitation well 3, which abuts against the outer walls of the 8 supporting columns. The 8 branches of the cross-shaped frame 8 are composed of 2 solid pipes 81 with external threads and 1 threaded sleeve 82 with internal threads. An abutment joint 83 is provided at the end of the threaded solid pipe 81 located on the outside. The abutment joint 83 is C-shaped and has a rubber layer on the outside. Due to the inevitable errors in field construction, the length of the branch of the cross-shaped frame 8 is adjusted by twisting the threaded sleeve 82 with internal threads, so that the abutment joint 83 can fully contact the support column. The length of a single drainage pipe 4 does not exceed 50m. The length of a single drainage pipe 4 is 15-20m in severe saline-alkali land, 20-30m in moderate saline-alkali land, and does not exceed 50m in mild saline-alkali land. The actual adjustment is made according to the type of saline-alkali land and the area of ​​the region, in order to ensure the repair effect and reduce the engineering investment. The distance between the outlet of the drainage pipe 4 and the bottom elevation of the precipitation well 3 is not less than 100cm, and the distance from the bottom elevation of the strong drainage well 2 is not less than 250cm. Sufficient space is reserved, which not only improves the precipitation effect, but also provides sufficient 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 wrapped with geotextiles to form a sand blanket, and are tied layer by layer on the outside of the corrugated pipe 41 with binding tapes, 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 completely consistent with 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 completely consistent with the first filter layer 22 except that the height is different. 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, thereby realizing the reuse of sand in the depressurized sand field and helping to protect the ecological environment. The side of the filter layer in contact with the soil is all fine sand, the main purpose of which is to prevent a large amount of fine particles in the soil from entering the pipeline and maintain the stability of the soil structure skeleton. The top of the precipitation well 3 is not less than 60 cm from the ground, so that it is guaranteed to be below the root layer of most crops. 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, which not only ensures drainage, but also ensures that daily rotary tillage will not damage it, and also ensures that the straw is decomposed to increase organic matter in the soil. Gravel is also preferably covered with sand and gravel on the surface of the sand-pressed land.

[0058] In the embodiment of the present invention, please refer to Fig.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 outside the gravel layer 52, the thickness of the gravel layer 52 is 10cm, the thickness of the gabion gabion cage 51 is 30cm, 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 30cm, and the left bank of the drainage ditch 5 is also provided with ecological holes. The depth of the excavation of the drainage ditch 5 should be deep to meet the drainage requirements. Among them, 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, and the buried depth of the waterproof cloth is greater than the depth of the drainage ditch 5, at least extending more than 100cm 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, resulting in its loss of drainage effect. For areas with soft soil and prone to collapse, the left bank of the drainage ditch 5 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 the drainage ditch 5 and the mud collecting trough 53 are lined with concrete. The lower part of the mud collecting trough 53 is a standard rectangle. The concrete lining is conducive to mechanical cleaning of silt on the one hand, and can play a certain role in water storage on the other hand, laying a foundation for the development of saline-alkali fishery breeding (such as saline-alkali water crab breeding, etc.) in the drainage ditch 5 in the later stage. Ecological holes are reserved during the lining to facilitate the habitat of aquatic organisms.

[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 the restoration area and use drone hyperspectral to make preliminary identification and division of the degree of saline-alkali land. Drone hyperspectral is a mature technology and will not be described in detail here. According to the preliminary division results of hyperspectral, follow the principle of proximity and divide the saline-alkali land of the same type into the same area as much as possible. After the preliminary division, five soil columns are collected from each plot using the five-point sampling method. The soil column is preferably 100 cm, and each 20 cm is divided into a sample to detect the salt content, salt composition and soil particle size composition of soil at different depths. Further judgment of saline-alkali land is made to avoid the disadvantage that hyperspectral inversion can only reflect the surface layer, so that the classification of saline-alkali land types is more accurate and its type is further verified. At the same time, monitor the groundwater in the study area and analyze the groundwater quality and flow direction. According to the groundwater flow direction, water quality and the type of saline-alkali land after verification, the empirical method, expert demonstration method or other mathematical models that can be found in the literature are used to design the project overview and specific parameters. Generally, it is required that each drainage ditch 5 control no more than 3 rows of strong drainage wells 2, and 2 rows are appropriate.

[0061] S2. Land leveling and drainage ditch 5 excavation: Use a bulldozer or rotary tiller to level the soil surface in the repair area according to the actual ground flatness, ensure that the land slope is consistent with the groundwater flow direction, and the land slope meets 5‰~10‰. The appropriate slope is conducive to drainage, avoiding summer rainstorms that cause rain and floods, soil erosion and soil erosion. At the same time, the slope should not be too large, which will cause a large amount of water loss and fail to achieve the effect of infiltration and alkali drainage. The water body will eventually be discharged into the drainage ditch 5, so it is necessary to excavate the drainage ditch 5. The vertical excavation of the groundwater flow direction is delayed during the excavation to intercept the groundwater. The depth of the drainage ditch 5 excavation should be deep to meet the drainage requirements. 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 to the lower part of the drainage ditch 5 by more than 100 cm. 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 field. After that, backfilling is carried out to form a trapezoid. A mud collecting trough 53 should be excavated at the bottom of the drainage ditch 5. Since some fine-grained soil will be carried when draining water, it will accumulate in the ditch for a long time. The mud collecting trough 53 is set to facilitate mechanical equipment to remove it.

[0062] S3. Positioning, excavation and layout of forced drainage well 2, precipitation well 3 and drainage pipe 4: Design and excavate the spacing, quantity and depth of forced drainage well 2 and precipitation well 3 according to the type and degree of salinization and the area of ​​restoration, 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 and obstruction of rotary tillage. 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 precipitation well 3 are consistent, the height of the forced drainage well 2 above the ground is consistent, the distance from the bottom to the ground is consistent, the height from the upper part of the precipitation well 3 to the ground is consistent, and the height from the lower part to the ground is consistent; an excavator is used to dig the trenches of the forced drainage well 2 and the precipitation well 3. During excavation, try to dig into cylindrical trenches to reduce the workload of subsequent filling. A trencher is used to dig the buried trench of the drainage pipe 4 to connect it with the trenches of the forced drainage well 2 and the precipitation well 3. Then, the construction of the forced drainage well 2, the precipitation well 3 and the drainage pipe 4 is carried out. During the construction of the strong drainage well 2 and the precipitation well 3, the precipitation well support column 31 and the strong 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 equal arc circular array. 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 eight support columns. The abutment joint 83 is C-shaped and is provided with a rubber layer on the outside. Due to the inevitable errors in field construction, the branch length of the M-shaped frame 8 is adjusted by twisting the threaded sleeve 82 with an internal thread, so that the abutment joint 83 can fully contact 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 with the corrugated pipe 41 with a tying belt. The thickness of each layer is not less than 5 cm, and 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 plate is processed into a C-shape of different specifications, and 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. After backfilling, compaction is carried out to avoid excessive subsequent collapse. If the well slot is opened larger, the outside of the fine sand layer is backfilled with soil. After the backfilling is completed, the C-shaped steel plate is pulled out and used for upper backfilling or reused in other wells. The purpose of the C-shape is to avoid the influence of the arranged drainage pipe 4 on the backfilling, 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 ventilation pipe 34 is inserted into the through hole opened on the precipitation well cover 33. The ventilation 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 at 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 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 can not only save rainwater resources, but also reduce the concentration of underground saline-alkali water through fresh water, thereby accelerating the improvement of saline-alkali land.

[0065] S4, setting of the fourth inverting filter layer 43 and the fifth inverting 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 inverting 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 inverting 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 PVC thick pipe, put it in the position where the fourth inverting filter layer 43 and the fifth inverting 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 PVC thick pipe is pulled out for other uses.

[0066] S5. Deep tillage and soil plowing: After the soil is backfilled, organic fertilizer is spread. The organic fertilizer is fermented chicken manure, cow manure, sheep manure, crop straw, etc. The thickness of the organic fertilizer is not less than 15 cm. Then deep tillage is performed. The depth of deep tillage and soil plowing is preferably near the top of the fourth filter layer 43 and the fifth filter layer 44, so that the organic fertilizer and the soil are fully integrated. At the same time, avoid damaging the filter layer due to deep tillage, 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, drainage ditch 5 is lined. The purpose of slope protection is to facilitate the maintenance of drainage ditch 5 in the later stage, and to avoid soil collapse after long-term use, which causes it to lose its drainage function. On the left bank of drainage ditch 5, gravel layer 52 is set, and gabion gabion cage 51 is set outside of gravel layer 52. The thickness of gravel layer 52 is about 10cm, and the thickness of gabion gabion cage 51 is about 30cm. Only gabion gabion cage 51 is set on the right bank of drainage ditch 5, and the thickness of gabion gabion cage 51 is about 30cm. For areas with soft soil and easy collapse, anchor rods need to be set on the left bank of drainage ditch 5, and the height of lining is about 10cm 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 breeding (such as saline-alkali water crab breeding, etc.) in drainage ditch 5 in the later stage. If necessary, ecological holes should be reserved during the 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 and the salt content of the soil in the cultivated layer can be greatly reduced. 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 on 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, the soil is backfilled. This arrangement increases the use time of the facility and reduces the subsequent operation and maintenance costs.

[0072] In the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance; the term "plurality" refers to two or more, unless otherwise clearly defined. The terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0073] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope 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 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 the number of forced drainage wells (2) controlled by each drainage ditch (5) does not exceed 3 rows, and the drainage pipe (4) is 120 mm / s. A water diversion groove (6) is arranged at the upper part in the vertical direction of the drainage ditch (5); a fourth filter layer (43) is arranged downward from the water diversion groove (6) and abuts against the drainage pipe (4) at the intersection of the vertical space of the water diversion groove (6) and the drainage pipe (4); a fifth filter layer (44) is arranged at the intersection of the center line of two adjacent water diversion grooves (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 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 body (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 body (1); the drainage pipe (4) is consistent with the surface slope of the soil body (1) in the direction of the soil body (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) 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 arranged 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 ventilation pipe (34) is inserted into the through hole. The ventilation 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 body (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 part of the strong drainage well support column (21) exposed above 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 drainage well (3) each have eight supporting columns arranged in an array of equal arc circles, and 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 drainage well (3), which is abutted 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), which is C-shaped and has a rubber layer on the outside. The length of a single drainage pipe (4) does not exceed 50 m, and the distance between the pipe opening of the drainage pipe (4) and the bottom elevation of the drainage 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) comprises 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) comprises 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) is completely consistent with the structure of the fourth filter layer (43); the first filter layer (22) comprises 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 completely consistent with the first filter layer (22) in structure 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 for the filter layer after screening and grading.

6. The well-pipe coordinated saline-alkali land improvement system according to claim 5, characterized in that: The three layers of sand of 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 arranged at the bottom of the drainage ditch (5), a gravel layer (52) is arranged on the left bank of the drainage ditch (5), a gabion cage (51) is arranged 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 arranged on the right bank of the drainage ditch (5), the thickness of the gabion cage (51) is 30 cm, and ecological holes are also arranged 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 5 soil columns in each plot to detect 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 excavation (5): Drainage ditches are excavated vertically along the groundwater flow direction, and the soil in the restoration area is leveled to ensure that the land slope is consistent with the groundwater flow direction and the land slope meets the requirement of 5‰ to 10‰; S3. Location, excavation and layout of the forced drainage well (2), the precipitation well (3) and the drainage pipe (4): The spacing, number and depth of the forced drainage well (2) and the precipitation well (3) are designed and excavated according to the type and degree of salinization and the area of ​​the restoration area, and it is ensured that the length of a single drainage pipe (4) does not exceed 50m, the top of the precipitation well (3) is not less than 60cm from the ground, and all underground structures are arranged in a parallelogram in vertical space layout; after excavation, the forced drainage well (2), the precipitation well (3) and the drainage pipe (4) are constructed; S4, setting of the fourth inverting filter layer (43) and the fifth inverting 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, and when backfilling the soil, the fourth inverting 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 inverting 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 cultivation of the soil: after the soil is backfilled, organic fertilizer is spread, the thickness of which is not less than 15 cm, and then deep tillage is performed. The depth of deep tillage and rotary cultivation 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 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 or so. 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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