Mouse path and underground pipe interface structure for low permeability black soil farmland and construction method thereof

Abstract

This invention discloses a rat tunnel and culvert interface structure for low-permeability black soil farmland, belonging to the field of farmland drainage and soil moisture regulation technology. The aim is to solve the problems of easy collapse, blockage, and maintenance difficulties at the connection points of existing rat tunnels and culverts. The key to this technical solution is that it includes a rat tunnel guide section and a transition connection cavity connected to the rat tunnel guide section. The cross-sectional area of ​​the inlet end of the transition connection cavity is smaller than that of the outlet end. The transition connection cavity has an anti-collapse support frame inside, a sediment collection chamber at the bottom, and a filter layer on the outside. The rat tunnel guide section and the transition connection cavity are connected by a flexible pipe sleeve. It also includes a backwash pipe connected to the transition connection cavity and the culvert access section, and a drainage control section located downstream of the main culvert. This invention is mainly used in drainage systems for low-permeability black soil farmland, effectively preventing interface collapse and sediment blockage, simplifying maintenance operations, and enabling flexible control of drainage intensity.

Description

Technical Field

[0001] This invention relates to the field of farmland drainage and soil moisture regulation. More specifically, this invention relates to a rat tunnel and culvert interface structure for low-permeability black soil farmland and its construction method. Background Technology

[0002] In low-permeability black soil farmland areas, especially in low-lying plains with high groundwater levels and distinct plow pans, soil moisture infiltrates slowly after rain, while shallow groundwater rises rapidly, easily leading to continuous stress from surface water accumulation and topsoil waterlogging.

[0003] To improve drainage in such farmland, existing technologies often employ a combination of rat tunnels and underground pipes. The rat tunnels quickly collect shallow, stagnant water and guide it into the underground pipe system for discharge. However, current rat tunnel and underground pipe connections are mostly simple, rigid direct connections, lacking specialized design for the interface area. This traditional connection structure is highly susceptible to collapse, misalignment, and localized erosion at the interface between the rat tunnel and the underground pipe under the influence of water erosion, soil expansion and contraction, and freeze-thaw cycles, leading to drainage channel interruption or failure. Simultaneously, silt, straw debris, and other impurities carried by the water flow accumulate at the interface, causing blockages and significantly reducing drainage efficiency. Furthermore, subsequent maintenance requires extensive excavation of the interface area, resulting in high maintenance costs. In addition, existing interface structures struggle to simultaneously meet the needs of rapid drainage after heavy rains and maintaining target groundwater levels during the crop's growth period.

[0004] Therefore, there is an urgent need to provide a special interface structure for rat tunnels and underground pipes that can effectively balance flow stabilization, sedimentation, anti-clogging, anti-collapse, and maintainability, and achieve flexible control of drainage intensity. Summary of the Invention

[0005] One object of the present invention is to provide a rat tunnel and underground pipe interface structure for low-permeability black soil farmland, comprising: Rat tunnel guide section; The transition connection cavity has an inlet end and an outlet end, the inlet end being connected to the mouse channel guide section, and the cross-sectional area of ​​the inlet end of the transition connection cavity being smaller than the cross-sectional area of ​​the outlet end of the transition connection cavity. The concealed pipe access section has one end connected to the outlet end of the transition connection cavity, and the other end of the concealed pipe access section is connected to the main concealed pipe. A flexible sleeve is fitted at the connection between the rat passage guide section and the inlet end of the transition connection cavity; An anti-collapse support frame is disposed inside the transition connection cavity; A sedimentation chamber is located at the bottom of the transition connection cavity, and the bottom surface of the sedimentation chamber is lower than the bottom surface of the end of the underground pipe connection section that communicates with the transition connection cavity. The filter layer includes a first filter section covering the periphery of the transition connection cavity and a second filter section covering the periphery of the concealed pipe inlet section; A backflushing pipe, the opening of which is connected to the inner cavity of the transition connection cavity and / or the inner cavity of the concealed pipe access section; The control and discharge section is located downstream of the main concealed pipe.

[0006] Preferably, the flexible sleeve is a self-locking composite sleeve, which includes: The inner elastic sealing body is in contact with the outer wall of the rat passage guide section and the transition connection cavity; A shape memory alloy woven mesh is wrapped around the outer surface of the inner elastic seal. The shape memory alloy woven mesh shrinks and deforms under preset temperature or stress conditions, and applies a radial clamping force to the inner elastic seal.

[0007] Preferably, the material of the shape memory alloy woven mesh is a two-way shape memory alloy, which is in a relaxed state at a first temperature below the normal soil temperature and in a contracted state at a second temperature within the normal soil temperature range.

[0008] Preferably, the inner wall of the transition connection cavity is provided with a spiral guide groove, the spiral guide groove extends spirally along the inner wall of the transition connection cavity, the inner wall of the spiral guide groove is fixedly connected to the outer wall of the anti-collapse support frame, the end of the spiral guide groove is connected to the inlet of the sedimentation chamber, and the spiral angle of the spiral guide groove gradually decreases along the water flow direction.

[0009] Preferably, the inner wall of the transition connection cavity is provided with a plurality of hemispherical micro-protrusions on the bottom or side wall of the spiral guide groove.

[0010] Preferably, it also includes an in-situ soil solidification anchoring ring, which is disposed on the outer periphery of the transition connection cavity and / or the outer periphery of the culvert access section, and is located outside the filter layer.

[0011] Preferably, the in-situ soil solidification anchoring ring is a hollow annular structure filled with a curing agent, and the ring wall of the in-situ soil solidification anchoring ring is provided with multiple grouting holes facing the surrounding soil.

[0012] Preferably, it also includes a maintenance observation port located above the transition connection cavity.

[0013] Preferably, the drainage control section is a drainage control well, the downstream end of the main underground pipe extends into the drainage control well, and the drainage control well is provided with at least one adjustable weir plate, which divides the inner cavity of the drainage control well into an upstream chamber and a downstream chamber.

[0014] A construction method for forming the interface structure between the rat tunnel and the concealed pipe is provided, comprising the following steps: S1. Determine the location of the rodent tunnel drainage section and the main underground pipe according to the field slope and drainage requirements; S2. Install a transition connection cavity at the end of the rat tunnel to ensure that the cross-sectional area of ​​its inlet end is smaller than the cross-sectional area of ​​its outlet end; S3. Install a flexible tube sleeve in the form of a self-locking composite sleeve at the connection between the rat passage guide section and the transition connection cavity; S4. Connect the rear end of the transition connection cavity to the main concealed pipe through the concealed pipe access section, and set a filter layer; S5. On the outer periphery of the transition connection cavity and / or the underground pipe access section, electrodes and biodegradable conductive fiber mesh are set, and curing agent slurry is injected into the surrounding soil. Then, an electric field is applied through the electrodes to make the curing agent slurry diffuse into the surrounding soil and drain the water, forming an in-situ soil curing anchor ring. S6. Install a backflushing and unclogging branch pipe, the pipe opening of which is connected to the inner cavity of the transition connection cavity and / or the inner cavity of the concealed pipe access section; S7. Connect the downstream of the main underground pipe to the drainage control unit, wherein the drainage control unit is a drainage control well and is provided with at least one adjustable weir plate. S8. After completing the above installation steps, perform layered backfilling and compaction, and conduct water flow tests and controlled drainage mode adjustments. The present invention has at least the following beneficial effects: First, the present invention provides an anti-collapse support frame that is fixedly connected to the inner wall of the spiral guide channel inside the transition connection cavity, and a flexible sleeve is provided between the rat tunnel guide section and the transition connection cavity. This structure can effectively withstand the sinking pressure and backfill pressure of the soil around the interface area, and adapt to the displacement deformation caused by uneven soil settlement and freeze-thaw, thereby reducing the risk of collapse at the end of the rat tunnel, misalignment of the interface and local scour instability.

[0015] Secondly, by designing the cross-sectional area of ​​the inlet end of the transition connection cavity to be smaller than that of the outlet end, the present invention forms a gradually expanding deceleration space, and sets a sedimentation chamber at its bottom with the bottom surface of the chamber being lower than that of the underground pipe access section. Combined with the filter layer covering the transition connection cavity and the periphery of the underground pipe access section, this structure can slow down the water flow, promote the deposition of large particles of sediment in the sedimentation chamber, and grade and intercept coarse particles of sediment, roots and straw debris, reducing the possibility of sediment and impurities entering the main underground pipe.

[0016] Third, by setting up a backwash pipe that connects to the transition connection cavity and the inner cavity of the underground pipe access section, when the interface becomes blocked, high-pressure water or air-water mixture can be injected into the interface from the ground surface through the backwash pipe for reverse flushing without large-area excavation, thereby restoring the water passage capacity and reducing maintenance difficulty and cost.

[0017] Fourth, by setting a control and discharge section downstream of the main underground pipe, the present invention can adjust the outflow elevation and drainage intensity of the underground pipe, so that the interface structure can take into account the different needs of rapid drainage after heavy rain and maintaining the target groundwater level during the crop growth period.

[0018] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0019] Figure 1 This is a longitudinal sectional view of the overall structure of the mouse tunnel and the dark pipe interface structure according to one of the technical solutions of the present invention. Figure 2 This is an enlarged cross-sectional view of the transition connection cavity according to one of the technical solutions of the present invention; Figure 3 for Figure 2 Cross-sectional view of AA; Figure 4 This is a partially enlarged cross-sectional view of the flexible sleeve according to one of the technical solutions of the present invention; Figure 5 This is a cross-sectional view of the controlled drainage well according to one of the technical solutions of the present invention.

[0020] The markings in each of the attached figures are as follows: 1. Rat tunnel guide section; 2. Transition connection cavity; 21. Inlet end; 22. Outlet end; 23. Spiral guide channel; 24. Micro-protrusion; 25. Sediment collection and sedimentation bin; 26. Anti-collapse support skeleton; 3. Underground pipe access section; 31. Variable diameter pipe; 4. Main underground pipe; 5. Flexible pipe sleeve; 51. Inner elastic sealing body; 52. Shape memory alloy braided mesh; 6. First filter section; 7. Second filter section; 61. Inner rigid porous support component; 62. Outer permeable filter layer; 8. Backwash pipe; 9. Controlled discharge well; 91. Adjustable weir plate; 10. In-situ soil solidification anchoring ring; 11. Inspection and observation port. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0022] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this invention, the orientation or positional relationship indicated by the terms is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0023] like Figures 1-5 As shown, the present invention provides a rat tunnel and underground pipe interface structure for low-permeability black soil farmland, comprising: Rat tunnel guide section 1; Specifically, the rat tunnel guide section 1 is located in the lower part of the tillage layer or near the plow layer, and its depth can be selected from 0.40 m to 0.70 m. Its spacing can be selected from 2 m to 6 m. It is used to collect the stagnant water in the upper part of the tillage layer and guide it to the interface structure. The transition connection cavity 2 has an inlet end 21 and an outlet end 22. The inlet end 21 is connected to the rat passage guide section 1. The cross-sectional area of ​​the inlet end 21 of the transition connection cavity 2 is smaller than the cross-sectional area of ​​the outlet end 22 of the transition connection cavity 2. Specifically, the diameter of the inlet end 21 of the transition connection cavity 2 can be 1.0 to 1.5 times the diameter of the rat passage guide section 1, and the diameter of the outlet end 22 can be 1.2 to 2.0 times the diameter of the inlet end 21, thereby forming a gradually expanding deceleration space along the water flow direction to reduce the incoming flow velocity and reduce the local scouring of the interface. The concealed pipe access section 3 has one end connected to the outlet end 22 of the transition connection cavity 2, and the other end of the concealed pipe access section 3 is connected to the main concealed pipe 4. Specifically, one end of the concealed pipe access section 3 is connected to the outlet end 22 of the transition connection cavity 2 by a socket connection and sealed with a sealing ring, and the other end is connected to the main concealed pipe 4 through a reducing pipe 31, which is used to introduce water into the main concealed pipe 4. The flexible sleeve 5 is fitted at the connection between the rat passage guide section 1 and the inlet end 21 of the transition connection cavity 2. Specifically, the flexible sleeve 5 can be a silicone rubber sleeve or an EPDM rubber sleeve. The flexible sleeve 5 is tightly fitted at the connection between the outer wall of the end of the rat passage guide section 1 and the outer wall of the inlet end 21 of the transition connection cavity 2. During installation, after the two pipe ends are joined, the flexible sleeve 5 is moved first to cover the joint, and then a stainless steel hose clamp is used on each of its two outer ends for radial locking in order to adapt to displacement deformation under wet expansion and dry contraction and micro-settlement conditions. The anti-collapse support frame 26 is located inside the transition connection cavity 2. Specifically, the anti-collapse support frame 26 can be a cage-type grid structure or a ring-shaped frame. Its outer wall is rigidly fixed to the inner wall of the transition connection cavity 2 through multiple evenly distributed welding points or buckles. It is used to effectively withstand the collapsibility pressure and backfill pressure of the surrounding soil and prevent the interface area from collapsing under high moisture content. The sedimentation chamber 25 is located at the bottom of the transition connection cavity 2, and the bottom surface of the sedimentation chamber 25 is lower than the bottom surface of the end of the underground pipe inlet section 3 that communicates with the transition connection cavity 2. Specifically, the sedimentation chamber 25 is a groove formed by the downward indentation of the inner wall of the bottom of the cavity, and its bottom surface is lower than the bottom surface of the inlet of the underground pipe inlet section 3. This height difference can be selected from 5 cm to 20 cm, and is used to collect sediment and larger particulate impurities carried in the water flow. The filter layer includes a first filter section 6 covering the periphery of the transition connection cavity 2 and a second filter section 7 covering the periphery of the underground pipe access section 3. Specifically, the first filter section 6 and the second filter section 7 are structurally identical. Each filter section adopts a sleeve-type composite structure consisting of an inner rigid porous support member 61 and an outer permeable filter layer 62 from the inside out. The inner rigid porous support member 61 can be a perforated plastic sleeve, and the outer permeable filter layer 62 can be a geotextile. During installation, the inner support member is first used to form an axial limit with the outer wall of the cavity through the clamping platform at its end. Then, the outer filter layer is tightly tied to its outside with a corrosion-resistant braided rope for graded interception of coarse particles of mud and sand, roots and straw debris. The backwash pipe 8 has its port connected to the inner cavity of the transition connection cavity 2 and / or the inner cavity of the concealed pipe access section 3. Specifically, the port of the backwash pipe 8 is inserted from the outside and is connected to the upper side wall of the transition connection cavity 2 and the upper side wall of the concealed pipe access section 3. A sealing gasket and a locking nut are used for waterproof sealing at the penetration point. Its outer end extends to the ground surface and is equipped with a removable cover and valve for connecting to an external high-pressure water source or air source for backwashing when the interface is blocked. The control and discharge section is located downstream of the main underground pipe 4. Specifically, the control and discharge section is reliably connected to the downstream end of the main underground pipe 4 through a reducing pipe 31, and is used to adjust the outflow elevation and drainage intensity of the underground pipe.

[0024] In the above technical solution, the working process of the rat tunnel and culvert interface structure for low-permeability black soil farmland is as follows: First, the stagnant water in the cultivated layer is collected through the rat tunnel drainage section 1. After the water flows into the transition connection cavity 2, it slows down due to the expansion of the cross-section. Large particles of silt are deposited in the sedimentation chamber 25. The cleaner water is filtered through the filter layer and enters the culvert access section 3 and the main culvert 4, and is discharged from the downstream control drainage section. During this process, the anti-collapse support frame 26 ensures that the transition connection cavity 2 does not collapse. During the normal growth period, the outflow elevation can be adjusted by the control drainage section to maintain the target groundwater depth. When the interface area is blocked, it can be flushed in reverse through the backwash pipe 8 or cleared by mechanical cleaning rod, thereby restoring the water flow capacity.

[0025] In another technical solution, the flexible sleeve 5 is a self-locking composite sleeve, which includes: The inner elastic sealing body 51 is attached to the outer wall of the rat passage guide section 1 and the transition connection cavity 2. Specifically, the inner elastic sealing body 51 can be made of highly elastic neoprene rubber or silicone rubber, and its inner wall is directly attached to the outer wall of the rat passage guide section 1 and the transition connection cavity 2 to form the first seal. A shape memory alloy braided mesh 52 covers the outer surface of the inner elastic sealing body 51. The shape memory alloy braided mesh 52 shrinks and deforms under preset temperature or stress conditions, and applies radial clamping force to the inner elastic sealing body 51. Specifically, the shape memory alloy braided mesh 52 can be woven from nickel-titanium shape memory alloy wires and tightly covers the outer surface of the inner elastic sealing body 51. The bidirectional shape memory alloy has specific phase change temperature characteristics: it is in a relaxed state at the first temperature of 0°C to 5°C, at which time the inner diameter of the sleeve expands, making it easy to fit onto the interface connection in a low-temperature environment; when the ambient temperature rises to the second temperature of 15°C to 25°C (i.e., normal soil temperature), the shape memory alloy wires are excited by heat and undergo a phase change, automatically switching to a contracted state and maintaining this state to continuously apply radial clamping force, achieving a self-locking seal without manual intervention. This design can automatically adapt to uneven soil settlement and displacement deformation caused by freeze-thaw cycles, maintaining interface sealing and continuous flow.

[0026] In another technical solution, the shape memory alloy braided mesh 52 is made of a bidirectional shape memory alloy, which is in a relaxed state at a first temperature below the ambient soil temperature and in a contracted state at a second temperature within the ambient soil temperature range. Specifically, the bidirectional shape memory alloy is in a relaxed state at the first temperature of 0°C to 5°C, making it easy to easily slip the self-locking composite sleeve onto the interface connection in a low-temperature environment (or through simple cooling measures). At the second temperature of 15°C to 25°C (i.e., ambient soil temperature), it automatically switches to the contracted state and maintains this state to continuously apply radial clamping force. When it is necessary to disassemble or replace the composite sleeve, it can be cooled to the first temperature, at which point the shape memory alloy braided mesh 52 will return to the relaxed state, making it easy to remove from the interface. This design greatly facilitates the later maintenance, repair, and replacement of the interface structure.

[0027] In another technical solution, the inner wall of the transition connection cavity 2 is provided with a spiral guide groove 23. The spiral guide groove 23 extends spirally along the inner wall of the transition connection cavity 2. The inner wall of the spiral guide groove 23 is fixedly connected to the outer wall of the anti-collapse support frame 26. The end of the spiral guide groove 23 is connected to the inlet of the sedimentation chamber 25. The spiral angle of the spiral guide groove 23 gradually decreases along the water flow direction. Specifically, the spiral angle of the spiral guide groove 23 can be designed to gradually decrease along the water flow direction, with the inlet... The spiral angle can be 45°, and the spiral angle at the outlet can be reduced to 15°. Its inner wall is rigidly fixed to the outer wall of the anti-collapse support frame 26 through multiple evenly distributed welding points or buckles. Its end opening is directly connected to the inlet of the sedimentation chamber 25. When the water flows in, it generates a rotational motion under the guidance of the spiral guide channel 23. It uses centrifugal force to throw the denser sediment particles to the channel wall and sink along the spiral channel to achieve solid-liquid separation. This structure integrates hydraulic guidance, anti-earth pressure support and sediment separation functions.

[0028] In another technical solution, the inner wall of the transition connection cavity 2 is provided with multiple hemispherical micro-protrusions 24 on the bottom or sidewall of the spiral guide channel 23. Specifically, the micro-protrusions 24 can be integrally formed with the spiral guide channel 23 by injection molding. Their diameter can be selected from 1 mm to 3 mm, and their height can be selected from 0.5 mm to 1.5 mm. They are distributed in an array on the bottom and sidewall of the guide channel, for example, in a plum blossom shape or matrix shape. The spacing between adjacent micro-protrusions 24 can be selected from 5 mm to 10 mm. When the water flows through multiple micro-protrusions 24, it will destroy the laminar boundary layer, generate local turbulence, increase the disturbance inside the water flow and the probability of collision between particles, thereby assisting the separation of sediment particles from the water body and promoting the separated sediment to enter the bottom of the channel.

[0029] In another technical solution, an in-situ soil solidification anchoring ring 10 is also included. The in-situ soil solidification anchoring ring 10 is disposed on the outer periphery of the transition connection cavity 2 and / or the outer periphery of the underground pipe access section 3, and is located outside the filter layer. Specifically, the in-situ soil solidification anchoring ring 10 can be a prefabricated annular hollow steel component with an inner diameter slightly larger than the outer diameter of the filter layer. It is fixed to the outer wall of the transition connection cavity 2 or the outer wall of the underground pipe access section 3 by welding multiple support ribs welded to its inner ring to maintain coaxiality. During construction, a high-strength, low-permeability composite reinforcement ring is formed at the interface between the anchoring ring and the surrounding soil through grouting. This can effectively prevent the soil around the interface from becoming cavitary due to water erosion or subsidence, and greatly enhance the anti-collapse and anti-seepage capabilities of the interface structure.

[0030] In another technical solution, the in-situ soil solidification anchoring ring 10 is a hollow annular structure filled with a curing agent. The ring wall of the in-situ soil solidification anchoring ring 10 has multiple grouting holes facing the surrounding soil. Specifically, the curing agent can be a cement-based grout or a polymeric chemical grout, such as polyurethane grout or acrylate grout. Multiple conical grouting holes facing the surrounding soil are uniformly opened circumferentially on the ring wall of the in-situ soil solidification anchoring ring 10. The diameter of these grouting holes can be selected from 5 mm to 15 mm. During construction, a high-pressure injection is performed into the hollow cavity of the anchoring ring by connecting an external grouting pump. For example, the grouting pressure can be selected from 0.5 MPa to 2 MPa. This propels the internal curing agent to penetrate and diffuse into the surrounding soil through these grouting holes. After the curing agent solidifies, a soil solidification ring is formed around the anchoring ring, tightly bonded to the original soil and with significantly increased strength.

[0031] In another technical solution, an inspection and observation port 11 is also provided above the transition connection cavity 2. Specifically, the inspection and observation port 11 can be a short metal or plastic pipe with a flange, which is vertically welded to the top of the transition connection cavity 2 and extends upward to the ground surface. Its top end is sealed by a bolt-type blind plate with a rubber sealing ring to prevent surface water or debris from entering. The inner diameter of the inspection and observation port 11 can be selected from 100 mm to 200 mm. When needed, the staff only needs to open the blind plate on the ground surface to directly observe the sedimentation of mud and sand or the state of the filter layer inside the transition connection cavity 2 through the inspection port. Long pole tools or small dredging equipment can be used to directly clean the sedimentation chamber 25, realizing rapid inspection and maintenance of the interface without large-scale excavation.

[0032] In another technical solution, the drainage control unit is a drainage control well 9, and the downstream end of the main underground pipe 4 extends into the drainage control well 9. The drainage control well 9 is equipped with at least one adjustable weir plate 91, which divides the inner cavity of the drainage control well 9 into an upstream chamber and a downstream chamber. Specifically, the drainage control well 9 can be a prefabricated vertical shaft structure made of concrete or corrosion-resistant plastic. The downstream end of the main underground pipe 4 extends into the inner cavity of the drainage control well 9 from one side of the well wall. A vertical chute is provided on the side of the drainage control well 9 opposite to the inlet of the main underground pipe 4. An adjustable weir plate 91 made of stainless steel or corrosion-resistant plastic is installed in the chute. The top of the adjustable weir plate 91 is connected to an adjusting handwheel outside the wellhead by a screw. By rotating the handwheel, the weir plate can be driven to move up and down in the chute, thereby changing the top elevation of the weir plate. By adjusting the height of the adjustable weir plate 91, the water level in the upstream chamber can be precisely controlled, thereby controlling the water head when drainage is started, and realizing flexible control of drainage intensity. For example, the weir plate can be lowered when rapid drainage is needed after heavy rain, and raised when groundwater level needs to be controlled during the crop growth period.

[0033] A construction method for forming the interface structure between the rat tunnel and the concealed pipe as described above is provided, comprising the following steps: S1. Layout and positioning: Based on the field slope, the direction of the underground pipe layout and the drainage requirements of the work area, determine the layout position, spacing and burial depth of the rat tunnel drainage section 1 and the main underground pipe 4, and carry out measurement and layout. S2. Install transition connection cavity 2: Reserve an interface installation position at the end of the rat tunnel and excavate the installation pit of transition connection cavity 2. Hoist the transition connection cavity 2 with the pre-set spiral guide channel 23 and anti-collapse support frame 26 into the pit, adjust the level and elevation, and ensure that the outlet of the spiral guide channel 23 faces directly downward and is aligned with the groove of the pre-excavated mud and sand collection chamber 25 at the bottom of the pit. S3. Install the flexible sleeve 5: Cool the self-locking composite sleeve to the first temperature so that it is in a relaxed state, and put it on the connection between the inlet end 21 of the mouse channel guide section 1 and the transition connection cavity 2. Then, rely on the natural rise of the ambient ground temperature to make the shape memory alloy braided mesh 52 shrink to complete the self-locking. S4. Connecting the underground pipe: Connect one end of the underground pipe access section 3 to the outlet end 22 of the transition connection cavity 2 with a socket seal, and connect the other end to the pre-embedded main underground pipe 4 through a reducer pipe 31 or a special pipe fitting. Then, on the outer periphery of the transition connection cavity 2 and the underground pipe access section 3, first wrap the inner rigid porous support member 61 and clamp it to limit its position, and then tightly bind a layer of geotextile on its outer side to form an outer filter layer. S5. Forming the anchoring ring: The prefabricated in-situ soil solidification anchoring ring 10 is placed outside the filter layer and fixed to the outer wall of the structure by welding through the supporting ribs of its inner ring. In the soil around the anchoring ring, a conductive fiber mesh made of biodegradable materials (such as cellulose) is pre-embedded, and the electrodes are inserted into the area where the fiber mesh is located. High-pressure cement-based curing agent slurry is injected into the anchoring ring by a grouting pump. After the slurry initially penetrates into the surrounding soil through the grouting holes in the ring wall, a DC electric field is applied between the electrodes. Under the action of electroosmosis, the pore water in the soil moves directionally to the cathode and is discharged. At the same time, the curing agent slurry diffuses more evenly and deeply into the anode area under the action of electrophoresis, replacing the discharged water. This process significantly accelerates the drainage and consolidation of the soil and makes the curing agent more evenly distributed. Finally, a high-strength, low-permeability solidified soil anchoring ring is formed around the interface, which greatly enhances the long-term anti-settlement and anti-shear deformation ability of the interface structure. S6. Install auxiliary components: Drill mounting holes on the upper side of the transition connection cavity 2, insert and fix the backflushing pipe 8, and waterproof it with lock nuts and sealing gaskets. At the ground surface directly above the transition connection cavity 2, install and fix the flange short pipe of the inspection and observation port 11, and seal it with a blind flange. S7. Connect the control and drainage unit: Connect the downstream end of the main underground pipe 4 to the inlet of the side wall of the constructed control and drainage well 9 through the pipe fitting. Install the adjustable weir plate 91 in the chute inside the well and connect it to the adjustment mechanism at the wellhead. Check whether the lifting and lowering is smooth. S8. Backfilling and Commissioning: After all installations are completed, the excavated foundation pit is backfilled in layers. First, graded gravel is backfilled to the filter layer and around the anchor ring. Then, the original soil is backfilled and compacted layer by layer to the ground surface. After completion, a water flow test is conducted to check for any leakage at the joints. The height of the weir plate of the drainage control unit is adjusted to ensure that the drainage strength meets the design requirements.

[0034] As a preferred embodiment of the present invention, combining all the above technical solutions, a rat tunnel and underground pipe interface structure for low-permeability black soil farmland includes: Rat tunnel guide section 1 is located in the lower part of the cultivated layer, at a depth of 0.55m and a spacing of 4m; The transition connection cavity 2, which is injection molded from HDPE, has an inlet end 21 with a diameter matching the mouse passage outlet, and an outlet end 22 with a diameter 1.5 times that of the inlet end 21, forming a gradually expanding structure. The inner wall of the cavity is provided with a spiral guide groove 23, whose spiral angle gradually changes from 40° at the inlet to 20° at the outlet. The inner wall of the spiral guide groove 23 is welded and fixed to the outer wall of a cage-type stainless steel anti-collapse support frame 26. The inner wall of the transition connection cavity 2 has multiple hemispherical micro-protrusions 24 with a diameter of 2 mm at the bottom of the spiral guide groove 23, arranged in a plum blossom pattern with a spacing of 8 mm. The concealed pipe inlet section 3 is sealed to the outlet end 22 of the transition connection cavity 2 by means of a socket, and the other end is connected to the PE corrugated main concealed pipe 4; A flexible sleeve 5 in the form of a self-locking composite sleeve is installed at the connection. The composite sleeve consists of an inner neoprene rubber elastic sealing body and an outer nickel-titanium shape memory alloy braided mesh 52. The shape memory alloy automatically shrinks at normal soil temperature and provides radial clamping force. A recessed sedimentation chamber 25, with its bottom 15 cm lower than the bottom surface of the inlet of the underground pipe access section 3, is located at the bottom of the transition connection cavity 2. A filter layer consisting of an inner perforated PP plastic sleeve and an outer geotextile is wrapped around the transition connection cavity 2 and the underground pipe access section 3. The prefabricated steel annular hollow in-situ soil solidification anchoring ring 10 has its inner ring welded and fixed to the outer wall of the transition connection cavity 2 by the support rib and located outside the filter layer. There are 8 radial grouting holes evenly distributed on the ring wall of the anchoring ring, and the inside is pre-filled with cement-based curing agent. A flanged PVC short pipe with a nominal diameter of 150 mm serves as an inspection and observation port 11, which is vertically welded to the top of the transition connection cavity 2 and leads directly to the ground surface. The top is sealed with a bolt-type blind flange. A DN50 galvanized steel pipe serves as the backwash pipe 8, with its port connected to the upper side wall of the transition connection cavity 2 and the concealed pipe access section 3 via a sealing joint, and a ball valve is provided at the outer end. The concrete structure of the drainage well 9 has the downstream end of the main underground pipe 4 extending into the well. The well is equipped with a stainless steel adjustable weir plate 91, which can be divided into upstream and downstream sections by handwheel and screw drive. When rainfall occurs, the rat tunnel guides the stagnant water into the transition connection cavity 2. The water flow rotates and slows down in the spiral guide channel 23. Under the action of centrifugal force, the mud and sand are thrown against the channel wall and sink to the mud and sand collection bin 25. The cleaner water enters the main underground pipe 4 after passing through the filter layer, and is then discharged by the control drainage well 9. The in-situ soil solidification anchoring ring 10 ensures the stability of the soil around the interface, and the self-locking composite sleeve automatically adapts to soil deformation. When maintenance is required, the sedimentation can be observed through the inspection and observation port 11, or reverse flushing can be performed through the backwash pipe 8.

[0035] To verify the performance of the rat tunnel and underground pipe interface structure used in low-permeability black soil farmland, the following tests were conducted.

[0036] The experimental site was set up in a low-lying black soil cornfield with a soil texture of clay loam to clay, a saturated hydraulic conductivity of 0.08 to 0.25 mm / min in the 0 to 40 cm soil layer, and a field slope of 0.1% to 0.3%.

[0037] Four treatments were set up: conventional without underground drainage (CK, control), single underground pipe drainage (D), direct connection between rodent trails and underground pipe (MD, prior art), and using the interface structure of the present application (MP). Each treatment was set up to be repeated 3 times, and the area of ​​the plot was 30 meters × 50 meters.

[0038] Indoor water flow and sand blockage test: The test was conducted after continuous operation for 120 minutes under the conditions of inlet water flow rate of 1.80 L / s, inlet water suspended solids concentration of 2.00 g / L, and chopped straw addition of 0.50 g / L.

[0039] The results showed that the interface structure (MP) of this application had the highest drainage retention rate, the lowest outlet suspended solids concentration, the least amount of straw debris entering the main underground pipe 4, the shallowest local flushing depth at the interface, the smallest head loss, and no blockage occurred during the three repeated runs. After backwashing, its flow recovery rate was the highest.

[0040] Field simulation of heavy rainfall drainage effect: After corn experienced heavy rainfall of 60 mm every 24 hours during its growth period, continuous monitoring was conducted for 72 hours.

[0041] The results showed that the interface structure (MP) treatment of this application had the shortest duration of surface water accumulation, the shortest time required for the soil moisture content of 0-40 cm to drop to field capacity plus 5%, the shortest duration of groundwater level shallower than 40 cm, the largest drainage volume of underground pipes in 72 hours, and the smallest surface runoff. Compared with the direct connection between rodent tunnels and underground pipes (MD) treatment, the MP treatment reduced the duration of surface water accumulation and shortened the recovery time of soil moisture content of 0-40 cm.

[0042] Anti-clogging and maintenance data after continuous rainfall events: After six consecutive simulated rainfall events (50 to 60 mm each, with an interval of 7 to 10 days), the interface drainage retention rate and maintenance status were measured.

[0043] The results showed that the drainage retention rate of the interface structure (MP) of this application decreased from 94.8% in the first event to only 91.7% in the sixth event. The amount of sediment entering the main culvert 4 was the least, and the amount of sediment that could be collected at the interface was the largest. In the six rainfall events, the MP treatment did not require excavation and maintenance, and the single maintenance time was the shortest.

[0044] Controlled drainage mode operation data: By adjusting the adjustable weir plate 91 inside the controlled drainage well 9, two controlled drainage modes can be achieved. In the rainstorm emergency drainage mode, the low-level outflow outlet is opened, resulting in the maximum drainage volume in 72 hours, a high peak drainage flow, and a stable groundwater level at a relatively deep level. In the normal controlled drainage mode, the low-level outflow outlet is closed, and only the high-level overflow is activated, resulting in a smaller drainage volume in 72 hours, a stable groundwater level at a relatively shallow level, and less nitrogen loss from the drainage.

[0045] Maize growth and yield response data: Measurements were conducted using the same maize variety and under the same fertilization and field management conditions in years with a high risk of waterlogging. The results showed that the maize treated with the interface structure (MP) of this application had the highest plant height, SPAD value, root volume, and aboveground dry matter, as well as the highest yield, with the highest yield increase compared to the control (CK).

[0046] The above data demonstrates that the interface structure (MP) of this application can comprehensively achieve functions such as flow stabilization, sedimentation, anti-clogging, anti-collapse, and drainage control. In indoor sand-laden blockage, field drainage during heavy rainfall, continuous rainfall anti-clogging, and drainage control management, its performance is significantly superior to direct connection between rodent tunnels and underground pipes (MD) and other treatment methods. By achieving efficient sediment separation and interception at the interface, this structure reduces the entry of sediment and nutrients into the main underground pipe 4, ensuring the long-term stable operation of the drainage system and ultimately promoting increased crop yield.

[0047] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A rat tunnel and underground pipe interface structure for low-permeability black soil farmland, characterized in that, include: Rat tunnel guide section; The transition connection cavity has an inlet end and an outlet end, the inlet end being connected to the mouse channel guide section, and the cross-sectional area of ​​the inlet end of the transition connection cavity being smaller than the cross-sectional area of ​​the outlet end of the transition connection cavity. The concealed pipe access section has one end connected to the outlet end of the transition connection cavity, and the other end of the concealed pipe access section is connected to the main concealed pipe. A flexible sleeve is fitted at the connection between the rat passage guide section and the inlet end of the transition connection cavity; An anti-collapse support frame is disposed inside the transition connection cavity; A sedimentation chamber is located at the bottom of the transition connection cavity, and the bottom surface of the sedimentation chamber is lower than the bottom surface of the end of the underground pipe connection section that communicates with the transition connection cavity. The filter layer includes a first filter section covering the periphery of the transition connection cavity and a second filter section covering the periphery of the concealed pipe inlet section; A backflushing pipe, the opening of which is connected to the inner cavity of the transition connection cavity and / or the inner cavity of the concealed pipe access section; The control and discharge section is located downstream of the main concealed pipe.

2. The rat tunnel and underground pipe interface structure for low-permeability black soil farmland as described in claim 1, characterized in that, The flexible sleeve is a self-locking composite sleeve, which includes: The inner elastic sealing body is in contact with the outer wall of the rat passage guide section and the transition connection cavity; A shape memory alloy woven mesh is wrapped around the outer surface of the inner elastic seal. The shape memory alloy woven mesh shrinks and deforms under preset temperature or stress conditions, and applies a radial clamping force to the inner elastic seal.

3. The rat tunnel and underground pipe interface structure for low-permeability black soil farmland as described in claim 2, characterized in that, The material of the shape memory alloy woven mesh is a two-way shape memory alloy, which is in a relaxed state at a first temperature below the normal soil temperature and in a contracted state at a second temperature within the normal soil temperature range.

4. The rat tunnel and underground pipe interface structure for low-permeability black soil farmland as described in claim 1, characterized in that, The inner wall of the transition connection cavity is provided with a spiral guide groove. The spiral guide groove extends spirally along the inner wall of the transition connection cavity. The inner wall of the spiral guide groove is fixedly connected to the outer wall of the anti-collapse support frame. The end of the spiral guide groove is connected to the inlet of the sedimentation chamber. The spiral angle of the spiral guide groove gradually decreases along the water flow direction.

5. The rat tunnel and underground pipe interface structure for low-permeability black soil farmland as described in claim 4, characterized in that, The inner wall of the transition connection cavity is provided with multiple hemispherical micro-protrusions on the bottom or side wall of the spiral guide channel.

6. The rat tunnel and underground pipe interface structure for low-permeability black soil farmland as described in claim 1, characterized in that, It also includes an in-situ soil solidification anchoring ring, which is located on the outer periphery of the transition connection cavity and / or the outer periphery of the culvert access section, and is located outside the filter layer.

7. The rat tunnel and underground pipe interface structure for low-permeability black soil farmland as described in claim 6, characterized in that, The in-situ soil solidification anchoring ring is a hollow ring structure filled with a curing agent. The ring wall of the in-situ soil solidification anchoring ring is provided with multiple grouting holes facing the surrounding soil.

8. The rat tunnel and underground pipe interface structure for low-permeability black soil farmland as described in claim 1, characterized in that, It also includes a maintenance observation port located above the transition connection cavity.

9. The rat tunnel and underground pipe interface structure for low-permeability black soil farmland as described in claim 1, characterized in that, The drainage control section is a drainage control well. The downstream end of the main underground pipe extends into the drainage control well. The drainage control well is equipped with at least one adjustable weir plate, which divides the inner cavity of the drainage control well into an upstream chamber and a downstream chamber.

10. A construction method for forming an interface structure between a rat tunnel and a concealed pipe as described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Determine the location of the rodent tunnel drainage section and the main underground pipe according to the field slope and drainage requirements; S2. Install a transition connection cavity at the end of the rat tunnel to ensure that the cross-sectional area of ​​its inlet end is smaller than the cross-sectional area of ​​its outlet end; S3. Install a flexible tube sleeve in the form of a self-locking composite sleeve at the connection between the rat passage guide section and the transition connection cavity; S4. Connect the rear end of the transition connection cavity to the main concealed pipe through the concealed pipe access section, and set a filter layer; S5. On the outer periphery of the transition connection cavity and / or the underground pipe access section, electrodes and biodegradable conductive fiber mesh are set, and curing agent slurry is injected into the surrounding soil. Then, an electric field is applied through the electrodes to make the curing agent slurry diffuse into the surrounding soil and drain the water, forming an in-situ soil curing anchor ring. S6. Install a backflushing and unclogging branch pipe, the pipe opening of which is connected to the inner cavity of the transition connection cavity and / or the inner cavity of the concealed pipe access section; S7. Connect the downstream of the main underground pipe to the drainage control unit, wherein the drainage control unit is a drainage control well and is provided with at least one adjustable weir plate. S8. After completing the above installation steps, backfill and compact in layers, and conduct water flow test and control and drainage mode debugging.

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