A blind drain with multiple drainage paths

Abstract

This utility model discloses a blind ditch with multiple drainage paths, relating to the technical field of internal drainage systems for dams. It includes a culvert horizontally buried in a drainage pit, which is inverted conical in shape and comprises multiple layers of crushed stone arranged from top to bottom. The bottom end of the culvert is fixed to a reinforced concrete protective layer. The drainage pit is surrounded by a permeable geotextile, with permeable geotextile placed between the multiple crushed stone layers. Vertical permeable geotextile is placed on both sides of the bottom end of the upper crushed stone layer. The lower half of the culvert has several upwardly inclined baffles, and drainage holes are provided above the base of the baffles. The horizontal culvert and the vertical drainage pit work together to achieve rapid dispersion and centralized discharge of seepage within the dam, improving drainage efficiency and increasing dam stability.

Description

Technical Field

[0001] This utility model relates to the technical field of drainage systems inside dams, and in particular to a blind ditch with multiple drainage paths. Background Technology

[0002] In existing hydraulic engineering projects, the internal drainage systems of dams generally adopt single-layer, unidirectional blind drain structures. These drains have a limited drainage path, guiding water only in a predetermined direction. This fails to address seepage variations at different times and locations within the dam, resulting in low drainage efficiency, poor phreatic line reduction, and a high risk of dam leakage and landslides. Furthermore, blind drains are often filled with gravel or simple PVC pipes, lacking reliable fixing measures. Long-term exposure to water pressure and soil deformation makes them prone to displacement, blockage, and even breakage, leading to maintenance difficulties. Especially during periods of multi-level loads or concentrated rainfall, a single drainage channel is highly susceptible to overload, creating localized stagnant water zones and weakening dam stability. Therefore, structural optimization and diversified drainage paths are urgently needed.

[0003] Chinese Patent Publication No. CN107905263B, Publication Date: April 13, 2018, discloses a Chinese patent entitled "Self-drainage Structure for Inspection Wells," which includes an inspection well and a well cover. The well cover fits over the inspection well, and a sump is provided inside the inspection well. Several steel pipes are pre-embedded in the inspection well, with one end of each pipe connected to the sump. The inspection well is buried in a drainage pit, which is an inverted cone shape and includes a structural layer, a backfill layer, and a permeable layer arranged from top to bottom. The upper surface of the permeable layer is flush with the highest groundwater level, and the upper surface of the sump is flush with the upper surface of the permeable layer. The other end of each steel pipe extends into the permeable layer. Permeable geotextile is laid on the outside of the permeable layer and between the backfill layer and the permeable layer. This drainage structure only has one vertical drainage path, which is too simple and prone to overload operation, forming localized stagnant water areas. Utility Model Content

[0004] This utility model provides a blind ditch with multiple drainage paths. By setting up two drainage paths, horizontal and vertical, it improves drainage efficiency and increases the stability of the dam.

[0005] A further objective of this invention is to improve the structural strength of blind drains by providing a steel reinforcement protective layer to protect the culvert.

[0006] A further objective of this invention is to increase drainage efficiency by setting drainage holes and baffles to form additional water channels.

[0007] To achieve the above objectives, this utility model adopts the following technical solution: a blind ditch with multiple drainage paths, including a culvert, which is horizontally buried in a drainage pit. The drainage pit is inverted conical in shape and includes multiple layers of crushed stone arranged from top to bottom. The bottom end of the culvert is fixed to a reinforced concrete protective layer. The drainage pit is wrapped with permeable geotextile, and permeable geotextile is placed between the multiple layers of crushed stone. Vertical permeable geotextile is placed on both sides of the bottom end of the upper layer of crushed stone. The lower half of the culvert is provided with several upwardly inclined baffles, and drainage holes are provided above the base of the baffles.

[0008] Preferably, the multi-stage crushed stone layer includes a primary crushed stone layer and a tertiary crushed stone layer arranged from top to bottom, with a secondary crushed stone layer between the primary and tertiary crushed stone layers. The particle size of the primary, secondary, and tertiary crushed stone layers increases from top to bottom, forming a gradient filtration system. This ensures that fine particles on the surface are not lost, while the larger particles at the bottom provide high permeability channels, significantly improving the overall water conductivity and extending the service life of the blind drain.

[0009] Preferably, each of the multi-level crushed stone layers is filled with crushed stone, with the particle size increasing from top to bottom. The horizontal culverts and vertical drainage pits work together to achieve three-dimensional drainage that is "concentrated laterally and dispersed longitudinally," which can quickly lower the phreatic line of the dam body, avoid local water stagnation caused by unidirectional drainage, and improve the anti-sliding stability of the dam body.

[0010] Preferably, the drainage pit is situated on a foundation layer, with a reinforced concrete protective layer fully installed at the bottom of the pit. The foundation layer is made of concrete, preferably C20 grade, and its length exceeds the length of the bottom of the drainage pit. The bottom of the drainage pit is 17 meters long, and the foundation layer is 19 meters long, with the drainage pit positioned at the center of the foundation layer. The top of the drainage pit is 27 meters long. The 19-meter-long foundation layer extends 1 meter beyond each end of the 17-meter pit, forming a cantilevered foundation to distribute the upper load. The C20 concrete provides a smooth, high-strength support surface, preventing differential settlement from causing deformation or breakage of the culvert.

[0011] Preferably, the reinforcing steel protective layer is set within the third-level crushed stone layer and on the foundation layer. The height of the reinforcing steel protective layer is less than the height of the third-level crushed stone layer. The cross-section of the reinforcing steel protective layer is a rectangle with the top edge sloping upwards from the center. The culvert is set within the first-level, second-level, and third-level crushed stone layers, with most of it set within the third-level crushed stone layer. One end of the baffle is set at the contact point between the top of the reinforcing steel protective layer and the lower half of the culvert, and the other end is set on the permeable geotextile. The drainage holes are set downwards at the same angle as the baffle. The drainage pit can protect the culvert from lateral soil impact. While protecting the pipe, the baffle forms a natural water flow zone. Vertically downward seepage water is guided by the baffle and flows through the drainage holes to the culvert, improving drainage efficiency.

[0012] Preferably, several reinforcing bars are provided near the outer ring within the concrete cover, which is filled with concrete. The concrete for the concrete cover is preferably C25 grade. The circumferential reinforcement within the concrete cover, combined with cast-in-place C25 concrete, forms a rigid shell that supports and positions the culvert, resisting lateral earth pressure and construction impact, thus avoiding the common problems of culvert displacement and damage found in traditional blind drains.

[0013] Preferably, the particle size of the crushed stone in the primary crushed stone layer is 3-5 cm, and the particle size of the crushed stone in the secondary crushed stone layer is 5-10 cm. The taper of the side of the drainage pit is 60-80 degrees, and the taper is preferably set to 75.96 degrees. The ratio of the diameter of the culvert to the height of the drainage pit is 0.5-0.7, and the height ratio is preferably set to 0.6.

[0014] Preferably, the gravel particle size in the tertiary crushed stone layer is 10-30 cm, and the culvert pipe does not contact the subbase. The culvert pipe is preferably a 12-meter diameter pipe. A 1.98-meter gap is preferably provided between the bottom end of the culvert pipe and the subbase.

[0015] Preferably, the vertical permeable geotextile is placed inside the primary crushed stone layer and does not contact the top of the primary crushed stone layer.

[0016] Preferably, the height of the tertiary crushed stone layer is greater than the heights of the secondary and primary crushed stone layers. The primary and secondary crushed stone layers have the same height, preferably 5 meters. The height of the tertiary crushed stone layer is preferably 10 meters. Precise control of the vertical drainage starting point avoids material waste caused by full-depth installation; simultaneously, in conjunction with the primary fine crushed stone, it forms a rapid water-conducting channel with a "fine at the top and coarse at the bottom," shortening the seepage path and improving drainage response speed.

[0017] Beneficial effects: This utility model achieves rapid dispersion and centralized discharge of seepage inside the dam body through a three-dimensional structure of "inverted cone-shaped foundation pit + multi-level crushed stone layer + bidirectional drainage path": the horizontal culvert and the vertical drainage foundation pit work together to simultaneously discharge seepage water at different elevations, significantly reducing the phreatic line and improving the overall stability of the dam body; the gradient filtration design with the crushed stone particle size increasing from top to bottom prevents the loss of fine particles and ensures high permeability, extending the service life of the blind drain; the reinforced concrete protective layer stably supports the culvert, resisting lateral earth pressure and construction impact, completely solving the problems of easy displacement and breakage of traditional blind drain culverts. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view of the present invention.

[0019] Figure 2 for Figure 1 Enlarged view of point A.

[0020] Attached reference numerals: 1: Primary crushed stone layer; 2: Secondary crushed stone layer; 3: Tertiary crushed stone layer; 4: Culvert; 5: Reinforcing steel protective layer; 6: Permeable geotextile; 7: Subbase; 8: Reinforcing steel; 9: Baffle; 10: Drainage hole; 11: Drainage pit. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0022] In water conservancy and geotechnical engineering, blind drains are important drainage facilities, and their drainage efficiency and structural stability directly affect the safety of dams. This utility model provides a blind drain with multiple drainage paths. Through the coordinated design of horizontal and vertical drainage paths, combined with gradient filtration and structural protection measures, it effectively solves the problems of traditional blind drains, such as single drainage method, easy clogging, and insufficient structural strength.

[0023] like Figure 1 As shown, the blind drain uses a horizontally arranged culvert 4 as its core drainage channel, which is horizontally buried within an inverted conical drainage pit 11. The inverted conical drainage pit 11 gradually narrows from top to bottom. This shape design guides seepage water from the surface and inside the dam to converge at the bottom of the pit, providing a natural path for vertical drainage. The drainage pit 11 is entirely wrapped with permeable geotextile 6. The permeable geotextile 6 has good permeability and filtration properties, allowing water to pass through while preventing soil particles from entering the pit and avoiding clogging by fine soil. At the same time, permeable geotextile 6 is also installed between the multi-level crushed stone layers. The vertical permeable geotextile 6 on both sides of the bottom of the upper crushed stone layer further separates the crushed stone of different levels, preventing the mixing of crushed stone at different levels and ensuring the long-term effectiveness of the gradient filtration system.

[0024] The multi-level crushed stone layer is arranged in layers, from top to bottom: primary crushed stone layer 1, secondary crushed stone layer 2, and tertiary crushed stone layer 3. Each layer is filled with crushed stone, and the particle size increases from top to bottom, forming a scientific gradient filtration system. The primary crushed stone layer 1 is located at the top, in contact with the surface soil of the dam. Its smaller particle size can filter fine soil particles carried by surface seepage water, preventing fine soil from entering the lower layers with the water flow. The secondary crushed stone layer 2 serves as an intermediate transition layer. The medium particle size can both receive the water flow filtered from the upper layers and further block residual fine particles. The tertiary crushed stone layer 3 is located at the bottom, and its largest particle size creates a high permeability channel, providing conditions for the water flow to quickly converge into the culvert 4. This gradient design ensures that surface fine particles are not lost, avoiding deformation of the dam structure due to soil erosion, and also improves the overall water conduction capacity through the high permeability of the large-diameter crushed stone at the bottom, extending the service life of the blind drain.

[0025] like Figure 1 and Figure 2 As shown, the horizontal culvert 4 and the vertical drainage pit 11 together form a three-dimensional drainage network that is "concentrated laterally and dispersed longitudinally." Seepage water inside the dam or surface water first enters the drainage pit 11. Vertically, the water penetrates the pores of the gravel layer step by step under its own weight, and the permeable geotextile 6 clearly separates the various levels of gravel layers, ensuring that the water flows smoothly down the predetermined channel and eliminating the risk of localized water stagnation. Horizontally, the water that converges at the connecting well is quickly carried away by the culvert 4, achieving three-dimensional and continuous drainage. This dual-pathway system can significantly reduce the dam's phreatic line in a short time. An excessively high phreatic line increases the dam's self-weight and pore water pressure, weakening its anti-sliding force. The three-dimensional drainage system, through longitudinal dispersion and lateral concentration, effectively eliminates dead zones caused by unidirectional drainage, rapidly dissipating the pore water pressure inside the dam and significantly improving the overall anti-sliding stability, thus providing a solid guarantee for the long-term safe operation of the dam.

[0026] like Figure 1As shown, the lower half of the culvert 4 is carefully equipped with several upward-sloping baffles 9. These baffles 9 act as "guides" to direct water flow, playing a crucial role in the drainage process of the culvert 4. Drainage holes 10 are provided at corresponding positions above the base of the baffles 9 in the culvert 4. The drainage holes 10 are inclined downwards, with the inclination angle perfectly matching that of the baffles 9. This angle-matching design ensures that the water flows smoothly along the predetermined path. One end of the baffle 9 is fixed at the contact point between the top of the reinforcing steel protective layer and the lower half of the culvert 4, while the other end is firmly connected to the permeable geotextile 6, forming a stable support structure. When seepage water from inside the dam body vertically infiltrates into the drainage pit 11, the baffles 9 act like a pair of powerful hands, guiding the originally dispersed seepage water towards the culvert 4. The seepage water flows along the inclined surface of the baffles 9 and finally enters the interior of the culvert 4 through the angle-matched drainage holes 10, achieving centralized drainage. This design prevents seepage water from spreading or stagnating throughout the pit, significantly improving drainage efficiency.

[0027] The drainage pit 11 acts as a "protective barrier" for the culvert 4, effectively protecting it from lateral earth pressure. Within the dam structure, the soil exerts continuous lateral pressure on the pit's sidewalls. The inverted cone-shaped pit structure, combined with the surrounding permeable geotextile 6, disperses and resists this pressure, preventing soil compression of the culvert 4 and subsequent deformation or damage. Simultaneously, the pit's internal baffle 9 creates a natural drainage zone. Guided by the baffle 9, the water flows in an orderly manner, preventing erosion of the pit's sidewalls while ensuring rapid convergence of seepage water towards the culvert 4, thus achieving a dual function of protection and drainage. The taper of the drainage pit 11's sides is 60–80 degrees, with a preferred taper of 75.96 degrees. This angle has been verified through multiple structural mechanics and fluid mechanics simulations. The inverted cone-shaped pit gradually narrows from top to bottom, and the 75.96-degree taper achieves the optimal balance between seepage convergence speed and structural stability.

[0028] The ratio of the diameter of culvert 4 to the height of drainage pit 11 is 0.5–0.7, with a preferred height ratio of 0.6. This ratio design fully considers the matching relationship between the drainage capacity of culvert 4 and the seepage capacity of the pit. As the core drainage channel, the diameter of culvert 4 directly determines the drainage flow rate. The preferred material specifications for permeable geotextile 6 are 300g / ㎡, with an upper elongation ≥300mm. Permeable geotextile 6 has a relatively low cost but plays multiple key roles: as the outer protective structure of drainage pit 11, it ensures smooth seepage into the pit and prevents soil particle loss through a dual function of filtration and reinforcement, maintaining the stability of the dam structure; at the same time, its good flexibility and adaptability can conform to the inverted conical contour of the pit, ensuring that the shape of the pit does not change during long-term use, providing a stable structural foundation for the coordinated work of baffle 9 and culvert 4. This low-cost and high-efficiency design improves the safety and stability of the pit while reducing the overall cost and maintenance cost of the project.

[0029] The drainage pit 11 is firmly set on the concrete cushion layer 7, which serves as the foundation structure of the entire blind drain. The cushion layer 7 is meticulously cast using C20 grade concrete. With its sufficient strength and excellent durability, the C20 concrete provides a flat and solid support surface for the drainage pit 11 and culvert 4. This solid foundation is a crucial prerequisite for ensuring the long-term stable operation of the blind drain. The cushion layer 7 is precisely designed to be 19 meters long, longer than the 17 meters at the bottom of the drainage pit 11, extending outwards by 1 meter at each end, forming a unique "cantilever" foundation. This outward extension design has significant advantages; it can evenly distribute various loads from above, including the weight of the various levels of crushed stone layers, the flowing water, and the weight of the drainage pit 11 itself, across a larger area of ​​the foundation. By expanding the load-bearing area, it effectively avoids foundation settlement problems caused by concentrated loads, thereby preventing deformation or breakage of the culvert 4 due to differential foundation settlement, ensuring the safety of the blind drain structure from the foundation level.

[0030] The drainage pit 11 is precisely positioned at the center of the foundation layer 7, with a top length of 27 meters and an overall inverted cone shape, gradually narrowing from the top 27 meters to the bottom 17 meters. This size design is highly compatible with the support range of the foundation layer 7. The narrowing trend of the inverted cone shape guides the water flow to converge at the bottom of the pit, while the central positioning ensures that the entire blind drain structure is subjected to balanced stress on the foundation layer 7, avoiding excessive local stress and providing a structural foundation for the stable operation of the blind drain.

[0031] The reinforced concrete protective layer 5 is installed at the bottom of the drainage pit 11, providing comprehensive protection for the culvert 4. As the core component of the horizontal drainage system, the structural integrity of the culvert 4 directly affects the drainage efficiency and service life of the blind drain, making its protection crucial. The reinforced concrete protective layer 5 is made of reinforced concrete and tightly wraps around the bottom and sides of the culvert 4, forming a robust protective barrier. This structure effectively distributes the upper loads borne by the culvert 4, including the weight transmitted from the various levels of crushed stone layers and the pressure generated by the flowing water, preventing the culvert 4 from cracking or even breaking due to long-term exposure to these loads.

[0032] The reinforced concrete protective layer 5 and the concrete cushion layer 7 are tightly bonded together, forming a unified load-bearing system. This holistic load-bearing structure further enhances the overall structural strength of the blind drain, ensuring that the culvert 4 can still operate stably for a long time even when facing complex geological conditions, such as uneven foundation settlement and changes in soil lateral pressure. The drainage function will not be affected by changes in the external environment, fundamentally guaranteeing the reliability and durability of the blind drain.

[0033] The permeable geotextile 6 plays multiple roles in the entire blind drain structure: the permeable geotextile 6 wrapping the perimeter of the drainage pit 11 prevents soil from the dam body from entering the pit, protecting the permeability of the gravel layer; the layered permeable geotextile 6 separates the gravel at different levels, maintaining the stability of the gradient filtration system; and the vertical permeable geotextile 6 on both sides of the bottom of the upper gravel layer guides the water flow towards the center of the pit, improving drainage efficiency. The synergistic effect of these permeable geotextiles 6 ensures the orderly flow of water within the blind drain, reducing the risk of clogging.

[0034] In practical applications, the three-dimensional drainage effect of this blind drain is significant. When encountering heavy rainfall or increased seepage in the dam body, the gradient gravel layer rapidly guides water, while the permeable geotextile 6 effectively filters it. Water flows vertically through infiltration and converges at the bottom. The culvert 4 is connected to the horizontal pipe via a connecting well, and water from the horizontal pipe is discharged laterally through the culvert 4, rapidly lowering the dam's phreatic line. The cantilevered design of the concrete cushion layer 7 and the protective effect of the steel reinforcement protective layer 5 ensure that the blind drain maintains structural stability under long-term loads and water erosion, without problems such as culvert 4 deformation or gravel layer blockage. This design improves drainage efficiency and enhances dam stability, providing a reliable guarantee for the safe operation of water conservancy projects.

[0035] This invention achieves a dual improvement in drainage efficiency and structural stability of blind drains through a three-dimensional drainage path consisting of a horizontal culvert 4 and a vertical drainage pit 11, gradient filtration through multi-stage crushed stone layers, foundation support through a concrete cushion layer 7, and structural protection through a steel reinforcement protective layer 5. The coordinated operation of all components solves the problems of traditional blind drains being simple to drain and prone to clogging, while also extending their service life through scientific structural design. It has significant practical value in fields such as water conservancy and geotechnical engineering.

[0036] In the structural design of this blind drain, the layout and material selection of the reinforcing steel protective layer 5 are crucial for the protection of the culvert 4. The reinforcing steel protective layer 5 is set within the grade III crushed stone layer 3 and firmly laid on the subbase 7, with a rectangular cross-section that slopes upwards from the center. This sloping cross-section design allows for better contact with the curved outer wall of the culvert 4, increasing the contact area and ensuring more even stress distribution on the culvert 4. Several reinforcing bars 8 are distributed near the outer ring within the reinforcing steel protective layer 5, with C25 strength concrete filling the spaces between them. Through the combination of circumferential reinforcement and cast-in-place concrete, a robust rigid shell is formed. This rigid shell supports the culvert 4, not only accurately positioning it and preventing displacement during construction or use, but also effectively resisting lateral earth pressure from the grade III crushed stone layer 3 and external construction impacts. In traditional blind drains, the culvert 4 often experiences displacement and damage due to a lack of effective protection; this reinforced concrete protective layer fundamentally solves this problem, ensuring the long-term stable operation of the culvert 4.

[0037] The multi-stage crushed stone layer design, with its varying particle size and height, forms a scientifically graded drainage system. The primary crushed stone layer (1) has a particle size of 3–5 cm, the secondary layer (2) has 5–10 cm, and the tertiary layer (3) has 10–30 cm, with the particle size increasing from top to bottom. The primary layer (1), as the uppermost layer, directly contacts the surface soil of the dam. Its smaller particle size filters out fine soil particles carried by seepage, preventing them from entering the lower layers and clogging the drainage channels. The secondary layer (2), with its medium particle size, receives the filtered water from the upper layers, further blocking residual fine particles while providing a transitional water-conducting space. The tertiary layer (3), with its maximum particle size, forms a highly permeable channel, allowing the collected water to flow quickly towards the culvert (4). The tertiary layer (3) has a height of 10 meters, greater than the 5-meter height of the secondary and primary layers (1), while the primary and secondary layers (2) have the same height. This highly differentiated design allows the lower layer of coarse-grained gravel to occupy more space, providing a more sufficient water-conducting path for deep infiltration, while the upper layer of fine-grained gravel focuses on filtering and initially guiding surface infiltration, forming a "fine on top, coarse on bottom" rapid water-conducting channel, which significantly shortens the infiltration path and improves the drainage response speed.

[0038] The installation location of culvert 4 is precisely planned, with most of it placed within the tertiary crushed stone layer 3, maintaining a 1.98-meter gap between it and the subbase 7, preventing direct contact. This gap also reduces the direct constraint of the subbase 7 on culvert 4, preventing additional stress on culvert 4 due to subbase 7 settlement, and further protecting the structural integrity of culvert 4. Culvert 4 is preferably a large-diameter pipe of 12 meters to ensure rapid drainage of large amounts of accumulated seepage water, avoiding stagnant water formation within the tertiary crushed stone layer 3.

[0039] The height of the third-level crushed stone layer 3 is greater than that of the second-level and first-level crushed stone layers 1. The first-level and second-level crushed stone layers 2 have the same height (both 5 meters), while the third-level crushed stone layer 3 has a height of 10 meters. This height difference design allows the third-level crushed stone layer 3 to occupy more space in the entire drainage pit 11, providing ample water guiding and collection areas for deep seepage. The first-level and second-level crushed stone layers 2 have the same height, forming a transition section that connects the upper and lower layers, ensuring the continuity of seepage flow from the upper to the middle layer. The high space design of the third-level crushed stone layer 3, combined with the high permeability of its large-diameter crushed stones, creates a "fine at the top, coarse at the bottom" structure with increasing height, shortening the seepage path and making the flow of seepage from the surface to the bottom layer more efficient. This significantly improves the drainage response speed of the blind ditch, enabling it to function quickly in the event of heavy rainfall or a surge in dam seepage.

[0040] The synergistic action of each component constructs an efficient three-dimensional drainage network. The inverted cone-shaped drainage pit 11 guides seepage from the dam body towards the center. Vertically, under the gradient guidance of the primary, secondary, and tertiary crushed stone layers 3, the seepage rapidly infiltrates downwards through the filtration and constraint of the permeable geotextile 6. Horizontally, the seepage converging at the connecting well is discharged centrally through the culvert 4, achieving a drainage effect of "lateral concentration and vertical dispersion." The reinforced concrete protective layer 5 ensures the stable operation of the culvert 4, and the gradient design of the multi-stage crushed stone layers ensures both filtration and water guidance functions. This collaborative working mode can simultaneously drain seepage from different elevations, significantly lowering the dam's phreatic line, avoiding localized water stagnation, and improving the dam's anti-sliding stability. Simultaneously, gradient filtration reduces the risk of clogging, extends the service life of the blind drain, and provides a reliable guarantee for the safe operation of the water conservancy project.

[0041] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the protection scope of this utility model.

Claims

1. A blind drain with multiple drainage paths, characterized in that, It includes culverts, which are horizontally buried in the drainage pit. The drainage pit is inverted cone-shaped and includes multi-level crushed stone layers arranged from top to bottom. The bottom end of the culvert is fixed on the steel reinforcement protective layer. The drainage pit is wrapped with permeable geotextile. Permeable geotextile is installed between the multi-level crushed stone layers. Vertical permeable geotextile is installed on both sides of the bottom end of the upper crushed stone layer. The lower half of the culvert is equipped with several upward-sloping baffles, and the culvert has drainage holes above the base of the baffles.

2. The blind drain provided with a plurality of water discharge paths according to claim 1, wherein The multi-level crushed stone layer includes a primary crushed stone layer and a tertiary crushed stone layer arranged from top to bottom, with a secondary crushed stone layer between the primary and tertiary crushed stone layers.

3. The blind drain provided with a plurality of water discharge paths according to claim 1 or 2, wherein Each of the multi-level crushed stone layers is filled with crushed stone, with the particle size increasing from top to bottom.

4. The blind drain provided with a plurality of water discharge paths according to claim 2, wherein The drainage pit is set on the foundation layer, and the steel reinforcement protective layer is fully installed at the bottom of the drainage pit. The taper of the side of the drainage pit is 60 to 80 degrees.

5. The blind drain provided with a plurality of water discharge paths according to claim 4, wherein The steel reinforcement protective layer is set inside the third-level crushed stone layer and on the cushion layer. One end of the baffle is set at the contact point between the top of the steel reinforcement protective layer and the lower half of the culvert, and the other end is set on the permeable geotextile.

6. The blind drain provided with a plurality of water discharge paths according to claim 1 or 2 or 4, wherein Several steel bars are installed near the outer ring inside the steel reinforcement protective layer, which is filled with concrete.

7. The blind drain provided with a plurality of water discharge paths according to claim 2, wherein The particle size of the gravel in the primary gravel layer is 3-5 cm, and the particle size of the gravel in the secondary gravel layer is 5-10 cm.

8. The blind drain provided with a plurality of water discharge paths according to claim 5, wherein The gravel particle size in the third-level crushed stone layer is 10-30cm. The culvert and the subbase do not contact each other. The drainage holes are set downward at the same angle as the baffle.

9. The blind drain provided with a plurality of water discharge paths according to claim 2, wherein The vertical permeable geotextile is placed inside the primary crushed stone layer, without contacting the top of the primary crushed stone layer.

10. The blind drain provided with a plurality of water discharge paths according to claim 2, wherein The height of the third-level crushed stone layer is greater than that of the second-level and first-level crushed stone layers, and the ratio of the diameter of the culvert to the height of the drainage pit is 0.5 to 0.7.

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