A roadbed drainage system with gravel blind drains suitable for West Africa
By combining surface main drainage ditches with underground gravel blind ditches into a three-dimensional drainage system, multiple deficiencies in the roadbed drainage system in West Africa have been resolved, achieving efficient and stable drainage and improving the structural stability and service life of the roadbed.
Patent Information
- Application Number
- CN202522667872.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-16
- Publication Date
- 2026-11-06
- Estimated Expiration
- 2035-12-16
AI Technical Summary
Existing roadbed drainage systems in West Africa suffer from problems such as limited drainage dimensions, poor anti-siltation performance, insufficient drainage capacity, and lack of proactive control over groundwater levels. These issues result in high roadbed moisture content, reduced bearing capacity, and susceptibility to road damage.
A three-dimensional drainage system combining surface main drainage ditches and underground gravel blind ditches is adopted, including main drainage ditches, first gravel blind ditches and second gravel blind ditches. A permeable geotextile filter layer and a reverse filter protection layer are set up. A multi-stage filtration system is constructed using water collection and infiltration pipes to form a three-dimensional drainage network, which actively collects and removes water that seeps into the roadbed.
It effectively removes surface and groundwater, improves the overall efficiency of the drainage system, maintains the optimal moisture content of the roadbed, prevents soil particle blockage, and enhances the system's anti-siltation performance and drainage capacity.
Smart Images
Figure CN224942963U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of road engineering technology, specifically to a roadbed drainage system with gravel blind ditches suitable for West Africa. Background Technology
[0002] In road engineering, the performance of the subgrade drainage system directly determines the structural stability and service life of the road. This challenge is particularly severe in tropical West African regions such as Nigeria. The region's rainy season is characterized by high rainfall intensity and long duration, with annual rainfall reaching 1500-3000 mm, mostly in short bursts of intense rainfall. Traditional surface drainage methods mainly rely on open ditches, which can remove surface runoff but are ineffective at removing gravity and capillary water that seeps into the subgrade. This results in the subgrade soil remaining in a high-water-content state for extended periods, significantly reducing its bearing capacity and leading to road subsidence, frost heave, and other road defects.
[0003] Currently used roadbed drainage systems have several inherent defects: First, their drainage dimension is singular, mainly relying on surface runoff for removal, lacking an effective mechanism for diverting water accumulation inside the roadbed, and thus failing to fundamentally reduce the roadbed's moisture content; second, the system's anti-clogging performance is insufficient, with fine soil particles easily entering with the water flow and causing blockages, leading to a rapid decline in drainage efficiency and making maintenance difficult; third, existing designs are mostly passive drainage systems, lacking the ability to actively control groundwater levels, making it difficult to prevent the continuous replenishment of the roadbed by groundwater; finally, under short-term heavy rainfall conditions, the system's drainage capacity is insufficient, and it is prone to failure due to instantaneous overload.
[0004] Therefore, given the unique climatic conditions and engineering requirements of West Africa, there is an urgent need to develop a new type of roadbed drainage system with three-dimensional drainage, efficient anti-clogging, and large-capacity drainage. Utility Model Content
[0005] The purpose of this invention is to overcome the shortcomings of existing technologies, such as single drainage dimension, poor anti-clogging performance, insufficient drainage capacity, and lack of active control over groundwater levels, and to provide a roadbed drainage system with gravel blind ditches suitable for West Africa.
[0006] In a first aspect, the present invention provides a roadbed drainage system with gravel blind ditches applicable to West Africa, comprising a main drainage ditch located on the surface and a first gravel blind ditch and several second gravel blind ditches located underground. The main drainage ditch is set along the length of the foundation, and the first gravel blind ditch is set below the main drainage ditch; at least one water collection and seepage pipe is set inside the first gravel blind ditch, and the water collection and seepage pipe is set at the bottom of the first gravel blind ditch. The second gravel blind drain is installed in the foundation, and several second gravel blind drains are installed on the side of the first gravel blind drain and communicate with the first gravel blind drain. The second gravel blind drains are located inside the first gravel blind drain.
[0007] Preferably, a filter layer is provided between the main drainage ditch and the first gravel blind ditch, the filter layer is arranged along the outer circumference of the first gravel blind ditch, and the filter layer is a permeable geotextile.
[0008] The permeable geotextile should be a Class I non-woven geotextile, with a flat seam for stitching. The seam width should be no less than 10cm, and the seam strength should be equal to or greater than 90% of the specified holding strength. The site should be leveled and debris cleared before laying.
[0009] Preferably, the gravel particles filled in the first gravel blind drain have a particle size of 5-20mm and a mud content of ≤3%.
[0010] Preferably, the water collection and seepage pipe is a perforated U-PVC pipe with an opening rate of 30-40%, an opening diameter of 3-10 mm, and a laying slope of 0.2%-0.5%.
[0011] Preferably, a reverse filter protective layer is provided at the bottom of the first gravel blind ditch. The reverse filter protective layer is made of non-woven geotextile and is located outside the filter layer. The reverse filter protective layer is located at the bottom and both sides of the first gravel blind ditch.
[0012] Non-woven geotextile is a composite geotextile consisting of two layers of fabric and one layer of membrane. The ratio of fabric weight to membrane thickness to fabric weight is 200g / (0.5-1mm) / 200g. The geotextile must be consistent with the permeable geotextile. The sewing method is hot-melt welding, and the connection width is not less than 10cm.
[0013] Preferably, the cross-sectional area of the second gravel blind drain is smaller than the cross-sectional area of the first gravel blind drain.
[0014] Preferably, the gravel particles filling the second gravel blind drain have a particle size of 5-20mm and a mud content of ≤3%. Preferably, the distance between adjacent second gravel blind drains is 25m-35m.
[0015] Compared with the prior art, the beneficial effects of this utility model are as follows: 1. By organically combining the surface drainage system (main drainage ditch) with the underground drainage system (gravel blind ditch), a complete three-dimensional drainage network is constructed. This system can not only effectively remove surface runoff, but also penetrate deep into the roadbed to actively collect and remove gravity water and capillary water that seeps into the roadbed, realizing the transformation from "passive drainage" to "active drainage" and significantly improving the overall efficiency of the drainage system; 2. It has a water storage and regulation function: The graded crushed stone filling inside it forms a large water storage space and a fast drainage channel. During rainfall, it can temporarily store some groundwater to relieve drainage pressure; after rain, the stored water is continuously discharged through the water collection and infiltration pipes, effectively controlling the groundwater level and keeping the roadbed in the best water content state for a long time. 3. The system is equipped with a multi-stage filtration system consisting of a filter layer and a reverse filter protection layer: the filter layer adopts a composite structure of geotextile and graded crushed stone to effectively block fine particulate matter, and the reverse filter protection layer adopts non-woven geotextile to form a stable filtration interface. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the structure when the main drainage ditch is set in the excavated section of the road in this embodiment.
[0017] Figure 2 This is a schematic diagram of the structure when the main drainage ditch is set in the embankment section in this embodiment.
[0018] Marked in the image: 1-Main drainage ditch, 2-First gravel blind ditch, 3-Second gravel blind ditch, 4-Water collection and seepage pipe, 5-Filter layer, 6-Reverse filter protective layer, 7-Subbase layer, 8-Road structure layer, 9-Improved road base layer. Detailed Implementation
[0019] The present invention will be further described in detail below with reference to specific embodiments. However, it should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.
[0020] Example 1 This embodiment provides a roadbed drainage system with gravel blind ditches suitable for West Africa, combined with... Figure 1-2 As shown, it specifically includes the main drainage ditch 1 located on the surface and the first gravel blind ditch 2 and several second gravel blind ditches 3 located underground; The main drainage ditch 1 is set along the length of the foundation. Specifically, the main drainage ditch 1 is constructed by cast-in-place concrete. The cross-section of the main drainage ditch 1 is rectangular or inverted trapezoidal. When the main drainage ditch 1 is set in an excavated section, a rectangular shape is used; when the main drainage ditch 1 is set in a filled section, an inverted trapezoidal shape is used. Figure 1-2 As shown, the road structure consists of a road structure layer 8 and an improved road base layer 9 from top to bottom.
[0021] The dimensions of the side ditches in the main drainage ditch 1 can be in the form shown in Table 1-2 below, depending on the depth.
[0022] Table 1 shows the combined size information for rectangular main drainage ditches.
[0023] Where a represents the net width of the main drainage ditch cross section, h represents the depth of the main drainage ditch, and c represents the thickness of the C25 cast-in-place concrete used to pour the main drainage ditch.
[0024] Table 2 shows the combined size information for the inverted trapezoidal main drainage ditch.
[0025] Where B represents the top net width of the cross-section of the main drainage ditch, b represents the bottom width of the cross-section of the main drainage ditch, and h represents the depth of the main drainage ditch.
[0026] More specifically, the main drainage ditch 1 is constructed using C25 cast-in-place concrete, and a C10 concrete cushion layer 7 is also installed at the bottom of the main drainage ditch 1.
[0027] When cutting sections, the side ditch is located at the edge of the shoulder and is mainly used to collect rainwater from the road surface and the cut slope. The longitudinal slope is consistent with the main line design, and then the water is discharged into natural ditches or directly to the natural ground. When filling sections, the drainage ditch is located outside the toe of the fill slope and is mainly used to collect rainwater from the road surface and the fill slope. It is 1.5m away from the toe of the roadbed slope and is designed according to the surrounding terrain. Then the water is discharged into natural ditches or directly to the natural ground.
[0028] The first gravel blind ditch 2 is located below the main drainage ditch 1; at least one water collection and seepage pipe 4 is provided inside the first gravel blind ditch 2, and the water collection and seepage pipe 4 is located at the bottom of the first gravel blind ditch 2. Specifically, the gravel filling the first gravel blind drain 2 has a particle size of 5-20mm and a mud content of ≤3%. The cross-section of the first gravel blind drain 2 is rectangular, with a bottom width of 60cm and a depth of 80cm. The water collection and seepage pipe 4 is a perforated U-PVC pipe with an opening rate of 30-40%, an opening diameter of 3-10mm, and a laying slope of 0.2%-0.5%. In this embodiment, two water collection and seepage pipes 4 are arranged side by side at the bottom of the first gravel blind drain 2.
[0029] The second gravel blind drain 3 is installed in the foundation, and several second gravel blind drains 3 are installed inside the first gravel blind drain 2 and are connected to the first gravel blind drain 2, forming a three-dimensional drainage network.
[0030] Specifically, the cross-sectional area of the second gravel blind ditch 3 is smaller than that of the first gravel blind ditch 2. The gravel particles filled in the second gravel blind ditch 3 have a particle size of 5-20mm, a mud content of ≤3%, and a paving slope of 0.2%-0.5%. More specifically, when main drainage ditches 1 are set on both sides of the roadbed, the second gravel blind ditch 3 connects to the first gravel blind ditch 2 on both sides of the road surface, and the second gravel blind ditch 3 has a herringbone slope; specifically, the middle area of the second gravel blind ditch 3 is higher than the end area.
[0031] The second gravel blind ditch 3 has a rectangular cross-section and is set in the roadbed. It has a bottom width of 30cm and a depth of 30cm and is filled with graded gravel. For excavated road sections, the second gravel blind ditch 3 is set every 30m.
[0032] More specifically, a filter layer 5 is provided between the main drainage ditch 1 and the first gravel blind ditch 2. The filter layer 5 is arranged along the outer circumference of the first gravel blind ditch 2 and is a permeable geotextile.
[0033] The permeable geotextile uses Class I non-woven geotextile, with a flat seam for stitching, a joint width of not less than 10cm, and a joint strength of not less than 90% of the specified holding strength.
[0034] The bottom of the first gravel blind ditch 2 is provided with a reverse filter protective layer 6. The reverse filter protective layer 6 is made of non-woven geotextile. The reverse filter protective layer 6 is located outside the filter layer 5 and is located at the bottom and both sides of the first gravel blind ditch 2.
[0035] The filter protective layer 6 adopts a "two-layer fabric-one-membrane" composite geotextile, including an upper non-woven fabric, a geomembrane, and a lower non-woven fabric. The structure is 200g / (0.5-1mm) / 200g, indicating that the unit area mass of the upper non-woven fabric is 200 grams per square meter. The thickness of the middle geomembrane is between 0.5 mm and 1 mm. The unit area mass of the lower non-woven fabric is also 200 grams per square meter.
[0036] The joint is stitched using a hot-melt welding method with a connection width of not less than 10cm. The welding machine generates high-temperature hot air or a wedge-shaped heating plate is used to melt the geomembrane layer at the overlap of the two materials. Then, pressure is immediately applied to allow the molten plastic to cool and fuse together, forming a strong, continuous, and waterproof joint.
[0037] The bottom and lower sides of the first gravel blind drain 2 are covered. The drainage system, through the filter layer 5 and the reverse filter protective layer 6, forms a multi-stage filtration system, effectively preventing soil particles from entering the drainage system and ensuring long-term drainage efficiency.
[0038] During construction, the foundation trench is first excavated, and a reverse filter protective layer 6 is laid. Then, a filter layer 5 is laid on the reverse filter protective layer 6. Gradient crushed stone is then filled to form the first crushed stone blind ditch 2. When filling the first crushed stone blind ditch 2 with graded crushed stone, a water collection and seepage pipe 4 is buried. Then, the filter layer 5 is laid. The second crushed stone blind ditch 3 reduces the step of burying the water collection and seepage pipe 4. The rest of the process is the same as the first crushed stone blind ditch 2. Finally, the main drainage ditch 1 is built to complete the construction of the drainage system.
[0039] When the drainage system is working, surface water is discharged through the main drainage ditch 1, and water inside the roadbed is discharged through the first gravel blind ditch 2 and the second gravel blind ditch 3, eventually converging into the first gravel blind ditch 2, and finally discharged through the water collection and infiltration pipe 4, ensuring the long-term effective operation of the system.
[0040] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.
Claims
1. A roadbed drainage system with gravel blind drains suitable for West Africa, characterized in that, It includes the main drainage ditch (1) located on the surface and the first gravel blind ditch (2) and several second gravel blind ditches (3) located underground. The main drainage ditch (1) is set along the length of the foundation, and the first gravel blind ditch (2) is set below the main drainage ditch (1); at least one water collection and seepage pipe (4) is set inside the first gravel blind ditch (2), and the water collection and seepage pipe (4) is set at the bottom of the first gravel blind ditch (2); The second gravel blind drain (3) is set in the foundation, and several second gravel blind drains (3) are set on the side of the first gravel blind drain (2) and are connected to the first gravel blind drain (2).
2. The roadbed drainage system with gravel blind drains applicable to West Africa according to claim 1, characterized in that, A filter layer (5) is provided between the main drainage ditch (1) and the first gravel blind ditch (2). The filter layer (5) is arranged along the outer circumference of the first gravel blind ditch (2) and is a permeable geotextile.
3. The roadbed drainage system with gravel blind drains applicable to West Africa according to claim 2, characterized in that, The first gravel blind drain (2) is filled with gravel particles with a diameter of 5-20 mm and a mud content of ≤3%.
4. The roadbed drainage system with gravel blind drains applicable to West Africa according to claim 3, characterized in that, The water collection and seepage pipe (4) is a perforated U-PVC pipe with an opening rate of 30-40%, an opening diameter of 3-10mm, and a laying slope of 0.2%-0.5%.
5. The roadbed drainage system with gravel blind drains applicable to West Africa according to claim 3, characterized in that, Two water collection and seepage pipes (4) are arranged side by side at the bottom of the first gravel blind drain (2).
6. The roadbed drainage system with gravel blind drains applicable to West Africa according to claim 3, characterized in that, The bottom of the first gravel blind ditch (2) is also provided with a reverse filter protection layer (6). The reverse filter protection layer (6) is made of non-woven geotextile. The reverse filter protection layer (6) is located outside the filter layer (5). The reverse filter protection layer (6) is located at the bottom and both sides of the first gravel blind ditch (2).
7. The roadbed drainage system with gravel blind drains applicable to West Africa according to claim 1, characterized in that, The cross-sectional area of the second gravel blind drain (3) is smaller than that of the first gravel blind drain (2).
8. The roadbed drainage system with gravel blind drains applicable to West Africa according to claim 7, characterized in that, The gravel particles filled in the second gravel blind drain (3) are 5-20 mm in diameter and have a mud content of ≤3%.
9. The roadbed drainage system with gravel blind drains applicable to West Africa according to claim 6, characterized in that, The distance between adjacent second gravel blind drains (3) is 25m-35m.
10. The roadbed drainage system with gravel blind drains applicable to West Africa according to any one of claims 1-9, characterized in that, The main drainage ditch (1) has a rectangular or inverted trapezoidal cross section. When the main drainage ditch (1) is located in the excavation section, it adopts a rectangular shape, and when the main drainage ditch (1) is located in the fill section, it adopts an inverted trapezoidal shape.