An ecological friendly river drop energy dissipation and revetment integrated structure and method

Abstract

This invention relates to the field of riverbank protection, specifically to an eco-friendly integrated structure and method for riverbank energy dissipation and protection. It includes a concrete overflow weir (2) arranged sequentially from the upstream end to the toe of the existing river channel (1), a multi-graded porous ecological riprap layer (3), an aquatic / wetland plant layer (4), and a toe protection system. The toe protection system consists of intermittently arranged imitation wood piles (5) and locally laid impermeable geomembrane (6). This invention employs a multi-stage energy dissipation system, with the overflow weir as the primary energy dissipator, the ecological riprap layer as the secondary energy dissipator, and the plant layer as the tertiary energy dissipator. Each energy dissipator is sequentially connected, reducing the kinetic energy of the water flow layer by layer, significantly improving energy dissipation efficiency. This effectively resists water scouring under the design flood level, solving the problem of low energy dissipation efficiency in existing riverbank protection, greatly improving the slope's scouring resistance, and reducing soil erosion.

Description

Technical Field

[0001] This invention relates to the field of riverbank protection, specifically to an eco-friendly integrated structure and method for river cascade energy dissipation and bank protection. Background Technology

[0002] Riverbank protection is a core component of river construction. Its core functions are to resist water erosion, prevent riverbank collapse and river channel changes, protect the safety of dikes, farmland and surrounding infrastructure, and at the same time, it is necessary to take into account the coordination and unity of flood control, ecology and landscape functions.

[0003] Currently, conventional riverbank protection construction often uses gabion baskets or concrete block structures. While these structures are sturdy, durable, and resistant to erosion, they have significant ecological and engineering drawbacks: First, gabion baskets and concrete blocks are impermeable structures, which can obstruct the two-way exchange between groundwater and river water, destroying aquatic habitats, leading to a decline in river biodiversity, weakening the river's self-purification capacity, and affecting the survival and reproduction of fish and aquatic plants. Second, these structures have poor landscape effects and cannot achieve a harmonious integration of human elements and nature, especially in urban river applications, where they fail to meet the needs of recreational water activities. Third, they are prone to non-point source pollution, have high maintenance costs, require significant investment of manpower and resources, and are susceptible to structural aging and erosion damage over time, increasing the risks of later stages of the project, making them both uneconomical and posing safety hazards.

[0004] To address the aforementioned issues, some ecological revetment attempts have emerged in existing technologies, such as simply combining riprap with vegetation. However, these solutions are mostly simple combinations of conventional technologies, failing to be precisely designed for the specific harsh environment of fluctuating river levels. Riprap is often of a single particle size, making it difficult to simultaneously meet the needs of energy dissipation, erosion resistance, and vegetation planting. Vegetation planting lacks specificity, making it difficult to adapt to the fluctuating water levels of exposed soil during dry seasons and complete submersion during floods, resulting in low survival rates. Slope toe protection often employs full-coverage geomembranes or continuous piles, which, while improving structural stability, completely block ecological channels, violating the concept of eco-friendliness. Furthermore, the lack of coordinated design among components prevents the formation of a complete multi-level energy dissipation system, resulting in low energy dissipation efficiency and failing to fundamentally solve the ecological damage and engineering defects of traditional revetments. Summary of the Invention

[0005] To address the problems of existing technologies, this invention provides an eco-friendly integrated structure and method for river cascade energy dissipation and bank protection.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An eco-friendly integrated structure for river channel cascade energy dissipation and bank protection includes a concrete overflow weir, a multi-graded porous ecological riprap layer, an aquatic / wetland plant layer, and a slope toe protection system arranged sequentially from the upstream end of the existing river channel to the slope toe; the slope toe protection system consists of intermittently arranged imitation wood piles and locally laid impermeable geomembrane.

[0008] The concrete overflow weir is vertically installed at the upstream end of the existing river channel. The bottom of the weir is seamlessly connected to the river channel foundation, and the top of the weir is connected to the top of the revetment slope. The elevation of the overflow weir crest is slightly higher than the design normal water level of the river channel by 5-10cm and lower than the elevation of the top of the revetment slope by ≥50cm.

[0009] The ecological riprap layer is divided into two layers according to its spatial location. The lower layer, which is the area near the water level fluctuation zone and below, accounts for 60% of the total thickness of the riprap layer. It consists of 1000-1500mm dark gray large stones with a porosity controlled at 30%-35%. The upper layer, which is the area from the top of the slope near the shore to the water level line during the normal water period, accounts for 40% of the total thickness of the riprap layer. It consists of 400-800mm medium and small stones mixed with improved planting soil at a volume ratio of 7:3, with a porosity controlled at 40%-45%.

[0010] The plants in the aquatic / wetland plant layer are selectively planted in the improved soil between the stones in the upper layer of the ecological riprap layer. The plants are wetland / aquatic varieties that are tolerant of flooding and have well-developed root systems. The planting spacing is 0.3 to 0.5 m. The plant roots are intertwined with the stones and soil to form a reinforced soil-stone composite of plant roots, stones, and soil.

[0011] The imitation wood piles are vertically arranged on the outermost side of the bank slope. The imitation wood piles are 200mm in diameter, 4m in length, 2.6m deep in the soil, and 1.4m above the ground, level with the design normal water level of the river during the normal water period. The pile spacing is 0.4m.

[0012] The impermeable geomembrane is partially laid in the area where the water level fluctuates frequently at the toe of the slope behind the gaps of the imitation wood piles. The bottom is connected to the riverbed foundation, and the top extends to the bottom of the lower large stone riprap layer, sandwiched between the riprap layer and the original soil of the slope. The width of the impermeable geomembrane is 1.52m.

[0013] The slope of the revetment is 1:2.5-1:3.

[0014] The construction method for the eco-friendly integrated river cascade energy dissipation and bank protection structure is characterized by the following steps:

[0015] S1. Foundation Treatment: Clean and level the existing weir foundation and bank slope at the upstream end of the river channel to ensure that the foundation bearing capacity meets the design requirements.

[0016] S2. Overflow weir construction: Concrete overflow weirs are poured at the upstream end of the existing river channel, and the weir crest elevation is controlled to be slightly higher than the design normal water level by 5-10cm and lower than the slope crest elevation by ≥50cm. The weir body is seamlessly connected to the river channel foundation.

[0017] S3. Laying of ecological riprap layer: Lay the riprap layer in layers according to the multi-gradation requirements. First, lay the lower layer of 1000-1500mm large stones on the water-near side of the slope toe until it is stable. Then, lay the upper layer of 400-800mm medium and small stones mixed with improved planting soil on the near-shore side.

[0018] S4. Construction of the slope toe protection system: Vertical imitation wood piles are driven into the outermost part of the bank slope toe, with the pile diameter controlled at 200mm, length at 4m, depth in the soil at 2.6m, top height at 1.4m above the ground, and pile spacing at 0.4m. The imitation wood piles are wrapped with impermeable geomembrane at the ground height. Composite impermeable geomembrane is laid locally in the slope toe area behind the gaps between the imitation wood piles, with a laying width of 1.5-2m. The bottom of the membrane is connected to the riverbed foundation, and the top extends to the bottom of the lower riprap layer. The upper layer is fixed with large stones for weight.

[0019] S5. Planting: Plant flood-tolerant and well-developed wetland / aquatic plants in the improved soil between the stones in the upper layer of the ecological riprap layer at a spacing of 0.3 to 0.5m. Flood-tolerant varieties extend to the pores on the water side of the lower riprap layer to form an aquatic / wetland plant layer.

[0020] S6. Acceptance and Maintenance: Conduct construction quality acceptance of each structural component, and carry out post-construction maintenance of the plant layer to ensure plant survival rate and overall structural stability.

[0021] In step S3, the improved planting soil is made by mixing humus, river sand and organic fertilizer in a volume ratio of 5:3:2. In step S5, the wetland / aquatic plants are one or more of the following: calamus, reed, loosestrife and cattail.

[0022] In step S4, static pressure method is used when driving imitation wood piles to avoid disturbing the slope toe foundation. Before laying the impermeable geomembrane, the original soil of the slope is compacted to a degree of ≥90%.

[0023] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention adopts a multi-stage energy dissipation system, with the overflow weir as the primary energy dissipation body, the ecological riprap layer as the secondary energy dissipation body, and the vegetation layer as the tertiary energy dissipation body. Each energy dissipation body is connected in sequence, reducing the kinetic energy of the water flow layer by layer, which significantly improves the energy dissipation efficiency. It can effectively resist the scouring of water flow under the design flood level, solve the problem of low energy dissipation efficiency of existing bank protection, greatly improve the scouring resistance of the bank slope, and reduce soil erosion.

[0024] All components of this invention are precisely designed around the specific harsh environment of the river water level fluctuation zone, achieving full parameter adaptability and selectivity: the overflow weir elevation adapts to the water level control requirements, the riprap gradation adapts to the different scouring characteristics of the upper and lower parts of the water level fluctuation zone, the plant species adapt to the growth environment of water level fluctuation, and the parameters of the imitation wood piles and geomembrane adapt to the dual requirements of slope toe protection and ecological preservation.

[0025] The multi-graded ecological riprap layer ensures slope stabilization while enabling bidirectional exchange between groundwater and river water. The plant layer and riprap layer form a reinforced soil-rock composite, enhancing structural stability while improving biodiversity and the river's self-purification capacity. The slope toe protection system adopts an innovative design of "interspersed imitation wood piles + local geomembrane," which, while ensuring slope toe stability and preventing erosion of the original soil, preserves ecological channels and micro-exchange space for water, avoiding the ecological isolation problem of traditional full-coverage protection, and truly achieving "protection without sealing off, and bank stabilization without damaging the ecology."

[0026] Meanwhile, the construction method of this invention is simple and feasible, with close connection between each process. It adopts static pressure method to drive imitation wood piles and layered riprap layer laying, which reduces the disturbance to the river foundation and surrounding environment. The construction quality is easy to control, the later maintenance cost is low, and the economic and social benefits are significant. Attached Figure Description

[0027] Figure 1 This is a cross-sectional structural diagram of the integrated structure of the present invention;

[0028] In the diagram: 1 - Existing river channel, 2 - Concrete overflow weir, 3 - Ecological riprap layer, 4 - Aquatic / wetland plant layer, 5 - Imitation wood pile, 6 - Impermeable geomembrane, 7 - Water level line. Detailed Implementation

[0029] The present invention will be further described in detail below through embodiments. These embodiments are only used to illustrate the present invention and do not limit the scope of the present invention.

[0030] An eco-friendly integrated structure for river channel energy dissipation and bank protection includes a concrete overflow weir, a multi-graded porous ecological riprap layer, an aquatic / wetland plant layer, and a slope toe protection system arranged sequentially from the upstream end of the existing river channel to the slope toe. The slope toe protection system consists of intermittently arranged imitation wood piles and locally laid impermeable geomembranes. Each component is designed to adapt to the river channel's water level fluctuation zone, forming a multi-stage energy dissipation, synergistic bank stabilization, and ecologically compatible organic whole.

[0031] The concrete overflow weir is vertically arranged at the upstream end of the existing river channel. The bottom of the weir body is closely connected to the river channel foundation, and the top of the weir body is naturally connected to the top of the revetment slope. The elevation of the overflow weir crest is slightly higher than the design normal water level of the river channel by 5-10cm and lower than the elevation of the top of the revetment slope by ≥50cm. This not only stabilizes the normal water level but also allows floodwaters exceeding the design water level to overflow and discharge in an orderly manner, achieving primary energy dissipation and flow regulation.

[0032] The multi-graded porous ecological riprap layer is fully laid on the gentle slope of the revetment, extending from the top of the slope behind the overflow weir to the upper part of the imitation wood piles at the foot of the slope. The ecological riprap layer is divided into upper and lower layers according to its spatial location.

[0033] The stratified particle size is quantitatively determined using the formula for calculating the critical particle size for erosion resistance of riprap on riverbank slopes, as follows:

[0034]

[0035] In the formula: The critical erosion resistance diameter (m) of paving stones is the smallest paving stone diameter that can resist water erosion. The water flow velocity (m / s) in the corresponding area; The specific gravity of the stone is taken as 2.65; Porosity of the rubble layer; The acceleration due to gravity is taken as 9.8 m / s².

[0036] The lower layer, which is the area below the water level fluctuation zone on the near side, accounts for 60% of the total thickness of the riprap layer. Considering the hydrological characteristics of the design flood flow velocity of 2.0-2.5 m / s in this area, the critical value D is calculated to be approximately 0.98 m based on the above formula. This means that the minimum riprap particle size that can resist water erosion is 0.98 m. In practice, large stones of 1000-1500 mm (1.0-1.5 m) are used, slightly larger than the calculated critical value (0.98 m), to ensure the structure's erosion resistance during flood season.

[0037] Large, dark gray stones (1000-1500mm) are used, scattered until stable, with a porosity controlled at 30%-35%; the focus is on erosion resistance and secondary energy dissipation. The upper layer, from the top of the near-shore slope to above the water level during the normal water period, accounts for 40% of the total thickness of the riprap layer. It consists of small and medium-sized stones (400-800mm) mixed with improved planting soil at a volume ratio of 7:3, with a porosity controlled at 40%-45%; this provides anchoring space and growth medium for plant planting. The entire ecological riprap layer is permeable, enabling bidirectional exchange between groundwater and river water.

[0038] The aquatic / wetland plant layer is selectively planted in the improved soil between the stones in the upper layer of the ecological riprap layer. Flood-tolerant plant varieties are selected and extend into the pores near the water surface of the lower riprap layer. The planting area covers the entire slope from the water level to the top during the normal water period. The plants are flood-tolerant wetland / aquatic varieties with well-developed root systems, planted at intervals of 0.3–0.5 m. The plant roots intertwine with the stones and soil, forming a reinforced soil-rock composite. This significantly improves the slope's shear strength and erosion resistance, while simultaneously achieving three levels of energy dissipation and ecological restoration.

[0039] The imitation wood piles are vertically arranged on the outermost side of the bank slope toe, serving as the first mechanical protective barrier for the slope. The imitation wood piles are 200mm in diameter, 4m in length, 2.6m deep in the soil, and 1.4m above the ground, level with the design normal water level during the river's normal water period. The pile spacing is 0.4m. The 0.4m spacing is the optimal value for coordinated balance after dual calculation using the imitation wood pile group overturning safety factor calculation formula and the slope toe water flow eddy critical spacing calculation formula, combined with the passage requirements of small aquatic organisms.

[0040] Formula for calculating the overturning safety factor of a group of imitation wooden piles:

[0041]

[0042] In the formula: To ensure the overturning safety factor of the simulated wooden pile group, this invention requires ≥1.5; The overturning moment (kN·m); The overturning moment is (kN·m). The weight of the pile (kN); The horizontal distance (m) from the center of gravity of the pile to the overturning point; The passive earth pressure on the slope (kN); The height (m) from the point of application of passive earth pressure to the point of overturning. The flow-side pressure (kN) at the design flood level. The height (m) from the point of application of the water flow side pressure to the point of overturning.

[0043] Formula for calculating the critical distance of the eddy current at the toe of the slope:

[0044]

[0045] In the formula: The critical spacing (m) for avoiding eddy currents in the slope toe pile body; Design flood velocity (m / s); The design flood level is determined by the water depth at the toe of the slope (m). The acceleration due to gravity is taken as 9.8 m / s².

[0046] Based on the above formula, the overturning safety factor of the simulated wood pile group with a spacing of 0.4m is calculated. Critical spacing of water flow eddies at the toe of the slope The spacing between the piles is greater than the required spacing between the piles, which not only meets the structural stability specifications but also prevents water flow from impacting the piles and creating local eddies that exacerbate slope erosion. It also meets the minimum passage width requirement of 0.3 to 0.4 meters for small aquatic organisms. The ground-level portion of the imitation wood piles is wrapped with an impermeable geomembrane to enhance protection and extend service life.

[0047] The exposed portions of the simulated wooden piles are wrapped with impermeable geomembranes to enhance protection and extend service life. These impermeable geomembranes are anti-aging and puncture-resistant composite geomembranes. They are partially laid in the area behind the gaps between the simulated wooden piles, in the frequently fluctuating water level zone at the toe of the slope. The bottom connects to the riverbed foundation, and the top extends to the bottom of the lower layer of large riprap, sandwiched between the riprap layer and the original slope soil. The impermeable geomembrane is 1.52m wide, which is 1.52 times the eddy current scouring depth at the toe of the slope under the design flood level. This is the minimum effective width to prevent erosion of the original slope soil, and it forms a protective zone-ecological channel interval with the gaps between the simulated wooden piles. This prevents the slope soil from being eroded by water flow while preserving the ecological channel and micro-exchange space with the water body.

[0048] The slope of the revetment is 1:2.5 to 1:3.

[0049] An eco-friendly construction method for an integrated river cascade energy dissipation and bank protection structure includes the following steps:

[0050] S1. Foundation Treatment: Clean and level the existing weir foundation and bank slope at the upstream end of the river channel to ensure that the foundation bearing capacity meets the design requirements.

[0051] S2. Overflow weir construction: Concrete overflow weirs are poured at the upstream end of the existing river channel. C30 concrete is used for on-site pouring and compaction. The weir crest elevation is controlled to be 5-10cm higher than the design normal water level and ≥50cm lower than the slope crest elevation. The weir body is seamlessly connected to the river channel foundation.

[0052] S3. Ecological riprap layer laying: The riprap layer is laid in layers according to the multi-gradation requirements. First, lay the lower layer of 1000-1500mm dark gray large stones on the water-near side of the slope toe. The filling is done manually and mechanically until it is stable. Then, lay the upper layer of 400-800mm medium and small stones mixed with improved planting soil on the near-shore side to ensure that the upper and lower layers are tightly connected and the overall porosity and permeability meet the design requirements.

[0053] S4. Construction of the slope toe protection system: Vertical imitation wood piles are driven into the outermost part of the bank slope toe to avoid disturbing the slope toe foundation. The pile diameter is controlled to be 200mm, length is 4m, depth is 2.6m, top is 1.4m above the ground, and pile spacing is 0.4m. The imitation wood piles are wrapped with impermeable geomembrane above the ground. Composite impermeable geomembrane (6) is laid locally in the slope toe area behind the gaps of the imitation wood piles. The laying width is 1.5-2m. The bottom of the membrane is connected to the river channel foundation, and the top extends to the bottom of the lower riprap layer. The upper layer is fixed with large stones for weight.

[0054] S5. Planting: Plant flood-tolerant and well-developed wetland / aquatic plants in the improved soil between the stones in the upper layer of the ecological riprap layer at a spacing of 0.3 to 0.5m. Flood-tolerant varieties extend to the pores on the water side of the lower riprap layer to form an aquatic / wetland plant layer.

[0055] S6. Acceptance and Maintenance: Conduct construction quality acceptance of each structural component, and carry out post-construction maintenance of the plant layer to ensure plant survival rate and overall structural stability.

[0056] In step S3, the improved planting soil is made by mixing humus, river sand and organic fertilizer in a volume ratio of 5:3:2. When laying it, the upper and lower layers are tightly connected, and the overall porosity and water permeability meet the design requirements.

[0057] In step S5, the wetland / aquatic plant is one or more combinations of calamus, reed, loosestrife, and cattail.

[0058] In step S4, static pressure method is used when driving imitation wood piles to avoid disturbing the slope toe foundation. Before laying the impermeable geomembrane, the original soil of the slope is compacted to a degree of ≥90%.

[0059] Example 1

[0060] An eco-friendly integrated structure for riverbank energy dissipation and revetment was applied to Section II of the Shenzhen Reservoir Interception and Drainage Project on the Shawan River. The river's design normal water level is 1.4m, design flood level is 2.8m, and design flood velocity is 2.5m / s. The slope toe soil is silty clay with a clay content of 25% and an erosion resistance coefficient of 0.8×10⁻⁻⁻⁻⁶. 6 m² / s.

[0061] The integrated structure includes a concrete overflow weir 2, a multi-graded porous ecological riprap layer 3, an aquatic / wetland plant layer 4, and a slope toe protection system arranged sequentially from the water-facing end of the existing river channel 1 to the slope toe. The slope toe protection system consists of intermittently arranged imitation wood piles 5 and locally laid impermeable geomembrane 6, with a bank slope of 1:3.

[0062] The concrete overflow weir 2 is made of C30 concrete and is vertically installed at the upstream end of the existing river channel 1. The bottom of the weir is seamlessly connected to the river channel foundation, and the top of the weir is connected to the top of the revetment slope. The weir top elevation is 1.48m, which is slightly higher than the design normal water level by 0.08m and lower than the slope top elevation by 0.6m.

[0063] A multi-graded, porous ecological riprap layer 3 is fully laid on the gentle slope of the revetment, extending from the rear edge of the overflow weir 2 to the top of the imitation wood piles 5 at the foot of the slope. It is divided into two layers: the lower layer is the area below the water level fluctuation zone on the near side, accounting for 60% of the total thickness. It uses 1000-1500mm dark gray large stones, which are thrown until they are stable, with a porosity of 32%; the upper layer is the area from the top of the near-bank slope to the water level line during the normal water period, accounting for 40% of the total thickness. It uses 400-800mm medium and small stones mixed with improved planting soil at a volume ratio of 7:3. The improved planting soil is a mixture of humus, river sand and organic fertilizer at a ratio of 5:3:2, with a porosity of 42%.

[0064] Aquatic / wetland plant layer 4 is planted in the improved soil between the stones in the upper layer of ecological riprap layer 3. Flood-resistant calamus extends to the pores on the water-side of the lower riprap layer. The planting area covers the entire area of ​​the revetment slope from 1.4m to the top of the slope. The planted varieties are a combination of calamus, reeds, and loosestrife, with a planting spacing of 0.4m. The roots, stones, and soil form a reinforced soil-stone composite.

[0065] The imitation wood piles 5 are vertically arranged on the outermost side of the slope toe, with a diameter of 200mm, a length of 4m, a soil depth of 2.6m, and a top height of 1.4m above the ground, level with the design normal water level. The pile spacing is 0.4m. According to calculations, the overturning safety factor of the imitation wood pile group is 1.55, and the sliding safety factor is 1.42. The part above the ground is wrapped with an impermeable geomembrane. The impermeable geomembrane 6 is a composite geomembrane, which is partially laid in the slope toe area behind the gaps of the imitation wood piles 5. Before laying, the original soil compaction degree of the slope is 92%, and the laying width is 1.8m, which is 1.8 times the eddy current scouring depth of 1.0m at the slope toe under the design flood level of this project. The bottom of the membrane is connected to the river channel foundation, and the top extends to the bottom of the lower riprap layer. The upper layer is fixed with large stones for weight.

[0066] Example 2

[0067] The construction method of the integrated structure in Embodiment 1 above includes the following steps:

[0068] S1. Foundation treatment: Clean and level the foundation and bank slope of the existing river channel 1 at the water-facing end, remove silt and miscellaneous soil, and use a frog-type rammer to compact the foundation to a compaction degree of ≥90% to ensure the foundation bearing capacity is ≥150kPa.

[0069] S2. Overflow weir construction: Set up formwork at the water-facing end of the existing river channel 1 according to the design elevation, and use C30 commercial concrete to pour concrete overflow weir 2 on site. Vibrate and compact it, control the weir top elevation to 1.48m, and cover it with geotextile and water it for 7 days after pouring.

[0070] S3. Laying of ecological riprap layer: First, use an excavator in conjunction with manual labor to fill the lower layer of 1000-1500mm large stones on the water-near side of the slope toe until it is stable. Then, lay a mixed layer of 400-800mm medium and small stones and improved planting soil on the upper side near the bank. The improved planting soil is a mixture of humus, river sand and organic fertilizer in a ratio of 5:3:2. When laying, ensure that the upper and lower layers are tightly connected.

[0071] S4. Construction of the slope toe protection system: The static pressure method is used to vertically drive imitation wood piles 5 on the outermost side of the slope toe, controlling the pile spacing to 0.4m to avoid disturbing the slope toe foundation. The imitation wood piles 5 are tightly wrapped with impermeable geomembrane at the ground level. A composite impermeable geomembrane 6 is laid in the slope toe area behind the gaps of the imitation wood piles 5, with a laying width of 1.8m and a membrane overlap width of 0.3m. After laying, large stones are used to weigh down and fix the top and edges of the membrane.

[0072] S5. Planting: In the improved soil between the stones in the upper layer of the ecological riprap layer 3, plant calamus, reeds and loosestrife at a spacing of 0.4m. The flood-resistant calamus extends to the pores on the water side of the lower riprap layer. Water and keep moist in time after planting.

[0073] S6. Acceptance and maintenance: Conduct a comprehensive acceptance inspection of the dimensions and construction quality of each structural component. After the inspection is passed, maintain the plant layer. Water once a week and fertilize once a month for the first 3 months. Remove weeds in a timely manner to ensure that the plant survival rate is ≥95%.

[0074] After one year of monitoring following the implementation of the project, no erosion or collapse of the riverbanks was observed, demonstrating its ability to effectively resist water flow erosion at the design flood level. The number of aquatic organisms in the river increased from 18 to 25, representing a 38.9% increase in biodiversity. The removal rates of COD and ammonia nitrogen in the river increased by 28% and 32%, respectively, significantly enhancing its self-purification capacity. The subsequent maintenance cost was 8 yuan / ㎡·year, a 40.7% reduction compared to the original gabion revetment cost of 13.5 yuan / ㎡·year. At the same time, it created a pleasant waterfront recreational space, achieving multiple objectives of flood control, ecology, and landscape.

Claims

1. An eco-friendly integrated structure for river cascade energy dissipation and bank protection, characterized in that, It includes a concrete overflow weir (2) arranged sequentially from the water-facing end to the toe of the existing river channel (1), a multi-graded and porous ecological riprap layer (3), an aquatic / wetland plant layer (4), and a slope toe protection system; the slope toe protection system consists of intermittently arranged imitation wood piles (5) and locally laid impermeable geomembrane (6).

2. The eco-friendly integrated river cascade energy dissipation and bank protection structure according to claim 1, characterized in that, The concrete overflow weir (2) is vertically installed at the upstream end of the existing river channel (1). The bottom of the weir body is seamlessly connected to the river channel foundation, and the top of the weir body is connected to the top of the revetment slope. The top elevation of the overflow weir (2) is slightly higher than the normal design water level of the river channel by 5-10cm and lower than the top elevation of the revetment slope by ≥50cm.

3. The eco-friendly integrated structure for river cascade energy dissipation and bank protection as described in claim 1, characterized in that, The ecological riprap layer (3) is divided into two layers according to its spatial location: the lower layer is the area below the water level fluctuation zone on the near side, accounting for 60% of the total thickness of the riprap layer, and uses 1000-1500mm dark gray large stones with a porosity controlled at 30%-35%; the upper layer is the area from the top of the near bank slope to the water level line during the normal water period, accounting for 40% of the total thickness of the riprap layer, and uses 400-800mm medium and small stones mixed with improved planting soil at a volume ratio of 7:3, with a porosity controlled at 40%-45%.

4. The eco-friendly integrated structure for river cascade energy dissipation and bank protection as described in claim 1, characterized in that, The plants in the aquatic / wetland plant layer (4) are selectively planted in the improved soil material between the stones in the upper layer of the ecological riprap layer. The plants are wetland / aquatic varieties that are tolerant to flooding and have well-developed root systems. The planting spacing is 0.3 to 0.5 m. The plant roots are intertwined with the stones and soil to form a reinforced soil-stone composite of plant roots, stones and soil.

5. The eco-friendly integrated structure for river cascade energy dissipation and bank protection as described in claim 1, characterized in that, The imitation wood piles (5) are vertically arranged on the outermost side of the bank slope. The imitation wood piles (5) have a diameter of 200mm, a length of 4m, a soil depth of 2.6m, a top height of 1.4m above the ground and are level with the design normal water level of the river during the normal water period, and a pile spacing of 0.4m.

6. The eco-friendly integrated river cascade energy dissipation and bank protection structure according to any one of claims 1-5, characterized in that, The impermeable geomembrane (6) is partially laid in the area where the water level fluctuates frequently at the toe of the slope behind the gap of the imitation wood pile (5). The bottom is connected to the riverbed foundation, and the top extends to the bottom of the lower large stone riprap layer, sandwiched between the riprap layer and the original soil of the slope. The impermeable geomembrane (6) is laid with a width of 1.52m.

7. The eco-friendly integrated structure for river cascade energy dissipation and bank protection as described in claim 6, characterized in that, The slope of the revetment is 1:2.5-1:

3.

8. A construction method for an eco-friendly integrated river cascade energy dissipation and bank protection structure according to claim 7, characterized in that, Includes the following steps: S1. Foundation treatment: Clean and level the foundation and bank slope of the weir at the water-facing end of the existing river channel (1) to ensure that the foundation bearing capacity meets the design requirements; S2. Overflow weir construction: Concrete overflow weir (2) is poured at the water-facing end of the existing river channel (1). The elevation of the weir crest is controlled to be 5-10cm higher than the design normal water level and ≥50cm lower than the slope crest elevation. The weir body is seamlessly connected to the river channel foundation. S3. Laying of ecological riprap layer: Lay the riprap layer in layers according to the multi-gradation requirements. First, lay the lower layer of 1000-1500mm large stones on the water-near side of the slope toe until it is stable. Then, lay the upper layer of 400-800mm medium and small stones mixed with improved planting soil on the near-shore side. S4. Construction of the slope toe protection system: Vertical imitation wood piles (5) are driven into the outermost part of the bank slope toe. The pile diameter is controlled to be 200mm, length is 4m, depth is 2.6m, top is 1.4m above the ground, and pile spacing is 0.4m. The imitation wood piles are wrapped with impermeable geomembrane at the ground. Composite impermeable geomembrane (6) is laid locally in the slope toe area behind the gap of the imitation wood piles (5). The laying width is 1.5-2m. The bottom of the membrane is connected to the river channel foundation, and the top extends to the bottom of the lower riprap layer. The upper layer is fixed by heavy weight of large stones. S5. Planting: In the improved soil between the stones in the upper layer of the ecological riprap layer, plant flood-tolerant and well-developed wetland / aquatic plants at a spacing of 0.3 to 0.5 m. Flood-tolerant varieties extend to the pores on the water side of the lower riprap layer to form an aquatic / wetland plant layer (4). S6. Acceptance and Maintenance: Conduct construction quality acceptance of each structural component, and carry out post-construction maintenance of the plant layer to ensure plant survival rate and overall structural stability.

9. The construction method of the eco-friendly integrated river cascade energy dissipation and bank protection structure according to claim 8, characterized in that, In step S3, the improved planting soil is made by mixing humus, river sand and organic fertilizer in a volume ratio of 5:3:

2. In step S5, the wetland / aquatic plants are one or more of the following: calamus, reed, loosestrife and cattail.

10. The construction method of the eco-friendly integrated river cascade energy dissipation and bank protection structure according to claim 9, characterized in that, In step S4, static pressure method is used when driving imitation wood piles (5) to avoid disturbing the slope toe foundation. Before laying the impermeable geomembrane (6), the original soil of the slope is compacted and the compaction degree is ≥90%.

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