Reservoir bank slope reinforcing method based on root system-engineering structure coupling effect

Abstract

The invention relates to the technical field of slope reinforcement, and aims to solve the problems that in the prior art, a traditional reinforcement structure hinders plant growth and is poor in ecological benefit, the instant stability requirement of a high and steep slope is difficult to meet by purely depending on root system soil fixation, a slope surface layer is prone to slippage, and the simple superposition synergistic effect of a traditional rigid structure and ecological reinforcement is insufficient. The reservoir bank slope reinforcing method based on the root system-engineering structure coupling effect comprises the following steps that S1, slope pretreatment is conducted; s2, constructing a three-dimensional geonet pad; s3, planting matrix construction; s4, vegetation establishment and maintenance; s5, later monitoring and maintenance; the deep taproot system plants, the shallow creeping system plants and the three-dimensional geonet pad form a composite reinforcing system, the anti-scouring performance of the side slope is improved, the stability of the side slope is enhanced, the long-term durability is better, the ecological restoration and landscape effects are achieved, the construction and maintenance cost is reduced, and the environmental adaptability is higher.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of slope reinforcement, in particular to a bank slope reinforcement method based on root-structure coupling. BACKGROUND

[0002] In water conservancy projects, the stability of the bank slope directly affects the safe operation of the reservoir. Traditional slope reinforcement methods such as anti-slide piles, anchor rods, retaining walls, etc. mainly rely on rigid structure support, which can improve stability in the short term, but has problems such as high construction cost, large ecological damage, and poor long-term adaptability.

[0003] In recent years, reinforcement techniques based on ecological engineering (such as vegetation slope protection and root soil stabilization) have attracted attention due to their environmental friendliness and sustainability. Although ecological engineering reinforcement techniques have environmental advantages, relying solely on vegetation roots cannot meet the immediate stability needs of high and steep slopes, and existing "rigid-flexible" composite solutions often only involve simple superposition, lacking systematic optimization of root distribution, support structure, and soil stress field synergy. In particular, in the special environment of frequent changes in reservoir water level, the root-soil interface is easily weakened by wetting and drying cycles, making it difficult to maintain the reinforcement effect.

[0004] The existing technology still has the following key defects: 1. Traditional reinforcement structures (such as concrete slope protection) hinder plant growth, with poor ecological benefits; 2. Relying solely on root soil stabilization cannot meet the immediate stability needs of high and steep slopes, and the surface soil of the slope is prone to sliding under rainwater erosion and water level changes; 3. The simple superposition of traditional rigid structures and ecological reinforcement (such as "anti-slide pile + vegetation") lacks systematic coupling design, and fails to fully utilize the synergistic effect of the "rigid-flexible" composite system, resulting in insufficient synergy and poor long-term stability. SUMMARY

[0005] The present application aims to provide a bank slope reinforcement method based on root-structure coupling to solve the problems of traditional reinforcement structures hindering plant growth, poor ecological benefits, relying solely on root soil stabilization to meet the immediate stability needs of high and steep slopes, surface soil sliding, and insufficient synergy of traditional rigid structures and ecological reinforcement, resulting in poor long-term stability.

[0006] The present application is implemented by using the following technical solutions: The present application provides a bank slope reinforcement method based on root-structure coupling, comprising the following steps: S1: slope pretreatment; S2: three-dimensional geotechnical net mat construction; S3: planting substrate construction; S4: Vegetation establishment and maintenance; Deep-rooted and shallow-rooted plants are mixed and sown on the planting substrate, and the plants are maintained. As the plant roots grow, they gradually penetrate the mesh of the geonet and form a mechanical interlock with the slope soil. The roots of the deep-rooted and shallow-rooted plants form a three-dimensional root network. The deep-rooted and shallow-rooted plants and the three-dimensional geonet form a composite reinforcement system. S5: Post-monitoring and maintenance.

[0007] As a preferred technical solution: The ratio of deep taproot plants to shallow creeping root plants is 3:2.

[0008] As a preferred technical solution: Tall fescue is used for plants with deep taproot systems, while bermudagrass is used for plants with shallow creeping roots.

[0009] As a preferred technical solution: The sowing density for deep taproot plants is 15-20 g / m², and the sowing density for shallow creeping root plants is 10-15 g / m².

[0010] As a preferred technical solution: The planting substrate is formulated as follows: 70% local loam, 8% water-retaining agent, 2% slow-release fertilizer, 15% organic matter, and 5% soil conditioner.

[0011] As a preferred technical solution: Among them, water-retaining agents may include, but are not limited to, polyacrylamide; slow-release fertilizers may include, but are not limited to, NPK=15-15-15 compound fertilizers; organic matter may include, but is not limited to, humus; and soil conditioners may include, but are not limited to, diatomaceous earth.

[0012] As a preferred technical solution: Slow-release fertilizer is a type of compound fertilizer that can be produced as acidic, alkaline, or neutral compound fertilizers based on different raw material components. It is used to adjust the pH value of the planting substrate, ideally between 6.0 and 7.5. Slow-release fertilizers are readily available for purchase in the market.

[0013] As a preferred technical solution: S1 specifically includes: Remove loose soil, gravel, and vegetation roots from the slope surface, and repair any uneven areas to ensure that the slope flatness error does not exceed ±5cm. The slope is compacted in layers using a road roller; Dig intercepting ditches at the top of the slope and drainage ditches at the bottom of the slope to prevent surface runoff from eroding the slope surface.

[0014] As a preferred technical solution: When trimming the slope, ensure that the slope ratio is ≤1:1.5.

[0015] As a preferred technical solution: The intercepting ditch and drainage ditch have dimensions of 30cm×30cm and are constructed using M7.5 mortar-grouted rubble masonry.

[0016] As a preferred technical solution: S2 specifically includes: Three-dimensional geonets are laid from the top of the slope downwards, with adjacent geonets overlapping and anchored to the slope. Multiple rows of drainage holes are set on the slope, and a permeable pipe is inserted into each drainage hole.

[0017] As a preferred technical solution: The mesh size of geonets ranges from 5 to 10 cm, and the tensile strength of geonets is ≥3 kN / m; When adjacent mesh mats overlap, the overlap length should be ≥10cm.

[0018] As a preferred technical solution: The mesh mattress is anchored to the slope using U-shaped nails. After anchoring, the linear anchoring force of the U-shaped nails is tested. If the linear anchoring force is ≥0.3kN / m, the anchoring is qualified. If the linear anchoring force is <0.3kN / m, the anchoring is unqualified and further anchoring is required until the anchoring is qualified.

[0019] As a preferred technical solution: S3 specifically includes: Use a mechanical mixer to thoroughly mix the planting substrate, and then use a hydroseeder to evenly spray the substrate onto the netting.

[0020] As a preferred technical solution: When spraying the planting substrate, the total thickness of the planting substrate should be 10-15cm.

[0021] As a preferred technical solution: The injection pressure is controlled between 0.4 and 0.6 MPa.

[0022] As a preferred technical solution: When spraying the substrate, it can be done in two or more stages. If it is sprayed in two stages, the first stage should be 6 cm thick, and after allowing it to settle naturally for 24 hours, the remaining 4 cm should be sprayed.

[0023] As a preferred technical solution: S4 specifically includes: Mix deep taproot plants and shallow creeping root plants, and add rhizobium inoculant during sowing; Immediately after sowing, cover the seeds with non-woven fabric and secure the fabric in place. Irrigation and fertilization should be carried out during the maintenance period.

[0024] As a preferred technical solution: The non-woven fabric is fixed with bamboo sticks, which are then inserted into the planting substrate at 1m x 1m intervals.

[0025] As a preferred technical solution: For the first 30 days of the maintenance period, spray water once a day, with a water volume of 8-10mm each time; spray water once every 2 days from days 31 to 60; spray water twice a week from days 61 to 90; and apply top dressing once a month, using compound fertilizer (NPK=20-10-10) at 5g / ㎡.

[0026] As a preferred technical solution: Regularly monitor soil moisture content to maintain it within the range of 15-25%, and adjust irrigation plans according to weather conditions.

[0027] As a preferred technical solution: S5 specifically includes: Vegetation cover is measured quarterly, and the results are calculated using image analysis software after taking photos with a digital camera. The shear strength index of the reinforced soil is determined every six months by in-situ direct shear test. Reseeding is carried out once each spring and autumn, with the reseeding amount being 15% of the original seeding amount. When the netting is found to be damaged, it is repaired in a timely manner, and the repaired area is 20cm larger than the perimeter of the damaged area.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: (1) Significantly improved erosion resistance: Traditional ecological slope protection mainly relies on single vegetation or simple geotechnical materials, which have limited resistance to water erosion. However, this invention uses a three-dimensional root network of tall fescue (deep straight root system) and bermudagrass (shallow creeping root system) combined with the mechanical reinforcement of three-dimensional geonet, so that the erosion of the slope under the condition of 2m water level change is only 18% of that of the traditional method, and the slope erosion resistance is increased by more than 5 times.

[0029] (2) Enhanced structural stability: Ordinary vegetation slope protection is prone to surface slippage due to rainfall or water level fluctuations in the early stage of root development. However, this invention optimizes the three-dimensional mesh laying process (precisely controlling the overlap width, U-shaped nail fixing spacing and drainage hole arrangement) to form a stable embedded structure between the mesh and the slope soil, which is significantly better than the single protection method of using only vegetation or only geonet. The slope stability is enhanced and the slope surface is not easy to slip.

[0030] (3) Superior long-term durability: In existing technologies, pure vegetation slope protection is prone to degradation due to drought or freeze-thaw cycles, while pure engineering structure slope protection (concrete frame) lacks ecological function. This invention achieves a synergistic effect between vegetation and netting, with the root system penetrating the netting to form a biomechanical composite, which has a protection life of 12-15 years. It also has ecological restoration and landscape effects, resulting in good ecological benefits.

[0031] (4) Reduced construction and maintenance costs: Compared with traditional grid beams or concrete slope protection, the present invention adopts standardized construction technology, reducing labor input by more than 30%; only seasonal reseeding and local repair of netting are required in the later stage, and the maintenance cost is reduced by 40% compared with conventional engineering measures.

[0032] (5) Stronger environmental adaptability: By optimizing the substrate ratio and vegetation combination, the present invention can still maintain a vegetation coverage rate of more than 90% under harsh environments such as drought, water level fluctuation and freeze-thaw cycles, while the coverage rate of ordinary ecological slope protection is usually less than 60% under the same conditions. Attached Figure Description

[0033] Figure 1 This is a flowchart of the reservoir bank slope reinforcement method based on root system-engineering structure coupling as described in this invention.

[0034] Figure 2 This is a schematic diagram of the ecological-structural reinforcement measures described in this invention.

[0035] Figure 3 This is a stability calculation model for unprotected slopes and ecologically protected slopes.

[0036] Figure 4 This is a comparison chart showing the variation patterns of local safety factors between unprotected slopes and ecologically protected slopes.

[0037] Figure 5 This is a comparison chart showing the calculation results of the local critical slip surface of an unprotected slope and an ecologically protected slope. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1 like Figure 1 As shown in the figure, this embodiment proposes a reservoir bank slope reinforcement method based on the coupling effect of root system and engineering structure, including the following steps: S1: Slope pretreatment; The loose soil, gravel, and vegetation roots on the slope were thoroughly removed using a combination of mechanical and manual methods. Uneven areas were repaired to ensure that the slope flatness error did not exceed ±5cm. A 12-15t roller was used to compact the slope in layers, with each layer compacted to a thickness of 20-25cm, ultimately achieving an overall slope compaction of 87%±2%. A water interception ditch was excavated at the top of the slope, and a drainage ditch was excavated at the bottom of the slope. The ditch dimensions were 30cm×30cm, and it was constructed using M7.5 mortar-grouted rubble masonry to prevent surface runoff from eroding the slope.

[0040] S2: Construction of three-dimensional geonet; Three-dimensional geonets made of biaxially oriented polypropylene are selected, with longitudinal and transverse tensile strengths of not less than 8.5 kN / m and 7.5 kN / m, respectively. The mesh size is 10 mm × 10 mm, and the thickness is 18 ± 2 mm. During installation, the geonets are laid from the top of the slope downwards, with adjacent geonets overlapping longitudinally by 12 cm and transversely by 15 cm. The geonets are anchored to the slope using φ8 mm galvanized U-shaped nails, with a nail spacing of 80 cm longitudinally and 100 cm transversely. Drainage holes are set at 1.5 m intervals on the slope, with a hole spacing of 1.2 m and a hole diameter of 8 mm. The drainage holes are arranged in a quincunx pattern, and φ6 mm PVC permeable pipes are inserted into the holes.

[0041] The recommended mesh size range for geogrid mattresses is 5-10cm, and the recommended tensile strength is ≥3kN / m. Too small a mesh size (<5mm) will restrict root penetration, while too large a mesh size (>10mm) will reduce the restraint force of the mattress on the soil. A mesh size of 5-10mm allows more than 80% of plant roots to naturally penetrate and form mechanical interlocking. Since the typical sliding force of the reservoir bank slope is ≤2.5kN / m, a tensile strength of ≥3kN / m is selected to ensure that the mattress will not break under the action of the sliding force on the surface of the slope.

[0042] S3: Planting substrate construction; The planting substrate is prepared as follows: 70% local loam (passed through a 10mm sieve), 8% water-retaining agent (polyacrylamide, particle size 0.5-1mm), 2% slow-release fertilizer (NPK=15-15-15), 15% organic matter (humus), and 5% soil conditioner (diatomaceous earth). Use a mechanical mixer to thoroughly mix the planting substrate for at least 5 minutes to ensure even distribution of all components. Then use a hydroseeder to evenly spray the substrate onto the netting, controlling the spraying pressure at 0.4-0.6 MPa. Spray in two stages: the first spray is 6 cm thick, and after allowing it to settle naturally for 24 hours, spray the remaining 4 cm.

[0043] S4: Vegetation establishment and maintenance; Deep taproot and shallow creeping root plants are mixed and sown on the planting substrate. Preferably, tall fescue 'Hound No. 5' and bermudagrass 'Pyramid' are used for this mixture, with sowing rates of 27g / m² and 18g / m² respectively. 5g / m² of rhizobium inoculant is added at sowing time. Immediately after sowing, cover with 30g / m² of non-woven fabric and secure with bamboo skewers inserted into the planting substrate at 1m x 1m intervals. For the first 30 days of the maintenance period, spray once daily with 8-10mm of water each time; from days 31-60, spray once every two days; from days 61-90, spray twice a week. Apply top dressing monthly using 5g / m² of compound fertilizer (NPK=20-10-10). Simultaneously, regularly monitor soil moisture content, maintaining it within the range of 15-25%, and adjust the irrigation plan according to weather conditions.

[0044] Tall fescue (deep taproot system) has a taproot that can penetrate 40-60cm into the soil, enhancing the anchoring effect of deep soil layers. Bermuda grass (shallow creeping root system) has lateral roots that extend horizontally (20-30cm), forming a surface mesh cover that can inhibit erosion.

[0045] Preferably, the mixed sowing ratio of deep taproot plants (such as tall fescue) and shallow creeping root plants (such as bermudagrass) is 3:2. At this ratio, the root biomass distribution is optimal, balancing uplift resistance and shear strength. Recommended sowing density: 15-20 g / m² for deep taproot plants (such as tall fescue) and 10-15 g / m² for shallow creeping root plants (such as bermudagrass).

[0046] S5: Post-monitoring and maintenance; Vegetation coverage is measured quarterly, and the results are calculated using image analysis software after taking photos with a digital camera. The shear strength index of the reinforced soil is determined every six months by an in-situ direct shear test. Reseeding is carried out once each spring and autumn, with the reseeding amount being 15% of the original seeding amount. When the netting is found to be damaged, it is repaired in a timely manner, and the repair area should be 20cm larger than the perimeter of the damaged area.

[0047] like Figure 2As shown, this invention mainly uses a three-dimensional geonet, plant roots, and undisturbed soil (slope soil) to form an ecological-structural reinforcement measure. Specifically, this invention uses tall fescue, bermudagrass, and a three-dimensional geonet to form a composite reinforcement system. When reinforcing a slope, a three-dimensional geonet with specific pore size and tensile strength is first laid on the surface of the slope as a skeleton structure, and improved planting soil is filled between the layers of the geonet. Then, tall fescue and bermudagrass are mixed and planted in a specific ratio, where the deep taproot system of tall fescue and the shallow creeping root system of bermudagrass form a spatially complementary three-dimensional root network. Micro-drainage holes (i.e., φ6mm PVC permeable pipes) are set at the geonet holes to regulate the substrate moisture content. This composite system provides immediate shear strength through the three-dimensional geonet, and the plant roots gradually penetrate the geonet pores and form a mechanical interlock with the soil as they grow, ultimately forming a three-in-one reinforced body of "geomute-root-soil". In particular, the combination of the drought-resistant properties of tall fescue and the waterlogging-resistant properties of bermudagrass can effectively adapt to the alternating wet and dry environment caused by reservoir water level fluctuations, while the flexibility of the three-dimensional mesh can both restrain the slippage of the surface soil and not hinder root development.

[0048] Numerical simulations of the engineering slope model were performed using Geo-studio software to compare the reinforcement effects of an unprotected slope and an ecologically protected slope formed using the reservoir bank slope reinforcement method of this invention. Geo-studio software is one of the commonly used geotechnical engineering analysis software programs, which includes sub-modules such as SLOPE / W, SEEP / W, SIGMA / W, QUAKE / W, TEMP / W, CTRAN / W, and AIR / W. It can analyze and calculate slope stability, etc. Based on the Morgenstern-Price limit equilibrium theory and the saturated-unsaturated soil seepage theory, the variation law of slope stability was analyzed. The calculation model is as follows: Figure 3 As shown.

[0049] Analysis of the local stability of the two types of slopes under rainfall reveals significant differences in their overall stability: five days after rainfall, the local safety factor of the unprotected slope is 0.90, indicating an unstable state; while the local safety factor of the ecologically protected slope is 1.08, indicating a stable state. Figure 4 As shown.

[0050] Figure 5 The study demonstrates the variation of the slope safety factor under rainfall conditions on the potential sliding surface of the slope. The overall critical sliding surfaces of the two types of slopes are different. Taking the 5-day period after the back front rainfall as an example, the range and depth of the potential sliding surface of the slope are significantly reduced after the slope is reinforced using the reservoir bank slope reinforcement method of this invention.

[0051] Compared with existing technologies, the slope reinforcement method of the present invention has the following advantages for slope reinforcement: (1) Significantly improved erosion resistance: Traditional ecological slope protection mainly relies on single vegetation or simple geotechnical materials, which have limited resistance to water erosion. However, this invention uses a three-dimensional root network of tall fescue (deep straight root system) and bermudagrass (shallow creeping root system) combined with the mechanical reinforcement of three-dimensional geonet, so that the erosion of the slope under the condition of 2m water level change is only 18% of that of the traditional method, and the erosion resistance is increased by more than 5 times.

[0052] (2) Enhanced structural stability: Ordinary vegetation slope protection is prone to surface slippage due to rainfall or water level fluctuations in the early stage of root development. However, the present invention optimizes the three-dimensional mesh laying process (precisely controlling the overlap width, U-shaped nail fixing spacing and drainage hole arrangement) to form a stable embedded structure between the mesh and the soil, which is significantly better than the single protection method of using only vegetation or only geonet.

[0053] (3) Superior long-term durability: In existing technologies, pure vegetation slope protection is prone to degradation due to drought or freeze-thaw cycles, while pure engineering structure slope protection (concrete frame) lacks ecological function. This invention achieves a synergistic effect between vegetation and netting, with the root system penetrating the netting to form a biomechanical composite, which has a protection life of 12-15 years, while also providing ecological restoration and landscape effects.

[0054] (4) Reduced construction and maintenance costs: Compared with traditional grid beams or concrete slope protection, the present invention adopts standardized construction technology, reducing labor input by more than 30%; only seasonal reseeding and local repair of netting are required in the later stage, and the maintenance cost is reduced by 40% compared with conventional engineering measures.

[0055] (5) Stronger environmental adaptability: By optimizing the substrate ratio and vegetation combination, the present invention can still maintain a vegetation coverage rate of more than 90% under harsh environments such as drought, water level fluctuation and freeze-thaw cycles, while the coverage rate of ordinary ecological slope protection is usually less than 60% under the same conditions.

[0056] In summary, this invention achieves synergistic optimization of ecological benefits and engineering performance, providing an efficient, economical, and sustainable protection solution for easily eroded areas such as reservoirs, river channels, and highway slopes.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for reinforcing reservoir bank slopes based on the coupling effect of root system and engineering structure, characterized in that: Includes the following steps: S1: Slope pretreatment; S2: Construction of three-dimensional geonet; S3: Planting substrate construction; S4: Vegetation establishment and maintenance; Deep-rooted and shallow-rooted plants are mixed and sown on the planting substrate, and the plants are maintained. As the plant roots grow, they gradually penetrate the mesh of the geonet and form a mechanical interlock with the slope soil. The roots of the deep-rooted and shallow-rooted plants form a three-dimensional root network. The deep-rooted and shallow-rooted plants and the three-dimensional geonet form a composite reinforcement system. S5: Post-monitoring and maintenance.

2. The method for reinforcing reservoir bank slopes based on root-engineering structure coupling as described in claim 1, characterized in that: The ratio of deep taproot plants to shallow creeping root plants is 3:

2.

3. The method for reinforcing reservoir bank slopes based on root-engineering structure coupling as described in claim 1, characterized in that: Tall fescue is used for plants with deep taproot systems, while bermudagrass is used for plants with shallow creeping roots.

4. The method for reinforcing reservoir bank slopes based on root-engineering structure coupling as described in claim 1, characterized in that: The sowing density for deep taproot plants is 15-20 g / m², and the sowing density for shallow creeping root plants is 10-15 g / m².

5. The method for reinforcing reservoir bank slopes based on root-engineering structure coupling as described in claim 1, characterized in that: The planting substrate is formulated as follows: 70% local loam, 8% water-retaining agent, 2% slow-release fertilizer, 15% organic matter, and 5% soil conditioner.

6. The method for reinforcing reservoir bank slopes based on root-engineering structure coupling as described in claim 1, characterized in that: S1 specifically includes: Remove loose soil, gravel, and vegetation roots from the slope surface, and repair any uneven areas to ensure that the slope flatness error does not exceed ±5cm. The slope is compacted in layers using a road roller; Dig intercepting ditches at the top of the slope and drainage ditches at the bottom of the slope to prevent surface runoff from eroding the slope surface.

7. The method for reinforcing reservoir bank slopes based on root-engineering structure coupling as described in claim 1, characterized in that: S2 specifically includes: Three-dimensional geonets are laid from the top of the slope downwards, with adjacent geonets overlapping and anchored to the slope. Multiple rows of drainage holes are set on the slope, and a permeable pipe is inserted into each drainage hole.

8. The method for reinforcing reservoir bank slopes based on root-engineering structure coupling as described in claim 1, characterized in that: S3 specifically includes: Use a mechanical mixer to thoroughly mix the planting substrate, and then use a hydroseeder to evenly spray the substrate onto the netting.

9. The method for reinforcing reservoir bank slopes based on root-engineering structure coupling as described in claim 1, characterized in that: S4 specifically includes: Mix deep taproot plants and shallow creeping root plants, and add rhizobium inoculant during sowing; Immediately after sowing, cover the seeds with non-woven fabric and secure the fabric in place. Irrigation and fertilization should be carried out during the maintenance period.

10. The method for reinforcing reservoir bank slopes based on root-engineering structure coupling as described in claim 1, characterized in that: S5 specifically includes: Vegetation cover is measured quarterly, and the results are calculated using image analysis software after taking photos with a digital camera. The shear strength index of the reinforced soil is determined every six months by in-situ direct shear test. Reseeding is carried out once each spring and autumn, with the reseeding amount being 15% of the original seeding amount. When the netting is found to be damaged, it is repaired in a timely manner, and the repaired area is 20cm larger than the perimeter of the damaged area.

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