River ecological slope design principles and practical application?

River berms are mostly slurry masonry, concrete and other berms, and now most of the river has adopted ecological berms. The following design principles and practical application of ecological river berms and the advantages and disadvantages of traditional river berms for comparison.

Traditional river berms: slurry or dry masonry stone berms, cast-in-place concrete berms, precast concrete block berms. Advantages: strong stability of the river bank slope, flooding and drainage function, disadvantages: high cost, maintenance difficulties, damage to the natural environment and ecology.　Ecological slope protection: vegetation grass, geomaterials, greening network, hydroseeding planting, vegetation type ecological concrete, cement ecological planting base, soil curing agent, concrete interlocking blocks combined with vegetation grass and other methods, advantages: at the same time with the efficacy of water conservancy projects and landscape "hydrophilic", ecological and environmental protection, architectural art and so on.

Connotation of ecological berm

Connotation of ecological berm concept: First, the river berm to meet the requirements of flood control standards, the main point is to build a permeable, air permeability, growth of plants, ecological protection platform.　Second, the river berm to meet the requirements of ecological balance of the slope, that is, to establish a benign ecosystem of the river slope, by the tall trees, low shrubs, flowers, grasses, fish nests, aquatic grasses, animals along the beach, waterfront slopes, foot of the slope and the near-shore water composed of three-dimensional ecological system of the river slope.　Ecological slope protection should be "both to meet the protection standards of the river system, but also conducive to the river system to restore the ecological balance" of the system engineering. The first element is the requirement of people to nature, that is, people transform nature for the sake of socio-economic development and safety; the latter element reflects people's respect to nature, that is, transforming nature without destroying the balance of nature. The combination of the two reflects the concept of "harmonious development of man and nature and the environment".　

Ecological slope design principles

1 Hydraulic stability principle The design of slope protection should first meet the requirements of slope stability. Bank slope instability factors are: ① Bank slope surface gradually scouring caused by instability; ② instability caused by surface soil sliding damage; ③ instability caused by deep sliding. Therefore, the hydraulic parameters and geotechnical parameters affecting the stability of the slope should be studied so as to realize the hydraulic stability design of the slope.　2 Ecological principles Ecological slope design should be coordinated with ecological processes to minimize its destructive impact on the environment. This coordination means that the design should respect species diversity, reduce deprivation of resources, maintain nutrient and water cycles, maintain the quality of plant habitats and animal habitats, and contribute to the improvement of habitat and ecosystem health as a general principle. The following three main aspects are included: A Local Principle.　The design should be adapted to local conditions, and based on a full understanding of the local natural environment, the design should be carried out in harmony with the local natural environment. Including: ① Respect traditional culture and vernacular knowledge; ② Adapt to the natural process of the place, the design should take these natural factors with the characteristics of the place into consideration, so as to maintain the health of the place; ③ According to the local actual situation, try to use local materials, plants and building materials, so as to make the ecological berms in harmony with the local natural conditions.　B Principle of protecting and saving natural resources.　For the logistics and energy flow of the natural ecosystem, there are four solutions emphasized by ecological design: ① Protect non-renewable resources, which should not be used unless as a last resort; ② Minimize the use of energy, land, water and biological resources, and improve the efficiency of their use; ③ Utilize the original materials including vegetation, soil, masonry and stone, etc., to serve the new function, which can greatly save the resources and energy consumption; ④ Try to keep the slope protection in a virtuous cycle, so that the resources can be regenerated.　C Return to nature principle. The natural ecosystem provides various conditions and processes to maintain human survival and satisfy their needs, which is the so-called ecosystem services. Emphasis is placed on: ① There is no waste in nature, every healthy ecosystem has a perfect food chain and trophic level, so the ecological design should make the system in a healthy state; ② Edge effect, in the edge zone of two or more different ecosystems, there is a more active energy flow and flow of goods, with a rich variety of species and higher productivity, and is also the richest biological communities, the highest ecological benefits of the section, the river bank as a The edge zone between water ecology and land ecology, its edge effect should be fully considered in the design; ③ Biodiversity, maintain effective number of plant and animal populations, protect various types and multiple stages of ecosystems, respect various ecological processes and natural disturbances, including the natural fire process, the alternating pattern of dry and rainy seasons, and the seasonal inundation of floods.　

Introduction of ecological slope protection

1 plant slope protection with developed root system plants for slope protection and soil fixation advantages: not only can achieve soil fixation and sand retention, to prevent soil erosion, but also to meet the needs of the ecological environment can also be landscaped.　Case: Handan City, Zhizhang River, Busan River plant berms, with the local morning glory, bentgrass and other eight kinds of herbaceous plants for the berm plant, willow and other shrubs for the foot of the waterfront slope wave protection forest.　Soil-fixing plants can be selected according to the climate of the region more suitable plant species, generally considering the following conditions: A low requirements for soil quality, adaptable to climatic conditions. Resistant to acid, alkali, cold, high temperature, drought, etc., with strong growth capacity.　B well-developed root system, low stem, luxuriant branches and leaves, fast growth, long green period, able to cover the ground surface quickly.　C strong rooting, high survival rate, and can absorb deep water and nutrients, effective soil fixation.　D low price, sloppy management, no maintenance, no pests and weeds competitive.　In the plant slope protection project, the commonly used plants mainly include: tall fescue, perennial ryegrass, fine bentgrass, awnless bird's-eye, grass early harvest bermudagrass, etc.; seeding grass should be considered as a mixed sowing. Sowing method: artificial planting or transplantation method. Disadvantages of plant slope protection: the slope protection is easy to be washed by the rain to form a deep ditch, the slope protection effect is poor, affecting the landscape. Long-term immersion in the water, flood flow rate of more than 3m / s of the earth embankment waterfront slope and flood control key areas (such as river bends) is not suitable for planting grass slope protection.　2 Three-dimensional vegetation mesh slope protection Three-dimensional vegetation mesh was originally used for the protection of mountain slopes and highway slopes, and is now also being used for the protection of river banks and slopes. It is the main use of active plants and combined with geosynthetics, in the slope to build a protective system with its own growth capacity, through the growth of plants on the slope to strengthen a new technology. According to the topography of the slope, soil quality and regional climate and other characteristics, the surface of the slope is covered with a layer of geosynthetic materials and planted with a variety of plants according to a certain combination and spacing, through the growth of plants to achieve the purpose of root reinforcement, stem and leaf erosion prevention, which can form a dense vegetation cover on the slope surface, form a root system in the topsoil layer, effectively inhibit the erosion of the slope by storm runoff and increase the shear strength of the soil body, reduce the pore water pressure and soil self-deepening. Pore water pressure and soil self-gravity, thus greatly improving the stability of the slope and scour resistance. Geonet has a good effect on reducing the evaporation of soil water on the slope and increasing the infiltration amount.　

Three-dimensional vegetation network slope protection advantages:

Combined the advantages of geonet and plant slope protection, played the role of composite slope protection. When the vegetation coverage of the slope reaches 30% or more, it can withstand the scouring of light rain, and when the coverage reaches 80% or more, it can withstand the scouring of heavy rain. When the plant growth is luxuriant, the runoff flow rate can resist scouring is up to 6m/s, which is more than 2 times of the general turf. At the same time, due to the geonet material for the black polyethylene, with heat-absorbing thermal insulation effect, can promote seed germination, is conducive to plant growth.　　　3 Vegetative eco-concrete slope protection Vegetative eco-concrete consists of porous concrete, water retention materials, slow-release fertilizer and topsoil. Porous concrete is composed of coarse aggregate, cement, and appropriate amount of fine admixture, which is the skeleton of vegetative eco-concrete. The water retention material is based on organic water retention agent and mixed with inorganic water retention agent to provide essential moisture to the plants. The topsoil is laid on the porous concrete surface to form a vegetation germination void, reduce water evaporation from the soil, provide nutrients for the early stages of vegetation germination and prevent the concrete surface from overheating during the early stages of grass growth. Many vegetative grasses can grow well on the vegetative eco-concrete, and in the experimental process, purple wool and awnless birdseed showed excellent cold resistance.　Advantages: Not only realize the concrete slope protection, but also plant flowers and grasses on the slope, beautify the environment, make the perfect combination of hardening and greening.　It has good resistance to scouring, and the grass on top has buffer performance. Due to the "anchoring" effect of grass roots, the anti-slip force increases, after the grass roots, grass, soil and concrete form a whole, which improves the stability of embankment slopes. Porous concrete porosity is up to 40% or more. Porous concrete porosity up to 40% or more, the surface equivalent pore diameter 2cm ~ 3cm, pore from the top surface of the component can be meandered to the ground, in the embankment berm porous concrete has a high degree of permeability, to a large extent, to maintain the protected soil and the air between the exchange of humidity, heat capacity.　The thickness of the vegetated eco-concrete components and the geometry of a single piece can be calculated in accordance with the relevant provisions of the Embankment Engineering Design Code (GB50286-98). Due to the "anchoring" effect of grass roots, it will make the above calculation results more secure.　Ecological slope protection of the North Canal: the slope of the embankment is an earth slope, the base is relatively dense, the river channel is trapezoidal compound section, and the side slope is less than l:3. Generally, it is designed according to the standard flood of one in 20 years, and the flow rate of the anti-washout velocity is 1.2m/s, and the flood water does not flood the beach. The engineering measures taken include: (1) constructing a slope protection platform suitable for ecology; (2) planting grass on the protection platform.　Protection platform: Grass-planted concrete blocks are used to protect the slope in the upstream curved top flush part, and three-dimensional mesh is used to protect the slope in the straight section. The foot of the slope adopts fish nest bricks and grass-planted wall bricks to protect the bottom to meet the requirement of anti-impact.　The above is the content of the Zhongda Consulting collated

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