1. The principle of three-dimensional vegetation net spraying and planting technology
Geotechnical materials combined with grass planting and slope protection started abroad in the early 1980s. At first, the two-dimensional geogrid combined with grass planting or the composite material of "double-pulling net + straw + double-pulling net" combined with grass planting. Due to the two The effect of 3D structure in soil erosion control is not obvious. Later, a 3D network material with good soil erosion control ability, namely 3D vegetation network, was developed.
The three-dimensional vegetation net, also known as the geonet pad, is a three-dimensional structural net made of thermoplastic resin. The bag, filled with planting soil and grass seeds, has two functions of anti-scour and beneficial to plant growth.
The principle of 3D vegetation net spraying and planting technology is mainly in two aspects: one is that before the turf is formed, the reinforcement and anchoring effect of the 3D net can protect the slope from wind and rain erosion; The tendons are tangled to form an overall modular structure with high tensile strength, which can increase the coverage area of grass and increase the fiber density of the plant root system. The high tensile strength of the three-dimensional mesh itself can significantly increase the strength of plant roots.
2. Construction characteristics of three-dimensional vegetation net spraying and planting technology
(1) Hanging three-dimensional vegetation net spraying and planting grass greening is suitable for cutting slopes, soil slopes, and strongly weathered bedrock slopes whose slope ratio is not steeper than 1:1.
(2) The backfill soil in the three-dimensional net bag is generally clay soil obtained from local materials, so as to facilitate the combination with the net and prevent the erosion of rainwater.
(3) The slope surface on which the three-dimensional vegetation net is laid should be as smooth as possible to ensure the close combination of the net and the slope surface, so as to avoid the phenomenon of hollowing in some places, which will cause the grass seeds to fail to implant, and the slope surface after flattening will appear "baldness".
3. Construction technology of three-dimensional vegetation net spraying and planting technology
(1) Clean up the slope to meet the design requirements, remove weeds and miscellaneous trees, and supplement with spraying to inhibit the growth of weeds. Cover the soil with a thickness of 5 to 7 cm on the leveled slope, and the thickness of the cover depends on the soil type and the smoothness of the slope.
(2) According to the dry and wet conditions of the slope, water the slope with water, and it is advisable that there is no floating soil and dusty soil in the soil.
(3) Lay down and level the three-dimensional mesh pad from top to bottom along the slope, and fix the mesh pad with U-shaped nails. The U-shaped nails are staggered, with a vertical spacing of 100cm and a horizontal spacing of 140cm. Steel nails are used to fix them. Make the mesh pad close to the slope.
(4) The top of the slope shall be buried with pressure ditch or fixed with U-shaped nails to fix the three-dimensional mesh.
(5) When laying the second three-dimensional mesh, overlap the overlapped part of the first three-dimensional mesh by 10-15cm, and fix the overlapped part with U-shaped nails, and the spacing between the U-shaped nails on the slope surface is 1m.
(6) The three-dimensional net should be crimped by 5-10cm around the contact area between the three-dimensional vegetation net and the structure, and the edges should be pressed with U-shaped nails to make the three-dimensional net and the surrounding structures contact and close.
(7) After the three-dimensional vegetation net is laid and fixed, the fine-grained soil and fertilizer are manually spread from the top of the slope downward, so as to cover the net bag.
(8) Due to the small size of the three-dimensional mesh, in order to ensure the compactness of the backfill, it should be carried out in three steps. Mesh backfill: The sieve hole is smaller than the tree hole of the three-dimensional vegetation. After sieving, the first backfill is carried out from top to bottom and confirmed (do not use wet cloth). Water spray settlement: After the first backfill, use a high-pressure water truck to water and soak the soil, let the backfill soil settle naturally, and prevent the phenomenon of "empty drum". The second backfill method is the same as above. Mud backfill After the second backfill, the net, soil and slope soil are basically integrated, but there are a small part of the "empty drum". Symptoms are reduced to a minimum to none.
(9) The mixture of seeds, fertilizer, soil conditioner, water-retaining agent and water is evenly sprayed on the slope surface by hydraulic spraying machine. should.
(10) The role of polypropylene non-woven fabrics is to prevent water from scouring the slope and seeds, to retain water and keep warm, which is conducive to the germination and growth of flowers and grass seeds. After covering, it is fixed with medium Φ4 "U" nails.
(11) Pre-, middle- and late-stage maintenance. In the early stage of maintenance, spray irrigation water is the main method, and the soil is often kept moist to promote seed germination and rapid growth and coverage; in the middle stage, natural rainwater is used for maintenance. In case of drought, water is sprayed 1-2 times a month; , and topdressing fertilization, to promote seedlings turn green. Timely detection and prevention of pests and diseases.
In order to make the vegetation produced by the spraying and planting technology of the three-dimensional vegetation net enhance the slope-fixing effect and have the plant diversity characteristics similar to natural vegetation, ecological planting methods can also be combined in the construction process, such as mixing grass seeds during spraying. Appropriate amount of seeds of native wild shrubs such as mimosa and dung bean, or dig pits to plant trees and shrubs such as yellow kudzu and lilac after hanging nets; or use pits to plant native shrubs such as American thorn and five-colored plum after the grass is covered. , oleander, wild peony, etc., in order to form the effect of natural mountains and forests, to achieve the purpose of ecologically shaped soil slope protection and greening and beautifying the environment. This kind of greening protection method has been tested and promoted on the expressway, and it has achieved a very reasonable effect.
4. Precautions for the construction of three-dimensional vegetation net spraying andplanting grass
(1) It must be strictly ensured that the three-dimensional vegetation net used has sufficient tensile strength and good flexibility, so as to make it adhere more closely to the soil on the slope surface, and avoid hanging in the air, causing the hanging air to kill the seedlings. and the overhang area collapsed, resulting in the failure of the slope protection.
(2) Drainage adjustment and separation facilities such as water retaining shoulders and slope aqueducts should be improved.
(3) The slope greening project should be constructed by a professional greening construction team, and the construction unit should have enough construction machinery, technical personnel and successful construction experience to ensure that the greening project is completed within 2 to 3 months, and the greening quality guarantee period is guaranteed. greening effect.
(4) In the conditional section, a soil trench with a width of 20cm and a depth of 30cm can be dug at the slope of the cutting edge to bury the three-dimensional net; Surface water washes away the soil under the 3D mesh.
(5) Grass species suitable for local climatic characteristics should be selected, and grass species are required to have strong vitality, strong disease resistance, developed root system, and short withering and yellowing period. And use warm-season cold-season grass seed mixed sowing, and strive to be evergreen in all seasons, and an appropriate amount of grass seeds should be added to the spray-sown grass seeds.
(6) The key to ensuring the success of this work is to grasp the construction season in time.
(7) Mix the mixture evenly when spraying, and pay attention to the humidity of the slope during maintenance until the grass is planted.
