First of all, about ecological concrete.
Ecological concrete is a new type of environmental protection material, which is simply a kind of special concrete with both protective function and plant growth. From a professional point of view, eco-concrete is a kind of special concrete made by carefully selecting materials and using special additives, and then using professional technology. This special concrete can reduce the environmental load and improve the harmony with the ecological environment. Ecological concrete is widely used in many ecological projects and general civil buildings, especially slope protection projects in some water conservancy projects.
Second, the ecological concrete construction technology
Soil erosion is a serious ecological environment problem in many areas, and many human activities will aggravate this ecological environment problem. Therefore, it is very necessary to control and prevent soil erosion by some artificial methods. Eco-concrete is a kind of environmental protection material commonly used in slope treatment. While protecting the slope from soil erosion, it does not affect the normal production of plants on the slope, killing two birds with one stone. Eco-concrete is a special material, which will be used in many ecological projects, but the construction technology of eco-concrete is basically the same on different occasions.
General ecological concrete construction technology includes the following procedures:
1, forecast lofting
2. Pouring frame: including formwork support, concrete pouring and concrete curing.
3. Laying nutritious non-woven fabrics
4, pouring ecological concrete
5. Filling saline-alkali improver
6. Filled with composite long-lasting nutritional materials?
7. Maintenance of planted plants
Classification of application fields:
First, the application of high slope ecological protection
Ordinary net-hanging foreign soil spraying or hydraulic spraying can not achieve permanent stability on high-steep rock slopes, and vegetation concrete technology is a new technology for ecological protection of high-steep rock slopes (concrete slopes and hard rock slopes) above 60 degrees [1999, patent of Three Gorges University, Xu Wennian, Liu] [3]. This technology is based on cement, CBS vegetation concrete greening additives AB bacteria and Liu. (volume ratio), and the spraying mixture composed of sandy loam, plant seeds, fertilizer and water is used for slope protection and greening technology. This technology has a high degree of mechanization, large production capacity, long spraying distance with dry shotcrete anchor machine, certain strength of sprayed layer and strong anti-scouring ability, and is especially suitable for steep rock slopes.
1, vegetation concrete ecological slope protection construction technology
Vegetation concrete ecological slope protection includes the following procedures: slope trimming, laying and installation of galvanized barbed wire and anchor nails, preparation of vegetation concrete and spraying of vegetation concrete.
2. Slope repair
Remove all obstacles that hinder slope construction. Including:
Clean up the vegetation joints. Clean the contact surface of the original slope above the groove line, and the cleaning width is1.0 ~1.5m. It is the transition between the project and the original slope, that is, the junction of vegetation, based on the removal of plant branches on the original slope, without digging out underground rhizomes.
Remove weeds, fallen leaves, dead branches, floating soil and pumice on the slope;
Slope trimming treatment. For the protruding and easy-to-drop parts with obvious dangerous rocks, photograph them. First, drill a hole along the slope in the protruding part with an electric hammer or a pneumatic pick, and then photograph it with a hammer. For areas with obvious depressions, fill them. Use a pneumatic pick to chisel out the pits to be filled, the depth is not less than 1cm, then use high-pressure wind and water to clean them, and finally use M7.5 mortar to fill them.
3) Laying and installation of barbed wire and anchor nails
Drill a hole perpendicular to the slope with an electric hammer and drive in the anchor nail. The anchor nails are made of φ 14 or φ 16 steel bars, with a length of 30cm~60cm and an anchor nail spacing of1m×1m. The hole depth is 20cm~50cm, and the anchor rod is exposed 10cm. In order to strengthen the stability of the top of the slope, it can be encrypted and lengthened, with a length of 60cm. The anchor nail is slightly inclined, and the included angle with the slope is 95 ~ 100. The anchor nail will be lengthened according to the situation, and the stability of the anchor nail after hitting the slope shall prevail.
According to the designed anchor nail specifications, rock penetration depth and spacing, 14# galvanized wire mesh (mesh 5×5cm) shall be laid after the anchor nails are arranged on the vertical slope. Mesh should be laid from the top to the bottom of the vegetation joint, steel mesh should be laid tautly, and the overlap between meshes should be no less than 5㎝. There is no need to overlap the left and right sides of mesh, but all meshes should be firmly bound with 18# wire, and anchor nail joints should be firmly bound with 18# wire. The net should keep a distance of 7 cm from the slope, otherwise it should be supported by cushion blocks.
4) Vegetation concrete spraying material
Vegetation concrete is composed of sandy loam, cement, organic matter and special additives, and the selection requirements of each component material are as follows:
Prepare the materials of each component according to the proportion, and fully stir them with a blender for later use. When mixing the surface substrate, plant seeds should be added according to the design requirements.
5) spraying vegetation concrete
After the slope treatment, net laying and anchor laying are completed and the components of vegetation concrete matrix are ready, the vegetation concrete matrix can be sprayed. The equipment used for spray planting is a general concrete sprayer, which is divided into base course and surface course. Spray protection should be carried out from top to bottom and from bottom to surface on the slope. The width of each shotcrete board is 4 ~ 6 meters and the height is 3 ~ 5 meters.
Spray seeding is supplied by an air compressor larger than 12 cubic meter, and the dry spraying method is adopted for construction (the equipment is the same as the anchor spraying equipment, using PZ-6 gunning machine).
Grass-roots spraying. 1) Method: Before spraying concrete, check again whether the slope surface is clean of floating soil, turf, tree roots and other impurities, spray the slope surface with water after confirmation, so that the sprayed vegetation concrete base material can be closely combined with the base surface, then carry out trial spraying test to adjust the water cement ratio, and then carry out spraying concrete construction; The thickness of sprayed concrete base is 8 ~ 9cm；; At the beginning of spraying operation, gas should be supplied first, then turned on and then fed. At the end of spraying, the air should be turned off after spraying the materials. 2) Control measures: sprayed concrete at the grass-roots level can be sprayed to the design thickness at one time without layered spraying; In the process of spraying, the distance between the nozzle and the slope should be controlled between 0.6m ~ 1.0m, which should generally be perpendicular to the slope, and the maximum inclination angle should not exceed10; When spraying concrete, the output pressure of the nozzle should not be less than 0.1MPa; Spraying is carried out from top to bottom, with concave parts sprayed first and convex parts sprayed later; Spraying movement can adopt "S" shape or spiral movement.
Surface spraying: surface spraying should be carried out within 8 hours after the completion of grass-roots construction, generally controlled within 3 ~ 4 hours; The surface layer thickness is1~ 2 cm; Before spraying water on the surface layer, spray it once on the slope to ensure the bonding between the base and the surface layer; Spray sowing at close range to ensure uniform sowing of grass seeds; Spray seeding is carried out from top to bottom, and the width of a single block is controlled at 4 ~ 6m.
Ecological concrete is a rare environmental protection material, which is very effective for slope treatment, but its construction is a very professional technology, and every step requires professional personnel to use professional equipment to carry out the construction seriously, and there can be no falsehood. At the same time, the construction of ecological concrete projects should have a strict project supervision system. As an eco-concrete constructor, one must be qualified first, then the manpower needs professional qualification certificate, and finally all the construction equipment must meet the professional requirements of construction.
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