1. 1 planting grass
Applicable conditions of 1. 1. 1
For embankments or cutting slopes with stable slopes and slight slope erosion, it is generally required that the slope gradient should not be greater than 1: 1, and the slope water flow velocity should not exceed 0.6m/s, which is not suitable for long-term submerged slopes.
1. 1.2 planting pattern
According to different construction methods, there are the following ways:
(1) Seed sowing method: suitable for soft soil, sandy soil with thickness less than 25mm and cohesive soil with thickness less than 23mm, with slope less than 1: 1.
(2) Spray seeding method: it is suitable for gravelly soil with sand between gravels, sandy soil with a thickness less than 25mm, cohesive soil with a thickness less than 23mm, cohesive soil slope with a thickness greater than 25mm, or hard soil with a thickness greater than 25mm, and can be used in conjunction with carpet laying projects in areas with frequent rainstorms.
(3) Exotic soil spray seeding method [5]: Exotic soil spray seeding technology is a new technology to improve the slope planting environment, promote plant growth, realize three-dimensional greening, and restore the natural vegetation on the slope that cannot be afforested or has poor greening effect under ordinary conditions. The method of spray seeding with foreign soil has wide adaptability, and is suitable for both soil slopes and rock slopes.
(4) Acupoint ditching method
Methods: The point-and-click method is to dig holes with a diameter of 5 ~ 8 cm and a depth of 65,438+00 ~ 65,438+05 cm on the slope, with about 8 ~ 65,438+02 holes per square meter to prevent solid fertilizer from entering, and to bury the holes with soil and sand before sowing. Trenching method is to dig a trench with a depth of 10 ~ 15 cm on the slope with a horizontal spacing of about 50cm, and then put in fertilizer and sow.
Suitable for: the site conditions of green space on both sides of the highway are poor, such as hard soil or granite weathered sandy soil excavation slope.
1.2 paving turf
Applicable conditions of 1.2. 1
Various soil slopes, especially when the slope erosion is serious, have steep slopes (up to 60) and the runoff velocity reaches 0.6 m/s.
1.2.2 paving method of turf
Paving, horizontal lap, vertical or oblique lap and slope half broken, and paving square or arch frame with flaky, paving turf in square, etc.
1.3 tree planting
It is suitable for all kinds of soil slopes and strongly weathered rock slopes, and the slope is not steeper than 1: 1.5. Planting plants on subgrade slopes and floodplains has achieved good results in strengthening subgrade and protecting river banks. It can reduce the flow rate of water, and planting on the river beach can promote sediment deposition and prevent water from directly scouring the bank. Planting trees is best combined with planting grass. It is forbidden to plant trees on the slopes of high-grade highways.
2. Flexible support
2. 1 stereoscopic vegetation network [6]
Three-dimensional vegetation net, also known as anti-corrosion net, is made of thermoplastic resin. The structure is divided into two layers, the upper layer is a high modulus foundation layer stretched on both sides, which is strong enough to prevent the deformation of vegetation net and effectively prevent soil erosion, and the lower layer is composed of elastic, regular and irregular net bags.
2. 1. 1 mechanism:
Three-dimensional vegetation net is a three-dimensional net structure composed of multi-layer plastic concave-convex net and high-strength flat net. The surface appearance is uneven. The material is loose and flexible, leaving more than 90% space for filling soil and sand, firmly protecting grass seeds and topsoil in the middle of the three-dimensional net.
2. 1.2 characteristics
① The soil consolidation effect is excellent. Experiments show that before turf formation, when the slope is 45 degrees, the blocking rate of the three-dimensional vegetation network is as high as 97.5%, and even when the slope angle reaches 90 degrees, the three-dimensional vegetation network can still retain 60% of the soil.
② Strong erosion resistance. Three-dimensional net mat and plant roots can play the role of shallow reinforcement. This composite system has strong anti-scouring ability and can achieve the purpose of effective slope protection.
③ The mesh pad is made of polyethylene, which is non-toxic and has stable and reliable chemical properties. The service life of the net mat can reach more than 50 years after it is buried underground, and even if it is exposed to the sun, the service life can reach 10 years.
(4) Grass seeds are mixed, which can quickly grow into lawns; Strong resilience, barren tolerance and extensive management.
2. 1.3 Applicable conditions
The design of stable earth-rock slopes, especially those with poor soil quality and mixed soil and rock, can play a very good role in soil consolidation and erosion prevention and improve the quality of grass planting.
2.2 Active protection of steel rope net [9]
The steel wire mesh is fixedly covered on the slope through the anchor rod and the supporting rope.
The mechanism of action is to form continuous support for the whole slope through the pre-tensioned steel rope net fixed on the anchor rod or supporting rope, and the metal net or geogrid used to prevent fine particles in weathering and peeling, falling off or soil loss. Its pretension makes the system close to the slope, and after moving or slight displacement, a local rock slope or soil body is constrained by prestress, thus realizing its active protection function. The principle of the system is similar to that of shotcrete and anchor support. However, due to its flexible characteristics, the system can evenly transfer the sliding force in the local body to the surrounding areas, so as to give full play to the protective ability of the whole system and enable the system to bear a large sliding force. At the same time, like the three-dimensional vegetation network, it can cooperate with plants to realize plant protection, so that the root system of plants can be integrated with the slope protection system to achieve the best slope protection and environmental protection.
2.3 Passive protection of steel wire mesh
This method is a flexible stone fence, which can intercept and store falling rocks. It consists of four parts: steel rope net, fixing system, decompression ring and steel column.
2.3. 1. Applicable conditions
The high cutting slope with interactive development of rock mass has poor integrity and the possibility of rock collapse.
2.3.2 Mechanism of action
When the rockfall hits the stone barrier net, its impact force is firstly dissipated through the flexibility of the net, and the residual load is gradually loaded to the periphery of the rope net system from the impact point, and finally transferred to the anchoring bedrock and stratum, and the ultimate residual load borne by the anchor rod and its foundation is very small.
3. Comprehensive protection
3. 1 Rock Slope Greening Spraying Technology [8]
The core of green spray seeding technology is to create a porous and stable structure on the rock slope, which can not only make the plants grow and develop, but also make the plant matrix not be washed away. It uses a special mixer to spray mixed dry materials, such as soil, fertilizer, organic matter, water-retaining materials, plant seeds, cement and so on. On the rock surface after adding water. Due to the bonding effect of cement, the above mixture can form a hardened body with continuous gaps on the rock surface. A certain degree of hardening prevents the planting from being eroded, and the gap is filled with seeds, soil, water-retaining materials, etc. Gap is not only the filling space of planting substrate, but also the growth space of plant roots.
3. 1. 1 Applicable conditions
It is not only suitable for all excavated rock slopes, but also suitable for rock piles, soft rocks, cataclastic rocks, loose rocks, extremely acidic soil rocks, retaining walls, retaining walls, concrete structure slopes and other harsh environments that are not suitable for greening.
3. 1.2 construction method
① Trim the slope.
In expressway slope support engineering, the slope is relatively flat, and generally only surface impurities need to be removed. If there are very concave and convex places, we must deal with them.
(2) Anchoring and hanging nets
First, punch holes in the slope, then spread woven nets on the slope, and then fix them with anchor rods or anchors. For small slopes (>: 1: 1), slopes with stable rock mass structure or steep slopes with arches, the mixture can be sprayed directly on the rock surface without hanging the net.
③ Spray mixing
After the materials are mixed in proportion, the mixture is sprayed on the rock surface together with water and PH buffer with a special spray mixer. Spraying is divided into two steps: spraying the mixture without seeds with a thickness of 7-8 cm first, and then spraying the mixture with seeds with a thickness of 2-3 cm. The average thickness of the sprayed mixture is 10 cm, and the variation range is 3 ~ 15 cm.
④ Covering
After spraying, it can be covered with non-woven fabric, grass curtain, sunshade net and straw. Keep moisture and prevent rain from washing away.
⑤ Maintenance
If it doesn't rain after spraying, water it every day to keep the soil moist. Generally, it germinates in about 7 days, becomes a lawn in one month, and the coverage rate reaches over 90% in two months. After turning into a lawn, you can gradually reduce the frequency of watering.
3.2 Frame slope protection
Applicable conditions:
Weathered rock slopes and high soil slopes with stable slopes.
3.2.2 Selection of Framework Form
Frame lattice slope protection can choose rhombic lattice, hexagonal lattice, master-slave lattice and so on.
3.3. 1. Structural requirements:
(1) For planting grass in the frame, soil spraying or turf planting is generally adopted.
(2) The grid forms mainly include square, diamond, arch, main ribs with oblique or wavy transverse ribs, and combinations of several geometric figures. The width of grid and transverse rib is 0.4~0.6m, the width of main rib is generally about 1m, and the grid spacing is 2.5 ~ 3.5m 。
(3) Fixed piles or anchors should be set according to the situation.