Detailed analysis of rock slope greening technology?

Since 1990s, slope greening has entered China. After twenty or thirty years' development, the technical regulations for slope greening have been gradually improved. Based on a lot of practical experience and geological research, the following analysis is made for slopes with different properties:

Analysis of geological conditions of rock slope;

A: Lack of essential ingredients for plant growth. The rocky slope does not have the necessary soil environment for vegetation growth, so it is impossible to sow or green seedlings. Even if the foreign soil spraying technology widely used in China is adopted, its protection effect is not ideal, because the bonding force between sprayed concrete and rock slope is very small. In addition, the water-retaining function of rock mass is poor, and it contains less activated nutrients, so it is difficult for vegetation roots to absorb enough water and nutrients from slope rock mass for its growth and development.

B: the slope is large. Generally, the design slopes of rock slopes of expressways, railways and mines are all above 1∶0.75, and some of them can reach 1∶0.3, or even stand upright. Rainwater runoff on slope is fast, which is easy to form erosion in high rainfall areas; Naturally weathered soil particles and soil particles brought by wind transport are difficult to stay on the slope surface, and are accumulated at the foot of the slope by hydraulic and gravity. In addition, rainfall can't stay on the slope, which makes it difficult for vegetation to survive.

C: The natural ecological conditions on the slope are harsh. Rock slope is not covered with soil, so it is short of water. In direct sunlight, the temperature of the exposed rock surface is too high. Even if seeds spread by wind or animals are embedded in cracks in rocks, they will be difficult to germinate and survive because of high temperature. No matter which way is adopted, we should first consider the purpose of slope greening and the effect achieved in the later period, and then create conditions, that is, how to fix the plant growth substrate on the rocky slope to provide water and fertilizer for plant growth for a long time and withstand the wind and rain of nature. Specifically, the greening construction technology of rock slope should focus on solving the following problems:

A: The erosion resistance of the base layer (also called base material and substrate). How to better attach and fix it on a rocky slope without being washed down by rain. Soil is the condition for the survival of plants. For rocky slopes without soil, planting soil should be covered or artificial "soil" (matrix or exotic soil) should be sprayed. Physical, chemical and biological methods can be used to make these "soils" better attached to rock slopes. Physically, for example, metal mesh, plastic mesh, geotextile and concrete frame are nailed on the slope to fix the matrix, and grass fiber and wood fiber are added to the matrix for reinforcement to enhance its integrity. Chemically, cement or polymer binder is added to the spraying matrix to fix soil colloidal particles, and greening additives and polymer water retaining agent are added at the same time. The purpose of biology is to promote the seeds to germinate as soon as possible after the spray sowing is completed, and to fix the substrate by means of the "anchoring effect" of plant roots and stems and leaves to prevent the seeds from falling off. Even so, some slopes are worried that they are not stable enough and need a combination of engineering protection and biological protection, such as planting plants in concrete frame structures.

B: The principles of greening methods for many rock slopes are similar. The main components of the substrate are generally: plant propagator (such as seeds and grass stems), protective net, binder (or cementing material), polymer water-retaining agent, plant soil, organic matter, humus, fertilizer and greening additive. The physical and chemical properties of the matrix are determined by the composition and proportion of the matrix. Protective net: plastic, iron wire and steel bar can be used, and the choice of net and material should be determined according to the protection requirements and characteristics of slope. The function of the protective net is to protect the slope together with the anchor rod, and at the same time form the "skeleton" of the matrix, enhance the integrity of the matrix and prevent it from slipping off the slope. Binder: Different methods use different binders, some use high molecular organic substances, and some use ordinary silicate or 325 and 425 cement. These cementing materials can make the matrix mixture have cohesive force and certain strength. Polymer water-retaining agent: it can absorb water in abundant water and provide water for plant roots in drought. Plant soil: generally, it is mainly local soil, which is convenient for construction. When the local soil quality is too poor, sandy loam can be added to provide good water, fertilizer, gas and heat conditions for plant growth. Vegetation soil can be described as the "muscle" that constitutes the matrix. Organic matter: rice husk, broken straw, sawdust, etc. Usually used. The functions of these organic substances are: to increase the fluidity of matrix mixture and facilitate construction; Increasing the porosity of the matrix mixture and adjusting the water and gas conditions; After decomposition, it provides nutrients such as nitrogen, phosphorus and potassium for plants. Humus: it is made of rice husk, broken straw, sawdust and mushroom residue by decay. They can improve the physical and chemical properties of the substrate, introduce a large number of microorganisms into the substrate, coordinate the conditions of water, gas and heat, enhance the buffer performance of fertilizer conservation, and together with plant roots, make the substrate mixture gradually become soil suitable for plant growth. Fertilizer: Generally, it is a long-acting slow-release compound fertilizer, such as biological fertilizer and chemical compound fertilizer. If the matrix mixture is constructed into two layers, a certain amount of quick-acting fertilizer, such as urea, can be added to the surface layer to promote the seeds to germinate as soon as possible.

C: Combination of Grass and Irrigation ① Selection of Slope Protection Plants There are many lessons from the failure of stone slopes due to insufficient irrigation conditions, poor site conditions and improper vegetation selection. When selecting, we should consider that local cultivated grass is better than imported lawn grass, and local wild grass suitable for greening is better than cultivated grass, that is, slope protection plants should adapt to local climate and resist adverse environment; The root system is developed (deep root system), which grows rapidly and can reach a certain coverage in a short time; Have perennial habits and strong consolidation ability with soil; There are many tillers and lush stems and leaves; Strong resistance. (2) Plant configuration and combination of slope protection The main purpose of stone slope greening is slope protection. The plant configuration should follow the following principles: First, the combination of irrigation and grass can make full use of natural water, light and heat conditions, quickly establish three-dimensional ecological vegetation, maintain the long-term effect of slope greening, prevent lawn degradation, and continue and improve the function of soil and water conservation. Secondly, the arrangement of leguminous and gramineous plants is conducive to the development of interspecific advantages and mutual benefit. Grass (such as sainfoin+other grasses) is cultivated, and pioneer or protected grass seeds (such as perennial ryegrass) are added at the same time, so as to make use of its habit of early germination and fast growth to promote the germination of protected main grass seeds.

D: Measures to protect rocky slopes from drought include increasing the thickness of matrix layer, adding pore-forming agent and water-retaining agent to matrix, and selecting drought-resistant plants. However, due to the steep slope of rock slope and serious soil erosion, the function of water conservation and water supply of substrate planting layer is limited, which affects the effective regulation of water and the benign supply of nutrients. When it is difficult to ensure continuous dry and hot weather or spraying water, vegetation often turns yellow or dies. There is a lot of organic matter in the substrate as a long-term fertilizer, so there will be no nutrient depletion before a stable plant community is formed on the slope. However, the thickness of the substrate planting layer is limited, and the space for water and fertilizer circulation is very limited. With the increase of time, it is easy to cause ecological imbalance such as vegetation degradation on slope due to insufficient water and nutrient supply.

In a word, the greening design project of rocky slope should pay attention to the ecological and environmental protection function. According to the local ecological plant structure, the trees, shrubs and grasses should be organically combined and rationally allocated, so as to restore the original natural vegetation on the slope as soon as possible, integrate the vegetation of the protection project with the surrounding environment, restore its ecological balance, and realize the self-reproduction from artificial compulsory greening to natural vegetation. The comprehensive management project of rock slope mine ecosystem should pay attention to science, respect the laws of nature, be green when it is suitable, and be exposed when it is suitable, and not blindly pursue higher and unified green coverage rate. Because of the different geological structure and structure, rock properties and hardness, joint and bedding development, slope angle and surrounding vegetation environment, the construction difficulty and final effect of greening will be different.

I believe that after the above introduction, everyone has a certain detailed understanding of the greening technology of rock slopes. Welcome to Zhong Da for more information.

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