Abandoned mines do more harm! Mine ecological restoration, so to operate

What are the hazards of abandoned mines

If the abandoned mine is not properly treated, it will have an important impact on the surrounding environment.

Water pollution

After mine collection, mine closure will lead to the accumulation of a large amount of groundwater in the mine, and the residue in the mine will pollute the water quality, and the polluted water will penetrate into the surface and circulate with each other, resulting in an increasingly large area of water pollution.

Dust pollution

Mining will seriously damage the surrounding vegetation and ecological environment, after the mine abandoned, a large number of gravel, loose slag exposed to the surface, will cause serious dust pollution.

Toxic gas pollution

After the mine is abandoned and closed, the toxic gas in the mine can not be discharged, and the long-term accumulation of toxic gas is more and more. Once there is a crack or collapse, the toxic gas will spread into the air, causing pollution to the surrounding environment and endangering human health.

Landslides and other geological disasters

After mining inside the mine will lead to internal empty, after long-term rain or internal sewage erosion, to a certain extent will cause landslides or landslides, the life safety of the surrounding population has a great threat.

Mine rehabilitation technology

(1) Soil treatment and improvement

Soil treatment and improvement is an important and primary link of ecological environment restoration in mining areas, including the treatment and improvement of soil quality around mining areas, and the treatment and improvement of the performance of tailings and waste ore piles covering the soil. The reason why it is important is that the restoration of vegetation must be based on the premise that the improvement of soil governance has achieved results, otherwise, any plant planted in the soil of the mining area will not grow or grow difficult, and vegetation restoration will become impossible. Soil treatment and improvement can be summarized into three methods: physical methods, chemical methods and biological methods.

Physical improvement: including topsoil transfer and guest soil backfill two kinds. The application of topsoil transfer method is limited, only used in newly opened mines and newly built tailings fields, and now it is widely used in soil remediation work in open iron mines. Another kind of backfill technology is obviously effective, but expensive.

Chemical improvement: The main use of chemical methods, the use of chemical additives to reduce or remove pollutants. Chemical repair technology is used earlier and relatively mature, but special attention should be paid to the use of chemical additives can not produce secondary pollution.

Biological improvement: mainly refers to the use of biological methods, the use of animals, plants and microorganisms to let the pollutants remaining in the soil be absorbed, degraded and transformed, so that the concentration of pollutants is reduced, the soil index is restored to the safe range, or the toxic and harmful pollutants become harmless, or the pollutants are stable and do not spread to the surrounding environment. Its advantage is economic, will not cause re-pollution to the environment, the disadvantage is that the repair time is long, the use of animals, plants, microorganisms are affected by the external environment, the repair effect is unstable.

(2) Vegetation restoration

The restoration of ecosystem should be based on the premise of obtaining the maximum benefit with the least investment and the shortest time, and the restoration of vegetation is no exception. On the basis of research and learning from domestic and foreign experience, the pollution elements should be analyzed first, and then the physicochemical and biochemical properties of soil should be analyzed to find out the soil pH value, soil water content, air permeability, soil nitrogen and soil temperature, etc. Then choose the tree species. In addition, the preliminary study of pollutants and vegetation in mining area shows that different plants have certain adaptability to different pollutants, and these plants are mostly tolerant plants of this kind of pollutants. Therefore, the selection of these plants has to go through a lot of optimization work, which consumes a huge amount of time and energy. The restoration of vegetation is the key and difficult point of ecological environment restoration in mining area. Only when vegetation is restored in mining area can the original mining area landscape be restored.

(3) Joint repair of plants and fungi

Mycorrhiza is a combination of fungal mycelia in soil and vegetative roots of higher plants. A survey of plants in British mining areas found that plants were sparse in mining areas with high metal content, especially heavy metals. Most of the surviving plants are mycorrhizal plants, and the growth is better than that of non-mycorrhizal plants. Mycorrhizas containing a large number of microorganisms are a complex group, including actinomyces, azotobacter and fungi. These fungi have a certain ability to degrade pollution; At the same time, the microecology provided by the mycorrhizal rhizosphere enables the mycorrhizal rhizosphere to maintain a higher microbial population density and physiological activity, thus making the microbial flora more stable. Mycelium extending on the surface of mycorrhiza can greatly increase the absorption area of roots. Most mycorrhiza fungi have strong acid-soluble and enzymolysis capabilities, which can absorb and transfer nutrients for plants, and can synthesize plant hormones to promote plant growth. The activity of mycorrhizal fungi can also improve the rhizosphere microecological environment of plants, enhance the disease resistance of plants, and greatly improve the survival ability of plants under adverse conditions.

(4) Mining area restoration

The restoration of ecological environment in mining area is to restore the original landscape as the ultimate goal, and the restoration of vegetation in mining area is the most basic result of landscape restoration in mining area. However, it is far from enough to restore the vegetation in the mining area, and the following engineering measures need to be taken, and combined with the previous methods and measures, in order to achieve the goal of restoring the original mining area landscape as soon as possible.

1. Ecological restoration in mining areas

The mining technology to reduce surface subsidence should be adopted and the filling mining technology should be popularized. The subsidence area of the surface should be reduced as far as possible, and waste rock filling and topsoil covering should be adopted in the place where ground cracks have been caused, and finally the vegetation should be restored. After open-pit mining, many rock slopes with steep slope and steps with small width are formed. Therefore, when ecological restoration is carried out in the open-pit mining area, the slopes formed should be treated in different degrees. For slopes with slope slope greater than 75°, ecological environment restoration measures should be carried out under the premise of ensuring slope stability.

2. Reclamation of waste dump

To restore the ecological environment of the dump site, firstly, the slope stability should be ensured, and secondly, engineering measures should be combined with plant measures, mainly planting trees and grass. Engineering measures should be taken to deal with the slope with hidden safety risks, which mainly include the construction of barrage dam, slope cutting and grade opening, the construction of anti-slide pile, deep space prestressed anchor, long anchor reinforcement and other engineering measures. The plant species selected by the plant measures of the dump site should have strong resistance and good quality. The methods of planting trees mainly include soil pile bag, hanging net greening, planting bag, planting plate, etc. When the waste dump is restored to forest land, it should be covered with soil, the thickness should be greater than 30cm; If pit planting is used, a small amount of guest soil can be filled in the pit; General trees can be planted in the slope zone with slope less than 35°.

3. Reclamation of tailings pond

The reclamation work of tailings pond should be carried out after ensuring its complete closure and the stability of the entire engineering facilities, and the reclamation work should be adjusted according to its actual nature. Whether the tailings are acidic or alkaline, it should be deeply treated according to the utilization direction of the site. When the tailings contain radioactive and toxic substances, it should be determined whether it is necessary to set up an isolation layer according to its content level, and cover it as deep as possible; When the salt content of the tailings is large, it should be desalt treatment, or deep covering treatment. At the same time, drainage facilities should be set up around the tailings pond, and the drainage facilities must meet certain flood control standards.

4. Ecological restoration of waste discharge field

The primary task of ecological restoration of waste heap is to stabilize the slope of waste heap, which is dominated by slopes and hills. The main measures include horizontal land preparation, stabilizing slope surface and reducing the relative height of gangue hill. Before the gangue stacking, the bottom of the ditch must be flattened and tamped, and the gangue stacking shall be stacked in layers of 3m, and the width of the steps shall be greater than 3m. The stacking sequence is from gully to gully mouth, layer by layer compaction, and at the same time, slag dam and slurry stone drainage ditch are set up at the gully mouth. Diversion channels are arranged at intervals of 15m in the slope zone, and the layers are scattered and arranged in the shape of "goods". Secondly, topsoil covering is carried out in the discharge field. Finally, according to the nature of the soil and local climate conditions, the appropriate vegetation is selected for planting.

In the process of mining, a large amount of land has become abandoned land due to the loss of utilization value, such as open-pit stope, waste rock yard, tailings reservoir, subsidence area, etc. Mine restoration is to repair the pollution of abandoned mining land and realize the reuse of land resources.

Ecological restoration of abandoned mines needs to go through a long process, so it is necessary to work out a perfect treatment plan according to the actual needs of mine ecological restoration projects. For the mine ecological restoration, it is necessary to follow the principle of ecological restoration to improve the soil, vegetation, biology and other aspects, and adopt appropriate technical measures to restore the mine ecological restoration, so as to ensure the smooth progress of the mine ecological restoration project.