Environmental geological impact assessment and ecological restoration of abandoned mines

2.1 Impact of function zones of abandoned mines on the environment

Abandoned mines generally include slag dumps, mining dumps, tailings dumps and other abandoned lands. Due to different causes, the impact on the environment is also different. This paper discusses its impact on the environment from many aspects.

In mining, low-quality ore is often thrown away directly, resulting in a large amount of waste accumulation. Due to its relatively chaotic geological conditions, the rock layers are very loose, and there is not much organic matter, it is difficult to form rich vegetation on the surface, and therefore, it is more likely to cause soil erosion and uneven settlement. There are a lot of harmful elements in the abandoned mines and tailings abandoned land produced by mining. Some mineral elements, due to long-term exposure and oxidation, will produce spontaneous combustion and explosion risk; At the same time, these harmful substances will also penetrate into the soil with the rain, and then enter the water cycle, which will lead to greater environmental pollution. The environmental problems of the buildings built in the mining process and the abandoned land formed by the leftovers and wastes after mining are mainly manifested as a large amount of land waste and the processing equipment has the capacity of secondary use but is idle and abandoned, forming a new environmental hidden danger.

2.2 Specific harm to the environment caused by abandoned mines

Specifically, the impact of mine abandonment on ecological environment is multifaceted. First, due to the large consumption of abandoned mines, more fertile farmland has become barren. However, the per capita cultivated land resources are low, facing a large number of mines desertification, resulting in a large amount of resource waste. Secondly, the abandonment of mines has caused severe damage to the soil and surface topography, and the drastic movement and deformation of rock strata and upper soil layer caused by mining. Irreparable damage to vegetation and terrain. In addition, it also has a certain impact on the overall balance of regional ecosystems. For example, in the relatively dry areas of Northwest China, vegetation itself has a strong ability to prevent wind and fix sand. The exploitation of mineral resources has led to the intensification of desertification, and has local negative effects on precipitation, temperature and humidity. In the south, open-pit mining of rare earth minerals mixes with rainwater, releasing heavy metals that threaten surrounding rivers and residents.

3. Mine environmental impact assessment

On the whole, the environmental impact assessment of mine is carried out with the disaster body as the object, and with the increasing awareness of environmental protection today, the problem of visual pollution caused by it is getting more and more attention. In recent years, with the frequent occurrence of environmental pollution accidents caused by mining, the pollution risk assessment of soil and groundwater has been paid more and more attention.

3.1 Geological hazard assessment

3.1.1 Overall slope stability assessment

The surrounding mining area generally belongs to the hilly and mountainous landform units, the surface soil cover is very shallow, and some surface bedrock is exposed. Taking the adjacent mining area as an example, several fault zones develop around the mining area, and local bedrock folds and rock joints are relatively developed, but in general, the ratio is relatively stable. Due to the influence of mining, the rock mass will appear large slide, spalling and other bad geological phenomena.

3.1.2 Risk assessment of stope slope

Non-metallic minerals are mostly open-pit mining. Taking the surrounding abandoned mines as an example, the rock joint cracks of the mining site are developed, and there are no obvious geological disasters such as landslide, collapse, ground subsidence, ground cracks and debris flow within the mining area. The slope of the mining site is generally relatively stable, but there are still small pieces of dangerous rock and pumice on the slope and slope of the mining site. There are often small pieces of rubble rolling down the slope, collapse, poor stability.

3.1.3 Stability evaluation of slag dump

The form of slag accumulation is near fan, taking the surrounding abandoned mine as an example, its heap contains a lot of slag and a little soil, with a large height difference; The slope is usually steeper and larger. The compaction degree of waste slag pile is poor, the interior is loose, and the stability is very poor. If there are other inducements such as heavy rain, it is easy to cause geological disasters such as debris flow and landslide.

3.2 Destruction of landform and landscape

Open-pit mining is the most economical mining method, and its special mining method has caused great damage to the terrain and landform of the mining area and its surroundings. The vegetation on the ground has been cut down artificially, forming pits and deposits, which have greatly changed the terrain and caused changes in the mountain form and vegetation. Due to the perennial construction of mining roads and mining areas, the landform and vegetation resources in the mining area have been seriously damaged. However, due to the lack of detailed topographic and geomorphic damage assessment system, it is difficult to evaluate it quantitatively. It is gratifying that in recent years, a number of ecological restoration projects have been carried out in the Yangtze River area, and the vegetation of abandoned mines has been better restored.