Xinjiang is rich in limestone mineral resources, which are mainly used for the production of cement, building stone, lime, calcium carbide, and flux. The development of limestone mineral resources has provided a strong resource guarantee for the rapid social and economic development of Xinjiang, but also caused some geological environmental problems of mines. Today, we have collected information on the development and utilization of limestone mines in Xinjiang, investigated the problems existing in mining and the situation of restoration and management, summed up the common geological environmental problems existing in limestone mines, and put forward suggestions for restoration and management in response to the corresponding problems.
Overview of Xinjiang Limestone Mine
Limestone is a common non-metallic mineral and a valuable resource with a wide range of uses. Limestone is not only an indispensable and important raw material for the cement and ash making industry, but also widely used in construction stone, calcium carbide, flux and other industries.
A total of 338 limestone mineral deposits have been discovered in Xinjiang. The deposits range from super-large to ore deposits, mainly small and medium-sized deposits, including 4 super-large deposits, 26 large deposits, 48 medium-sized deposits, and 205 small deposits. , mine site 55. There are 237 limestone mines developed and utilized in Xinjiang, including 161 limestone for cement, 56 limestone for construction stone, 16 limestone for lime making, 2 limestone for calcium carbide, and 2 limestone for flux (Table 1). The limestone mines that have been developed and utilized are widely distributed. Aksu, Changji, Bazhou, Bozhou and Urumqi are the main bases for limestone mining in Xinjiang.
Existing geological environment problems
The mining methods of limestone mines for different purposes are usually the same, generally adopting hillside-sag open-pit mining, top-down, horizontal layered and stepped mining. The main mining and stripping processes in Xinjiang limestone mines are: open-pit DTH drilling of medium and deep holes—single-row or multi-row hole loosening and blasting—diesel-powered excavator mining and loading—dump truck transportation. Because the mining methods of limestone mines for different purposes are basically the same, the geological environment problems existing in mining are basically the same.
Slope Geological Hazards
The hidden dangers of geological hazards in limestone mines generally appear on the slopes of mining pits, mine road slopes and waste rock yard slopes.
1. Slope of mining pit: limestone mines generally adopt the mining method of open-pit hillside-sag. Along with the mining, open-pit depression mining pits are often formed. The high and steep slopes formed by the mining pits provide favorable spatial conditions for collapse, and the high and steep terrain It will promote the development of unloading cracks, and with the further development of cracks, it may cause geological disasters of collapse. If the slope inclination and the inclination of the rock formation are the same, the slope angle of the step should not be greater than the inclination angle of the rock formation, otherwise the lower part of the rock formation will be damaged during mining, which will easily lead to the geological disaster of bedding landslides;
2. Mine road side slope: some high and steep side slopes are formed during the construction of mine roads. Similar to the situation of mining pit side slopes, it may also cause geological disasters such as collapse and layered landslides; 3. Rocks will roll down under the action of gravity, blasting vibration, etc., resulting in collapse geological disasters. If the slope angle of the waste rock yard is too large, under the influence of rainfall, a weak structural plane may be formed, resulting in landslide geological disasters.
Topography problem
Mining activities cause changes and damage to the original topography. The ground construction project layout formed by limestone mining mainly includes open-pit mining fields, waste rock dumps, topsoil dumps, management areas, living areas, crushing areas, etc. It will cause the destruction of vegetation, the change of landform and affect the visual landscape (Figure 1). The damage degree of the mine to the topography can be divided into three categories: serious, serious and light according to the damage area, the degree of damage, and the distance from various nature reserves, cultural landscapes, scenic tourist areas, surrounding cities, and main traffic arteries. grade. At present, many mines are not standardized in mining. They do not follow the top-to-bottom horizontal layered and stepped mining method. The stope is messy, and the waste rocks are piled up indiscriminately, which increases the impact and damage on the topography.
Cause soil and water pollution
Limestone mines generally only carry out physical quarrying, and some mines will set up crushing lines in the mining area for ore crushing. There is no chemical sorting process, and heavy metal elements will not be sorted. Therefore, the mining process of limestone generally has little impact on water and soil environmental pollution. There are toxic and harmful pollutants in the domestic garbage and domestic sewage generated by the mine workers. The random disposal of domestic garbage will cause pollution to the environment, and the direct discharge of domestic sewage without treatment will also pollute the water and soil environment. In some mines, waste oil is discharged at will, which will pollute soil and water bodies.
Cause air pollution
The mines basically do not use outdated production process equipment and mechanical equipment that are explicitly eliminated by the state, and the exhaust emissions of mechanical equipment meet the national emission standards. The main air pollution in the mining process is dust pollution. The main dust-producing links in limestone mines are: dust from blasting, crushing, loading and unloading, and transportation. The main effects are: dust floating in the air, increasing the content of suspended solids in the local air, and affecting the regional landscape at the same time; dust in the air falling on the rotating parts of the machine will accelerate the wear of the rotating parts and reduce the precision and accuracy of the machine work. Long-term life; long-term exposure of miners to dust in a bad working environment will have a certain impact on their health.
Conclusions and Recommendations
(1) Xinjiang has discovered 338 limestone mineral deposits, and 237 limestone mines have been developed and utilized, which are widely used in industries such as cement, construction stone, ash making, calcium carbide, and flux, with a wide range of applications and a large amount of use. The main geological and environmental problems caused by limestone mining include slope geological disasters, topography, waste rock fields, water and soil environmental pollution, and atmospheric environmental pollution.
(2) For slope geological disasters, production mines mine and pile up waste rocks according to the design requirements, and special treatment measures should be designed for slopes with greater risk of geological disasters; abandoned mines should clean up dangerous rocks and cut slopes. ramp to a steady state. For topographic and landform problems, production mines should minimize the disturbance area; abandoned mines can be treated and restored by measures such as waste rock backfilling, slope cutting, leveling, and vegetation reconstruction.
For the problem of waste rock yard, improve the comprehensive utilization rate of waste rock and reduce waste rock discharge. The waste rock that cannot be used can be backfilled to the mining pit after the mine is closed. For water and soil environmental pollution, domestic garbage is stored in garbage bins and regularly transported to garbage treatment stations for unified treatment. For the problem of atmospheric environmental pollution, dust removal and dust capture equipment is installed at fixed dust production points, and water trucks are arranged on transport roads and other sites to sprinkle water regularly to reduce dust.
(3) Limestone mines have played an important role in social and economic development. In order to do a good job in geological environment management and land reclamation during and after mining, it is necessary to choose recovery and governance measures with good recovery effects and economic feasibility according to local conditions, so as to promote Mine ecological civilization construction, and practice the goal of green mine construction.
Mine geological environmental protection and restoration work should be combined with green mine construction work. For mines that are going to carry out green mine construction, geological environmental protection and restoration work are included in the scope of green mine construction work and are part of green mine construction. In practice, large and medium-sized mines should carry out green mine construction and evaluation and storage work as soon as possible, and small mines and three types of mineral mines should be managed in accordance with the requirements of green mine construction.