Cause analysis of mine geological environment problems

Mining development will more or less affect and destroy the geological environment. Some mine geological environment problems are inevitable, while others are closely related to the standardization of mining behavior. In a word, the main factors leading to mine geological environment problems in Hunan Province are mining behavior, mining, metallurgy, control technology and natural factors.

I. Factors of mining behavior

In the process of mining development, due to underground mining excavation and active caving, mine surface engineering construction, open-pit mining and topsoil stripping, it is difficult to avoid mine geological environment problems such as ground deformation, groundwater table decline and land resource occupation destruction. However, in the standardized mining activities or mining activities, taking effective measures to protect the mine geological environment in advance will greatly reduce or eliminate the degree of damage caused by mining activities to the mine geological environment, and even if damage occurs, it is easier to recover and control. Comprehensive analysis shows that a large number of environmental problems caused by improper mining behavior in Hunan Province are as follows:

1. Overexploitation and predatory development

Influenced by the idea of "mining large mines, opening small mines, fast water flow, and vigorously encouraging the development of private economy", the development of mining industry is disorderly. During the peak period, there were nearly 20,000 mines of various types in Hunan Province. According to incomplete statistics, from 65438 to 0998, there were a total of large and small mines 124 17 in Hunan Province, among which there were many illegal private adits. Some mining enterprises or private gangs are very serious, such as mining when they see the mine, blindly digging, crossing the layer and crossing the border, leaving no safety mine wall (column) or even stealing the row, which leads to a sharp outbreak of mine geological environment problems in the province, which is the main reason for the deterioration of mine geological environment problems in the early days.

2. Weak awareness of environmental protection and excessive pursuit of economic benefits.

In order to maximize economic benefits, environmental protection and prevention have been neglected in the process of mining in history, regardless of the interests of the environment and others. Mainly manifested in: waste residue is piled up at will, and it does not hesitate to occupy farmland, reservoirs and river valleys; No purification measures have been taken for wastewater discharge; Mining under residential areas, important facilities and basic farmland without safe pillars to form ultra-deep and ultra-wide mined-out areas; Illegal mining rights holders or illegal individuals illegally exploit safety pillar, etc.

3. There is a shortage of technical personnel for mine geological environment protection.

At present, there are many small mines, or there are no technicians in environmental protection, or the existing technicians lack professional knowledge in hydraulic environment, and they don't understand or know enough about the mining technical conditions such as hydrogeological conditions and engineering geological conditions and their complexity, and they don't take scientific and reasonable preventive measures for possible geological environmental problems, which unconsciously causes the destruction of mine geological environment, which is an important factor causing the geological environmental problems of mines in Hunan Province.

4. Local protectionism is too heavy.

In some places, the development of mineral resources has become the main economic pillar and the largest source of local finance. In the historical period, some local governments and departments unilaterally understood that "development is the last word", and there was a misunderstanding of "developing first, then improving ecology and protecting the environment", which failed to implement the requirements of rectifying the management order of mineral resources, shutting down small mines and protecting mine geological environment, which aggravated the destruction of mine geological environment.

Second, technical factors.

1. The backward mining and dressing technology in the mine has aggravated the occurrence of geological environment problems in the mine.

Restricted by mineral resources endowment, the mining technology is backward, and backward mining technologies such as caving method and cannon are adopted, resulting in geological disasters such as ground collapse, collapse and landslide. Some underground mining mines are backward in water exploration technology, and the detection of old kiln, old goaf and karst pipeline is incomplete, which leads to water inrush and mud outburst accidents and ground collapse. The mineral processing technology is simple and backward. For example, there used to be a large number of indigenous gold mines, indigenous mercury mines, arsenic mines, sulfur mines, alum mines, lead-zinc mines and cyanide mines in this province, which caused pollution to the geological environment of mines. Many mineral resources in the province, especially non-ferrous metal resources, are rich in raw ore and poor in ore. Due to backward mineral processing technology and low level of comprehensive utilization of resources, the total recovery rate is only about 40%. The low level of comprehensive utilization not only wastes resources and increases the discharge of solid waste, but also increases the discharge of heavy metals in tailings, which aggravates the environmental impact.

2. The comprehensive utilization rate of waste residue and waste water is low, and the technology of mine geological environment restoration and treatment is backward.

In the process of mining activities, a lot of waste residue and wastewater will be discharged. Comprehensive utilization of them can not only turn waste into treasure, save resources, but also effectively protect the mine geological environment. The comprehensive treatment rate of mine waste residue and wastewater in Hunan Province is not high, and the comprehensive utilization rates of mine waste residue and wastewater are 26.83% and 1 1.89% respectively. At the same time, at present, the technical level of comprehensive treatment and utilization of mining waste residue and wastewater in this province is low, and the methods and technologies are backward. The restoration and treatment of mine geological environment is a professional technical work, but the research on mine geological disaster prevention and land reclamation technology in mining areas is still very weak. For example, ground deformation monitoring can effectively prevent ground subsidence and ground deformation from damaging ground facilities, but at present, ground deformation monitoring is still in the exploratory research stage, and there is no complete and economical monitoring technology system to control ground deformation as soon as possible. As far as land reclamation is concerned, it is very difficult to control water and soil pollution represented by heavy metal pollution caused by mining wastewater and waste residue. At present, there is no universal control technology to restore and control the polluted and destroyed land, which leads to the slow progress in restoring and controlling the destroyed land.

Third, financial factors.

Historically, due to the pursuit of maximizing economic benefits, mine owners often did not take the initiative to prevent and control the risk of mine geological environment damage in time. Even if there is a problem, it has not invested enough money in governance and repair, resulting in a large number of environmental problems. Although the state and local governments and mining rights owners have invested a lot of money in the governance of mine geological environment problems in the past decade, there are many historical debts and the governance area is limited.

Fourth, natural factors.

Mining activities destroy the equilibrium conditions of mine geological environment, which is the fundamental cause of mine geological environment problems, and the fragile state of mine geological environment in Hunan Province is another factor that mining activities easily lead to the aggravation of mine geological environment problems.

(1) Meteorology and Hydrology

Hunan Province is rich in precipitation, but it is unevenly distributed during the year. The average annual precipitation in Hunan Province is 1426.6 mm, with a maximum of 3,089 mm. Due to abundant and concentrated rainfall, heavy rains often occur, with a maximum daily rainfall of 423.438 0 mm. Rainfall is an important factor for mine collapse, landslide, debris flow, ground subsidence and soil erosion in Hunan. Climatic conditions are very favorable to the weathering of rocks, and the weathering of rocks in many mining areas is strong, which reduces the integrity and stability of rock mass. At the same time, strong weathering also reduces the stability of waste rock piles and is prone to mine geological disasters. Hunan monsoon changes greatly, and the dry wind is strong in summer and autumn, which is one of the reasons for dust pollution in tailings pond. The surface water system is developed and the river network is dense. There is a hydraulic connection between surface water and groundwater in many mining areas, and surface water often becomes the main source of mine water filling and water inrush. Especially with the appearance of extreme weather such as long-term drought and rainstorm, a large number of mine geological environment problems have been caused.

(2) topography

Deep ditches and rivers with strong topographic cutting are the most favorable areas for landslides. Collapse and landslide are also very developed in the slope zone between terraces and stripping surfaces at all levels; The upper part of the broken-line hillside is horseshoe-shaped, and when the catchment area is large, it is easy to produce soil landslides sliding along the bedrock surface. Most nonferrous metal deposits in Hunan are located in mountainous areas, and geological disasters such as collapse, landslide and debris flow are prone to occur under complex terrain conditions.

(3) Geological environment conditions of the deposit

The main ore-bearing strata of energy minerals in Hunan Province are Permian Longtan coal measures and Carboniferous water-water coal measures, followed by Permian Wujiaping coal measures, Permian Qianyang coal measures, Upper Triassic coal measures and Lower Jurassic coal measures. The lithology of each coal-bearing series is mainly siltstone, shale, mudstone mixed with sandstone or interbedded. The mechanical strength of shale and mudstone is low, and the engineering geological conditions of mines are mostly medium to poor. However, the roof, floor or roof and floor of the northern section of Longtan coal measures, Wujiaping coal measures and Qianyang coal measures are carbonate rocks, with karst development, rich karst groundwater, developed fault structures and strong water conductivity, and the hydrogeological conditions and mining structure are mostly complicated. The main occurrence horizons of gypsum minerals in building materials mines are Zimenqiao Formation, Cretaceous and Paleogene of Lower Carboniferous, in which the direct roof of gypsum-bearing rock series in Zimenqiao Formation is limestone in the upper member of Zimenqiao Formation with moderate to strong karst development, and the indirect roof is Hutian Formation with strong karst development. The hydrogeological conditions are mostly complex to moderate, and the lithology of gypsum-bearing rock series in Cretaceous and Paleogene is mudstone and siltstone, with low degree of rock consolidation and low mechanical strength. The main nonferrous metal deposits such as Shizhuyuan polymetallic deposit, Huangshaping deposit, Baoshan deposit, Shuikoushan lead-zinc deposit and Qibaoshan gold-silver pyrite deposit are all contact metasomatic deposits, and their host strata are all carbonate rocks with karst development, with complex hydrogeological conditions. The ore-hosting stratum of Huayuan lead-zinc deposit is also Qingxudong Fm limestone of Lower Cambrian, and karst poles such as underground rivers are developed. When mining the above mineral resources, due to poor engineering geological conditions, it is easy to cause mine geological disasters such as ground deformation mines in goaf; Complicated hydrogeological conditions easily lead to karst ground collapse and the destruction of aquifer structure. This is also the reason why the ground deformation disasters in mined-out areas in Hunan Province are mainly related to coal mines such as Shuishui coal measures, Longtan coal measures (south type) and gypsum mines, and karst collapse and aquifer structure destruction are mainly related to non-ferrous metal mines such as Longtan coal measures (north type), Wujiaping coal measures, Qianyang coal measures, Shizhuyuan polymetallic mine, Huangshaping, Baoshan lead-zinc mine and Qibaoshan polymetallic mine.

Most open-pit mines in Hunan Province are sandstone clay mines, and quarries such as granite, limestone and quartzite have a high degree of weathering. When joints and fissures develop and steep free surfaces are formed during mining, they are easy to collapse. Quarry soil (sand) is the mining object of sand mining field, brick and tile factory, kaolin mine, lateritic gold mine and eluvial manganese mine, which has low mechanical strength and is easy to soften when it meets water, and the stope slope is easy to collapse and slide. In addition, most stone coal mines are open-pit mining, and some sedimentary iron ore and phosphate ore are also open-pit mining. The ore-bearing strata are mainly Jiangkou Formation, Doushantuo Formation and Xiaoyanxi Formation from Sinian to Cambrian, and the lithology is mostly slate, carbonaceous slate and sandy slate. In addition to bedding, bedding and cleavage are developed, and shallow weathered joints are developed, so the stope slope is prone to landslide and collapse. At the same time, there are a lot of stripped waste rocks and mining waste rocks in the stope, which often become the material source of debris flow.

The waste residue and waste water of nonferrous metal and stone coal mines contain a lot of heavy metal elements and radioactive elements, the waste residue and waste water of chemical salt mines contain halogen elements, and the waste residue and waste water of medium-high sulfur coal mines and pyrite mines contain a lot of pyrite, which are the sources of pollutants in mine water and soil pollution.