Analysis of the causes of mine geological environmental problems

Mining development will more or less cause damage to the geological environment. The occurrence of geological environmental problems in some mines is inevitable, and the occurrence of geological environmental problems in some mines is closely related to the standardization of mining behavior. In short, The factors leading to geological environmental problems in mining in Hunan Province mainly include mining behavior, mining, processing, smelting and treatment technology, and natural factors.

1. Mining behavioral factors

In the process of mining development activities, mining behaviors such as underground mining excavation and active roof caving, mine surface engineering construction, open-pit excavation and topsoil stripping, etc., It is difficult to avoid the occurrence of mine geological environmental problems such as goaf ground deformation, groundwater level decline, land resource occupation and destruction, etc. This is due to the basic attributes of mining activities. However, standardized mining activities or proactive and effective mine geological environment protection measures taken in advance during mining activities will greatly reduce or eliminate the damage caused by mining activities to the mine geological environment. Even if damage occurs, its restoration and management will be easier. Comprehensive analysis shows that the main aspects that currently lead to a large number of environmental problems due to inappropriate mining practices in Hunan Province are:

1. Over-exploitation and predatory mining

Influenced by the "big mines and big mining" Influenced by the idea of ??"opening up small mines, allowing water to flow quickly, and vigorously encouraging the development of the private economy", the development of mining industry was disordered. At its peak, there were nearly 20,000 mines of various types in Hunan Province. According to incomplete statistics, in 1998, there were 12,417 mines of various sizes in Hunan Province, and there were also many illegal mining and civilian mining tunnels. Some mining companies or private groups mine as soon as they see the mines, blindly mine indiscriminately, cross layers and boundaries, fail to set up or even secretly mine security mine walls (pillars), etc. The phenomenon is very serious, which has led to a sharp outbreak of geological and environmental problems in the province's mines. The main reason for the deterioration of mine geological environmental problems.

2. Weak environmental awareness and excessive pursuit of economic benefits

In order to maximize economic benefits, historically, regardless of the environment and the interests of others, environmental protection and prevention were not paid attention to during the mining process. . The main manifestations are: waste residues are piled up at will without hesitation to occupy farmland, reservoirs, and river valleys; wastewater is discharged indiscriminately without taking any purification measures; mining under residential areas, important facility areas, and basic farmland does not leave security pillars, forming ultra-deep, ultra-deep Wide goaf areas; illegal mining right holders or illegal individuals illegally mining security pillars, etc.

3. Lack of technical personnel in mining geological environmental protection

Many existing small mines either do not have environmental protection technicians or have technical personnel with hydraulic and environmental expertise. Lack of understanding or insufficient understanding of mining technical conditions such as hydrogeological conditions, engineering geological conditions and their complexity of mineral deposits, and failure to take scientific and reasonable preventive measures for possible geological environmental problems that may arise, unknowingly causing damage to the geological environment of the mine. The damage is an important factor causing geological environmental problems in mining in Hunan Province.

4. Excessive local protectionism

In some places, the development of mineral resources has become the main economic pillar of the local area and the largest source of local finance. During the historical period, some local governments and departments one-sidedly understood that "development is the last word" and had the wrong understanding of "development first, then improve ecology and protect the environment." They rectified the management of mineral resources, closed down small mines, and protected mine geology. Inadequate implementation of environmental requirements has aggravated the damage to the geological environment of mines.

II. Technical Factors

1. The mining and dressing technology of mines is backward, exacerbating the occurrence of mine geological environmental problems

Restricted by the endowment conditions of mineral resources, mines Mining technology is backward, and backward mining techniques such as "collapse method" and "big cannon" are used, causing geological disasters such as ground subsidence, collapse, and landslides. The water detection technology of some underground mining mines is backward, and the detection of old kilns, old goafs, and karst pipelines is incomplete, resulting in water and mud inrush accidents, resulting in ground collapse. The mineral processing technology is simple and backward. For example, there used to be a large number of mines in the province that mined and processed gold ore, smelted mercury, arsenic, sulfur, vitriol, lead and zinc, and cyanide mineral processing in the province, which caused pollution to the geological environment of the mines. There are many mineral resources in the province, especially non-ferrous metal resources. There are many secondary (associated) ores and lean ores. Due to backward mineral processing technology, the comprehensive utilization level of resources is low. The total recovery rate is only about 40%, and the comprehensive utilization level is low. It not only wastes resources and increases solid waste emissions, but also increases the emissions of heavy metals in tailings, aggravating the environmental impact.

2. The degree of comprehensive utilization of waste residue and wastewater is low, and the mining geological environment restoration and management technology is backward

A large amount of waste residue and wastewater are discharged during mining activities. Their comprehensive utilization can not only change the Turn waste into treasure, save resources, and effectively protect the geological environment of the mine. The comprehensive treatment rate of mining waste residue and wastewater in Hunan Province is not high. The comprehensive utilization rate of mining waste residue and wastewater is 26.83% and 11.89%. At the same time, the current technical level of comprehensive treatment and utilization of mining waste residue and wastewater in the province is relatively low, and the methods and techniques are relatively backward. The restoration and management of mine geological environment is a highly professional and technical task, but the current research on mine geological disaster prevention and mining area land reclamation technology is still very weak. For example, ground deformation monitoring can effectively prevent ground collapse and goaf ground deformation from damaging ground facilities. However, ground deformation monitoring is still in the exploratory research stage, and there is no complete, economical and applicable monitoring technology system to control ground deformation early.

As far as land reclamation is concerned, it is difficult to control water and soil pollution represented by heavy metal pollution caused by mining wastewater and waste residues. At present, there is no universal treatment technology to restore and treat the polluted and damaged land, resulting in the destruction of the land. Progress in restoring governance has been very slow.

3. Financial factors

Historically, because mining rights holders pursue maximizing economic benefits, they often do not take the initiative to promptly prevent and control the risks of damage to the geological environment of mines. Even if problems have arisen, sufficient funds are not invested in governance and restoration, resulting in a large number of environmental problems remaining. Although the national and local governments and mining rights holders have invested a large amount of funds in the treatment of mining geological environmental problems in the past ten years, there are many historical debts and the treatment area is limited.

IV. Natural factors

Mining activities destroy the balanced conditions of the geological environment of mines, which is the fundamental cause of geological environmental problems in mines. However, the fragile geological environmental conditions of mines in Hunan Province are easily caused by mining activities. Another factor that intensifies the geological and environmental problems in mines.

(1) Meteorology and Hydrology

Hunan Province has abundant precipitation, but its annual distribution is uneven. The multi-year average precipitation in the province is 1426.6mm, with the maximum reaching 3089mm. Due to abundant atmospheric precipitation and concentrated rainfall, heavy rains often occur, with the maximum daily rainfall reaching 423.1mm. Rainfall is an important factor causing collapses, landslides, debris flows, ground subsidence and soil erosion in Hunan mines. Climatic conditions are very conducive to the weathering of rocks. In many mining areas, rocks are strongly weathered, reducing the integrity and stability of the rock mass. At the same time, strong weathering also reduces the stability of waste rock piles, which can easily cause geological disasters in mines. Hunan's monsoon changes greatly, and dry winds are strong in summer and autumn, which is one of the reasons for dust pollution in tailings ponds. 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. Surface water often becomes the main source of water filling and water inrush in mines. Especially the occurrence of extreme weather, such as long drought followed by heavy rain, will cause a large number of mining geological environmental problems.

(2) Topography

The deep ravines and rivers with strong topography are the most favorable areas for collapses and landslides; the slope areas between terraces and stripping surfaces at all levels are the most favorable areas for collapses and landslides. Landslides are also very developed; on slopes with steep tops and bottoms and gentle breaks in the middle, when the upper part of the hillside forms a horseshoe-shaped ring topography and the water catchment area is large, soil landslides sliding along the bedrock surface are prone to occur. Nonferrous metal deposits in Hunan are mostly found in high mountains and ridges, and the complex terrain conditions are prone to geological disasters such as collapses, landslides, and debris flows.

(3) Geological and environmental conditions of mineral deposits

The energy mineral deposits in Hunan Province are mainly the Permian Longtan coal series and the Carboniferous hydrocarbon coal series, followed by the Permian Wujiaping coal Series, Permian Qianyang Coal Series, Upper Triassic, Lower Jurassic coal-bearing rock series, etc. The lithology of each coal-bearing rock series is mainly siltstone, shale, mudstone interbedded 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; while the northern type of Longtan coal series and Wujiaping coal series The roof, floor or roof and floor of the Qianyang Coal Measures are karst-developed carbonate rock salts rich in karst groundwater. The fault structures are developed and have strong hydraulic conductivity. The hydrogeological conditions and mining area structures are mostly complex. The main occurrence layers of gypsum minerals in building materials mines include the Lower Carboniferous Zimenqiao Formation, the Cretaceous System, and the Paleogene-Neogene System. Among them, the direct roof of the gypsum-bearing rock series of the Zimenqiao Formation is the Zimenqiao Formation with moderate to strong karst development. The upper section of the formation is limestone, and the indirect roof is the Hutian Group with strong karst development. The hydrogeological conditions are mostly complex to moderate. The lithology of the Cretaceous and Paleogene-Neogene gypsum-bearing rock series is mostly mudstone and siltstone. The degree of rock consolidation is The mechanical strength of the rock mass is low, and the engineering geological conditions of the mineral deposits are mostly poor. Major non-ferrous metal deposits such as the Shizhuyuan polymetallic mine, Huangshaping, Baoshan, Shuikoushan lead-zinc mine, and Qibaoshan gold-silver pyrite in Hunan Province are all contact metasomatism deposits, and their ore-bearing layers are carbonate rock salts developed in karst. , the hydrogeological conditions are complex, and the ore-bearing layer of the Huayuan lead-zinc mine is also the limestone of the Qingxudong Formation of the Lower Cambrian System, and karsts such as underground rivers are extremely developed. When mining the above-mentioned mineral resources, due to poor engineering geological conditions, it is easy to cause mine geological disasters such as ground deformation in the goaf; complex hydrogeological conditions are prone to karst ground collapse and damage to the aquifer structure. This is why the ground deformation disasters in the goaf areas of Hunan Province are mainly related to the water-measured coal series coal mines, Longtan coal series (southern type) coal mines, and gypsum mines. The karst collapse and aquifer structure damage are mainly related to the Longtan coal series (northern type), Important factors related to non-ferrous metal mines such as Wujiaping Coal Series, Qianyang Coal Series Coal Mine, Shizhuyuan Polymetallic Mine, Huangshaping, Baoshan Lead-Zinc Mine, Qibaoshan Polymetallic Mine, etc.

The vast majority of open-pit mining mines in Hunan Province are sand and gravel clay mines, granite, limestone, quartzite and other quarries. The degree of weathering is high. When joints and fissures develop, mining will form a steeper open surface. When exposed to water, collapse is prone to occur; sand quarries, brick and tile factories, kaolin mines, laterite gold mines, and eluviated manganese ores are mined from Quaternary soil (sand) bodies. The mechanical strength of the soil body is low and it is easy to soften when exposed to water. Site slopes are prone to landslides; in addition, stone coal mines are mostly open-pit mined, and some sedimentary iron ores and phosphate mines also have open-pit mines. The ore-bearing layers are mainly the Jiangkou Formation and Doushantuo Formation from Sinian to Cambrian systems. , Xiaoyanxi Formation, the lithology is mostly slate, carbonaceous slate, and sandy slate. In addition to bedding, lamination and cleavage are relatively developed. Shallow weathering joints are very developed, and the stope slope is prone to Landslides and collapses.

At the same time, the amount of stripped waste rock and mining waste rock in the stope is large, which often becomes the material source of debris flow.

The waste residue and wastewater of non-ferrous metal and stone coal mines contain a large amount of heavy metal elements and radioactive elements, the waste residue and wastewater of chemical salt mines contain halogen elements, the waste residue of medium-high sulfur coal mines and pyrite mines, Wastewater contains a large amount of pyrite, which is a source of pollutants for water and soil pollution in mines.