Discussion on prevention of mining face collapse i

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Discussion on the prevention of coal mining face collapse

land and coal are equally important limited resources in the development of industry and agriculture, and they are important factors that restrict China's economic development for a long time, but coal mining face will lead to ground collapse and form goaf. The mechanism of Goaf Collapse is relatively complex. This paper discusses the mechanism and development factors of Goaf Collapse

1 mechanism of coal mining face collapse and its impact on the environment widely used in metallurgy, building materials, colleges and universities, scientific research and other fields

1.1 mechanism of coal mining face collapse when the coal mining face is mined out, the overburden on the upper part of the goaf and the coal pillar border formed by the goaf form a free surface. The original stress balance is destroyed. Under the gravity of the overlying rock and soil layer, the pressure borne by the overlying rock increases with the expansion of the goaf. When this pressure exceeds the bearing capacity of the coal seam roof rock, the roof rock will break and collapse to form a caving zone. The caving rock blocks are of different sizes and are filled into the goaf in a disordered manner. The falling rock block protrudes into contact with the upper rock stratum, but the supporting force is not enough to hold the upper rock stratum, so the upper rock stratum sinks, bends downward, and breaks, producing cracks, that is, forming a fracture zone. The rock layer on the upper part of the rock layer in the fracture zone is called the bending zone because the rock layer in the fracture zone bends downward and bends downward as a whole under the weight of its own gravity and the overlying rock layer, but it neither breaks nor falls off. Under the influence of the bending zone, the ground collapses, forming collapse basins and collapse pits

1.2 impact of coal mining face collapse on the environment ① mechanized coal mining caused a large area of surface collapse, which destroyed land resources and worsened the ecological environment in the collapse area. ② The area of cultivated land has decreased year by year, and the contradiction between people and land has intensified. Coal mining has caused surface subsidence and collapse, resulting in partial or complete destruction of farmland and water conservancy facilities, blocked rivers, serious flood disasters in flood season, reduced crop production, and even no harvest. Many good fields on the ground have become potholes with perennial ponding. Coupled with population growth, land occupation for engineering construction and other reasons, the production and living difficulties of farmers who lost farmland in the subsidence area have been aggravated. ③ At this time, the impact on human settlements must be repaired in time. Affected by the coal mining collapse, the people's houses in the collapse area are cracked and skewed, resulting in a large area of dangerous houses, and the personal safety of residents is seriously threatened. ④ Restrict the development and construction of urban and rural towns in the region, and increase the investment of funds, manpower and materials from both geological and mining sides. Many roads have been damaged due to surface subsidence and collapse caused by coal mining. Urban construction has to increase the construction cost because of solving the problem of project stability, and the human and material resources of project stability have increased, which has increased the local financial burden; At the same time, due to the road damage caused by coal mining collapse, coal mining enterprises need to invest a lot of money every year. In response to the above problems, the local government and the mining side have worked together to make a comprehensive and comprehensive plan, and made some useful attempts in restoring the ecological environment, increasing the area of effective cultivated land, improving agricultural facilities and conditions, and improving the production and life of the people in the mining area

2 measures to prevent the collapse of coal mining face

2.1 establishing a special Prevention Fund for the collapse control of coal mining face is a costly project. While actively striving for the coal sustainable development fund, local financial resources, urban construction funds and policy income are still the main channels of investment. We should open up channels and raise funds from multiple sources to focus on the treatment of coal mining subsidence. First, we should actively strive for financial support from the state, provincial and municipal governments, actively strive for, make overall arrangement, centralized allocation and rational use according to the three investment directions of the national coal sustainable development fund, give investment support by means of investment subsidies, sub loans, loan interest discounts, and focus on the management of coal mining subsidence in local coal mines; Second, land reclamation fees should be charged. According to the principle of "who destroys, who governs", the management of goaf shall be included in the coal production cost, a certain proportion of land reclamation fees shall be charged to the coal enterprises that cause collapse hazards, and the cultivated land reclamation fees, cultivated land occupation fees, and paid use fees for newly added construction land shall be bundled for use. Third, we should activate private funds. According to the principle of "who governs, who benefits", give full play to social forces, widely absorb social idle funds, adopt contracting system, auction, lease and other forms, implement paid use of land and paid governance, and invest in the governance and construction of coal mining subsidence land

2.2 improving prevention technology to ensure the treatment of coal mining face is a complex ecological and social project, which involves not only underground geological changes, but also aboveground fields, forests, roads, water, gas and other factors. Therefore, we must improve the content of science and technology and rely on advanced science and technology for scientific management. First, scientific planning should be carried out, which not only deals with the relationship between short-term planning and long-term planning, local governance and overall layout, but also considers the actual needs of natural resources and social development in the subsidence area. Second, we should adjust measures to local conditions. Different treatment methods are adopted for different types of subsidence land, such as agriculture, forestry, fishing and construction. The land can be leveled and the farming conditions can be improved where the collapse is not deep or there is not much ponding. Restore the landform; In the subsidence area with large area and deep water, aquaculture, tourism and leisure industries can be developed. Through treatment, waste land is turned into treasure land, and the effect of comprehensive treatment is achieved. Third, we should adhere to the principle of putting prevention first and addressing both the symptoms and root causes. We should adopt advanced detection methods, strengthen the monitoring of the goaf, take effective measures to fill the goaf, and minimize the collapse area of the goaf, so as to achieve the purpose of treating both the symptoms and the root causes

2.3 eliminate the influence of mining boundary. The most serious place where underground mining affects the ground is the edge of the surface subsidence basin, which is located above both sides of the mining boundary. Therefore, when arranging the mining face under the building, the vertical working face should have enough length to make the surface fully mined, so that the building is located at the flat bottom of the mobile basin. In addition, when the mining face passes through the lower part of the building, the mining speed should be accelerated as much as possible, and mining cannot be stopped, especially residual pillars should not be left. The law of surface movement shows that the permanent uneven subsidence and deformation of the surface are concentrated in the edge of the surface subsidence basin. Every time a permanent mining boundary appears underground, an area with large deformation value appears on the surface. The new copper alloy material developed by Guoliang copper has reached the level of silver in terms of thermal conductivity. In order to minimize the harmful impact of mining on the protected buildings, it is required to realize full pillar mining: that is, a large area of comprehensive mining is carried out within the whole coal seam range of the mine field, so as to avoid the formation of permanent mining boundaries within the coal seam range and the accumulation of deformation values of each coal seam, so as to minimize the harmful impact on the protected buildings. Therefore, long face mining and layer by layer mining must be realized

2.4 strengthening ecological restoration mainly refers to the technical treatment of polluted areas, which is also an important prerequisite for ecological restoration in mining subsidence areas. The mine development mainly causes pollution to the air and water in the mining area, as well as serious pollution to the land (bolt) metal rod body and its accessories. The performance standard mt146 ⑵ 011 is heavily damaged. Therefore, the restoration and treatment of atmosphere, water and land is the main task of ecological environment restoration (treatment) in the mining area. As for the traditional technical measures in this regard, the relevant research at home and abroad has been very rich. Here we will focus on the emerging phytoremediation technology, which is by far the most economical, ecological and highly efficient ecological remediation technology. The so-called phytoremediation technology is a new pollution treatment technology that uses the absorption, volatilization, transformation and degradation mechanism of green plants and rhizosphere microbial system to remove pollutants in the environment. According to the repair function and repair characteristics of a certain aspect of repair plants, the types of plant repair technology can be summarized as plant absorption repair method; Phytoremediation by volatilization; Plant stabilization repair method; Plant degradation remediation and Rhizosphere biodegradation remediation

2.5 actively use the filling grouting construction process. The goaf filling grouting technology uses the grouting pump as the power source to inject the slurry with filling cementation into the goaf through the grouting pipeline and grout stopping system, so as to fill the goaf and control the movement of overlying strata and surface deformation. Filling grouting in goaf can be divided into full filling grouting and semi filling grouting according to applicable conditions. Full filling grouting is to use suitable and low-cost grouting materials to fully fill the treated goaf and the cracks of the overlying strata when the stability of the overlying strata is high or the strength of the strata itself is low; Semi filling grouting is to carry out local effective filling within the determined goaf, and achieve the purpose of controlling the movement of overlying strata and surface deformation at the same time

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