The prevention and control technology of subsidence damage can be considered from two aspects; (1) the control of mining subsidence, that is, through reasonable selection of mining methods and techniques, rational arrangement of mining face, adoption of underground filling method, and filling of overburden strata with space To reduce the surface subsidence, control the speed and extent of surface subsidence, and achieve the purpose of protecting the surface and ground construction, structures and cultivated land. (2) Restoration and remediation of mining subsidence damage, using land reclamation technology and building anti-seismic deformation technology to remediate and utilize the land damaged by mining subsidence. 1.1.1 Full filling mining Prior to the recovery of coal caving roof yet, for the solid material goaf dense filling, so that the top layer generates only a small amount slate sink to reduce subsidence and deformation of the surface of the ground to protect the building, structure or The purpose of the farmland. Among them, water and sand filling is a good method to reduce surface subsidence effect in filling coal mining method, followed by wind filling and vermiculite self-slip filling. However, filling mining methods require specialized filling equipment and facilities, as well as adequate filling materials. The initial investment in the mine was large, and the cost per ton of coal increased accordingly. 1.1.2 strip mining According to the combination of coal seam and overburden, one piece is taken in the coal seam to be mined according to a certain ratio of retention, and one is retained. Since strip mining only partially extracts underground coal resources, a portion of the coal is retained in a coal column to support the overlying rock formation. Thereby reducing the movement of overburden, controlling the movement and deformation of the surface, and realizing the protection of the ground construction and structures. However, the method has low recovery rate, many roadway excavation, and low working surface efficiency. 1.1.3 Overburden Separation Filling According to the rock movement characteristics of the three belts formed by the overburden movement above the goaf, in a certain time interval after the coal is mined, the borehole is moved to the separation zone with high pressure grouting, filling and reinforcing the space of the separation zone, which will be driven. The masonry beam structure is reinforced into a continuous beam structure with good stability, so that the sinking space of the separation zone is no longer transmitted to the surface to reduce or slow down the surface subsidence and protect the ground construction, structure or farmland. But the technology is very difficult, and further research. 1.1.4 limited thickness mining According to the topography, hydrogeological conditions of the mining area and the anti-deformation ability of the building and structure, the thickness of the exploitable coal seam is determined based on the non-surface water accumulation and the required protection level of the building. The mining is to recover only the thickness of the coal. The remaining coal seams are not mined to achieve the purpose of reducing subsidence to protect ground structures, structures and land. However, the technology has a low recovery rate and has a certain use value only in thin coal seams. 1.1.5 coordinated mining When stratified mining of thick coal seams, rationally design the mining spacing, mutual position and mining sequence of each working face, so that the surface deformation caused by mining one coal seam (working surface) and the surface deformation caused by mining another coal seam (working surface) Offset or offset part of it to reduce surface deformation caused by mining and protect ground structures and structures. However, the technology must maintain a certain distance, so it is difficult to organize production. China has not carried out such industrial experiments. 1.1.6 "Picking - Injection - Mining" three-step mining Make full use of the control effect of overlying strata structure on rock movement, apply the principle of load displacement, carry out small-strip mining-grouting and filling consolidation goaf-three-step mining of residual strip mining, effective on rock movement and surface The control of subsidence solves the control of surface subsidence in large-scale mining, improves the recovery rate of coal, and protects the ground construction and structures, but it also has the disadvantages of complicated process and high cost. 2. Land reclamation technology 2.2.1 Coal gangue filling and reclamation and fly ash filling and reclamation (1) A large amount of coal gangue produced by underground mining is transported to the surface, which not only occupies a polluted environment. The use of coal gangue as a filling material can restore the land destroyed by coal mining and reduce the amount of land occupied by meteorites. (2) Using the waste from the power plant - fly ash to fill the subsidence area to reclaim land, can make two pests (subsidence area, fly ash) for Sanli (power plant, coal mine, farmers are good for three faces). 2.2.2 Flat land and construction of terraced reclamation For the slope area where the water subsidence area and the phreatic level are low, the method of leveling the land and transforming it into terraces can be used for reclamation. The horizontal width of the terraces and the height of the ladder should be determined according to the gradient of the slope of the ground, the thickness of the soil, the amount of the project, the type of crops, and the mechanization of the cultivation. The size and slope direction of the slope should be based on the original slope. It is determined without irrigation conditions or by reclamation of land use. 2.2.3 Reclamation method The drainage channel is excavated, and the shallow water in the subsidence area is introduced into rivers, lakes, pit ponds, reservoirs, etc., as water storage, and it is re-cultivated by subsided flooded land. 2.2.4 shallow dug mat shallow reclamation Use artificial or mechanical methods to dig deep areas of localized water or seasonal water subsidence areas, suitable for fish farming, water storage irrigation, etc., and use the excavated soil to fill the mining area with less subsidence, making it a Cultivated land. 2.2.5 Comprehensive utilization technology of water accumulation area For the subsidence area with large surface water accumulation and large depth of water, scientific and comprehensive utilization, development of cage fish culture, fence fish farming, flood storage for irrigation water sources, construction of water parks, etc. 2.2.6 Solid microbial reclamation technology The coal gangue is added with an appropriate amount of microbial activator, and after a plant growth period (about 6 months), a stable plant growth layer can be established to form a mature soil. Conclusion Mining subsidence is the direct cause of environmental geological disasters in mining areas. Effective control and reduction of ground subsidence is the basic way to avoid mining environmental disasters. Filling coal mining method is a good method to reduce the effect of surface subsidence. In recent years, some mining areas in Shandong are doing paste filling experiments. This method can make the stope have no or reduce the fall zone, and can better reduce the surface subsidence. . However, its technical content is very large, the transmission line is large, and the pipeline is easy to block. If it succeeds, it will be a technological revolution in coal mining. The impact and destruction of mining subsidence on land resources is inevitable. Therefore, each coal mine should apply multi-disciplinary knowledge such as prevention and control of mining subsidence technology and land reclamation technology, and ecological reclamation technology in mining areas according to its actual conditions and conditions. In order to better protect the surface, mining environment and farmers' interests by comprehensively managing and exploiting surface subsidence. The stone mill flour preserves the original flavor of the wheat. All kinds of pasta made with the milling flour mill are flexible, rich in wheat fragrance and higher in nutritional value. It is a healthy and healthy food of natural green. From wheat input to flour milling machinery to flour production, the flour processing industry's production process can be roughly divided into four steps:
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The first step is to clean up the impurities. Wheat into the high efficiency combination grain screen, using a plane rotary screen to remove the soil in wheat, the use of magnetic separator to remove metal impurities, the use of gravity classifier to remove stone and inferior wheat.
Second step cleaning and drying. The wheat is added into the wheat washing machine, and water is injected and dried to further clean the impurities.
The third step is to moisten the wheat. The wheat will be washed again into the wheat machine warehouse, moistening for about 10 hours (wetting 1%).
Fourth steps to make powder. The cleaned wheat was put into the grinding machine, and after repeated grinding, the wheat bran and flour were separated.
Coal mining subsidence prevention and control technology
I. Techniques for prevention and control of subsidence