The tailings reservoir closure scheme is mainly selected according to the following factors: shape and geomorphology, tailings type and mineral characteristics, local groundwater and hydrological conditions, tailings discharge method, drainage difficulty level, and water level. Each tailings pond site has its own specific conditions. In order to ensure that the closed and recovery project can meet the environmental constraints, it is necessary to select a suitable closed storage plan according to the specific site conditions to optimize the closed storage system. Otherwise, due to improper selection of the closed storage plan, long-term maintenance is required, and high maintenance fees will be passed on to future generations. To this end, the mining company must put in the appropriate recovery infrastructure capital during the operation period and begin to implement the closed storage program to safely close the warehouse without excessive cost and long-term maintenance. I. Non-sulfide tailings closed storage scheme The non-sulfide tailings closed storage scheme is shown in Figure 1. Figure 1. Non-sulfide tailings closure scheme If the tailings material is easily drained, such as potash, some uranium tailings, etc., diversion trenches and diversion banks can be used to stabilize the surface with geopolymers, and then use soil and plant cover, thereby completing the closed base; if the tailings material is difficult to drain, clays such as phosphate, hydroxide-containing tailings mud, in the case without a general drainage using guiding channel, and a downstream passive diversion dike Treated wetlands can improve leakage problems. Wetlands can provide growth conditions for plants. In some areas, vibration techniques can be used to drain or open ditches and drain methods so that vegetation can be placed on them. In order to reduce the discharge of acidic water to the environment containing sulfide tailings, there are various options, including compacted clay covering; synthetic membrane covering; inoculation of bacteria; surface filling with limestone ; diversion trench; filling of alkali, other chemicals or Biological ditch; discharged into the lake; chemical treatment; downstream wetlands; wetland cover; soil and plant cover; formation of hard shell; stable surface (geopolymer). II. Sulfide tailings closure scheme The sulphide tailings closure scheme can be considered in two cases, namely the low tailings area with high water level and the high tailing area with low water level. The former, if established wetland marshes, wetlands downstream throughout the tailings area will reduce the acidity of water leakage and to extract the metal to create the conditions, perhaps in some areas, especially in solid areas tailings area can be adapted to cover the geological polymer. The latter requires good diversion trenches and diversion banks to concentrate acidic and contaminant-laden water for treatment in downstream wetlands. The surface of the tailings in the high zone is suitable for stabilization with geopolymers, followed by soil and plant cover. Land surface and dense discharge are relatively new methods of tailings deposition. Since there is no drainage problem encountered in tailings pond discharge method, geologic polymer covering and stable tailings can be used to effectively close the reservoir immediately after closing. In fact, in order to establish a stable layer of sufficient thickness (forming a synthetic hard shell) before closing, it is possible to start geopolymer deposition in the later stages of the operation, either directly in the tailings of the plant or in the discharge pipe. Or add geopolymers to the tailings reservoir area. Sulfide tailings are piled up in pits (open pits or specially excavated deep pits) that can fill the tailings close to the top, or retain a certain height of super high, after drainage, covered with geopolymer. In most cases, wetland and geopolymer coverage, or a combination of both, may be considered. Three, small iron ore tailings reclamation scheme closed library (a) flood the tailings pond around the reclamation reclamation mode model has been applied with a large flood Malan Zhuang Iron ground. Rehabilitation project: 1 The river beach dam area is divided into square pools (2.67hm ² per pool) for sequential tailing and reclamation. 2 cofferdam, the height is 3m, the width of the dome is 1~1.5m, the slope is 1:1, and the bottom plane of the dam forms a slope of 3%~5% inclined to the overflow pipe. An overflow port is provided on one side of the raft, and the water overflow tank is discharged into the field or into the river. The overflow pipe is opened every 30~50cm to reduce the depth of overflow. The overflow pipe is provided with a row of tailings pipes every 20m, and a row of tailings is discharged. After being filled, it is dried for 20 days and then leveled. After the upper soil is more than 30cm, the crops can be planted, and then the tailings pipes are adjacent to each other. In another pool, the above operation is repeated, and the schematic diagram of the reclamation process is shown in Fig. 2. The process flow is shown in Figure 3. Fig. 2 Schematic diagram of reclamation process of Hetanwei pool tailings 1-pipeline foundation; 2-cofferdam; 3-slurry pipe; 4-valve; 5-branch pipe; 6-overflow pipe; 7-gate valve; A-dry section; B- Dam section; C-preparation section. Figure 3 Flow chart of tailings reclamation process (2) Tailings filling low-lying land or gully reclamation mode Zhaodianzi Iron Mine, Baoguanying Iron Mine, Qian'erzhuang Iron Mine, Zunhua City, Qianxi County Wangyeling Iron Mine has used this model to build a hundred acres of sandy pears, intercropping with dry crops and wheat, and the rice is also in pieces and grows well. This retanning mode is selected for use in gullies, valleys or low-lying areas near the plant. This tailings dam is short, with minimal engineering and low capital costs. Engineering requirements: Use waste rock to build dams in suitable valleys or gullies. The dam height is generally less than 4~5 meters. The rock dams have pores to see out the tailings water, or buried high overflow pipes in the dam. the water discharged from the backwater system for mineral recovery plant reuse. The filling sequence of the tailings is to fill the high ground of the valley first, and then fill the low places, which is convenient for district reclamation. After the tailings are full of dryness, the bulldozer is leveled, and the crops can be planted with the soil above 30cm in the upper part, as shown in Figure 4. Show. Fig.4 Schematic diagram of tailings filling low-lying land or gully technology (III) Staged-stage planting and planting reclamation technology The reclamation model has been segmented in the tailings section of the tailings reservoir in the Dashihe mining area of ​​Qian'an Shougang Mine Company Planting trees plays a role in fixing nitrogen, fixing the environment and reducing pollution. After planting, it also increases the organic matter content of tailings sand. This model is suitable for large tailings ponds with long service life. It is necessary to plant grassland in stages according to the progress of the dry slope section of the tailings pond. (4) Technical points for the reclamation of the tailings pond. The tailings are processed ore, which has formed a loose structure with a certain degree of humidity and pseudo-phase cementation, which generates a concentrated load field for the accumulation site. Because it is a loose structure, it will destroy the topography, pollute the environment, and also affect the environmental geology. The site selection of the tailings pond is generally selected in the ravine and valley, and it is far away from the plant in the downwind side of the residential area. The large and medium-sized tailings ponds generally have a volume of tens of millions of tons, and the service life is 10 to 20 years. Therefore, the stability protection of tailings dams is very important. Local small and medium iron ore mines do not pay attention to the reasonable discharge of tailings due to some mines, resulting in large area, silted rivers and polluted environment. However, experience has proved that the scale of the mine is small and the amount of tailings is small, so it is easy to organize the filling and reclamation, and it is easy to organize and implement in a flexible manner. In view of the above characteristics, in the decision-making of tailings reclamation, the subdivision is divided into the tailing process, and the reclamation process is carried out step by step. Combined with the characteristics of small and medium iron ore, the process of dispersing heat discharge and re-slapping is adopted. 1. Technical points for the reclamation of the tailings pond closed. According to local conditions, a variety of tailings reclamation technical solutions are summarized. For example, according to the topographical changes, there are reclamation techniques for dam construction in riverbanks, damming and reclamation techniques for filling gully sections, reclaiming of tailings, and reclamation of tailings, and it is necessary to adjust the process, and to simplify the process. Think about science. 2 In the practice of reclamation reclamation, attention should be paid to the design of the land reclamation plan in the mining area. The preliminary design includes establishing reclamation points, measuring geological topographic maps, doing engineering reclamation schemes, completing technical and economic analysis, screening agricultural and forestry crops, conducting pilot planting of agricultural and forestry crops, tracking and surveying crop growth, yield, fertilization statistics, and tracking soil ripening. Changes in the toxic and harmful elements of the situation, soil and crops, in order to take measures to accelerate the maturation of the soil, to control and reduce the pollution of toxic and harmful elements to the soil and crops, and to analyze the benefits of tailings reclamation (including economic, ecological and social benefits). 3 Develop technical standards for reclamation land that meet local specific conditions to serve as a guiding role. 2. Biological reclamation is a continuation of engineering reclamation and an integral part of the land reclamation process. Such as screening crop varieties, crop rotation, intercropping; various fertilization measures; monitoring soil and crop toxic and harmful elements, taking measures to reduce hazards; accelerating rejuvenation of soil fertility, slope vegetation cover, agriculture, forestry, deputy, fishing Such as the optimization of the retracement technology configuration. These measures play an important role in improving soil fertility and crop yield levels. According to the actual conditions of the mine, the research, experiment, summary and technical research work on biological reclamation from different aspects, the following technical points are proposed: 1 According to the climatic conditions in the northern mountainous areas of Tangshan, the chemical composition of the soil is Fe ₂ O ₃ , Al ₂ O ₃ , CaO, MgO, SiO _{2 ,} etc., and the SiO ₂ content accounts for 68.37%. The nutrient content in the soil is taken as the example of the Malanzhuang iron ore. The total phosphorus content of the guest soil is lower than that of the reclamation, and the available nitrogen The available potassium is higher; the organic matter content of the guest soil is higher than that of the reclaimed land, and the total number of bacteria in the soil is not much different. This indicates that the level of fertility in reclaimed land is low. Therefore, the soil in the reclaimed land should be focused on fertilization, and the cultivation of crops should be carried out by adding organic fertilizer and planting crops. 2 Through the analysis and analysis of the basic physical properties of tailings, waste rock, topsoil and guest soil, the tailings sand is fine sand, the waste rock topsoil and tailings are gravel coarse sand, and the waste rock is gravel soil. The soil has strong sand, low fertility, poor water retention and poor fertilizer retention, but they have good gas permeability and permeability. Practice has proved that when the tailings are reclaimed, they are mixed with soil with high content of powder and clay (such as mountain soil), and organic fertilizer is applied. The reclaimed soil can adapt to crop growth. â‘¢ After the test of the new soil and soil tailing, respectively, both bulk density ^{1.14 g / cm 3, 1.30g /} cm 3, a specific gravity of ^{2.64t / m 3, 2.79 t /} m 3, a porosity of 53.4%, 58.3% The bulk density is small, the porosity is large, and the soil in the soil is relatively sticky, easy to form, and poor in permeability. Zunhua Xingwangzhai Town uses tailings to improve the slab soil, which is to use the tail sand pad pig stalk fertilizer, and then apply the viscous The soil increases crop yield by 10%. 4 According to the results of follow-up survey, it is necessary to carry out agroforestry in time after reclamation, because with the extension of agricultural and forestry planting time, the content of organic matter, alkali nitrogen, available phosphorus and available potassium in reclaimed soil increased year by year, the content of clay and powder Increase, the sand content is reduced. 5 Ways to improve the soil fertility of sandy reclaiming are: ̇ sand soil mixed with clay to improve the soil; ̇ increase the application of organic fertilizer, straw return to the field; ̇ establish a reasonable rotation system. Legume crops and other crop rotations, play a role in legume crops to increase phosphorus and nitrogen; leguminous green manure has strong nitrogen fixation capacity, can also maintain soil organic matter balance and stability, can improve soil structure and reduce soil erosion. 6 Selection of crops and fruit varieties a. According to the results of soil tests, the reclaimed soil is a strong sand and low fertility level. Therefore, in the pilot site, it is necessary to select crop varieties that are resistant to inferiority, such as beans, millet, potato, and corn. After retanning, the bean crop should be given priority, which is beneficial to accelerate the ripening of the soil. In addition, the practice also proves that under the condition of the water-maintenance layer on the bottom of the soil, sufficient water and fertilizer can ensure the growth of rice. b. According to the test, the pH value of the complex soil is between 6.8 and 8.1, which is slightly acidic to neutral, suitable for planting chestnut and apple. Potassium, iron and potassium in the topsoil greatly promote the conversion, transportation and accumulation of sugar, and iron can increase the sugar content in the fruit. Qianxi, Qian'an and Zunhua are rich in sweet and delicious chestnuts. c. According to the characteristics of strong and easy soil loss of reclaimed soil, planting trees and pastures should be selected. This will not only fertilize the soil, improve soil moisture, accelerate soil ripening, but also prevent wind and sand, reduce soil erosion and prevent environmental pollution. Practice has proved that the temperature of the summer forest is 3.6~4.3°C lower than that of the farmland, the relative humidity is increased by 14%~17%, the soil water content is increased by 3.8%~4.7%, and the evaporation is reduced by 7.5%. The Malanzhuang Iron Mine reclaimed the land of the river, the willow forest was formed into a net, and some dumping sites were replanted between chestnut trees or pear trees and crops. The large-scale planting of seabuckthorn and amorpha in the Shougang tailings pond has become a forest, which plays a role in wind-proof and sand-fixing and ripening soil. d. Select suitable crop and fruit and fruit varieties based on the bulk density and porosity of the reclaimed soil. The biological characteristics of various crops are different, and the penetration ability of roots is different. When the porosity is less than 50%, the soil bulk density suitable for wheat growth is 1.41~1.26g/cm ³ , and the porosity is less than 52%~6% when the porosity is When the degree is less than 50%, the wheat yield is significantly reduced. The root penetration ability of cucumber is weak. When the soil bulk density is 1.45 g/cm ³ and the porosity is 45.5%, it is difficult to penetrate. According to the practice test, the reclaimed soil similar to the Malanzhuang Iron Mine in Qian'an and the Hanerzhuang Iron Mine in Qianxi is suitable for growing wheat and cucumber. The iron ore reclaimed soil in the northern part of Tangshan is strong in sand, loose, small in bulk density and large in porosity. It is especially suitable for the growth of tuber and tuber crops, such as sweet potato and potato. Chestnut tree has strong tolerance to solid soil, so it can grow normally under slope soil conditions with soil bulk density of 1.55~1.65g/cm ³ ; while apple and pear trees are suitable for loose soil, so it is in tailings. The reclaimed land and the reclaimed land of the dumping site are growing well. 7 For the effect of reclamation on the growth of crops and the quality of raw grain, the toxic and harmful elements and radioactivity in tailings sand, reclaimed soil and raw grain were tested respectively to provide a basis for the feasibility of reclamation. The test proves that the toxic and harmful elements in the tailings and complex soil of Tangshan Iron Mine have not exceeded the growth resistance of crops. Some harmful elements are higher than the soil of the soil, but they are not exceeded and will not cause pollution. 8 Prevention and control measures for pollution of toxic and harmful elements in reclaimed land: a. Application of inhibitor: application of lime in reclaimed land can increase the pH value of the soil, and the application of alkaline phosphate can reduce the solubility of elements such as cadmium and mercury , thereby reducing its Effectiveness. b. Add organic fertilizer and improve sandy soil c. Strengthen water and fertilizer management. Under flooding conditions, rice can significantly inhibit the absorption of cadmium, but increase the absorption of arsenic ; under drought conditions, arsenic is not easily absorbed by crops. Strictly control the variety of fertilizers containing toxic substances. d. Control and eliminate industrial “three wastes” emissions and control the use of chemical pesticides. 9 Tests showed that the content of various toxic components of tailings water and agricultural water in the reclamation site of Tangshan Mine did not exceed the water quality standards for agricultural water. This indicates that tailings water discharge did not cause an impact on the agricultural environment. 10 Tangshan iron ore was detected in the reclaimed land and the soil of the guest soil, the radioactivity was lower than the national standards, indicating that the tailings reclamation did not cause radioactive pollution to the local soil, nor did it cause radioactive contamination of the original grain. Explain the feasibility of reclamation of Anshan-type iron ore tailings.

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