## 4 The Process of Changing Mining Methods in Mines
### Comparison of Economic Benefits  
After the conversion of the mining method, data on the operational cycle and production capacity of the stope were obtained through statistical analysis. Specifically, the rock drilling efficiency is 4000 m per month for vertical deep holes, the discharge efficiency is 600 tons per shift, and the filling capacity is 1000 m\({}^{3}\) per day. Considering the imbalance factor, it is estimated that the mining cycle time of the stope is 1486 shifts, which covers rock drilling, blasting, and ventilation, a small amount of ore output from the riffle, a small amount of ore output from deep holes, a large amount of ore output, and filling. Table 5 represents specific technical and economic indicators. In addition, after adopting the sublevel open stope subsequent filling method, the recovery rate reaches 85%, the dilution rate is 7.38%, and the iron grade of the ore is 31.52%. To further improve the recovery rate and reduce the dilution rate, measures can be taken to improve the quality of filling, timely filling to maintain stability, remove the rock layer, optimize the mining process, etc. For the mines adopting the sublevel caring method, the recovery rate is generally lower than 90% and the dilution rate is generally greater than 20%, as shown in Table 6, which is the statistics of the recovery and dilution rates of the domestic part of the mines adopting the sublevel caving method. Figure 11: Rock drilling and blasting arrangement. Compared with the backfilling method, the main economic indicators of the sublevel caving method are as follows: 81% recovery rate and 31.33% iron grade. With the increase in recovery rate, its service life is also increased--the sublevel caving method can extract 27,668,36 million tons of ore and the backfilling method can extract 29,034.7 million tons of ore, and the difference between the two is 1366.34 million tons. According to the annual output of 3 million tons/year, it can extend the service life of the mine by 4.55 years. In addition, the grade of the output of the ore is increased by 0.19%. In other words, it will increase pure iron by 0.57 million tons per year, which can increase the economic benefit of the mine by 12.24485 million RMB per year (according to the current national average price of iron ore concentrate with a grade of 65%: 1396 RMB/t). In addition, the sublevel caving method requires a total of 6160 acres of land to be appropriated to set up the caving area, waste rock stope, and tailings storage, and according to the \"Anhui Province Comprehensive Land Price Standard for Exporportiated Areas\" issued in 2020, the compensation for each acre of land exportiated in Lujiang County is 43,070 RMB, and the mine will need to pay about 265,311,200 RMB for compensation for land expropriation only, while for the backfilling method, filling up the air-mined area to control the subsidence of the surface can be reduced or not required. Land acquisition can be reduced or not required. At the same time, compared with the sublevel caving method, according to the original preliminary design, in terms of ore production costs, if factors such as auxiliary materials and development are considered, the cost of using the sublevel caving method is 60.74 RMB/ton, while the cost of the backfilling method is 114.59 RMB/ton (including filling costs of 23.88 RMB/ton). In addition, if the sublevel caving method is selected, the construction cost of tailings ponds, tailings transportation, and discharge costs will further increase its total costs. In addition, after adopting the backfilling method, due to the improvement of ore grade at extraction, the benefits of subsequent beneficiation, tailings