Whether the choice of mining methods is reasonable is directly related to the safety, economic benefits and resource utilization of mine production [1-2]. The choice of mining methods needs to consider various factors such as safety, technical feasibility and investment cost [3-4]. At the same time, the physical and mechanical properties of the ore are also factors that must be considered, especially the mechanical properties of the ore [5- 7].
Mine for different technical conditions mining, mining methods mine may differ, such as Yu new multi-metal mine [8], cattle suffering lead zinc ore [9], Gushan iron ore [10] open pit mining method mined , while the embodiment of underground mining of copper ore mining Xintang [11] Lei Zhai copper ore [12], iron-copper tile plant [13] employed. The Jiudingshan copper- molybdenum ore body is small in scale, but it is clustered into ore-forming bodies. The mine used the underground caving method for mining. As a result, the economic benefits are poor, the resource utilization rate is low, and the safety hazards are large. At present, the mine needs to re-examine the mining method of the deposit and choose a reasonable mining method in order to solve various problems encountered in mine production, and at the same time provide reference for the selection of mining methods for other similar mines.
1 Mining technical conditions
1. 1 Mining status
The Jiudingshan copper-molybdenum mine was located in the northwestern part of Yunnan Province and was completed and put into operation in 2008. However, due to the low price of copper and molybdenum and unreasonable mining methods, the mining cost was high, which led to the temporary suspension of production in 2013. The original mining method of the mine is underground mining. The longwall caving mining method is used for top-down mining in the middle section (see Figure 1). The middle section of the mine has been in the middle of 2670, 2640, 2612, 2570, 2540, 2480m.
1. 2 ore body characteristics
The ore bodies in the mining area are mainly distributed in granite porphyry and contact metamorphic rock formations, and copper ore bodies and molybdenum ore bodies alternately appear to form ore bodies. The ore group is 80° east to the east, 10° east to east, 30° to the dip angle, and the strike length is about 700 m and the width is about 50 to 200 m. The ore bodies and rich ore bodies in the ore group appear cross-over, and the occurrence is basically the same. The overall scale is small, and most of them are lenticular along the layer, and there are compound and branching phenomena. The ore body thickness extreme value is 0. 83 ~ 43. 32 m, the average grade of copper ore body is 0. 29% ～ 0. 62%, the average grade of associated molybdenum is 0. 026% ～ 0.045%; the average grade of molybdenum ore body is 0. 15% ～ 0. 20%, the average grade of associated copper is 0. 036% ～ 0. 093%. The ore body characteristics are shown in Figure 2.
1. 3 Hydrology and engineering geological conditions
(1) Hydrogeological conditions: The aquifer in the mining area is mainly the granite porphyry weak fissure aquifer and the horn rock fissure aquifer in contact with the metamorphic belt. Due to kaolinization and chlorite, the granite porphyry becomes soft and hard and uneven rock, especially the weathering and fragmentation of the ore-bearing section is more significant, including weak diving; at the same time, the contact zone is developed, and most of them are tensile cracks and fissures. The rate is 1% to 4%, and the lithology is hard and broken, and the water is strong. Generally, the water level is 5 to 67 m below the surface and the aquifer thickness is 160 to 310 m, which has a certain impact on underground mining. If open mining is used, the impact is small.
(2) Engineering geological conditions: The ore-bearing geological rock group in the mining area is mainly composed of block rock type ~ hard engineering geological rock group and block rock type weak ~ hard engineering geological rock group, such as granite porphyry for medium to coarse grain flower The porphyry structure, block structure, and cracks in the rock body, the general fracture density is 22 / m, and the rock dry compressive strength is 8. 52 ~ 13. 32
MPa, wet compressive strength is 6. 88 ~ 9. 40 MPa; contact metamorphic horn rock, dense and hard, block structure, crack development, generally fracture density is 9 / m, rock dry compressive strength is 15. 60 to 22. 80 MPa,
The wet compressive strength is 10. 95 to 21. 20 MPa.
2 There is a problem with mining
The Jiudingshan copper-molybdenum mine was originally developed by underground mining. The mining method is the long-wall caving mining method. According to the years of production experience of the mine, the main problems encountered in the mining process can be summarized as follows:
(1) A number of ore bodies in the mining area form an ore body group, and the rich and poor ore bodies appear cross-over. When underground mining, the layout of the cutting and cutting roadway is difficult, and due to the poor engineering geological conditions of the mining area, the stability control of the surrounding rock is also a large problem.
(2) When mining is carried out by the caving method, although most of the goaf roof can achieve natural collapse, there is still a phenomenon that the roof of the local goaf cannot collapse naturally, which poses a serious safety hazard to the mining.
(3) Due to the low price of copper and molybdenum in recent years, and the high cost of underground mining, it has seriously affected the economic benefits of the mine and even incurred losses. In addition, local ore bodies have low grades and low reserves, which are treated as waste mines during mining, resulting in serious waste of resources.
3 Research on mining technology
3. 1 Mining method selection
Whether the choice of mining methods is reasonable, directly affects the economic benefits of mines and the utilization rate of resources. The mining method of Jiudingshan copper-molybdenum mine can be considered from the following aspects:
(1) Occurrence conditions of ore bodies: mines have shallower buried depths, and most of them are exposed on the surface;
(2) Ore body production and thickness: the ore body inclination angle is about 30°. Although most of the ore body thickness is small, the ore body quantity in the mining area is large, forming a certain scale of ore body group, and the thickness of the ore body group is relatively Large, thickest up to 200 m;
(3) Mining safety: The mine used underground mining. Because the stability of surrounding rock is difficult to control, accidents such as collapse of roadway often occur, and the safety of personnel and equipment is difficult to guarantee. This difficulty can be effectively solved during open-pit mining and greatly improved. Safety of mining;
(4) Economic benefits: The stability of the rock formation in the mining area is poor. When underground mining is adopted, the caving method or filling method must be adopted. The investment cost is high, and the mining cost and difficulty of the ore body are also large, resulting in poor economic benefits of the mine.
In summary, the Jiudingshan copper-molybdenum mine is more suitable for open-pit mining. Therefore, it is recommended that the mine change the original mining method and choose open-pit mining for mining.
3. 2 Determination of the slope parameters of the stope
There are many factors affecting the stability of open pit slopes. Therefore, when designing slope parameters, it is necessary to comprehensively consider various factors and combine the experience of other similar slope parameters. The physical and mechanical properties of the rock and the geological structure of the mining area directly affect the setting of the step height and the step slope angle. For example, the hardness of the rock, the internal friction angle, the fracture zone, faults and joints in the rock formation are all factors that must be considered. Factors such as the occurrence of groundwater in the mining area, the discharge conditions of surface water, and the time of storage of open slopes are also factors to be considered when selecting the parameters of the slope of the stope. In short, the determination of the slope parameters of the open pit of Jiudingshan Copper-Molybdenum Mine depends on the hydrogeological conditions, engineering geological conditions and physical and mechanical properties of the rock formation, and considers the existing equipment of the mine, and finally determines the side of the stope. The slope parameters are shown in Table 1.
3. 3 open-pit mining
The demarcation results of the open-pit mining boundary will directly affect the future economic benefits and resource utilization of the mine. The options for selecting the open-pit mining boundary must follow the following principles:
(1) The structural parameters delimited by the realm are conducive to the stability of the final slope;
(2) The boundary parameters of the boundary are compatible with the production scale, the physical and mechanical properties of the ore, and the technical performance of the mining equipment. Slope parameters and stripping ratio control are controlled within a reasonable safety range, and the open-pit mining boundary is expanded as much as possible to extract more ore and give full play to the superiority of open-pit mining;
(3) The timing of the open-air boundary shall not exceed the scope of the designated mining area;
(4) The boundary stripping, production stripping ratio, and average stripping ratio should be less than the economically reasonable stripping ratio. Based on the above principles, combined with the actual situation of the Jiudingshan copper-molybdenum mine, the realm of open-pit mining is defined. Since the mine stope is a hillside open-pit stop after the demarcation, the drainage and transportation system is better, considering various factors comprehensively, and finally delineating The top level of the stope is 2870 m, the bottom elevation is 2570 m, and the open pit end is the top of the boundary (length × width) 658. 64 m × 553. 86 m, the end of the open pit is the size of the bottom (length × width) 290. 12 m × 130. 49 m, the final slope angle is 42 ° ~
44°, the final step height is 20 m, and the current status of the mining site after mining is predicted.
3. 4 Mining technical and economic indicators
The Jiudingshan copper-molybdenum mine was completed and put into operation in 2008, and underground mining was carried out in 2013. Due to the low price of ore and high mining costs, the mine has been losing money. After the suspension of production and rectification in 2013, the mine changed the original mining method to open-pit mining. After the production summary in recent years, the current economic benefits of the mine have been improved, and the goal of turning losses into profit has been gradually realized. The main technical and economic indicators are compared in Table 2.
According to Table 2, the mining loss rate and the depletion rate in open-pit mining are lower than underground mining, and the resource utilization rate is higher than that of underground mining by more than ten percentage points. From the perspective of resource utilization, the open-pit mining method is more suitable for nine tops. Mountain copper molybdenum ore. From the analysis of mining costs, the sum of mining cost and stripping cost in open pit mining is much smaller than the mining cost in underground mining, which saves the mine's production investment. The transportation costs, electricity and water fees of the two mining methods are analyzed. Because of the large amount of waste rock to be transported during open pit mining, the transportation cost is much higher than that of underground mining, but the other aspects are less than underground mining. Considering the mining technical and economic indicators of the two mining methods, the overall economic index of the open-pit mining method is better than the underground mining method for the mining of the Jiudingshan copper-molybdenum ore mining area. Therefore, it can be concluded that the open-pit mining is more suitable for the nine-top mining. Mines with technical conditions for mining copper and molybdenum ore.
4 Conclusion
(1) The technical conditions of the mining of the Jiudingshan copper-molybdenum deposit are analyzed and analyzed. The conclusion is drawn that the ore body is small in scale, complex in production, clustered ore-forming groups, simple hydrogeological conditions in the mine, and poor stability of the ore.
(2) Summarize the problems encountered in mining, that is, the stability of roadway stability during underground mining is difficult; the roof of the goaf cannot be naturally collapsed, and the safety hazard is large; at the same time, the mining cost is high, resulting in poor economic benefits of the mine.
(3) According to the mining technical conditions and mining problems, it is proposed to use open-pit mining to carry out mining, determine the slope parameters and boundary range of open pits, and at the same time, through comparative analysis of technical and economic indicators, prove that open-pit mining is more suitable than underground mining. Mining of the Jiudingshan copper-molybdenum deposit.
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Article source: Mining Technology, 2017, 17(2)
Author: Huang Chun people; Chuxiong Mining Co., Ltd., Yunnan Chuxiong City 675 000
Wang Wen-li; China Nonferrous Metals Industry Survey and Design Institute Kunming, Yunnan Kunming 650051
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