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Safe and efficient mining of broken ore bodies has always been a major technical problem in mining technology research [1]. Qianhe gold deposit, as a representative weak fracture type deposit in China, has formed more mature after more than 20 years of mining. Downward layered cement filling mining technology, in recent years has successfully transformed the artificial concrete filling system into a river sand cementing filling pipeline conveying system [2-4]. However, with the increase of mining depth, the key areas of mining have gradually changed from the northern ore belt to the southern ore belt. In terms of mining area and deposit geology and mining technical conditions, there have been major changes compared with the previous ones, and the mining environment has become increasingly Deterioration, the existing downward stratified cementation filling mining process has certain safety hazards in the actual production process. The stratification is prone to collapse in the side wall during the mining process, and the actual wood support operation is difficult, and the personnel work Poor environmental and ventilation conditions, and low efficiency of artificial mining. In order to continue mining the mine, it is necessary to optimize the mining methods and processes of the mine.
1 Mining status and mining technical conditions
The Qianhe gold mine in the Qianhe gold mine is jointly developed with “Pingyu + Shaft + Blind Inclined Wellâ€. The height of the middle section is 40m. Currently, there are 200, 160, 120, 80m in the middle of the main mining area, and there are about 33 mines, accounting for the entire mine. More than 50% of the amount. The existing production scale of the mining area is 600t/d. The mining method is mainly to the stratified cement filling mining method. The single stope production capacity is 40t/d, the ore loss rate is about 6%, and the depletion rate is about 9%.
The Weigou mining area contains IVN2, IVN2-1, IV3, IVS3 ore bodies, of which IVS3 is distributed in the 76-84 line. The ore body is irregularly veined and lenticularly produced in the upper middle part of the IVS ore belt. The ore body is 200-350 m long. Going 70°～100°, tending to North West-Northeast, inclination 45°～80°, average 68°, obvious characteristics of expansion and branching along the strike and slope; ore body thickness 0.74～6.39m, average 3 .08m, is a typical steeply inclined thin vein. As of the end of December 2015, the IVS3 ore body 122b+333 has a reserve of 706,000 tons, with an average grade of 2.91 g/t, accounting for 52.3% of the total area of ​​the Weigou mining area. The surrounding rock of the ore body is carbonated fractured rock. After the project is exposed, it is easily collapsed. The lower plate is fragmented Anyan-altered andesite , which is unstable to medium stability. The current development project is arranged in the lower plate. The lithology of the deposit is complex, the geological structure is developed, the weathering of the rock is moderate, there is a weak interlayer and the rock is broken. The complexity of geological exploration of ore deposits is divided into moderately complex types of massive rocks. The Yihe River passes through the western end of the Genggou section, which is a natural boundary. The main ore body is located below the erosion datum, forming a water-bearing rock group with a mining belt and a top floor. The fracture is poorly guided, and the hydrogeological conditions of the fissure-filled water are medium. Mineral deposit. The mining technology of mining bodies is poor and the mining is extremely difficult.
2 Optional mining method and its comparative analysis
2.1 Optional mining method and process
According to the analysis of mining status and mining technical conditions, the mining methods that are technically suitable for the mine include the stratified caving mining method, the upward approach filling mining method and the downward horizontal stratified filling mining method.
(1) Option I: Stratified caving mining method. The planned stope is arranged along the ore body. The height of the middle section is 40m, the length of the stope is 60m, the width of the stope is the thickness of the ore body, and the stope is 6~7m. The pillar does not leave the top column and the column. Firstly, a double-grid patio is arranged at both ends and the center of the stope, and then the middle section of the stopway is connected to the central courtyard of the stopway. At the middle level of the stope, the top roof is pulled from the central patio of the stope to the two sides of the pit, and then expanded to the boundary of the ore body or cut once along the full thickness of the ore body. The height of the cutting top is 2.0 to 2.5 m. From the top of the cut, the stope is stratified from the top to the bottom, and the stratified caving is carried out. The shallow-eye mine is used, and the mining is started from the central patio of the stope. After the stratification is completed, the false bottom is produced. It can be retracted from the two ends of the stopway to the central patio. The cutting and cutting project in this scheme is supported by wooden scaffolding and is generally not supported. The standard scheme of the mining law is shown in Figure 1.
(2) Option II: Upward approach to fill mining method. The planned stope is arranged along the strike, the height of the middle section is 40m, the length of the mine is 58m, the width of the stop is the thickness of the ore body, the 2m column and the 6m bottom column are left in the stope, and the top column is not left, and the layer height is 2m. Firstly, the tunnel is transported from the middle section to the upper part of the ore body, and then a 2m×2m central ventilated pedestrian well is constructed near the upper part of the mining site, and timber is used for support and erection of ladders and filling pipes. Then, using the ventilating pedestrian well to carry out brush expansion, forming a 2m × 1m Shunlu Mine Pedestrian Well, and divide it into two compartments, one for the mine, and one for the ladder pedestrians. After the construction of the cutting and cutting project is completed, the bottom-up approach can be taken from the bottom of the bottom column, with the central patio as the free surface, and the middle end to the end, and the electric picking is used. After the mining is completed, the top of the ore body can be placed in time. The surrounding rock is supported by FRP anchor + high-strength polyester fiber mesh. After the end of one layer of the end of mining, the filling pipe is placed on the top plate of the road, and the filling wall is filled for filling operation, and then the other end of the same layer can be recovered, and the second layer and the subsequent layers are followed. This sequence is sequentially picked up until the end of the stop. The standard scheme of the mining law is shown in Figure 2.
(3) Scheme III: Downward horizontal stratification filling mining method. The planned stope is arranged along the strike. The middle section is 40m high and the stope is 60m long. The stope width is the thickness of the ore body, and the stratification height is 2.3~2.5m. There is no top and bottom columns. The middle section of the transportation lane is arranged in the outer rock mass of the lower part of the ore body. Firstly, the middle section of the transportation lane is transported to the ore body to the upper part of the ore body, and the central double grid well is built up near the upper part of the ore body. Mine, a pedestrian, and the use of timber intensive support, while filling the pipeline with filling pipes, pedestrian ladders, for pedestrians, ventilation, mining and filling. After the completion of the mining project, the approach is adopted from the top-down stratified mining, and the central double-grid well is propelled to the two wings. The manual + electric winch winch is used for joint mining. After each layer is mined, the filling can be filled and filled. Before the field should be leveled, filmed, laid steel and erected to fill the retaining wall. Workers work under cemented backing, which is safer and more reliable. The first mining layer is made of high-strength polyester fiber mesh + hollow grouting anchor cable combined support, and other layered mining roads and filling contact roads are supported by wooden sheds. The standard scheme of the mining law is shown in Figure 3.
2.2 Scheme comparison
Based on the above-mentioned optional mining method scheme and process, the main advantages and disadvantages of each scheme are summarized and analyzed in terms of safety conditions, production capacity, mining cost, lean index and process complexity. The results are shown in Table 1. According to the standard scheme and the current unit price of the mine, such as labor, materials, etc., the design values ​​of the main technical and economic indicators of each scheme are shown in Table 2.
Based on the advantages and disadvantages of the above schemes and technical and economic indicators, the corresponding hierarchical analysis model is first established, the weight value of each factor is determined, and the qualitative indicators are dimensionlessly processed, and then the corresponding fuzzy comprehensive evaluation matrix R can be determined. Finally, the weighted average model is used to evaluate each scheme [5-7]. According to the evaluation results, the membership degree of the three schemes for the optimal mining method scheme is 0.554, 0.253 and 0.611, respectively. It can be seen that the scheme III is the best for the stratified filling mining method, and the scheme I is the second to the stratified caving mining method.
3 Risk assessment analysis of selected mining schemes According to the preferred results of the scheme, the downward stratified filling mining method is still the most suitable mining scheme in the Qianhe gold mine in the Qianhe gold mine, but this scheme is compared with the existing mine scheme. Optimization of mining technology, mining and support methods, in order to more comprehensively understand and evaluate the optimized mining plan, based on the unit price calculation of personnel, materials, engineering contracting, etc., break-even analysis and sensitivity analysis of the plan To conduct an overall risk assessment of the optimized solution.
3.1 breakeven analysis
The project risk is analyzed based on the breakeven point (BEP) calculated from fixed cost, unit ore value, variable cost, sales tax and surcharges. The calculation results are as follows:
Breakeven scale = fixed cost expense unit ore creation value - unit ore variable cost - unit ore business tax and additional = 154.922.98 × 0.83 × 230-245.33-8 × 100% = 46.8 When the production capacity reaches 49.10% of the designed production capacity, that is, the annual output of ore is 64,800 tons, the project can reach breakeven. When the grade of the ore is 70.35%, that is, the grade of the ore is 2.10g/t, the project can reach breakeven.
3.2 Sensitivity analysis
After the proposed scheme is applied to the horizontal stratified filling mining method, the key factors that directly affect the economic benefits of the mine after commissioning are: metal price, annual ore volume, depletion rate and loss rate control. Therefore, it is necessary to carry out sensitivity analysis and prediction on the impact of these four factors on the economic benefits of mines within a certain range. The results of its annual profit analysis are shown in Figure 4.
It can be seen from Figure 4 that the change of metal price factor has the most obvious impact on the economic benefit of the mine. The impact of mine production capacity and grade control on the economic benefit of the mine is also obvious, and the impact of the change of the loss rate is relatively small, so the production is improved. The ability to control the quality of the ore is the key to improving the economic benefits of the mine. In general, the ability to resist risks is strong.
4 Conclusion
Based on the analysis of mining status and mining technical conditions, combined with the characteristics of this type of mining, three kinds of targeted mining methods are proposed. Through the comparison of the process and indicators of each program, the results show that the downward level is divided. The layer filling mining method is still the most suitable mining method for mining steeply weak and weak thin veins in the Qianggou mining area of ​​Qianhe Gold Mine. In order to adapt to the deteriorating mining environment of the mine and effectively solve the problems of poor safety conditions, difficult support and low mining efficiency, it is necessary to optimize the existing mining technology and support methods. In the optimized scheme, the manual + electric winch combined mining and mining to improve the mining efficiency, the first mining layered using high-strength polyester fiber mesh + hollow grouting anchor cable combined support, other layered mining approach and Filling the contact lanes with wooden shed support, effectively changing the support method and improving safety. According to the results of breakeven analysis and sensitivity analysis, the optimized scheme has a strong overall risk resistance capability.
references:
[1] Lai Wei. Experimental study on mining method of complex steep inclined thin vein [D]. Changsha: Changsha Mining Research Institute Co., Ltd., 2012: 16-24.
[2] Xiao Youding, Li Yuran, Wang Yuanliang. Experimental study on the underlying layered cement filling method of Qianhe Gold Mine [J]. Metal Mine, 1995 (1): 22-25.
[3] Yang Zhifang, Wang Xiaochun, Fu Wenjiang. The application of the downward stratified cement filling mining method in Qianhe Company [J]. Gold, 2011, 32 (3): 33-37.
[4] Li Xiangdong, Sheng Jia, Wan Bing, et al. Research on safe mining technology scheme for steeply inclined weak broken thin vein [R]. Changsha: Changsha Mining Research Institute Co., Ltd., 2014.
[5] Wang Xinmin, Zhao Bin, Zhang Qinli. Mining method selection based on analytic hierarchy process and fuzzy mathematics [J]. Journal of Central South University (Natural Science Edition), 2008, 39(5): 875-880.
[6] Zhu Zhuohui, Zhao Guoyan, Wu Guixiang, et al. Fuzzy optimization of mining schemes [J]. Mining Technology, 2005, 5(4): 12-14.
[7] Ma Pengfei, Sheng Jia, Li Qiang. Optimization of mining method for inclined medium-thick and low-grade gold deposits in complex group empty area [J]. Mining Technology, 2012, 12 (03): 18-19.
Sheng Jia, Jiang Feifei; Changsha Mining Research Institute Co., Ltd., Changsha 410012, China; National Metal Mining Engineering Technology Research Center, Changsha 410012, China;
Source: Mining Technology: 2016, 16(2);
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