Optimization of mining method for Shizishan lead-zinc mine

Lion lead zinc silver mine in August 2011 to begin pilot production in 2012 and put into production in 2013 reached. At present, the scale of mining and mining has been stable at 2000t/d. The mining objects mainly include three ore bodies of I, II and V, and the No. I ore body belongs to the main ore body of the mining area. The mining area is divided into 7 middle sections of 1300, 1250, 1200, 1150, 1100, 1050 and 1000m. The feasibility study report recommends the use of the upward horizontal layered filling mining method. Because the actual ore body and the surrounding rock joint fissures are very developed, the roof is broken, the stability is poor, and the personnel equipment cannot enter the operation in the stope. Therefore, the mine is currently in the first place. In the middle section of the 1200m mining, the horizontal medium-deep hole stratified collapse mining and mining method is used for mining. However, problems such as the loss of mining depletion indicators are not ideal, and the pillars are not recovered. Therefore, it is imperative to seek reasonable mining methods, determine reasonable process parameters, and improve the comprehensive economic benefits of mines.

1. Mining technical conditions

The characteristics of the ore body, the No. I ore body is the main ore body, and its resources account for more than 80% of the total resources of the mining area, and the rest are small ore bodies. The No. I ore body is generally northeast, tending to the northwest, with an average inclination of 59° and an average thickness of about 30.00 m. The ore is of high value and belongs to rich ore. The ore body has a more uniform distribution of useful components and a relatively stable thickness change.

Most ore bodies in the mining area are produced in the interbedded structures of argillaceous rocks, sandstones and dolomites . The surrounding rocks of the top and bottom plates are dominated by dolomite and marble , with a small amount of sandstone and argillaceous rocks. The exploration report shows that the ore body and the top and bottom plates are hard rock groups with moderate stability. After the underground actual project was exposed, the surrounding rock and ore body of the near mine in the stope were all shallow metamorphic limestone, marble, dolomite and so on. The surrounding rock and ore body joint fissures are developed (the average spacing is estimated to be ≤50-80mm), the rock hardness is f=6~8 (medium or medium-down), and the roof is broken, which is an unstable ore type.

The hydrogeology of the mining area belongs to the medium type mainly composed of dissolution and fissure water filling. The geological environment is moderate, and the current geological disasters are weak.

2. Difficulties in mining technology

The choice of mining method is mainly for the main ore body of No.1. The ore body belongs to the steeply inclined medium-thickness-thick large ore body, with high grade, high ore value, developed rock joint fissures, and poor stability of ore rock, only considering mining technology. It is more suitable to use the caving method. The method has the advantages of simple production process, large production capacity and low cost. However, considering the actual conditions of the mine and the mining technical conditions, the caving method also has many shortcomings and technical problems. as follows.

(1) Depletion and loss indicators are large, generally achieving a loss rate of 20% to 28% and a depletion rate of 18% to 25%. The method wastes resources, and a large amount of waste rock is mixed in the mining process, which also increases the processing cost in the mining and mineral processing process. The ore has a high grade and high ore value and is not suitable for mining by caving.

(2) Mining by caving will cause the surface to collapse, and at the same time destroy the vegetation and structures in the subsidence area, causing a certain degree of damage to the environment. It is contrary to environmental protection and requires land acquisition fees and reclamation costs. Because the mine is located in Yingjiang County, Yunnan Province, the rainfall is abundant, and the upper part of the ore body is steep and steep, and there is a large amount of covering soil on the surface. With the development of the ground collapse, there will be a large amount of soil and mud water pouring into the mining area, which will worsen the underground working environment. .

(3) The mine mines the 1~5 stope of the No. 1 ore body in the middle section of the 1200m, and the 6~9 stope of the V-type ore body, all of which are mining houses. According to the mining reserve consumption account from August 2011 to July 2014, a total of 1.04 million tons of ore was collected, forming an empty area of ​​about 27×104 m3. According to the current status of mining, the medium and deep hole stratified collapse mining and mining method is now used for mining. If the mining method is used again, the first mining area is difficult to select, and the ore after the collapse will cause the ore in the middle section of 1200m or more to be difficult to recover.

(4) The caving method cannot fill the tailings to the underground, and all the tailings produced by the plant will be discharged to the tailings pond, which will lead to large inventory pressure in the tailings pond and increase the safety risk of the tailings pond. After the mine is closed, it is necessary to invest in environmental protection such as tailings pond water treatment, solid waste treatment, and reclamation.

3. Mining method selection

According to the poor stability of the ore rock, the mine is not suitable for the stage filling method and the upward horizontal stratified filling mining method, which require medium stability and above conditions of the ore rock, and is unstable and valuable for the mining rock. The ore is suitable for the upward approach mining method (Scheme II), and the mining method is further technically and economically compared with the existing level of the deep hole retention ore filling method (Scheme I) of the mine to determine the optimal Mining law program. The main technical and economic indicators of each mining method are shown in Table 1.

According to Table 1, it can be seen that the economic and technical indicators of the upward approach filling mining method (Scheme II) are obviously superior to the medium-deep hole ore filling method (Scheme I). In addition, the advantages and disadvantages of the two schemes are Comparison:

(1) Although Scheme I is superior to Scheme II in terms of production efficiency and production cost index, the mining scheme has a certain degree of incompatibility as underground mining conditions reveal that the ore conditions have become unstable.

The exposed area of ​​the top plate and the upper and lower plates of the scheme I is large, which is easy to cause the surrounding rock to collapse, and the loss of depletion is large. If the slump is serious, it may cause the ore of the stope to be difficult to release. On the contrary, Scheme II has a small exposed area and can well control the pressure of ground pressure and depletion.

(2) The depletion rate of the scheme II is low, which is 9% lower than the depletion index of the scheme I, thereby reducing the waste rock transportation and beneficiation cost, and reducing the production cost to some extent.

(3) Good economic returns. Program â…¡ ore mining rate and metal recovery rate is high, thus increasing economic efficiency.

In summary, Scheme II is superior to Scheme I in technical and economical mining. Therefore, the No. 1 main ore body and the V-type ore body are recommended to adopt the upward approach filling mining method.

4. Mining process

4.1 Nugget layout parameters

The stope is arranged along the ore body, with a length of 40m and a width of the ore body. The middle section is 50m high and the section height is 12.5m. Each stope is arranged along the cutting cross-section and the ore body, and the inlet specification is wide × height = (3.5 ~ 4) m × (3 ~ 4) m. The pulse outside sampling is Φ3.0m, and the filling return well specification is 2.0m×2.0m.

4.2 mining cutting

Adopting the pulse external sampling method, the mining and cutting engineering mainly includes segmented roadway, layered communication road, cutting cross lane, filling return air well, and pulse outflow well.

4.3 mining process

Upward approach filling and mining method The approach in the stope adopts the mining mode of one mining and one mining. The mining block is divided into several ways according to the width of the access road of 3.5~4m. After one step, one mining and one mining road will be taken. After the road is recovered, the filling will be carried out. After the first step, the filling strength of the inlet is up to the required level, and then the second step is to recover the filling body between the filling bodies and fill the inlet after the mining.

(1) Rock drilling and blasting: AtlasCopco Boomer281 single-arm rock drilling rig for rock drilling, horizontal drilling, hole depth 3.5～4.0

m, the aperture is 43 to 45 mm, and the footage is 3.3 m per cycle. In the second step, the distance from the peripheral eye to the filling body is about 0.5m to protect the one-step filling body and reduce the depletion. The cylindrical modified ammonium explosive charge is used, and the non-electrical detonation initiation system is detonated.

(2) Ventilation of the stope: fresh air flow from the middle section of the lane → ramp road → section roadway → layered communication road → cutting cross lane → access road surface. Sewage from the mining site → filling back to the wind well → upper middle section returning to the wind.

Since the roadway mining is a single-headed working face, it is necessary to use the auxiliary fan ventilation. After the blasting, the general ventilation is 45 to 60 minutes before entering, and the guns can be cleaned before entering the working surface.

(3) Roof management: After the ventilation of the stope, check the roof and the two sets of ore, remove the loose rock, and then carry out the mining and leveling work, and carry out anchor net reinforcement for the unstable section of the roof.

(4) Mining in the stope: Using 2m3 scraper, the caving ore will be cut from the working face through the cutting cross-section→stratified contact road→segmented alley, and pour into the extra-pulse chute. The mining efficiency is about 200t. / Taiwan class.

(5) Filling: 2.5 to 3.5 m in the lower part of the first step is filled with a filling body with a sand-cement ratio of 1:6, and the upper 0.5 m space is connected with a filling surface with a sand-to-cement ratio of 1:4. Top filling; 2.5-3.5m in the lower part of the two-step approach and the layered contact road is filled with cement with a sand-to-cement ratio of 1:15, and the upper 0.5m space is filled with a 1:34 filling ratio. To facilitate the walking of trackless equipment.

(6) Transfer layer: After each layer is finished, the cutting cross-section and the layered contact track are raised 1.5m before the last road filling, and then filled. After the filling body reaches the curing strength, the layered communication road and the cutting roadway are continuously raised to a layer height to complete the layering work.

5 Conclusion

The No. 1 ore body of Shizishan Lead-Zinc-Silver Mine belongs to steeply inclined medium-thick to thick ore body with high grade, high ore value, developed joints and fractures of ore, and poor stability of ore. It is more suitable from the perspective of mining technology. The caving method is used for mining, but considering the actual conditions of the mine and the mining technical conditions, the medium-deep hole ore filling method and the upward approach filling mining method are selected, and the main technical and economic indicators of the two mining methods are comprehensively compared. Advantages and disadvantages, the upward approach filling mining method is better and more suitable for the mining of No. I ore body. Studying and optimizing the mining method and related mining technology of the Shizishan lead-zinc mine has a good reference for the mining of similar ore bodies in other mines.
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Author: Zhang Dong Wei; Wuhan Institute of Rock and Soil Mechanics Chinese Academy of CO2 geological storage group, Wuhan 430071, China;

Liu Mingrong; Changsha Mining Research Institute Co., Ltd., Changsha 410012, China;
        Source: Mining Technology 2015, 15(5);
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