The current mining methods for steeply inclined very thin veins are mainly shallow hole retention method and wall filling method. The shallow hole retention method has the advantages of simple mining process and low labor intensity, but the ore depletion rate is high, the ore grade is low, and the transportation volume is large. The wall filling and mining method has low ore depletion rate and high ore grade. The transportation volume is small, but the mining process is complicated, the labor intensity is large, the material consumption is large, and the mining cost is high [1].
Suitable methods for the selection of mining, ore Comparative Test Method described herein and left scarps through shallow hole filling method for a silver-lead-zinc ore Mongolian multiple metal to a thickness selected depending on ore mining methods, that end of ore The critical value of the thickness was studied.
1 Overview

A silver-lead-zinc polymetallic ore in Mongolia is a series of nearly parallel high-inclined vein-like ore bodies formed in the cracks of fine-grained rock of yellow iron . The boundary of the ore is obvious. The ore metal content is rich, the average grade: silver 293.19g / t, lead 6.57%, zinc 3.91%, copper 0.21%, gold 0.66g / t. The ore body has an inclination of about 70°. The ore body has a thickness of 0.4 to 1.2 m and an average thickness of 0.80 m, which is a very thin ore body.
2 mining methods
2.1 shallow hole retention method
After entering the stope through the patio, the personnel will drill and blast, and some ore will be mined after the ore collapses. The remaining ore remains in the mine as an upward recovery platform, and the mine will be discharged once after the mining. The main advantages of this method are: simple process, low mining cost and high production capacity; main disadvantages: high ore depletion rate, thinner ore body, higher ore depletion rate [2].
The mining method is shown in Figure 1.

2.2 cutting wall filling method
After entering the stope through the patio, the personnel drilled and blasted, and the ore that collapsed was placed in the chute in the center of the stope. In order to form the minimum working face width required for mining operations, the surrounding rock is rocked and blasted, and the collapsed waste rock remains inside the mine as a platform for continued upward recovery and plays a role in supporting the surrounding rock. The main advantages of this mining method: can achieve mineral and rock mining, and effectively reduce the depletion rate of ore; main disadvantages: complex process, high mining cost, low production capacity [2]. The mining method is shown in Figure 2.

2.3 Comparative test
The ore is mined by shallow hole retention method, and the ore depletion rate has been maintained at more than 50%. In recent years, the price of ore has fallen. In order to reduce the depletion rate of ore and improve the economic benefits of mines, the method of cutting wall filling mining has begun. The main factor affecting the choice of mining method is the thickness of the ore body. For this reason, the mine uses two mining methods to conduct comparative tests under different thickness conditions, and the corresponding mining capacity and ore depletion rate of the two mining methods are calculated. The main technical data is shown in Table 1.

3 Conclusion

(1) The depletion rate of the ore filling method is lower than that of the shallow hole retention method. When the thickness of the ore body is lower than the width of the minimum mining face (0.8m), the difference between the two is obvious; when the thickness of the ore body is larger than the width of the minimum mining face (0.8m), the difference between the two is small.
(2) The mining capacity of the shallow hole retention method is larger than that of the wall filling method. When the thickness of the ore body is lower than the width of the minimum mining face (0.8m), the difference between the two is obvious; when the thickness of the ore body is larger than the width of the minimum mining face (0.8m), the difference between the two is small.
(3) Combining the advantages and disadvantages of the two mining methods, through the comparative test, it is determined that the critical value of the ore body thickness converted by the shallow hole retaining method and the wall filling method is 0.8m, and the shallow body thickness is less than 0.8m. Hole retention method, when the thickness of the ore body is greater than 0.8m, the wall filling method is adopted. After a period of production, the mine ore depletion rate is stable at around 30%. Compared with the previous shallow hole retention method, the ore depletion rate has been significantly reduced.
references
[1] Yang Wenzhu. Current status and development trend of mining technology for steeply inclined thin veins [J]. Hunan Metallurgy, 1993 (2): 59-61.
[2] Guo Jinfeng. Experimental study on mining method of steeply inclined thin ore body [J]. Yunnan Metallurgy, 1995 (2): 13-19.
Author: Wang Junsheng; China Railway Engineering Consulting Group Co., Ltd;
Xuanzupu , Bailu ; Jinjian Engineering Design Co., Ltd.;
Article source: "Modern Mining"; 2016.7;
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