Optimization design of open pit to underground mining

0 Preface

Slate mining company located in Baishan City, Jilin Province, Jilin Province Tonghua Iron Steel Group under the major mining companies, mining consists of several mining slate mine, mine on the Green, No. 8 mining groups, etc., of which 8 ore group Originally open-pit mining, it has been converted to underground mining. The mining method is a sub-column-free sublevel caving method. The initial design of the open pit after the open pit is crucial to the production work after the mine is connected. Therefore, it is necessary to optimize the mining design when the open pit is turned according to the geological characteristics of the ore body and the actual conditions of the mine to ensure the connection. smoothly.

l Mine geology

The No. 8 ore body has a length of about 1020 m, which is between 1020 and 480 m, and the overall trend is near EW, which tends to SW. F202 plus: The fault divides the ore body into two parts, the ore body exposed on the eastern surface is located under the F202, and the ore body exposed on the northern surface is located on the upper plate of the F202 fault. The No. 2 ore body in the lower section of the fault has a large scale, tending to SN, tending to W, and the inclination angle is 350°-400°. Both ends of the ore body are bent by the twisting structure, and have wavy folds in the direction of the strike or inclination. The ore body has a horizontal width of up to 56m, a maximum extension of 866m, a vertical thickness of up to 48.16m, and a maximum thickness of 40.33m.

Metallic minerals magnetite, maghemite containing a small amount, hematite, pyrite, limonite, pyrrhotite, average ore grade: 35.31%.

2 Determination of stope structure and parameters

2.1 nugget structure parameters

According to the length of the ore body and the production management and 648m tunnel, combined with the network of the exploration line, the ore body is divided into 4 ore blocks. The length of the nugget is 60 m, the segment height is 12 m, and the approach spacing is 12 m. When the thickness of the ore body is greater than 15 m, the vertical ore body of the approach is arranged; when the thickness of the ore body is less than 15 m, the approach is arranged along the ore body. The 780, 770, and 758 m horizontal alignment design plans are shown in Figures 1, 2, and 3.

Figure 1 780 m horizontal mining design plan

Fig. 1 Plane map of mining preparation design on 780 m level

2.2 Determination of the slippery well

Since the open pit bottom level is 770 m after the end of open pit mining, the exposed ore body space changes with the original design. The original design of the ore body under the ore chute (KL5) has an upper elevation of 770 m, which causes the ore chute to penetrate with the open pit. When the open-pit mining ends the backfill rock to form a cover layer, the rock will slide through the chute to the 648 m level. The slipper is unusable. In addition, the rock slide (YL3) is also separated by the exposed ore body space, which is located near the open air side, causing the lower part of the ore body to be unloaded along the vein lane and through the vein lane.

In order to recover the above-mentioned ore body above the 770 m level of the No. 2 ore body and the No. 3 ore body above the 780 m level, the upper level of the ore retaining well (KL5) is changed to a level of 758 m at the level of 758 m, and is designed in the middle of the upper part of the ore body. 1 inverted section (758-770 m), the diameter of the chute is 2.5 m, all the ore that has collapsed in the middle of No. 2 ore body is slid through the inverted section to 758 m level, and transported to other ore by electric scraper. Sliding well.

Figure 2 770 m horizontal alignment design plan

Fig. 2 Plane map of mining preparation

Design on 770 m level

Figure 3 758 m horizontal alignment design plan

Fig. 3 Plane map of mining preparation

Design on 758 m level

When mining the No. 3 ore body above 780 m level, due to | rock chute (YLl, YL2), the original design of the ore chute (KLl) is 770 m, and the return air of the development system is 770 m. It is necessary to redesign the ore chute and the pedestrian equipment well. Because the No. 3 ore body has a long trend, in order to meet the effective distance of the ore mining equipment, the rocky shaft (YLl and ore chute) at the eastern end of the ore body is extended to 780 m horizontal (vertical), and the ore at the eastern end of the 780 m ore body passes YLl. Decentralized to a level of 648 m, it can meet the requirements of the eastern end of the ore body mining. If the ore shaft in the middle and west end of the ore body is extended to 780 m level according to this method, the ore column needs to be retained when mining more than 770 m ore, resulting in low ore recovery rate and inconvenient management: in order to maintain the ore recovery rate without leaving the ore column In the middle and west of the ore body, an additional inverted shaft (and equipment well) is added. The diameter of the chute is 2.5 m. The ore of the '780 m level in the central and western parts of the No. 3 ore body is all slid through the inverted section to 770. The m level is then transferred to the ore chute (KlJ2) via an electric scraper. In addition, an additional pedestrian well (both into the wind well and safety exit) was added, and a ladder room was placed in it. 780 m of production water and wind supply, water pipes and workers entering and leaving the 780 m level passed through the well.

3 Arrangement of return air wells

A return air patio is built from 708 to 770 m. A return air return patio (and a safety exit) is drilled at the end of the ore body. The elevation of the return air patio is 770 m and the lower elevation is 708 m. Service 708 Ventilation of sections of ~770 m horizontal.

4 cutting and mining work

4.1 minimum recoverable thickness

In order to fully recover the underground mineral resources, the minimum recoverable thickness of the designed ore body is 2 m, and the thickness of the stone removal is 1.5 m.

4.2 Approved work

The lower plate along the vein lane should be as close as possible to the ore body, and the upper and lower sections of the penetrating roadway should be arranged in a rigid arrangement according to the diamond shape. In order to ensure the stability of the rock under the ore body and meet the requirements of the mining equipment, the 758 m, 780 m horizontal section of the lower plate along the pulse lane and the 770 m horizontal plate along the pulse lane and the elevator shaft and equipment well junction.

4.3 Rock drilling work

Drifting using YT-29 type gas leg rock drill, chute digging chisel using the YSP-45 type to type drilling machine primers, subparagraph ore using YGZ-90 type rail drilling machine, using a vertical gun to the scallops.

4.4 Blasting work

Smooth blasting is used for roadway excavation and chute digging. Medium-deep hole blasting adopts the method of differential blasting.

4.5 recovery work

According to the requirements of the bottomless sublevel caving mining method, the mouth is returned from top to bottom. First, we will recover 780 m of ore, and recover from the two ends of the ore body to the middle of the ore body, and then recover 770 m and 758 m of ore. When the 770 m is recovered, it is placed on the upper plate along the vein lane, and the mining order is picked up by the white plate.

5 stope drainage

The self-flow drainage method is adopted, and the underground water inflow and the upper water seepage are discharged through the sub-segment drainage ditch and the discharge water discharge well to the 708 m auxiliary development roadway to reach the air intake well, and are discharged to the 648 m level, and then discharged to the main transport flat Surface.

During the transition from open pit to underground, in order to ensure that a large amount of water in the open pit suddenly floods into the well, it is necessary to first discharge the water in the open pit and complete the construction of the drain well (648-770 m) before the formation of the cover layer. Secondly, the roadway and the open pit are drilled in time at the 770 m level. When the cover layer is formed, the surface water penetrates into the well through the cover layer and is discharged to the 648 m transport lane through the drain well in time, so that there is no sudden water inrush.

6 downhole ventilation

After the fresh airflow reaches the transportation level of 648 m from the main inlet wind well, it enters the working face of each section through the equipment well of the mining area (which also enters the wind well), and the dirty wind after flushing the working face enters the 770 from the returning wind patio of the mining area. The m-level total return airway is then discharged from the main return air well to the surface. In order to ensure the ventilation effect, the regulating damper should be added near the equipment wells and elevator shafts of 758 m and 770 m horizontally, and the upper mouth of the ore shaft after the end of each section of mining should be closed in time.

7 Conclusion

The key to open-pit mining is to ensure the replacement of mining capacity. It is necessary to recognize the complexity of various impacts and constraints. In particular, when opening the first floor of underground mining, it is necessary to formulate a technically feasible design. Good or bad will directly affect the mine's production capacity, technical and economic indicators, and the economic benefits of the mine. Therefore, it is necessary to systematically consider various influences and constraints, and avoid the various factors and links that restrict production after being transferred to underground mining.


[1] Zhang Fumin. Mining Design Manual Underground Mining Volume: M:. Beijing: China Building Industry Press, 1989.

[2] Shen Jiliang, Cui Yunlong, Wang Jiefeng. Construction Engineering Manual Volume III [M]. Beijing: Coal Industry Press, 1986

[3] Design of the engineering project for the open pit of No. 8 mine group. Anshan: China Metallurgical North Engineering Technology Co., Ltd., 2005.

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