1.What is open pit mining?

Open pit mining is the process of removing the covering from the ore body to obtain the desired minerals. Open-pit mining can be divided into open-pit metal deposit mining, open-pit coal mining, and open-pit iron mining. The former mainly mines non-ferrous metals, the middle mainly mines coal and some non-metallic ores, and the latter mainly mines iron ore.

Open pit mining

During open pit mining, rock and soil are removed in layers. Open pit mining involves excavation that looks like a platform. Cuts are made at ground level and work is done around the perimeter of the mine at this depth. Once the minerals and waste have been removed from the layers (called steps), the excavation begins on the ground floor and the work begins again. This type of surface mining, also known as hard rock mining, is often used to extract metallic ores such as copper, gold, iron, aluminum and other minerals.

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2.Methods of open pit mining

According to the distribution of deposits, there are generally two types of mining methods:

① Mining methods for flat deposits

It is suitable for gentle deposits whose dip angle is generally less than 12°. Dump mining method The stripped material is dumped directly in the goaf of the previous mining belt with a mechanical shovel or a rope bucket, and the mining working face is pushed forward following the stripping working face. Under the same conditions, the weight of the mechanical shovel is about 1.8 times that of the rope bucket, so when peeling off high steps, the rope bucket is often used. Two or more stacks can be used to peel off higher steps. The scheme includes one mechanical shovel with one rope bucket, two rope bucket shovels cooperate with each other, or only one rope bucket shovel is used as secondary dumping, etc.

Shrinkage-stopingmining

The exfoliated material is transported to the goaf with a dump bridge and a cantilever dumper in a direction perpendicular to the working line. The spatial relationship between the exfoliation step and the advancement of the mining step is also limited by the specifications of the transportation equipment, but it is not as strict as the dump mining method. This method can be adapted to a larger peeling thickness, the peelable thickness of the AFB-60 dump bridge in the GDR is 60m.

power-shovel

Longitudinal mining method The stripped material is transported longitudinally to the goaf along the working line, bypassing the end gang. This method is not limited by the specifications of mining and transportation equipment and the thickness of the stripped rock, and has greater flexibility. It is suitable for various processes such as single bucket-locomotive vehicle, single bucket-(crusher) belt conveyor, single bucket-automobile, wheel bucket-locomotive vehicle-belt conveyor and so on.

Mining methods for flat deposits

The economic effects of the above methods are usually the best by the stacking method, the second by the horizontal method, and the worst by the vertical method. However, the applicable peel thicknesses are reversed. When the peeling thickness is large, the stacking method or the horizontal method can be used on the lower step, and the longitudinal method can be used on the upper part. In order to shorten the transportation distance, the ore field can be divided into several mining areas, mining in a certain order, and the stripped material can be discharged to the mining area or the goaf of the previous mining area.

② Mining methods for inclined deposits

Basically, the exfoliated material is transported to the outer dump, and only after the excavation work reaches the final depth, can the goaf be used for drainage. The layout of the working line is basically arranged along the strike of the ore body and vertical to the strike of the ore body.

Mining methods for inclined deposits

The selection of the initial position and the advancing direction should comprehensively consider factors such as the topographic and geological conditions of the deposit, production capacity, transportation methods, the amount of infrastructure stripping and the balance of production and stripping ratios. The production stripping ratio of inclined deposits varies during mining. In order to reduce the amount of infrastructure stripping and delay the peak of stripping, balance the production stripping ratio, and improve the economic effect, the following measures can be taken to steepen the working slope angle.

Combination of steps

A group of adjacent steps are excavated in sequence with one piece of equipment, and only a working platform is set on the excavation steps, and other methods are also available.

Horizontal mining belt

The horizontal mining belt for automobile transportation, the adjacent steps are followed for mining, and the working line is arranged horizontally and pushed forward vertically. There is only one working platform on any cross section, and 1-2 sets of mining equipment can be installed on each step. Compared with the combined steps, this method can arrange more mining equipment.

Conclusion

Surface mining is considered one of the most dangerous industries in the industry. It has a major impact on miners' health as well as ecological land. Surface mining causes changes in vegetation, soil and bedrock, and ultimately changes in surface hydrology, groundwater levels and water flow paths. Additionally, open pit mining can produce harmful pollutants, depending on the type of minerals mined and the type of mining process used. Therefore, current mining companies will choose the method of open-pit mining according to the situation, and will also treat the mine after completion to avoid pollution.

Surface mining

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