Open-cast Mining

Open-cast mining is one of the most popular surface mining methods mostly employed for bedded deposits. The kind of minerals or rocks mined this way are found near the surface; where the overburden (surface material covering the valuable deposit) is relatively thin or the material of interest is structurally unsuitable for tunneling. Terms open-cast and open-pit mining have always been interchangeably used to refer to an excavation or cut made at the surface of the ground to extract ore and which is open to the surface for the duration of the mine’s life. However, these two terms don’t exactly mean the same thing. The major difference between the two is that the overburden in open-cast is not transported to waste dumps for disposal, but it is cast into adjacent mined out panels.

The first step in any surface mining involves excavation and relocation of the overburden to expose and mine the ore. Once the ore is exposed, suitable procedures are employed to recover the ore depending on geologic, engineering and economic factors. For bedded deposits like coal seams, open-cast proves to be the most efficient method for near-surface ore. Casting overburden on mined-out areas means that material handling during mining is just excavation and casting, which can be done by a single machine. This also enables mining to be concentrated in small areas, and mining means that reclamation on mined-out areas is done almost immediately. This method allows steep high-wall during mining since the pit is kept for a short period of time.
In some cases, casting is done partially together with haulage and the use of conveyors. This method allows usage of the largest mining machines (like draglines), which enhances productivity and lowers production costs. The main disadvantage of this method is where operations rely on one machine; any major machine breakdown has dire consequences on the activities of the mine.

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