Open-pit mining is a mining method for near-surface deposits via a surface pit excavated using one or more horizontal benches. Overburden is first removed and benches of set heights excavated to reach the minable depth of the deposit, with the higher benches being larger than the lower ones.
The benches are able to control the depth of blastholes, pitwall slope and avert danger posed by highwall slopes. They also provide enough face length to enable sustained and uninterrupted production, with careful balancing between stripping and mining being done to ensure stripping costs are covered and long-term plans achieved. Benches should have enough space to allow accommodation and movement of material handling equipments and the pitslope is dictated by soil/rock mechanics.
This method is widely used because of its low operational costs hence convenient for low grade ores, and ability to use highly mechanized production equipments that are capital intensive but labor conserving.
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