Block caving is large-scale mining method that allows for huge volumes of rock to be extracted efficiently. However, the development time before production starts is longer compared to other mining methods. By drawing rock from the extraction level in the lower part of the mine, a gap is created. Absence of support for the overlying rock mass together with rock stress and gravity will cause the rock mass to cave.
This minimizes drilling and blasting of ore but requires the ore body to be large enough and the rock condition so to be favorable for natural breakage. To draw the first pieces of rock, to create this gap, the rock mass in the lower part of the ore body needs to be broken down into smaller pieces. To achieve this, an undercut level is developed and blasted. Below, an extraction level is developed where ore will be extracted throughout the life of that production area. Drawbells are created between undercut and extraction levels and become passages for caved rock. To avoid misfires, accurate drilling is crucial. Substantial rock reinforcements such as steel arches, sprayed concrete, cable bolts, rock bolts, steel mesh and straps are usually required due to several factors associated with block caving, including extreme rock stress changes and a long production period. Rock is loaded from the draw points and can be dumped into ore passes connected to a haulage level or directly to a crusher.
A variety of transportation methods can be employed for transporting ore to the surface. The fragmentation of the ore and the crushing requirements are key factors influencing the choice of a method. The extraction of ore will sooner or later cause the surrounding rock to cave, resulting in subsidence at the surface. Provided the rock breaks successfully and the ore can be extracted evenly at desired draw points, block caving is a high productivity method with low operating costs that allows a high degree of mechanization and capability of automation.
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