In the case of ore bodies in masses or veins, mining develops vertically downward through successive pits containing both ore and waste rock, which must be excavated and moved as the mining operations deepen.
This is a general method called global excavation. It involves a large crater whose profile consists of benches. The crest of each bench is represented in plan view by a closed curve.
If the region is mountainous, some benches may be incomplete, which allows, from time to time, the creation of new, deeper benches by advancing the mining front further into the ground.
This type of mining has two main characteristics:
- The execution of mining operations is irreversible, as their progression is based on a preliminary study of the ultimate (final) shape, and it is practically impossible to deviate from it later on. This is due to the significant stripping ratio that may occur when trying to extract a mineralized portion not included in the final pit design.
- The stripping ratio depends on the depth of the operation and the morphology of the deposit. Its variations can be significant between two successive mining phases under certain conditions.
Therefore, the planning of mining production is one of the critical challenges of this type of operation. This method requires the preparation of external land close to the mining area for purposes specifically intended for that use.
