Underground Methods

Orebodies generally are either vein-type, they have a shape that is either tabular or massive. This will influence the mining method chosen together with ore regularity and thickness.

Vein-type orebodies most of the time dip steeply, permitting ore to fall to a lower mining level where it can be loaded. Most of the time, the orebodies are often irregular and narrow, so care must be taken to prevent mining barren wall rock. They are most successfully mined by underground stoping in small scale.

Massive orebodies are big and most of the time have a shape that is irregular. Underground bulk mining methods, with large stopes, are best suited to this kind of orebody.

Tabular orebodies are flat or gently dipping and the ore, having no place where to fall, has to be handled where it is blasted. Thicknesses of the orebodies are varied. Room-and-pillar mining is typically used to extract the ore. These types of deposits tend to be moderate- to high-tonnage producers, depending on the thickness and lateral extent of the ore.

The strength of the ore and the rocks that surround an orebody influence the method (and therefore the costs) used to mine the orebody too. Openings can be supported or self-supported. Some supported openings are held up by aggregate, waste rock or backfill which are placed in the openings immediately after they are mined out. Yet others are held up by timber sets which are supports made of steel or timber, even though this kind of mining is expensive and is rarely used nowadays.

Self-supported opening stand up with little artificial support. The pillars and walls have enough strength of their own to carry the weight of rock above them and the horizontal stresses in the rock caused by tectonic forces – even though the miner can help them along with screening and bolts of rock. It is common to plan for the mining of pillars in massive orebodies. This is done by backfilling the mined-out stopes to provide the necessary support when the pillars are mined.