Methods of Mining
The method is everything
There is a wide variety of methods of extraction which one can choose from as the orebodies have shapes and sizes. The orientation and shape of an orebody, the strength of the ore and the surrounding rock and the form in which the valuable materials are distributed are different for each ore area. These factors among others are what will influence the selection of a mining method and the overall plan for developing the orebody.
Operating mines vary in size from small underground operations (some of these operations have only a few levels of production and may produce less than 100 tonnes of ore per day) to the large open pits (some of which move thousands of tonnes or ore and waste rock per day).
Getting Down to the Bottom
The primary opening into an underground mine can either be a shaft, a ramp (which can also be called a decline) is driven downinto the earth, or an adit which is a horizontal opening that is driven into the side of a mountain or hill. They all have the same purpose – to provide access for people, equipment and materials and to supply a way of making ore to be brought to the surface.
Most of the time, shafts are vertical, but they can also be inclined, they are equipped with headframes and hoists, the headfames are the structures at the top of the hoist which enclose it.
On the other hand, ramps, most of the time spiral downward at a gradient of about 15% to permit access into the mine by mobile equipment which are rubber-tired. In few cases, the ramps are driven in straight lines to accommodate conveyor belts, or they have straight runs with switch back points. Ramps are in most cases cheaper than shafts when it comes to developing. But the total cost might be higher than the cost of developing a shaft to reach the depth desired when it is dependant on the angle of the decline, the size of the opening and the encountered ground conditions.
Level or horizontal mine workings are called drifts and crosscuts. At times it is useful to open vertical workings between levels in a mine which is underground; they are called winzes or raises.