Mine shafts are vertical or near-vertical tunnels, which are "sunk" as a means of accessing an underground ore body, during of the development of an underground mine.
The shape (in plan view), dimensions and depth of mine shafts vary greatly in response to the specific needs of the mine they are part of and the geology they are sunk through. For example, in North and South America, smaller shafts are designed to be rectangular in plan view with timber supports. Larger shafts are round in plan and are concrete lined.
Mine shafts may be used for a variety of purposes, including as a means of escape in the event of an emergency underground and allowing for the movement of:
Mine services (such as compressed air, water, backfill, power, communications and fuel)
Broken rock (in the form of payable ore, or non payable waste)
Or any combination of the above
When the top of the excavation is the ground surface, it is referred to as a shaft; when the top of the excavation is underground, it is called a winze or a sub-shaft. Small shafts may be excavated upwards from within an existing mine as long as there is access at the bottom, in which case they are called raises.