What is a mine shaft?
A shaft is an underground vertical or inclined passageway. One example, miners dig straight down, or almost straight down, until they reach their desired depth. Then the mine begins to branch out in all directions. Miners will enter or exit a mine through a lift or elevator installed where the initial vertical tunnel was dug. Shafts can also be created for a number of other reasons including ventilation or emergency exits.
Shaft lining / Lagging
The shaft lining performs several functions; it is first and foremost a safety feature preventing loose or unstable rock from falling into the shaft. It also provides a place for shaft sets to attach to. Lastly, it provides a smooth surface to minimize resistance of the airflow for ventilation. Smaller shafts generally are designed to be rectangular with timber supports. Larger shafts can be round and are concrete lined. The final choice of shaft lining is dependent on the geology of the rock which the shaft passes through. Some shafts have several liners, whereas shafts sunk in very competent rock may have no requirement for lining at all.
Shaft Sets & compartments
Where the shaft is to be used for hoisting it is frequently split into multiple compartments by Shaft Sets made of timber. Vertical members in a shaft set are called Guides, horizontal members are called Buntons. Mine platforms run on the guides in a similar way to how a steel roller coaster runs on its rails, both having wheels which keep them securely in place.
The largest compartment is typically used for the mine cage, a platform used for moving workers and supplies, which is suspended from the hoist on steel wire rope. It functions in a similar manner to an elevator.
Additional compartments can be used for a number of reasons such as skips, emergency exits, housing an auxiliary cage or a system of ladders. An additional compartment may even house mine services such as high voltage cables and pipes for transfer of water, compressed air or diesel fuel. Another reason to divide the shaft is for ventilation. One or more of the compartments discussed above may be used for air intake, while others may be used for exhaust.