Shaft sinking

Shaft sinking is one of the most difficult of all mining development methods: restricted space, gravity, groundwater and specialized procedures make the task quite formidable.

[3] Today shaft sinking contractors are concentrated in Canada, Germany, China and South Africa.

For example, in North and South America, smaller shafts are designed to be rectangular in plan view with timber supports.

[6] 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: 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.

Many other global mining jurisdictions have adopted this rule and shafts are therefore often found in pairs (although there are multiple alternative methods of providing a second means of egress).

Shotcrete, fibrecrete, brick, cast iron tubing, and precast concrete segments have all been used at one time or another.

To ensure the safety of persons working on the shaft bottom temporary ground support is installed, usually consisting of welded mesh and rock bolts.

Research and development in this area is focusing on the robotic application of shotcrete and the commercialisation of thin sprayed polymer liners.

Some shafts do not use guide beams but instead utilize steel wire rope (called guide rope) kept in tension by massive weights at shaft bottom called cheese weights (because of their resemblance to a truckle or wheel of cheese) as these are easier to maintain and replace.

The largest compartment is typically used for the mine cage, a conveyance used for moving workers and supplies below the surface, which is suspended from the hoist on steel wire rope.

Cages may be single-, double-, or rarely triple-deck, always having multiple redundant safety systems in case of unexpected failure.

An additional compartment houses mine services such as high voltage cables and pipes for transfer of water, compressed air or diesel fuel.

Where this is the case a steel or concrete wall called a brattice is installed between the two compartments to separate the air flow.

With the advancements made in raise boring technology, raise borers have been used to create a pilot hole for shaft sinking, where access exists at the bottom of the new shaft, in this case the sinking phase is dedicated to enlarging this pilot hole to full diameter (a process usually called "slashing").