What Is a Mine Shaft? | An Underground Miner

If you've spent any time adjacent to the mining industry, you've likely heard the term "mineshaft" before.

Laypeople often use the word to refer to any underground tunnel used for mining; however, this usage isn't strictly accurate.

So what is a mine shaft?

Keep reading to learn all about this unique and daring excavation operation.

Shaft mining is an excavation method used to access an underground ore body from the top down.

The term "shaft" refers to the vertical tunnels sunk underground for mining and engineering projects.

When the opening starts on the surface, the resulting tunnel is called a shaft.

If the vertical tunnel starts underground and pushes upward, it's called a sub-shaft.

The depth varies depending on the project. Civil engineers usually create shallow shafts for public projects like sewer tunnels.

Shafts of greater depth are sunk to access underground ore deposits.

Sinking is the process of excavating a mining shaft.

It's commonly considered one of the most challenging and dangerous mining techniques in existence, although modern developments and mechanization aim to address these difficulties.

Shafts provide access to ore and are dug for ventilation and to ensure the proper flow of air throughout an existing mine.

Mine shafts can also be dug for storage. Compressed air, water, and fuel may be stashed in an empty shaft compartment for easy access in the event of an emergency.

Boreholes are small shafts raised from the bottom upward. "Borehole" refers to the fact that the rock or earth is bored to create the opening.

Here are the major components that make up a shaft mine.

Equipment on the ground surface is covered by a building referred to as the "head frame."

Within this building, you'll typically find a sheave wheel or hoist motor that lifts loads of ore through the shaft and storage bins to contain ore and other materials until they can be transported to another facility.

Beneath these facilities is the collar, a massive support structure made of reinforced concrete.

Shaft lining provides several important safety functions within the mine. Its smooth surface improves ventilation and air flow.

It also prevents loose earth, rocks, and other material from falling down the shaft.

Shaft lining may be used when boring through soft earth and rock to provide support to the shaft.

The shape of the shaft and the ground conditions around the mine will determine whether or not a liner is used.

The square-shaped, smaller shafts used in North and South America frequently go without lining, while larger, circular shafts typically have a shaft lining made of concrete.

During ground support installation on the surface, a temporary lining of shotcrete may be installed through robotic application.

The multiple compartments of a mine shaft are called shaft sets.

These sets are usually made of steel and are made up of horizontal members called buntons and vertical members called guides.

Steel shaft guides come in two varieties: hollow structural sections and top hat sections.

Top hats are preferred because they have increased stiffness over hollow sections and a simpler installation process.

They also make use of wire ropes rather than steel guide beams, which are more flexible and easier to replace.

The largest compartment in a shaft mine is typically used for moving workers, heavy equipment, and loads of ore.

Miners descend and ascend through the shaft in a mine cage, which is similar to an elevator you'd find in a skyscraper.

These cages are equipped with multiple safety systems to ensure workers can be safely evacuated in case of unexpected failure.

Horizontal tunnels, called drifts, are used for drainage in shaft mining.

These drifts form an important part of the structure. Without proper drainage, water can well up inside the mine and damage the mining components and equipment.

The place where a shaft meets the main ore body is called the shaft station, inset, or plat.

Drifts typically fan outward from the station to facilitate movement beneath the ground.

The shaft bottom is the lowest part of the mine. It's also the most dangerous place to work, so care must be taken to ensure miners spend as little time down there as possible.

The first part of the sinking cycle is excavation. This is usually accomplished through drill and blast methods.

However, mechanization through the use of a tunnel boring machine has shown great promise and may improve the safety of this notoriously dangerous mining technique.

During the initial excavation process, temporary ground support made of rock bolts and welded mesh is put in place to help ensure miner safety.

The mesh is fashioned from tough steel wires that are resistant to corrosion and have a tensile strength between 850 and 900 pascals, strong enough to stop a bullet and prevent a knife from cutting through.

Once the appropriate depth has been reached, the lining is put in place. This adds structure to the mine and helps prevent loose dirt and rock from falling.

Finally, the rest of the mining equipment needed for the project is constructed and installed, and the temporary equipment is stripped away.

Because of the many dangers, this type of excavation poses to miners, shaft sinking is not in widespread use in most parts of the world.

Canada and South Africa are the only countries to regularly employ this mining technique.

However, vertical shafts are still dug along with drifts in other forms of mining for proper ventilation and to ensure the miners get enough air.

They are also used to raise and lower workers, equipment, and ore in and out of the mine.

If you've referred to both the vertical and horizontal components of mines as "shafts" in the past, don't feel bad!

Most people outside the mining industry aren't aware there's a difference.

Interested in learning even more about mining techniques and terminology?

An Underground Miner is your go-to source for all things excavation.

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This article was written by An Underground Miner