Mine shafts were dug using either conventional drill and blast methods or mechanized means.
Historically, the sinking of mine shafts was one of the most hazardous mining jobs, typically handled by specialized mining contractors known as "sinkers." The specific techniques evolved over time, but the fundamental principle remained the same: creating a vertical or near-vertical access point into the earth.
Methods of Mine Shaft Excavation
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Conventional Drill and Blast:
- Drilling: Holes were drilled into the rock face using pneumatic drills or, historically, hand drills.
- Charging: Explosives (dynamite or other blasting agents) were placed into the drilled holes.
- Blasting: The explosives were detonated, breaking the rock.
- Mucking: The broken rock (muck) was removed from the shaft using various methods, including buckets, skips (large containers), or conveyor systems.
- Support: As the shaft deepened, support structures, such as timber, concrete, or steel sets, were installed to prevent collapse.
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Mechanized Shaft Sinking:
- This method utilizes specialized machinery to excavate and support the shaft. Examples include:
- Shaft Boring Machines (SBMs): These massive machines bore a full-face circular shaft in a single pass. They are particularly effective in soft rock or soil.
- Roadheaders: These machines use a rotating cutting head to excavate rock. They are more flexible than SBMs and can be used in a wider range of rock conditions.
- Raise Borers: Although technically used to create raises (vertical or near-vertical openings driven upwards from an existing underground opening), raise boring technology can be adapted for shaft sinking in certain applications.
Historical Significance of Sinkers
The "sinkers" were a specialized group of miners who possessed the skills and experience necessary to safely and efficiently excavate mine shafts. They often worked on contract and moved from mine to mine, taking on the dangerous task of creating these essential access points. Their work involved a high degree of risk due to the potential for rock falls, explosions, and flooding.
Shaft Support and Lining
Regardless of the excavation method, proper shaft support and lining are critical to ensure the long-term stability and safety of the mine shaft. Common lining materials include:
- Timber: Historically used, but less common today due to its susceptibility to rot and fire.
- Concrete: A durable and versatile lining material that can be cast in place or precast into segments.
- Steel: Steel sets or liners provide high strength and are often used in areas with unstable ground conditions.
