shaft sinking

Shaft sinking is a method of underground excavation primarily used in mining for accessing ore, ventilation, and material transport. These shafts are essentially vertical tunnels, often reaching depths of several thousand feet.1

Shaft Sinking Methods

• In Soil: Methods include using interlocking steel sheetpiling, concrete caissons sunk from the surface, or the slurry trench method where a trench is excavated and filled with a heavy liquid to support the walls until concrete is poured. For deeper soil shafts, freezing the soil around the shaft can provide temporary support.1
• In Rock: More efficient methods for deep shafts in rock, developed in South Africa, involve drilling and blasting, with concurrent excavation and concrete lining. Progress can be around 30 feet per day.1
• Drilling Methods: Techniques adapted from oil-well drilling, known as big-hole drilling, are used for constructing shafts, especially for smaller diameters. These methods can achieve significant depths and progress rates.1

Shafts can also be "raised" from an existing tunnel below, which simplifies cutting removal. The development of the raise borer in the 1960s significantly improved the efficiency and reduced the cost of shaft raising. Early shaft mines were often simple wells, with depth limited by the ability to remove water, a problem later addressed by steam engines.23