June/July 2008

History of Mining

The evolution of shaft sinking systems (Part 7)

By C. Graham and V. Evans

1600 A.D. to the present — a summary

Primitive shaft sinkers used their hands and implements of bone, wood and, later, metal to dig the shafts that were necessary to remove the minerals required in their society. With the arrival of a social system, under the Egyptians and the Phoenicians, shaft sinking and mining became more organized, with slaves, criminals and prisoners of war being utilized. In these early days, fire quenching was utilized along with wedges and hammers to break up the rock, which was then removed in baskets.

With the coming of the Middle Ages, mining and shaft sinking alike became a respected profession; however, mining techniques remained much the same as those used under the Romans. The first major change in shaft sinking practice was the use of black powder rather than fire quenching to break the rock, which occurred in the 17th century. The Industrial Revolution brought about the next major changes — steam-powered hoists and pumps. In the 19th century, the pneumatic rock drill replaced drilling by hand and in the mid-20th century, mechanical mucking machines replaced hand mucking. All these changes, although slow in coming, drastically increased the speed of shaft sinking.

Summarizing the average sinking speeds from the various periods clearly illustrates the changes in technology over time and the resulting increase in sinking rates.

  • Prior to 1600 AD — 1 to 1.2 metres per month
  • 1600 to 1800 AD — 3 to 4 metres per month (three-fold increase)
  • 1800 to 1900 AD — 10 to 12 metres per month (three-fold increase)
  • 1900 to 1940 AD — 30 to 40 metres per month (three-fold increase)
  • 1940 to 1970 AD — 90 to 110 metres per month (three-fold increase)
  • 1970 to 2007 AD — 90 to 110 metres per month (0 increase)

Prior to 1600 AD

The sinking of shafts had been going on for thousands of years prior to 1600. The Egyptians mined gold extensively in eastern Egypt and Sudan as far back as 2000 BC and sank shallow shafts to access the majority of this gold. It is thought that it was from the Egyptians that the Persians, Greeks and Romans learned their mining and shaft sinking techniques. Besides iron tools, the Romans used fire to fracture the rock. Pliny mentions breaking up the rock by means of fire and vinegar. Other Roman authors, such as Livy and Vitruvius, mention fire setting and vinegar as well.

A summary of the sinking system of 1600:

  • Excavation using fire setting and primitive tools
  • Hand mucking to small wooden buckets
  • Hoisting material with man-powered windlass
  • Rectangular or square shafts with wooden shaft linings
  • Temporary ground support consisting of platforms in the shaft every few metres
  • Crude ventilation or none at all
  • Water handling with buckets or other inefficient devices

The big change that occurred in this period was the status of the miners and shaft sinkers. In Egyptian and Roman times, miners and shaft sinkers were generally slaves, criminals or prisoners of war. By the early part of the 12th century, the shaft sinker and the miner were considered to be tradesmen and were much in demand. Personnel involved in the mining trade were freed from paying certain taxes, were allowed to carry arms and did not have to serve as soldiers. They were also free to choose the mine where they preferred to work. Although the status of the shaft sinker and miner alike changed drastically during this period, the techniques used for sinking shafts had changed very little from Roman times.

1600 to 1800

In Cornwall in the late 1700s, there was considerable advancement in mining techniques as deeper workings led to the greater use of steam power for hoisting and pumping. The use of steam power in shaft sinking, however, was much more pronounced after 1800.

It would also appear that it was during the 1700s that shaft sinking came to be considered a separate occupation from mining.

Improvements to the sinking system during the period were:

  • Hand drilling of drill holes
  • Blasting with black powder
  • Larger muck buckets
  • Hoisting utilizing horse whims
  • Faster water handling with buckets using horse whims

1800 to 1900

The invention of the steam engine in the late 18th century was very important to both miners and shaft sinkers. This invention translated into two very important pieces of equipment for the shaft sinking fraternity: steam-powered mine hoists and steam-powered mine pumps. Both of these inventions were pioneered in Cornwall. The Cornish steam-powered pumps and hoists were exported all over the world.

During the reign of the Tudors in England, Saxon technicians taught Cornishmen shaft sinking techniques employed in their native Saxony. These techniques were utilized to access Cornwall’s extensive tin and copper deposits and for the next two centuries, England had a virtual monopoly on these two essential minerals.

Beginning about 1840, and repeated in 1865, Cornish mining prosperity slumped drastically for a number of technical and financial reasons. The discovery of rich overseas copper deposits was the main problem, worsened by a degree of mismanagement in the Cornish mines. This situation caused many of the mines to close, throwing thousands of shaft sinkers and miners out of work. Cornish workers moved to North America, Australia and South Africa to ply their trade. Many of the shafts sunk during this period were sunk by Cornish men or “Cousin Jacks” as they were called.

Improvements to the sinking system during the period:

  • Mechanical drilling with large drills powered by compressed air
  • Blasting with dynamite and safety fuse
  • Hand mucking to buckets or skips
  • Circular shafts with brick lining utilized in poor ground
  • Hoisting men and material with steam-powered hoists
  • Wire hoist rope replaced the hemp hoist ropes
  • Ventilation using steam-powered centrifugal fans
  • Water handling with steam-powered pumps
  • Kind-Chaudron system of shaft drilling for sinking in high water-bearing ground
  • Poetsch system for the use of the freezing technique in sinking through high water-bearing ground

 

1900 to 1940

During this period in North America, shafts were almost all rectangular and timber-lined, while in Europe, nearly all were circular and lined with brickwork.

The introduction of electrical power to mines at the beginning of the 20th century had a great impact on shaft sinking practice. By the start of the Great Depression, miners and shaft sinkers alike celebrated the industry’s embrace of the electrical mine hoist for most types of shaft work.

Improvements to the sinking system during the period:

  • The use of light, handheld “plugger” drills rather than heavy drills mounted on some type of support
  • Blasting with electrical detonators rather than fuses
  • Temporary wall support with rock bolts
  • Ventilation using axial fans
  • Water handling with electric pumps

1940 to 1970

It was during this period that the South Africans developed their sinking system that incorporated the suspended curb ring and a multi-deck Gallaway work stage. This allowed for the installation of a concrete lining at the same time as excavation was being carried out on the shaft bottom below. This type of equipment was also adopted by both Canada and the United States, as well as some western European shaft sinkers, although concurrent concreting was not always carried out.

The mechanized loading of broken muck from the shaft bottom was also introduced during this period. In South Africa and Europe, the Cactus Grab mucking machine was adopted for shaft mucking. In the United States, the Eimco 630 loader was the most popular, while in Canada the Cryderman mucker became the most popular mucking machine.

Improvements to the sinking system during the period:

  • Introduction of pneumatic drill jumbos for drilling
  • Mechanical mucking machines
  • Suspended concrete forms and multi-deck work platforms for concreting
  • Concrete slick lines for lowering of concrete in the shaft

1970 to 2007

Although hydraulically powered drills had been used in the tunnelling industry since the 1970s, it took most shaft sinkers until the late 1980s to start using hydraulically powered drills mounted on drill jumbos.

In Canada, the “Long Round” system of shaft drilling was adopted in the late 1980s and early 1990s. This system utilizes a drill jumbo that is suspended from the sinking stage rather than sitting on the shaft bottom. This type of jumbo drills a “burn cut” rather than the “V-cut” that is usual in shaft sinking.

Very recently in Canada, a project was carried out where the shaft sinker was successfully able to equip the shaft concurrent with sinking operations being carried out on the shaft bottom below. This is certainly a major achievement and should bring about an increase in shaft sinking advance rates in the order of 25 per cent.

It was during this period that a number of attempts were made to speed up shaft sinking by mechanizing it, as with the case of the tunnel boring machine in the tunnelling industry. Perhaps the most successful example of this is the Wirth V-mole. Although bottom access to the shaft is required and the machine is really a shaft enlarger rather than a shaft sinker, it has functioned relatively well on a number of projects.
In addition to the Wirth V-mole, large-hole drilling, based on petroleum technology, is used to drill relatively small ventilation shafts in moderately hard ground.

Improvements to the sinking system during the period:

  • Drilling with hydraulically powered drill jumbos
  • Blasting with electronic detonators and bulk explosives
  • Shaft equipping concurrent with excavation
  • Development of the Wirth V-mole
  • Development of large-diameter drilling techniques for relatively small shafts

Summary

At the present time, average sinking rates around the world do not vary a great deal. If an average of 3 metres of completely equipped shaft can be attained, this is probably considered to be an excellent sinking rate in any country in the world.

The excavation of tunnels has seen a huge change in technology in recent years with the invention of the tunnel boring machine. Whether a similar change will be seen in shaft sinking techniques in years to come is difficult to forecast.

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