The path of mines – from skewers to robot arms

HISTORY OF TECHNOLOGY. From skewers, shovels and wheelbarrows, to remote-controlled loaders and robot arms that themselves calculate where the blast holes are to be drilled. Mining has been a cornerstone of Swedish business since the Middle Ages, but is constantly changing.

“Anyone who has not seen Stora Kopparberget has not seen Sweden.” This is a saying that is sometimes attributed to Carl von Linné, but which was probably old already in his time. Regardless of who coined the term, it says something about the historical significance of the mining industry for our country.

From time immemorial, the northerners had produced iron from bog ore and red soil: deposits in ferrous water, which were simply fished up with nets from the marshes or dug up as rust-red sludge by the watercourses. But most recently in the 11th century, mining of underground ore resources began in Falun and on Utö in the Stockholm archipelago.

During the Middle Ages, more and more mines were started in Dalarna and the surrounding area, such as in Garpenberg and Norberg. Early mining was carried out in rock types, ie groups of farmers who, in addition to agriculture, engaged in mining. From here comes the geographical term Bergslagen, the area in Central Sweden that constitutes the Swedish core area of ​​historic mining. To date, almost 3,000 large and small mines have arisen and disappeared in the country, most of them within Bergslagen.

Mining was conducted according to two methods. Where the rock was unusually easily broken, iron wedges could simply be driven into cracks and crevices, so-called cold wedging, but the dominant technique was called firing or firing. This meant that the rock was heated with fire so that it expanded and burst from the tensions that arose, after which it could be broken with picks and skewers.

And firing was an art that required skilled professionals. The wood was stacked in so-called lichens, arranged so that the flames stroked over the rock section you wanted to break, and in such a way that you got a strong pull through the wood.

Went to huge amounts of wood

To break horizontally, the lichen was often built three meters high at the wall of the mine tunnel. When you wanted to break upwards, the lichen was placed on top of a pile of stones or other elevation so that the flames would iron the roof as efficiently as possible, but most difficult of all was to lower the shaft downwards. Then a lying lava was created, where the wood was stacked crosswise in a low pyramid. This must be covered with stones so that the heat is pressed down, while the draft must not be hindered.

The breaking of the fire was extremely slow compared to today’s methods. Modern reconstructions have shown that the lichen must burn for at least six hours to give a good effect, and that it is best to break a few decimeters forward after each firing.

In addition, enormous amounts of wood were used, as it was barely possible to extract half a cubic meter of excavated rock per cubic meter of wood. The areas around the mines were periodically completely clear-cut, and there was often a shortage of wood for building timber. But firing and cold wedging were the predominant methods until gunpowder began to become common in the 18th century.

The first technical changes did not come in the mining itself, but in the bilge pumping. During the late 16th century, the “water art” or “art course” was introduced from Germany, with a paddle-mounted water wheel at ground level. This drove reciprocating horizontal rods, which in turn each drove their vertical rod via a shaft located at the mine mouth. As a result, the vertical rods moved up and down the mine shaft, in a piston movement that could be used to propel water.

The transmission losses in the system were very large, so the water wheel must be placed as close to the mine as possible. This meant that it was often necessary to lead driving water to the wheel through gutters and ditches, and in addition it often happened that the friction caused the rods and axles to start burning.

During the 17th century, however, Christopher Polhem, called “the father of Swedish mechanics”, succeeded in significantly improving the construction. One of his art passages, at Humberg’s mine in southern Dalarna, could effectively transfer hydropower several kilometers through rugged terrain.

But Christopher Polhem had more ideas about how mining could be improved. As master of art – a title roughly equivalent to today’s head of technology – at the Falu copper mine, he constructed a quarry for ore, based on the principle of art. Ore-loaded barrels were hung with hooks at the vertical bars that moved up and down the mine shaft, and “climbed” upwards by alternately moving from one bar to the other. At ground level, they were automatically unloaded by unfolding the bottom of the barrel.

Most often, however, the unloading was manual well into the 19th century. In some mines, the ore was carried on hand-loaded stretchers, but where the ground allowed, wheelbarrows or in some cases horse-drawn carriages were used.

And quarrying was still carried out with the firing method, despite the fact that the Sala silver mine began experimenting with powder blasting as early as the 1630s. But gunpowder was difficult to handle in the humid underground environment, and gave a difficult-to-control detonation. In addition, a new laborious task was added: the gunpowder must be placed in holes to obtain explosive power. The holes were drilled by hand with a sledgehammer and so-called navare, a rough octagonal drill with a chisel insert.

Therefore, the gunpowder was used for a long time mainly for special assignments such as shaft lowering or to open passages between existing rock chambers, and did not become common until the 18th century. In some mines, the firing method continued to be used until the second half of the 19th century, when more efficient explosives such as nitroglycerin and dynamite replaced gunpowder. And even then, the nitroglycerin had to be renamed “explosive oil” in order for it to be accepted by the miners, who thought that the chemical name sounded too abstract.

New method in place

Now a new method called roof breaking with clogging was introduced, which is still used today. This means that you work your way from the bottom up, while filling with gray rock (stone without extractable ore content) underneath to get a suitable working height in the mining room. Soon came the so-called reservoir mining, where you leave the ore itself as a “floor” in the mining room and unload at the same rate as you work your way up.

At this time also came the breakthrough of the railway, which gave the opportunity to exploit the huge deposits in Norrland. The ore line reached Gällivare in 1888 and Kiruna in 1899, and today’s Swedish mining industry began to take shape. Under the newly formed Luossavaara-Kiirunavaara Aktiebolag (LKAB), ore mining began on a scale that ancient miners could never dream of. For example, the mine in Malmberget delivered 20,000 tonnes of ore in the first year of operation – already five years later, more than half a million tonnes were mined.

The reason is of course spelled mechanization, with the pneumatic rock drill as one of the main breakthroughs during the early 20th century. It required two men to move, a whole wagon full of drill rods had to be towed, and it had to be mounted on a stand to be used, but it was much more efficient than a sledgehammer and hand drill.

The introduction of compressed air also meant that a new power source was also obtained for loading, and soon AB Atlas – now Atlas Copco – began to develop the rail-borne throwing loader. It resembled a small locomotive with a bucket, which was pushed into the ore and filled up. With compressed air operation, the bucket was then lifted up and back and emptied into an ore wagon. When the wagon was full, it was pushed by hand to the other wagons, which were then pulled out by a small low-built mining locomotive.

The locomotives were also operated in many cases with compressed air, to avoid exhaust fumes in the mine tunnels, but there were also diesel locomotives and electric locomotives that ran on an accumulator battery or were fed via a overhead contact line. Rubber-bearing loaders were also manufactured with their own load basket, which could transport mountains for shorter distances.

Swedish engineering companies became major suppliers to the mining industry, both within Sweden and globally. The pneumatic drill was further developed into a lighter machine that could be handled by a single man, who with the help of a “knee” on the drill could feed it forward. Now a lone miner could drill for a whole burst of explosives with only three drill rods.

In combination with carbide inserts from Sandvik, Atlas Copco’s “knee-fed” single-man drill was spread to mines in other countries under the name “The Swedish model”.

The mechanization improved both the working environment and profitability, but competed with many smaller mines that could not afford the investments. At the end of the 1910s, Sweden had almost 500 mines, which in total produced almost eight million tonnes of ore. Half a century later, there were only about 100 left, but the efficiencies had meant that the total production was about 20 million tons.

But the development does not stop. In the 1960s, the pneumatic throwing loaders began to be replaced by rubber-driven, diesel-powered loaders with increasing capacity. The dynamite has long been replaced by emulsion explosives, and the hand-held compressed air drills by drilling rigs with several “arms”, which can drill up to four explosive holes simultaneously.

Diesel engines are now starting to compete with electric power, and more and more mining machines are remotely controlled from control rooms at a safe distance from explosive gases and mining. At the time of writing, Epiroc, a spin-off from Atlas Copco, is experimenting with artificial intelligence in a drilling rig that will allow the drilling arms themselves to judge where the blast holes should be placed.

And the Swedish mines have continued to become fewer and larger. Including open-pit opencast mines, there are currently twelve in operation, and in total they mine almost 90 million tonnes of metal ores per year.

Falu copper mine – a thousand years underground

In the Falu copper mine, mining began in the Viking Age. It was in operation until the 1990s.

It is said that the copper ore was found by a Viking-era farmer, who noticed that his goat got reddish horns when it scrubbed against rocks on the edge of the pastures. But no one knows for sure.

Archaeological research shows that the Falu copper mine began to be mined in the 11th century, probably several hundred years earlier. The oldest known documents concerning the mine are from 1288, and even then it is mentioned as very old.

Mining was originally conducted in the form of a company, where shares in the mine could be bought and sold. But in the 14th century, the so-called rock shelf was introduced, which meant that the ore was owned by the king and that the miners paid a fee for the mining right. This was a good source of income for the royal family, as the Falu mine during the Middle Ages accounted for two thirds of all of Europe’s copper production.

The real heyday, however, came in the 17th century, when, under the guidance of German experts, innovations such as horsewinds, pedal wheels and art courses for ore soldering and bilge pumping were introduced. The mine was the most technically advanced in Europe at this time, and also Sweden’s largest workplace with over 1,000 miners.

But then came the landslide, in the literal sense. On the eve of Midsummer 1687, the rumbling of omens began in the mountain, and in the evening, three large open pits collapsed into one. The roar was heard for miles around, and when the dust settled, a 100-meter-deep pit, 300 to 400 meters in diameter, was visible. The huge hole is still there today and has been named Stora Stöten.

Copper mining never fully recovered, but would continue for another 345 years. The last ointment was fired on December 8, 1992, and an (at least) thousand-year-old epoch went into the grave.

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