Adit

An adit (from Latin aditus, entrance)[1] is an entrance to an underground mine which is horizontal or nearly horizontal,[2] by which the mine can be entered, drained of water,[3] ventilated, and minerals extracted at the lowest convenient level.[1] Adits are also used to explore for mineral veins.[1]

Adit.jpeg
Gated entrance of an abandoned adit near Medford, Oregon, United States

Construction

Sztolnia Królowa Luiza EC (11)
Queen Louise adit, Zabrze, Poland

Adits are driven into the side of a hill or mountain, and are often used when an ore body is located inside the mountain but above the adjacent valley floor or coastal plain. In cases where the mineral vein outcrops at the surface, the adit may follow the lode or vein until it is worked out, in which case the adit is rarely straight. The use of adits for the extraction of ore is generally called drift mining.

Adits can only be driven into a mine where the local topography permits. There will be no opportunity to drive an adit to a mine situated on a large flat plain, for instance. Also if the ground is weak, the cost of shoring up a long adit may outweigh its possible advantages.

Access and ventilation

Nenthead Mines - geograph.org.uk - 2530761
Horse adit in the abandoned lead mine, Nenthead, County Durham, UK

Access to a mine by adit has many advantages over the vertical access shafts used in shaft mining. Less energy is required to transport miners and heavy equipment into and out of the mine. It is also much easier to bring ore or coal out of the mine. Horizontal travel by means of narrow gauge tramway or cable car is also much safer and can move more people and ore than vertical elevators. In the past horses and pit ponies were used.

In combination with shafts, adits form an important element in the ventilation of a mine: in simple terms, cool air will enter through an adit, be warmed by the higher temperature underground and will naturally exhaust from vertical shafts, some of which are sunk specifically for this purpose.[4]

Drainage

Two brothers adit entrance
A small, almost hidden adit entrance at Eylesbarrow mine, Dartmoor, Devon

Most adits are designed to slope slightly upwards from the entrance so that water will flow freely out of the mine.[5] Mines that have adits can be at least partly drained of water by gravity alone or power-assisted gravity. The depth to which a mine can be drained by gravity alone is defined by the deepest open adit which is known as the "drainage adit".[6] The term mine drainage tunnel is also common, at least in the United States. Workings above this level (known as "above adit") will remain unflooded as long as the adit does not become blocked. All mine workings below both the drainage adit ("below adit") and the water table will flood unless mechanical means are used for drainage. Until the invention of the steam engine this was the main restriction on deep mining. Adits are useful for deeper mines, as water only needs to be raised to the drainage adit rather than to the surface.

Because of the great reduction in ongoing costs that a drainage adit can provide, they have sometimes been driven for great distances for this purpose. One example is the Milwr tunnel in North Wales, which is about ten miles (16 km) long. Other examples are the Great County Adit in Cornwall, a 40-mile (65 km)-long network of adits that used to drain the whole Gwennap mining area, and the 3.9 mile (6.2 km) Sutro Tunnel at the Comstock Lode in Virginia City, Nevada. A side benefit of driving such extensive adits is that previously unknown ore-bodies can be discovered, helping finance the enormous cost.[6]

Adits were used in Cornwall before 1500, and were important to the tin and copper mines in Cornwall and Devon because the ore-bearing veins are nearly vertical, thus acting as ingress channels for water.[5]

Notable examples

  • Great County Adit, a system of over 40 miles (65 km) of adits used for dewatering the over 100 mines in the Gwennap area of Cornwall in the 18th and early 19th centuries.
  • Milwr tunnel, a 10-mile long (16 km) drainage adit in North Wales. Started in 1897, it still discharges an average of 87 million litres (23 million US gallons) of water per day from the disused Halkyn District United Mines.
  • The Snowy Hydro scheme in the Australian Snowy Mountains created during its construction. These adits are very large and used to access the central point from which the hydro tunnels were constructed.
  • Black Trout Adit in Tarnowskie Góry, Poland. It is part of a former silver mine, the adit was used for removing the water out of the mine. It still carries water from old galleries to the nearest river, a part of it is open for tourists, who go 66 feet (20 m) down the steps in one shaft, have a ride in a boat and go up the stairs in another shaft.
  • Blue Hawk Mine near Kelowna, BC, Canada.
  • NORCAT's Underground Mine Centre (Fecunis Adit), used for underground training and mining technology development in Onaping, ON, Canada.
  • Sutro Tunnel for drainage and exploitation of the Comstock Lode in Nevada.

Similar terms

  • A "drift" is a more general term for any near-horizontal underground passage in a mine. Unlike an adit, a drift need not break out to the surface. Drift mining is the use of drifts to extract ore - in this case the drifts follow the vein.
  • A "level" is a horizontal passage that branches off from a shaft and is used for access to the parts of the mine where the ore is being removed. In mines where the lodes have significant vertical extent there can be many numbered levels, one below the other. They can be connected by short vertical shafts known as "winzes". A level that reaches the surface, on a hillside or in a valley, for instance, is called an "adit level".
  • "Sough" is a term mainly used in the lead mining areas of Derbyshire. The main purpose of a sough is to drain water from the mine.

See also

Glossary of coal mining terminology

References

  1. ^ a b c Wikisource Ripley, George; Dana, Charles A., eds. (1879). "Adit" . The American Cyclopædia.
  2. ^ Paul W. Thrush, 1968, A Dictionary of Mining, Mineral, and Related Terms, US Bureau of Mines, p.12.
  3. ^ R. W. Raymond, 1881, Glossary of Mining and Metallurgical Terms, American Institute of Mining Engineers, p.3.
  4. ^ Earl 1994, pp.64–65.
  5. ^ a b Earl 1994, p.36.
  6. ^ a b "Mining Encyclopaedia (Adit, Drainage Adit, Deep Drainage)". Mine-Explorer. Retrieved 2010-12-06.

Sources

  • Earl, Bryan (1994). Cornish Mining: The Techniques of Metal Mining in the West of England, Past and Present (2nd ed.). St Austell: Cornish Hillside Publications. ISBN 0-9519419-3-3.
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Asambhav

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Beer Quarry Caves

Beer Quarry Caves is a man-made limestone underground complex located about a mile west of the village of Beer, Devon, and the main source in England for beer stone. The underground tunnels resulted from 2,000 years of quarrying beer stone, which was particularly favoured for cathedral and church features such as door and window surrounds because of its colour and workability for carving. Stone from the quarry was used in the construction of several of southern England's ancient cathedrals and a number of other important buildings as well as for many town and village churches, and for some buildings in the United States. Extraction was particularly intense during the Middle Ages, but continued until the 1920s. An adit to another set of workings can be seen from the South West Coast Path east of Branscombe, having been exposed by a landslip in the late 18th century. The quarry is part of the Jurassic Coast, and is a Site of Special Scientific Interest (SSSI).

Black Trout Adit

Black Trout Adit (Polish: Sztolnia Czarnego Pstrąga) is the longest (600 meters) underground tourist route in Poland travelled by boats. It's a part of one of 8 adits dug in the area to drain the workings. The Black Trout Adit is located in a park in the west of the town Tarnowskie Góry. Access is by two shafts Ewa and Sylwester (the traffic is alternating). The guide puts the boats in motion and tells the stories connected with the place.

Carnon River

The Carnon River is a heavily polluted river in Cornwall, England. It starts in Chacewater. Trewedna Water and River Kennall flow into the Carnon before it merges with Tallack's Creek to become Restronguet Creek, which eventually flows into the English Channel at the mouth of Carrick Roads.The Nebra sky disc, a gold-decorated bronze disc found in Germany and dated to the Bronze Age contains both gold and tin from the Carnon valley.In 1992 the river was hit by a major pollution incident, when over 45 million litres of contaminated water from the closed Wheal Jane mine was released by the collapse of an adit, colouring the river water red. A treatment works has since been installed at Wheal Jane to intercept the contaminated water and treat it to remove suspended metals and restore a neutral pH.

Conglog Slate Quarry

Conglog Slate Quarry was a small enterprise situated to the north-west of Tanygrisiau near Blaenau Ffestiniog in Wales. It was overshadowed by the much bigger Rhosydd Quarry a little further to the west. It was active from 1854 to 1910, and was operated by an individual, two partnerships and four separate companies over this period.

Croesor Quarry

Croesor Quarry is a large underground slate mine in north Wales which was served by Croesor Tramway. Small scale quarrying began in the 1840s, and by 1861, there were two companies in operation. They amalgamated in 1865, a year after the quarry was connected to the newly opened Croesor Tramway. Much money was invested in development work, but volumes of useful slate produced were small, amounting to just 226 tons in 1868. Access to the underground workings was by a single adit, and the surface mill was powered by two water wheels. A change of ownership in 1875 did little to improve the profitability of the quarry, and it closed in 1878 or 1882.

In 1895, the quarry reopened under the direction of Moses Kellow, a fearless innovator who set about modernising working practices and methods. The two-man teams working in the mill were no longer tied to a two-man team working underground, which enabled the mill to operate more efficiently. Following trials with air drills, he decided instead to electrify the mill, building a large hydro-electric station, which generated three-phase alternating current, rather than the direct current recommended by British manufacturers. He obtained motors from Prague, which were used to drive winches and an electric locomotive, the first to work in Wales. The water wheels were supplemented by Pelton wheels, supplied by Gilbert Gilkes of Kendal. His greatest innovation was the Kellow drill, a hydraulic drill for which he obtained six patents between 1898 and 1915. It could drill a 7.5-foot (2.3 m) hole in the slate in under two minutes, much less than the day required using hand drills. The mine was ventilated by a Guibal fan, housed in a fan-house near the entrance to the adit. Peak output under Kellow's direction was between 5,000 and 6,000 tons per year, though it declined in the later years, until the quarry closed in 1930.

The chambers were used by Cookes Explosives to store propellants from the late 1940s until the early 1970s. This ceased when the Central Electricity Generating Board became aware of it, and feared that an underground explosion would damage the dams of the Ffestiniog pumped storage power station. Both lakes were drained until the explosives had been removed. The quarry was worked on seven levels, but the three below the adit level are now flooded. There was an underground link to the nearby Rhosydd Quarry, and the Croesor Rhosydd Through Trip is a well known, if somewhat dangerous, route for mine explorers.

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Fatman Films

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Great County Adit

The Great County Adit, sometimes called the County Adit, or the Great Adit was a system of interconnected adits that helped drain water from the tin and copper mines in the Gwennap area of Cornwall, in the United Kingdom. Construction started in 1748 and it eventually reached a length of over 40 miles (65 km) of underground tunnel, providing drainage to over 100 mines at an average depth of 80-100m.The adit was the brainchild of John Williams (born 1714) of Scorrier who was the manager of Poldice mine. Although work was started in 1748, it did not reach Poldice mine until the late 1760s. By 1778 the adit had been extended past Wheal Busy to Wheal Peevor, and another branch, known as the Consols Adit was driven west in the 1770s and 80s to drain the Consolidated Mines and United Mines. By 1792 a branch from Poldice extended to Wheal Unity.

The portal of the adit is in the Carnon Valley below the hamlet of Twelveheads. In 1839, probably at its peak, it discharged over 14.5 million gallons (66 million litres) of water per day into the Carnon River. At that time the adit had more steam engines pumping into it than were used by the whole of continental Europe and America combined.The Carnon River empties into Restronguet Creek (a tidal arm of the Carrick Roads upstream from Falmouth). Major floods in the winter of 1876 caused large quantities of gangue and silt to be washed into the higher part of Restronguet Creek, permanently damaging navigational access to the upper quays at Devoran.Although all the mines served by the Great County Adit have closed and it is unmaintained, it still drains many of their underground workings today; in the summer of 1980 the flow was 500,000 gallons per day.

Historic Silver Mine in Tarnowskie Góry

The Historic Silver Mine, (Polish: Zabytkowa Kopalnia Srebra), is a mining museum in Tarnowskie Góry, in Silesia in Poland. The mine and the neighbouring Black Trout Adit are remnants of a silver mining industry. The museum is an Anchor point on the European Route of Industrial Heritage. It also joined The International Committee for the Conservation of the Industrial Heritage and the Silesian Tourist Organization.

Lawson Adit

The Lawson Adit is a horizontal mine tunnel, or adit, on the UC Berkeley campus, near the Hearst Mining Building, dug directly through the Hayward Fault. Started in 1916, the adit is named after Andrew Lawson, one-time Dean of the College of Mining at UC Berkeley.

Merantau

Merantau, released in some countries as Merantau Warrior, is a 2009 Indonesian martial arts action film written, directed and edited by Gareth Huw Evans, and starring Iko Uwais. The film, which marks Uwais' debut as an actor, is the first collaboration between director Evans and star Uwais. It also marks the acting debut of Yayan Ruhian, both of whom Evans met while shooting for a documentary in Indonesia which became his introduction to the Pencak Silat martial art.

The film showcases the Minangkabau tradition of "Merantau", a rite of passage where a man leaves his home to pursue a career or gain experience outside of the village, a culture where inheritance is largely matriarchal. It showcases Yuda who leaves his village in hopes of teaching Silat in Jakarta, only to be sidetracked as he attempts to save a girl from being kidnapped. The film showcases a style of Silat known as "Silek Harimau" (Tiger Silat). It also features actors Donny Alamsyah and Alex Abbad who, along with Uwais and Ruhiyan, would later appear in Evans' subsequent films in The Raid (2011) and The Raid 2 (2014).

Evans' first major feature film, Merantau premiered at the Puchon International Fantastic Film Festival in South Korea on 23 July 2009, before being released theatrically on 6 August in Indonesia. It won the Jury Award for Best Film at the inaugural 2010 ActionFest in North Carolina.

Poldice mine

Poldice mine is a former metalliferous mine located in Poldice Valley in south-west Cornwall, England, United Kingdom. It is situated near the hamlet of Todpool, between the villages of Twelveheads and St Day, three miles (5 km) east of Redruth.

Quincy and Torch Lake Cog Railway

The Quincy and Torch Lake Cog Railway is a half-mile long, 4 ft 8 1⁄2 in (1,435 mm) standard gauge cog railway in Hancock, Michigan. It opened in May 1997 to transport tourists to the adit entrance of the Quincy Mine's Number 5 shaft. Its tram car has a capacity of 28 people and travels at a maximum grade of 35%. It is one of only a few rack railways in the United States.

Speedwell Cavern

The Speedwell Cavern is one of the four show caves in Castleton, Derbyshire, England.

It consists of a horizontal lead miners' adit (a level passageway driven horizontally into the hillside) leading to the cavern itself, a limestone cave. The adit is permanently flooded, resulting in Speedwell Cavern's (locally unique) feature: after descending a long staircase, the visitor makes the journey into the cave by boat. Originally the guide propelled the boat by pushing against the walls with his hands, later the boat was legged through, and now it is powered by an electric motor.

At the end of the adit, the visitor alights from the boat and walks into the cave to see the fluorspar veins, the stalactites and stalagmites, and the so-called "Bottomless Pit". This pit is an extremely deep vertical shaft, now choked to within 20 metres (66 ft) of the surface by rock spoil dumped by miners. The original depth of the shaft has been estimated, from the amount of spoil placed in the shaft over the years, at around 150 metres (490 ft).

A connection was discovered in 1999 between the Speedwell Cavern system and Titan, the largest natural shaft in the UK, which is 141.5 metres (464 ft) high.

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