Portland Stone is a limestone from the Tithonian stage of the Jurassic period unearthed on the Isle of Portland, Dorset. Mining consists of a white-and-gray limestone bed separated by a bed. It has been used extensively as a building stone throughout the British Isles, especially in major public buildings in London such as St Paul's Cathedral and Buckingham Palace. The Portland Rock is also exported to many countries - Portland stones are used at UN headquarters in New York City, for example.
Video Portland stone
Geology
Portland stones are formed in marine environments, on shallow, warm, sub-tropical sea floors probably near land (as evidenced by unusual fossilized driftwood). When sea water is warmed by the sun, its capacity to withstand dissolved gases is reduced, consequently dissolved carbon dioxide (CO 2 ) is released into the atmosphere as a gas. The calcium and bicarbonate ions in water can then combine, to form calcium carbonate (CaCO 3 ) as a precipitate. The process of making lime in a kettle in hard water areas is also the same. Calcium carbonate is the main constituent of most limestone. Billions of mined crystals of calcium carbonate deposits (called calcite) accumulate to form lime slurry (called micrite) that covers the ocean floor. Small particles of sand or organic detritus, such as shell fragments, form a nucleus, which is then coated with a calcite layer when rolled in a muddy micrite.
Calcite accumulates gradually (with accretion) around the shell fragments in concentric layers, forming small balls (diameter less than 0.5 mm). This process is similar to the way in which snowball grows in size as it rolls around in the snow. Over time, countless billions of these balls, known as "ooids" or "ooliths" (from Greek for "egg-shaped" or "stone-egg"), are partially cemented together (or settled) by more calcite , to form the oolitic limestone that we now call the Portland rock. Fortunately, the level of cementation in Portland stone is such that the stone is sufficiently cemented so well that it is possible to withstand weathering, but not so well cemented so that it can not be easily worked (cut and carved) by masons. This is one of the reasons why Portland stone is so favored as a monumental stone and architecture. Dr Geoff Townson conducted a three-year doctoral study in Portland, being the first to describe the patch-coral facies and the detail of Dorset sedimentation. Dr Ian West from the School of Ocean and Earth Sciences at Southampton University completed a detailed geological survey of Withies Croft Quarry before the Portland Bed excavated by Albion Stone plc.
Maps Portland stone
History
Stone has been excavated in Portland since Roman times and sent to London in the 14th century. Extraction as an industry began in the early 17th century, with deliveries to London for Banqueting House Inigo Jones. Wren's choice of Portland for the new St Paul's Cathedral was a great boost for mining and established Portland as London's choice for building stones. The island is connected with trains to the whole country from 1865. Albion Stone PLC has been mining and mining Portland rock since 1984. Portland Stone Firms Ltd has been pouring Portland stone since 1994.
Quarry and mine
Jordans is part of the Inmosthay Quarry in the center of the island, which also includes Fancy Beach. Mining has been working since the late 19th century. Albion Stone leased the southern part of The Crown Estate and purchased the northern part of the site in 2006. Most of the southern reserve is located underground in the local cricket club. To avoid disrupting the site at the surface level, the company has applied and received permission to extract stones using mining techniques rather than mining. Reserve in the north will be excavated using a diamond bladed cutting machine, a hydro bag and a wire saw to form blocks. This process avoids the use of dusty and noisy explosions as a major method of extraction, thereby protecting the surrounding environment, which has been designated as a Site of Special Scientific Interest (SSSI). Albion Stone PLC is now extracting all of their rocks through mining that dramatically reduces the impact on the local environment and shelter. Jordan's Mine is currently the largest mine in Portland.
Bowers Quarry has been operating since the late 18th century. It has been hired from The Crown Estate since 1979, and in 2002 became the site of the first Portland stone mine by Albion Stone PLC. The extraction from the site is now entirely underground, with the original Bower Mine at the extreme south end of the mine and the High Wall Extraction to the east and south east border. High Wall Extraction is a series of small mines that extract accidentally removed stones between the final surface of the mine and the actual site boundary.
Stonehills Mine is the first new mine in Portland (not a mine as an extension of the existing mine). Albion Stone Plc begins the process of opening the mine beginning in 2015 and the reserves are expected to last for 50 years (2066).
Coombefield Quarry, located near Southwell has been excavated openly for the past 80 years and is one of three privately owned mines by Portland Stone Firms Ltd, the island's largest landowner. Mining is nearing the end of its life and will be regenerated as a holiday caravan park to boost local tourism on the Island.
Perryfield Quarry is found in the center of the island and is actively cast cast openly. There are over 20 years of reserves left privately owned by Portland Stone Firms. Open cast quarrying provides faster raw stone block dimension extraction while maintaining its integrity. The majority of buildings in London today use Portland that has been excavated using the same method for the last 60 years.
Broadcroft Quarry is located on the east side of the island and is part of the open cast mine used for St. Paul's Cathedral. Personally by Portland Stone Firms Limited there is more than 20 years of reserves left and still excavated actively.
The coastline to the southern tip of the Island has permission to be undertaken by Portland Stone Companies and will provide more than 30 years of reserves. Permission has been granted for this to be an open cast cast.
Once mining has been done, they are then restored. The Portland Sculpture and Quarry Trust was formed in 1983 and is dedicated to preserving knowledge and understanding of the rocks and landscapes from which it came. The main mine that does not work is Tout Quarry which is where Trust stands, where workshops are used every year. Tout Quarry has been donated to Portland Sculpture and Quarry Trust by Portland Stone Firms Limited.
Excavation method
Traditional small diameter holes (35 mm) were drilled horizontally beneath each stone and filled with a small amount of gunpowder, chosen for their relatively ineffectual nature. When firing gunpowder produces a "blow" that pulls the rock out of its natural bed, hopefully it does not break. Stones are cut using spark plugs and feathers, in which a series of short, small diameter (usually 30 mm) holes are drilled in the line where pieces are to be made. One plug and two feathers are inserted into each hole and each plug is struck alternately with a sledgehammer until the rock produces the resulting extreme tensile stress. Most rocks are often weaker in tension than compression, spark plugs and feathers make use of this fact. It should also be noted that rocks tend to divide much more easily parallel to the bedding plane (called lattice) than perpendicular to them (called cuts).
In 1999, the Italian stone cutting equipment, originally designed for use in the Tuscany marble mines was imported by Albion Stone and applied to the extraction of Portland stones. This new technology eliminates the need for blasting, which significantly improves the environmental performance of the mine and eliminates the potential damage that may occur to rocks excavated through shocks. Complete accounts of local merged patterns are created when deciding positions and cutting orientations. Once the digging face has been cut, the stone is slowly displaced hydraulically. This is done using a "thin, flat, steel bag or envelope bag that, when pumped with water under moderate pressure, is able to produce the force required to loosen the rock to the point where it can be easily removed using a large wheel loader. Separating stones, using pneumatic exercises is a tough job and therefore wire saws have been put into mines, replacing many plugs and cutting feathers.
Mine
Mining in Portland is done using space and pillar methods. This mine is advanced by extracting stones using abrasive chain cutter mounted on the machine. Slots are cut to the top, bottom, side, and center of the rock. A flat steel cushion is inserted into the middle piece and slowly pumped with water. The stones are gently broken in the back without putting pressure on the resulting beams. This method of extraction is significantly more expensive than blasting, but yields higher yields thus saving valuable reserves for future generations. Environmental benefits are enormous because mining significantly reduces the impact on wildlife and local communities by reducing noise and dust.
Independent & amp; Admiralty Quarries
Both mines are owned by The Crown Estate and have been leased since 1982. This mine has been working since the mid-19th century with the last dimensional stone out of Independence in 2006, although some Portland stone block shares remain.
Once mining has been done, they are then restored. The Portland Sculpture and Quarry Trust was formed in 1983. Trust is dedicated to preserving knowledge and understanding of the rocks and landscapes from which it came.
Portland stone building
Portland limestone has almost certainly been used as a building material since Roman times. Many well-crafted Roman sarcophagi (matching stone coffins and lids, carved from large Portland stone blocks) that have been excavated locally for years, testify to the skill of its makers.
The earliest known building to build on Portland stone is Rufus Castle at Church Ope Cove, Portland. The original structure may have been built around 1080, rebuilt around 1259 and rebuilt around 1450, which is the likely date of the wall seen today. The first known Portland rock mines are located on the north-east coast of the Isle, close to Rufus Castle, where large landslides make the stone more accessible, and the proximity of the sea allows rock blocks to be excavated to move over relatively large distances. by barge.
The Portland Stone was used to build the Westminster Palace in 1347, the Tower of London in 1349 and the first stone London Bridge in 1350. Exeter Cathedral and the Christchurch Priory, also built in the 14th century built of Portland stone. Its extraordinary characteristics have gained popularity among the masons and architects who have survived since then. The East side of Buckingham Palace, the official residence of London Queen Elizabeth II, includes a balcony, faced with Portland stone, first in 1854 and again in 1913. Victoria Memorial is also made of it.
Inigo Jones (1573-1652) used the Portland Stone to build Banqueting Hall in Whitehall in 1620. Sir Christopher Wren used nearly one million cubic feet to rebuild St. Joseph's Cathedral. Paul and many other small churches after the Great Fire of London in 1666. All the stones used by Wren were transported by barges sailing from Portland to central London via the Thames River. Wide rituals use Portland stone, strongly establishing it as a "local rock" of London and as one of Britain's most beloved building stones. Other notable London buildings built from Portland stones are The British Museum (1753), Somerset House (1792), General Post Office (1829), British Bank, Mansion Mansion and National Gallery. The Portland Stone was used in 1923 to build a supporting pillar of Grace Gates in Lord's Cricket Ground.
Portland stones are prevalent in Manchester despite the historically favored use of harsh materials, such as Burmantofts and sandstone to withstand harsh industrial environments. Portland stones were mostly used in Manchester during the 1930s. Manchester buildings with Portland stone exteriors include 100 King Street (1935), Arkwright House (1937), St. James Buildings (1912), Manchester Central Library (1934), Kendal Milne (1939) and Sunlight House (1932).
Two of Liverpool's Three Graces, the Cunard Building and Port of Liverpool Building, are lined with Portland rocks that surround their reinforced concrete frames.
The Nottingham Council House, completed in 1929, was also built with Portland stones, as were public buildings in Cardiff's civilian center. Architect Charles Holden significantly used the stone in its main commissions in the 1920s and 1930s, including the Senate House and 55 Broadway, the home of the London Underground. The 1929 steel-framed building (one of the first established in the UK) of the London School of Hygiene & amp; Tropical Drugs, based in Keppel Street, owns the Portland façade stone to complete a stripped classic design. After World War II (1939-1945), bombed city centers and major cities such as Plymouth, Bristol, Coventry and London were reconstructed using the vast Portland stone facade.
Many of the buildings around the Parkinson's main building at Leeds University are wrapped in Portland rocks, including Michael Sadler's Building, Chemical and Engineering buildings, and the new Laidlaw Library.
Although Oxford typically uses oolitic limestone in its buildings, the Ashmolean Museum has been refurbished using a large number of Portland stones.
The Portland Stone has also been used worldwide. Examples include the United Nations building in New York, the Kursaal Casino in Belgium, and the Auckland War Memorial Museum. Most of the important civilian and administrative buildings that survived the 18th and 19th centuries of Dublin, Ireland, which came to be known as the "second city of the Empire", were of Portland stone, including City Hall (1779), Parliament House (1767), Custom House (1779) 1791), National Gallery (1864) and General Post Office (1818). More recent projects include BBC Broadcasting House in London, which won the "New Build (Modern Non-Load-bearing Stone) Award" in the 2006 Natural Stone Awards.
fauna Vertebrata
Sumber:
Ornithischian
Saurischian
Pergantian
Portland Stone is known for high quality, but rather expensive. Substitutions are known to have occurred, using similar oolitic limestone from other sources.
Cement
The term "Portland cement" was coined by Joseph Aspdin who in 1824 patented a hydraulic binder made by burning a mixture of limestone and clay, resembling previous Roman cement and presenting the material he expected to look like a famous Portland stone building.
See also
- List of stones
- List of limestone types
References
Further reading
- Hackman, Gill (2014). The Rock to Build London: The Heritage of Portland . Monkton Farleigh, Wilts: Folly Books. ISBN 978-0-9564405-9-4. OCLCÃ, 910854593.
- Stuart Morris, 2016 Portland, Picture History The Dovecote Press, Wimborne, Dorset: ISBNÃ, 978-0-9955462-0-2
External links
- Jurassic Coastal Geology
- Marking Godden's features in Today's Geology [1]
Source of the article : Wikipedia
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