자료: Wikipedia, http://www.answers.com/topic/thames-tunnel
The Thames Tunnel is an underwater tunnel, built beneath the River Thames in London, United Kingdom connecting Rotherhithe andWapping. It measures 35 feet (11 m) wide by 20 feet (6 m) high and is 1,300 feet (396 m) long, running at a depth of 75 feet (23 m) below the river's surface (measured at high tide). It was the first tunnel known successfully to have been constructed underneath a navigable river[1], and was built between 1825 and 1843 using Marc Isambard Brunel's newly invented tunnelling shield technology, by him and his son Isambard Kingdom Brunel.
The tunnel was originally designed for, but never used by, horse-drawn carriages and was most recently used by trains of the London Underground's East London Line. The East London Line closed on 23 December 2007 to allow extension of the line and conversion of the route to become part of the London Overground network in time for 2010.
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History and development
Construction
At the start of the 19th century, there was a pressing need for a new land connection between the north and south banks of the Thames to link the expanding docks on both sides of the river. The engineer Ralph Dodd tried, but failed to build a tunnel betweenGravesend and Tilbury in 1799.[2]
In 1805-1809 a group of Cornish miners, includingRichard Trevithick, attempted to dig a tunnel further upriver between Rotherhithe and Wapping but failed because of the difficult conditions of the ground. The Cornish miners were used to hard rock and did not modify their methods for soft clay and quicksand. The "Thames Archway" project was abandoned after it caved in when 1,000 feet (305 m) of a total of 1,200 feet (366 m) had been dug.[3] However, even if it had been completed its usefulness would have been questionable; it only measured 2-3 feet by 5 feet (61-91 cm by 1.5 m), far too small for passenger use.
The failure of the Thames Archway project led engineers to conclude that "an underground tunnel is impracticable".[4] However, the Anglo-French engineer Marc Brunel refused to accept this conclusion. In 1814 he proposed to Tsar Alexander I of Russia a plan to build a tunnel under the river Neva in St Petersburg. This scheme was turned down (a bridge was built instead) but Brunel continued to develop ideas for new methods of tunnelling.[2]
Brunel and Thomas Cochrane patented the tunnelling shield, a revolutionary advance in tunnelling technology, in January 1818. In 1823 Brunel produced a plan for a tunnel between Rotherhithe and Wapping, which would be dug using his new shield. Financing was soon found from private investors including the Duke of Wellington and a Thames Tunnel Company was formed in 1824, with the project beginning in February 1825.[3]
The first step taken was the construction of a large shaft on the south bank at Rotherhithe, 150 feet (46 m) back from the river bank. It was dug by assembling an iron ring 50 feet (15 m) in diameter above ground. A brick wall 40 feet (12 m) high and 3 feet (91 cm) thick was built on top of this, with a powerful steam engine surmounting it to drive the excavation's pumps. The whole apparatus was estimated to weigh 1,000 tons.[2] The soil below the ring's sharp lower edge was removed manually by Brunel's workers. The whole shaft thus gradually sank under its own weight, slicing through the soft ground rather like an enormous pastry cutter. The shaft became stuck at one point during its sinking as the pressure of the earth around it held it firmly in position. Extra weight was required to make it continue its descent, a total of 50,000 bricks were added as temporary weights. It was realised this problem was caused because the shaft was cylindrical, years later when the Wapping shaft was built it was slightly wider at the bottom than the top. This non-cylindrical tapering design ensured it did not get stuck. By November 1825 the Rotherhithe shaft was in place and tunnelling work could begin.[3]
The tunnelling shield, built at Henry Maudslay's Lambeth works and assembled in the Rotherhithe shaft, was the key to Brunel's construction of the Thames Tunnel. The Illustrated London Newsdescribed how it worked:
| “ | The mode in which this great excavation was accomplished was by means of a powerful apparatus termed a shield,
| ” |
The key innovation of the tunnelling shield was its support for the unlined ground in front and around it to reduce the risk of collapses. However, many workers, including Brunel himself, soon fell ill from the poor conditions caused by filthy sewage laden water seeping through from the river above. This sewage gave off methane gas which was ignited by the miner's oil lamps. When the resident engineer, William Armstrong, fell ill in April 1826 Marc's son Isambard Kingdom Brunel took over at the age of just 20.
Work was slow, progressing at only 8-12 feet a week (3-4 m). To earn some income from the tunnel the company directors allowed sightseers to view the shield in operation. An estimated 600-800 visitors per day paid 1 shilling for the adventure.
The excavation was also hazardous. The tunnel flooded suddenly on 18 May 1827 after 549 feet had been dug.[3] Isambard Kingdom Brunel lowered a diving bell from a boat to repair the hole at the bottom of the river, throwing bags filled with clay into the breach in the tunnel's roof. Following the repairs and the drainage of the tunnel, he held a banquet inside it.
The tunnel flooded again the following year, on 12 January 1828, when six men died and Isambard narrowly escaped drowning. Isambard was sent to Clifton in Bristol to recuperate where he heard about the competition to build what became the Clifton Suspension Bridge.
Financial problems followed, leading to the tunnel being walled off in August. The project was abandoned for seven years, until Marc Brunel succeeded in raising sufficient money (including a loan of £247,000 from the Treasury) to continue construction.[3]
When work resumed in February 1836, a new shield had to be installed. Impeded by further floods, fires and leaks of methane and hydrogen sulphide gas, the remainder of the tunnelling took another five and a half years, only being completed in November 1841. The extensive delays and repeated flooding made the tunnel the butt of metropolitan humour:
| “ | Good Monsieur Brunel Let misanthropy tell That your work, half complete, is begun ill; Heed them not, bore away Through gravel and clay, Nor doubt the success of your Tunnel. That very mishap, | ” |
The Thames Tunnel was fitted out with lighting, roadways and spiral staircases during 1841–1842. An engine house on the Rotherhithe side, which now houses the Brunel Museum, was also constructed to house machinery for draining the tunnel. The tunnel was finally opened to the public on 25 March 1843.[3]
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