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The Panama Canal locks is a lock system that lifts a ship up to the main elevation of the Panama Canal and down again. It has a total of six steps (three up, three down) for a ship's passage. The total length of the lock structures, including the approach walls, is over . The locks were one of the greatest engineering works ever to be undertaken when they opened in 1914. No other concrete construction of comparable size was undertaken until the Hoover Dam, in the 1930s. There are two independent transit lanes, since each lock is built double. The size of the locks limits the maximum size of ships that can transit the canal; this size is known as Panamax. Construction on the Panama Canal expansion project began in September 2007.〔(【引用サイトリンク】title=Panama Canal Expansion Project report - October 2012 )〕 This will double the canal's capacity, allowing more and larger ships to use the canal.〔(【引用サイトリンク】title=Proposal for the Expansion of the Panama Canal )〕 The project is expected to be completed in April 2016. == Design == There are twelve locks in total. A two-step flight at Miraflores, and a single flight at Pedro Miguel, lift ships from the Pacific up to Gatun Lake; then a triple flight at Gatun lowers them to the Atlantic side. All three sets of locks are paired; that is, there are two parallel flights of locks at each of the three lock sites. This, in principle, allows ships to pass in opposite directions simultaneously; however, large ships cannot cross safely at speed in the Culebra Cut, so in practice ships pass in one direction for a time, then in the other, using both "lanes" of the locks in one direction at a time. The lock chambers are wide by long, with a usable length of . These dimensions determine the maximum size of ships that can use the canal; this size is known as Panamax. The total lift (the amount by which a ship is raised or lowered) in the three steps of the Gatun locks is ; the lift of the two-step Miraflores locks is . The single-step Pedro Miguel locks have a lift of . The lift at Miraflores actually varies due to the extreme tides on the Pacific side, between at extreme high tide and at extreme low tide; tidal differences on the Atlantic side are very small. The lock chambers are massive concrete structures. The side walls are from thick at the bases; toward the top, where less strength is required, they taper down in steps to . The center wall between the chambers is thick and houses three galleries that run its full length. The lowest of these is a drainage tunnel; above this is a gallery for electrical cabling; and toward the top is a passageway that allows operators to gain access to the lock machinery. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Panama Canal locks」の詳細全文を読む スポンサード リンク
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