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1、4500汉字，2900单词，14万英文字符The lock design of River MurrayRiver Murray NavigationThe weirs and locks were originally constructed on the River Murray in the 1920s and 1930s to provide year-round navigation for commercial cargo and passenger paddle steamers. They were generally built too late to be of benef
2、it to the river trade, as the development of railways and the growth of motorized road haulage had overtaken river transport. Today there are 13 navigation locks on River Murray weirs and two locks on the barrages at the Murray mouth.They are maintained and operated for the Murray-Darling Basin Comm
3、ission by the New South Wales, Victorian and South Australian Constructing Authoritiesto serve an increasing number of houseboats, tourist cruise boats and other recreational craft. The locks and weirs on the River Murray make an enormous contribution to the tourist industry in South Australia and S
4、unraysia.The River Murray is permanently navigable from the Bairages to the top of the Mildura Weir pool, near Nangiloc, a distance of 970 kilometres from the mouth. The River Murray was permanently navigable in its natural state to Blanchetown in South Australia. Eleven weirs with locks, each raisi
5、ng the water level behind it by an average of 3.1 metres, create a continuous series of stepped pools from Blanchetown to Mildura. The River Murray upstream of Nangiloc, at the top of the Mildura weir pool, is only navigable during periods of high flow.Passing Through a LockFor a boat to pass downst
6、ream through the lock, the water inside the chamber must be at the same level as the top weir pool, to allow the gates to open. The top gates are opened by hydraulic powered arms to allow the boat to enter. The gates are closed behind the boat and the water in the lock chamber is released by opening
7、 large hydraulically operated butterfly valves just above lock gates. The butterfly valves are only slightly smaller than an average house door. Water flows from the lock chamber, via tunnels, to the weir pool below. As the water level in the chamber drops, the boat is lowered with it, until equal t
8、o the level of the lower weir pool The bottom gates are then opened and the boat continues on its way. The water levels in the locks are raised and lowered entirely by gravity; no pumps are used.To travel upstream the reverse occurs. After the boat enters the lock chamber and the gates are closed be
9、hind it, valves are opened above the upstream gates to fill the chamber, via tunnels from the top weir pool. Water enters the chamber from the tunnels through ports spaced along the bottom of each wall. This is to distribute the inflowing water to minimise turbulence in the lock chamber as it fills.
10、 When the water level in the lock chamber is equal to the weir pool, the gates can be opened and the boat can proceed. It takes only 7 minutes to empty or fill the lock chamber but it normally takes 15 to 20 minutes to pass a boat through the lock. Six to eight medium houseboats can be accommodated
11、in one lockage.Lock DesignA lock is a simple design: a rectangular chamber of concrete with gates at each end. Locks have made pennanent inland water transport possible, as they enable boats to move from one level to another without danger or loss of large quantities of wale匚Locks similar to those o
12、f today were first used on the Grand Canal in China during the Eighth Century. In the Fifteenth Century, Leonardo da Vinci is reputed to have designed the first lock with the familiar pair of mitred swing gates at each end. This is the type of lock which is used on the River Murray. The gates close
13、to form a V against the current and upstream water pressure helps to keep them closed and make a watertight seal. The pressure of water within the lock chamber keeps the downstream gates closed.The designs for the locks, and associated weirs on the River Murray, except Mildura and Torrumbarry, were
14、developed by Captain E.N. Johnston of the United States Corps Engineers. Mildura weir and the first Torrumbarry weir were designed by John Dethridge of Dethridge wheel fame.South Australia benefited considerably from river transport and wished to establish permanent navigation on the River Murray. I
15、n 1912, the South Australian Government engaged Captain Johnston to prepare a report on a scheme for the improvement of the River Murray by locks and weirs. In addition to his experience with the various types of locks and weirs on the navigable rivers in the United States, Captain Johnston was also
16、 familiar with the engineering aspects of European inland waterways. The standard structure recommended by Captain Johnston to assist in the navigation of the River Murray consisted of three parts:a lock chamber, for use by boats during normal flow periodsa navigable pass consisting of steel collapsible trestles supporting Boule shutters- This section is used by boats during periods of high flow, after the Boule panels are withdrawn and the hinged trestles coll
