aqueduct
Aqueduct
aqueduct
[′ak·wə‚dəkt]aqueduct
Aqueduct
a water main (or canal or pipe) for conveying water to population centers and irrigation and hydroelectric installations from sources located at higher altitudes. The term “aqueduct” may also refer to a part of the water main—the bridge over ditches, rivers, and roads. Above-ground aqueducts (with open conduits) and underground aqueducts were built in the ancient East beginning in the second millennium B.C. and in ancient Greece beginning in the seventh century B.C. Some aqueducts of Rome and of the provinces of the Roman Empire have been preserved; the former date from the fourth century B.C. and have a total length of 436 km, 55 km of which are bridge constructions. Arched stone bridge aqueducts with closed conduits 1–1.7 m wide, excellent in design and of majestic architecture, have been preserved; the span of the arches varies between 5.6 m (the Aqua Marcia, Rome; 140 B.C.) and 25 m (the Pont du Gard aqueduct, near Nimes, France; end of the first century B.C.); they were as high as 49 m and about 300 m long (the now-operating aqueduct near Segovia, Spain, A.D. 109). Medieval installations include the Burgas aqueducts, dating from about the sixth century, near Constantinople, and several later ones in France, Italy, and Spain. In modern irrigation and hydroelectric systems, the bridge parts of the aqueducts (with arch, frame, or girder structures) are made of concrete, reinforced concrete, metal, and more rarely of wood. In most aqueducts the walls and the bottom of the conduit (primarily rectangular in cross section) or pipes form the span framework of the bridge. Bulkheads are erected at the juncture of the bridge and the canal; the bulkheads also serve as an antiseepage device. An example of a modern monumental aqueduct is the aqueduct on the Razdan River in Yerevan (1949, architect, R. Israelian; engineer, G. Egiian).
REFERENCES
Ashby, T. The Aqueducts of Ancient Rome. Oxford, 1935.Grishin, M. M. Gidrotekhnicheskie sooruzheniia, 2nd ed., vol. 2. Moscow, 1955.
Aqueduct
a structure for conveying (delivering) water to the place of use. Aqueducts run from rivers, reservoirs, lakes, or other bodies of water. A distinction is made among power-engineering (diversion and turbine feeds) aqueducts, which carry water to hydroelectric power plants; irrigation aqueducts; and water-supply aqueducts.
Aqueducts are built in the form of artificial stream beds of closed cross section (underground piping and tunnels) or open cross section (canals and gutters in trenches, on embankments, or on supports such as trestles). Materials used in their construction include steel, reinforced concrete (including prestressed concrete), asbestos cement, and wood. Water may be moved along aqueducts constructed in the form of pipes by the pressure created by dams or pumps (pressure aqueducts) or by gravity flow, taking advantage of varying ground elevations (gravity or gravitational aqueducts). In terms of hydraulics, aqueducts are divided into pressure aqueducts, in which the entire cross section is filled, and free-flowing aqueducts, in which only part of the cross section is filled with water. The basic characteristic of an aqueduct is the fact that its maximum carrying capacity, or water flow rate, is determined by the size of its cross section.
REFERENCE
Grishin, M. M. Gidrotekhnicheskie sooruzheniia. Moscow, 1968.V. A. ORLOV