WORLD ACHIEVEMENT

Manawatu Standard, Volume LIX, Issue 161, 9 June 1939, Page 9

WORLD ACHIEVEMENT

THE BOULDER DAM. An achievement, of modern times is the construction in America of the Boulder Dam. Crossing the Black Canyon on the Colorado River between Arizona and Nevada, in the United States, it is Infar tiie largest dam ever Imilt, and second only to the Great Pyramid as the world’s largest “block” of solid masonry. Built in record time (concrete being placed in position at an average rate of 7000 cubic yards every twenty-four hours’) the dam has a spread or stance of 9GG6 feet at the base, and a width of 45 feet at flic crest. It is 1180 feci long at tiie top. and lias a height of 720 feet. The axial radius of tiie arch convex face upstream, is 500 feet. 1 lie approximate dead weight of tiie dam is 0.500.000 tons. One of flic most striking features of tiie constructional work was the elaborate measures taken to cool tiie vast masses of concrete. If it had been left to contract normally, it would have taken more than 100 years before it. has assumed its final size, besides being in great danger of a general collapse. Instead of allowing the rate of contraction to go on slowlv pipes were laid down in each block of cement, these being connected with mains which led them to a refrigeration plant. An atmospheric cooling tower was used to cool the river water ■to 7040 g. F. and this water passed through the pipes laid in the concrete. Later, water cooled to a tomneratore between 47deg. and 40dcg. F.. by three ammonia refrigerating compressors, each operated hv a 250 h.p- motor, was passed along the pipes. In this way the heat of hydration of the great 6-million-tnn mass was cooled as Mm dam was built, and before the concrete bad become bard ihe st r nctuie was occupying its final size.—(L.f.