Whirley cranes
moving buckets of concrete to a monolith, December 1961.
Thomas E. Petermann Collection (S-2005-89-104)
The
worksite behind an earthen cofferdam, December 1961.
Thomas E. Petermann Collection (S-2005-89-101)
A gravity dam is made up of monoliths, giant concrete blocks built on top of and next to each other. To create the monoliths, cantilevered steel lifts (forms) are used to hold and shape the concrete until it is hardened. Chilled concrete, shallow lifts, and a precisely calculated cure time prevent the concrete from cracking.
After steel reinforcing rods were put into position, concrete was poured onto the sandblasted surface of the hardened monolith below the lift. The concrete mix was so stiff when it was poured that workers were able to walk on it and use a six-inch vibrator to consolidate the concrete and remove air pockets.
Three cofferdams made of earth or steel sheet piling were erected at different stages of the project. They served as temporary barriers to keep the White River from flooding the worksite.
Dimension
of lift: 48-feet wide by 7½-feet high |
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