Arch dam

An arch dam is most suitable for narrow canyons or gorges with steep walls of stable rock to support the structure and stresses.

[2] Since they are thinner than any other dam type, they require much less construction material, making them economical and practical in remote areas.

In general, arch dams are classified based on the ratio of the base thickness to the structural height (b/h) as:[1] Arch dams classified with respect to their structural height are:[1] The development of arch dams throughout history began with the Romans in the 1st century BC and after several designs and techniques were developed, relative uniformity was achieved in the 20th century.

The curved ends of the dam met with two winged walls that were later supported by two buttresses.

[6] The Dara Dam was another arch dam built by the Romans in which the historian Procopius would write of its design: "This barrier was not built in a straight line, but was bent into the shape of a crescent, so that the curve, by lying against the current of the river, might be able to offer still more resistance to the force of the stream.

The dam is still erect, even though part of its lower downstream face fell off.

[4] In the early 20th century, the world's first variable-radius arch dam was built on the Salmon Creek near Juneau, Alaska.

The dam was, therefore, revolutionary, and similar designs were soon adopted around the world, in particular by the U.S. Bureau of Reclamation.

[11] Pensacola Dam was one of the last multiple arch types built in the United States.

The foundation or abutments for an arch dam must be very stable and proportionate to the concrete.

[13] Contraction joints are normally placed every 20 m in the arch dam and are later filled with grout after the control cools and cures.