Arch Dam

An arch dam is a dam with an arched or curved shape on the upstream face that naturally compresses together when water pushes up against it. This arch action is what gives the dam its apparent strength to hold back the water.^[1] The weight of the dam also works to press the entire structure downwards into the ground.^[2]

Essentially, the curved shape of an arch dam works to transfer the load (from water) to both the foundation and dam abutments by cantilever type action and also through the distribution of horizontal arches.^[3]

Another defining characteristic of arch dams is their uniquely thin shape. Arch dams typically require less concrete to build than other dam types but are also commonly reinforced using steel rods or pre-stressed steel cables.^[4]

Arch dams are often built is very narrow valleys, gorge ways, or mountainous regions where there is limited access to construction materials and naturally strong abutments. These valleys or gorge ways are more likely to be V-shaped as opposed to U-shaped.^[5]

[edit] History

The Romans were the first civilization to attempt building an arch dam, though somewhat sparingly considering the arch was a prominent shape incorporated in the construction of buildings and bridges at the time. One of the few true arch dams erected by the Romans was the dam Vallon de Baume built in France to supply water to the nearby town. The dam was 39.4 feet (12 m) high and 59 feet (18 m) long.^[6]

Another Roman arch dam was the Esparragalejo Dam near Merida, built around the first century A.D. and used for irrigation.^[7]

During the 13th century, the Mongols invaded Iran and settled there building many large dams including some arch dams up until the 14th century. The earliest of these arch dams was built near Kebar around 1300. The Kebar Dam was 85 feet (26 m) high and 180 feet (55 m) long. Around 1350, another arch dam was built near Kurit. For the time, this arch dam had an extraordinary height of 197 feet (60 m) and stood as the world’s highest arch dam until the early 1900s. Mongol arch dams were much more advanced than those built by the Romans, having thicker arch walls and greater heights. The arch dams were also very durable, being used for several centuries.^[8]

Arch dams later appeared in Europe. The first true arch dam was built in Elche, Spain. The Elche dam measured 243 feet (74 m) at the crest.^[9]

During the 17th century, Spanish dams were said to be superior to those of all other civilizations. This was evident when a Spaniard by the name of Don Pedro Villarreal de Berriz wrote the very first book about dam design. At this point in history, only arch dams for narrow sites and solid rock foundations and gravity dams for more wide and shallow sites were being built. The book was instrumental in showcasing new concepts in dam design, including the use of multiple arch dams.^[10]

Arch dams were being built worldwide by the early part of the 19th century. The 1960s then brought a revival of arch dam construction in the U.S., especially the adoption of a double-curvature design in projects as the 469-foot (143 m) high Morrow Point Dam built in 1968. However, despite their perfection and high level of productivity, the construction of arch dams declined in the last few decades.^[11]

[edit] Types

A constant radius arch dam is a dam that has a vertical upstream face with a constant radius of curvature.^[12]

A variable radius dam is a dam that has both upstream and downstream curves (also called extrados and intrados curves) of systematically decreasing radii with depth below the crest.^[13]

A dome dam is an arched dam with a double-curved vertical and horizontal plane.^[14]

A multiple arch dam is a dam with more than one contiguous arch or plane.^[15]

A double arch dam is a dam with two contiguous arches.^[16]

[edit] References

1. ↑ Arch. SimScience. 2008-09-30.
2. ↑ Arch Forces. PBS Org. 2008-09-30.
3. ↑ Dams. Dur. 2008-09-30.
4. ↑ Dams. Dur. 2008-09-30.
5. ↑ Arch. SimScience. 2008-09-30.
6. ↑ Arch. Simscience. 2008-09-30.
7. ↑ Arch Dams. Trainaus. 2008-09-30.
8. ↑ Arch Dams. Traianus. 2008-09-30.
9. ↑ Arch History. Simscience. 2008-09-30.
10. ↑ Dam History. UC Davis. 2008-09-30.
11. ↑ Arch History. SimScience. 2008-09-30.
12. ↑ Dams Dur. 2008-09-30.
13. ↑ Dams. Dur. 2008-09-30.
14. ↑ Dams. Dur. 2008-09-30.
15. ↑ Cat Technology. Answers.com. 2008-09-30.
16. ↑ Cat Technology. Answers.com. 2008-09-30.