Examine individual changes

'[[File:Morrowdam.JPG|thumb|230px|The [[Morrow Point Dam]] is a double-curvature arch dam.]] An '''arch dam''' is a solid [[dam]] made of [[concrete]] that is curved upstream in plan.<ref name="USBR" /> The arch dam is designed so that the force of the water against it, known as [[hydrostatic pressure]], presses against the arch, compressing and strengthening the structure as it pushes into its foundation or abutments. An arch dam is most suitable for narrow [[canyon|gorge]]s or [[canyon]]s with steep walls of stable rock to support the structure and stresses.<ref>{{cite web|url=http://www.pbs.org/wgbh/buildingbig/dam/arch_forces.html|title=Arch Dam Forces|publisher=|accessdate=2007-02-05| archiveurl= http://web.archive.org/web/20070205044521/http://www.pbs.org/wgbh/buildingbig/dam/arch_forces.html| archivedate= 5 February 2007 <!--DASHBot-->| deadurl= no}}</ref> Since they are thinner than any other dam type, they require much less construction material, making them economical and practical in remote areas. ==Classification== In general, arch dams are classified based on the ratio of the base thickness to the structural height (b/h) as:<ref name="USBR" /> * Thin, for b/h less than 0.2, * Medium-thick, for b/h between 0.2 and 0.3, and * Thick, for b/h ratio over 0.3. Arch dams classified with respect to their structural height are:<ref name="USBR" /> * Low dams up to 100 feet, * Medium high dams between 100– 300 feet, * High dams over 300 feet. == History == [[Image:Shah Abbas Arch Dam.jpg|280px|thumb|right|Shāh Abbās Arch near [[Kurit Dam]] - 12th century]] The development of arch dams throughout history began with the [[Ancient Rome|Romans]] in the 1st century BC and after several designs and techniques were developed, relative uniformity was achieved in the 20th century. The first known arch dam, the [[Glanum Dam]], also known as the Vallon de Baume Dam, was built by the [[Ancient Rome|Romans]] in [[France]] and it dates back to the 1st century BC.<ref name="smith">{{Citation| last = Smith| first = Norman| title = A History of Dams| place = London| publisher = Peter Davies| year = 1971| isbn = 0-432-15090-0}}</ref><ref name="simsci">{{cite web|title=Key Developments in the History of Arch Dams|url=https://web.archive.org/web/20120728110447/http://simscience.org/cracks/advanced/arch_hist1.html|work=Cracking Dams|publisher=SimScience|accessdate=18 July 2010}} from archive.org</ref><ref>{{cite web|last=D.Patrick JAMES|first=Hubert CHANSON|title=Historical Development of Arch Dams. From Cut-Stone Arches to Modern Concrete Designs|url=http://www.traianvs.net/textos/archdams_en.htm|publisher=Barrages.org|accessdate=18 July 2010}}</ref> The dam was about 12m high and 18m in length. Its radius was about 14m and it consisted of two masonry walls. The Romans built it to supply nearby [[Glanum]] with water. The Monte Novo Dam in [[Portugal]] was another early arch [[List of Roman dams and reservoirs|dam built by the Romans]] in 300 AD. It was {{convert|5.7|m|feet}} high and {{convert|52|m|feet}} long with a radius of {{convert|19|m|feet}}. The curved ends of the dam met with two winged walls that were later supported by two buttresses. The dam also contained two water outlets to drive mills downstream.<ref>{{cite web|last=Chaason|first=Hubert |title=EXTREME RESERVOIR SEDIMENTATION IN AUSTRALIA: A REVIEW|url=http://espace.library.uq.edu.au/eserv/UQ:124112/un_watresjl_98.pdf|work=Resources Journal|accessdate=18 July 2010|page=101}}</ref> 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."<ref name="smith"/> The [[Mongol Empire|Mongols]] also built arch dams in modern-day Iran. Their earliest was the [[Kebar Dam]] built around 1300, which was {{convert|26|m|feet}} high and {{convert|55|m|feet}} long, and had a radius of {{convert|35|m|feet}}. Their second dam was built around 1350 and is called the [[Kurit Dam]]. After {{convert|4|m|feet}} was added to the dam in 1850, it became {{convert|64|m|feet}} tall and remained the tallest dam in the world until the early 20th century. The Kurit Dam was of masonry design and built in a very narrow canyon. The canyon was so narrow that its crest length is only 44% of its height. The dam is still erect, even though part of its lower downstream face fell off.<ref name="simsci"/> The Elche Dam in [[Elche]], [[Spain]] was a post-medieval arch dam built in the 1630s by Joanes del Temple and the first in Europe since the Romans. The dam was {{convert|26|m|feet}} high and {{convert|75|m|feet}} long, and had a radius of {{convert|62|m|feet}}. This arch dam also rests on winged walls that served as abutments.<ref name="simsci"/> In the 20th century, the world's first variable-radius arch dam was built on the [[Salmon Creek Dam|Salmon Creek]] near [[Juneau]], [[Alaska]]. The Salmon Creek Dam's upstream face bulged upstream, which relieved pressure on the stronger, curved lower arches near the abutments. The dam also had a larger toe, which off-set pressure on the upstream heel of the dam, which now curved more downstream. The technology and economical benefits of the Salmon Creek Dam allowed for larger and taller dam designs. The dam was, therefore, revolutionary, and similar designs were soon adopted around the world, in particular by the [[U.S. Bureau of Reclamation]].<ref name="simsci"/> [[File:Enguri Dam, Georgia.jpg|thumb|left|200px|The Inguri Dam in Georgia.]] [[Pensacola Dam]], completed in the state of [[Oklahoma]] in 1940, was considered the longest multiple arch dam in the world. Designed by [[W. R. Holway]], it has 51 arches. and a maximum height of {{Convert|150|ft|abbr=on}} above the river bed. The total length of the dam and its sections is {{Convert|6565|ft|abbr=on}} while the multiple-arch section is {{Convert|4284|ft|abbr=on}} long and its combination with the spillway sections measure {{Convert|5145|ft|abbr=on}}. Each arch in the dam has a clear span of {{Convert|60|ft|abbr=on}} and each buttress is {{Convert|24|ft|abbr=on}} wide.<ref name="NRHP_App">[http://www.ocgi.okstate.edu/shpo/nhrpdfs/03000883.pdf" National Register of Historic Places. Pensacola Dam".] Accessed January 3, 2016.</ref> Arch dam designs would continue to test new limits and designs such as the double- and multiple-curve. The Swiss engineer Alfred Stucky and the U.S. Bureau of Reclamation would develop a method of weight and stress distribution in the 1960s, and arch dam construction in the United States would see its last surge then with dams like the 143-meter double-curved [[Morrow Point Dam]] in Colorado, completed in 1968.<ref>{{cite web|title=Arch Dam Design Concepts and Criteria|url=http://www.dur.ac.uk/~des0www4/cal/dams/conc/concf13.htm|publisher=Durham University|accessdate=18 July 2010}}</ref> By the late 20th century, arch dam design reached a relative uniformity in design around the world.<ref name="simsci"/> Currently, the tallest and largest arch dam in the world is the {{convert|292|m|feet}} [[Xiaowan Dam]] in [[China]], which was completed in 2010.<ref name="simsci"/> The longest multiple arch with buttress dam in the world is the [[Daniel-Johnson Dam]] in [[Quebec]], [[Canada]]. It is {{convert|214| meters|feet}} high and {{convert|1314|meters|feet}} long across its crest. It was completed in 1968 and put in service in 1970.<ref>{{cite web|last= Guimont|first=Andréanne|date=3 August 2010|title=Manic 5 : colossal témoin du génie québécois en hydroélectricité|url=http://canada.suite101.fr/article.cfm/manic-5--colossal-temoin-du-genie-quebecois-en-hydroelectricite|publisher=suite101.fr|accessdate=30 September 2010| archiveurl= http://web.archive.org/web/20100817021129/http://canada.suite101.fr/article.cfm/manic-5--colossal-temoin-du-genie-quebecois-en-hydroelectricite| archivedate= 17 August 2010 <!--DASHBot-->| deadurl= no}}</ref> In 2013, China completed an arch dam, [[Jinping 1 Dam]], which is world's tallest at {{convert|305|m|feet}}.<ref>{{cite web|title=The world's highest arch dam Jinping first production unit|url=http://energy.people.com.cn/n/2013/0902/c71661-22774787.html|publisher=Economic Times Network|accessdate=9 September 2013|language=Chinese|date=2 September 2013}}</ref> Pensacola Dam was one of the last multiple arch types built in the United States. Its NRHP application states that this was because three dams of this type failed: (1) Gem Lake Dam, [[St. Francis Dam]] (California), Lake Hodges Dam (California). None of these failures were inherently caused by the multiple arch design.<ref name="NRHP_App"/> == Design == The design of an arch dam is a very complex process. It starts with an initial dam layout, that is continually improved until the design objectives are achieved within the design criteria.<ref name="USBR" /><ref name="USACE" /> ===Loads=== The main loads for which an arch dam is designed are:<ref name="USBR" /><ref name="USACE" /> * Dead load * Hydrostatic load generated by the reservoir and the tailwater * Temperature load * Earthquake load Other miscellaneous loads that affect a dam include: ice and silt loads, and uplift pressure.<ref name="USBR">{{Citation| last = | first = | title = Design of Arch Dams - Design Manual for Concrete Arch Dams| place = Denver Colorado| publisher = Bureau of Reclamation| year = 1977| isbn = }}</ref> <ref name="USACE">{{Citation| last = | first = | title = Arch Dam Design - Engineering Manual EM 1110-2-2201| place = Washington DC| publisher = U.S.Army Corps of Engineers| year = 1994| isbn = }}</ref> [[File:IdukkiDamConcaveSide.jpg|thumb|The [[Idukki Dam]] in [[Kerala]].]] Most often, the arch dam is made of concrete and placed in a "V"-shaped valley. The foundation or abutments for an arch dam must be very stable and proportionate to the concrete. There are two basic designs for an arch dam: ''constant-radius dams'', which have constant radius of curvature, and ''variable-radius dams'', which have both upstream and downstream curves that systematically decrease in radius below the crest. A dam that is ''double-curved'' in both its horizontal and vertical planes may be called a '''dome dam'''. Arch dams with more than one contiguous arch or plane are described as '''multiple-arch dams'''. Early examples include the Roman [[Esparragalejo Dam]] with later examples such as the Daniel-Johnson Dam (1968) and [[Itaipu Dam]] (1982). However, as a result of the failure of the [[Gleno Dam]] shortly after it was constructed in 1923, the construction of new multiple arch dams has become less popular.<ref name="Herzog">{{Cite book |last=Herzog |first=Max A. M. |authorlink= |title=Practical Dam Analysis |publisher=Thomas Telford Publishing |year=1999 |location=London |pages=115, 119–126 |url=http://books.google.com/books?id=gSSEGDjakBYC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false |isbn=3-8041-2070-9}}</ref> Contraction joints are normally placed every 20 m in the arch dam and are later filled with [[grout]] after the control cools and cures.<ref>{{cite web|title=Contraction Joints|url=http://www.dur.ac.uk/~des0www4/cal/dams/conc/concf16.htm|work=Arch Dams|publisher=Durham University|accessdate=18 July 2010}}</ref> == Examples of arch dams == [[File:Presa de El Atazar - 01.jpg|240px|thumbnail|[[El Atazar Dam]], near [[Madrid]]]] * [[Buchanan Dam]] (example of multiple-arch type) * [[Contra Dam]] * [[Daniel-Johnson Dam]] * [[Deriner Dam]] * [[El Atazar Dam]] * [[Flaming Gorge Dam]] * [[Glen Canyon Dam]] * [[Idukki Dam]] * [[Inguri Dam]] * [[Karun-3 Dam]] * [[Luzzone Dam]] * [[Mauvoisin Dam]] * [[Pensacola Dam]] (longest multiple-arch type) * [[St. Francis Dam]] * [[Victoria Dam (Sri Lanka)|Victoria Dam]] * [[Xiluodu Dam]] == See also == * [[Dam]] * [[Gravity dam]] * [[Arch-gravity dam]] == References == {{Reflist}} == External links == {{Commons category|Arch dams}} * [http://www.pbs.org/wgbh/buildingbig/dam/basics.html PBS Dam Basics] * [http://www.traianvs.net/textos/archdams_en.htm Historical Development of Arch Dams. From Cut-Stone Arches to Modern Concrete Designs] * [https://web.archive.org/web/20120728110447/http://simscience.org/cracks/advanced/arch_hist1.html Key Developments in the History of Arch Dams], from archive.org [[Category:Dams by type]] [[Category:Arch dams|*]]'