Editing Breakwater (structure) (section)

==Breakwater armour units==
{{further|Wave-dissipating concrete block}}

As design wave heights get larger, rubble mound breakwaters require larger armour units to resist the wave forces. These armour units can be formed of concrete or natural rock. The largest standard grading for [[rock armour]] units given in CIRIA 683 "The Rock Manual" is 10–15 tonnes. Larger gradings may be available, but the ultimate size is limited in practice by the natural fracture properties of locally available rock.

Shaped concrete armour units (such as [[Dolos]], [[Xbloc]], [[Tetrapod (structure)|Tetrapod]], etc.) can be provided in up to approximately 40 tonnes (e.g. [[Jorf Lasfar]], Morocco), before they become vulnerable to damage under self weight, wave impact and thermal cracking of the complex shapes during casting/curing. Where the very largest armour units are required for the most exposed locations in very deep water, armour units are most often formed of concrete cubes, which have been used up to ~[http://www.dragados-usa.com/exp_tinnel_projet.php?pid=123&type=Port 195 tonnes] {{Webarchive|url=https://web.archive.org/web/20190512200547/https://www.dragados-usa.com/exp_tinnel_projet.php?pid=123&type=Port |date=2019-05-12 }} for the tip of the breakwater at Punta Langosteira near La Coruña, Spain.

Preliminary design of armour unit size is often undertaken using the [[Hudson's equation]], Van der Meer and more recently Van Gent et al.; these methods are all described in [http://rockmanual.dicea.nl CIRIA 683 "The Rock Manual"] and the United States Army Corps of Engineers [https://web.archive.org/web/20170506124610/http://www.publications.usace.army.mil/USACE-Publications/Engineer-Manuals/u43544q/636F617374616C20656E67696E656572696E67206D616E75616C/ Coastal engineering manual] (available for free online) and elsewhere. For detailed design the use of scaled physical hydraulic models remains the most reliable method for predicting real-life behavior of these complex structures.

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[[File:Yttre vågbrytaren Visby hamn.jpg|thumb|Similar wave motion along a seawall at the [[Visby]] breakwater in [[Sweden]]]]