Editing Hydraulic fill

{{short description|Method of selectively emplacing soil or other materials using a stream of water}}
{{Refimprove|date=December 2013}}
[[File:Hydraulic sluicing (2429911419).jpg|thumb|right|Hydraulic sluicing]]

'''Hydraulic fill''' is a means of selectively emplacing soil or other materials using a stream of water.  It is also a term used to describe the materials thus emplaced.<ref>{{cite web|title=Initiating Hydraulic Fill Projects|url=http://www.iadc-dredging.com/ul/cms/fck-uploaded/documents/PDF%20Facts%20About/facts-about-initiating-hydraulic-fill-projects.pdf|publisher=International Association of Dredging Companies|access-date=16 December 2013|archive-url=https://web.archive.org/web/20140104054616/http://www.iadc-dredging.com/ul/cms/fck-uploaded/documents/PDF%20Facts%20About/facts-about-initiating-hydraulic-fill-projects.pdf|archive-date=4 January 2014|url-status=dead}}</ref> [[Gravity]], coupled with velocity control, is used to effect the selected deposition of the material.

[[Borrow pit]]s containing suitable material are accessible at an elevation such that the earth can be [[sluice]]d to the fill after being washed from the bank by high-pressure nozzles. Hydraulic fill is likely to be the most economic method of construction. Even when the source material lacks sufficient elevation, it can be elevated to the sluice by a dredge pump. 

In the construction of a hydraulic fill [[dam]], the edges of the dam are defined by low [[Embankment (earthworks)|embankment]]s or [[dyke (construction)|dykes]] which are built upward as the fill progresses. The sluices are carried parallel to, and just inside of, these dykes.{{Vague|date=March 2008}} The sluices discharge their water-earth mixture at intervals, the water fanning out and flowing towards the central pool which is maintained at the desired level by discharge control. While flowing from the sluices, coarse material is deposited first and then finer material is deposited (fine material has a slower terminal velocity thus takes longer to settle, see [[Stokes' Law]]) as the flow velocity is reduced towards the center of the dam. This fine material forms an impervious core to the dam. The water flow must be well controlled at all times, otherwise the central section may be bridged by tongues of coarse material which would facilitate seepage through the dam later.

Hydraulic fill dams can be dangerous in areas of seismic activity due to the high susceptibility of the uncompacted, cohesion-less soils in them to [[soil liquefaction|liquefaction]]. The [[1971_San_Fernando_earthquake#Van_Norman_Dam|Lower San Fernando Dam]]<ref>{{cite web|title=The Lower San Fernando Dam |url=http://www.geo-slope.com/contact/res/lower%20sanfernando%20dam.pdf |access-date=16 December 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131216110746/http://www.geo-slope.com/contact/res/lower%20sanfernando%20dam.pdf |archive-date=16 December 2013 }}</ref>  is an example of a hydraulic fill dam that failed during an earthquake.   In these situations, a dam built of compacted soil may be a better choice. 

Poorly built hydraulic fill dams pose a risk of catastrophic failure. The [[Fort Peck Dam]] is an example of a hydraulic fill dam that failed during construction where the hydraulic filling process may have contributed to the failure.<ref>{{cite web|last=French|first=Brett|title=Fort Peck Dam damage from 2011 being repaired|url=http://bismarcktribune.com/news/state-and-regional/fort-peck-dam-damage-from-being-repaired/article_9bbeb260-432e-11e3-b57a-001a4bcf887a.html|publisher=The Bismarck Tribune|access-date=16 December 2013}}</ref>

Hydraulic fill is also a term used in [[Underground mining (hard rock)|hard rock mining]] and describes the placement of finely ground [[mining waste]]s into underground [[Stoping (mining method)|stopes]] in a slurry by boreholes and pipes to stabilize the voids.

==References==
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[[Category:Hydraulic engineering]]