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.

Gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...

, coupled with velocity control, is used to effect the selected deposition of the material.

Borrow pit Digging, also referred to as excavation, is the process of using some implement such as claws, hands, manual tools or heavy equipment, to remove material from a solid surface, usually soil, sand or rock on the surface of Earth. Digging is actuall ...

s containing suitable material are accessible at an elevation such that the earth can be

sluice Sluice ( ) is a word for a channel controlled at its head by a movable gate which is called a sluice gate. A sluice gate is traditionally a wood or metal barrier sliding in grooves that are set in the sides of the waterway and can be considered ...

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 A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use ...

, the edges of the dam are defined by low

embankment Embankment may refer to: Geology and geography * A levee, an artificial bank raised above the immediately surrounding land to redirect or prevent flooding by a river, lake or sea * Embankment (earthworks), a raised bank to carry a road, railwa ...

s or dykes which are built upward as the fill progresses. The sluices are carried parallel to, and just inside of, these dykes. 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

Stoke's Law In 1851, George Gabriel Stokes derived an expression, now known as Stokes' law, for the frictional force – also called drag force – exerted on spherical objects with very small Reynolds numbers in a viscous fluid. Stokes' law is derived by s ...

) 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

liquefaction In materials science, liquefaction is a process that generates a liquid from a solid or a gas or that generates a non-liquid phase which behaves in accordance with fluid dynamics. It occurs both naturally and artificially. As an example of the ...

. The Lower San Fernando Dam 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 The Fort Peck Dam is the highest of six major dams along the Missouri River, located in northeast Montana in the United States, near Glasgow, and adjacent to the community of Fort Peck. At in length and over in height, it is the largest hyd ...

is an example of a hydraulic fill dam that failed during construction where the hydraulic filling process may have contributed to the failure. Hydraulic fill is also a term used in

hard rock mining Underground hard-rock mining refers to various underground mining techniques used to excavate "hard" minerals, usually those containing metals, such as ore containing gold, silver, iron, copper, zinc, nickel, tin, and lead. It also involves the ...

and describes the placement of finely ground

mining waste In mining, tailings are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different to overburden, which is the waste rock or other material that overli ...

s into underground stopes in a slurry by boreholes and pipes to stabilize the voids.

References

{{Use dmy dates, date=August 2019 Hydraulic engineering