EP 1110-2-13
28 Jun 96
Outside the valve a cylindrical sleeve moves
Top thickness (top width)
The thickness or width of a dam at the level of the top
downstream to shut off flow by sealing on the
of dam (excluding corbels or parapets). In general,
periphery of the cone.
the term thickness is used for gravity and arch dams,
and width is used for other dams.
Volume of dam
The total space occupied by the materials forming the
dam structure computed between abutments and from
Top of dam
The elevation of the uppermost surface of a dam,
top to bottom of dam. No deduction is made for
usually a road or walkway excluding any parapet
small openings such as galleries, adits, tunnels, and
wall, railing, etc.
operating chambers within the dam structure.
Portions of powerplants, locks, spillway, etc., should
be included only if they are necessary for the
Trashrack
A device located at an intake to prevent floating or
structural stability of the dam.
submerged debris from entering the intake.
Watershed divide
The divide or boundary between catchment areas (or
Tunnel
A long underground excavation with two or more
drainage areas).
openings to the surface, usually having a uniform
cross section used for access, conveying flows, etc.
Waterstop
A strip of metal, rubber, or other material used to
prevent leakage through joints between adjacent
Uplift
The uplift pressure in the pores of a material
sections of concrete.
(interstitial pressure) or on the base of a structure.
Wave runup
Vertical height above the stillwater level to which
Upstream blanket
An impervious blanket placed on the reservoir floor
and abutments upstream of a dam.
For an
embankment dam, the blanket may be connected to
the core.
Valve
A device fitted to a pipeline or orifice in which the
closure member is either rotated or moved
transversely or longitudinally in the waterway so as to
control or stop the flow.
a. Hollow jet valve. A device for regulating
high-pressure outlets. Essentially, it is half a needle
valve in which the needle closure member moves
upstream toward the inlet end of the valve to shut off
flow. As there is no convergence at the outlet end,
the flow emerges in the form of an annular cylinder,
segmented by several splitter ribs for admitting air
into the jet interior to prevent jet instability.
b. Regulating sleeve valve.
A valve for
regulating high pressure outlets and ensuring energy
dissipation. Inside the valve there is a fixed-cone,
pointed upstream, which ensures dispersion of the jet.
B-13
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