Terms used in civil Engineering of Dams

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Basic Terms of Dam Engineering:

Dams are the most amazing and eyecatching construction so far man has made. When US president Frankin Roosevelt inaugurated the Hoover dam in 1935, the scene was unbelievable and he uttered these words: "I came, I saw and I was conquered". Dams are of tremendous significance in the development of mankind. While keeping in mind the increasing importance of the subject of dams in civil engineering writing detailed notes were felt unavoidable. After writing two detailed articles about the dams: Types of dams and spillways, we felt the need of explaining the terminology used in the civil engineering of the dams.

ABUTMENT: Abutments are the supports constructed at each opposite valley side. The dam's main wall is supported by abutments. The abutments are deep-rooted and firmly installed in the rocks of the valley side.
BASE WIDTH: The width of the dam foundation is called base width.
BREACH: An irregular breakthrough or rupture in the embankment of the dam due to the erosion caused by the flow of water.
CONDUIT: It is the conveying part of the dam. It is a closed channel to convey the discharge through or under a dam. Usually, pipes constructed of concrete or steel.
IMPERVIOUS CORE or ZONE OF THE DAM: The mid of the dam-wall is called the core of the dam. The core is generally constructed with concrete, wooden panels, and steel plates. This is an impermeable section of the dam. It prevents the dam water to seep out through the dame dump.
TRAINING WALL: This wall confines and guides the flow of the water.
TRASH RACK: It is constructed in the waterway from the intake side to control the flow of debris.
PREVIOUS ZONE: As the name mentions, the previous zone allow water to seep or flow.
RIPRAP: A barrier of large stones, broken rocks, blocks of concrete placed in the reservoir just before the dame embankment. Its duty is to prevent the dame from the strike of waves and ice blocks.
SEEPAGE COLLAR: In order to prevent the basement of the embankment from erosion, the water accumulated by means of seeping, is projected ahead from the foundation by means of pipes and conduits.
CREST OF DAM: The top of the dam and spillway is said to be the crest of the dam. A crest is a plane and smooth (in some cases paved) surface of the dame. The top surface of the dam is called the crest.
CUT-OFF of the Dam: Placement of an impervious material in the foundation of the dam is called the cut-off of the dam.
CUTOFF WALL: The cut-off of the dam is constructed with a concrete, wooden, or steel wall which is impervious to water, and prevents water to seep out. The wall which is constructed for the purpose of protecting water from seepage is called the cut-off wall.
DRAINAGE LAYER OR BLANKET: A very permeable structure placed directly over the used to remove water or to control groundwater seepage from cut slopes or beneath fills.
CREST LENGTH: Crest the surface above the spillway. The crest is as long as the dam is. It covers the whole span of the dam. The length of the dam is equal to the length of the crest.
TOE OF DAM: The junction between the downstream face of the dam with the river floor is called the Toe of the dam.
TOP OF DAM: The uppermost surface in the form of a road or walkway is called the top of the dam.
TOP THICKNESS: The width of the top of the dam is called the top thickness of the dam. The uppermost width of the dam is called the thickness of the dam.
Abutments: The part of the valley sides of the dams, constructed with concrete material or masonry work. The function of the abutments is to provide support to the wall of the dam.
The base of the Dam: The base is the total width of the basement of the dam, which descends with vertical ascend of the dam.
Crest: Crest the uppermost plane surface of the dam. It is the overflow part of the dam.
Cutoff: The cut-off of the dame is an impervious material, which prevents the seepage of water through the base section of the dam.
Cut-off Wall: The wall of impervious material like wood panels, concrete, or steel is constructed in the core of the dame. The purpose of this wall is to prevent seepage. Keep in view that seepage harms the solidarity of the dam.
The face of the Dame: The side of the dam which is faced by the downstream.
Upstream: Upstream of a dam is the level of water reservoir held back by the dam. The water of Upstream flows through the conduit toward the downstream.
Parapet Walls: The parapet walls of the dams are constructed on the crest of the dam. The function of the parapet wall is to give protection to the tourists.
The heel of the dam: The junction of the upstream face with the foundation of the dam is called the heel of the dam.
Toe of the dam: The junction of downstream of the dam with the ground is called the toe of the dam.
Crest Gate/ Spillway Gate: These gates are installed on the crest of the spillway. The duty of these gates is to allow a controlled quantity of the reservoir water.
Flap Gate: They are flow control gates, which are hinged from their top.
Outlet Gate: It controls the outlet flow of water from the reservoir.
Radial Gate: A gate with radial arms and curved upstream plates.
Slide Gate: This type of gate can be opened and closed by sliding it.
INTAKE: Any type of structure which transit water from the reservoir to the outlet.
LOW-LEVEL OUTLET: Opening which is constructed at the low level, near the foundation of the dam.
OUTLET: A hole or opening used to allow water flow from the reservoir toward the downstream.
DRAWDOWN: As the water releases from the reservoir, it results in lowering down the water level in the reservoir. The process of lowering down the water level is called Drawdown.
EMBANKMENT: The dump of fill material of soil, rocks, debris, sand, and gravel is called an embankment.
EMERGENCY ACTION PLAN: A precautionary conduit is built within the structure of the dam, to release the water at the time of emergency in order to prevent a flash flood.
FACE: The external face or the downstream side of the dam is called a face.
FLASHBOARDS: The crest of the spillway is elevated with the help of dumping wooding, timber, concrete, and steel material in order to further resist the flow of water. But at the time of the rising water level, these materials are abruptly removed.
FOUNDATION OF DAM: A wide span, thick and heavy concrete basement of the dam which is partly sunk into the river floor is called the foundation of the dam.
FREEBOARD: The distance from the water surface to the lowest top of the dam, at which the dam would overflow, is called freeboard.
GATE: Gates are used to stopping or controlling water flow. These gates are sliding gates, which can be removed and closed.
CREST GATE or SPILLWAY GATE: A gate installed at the crest of the spillway that controls the overflow of the water of the reservoir.
STOP LOGS: Large logs, timbers, or steel beams placed on top of each other with their ends held in guides on each side of a channel or conduit so as to provide a cheaper or more easily handled means of temporary closure than a bulkhead gate.
STRUCTURAL HEIGHT: The vertical distance from the lowest point of natural ground on the downstream side of the dam to the highest part of the dam which would impound water.
SPILLWAY: A structure over or through which flood flows are discharged. If the flow is controlled by gates, it is considered a controlled spillway; if the elevation of the spillway crest is the only control, it is considered an uncontrolled spillway.
AUXILIARY SPILLWAY (EMERGENCY SPILLWAY): A secondary spillway· designed to operate only during exceptionally large floods.
OGEE SPILLWAY (OGEE SECTION): An overflow spillway, which in cross section· the crest, downstream slope, and bucket have an “S” or ogee form of a curve. The shape is intended to match the underside of the nappe at its upper extremities.
SPILLWAY CHANNEL (SPILLWAY TUNNEL): A channel or tunnel conveying water from the spillway to the river downstream.

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Terms used in civil Engineering of Dams

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