WHAT IS THE FUNCTION OF DAMS? HOW DAM WORKS?

Definition of the Dam

Dam is constructions that are built to hold the flow of water into reservoirs, lakes, or recreational areas. Often dams are also used to drain water to a hydroelectric power station.

Parts of the Dam

The dam consists of several components, namely:

1. Built of Dam

Built of Dams

It is a dam body that functions as a water barrier. Basically, dams are built to hold water. The power of water provides electricity stored in water pumps and this is used to provide electricity for millions of consumers.

2. Foundation

It is part of a dam that serves to maintain the sturdy dam.

3. Floodgate

Used to regulate, open and close the flow of water in both open and closed channels. The important parts of the floodgates are:

a. Door Leaf

It is the part of the sluice which holds water pressure and can be moved to open, regulate and close the flow of water.

b. Guide Frame

It is a groove of steel or iron that is installed into the concrete that is used to keep the movement of the door leaf as planned.

c. Anchorage

Is steel or iron that is planted in concrete and is used to hold the frame of the direction of movement to move the load from the floodgates into concrete construction

d. Hoist

It is a tool to move the sluice gate so that it can be opened and closed easily.

4. Spillway of Dam

Spillway

It is a building and its installation to drain floodwater into the reservoir so that it does not endanger the safety of the dam. Important parts of the overflow building:

Directional and control structures

Used to direct and regulate the flow of water so that the flow velocity is small but the water flow is large.

Tube launcher, chute, discharge carrier, floodway

The higher the dam, the greater the difference between the highest water level in the reservoir with the water level of the river downstream of the dam. If the slope of the water discharge channel is made small, the size will be very long and the building will become expensive. Therefore, the slope is forced to be made large, by itself adapted to local topographic conditions.

Energy dissipator

Used to eliminate or at least reduce water energy so as not to damage cliffs, bridges, roads, buildings and other installations downstream of the overflow building.

5. Canal

Used to collect water overflow when rainfall is high.

6. Reservoir

Used to collect/receive abundant water from dams.

7. Stilling basin

It has the same function as an energy dissipater.

8. Valves (lint, valves)

Its function is the same as ordinary flood gates, it can only withstand higher pressures (water pipes, rapid pipes, and pressure tunnels). It is a tool to open, regulate and close the flow of water by rotating, moving towards the transverse or holding in the water channel.

9. Drainage gallery

Used as a power plant on the dam.

3 Types of Dam

Types of Dam

Dams are also divided into several types, namely:

a. By size Dam

1) large dams

According to ICOLD, the definition of a dam is:

a. Dam is more than 15m high, measured from the bottom of the foundation to the top of the dam.
b. Dams that are between 10m and 15m in height can also be called a large dam as long as they meet one or more of the following criteria:
  1. The length of the dam peak is not less than 500m.
  2. The capacity of the formed reservoir is not less than 1 million m³.
  3. The maximum flood discharge calculated is not less than 2000 m³ / sec.
  4. The dam faces special difficulties in its foundation (had especially difficult foundation problems).
  5. The dam is designed not as usual (unusual design).

2) Small dams (small dams, weir, weir)

All dams that do not qualify as large dams are called small dams.

b.  Dam based on the purpose of its development

  1. Single-purpose dams
    It is a dam that is built to fulfill only one purpose.
  2. Multipurpose dams
    Dams are built to fulfill several purposes.

c. Dam based on its use

1) Dam to make reservoirs (storage dams)

It is a dam that was built to form a reservoir to store water in excess when it can be used when needed.

2) Dams catchers/divers of water (diversion dams)

Dam is built so that the surface water is higher so that it can flow into the water channel or water tunnel.

3) Dam to slow down the water (detention dams)

It is a dam that was built to slow down the flow of water to prevent major flooding.

d. Dam based on the construction

dams

1) fill dams, embankment dams

According to ICOLD, the definition is a dam built from the excavation of material (material) without the addition of other materials that are chemically mixed, so it’s the original dam-forming material. This dam can still be divided into:

a. Homogeneous dams

fill dams is the same layer.

b. Multiple layers of dam (zone dams, rockfill dams)

fill dams consists of several layers, namely a waterproof layer (watertight layer), rock layer (rock zones, shell), regular rock layer (rip-rap) and dryer layer (filter zones).

c. Dam rock fill with a waterproof layer on the face (impermeable face rockfill dams, decked rockfill dams)

It is a multi-layered stone reservoir whose water-resistant layer is placed upstream of the dam. Waterproof coatings commonly used are asphalt and reinforced concrete.

2) Concrete dams

Dam is made of concrete construction both with reinforcement or not. This can still be further divided into:

  • Concrete dam based on its weight (concrete gravity dams) Is a concrete dam that is designed to withstand the load and the force acting on it only with its weight.
  • Concrete dams with supports (concrete buttress dams)
    It is a concrete dam that has a buffer to channel the forces acting on it. Widely used when the river is very wide while the geological condition is good.
  • Curved concrete dams (concrete shaped arches or concrete arch dams) Are concrete dams designed to channel the forces acting on them through the left abutment and right abutment of the dam.
  • Concrete combination dams (combination concrete dams, mixed type concrete dams) Is a combination of more than one type of dam.

3) Other dams

Usually only for small dams, for example, timber dams, steel dams, brick dams, masonry dams.

e. Dam based on its function

1) Preliminary Evacuation Dam (primary cofferdam, dike)

It is the dam that was first built in the river at the time of low water discharge so that the location of the planned evacuation dam becomes dry which enables its construction technically.

2) Dodge dam (cofferdam)

It is a dam that was built after the completion of the prelude dam so that the location of the main dam plan is dry which makes it possible to develop technically.

3) Main dam (main dam)

A dam is built to fulfill one or more specific objectives.

4) Side dam (high-level dam)

The dam is located on the left side and right side of the main dam whose height is also the same peak. This is used to make the project as optimal as possible, meaning that by adding height to the main dam the maximum results are obtained even if you have to raise the left and / or right sides.

5) Dam in a low place (saddle dam)

The dam is located on the edge of the reservoir far from the main dam that was built to prevent water from the reservoir so that the reservoir water does not flow into the surrounding area.

6) Embankment (dike, levee)

Dam is located on the left and or right side of the main dam and in a place far from the main dam with a maximum height of only 5 m with a maximum peak length of 5 times its height.

7) Industrial waste dams

It is a dam that consists of piles gradually to hold back the waste that comes from industry.

8) Mining dams (mine tailing dam, tailing dam)

It is a dam that consists of piles gradually to hold the results of mining excavation and the material made from mining excavations as well.

f. Dam based on the running of water

dams

1) Dam for water flowing (overflow dam)

It is a dam that is built for water to pass, for example in a spillway.

2) Dam to hold water (non-overflow dam)

It is a dam that absolutely cannot be crossed by water.
These two types are usually built next to each other and are made of concrete, masonry or masonry.

dams are a construction that is built to hold the flow of water into reservoirs, lakes, or recreational areas. Often dams are also used to drain water to a hydroelectric power station. Most dams also have a section called sluice to remove unwanted water gradually or continuously.

Dams and weir are different structures. Weir is a low-head dam structure, which serves to raise the water level, usually found in rivers. River water whose surface is raised will run through the top/lighthouse weir (overflow). It can be used as a gauge of the speed of water flow in a channel/river and can also be a traditional milling driver in European countries.

In countries with large enough rivers and swift flow, a series of weirs can be operated to form a water transportation system. In Indonesia, weirs can be used for irrigation if, for example, the river water level is lower than the surface of the water to be irrigated.

Dam function:

  • Dams for water supply and irrigation, hold water in reservoirs. This water is then channeled to cities or agriculture using large pipes or channels.
  • Hydropower Dam uses water to drive turbines to generate electricity. After passing through the turbine the water is then released back to the river which is located under the dam.
  • Flood control dams, collecting water during heavy rains to reduce flooding downstream of the river.
  • Navigation Dams, hold water and release it when the water in the river is low. This dam is usually used to move ships that are sailing through the dam.
  • Dams that divide water flow, divide water into other channels.
  • Dams for recreation, dams made as a place of recreation to enjoy the beauty of nature.

Characteristic of Dams

dams

  • A dam is different from other civil engineering buildings.
  • The dam is a mass of building material in large numbers in a limited area so that there will be a very large pressure load on the underground.
  • The destructive impact of water in the reservoir on the foundation and on the dam itself, so that leakage, erosion, and even collapse of the structure can occur.
  • A dam is always built in a valley.
  • A dam made of concrete according to several requirements regarding soil mass, because the soil mass will bear almost all the shear stresses that arise, and should not show a significant differential decrease, because the sturdy building structure can collapse.

Geological factors that determine the choice of a dam are:

  • The foundation and shoulder-wall must be made of good quality rock and can withstand expected stresses (static or dynamic).
  • The foundation mass must be able to withstand shear stresses and not show a differential decline, preferably the geological state of the development land shows uniformity.
  • Rock material in soil masses must be able to withstand weathering, freezing symptoms, dissolving symptoms, and erosion.
  • Rocks in the construction site must be waterproof.
  • The technical-geological properties of the surrounding rock should be suitable for the construction of various facilities such as tunnel overflow channels for various power stations, etc

The various styles that can work on dams are:

1). Static force

a. Vertical
  • The mass of the dam
  • Water + sediment that settles in the reservoir
  • Upward force from the part of the dam which is located underwater
b. Horizontal
  • Lateral pressure by water + sediment in the reservoir
  • Ice (not a big problem because the ice melts plastic)
  • Pore pressure, acting on the foundation

2). Dynamic style

  1. Wave action by water in the reservoir
  2. Flood
  3. Shock caused by an earthquake

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