11 Top Advantages and Disadvantages of Buttress Dams | Parts of a Dam | Types of Dams | Uses of Dams

What is Buttress Dam?  |Advantages and Disadvantages of Buttress Dams | Types of Dams | Uses of Dams | Different Parts of Dams

What is Buttress Dam?

A buttress dam, also known as a hollow dam, is a dam having a solid, watertight upstream side that is supported on the downstream side by a series of buttresses or supports at regular intervals.

The dam wall can be either straight or curved. The majority of buttress dams are constructed of reinforced concrete and are heavy, causing the dam to sink into the ground. Water pushes against the dam, yet the buttresses are rigid and keep the dam from collapsing.

Buttress or hollow gravity dams were originally built to retain water for cultivation or mining in locations where resources were few or expensive but labor was cheap.

In vast valleys where solid rock is scarce, a buttress dam is an excellent alternative.

The strengths and weaknesses of buttress dams have become clear as designs have become more advanced. The Romans were the first to utilize buttresses to strengthen dam walls.

With the patented technology of Norwegian-American civil engineer Nils F. Ambursen, buttress dams of slab concrete construction became popular in the United States in the early twentieth century.

A buttress dam is a type of dam that uses the weight and force of water to stabilize a slope or side of a valley.

The term “buttress” refers to the way the structure creates support for an adjacent hillside or mountain, like how one would brace oneself against someone’s shoulder.

Buttresses are made from earth-fill, rock fill, concrete slabs, rolled steel joists (RSJs), or other materials.  In order for buttresses to work properly they must be able to withstand pressure from behind as well as any forces coming in contact with them on top.

Most importantly though, they need to be free of leaks in order for them not slide down the hill because water will seep through cracks and holes over time.

Parts of a Dam

There are several parts of a dam. They include;

1. Foundations

It is the part of a dam where the dam is built. There are different foundations that can be used in constructing a dam.

2.Raft:

The raft is the foundation on which concrete or rock fill will be placed to raise the water level so as to ensure that the intake tower can function properly. The raft supports large proportion of the total weight of all materials within a dam.

3. Intake Tower:

The purpose of an intake tower is to draw water into the dam. Intake towers are located on the downstream side of the dam and are used to allow groundwater to pass under the dam.

4.Dam:

The dam is a strong structure made up mainly of concrete or rock fill that can withstand water pressure and heavy loads. It is used in controlling water levels in a reservoir or lake.

5. Parapet walls:

The purpose of the parapet walls is to prevent water from flowing down the dam and damage the foundation. It can also prevent debris from falling into the river.

6. Spillway:

The spillway is an area where a dam’s excess water can flow over and out of its reservoir when the water level drops below a certain level.

7. Powerhouse:

This is an area where electrical generators are placed to produce electricity for local residents or industries in other locations.

8. Abutments:

Abutments are strong walls that are built on the sides of mountains and support the weight of the dam. They can also be made of concrete, rock fill, earth-fill or a combination.

9. End walls:

These walls support the weight of the dam and serve as a barrier to retain water.

10. Rock Tunnel:

The purpose of a rock tunnel is to connect two points underground by drilling through rock while supporting tunnels in unstable areas such as mountains, cliffs or unstable ground

11.Spillway Gate:

A spillway gate is a valve that opens when the water level rises, and closes when the water level lowers. It is used to control the flow of water out of a reservoir or into a river.

12. Diversion Tunnel:

The purpose of a diversion tunnel is to divert water from one site to another.

Buttress dams offer a number of benefits:

1. They are more economical than other types of dams. A buttress dam is usually less expensive to build than other concrete, or thin-shell embankment dams.
2. The cost depends primarily on the structure’s height and the foundation conditions. In comparison with other types, buttress dams also return more benefits for the investment made in them.
3. They are less susceptible to erosion. One of the greatest advantages is that buttress dams are not subject to rapid erosion from the river’s load like other earthfall dams. In addition, these dams do not require large quantities of earthfall or rockfill for construction compared to earthen and embankment dams.
4. They can be built on uneven terrain. Buttress dams offer access to sites that have been difficult to reach due to existing topographic conditions. The buttress structure allows for construction on uneven terrain, which may have required elevating a roadway or constructing a foundation for other types of dams.
5. They can be designed and built without any commitment to the eventual use of the dam site. Most buttress dams are built with no specific purpose in mind. Many times, these are simply meant as a way to provide access to otherwise inaccessible resources.

Advantages and Disadvantages of Buttress Dams

The Advantages of Buttress Dams

• The Buttress dam can be built on a somewhat unstable foundation.
• Buttress dams can be engineered to accommodate moderate levels of foundation movement without causing major damage, allowing them to be erected in soil with differential settlements.
• The amount of concrete necessary for a buttress dam is approximately one-third to one-twelfth of that required for a gravity dam of the same height.
• There are no issues with foundation drainage or uplift.
• The uplift pressure operating on a buttress dam is significantly lower, resulting in savings on concrete and overall dam stability.
• The powerhouse, switchyard, and so on can be built between the buttresses, saving money on construction.

The Disadvantages of a Buttress Dam

• Buttress dams necessitate more labor than solid concrete dams.
• Because the upstream concrete surface is thinner, it is more prone to deterioration.
• It usually requires ongoing maintenance and supervision.
• The dam’s life is shorter than that of other dams.
• Buttress dams need more skilled labor and have a higher shuttering-to-concrete ratio than gravity dams. This could result in a higher unit rate of concrete.
• A buttress dam often requires more water seals to be installed and maintained than other types of dams.

Types of Dams

The following are various dams’ types;

1. Concrete Gravity Dams

Concrete dams are gravity dams that are often made in huge blocks separated by joints to facilitate construction and reduce thermal stress. After the dam has cooled, the joints are grouted. The dam axis is perpendicular to the transverse joints.

Concrete dams are the most cost-effective type of dam. They are usually constructed from reinforced concrete having a wide thickness.

Because they have no moving parts, concrete dams can be used for primary or secondary purposes. They are constructed for utilitarian purposes such as livestock watering troughs, irrigation, environmental management, etc.

2. Rockfill Dams

Rockfill dams are large embankment dams made of rock fill materials or mixtures of sand and gravel. They are constructed in arid regions where concrete is not available.

Rockfill dams with a height ranging from 10 to 100 feet are normally constructed using hand labor. Large rockfill dams, however, require heavy machinery and other advanced construction equipment.

3. Earthfill Dams

Earthfill dams are constructed using soil, sand and gravel. They are usually made of a cement-like mixture of cement and other ingredients.

Earthfill dams with a height ranging from 5 to 80 feet may be constructed using hand labor or by using heavy machinery. As a result, the costs are higher than those of rockfill and concrete types of dams.

4. Gravity Dams

Gravity dams are constructed using earthfill or rockfill materials. They are also made of concrete, metal and pre-cast material.

5. Thin-Shell Dams

Thin-shell dams are used primarily for flood control to store water and allow it to flow over the dam when the river floods. They are constructed with concrete, metal and pre-cast material on a rockfill base.

4.  Arch Dams

Arch dams are used as an alternative to gravity dams. They are constructed of a pre-cast unit. The pre-cast units are inserted into concrete foundations and covered with concrete slabs, while the ribs are attached to the ribbed aggregate cemented concrete foundation.

Uses of Dam

Most Dam are used for:

1. Reservoir:

It is used for the provision of drinking water for domestic and industrial purpose. It can also be used for providing irrigation water to grow crops.

2. Power Generation:

Water from the dam is allowed to flow through a turbine that rotates a generator to produce electricity.

3. Flood Control:

It is used to control flooding in an area by storing excess water in the reservoir and later releasing it when excess rain occurs.

4. Fish Farm:

The water flow from the dam can be used to raise fish

5. Recreational and Tourist Spots

6. Construction of Dams

Conclusion – Dam has various types as per the requirement and region, so choosing right type of dam depends on cost analysis, design requirements for particular regions etc.

Buttress Dam FAQs

1. What is a Dam?

A dam is a hydraulic construction made of relatively impermeable material that is built across a river to form a reservoir on its upstream side for impounding water for a variety of uses such as flood control, hydropower, water supply, irrigation, navigation, fishing, and recreation.

2. What is a Buttress Dam?

Buttress dam is a kind of earth-fill dam. It has the shape of a hollow truncated cone with steep upstream wall and sloping downstream face.

It is a low-cost dam with lower cost per unit area than earth embankment and concrete dams.

3. What are the Types of Buttress Dam?

• Wedge Buttress Dam
• Trapezoidal Buttress Dam
• Thin-shell buttress dam

 4. What are the Main Advantages of Buttress Dam?

Buttress type dams are typically non-structural, which means they don’t require a large concrete pour to withstand internal pressure.

5. What are the Disadvantages of Buttress Dam?

Partial blocking of natural streamflow can create problems upstream during flooding events.

6. What is the Role of PWD in Dam Construction?

Maintenance of existing dams and construction of new dams

7. What are Various Purposes of Dam Construction?

Water supply: The reservoirs hold water for agricultural or industrial use. The dam also provides water for drinking and industrial purposes as well as for fishing and recreation activities.

• Power generation: An impounded reservoir is used to drive a turbine to generate power. Many hydroelectric schemes have been built throughout the world with dams at some location in their catchment area.
• Irrigation: The impounded water can also be used to provide water for irrigation.
• Flood control: A dam can also be used to hold back flood-waters and release them slowly in order to minimize the downstream flooding. Dam foundations and embankments help in flood control by preventing the river from shifting its course by silt deposition. They provide temporary storage during floods, thus reducing the adverse effects of floods.

8. How Dam is constructed?

Construction of embankment mass comprising of suitable aggregate and soil.

Erection of structural works to support the embankment mass/ foundation and to house spillway gates and/or other appurtenances.

9. What are the Uses of Dam?

• Water supply: The reservoirs hold water for agricultural or industrial use. The dam also provides water for drinking and industrial purposes as well as for fishing and recreation activities.
• Power generation: An impounded reservoir is used to drive a turbine to generate power. Many hydroelectric schemes have been built throughout the world with dams at some location in their catchment area.
• Irrigation: The impounded water can also be used to provide water for irrigation.
• Flood control: A dam can also be used to hold back flood-waters and release them slowly in order to minimize the downstream flooding. Dam foundations and embankments help in flood control by preventing the river from shifting its course by silt deposition. They provide temporary storage during floods, thus reducing the adverse effects of floods.

Gravity Dam

1. What is a Gravity Dam?

A gravity dam is an earth-fill dam with steeper upstream face than downstream face.

2. What are the Main Advantages of the Gravity Dam?

It is simple to construct (it uses no machinery). It is stable as it does not move due to gravity pressure. It can be constructed in a short time. The resultant high water of the reservoir lets you make several small reservoirs and supply water for irrigation and drinking to nearby areas. It is also low cost compared to other types of dams.

3. What are the Main Disadvantages of the Gravity Dam?

It does not have any protection against flow, so it is vulnerable to erosion, while large fines caused by erosion can cause floods downstream which may submerge surrounding areas without warning.

4. What is the Purpose of the Gravity Dam?

The purpose of the gravity dam is to provide artificial lakes with water for irrigation and other purposes and protect itself against floods by holding back the water behind it. The capacity of a gravity dam will depend on its height and width of course as well as its depth.

5. What are the Uses of the Gravity Dam?

• Water supply: The reservoirs hold water for agricultural or industrial use. The dam also provides water for drinking and industrial purposes as well as for fishing and recreation activities.
• Power generation: An impounded reservoir is used to drive a turbine to generate power. Many hydroelectric schemes have been built throughout the world with dams at some location in their catchment area.
• Irrigation: The impounded water can also be used to provide water for irrigation.
• Flood control: A dam can also be used to hold back flood-waters and release them slowly in order to minimize the downstream flooding. Dam foundations and embankment help in flood control by preventing the river from shifting its course by silt deposition. They provide temporary storage during floods, thus reducing the adverse effects of floods.

Embankment Dam

1. What is an Embankment Dam?

An embankment dam is an earth-fill dam with a very high upstream face and a low downstream face. The upstream face is usually raised above the downstream face to provide better protection against erosion.

2. What are the Main Advantages of the Embankment Dam?

It provides good protection against floods. It is stable as it does not move due to gravity pressure. It can be constructed in a short time. The resultant high water of the reservoir lets you make several small reservoirs and supply water for irrigation and drinking to nearby areas. It is also low cost compared to other types of dams.

3. What are the Main Disadvantages of the Embankment Dam?

It does not have any protection against flow, so it is vulnerable to erosion, while large fines caused by erosion can cause floods downstream which may submerge surrounding areas without warning.

4. What is the Purpose of the Embankment Dam?

The purpose of an embankment dam is to provide artificial lakes with water for irrigation and other purposes and protect itself against floods by holding back the water behind it. The capacity of an embankment dam will depend on its height and width of course as well as its depth.

5. What are the Uses of the Embankment Dam?

• Water supply: The reservoirs hold water for agricultural or industrial use. The dam also provides water for drinking and industrial purposes as well as for fishing and recreation activities.
• Power generation: An impounded reservoir is used to drive a turbine to generate power. Many hydroelectric schemes have been built throughout the world with dams at some location in their catchment area.
• Irrigation: The impounded water can also be used to provide water for irrigation.
• Flood control: A dam can also be used to hold back flood-waters and release them slowly in order to minimize the downstream flooding. Dam foundations and embankment help in flood control by preventing the river from shifting its course by silt deposition. They provide temporary storage during floods, thus reducing the adverse effects of floods.

An earth-fill dam is usually designed in such a manner that the upstream face is of very steep slope and the downstream face is nearly flat or of gentle slope

But, this type of it may be difficult to construct. In order to protect itself against flowing water pressure, an earth-fill dam may also be provided with a vertical wall or a membrane along its crest.

Concrete Dam

1. What is a Concrete Dam?

A concrete dam is an arch dam constructed with reinforced concrete. The main advantage of this dam is that, it can be constructed as per the shape desired.

The concrete dam is built in a trench excavated in rock and soil. Steel or concrete beams are placed in the trench first.

A layer of cement grout is spread over this beam and stones, boulders, sand, etc are then placed above it. This layer also acts as reinforcement for the entire structure.

Layers of cement grout and stones are added until the height of the dam is increased by 10 to 15 meters.

Another useful advantage of concrete dam is that the reservoir water can be increased at a relatively lower cost.

2. What are the Main Advantages of the Concrete Dam?

The main advantage of a concrete dam is that it can be constructed as per your desired shape but it has an average life span.

A concrete dam needs skilled labour and a large area for its construction, which increases its cost proportionately.

3. What are the Main Disadvantages of the Concrete Dam?

The main disadvantage of a concrete dam is that it has an average life span only (20 to 30 years). It needs skilled labor and large area for its construction, which increases its cost proportionately.

4. What is the Purpose of the Concrete Dam?

A concrete dam is built in order to provide water for drinking, irrigation and making other useful purposes like fishing ponds, hotels, etc.

5. What are the Uses of the Concrete Dam?

• Water supply: The reservoirs hold water for agricultural or industrial use. The dam also provides water for drinking and industrial purposes as well as for fishing and recreation activities.
• Power generation: An impounded reservoir is used to drive a turbine to generate power. Many hydroelectric schemes have been built throughout the world with dams at some location in their catchment area.
• Irrigation: The impounded water can also be used to provide water for irrigation.