Multipurpose Reservoirs

Multipurpose Reservoirs: DamsThe most common types of dams are: Gravity Dam Arch Dam Earth Embankment Dam Roller Compacted Dam

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Gravity DamBasically, gravity dams are solid concrete structures that maintain their stability against design loads from the geometric shape and the mass and strength of the concrete. Generally, they are constructed on a straight axis, but may be slightly curved or angled to accommodate the specific site conditions. Gravity dams typically consist of a nonoverflow section(s) and an overflow section or spillway. The two general concrete construction methods for concrete gravity dams are conventional placed mass concrete and RCC.




More information is available by accessing the EM for this feature:EM 1110-2-2200: Engineering and Design - Gravity Dam Design

Arch DamAn Arch Dam is typically constructed in a location with Canyon walls and takes advantage of the arch action in the dam to transfer the forces in the dam to the rock canyon walls as well as the base. The design and shape of the dam is determined by the site conditions and the steepness and width of the canyon walls. The use of the arch action reduces the amount of concrete required to carry the load and is most commonly used for high head dams in deep canyons.



More information is available by accessing the EM for this feature:EM110-2-2201: Engineering and Design - Arch Dam Design

Earth Embankment DamThe typical Earth Embankment Dam has several feature shown here. An earth embankment constructed of compacted fill materials depending on the site conditions and foundation material to preclude and or control seepage of the water through and under the dam. Various design examples are shown on the sketches that follow. In addition, an emergency spillway is provided to pass large quantities of water during floods to prevent overtopping of the dam. Finally, a control house operates a set of gates which controls the amount of water passing through the outlet works to maintain flow in the river downstream of the dam during normal operations of the dam.

Hover over image to enlarge.More information is available by accessing the EM for this feature:EM 1110-2-2300: Engineering and Design - General Design and Construction Considerations For Earth and Rock-Fill Dams

Central CoreFor earthen dams constructed on an impervious rock foundation a center impervious core with a connected vertical and horizontal drainage system is ofter used tyo control the seepage through the dam


InclinedFor Earthen dams constructed on an impervious rock foundation, and impervious layer of material along with a sloped drainage system is used to control the seepage through the dam. This design is often used when the core material in the dam is of a high, semi-impervious quality.


HomogeneousWhen an earthen dam is constructed on a pervious layer of material which is too extensive to excavate, a slurry cutoff wall is often constructed on the upstream part of the dam connected to an impervious section of the dam. Under-seepage in this case is minimized in the foundation and through seepage in controlled by a sloped and horizontal system of grains in the embankment.


Pervious FoundationAnother option for control seepage ander and through a dam on a pervious foundation is to excavate the impervious material under the center of the cam and place an impervious core in both the foundation and dam embankment along with a drainage system on the downstream side of the core to collect and control and seepage through the core.


Upstream ImperviousFor Earth dams constructed on a pervious foundation,an upstream impervious layer with an impervious blanket is used to minimize the flow of water through and under the dam. The water which does flow through the dam is collected by a vertical and horizontal drainage system combined with relief wells to control the seepage and transport it to the downstream toe of the dam.

Hover over image to enlarge.Roller Compacted DamRoller Compacted Concrete (RCC)I s "concrete compacted by roller compaction; concrete that, in its unhardened state, will support a roller while being compacted." Properties of hardened RCC can be similar to those of conventionally placed concrete. However, Roller Compacted Concrete can also be made with hardened properties that are outside the range of typical properties of conventionally placed concrete. The term "roller compaction" is defined as "a process for compacting concrete using a roller, often a vibrating roller."



More information is available by accessing the EM for this feature:EM 1110-2-2006: Engineering and Design - Roller-Compacted Concrete

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Multipurpose Reservoirs

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