Spillway Chute Hydraulics: Difference between revisions
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[[Category:Hydraulic Performance of Spillways]] | [[Category:Hydraulic Performance of Spillways]] | ||
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|caption= Water rushing out one of the chute spillways at the Mosul Dam. | |||
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“The chute is that portion of the spillway which connects the crest curve to the terminal structure. The term chute when used in conjunction with a spillway implies that the velocity is supercritical; thus, the Froude number is greater than one. When the spillway is an integral part of a concrete gravity monolith, the chute is usually very steep. Chutes as steep as 1.0 vertical on 0.7 horizontal are not uncommon. The steepness thus minimizes the chute length. Chutes used in conjunction with [[Embankment Dams|embankment dams]] often must be long with a slope slightly steeper than the critical slope. This long, prominent structure is termed a chute spillway. The designs for long spillway chutes and steep chutes on concrete dam monoliths involve many of the same geometric and hydraulic considerations. Due to the extreme slope and short length of a steep chute, many of the hydraulic characteristics that become prominent in spillway chutes have insufficient time to develop prior to reaching the terminal structure.” <ref name="EM110-2-1603">[[Hydraulic Design of Spillways (EM 1110-2-1603) | Hydraulic Design of Spillways (EM 1110-2-1603), USACE, 1992]]</ref> | “The chute is that portion of the spillway which connects the crest curve to the terminal structure. The term chute when used in conjunction with a spillway implies that the velocity is supercritical; thus, the Froude number is greater than one. When the spillway is an integral part of a concrete gravity monolith, the chute is usually very steep. Chutes as steep as 1.0 vertical on 0.7 horizontal are not uncommon. The steepness thus minimizes the chute length. Chutes used in conjunction with [[Embankment Dams|embankment dams]] often must be long with a slope slightly steeper than the critical slope. This long, prominent structure is termed a chute spillway. The designs for long spillway chutes and steep chutes on concrete dam monoliths involve many of the same geometric and hydraulic considerations. Due to the extreme slope and short length of a steep chute, many of the hydraulic characteristics that become prominent in spillway chutes have insufficient time to develop prior to reaching the terminal structure.” <ref name="EM110-2-1603">[[Hydraulic Design of Spillways (EM 1110-2-1603) | Hydraulic Design of Spillways (EM 1110-2-1603), USACE, 1992]]</ref> | ||
“Hydraulic characteristics that must be considered in the design of a chute are the velocity and depth of flow, air entrainment of the flow, pier and abutment waves, floor and wall pressures, [[cavitation]] indices, superelevation of the flow surface at curves, and standing waves due to the geometry of the chute. Obtaining acceptable hydraulic characteristics is dependent upon developing proper geometric conditions that include chute floor slope changes, horizontal alignment changes (curves), and sidewall convergence… A model study is recommended to confirm any design that involves complex geometric considerations and/or large discharges and velocities.” <ref name="EM110-2-1603"> | “Hydraulic characteristics that must be considered in the design of a chute are the velocity and depth of flow, air entrainment of the flow, pier and abutment waves, floor and wall pressures, [[cavitation]] indices, superelevation of the flow surface at curves, and standing waves due to the geometry of the chute. Obtaining acceptable hydraulic characteristics is dependent upon developing proper geometric conditions that include chute floor slope changes, horizontal alignment changes (curves), and sidewall convergence… A model study is recommended to confirm any design that involves complex geometric considerations and/or large discharges and velocities.” <ref name="EM110-2-1603"/> | ||
Spillway chutes do not have to be designed with parallel sidewalls. Chutes commonly are designed and constructed with either diverging or converging sidewalls for a variety of site-specific reasons. “The height of a chute sidewall should be designed to contain the flow of the spillway design flood… The computed profile may require adjustment to account for the effects of pier end waves, slug flow or roll waves, and air entrainment. Sidewall freeboard is added above the adjusted profile; as a minimum, two feet of freeboard is recommended.” <ref name="EM110-2-1603"/> | |||
See also: [[Anatomy of Dams]] > [[Water Conveyance]] > [[Spillways]] > [[Uncontrolled Spillways]] > [[Chute Spillways]] | |||
==Examples== | ==Examples== | ||
{{Website Icon}} [https://damfailures.org/case-study/el-guapo-dam-venezuela-1999/ Learn about the importance of adequate chute | {{Website Icon}} [https://damfailures.org/case-study/oroville-dam-california-2017/ Learn about the importance of spillway chute design and construction from the incident at Oroville Dam (DamFailures.org)] | ||
{{Website Icon}} [https://damfailures.org/case-study/el-guapo-dam-venezuela-1999/ Learn about the importance of adequate hydraulic capacity of a spillway chute from the failure of El Guapo Dam (DamFailures.org)] | |||
==Best Practices Resources== | |||
{{Document Icon}}[[Design Standards No. 14: Appurtenant Structures for Dams (Ch. 3: General Spillway Design Considerations) | Design Standards No. 14: Appurtenant Structures for Dams (Ch. 3: General Spillway Design Considerations), USBR | {{Document Icon}}[[Design Standards No. 14: Appurtenant Structures for Dams (Ch. 3: General Spillway Design Considerations) | Design Standards No. 14: Appurtenant Structures for Dams (Ch. 3: General Spillway Design Considerations), USBR]] | ||
{{Document Icon}} [[Technical Release 210-60: Earth Dams and Reservoirs | Technical Release 210-60: Earth Dams and Reservoirs, NRCS | {{Document Icon}} [[Technical Release 210-60: Earth Dams and Reservoirs | Technical Release 210-60: Earth Dams and Reservoirs, NRCS]] | ||
{{Document Icon}} [[National Engineering Handbook: Chapter 50 - Earth Spillway Design | National Engineering Handbook: Chapter 50 - Earth Spillway Design, NRCS | {{Document Icon}} [[National Engineering Handbook: Chapter 50 - Earth Spillway Design | National Engineering Handbook: Chapter 50 - Earth Spillway Design, NRCS]] | ||
{{Document Icon}}[[Hydrologic Engineering Requirements for Reservoirs (EM 1110-2-1420) | Hydrologic Engineering Requirements for Reservoirs (EM 1110-2-1420), USACE | {{Document Icon}}[[Hydrologic Engineering Requirements for Reservoirs (EM 1110-2-1420) | Hydrologic Engineering Requirements for Reservoirs (EM 1110-2-1420), USACE]] | ||
{{Document Icon}} [[Hydraulic Design of Spillways (EM 1110-2-1603) | Hydraulic Design of Spillways (EM 1110-2-1603), USACE | {{Document Icon}} [[Hydraulic Design of Spillways (EM 1110-2-1603) | Hydraulic Design of Spillways (EM 1110-2-1603), USACE]] | ||
{{Document Icon}} [[Cavitation in Chutes and Spillways (EM 42) | Cavitation in Chutes and Spillways (EM 42), USBR | {{Document Icon}} [[Cavitation in Chutes and Spillways (EM 42) | Cavitation in Chutes and Spillways (EM 42), USBR]] | ||
==Trainings== | ==Trainings== | ||
Latest revision as of 15:59, 25 July 2023
|
| Water rushing out one of the chute spillways at the Mosul Dam.
(Image Source: USACE) |
“The chute is that portion of the spillway which connects the crest curve to the terminal structure. The term chute when used in conjunction with a spillway implies that the velocity is supercritical; thus, the Froude number is greater than one. When the spillway is an integral part of a concrete gravity monolith, the chute is usually very steep. Chutes as steep as 1.0 vertical on 0.7 horizontal are not uncommon. The steepness thus minimizes the chute length. Chutes used in conjunction with embankment dams often must be long with a slope slightly steeper than the critical slope. This long, prominent structure is termed a chute spillway. The designs for long spillway chutes and steep chutes on concrete dam monoliths involve many of the same geometric and hydraulic considerations. Due to the extreme slope and short length of a steep chute, many of the hydraulic characteristics that become prominent in spillway chutes have insufficient time to develop prior to reaching the terminal structure.” [1]
“Hydraulic characteristics that must be considered in the design of a chute are the velocity and depth of flow, air entrainment of the flow, pier and abutment waves, floor and wall pressures, cavitation indices, superelevation of the flow surface at curves, and standing waves due to the geometry of the chute. Obtaining acceptable hydraulic characteristics is dependent upon developing proper geometric conditions that include chute floor slope changes, horizontal alignment changes (curves), and sidewall convergence… A model study is recommended to confirm any design that involves complex geometric considerations and/or large discharges and velocities.” [1]
Spillway chutes do not have to be designed with parallel sidewalls. Chutes commonly are designed and constructed with either diverging or converging sidewalls for a variety of site-specific reasons. “The height of a chute sidewall should be designed to contain the flow of the spillway design flood… The computed profile may require adjustment to account for the effects of pier end waves, slug flow or roll waves, and air entrainment. Sidewall freeboard is added above the adjusted profile; as a minimum, two feet of freeboard is recommended.” [1]
See also: Anatomy of Dams > Water Conveyance > Spillways > Uncontrolled Spillways > Chute Spillways
Examples
Best Practices Resources
Technical Release 210-60: Earth Dams and Reservoirs, NRCS
National Engineering Handbook: Chapter 50 - Earth Spillway Design, NRCS
Hydrologic Engineering Requirements for Reservoirs (EM 1110-2-1420), USACE
Hydraulic Design of Spillways (EM 1110-2-1603), USACE
Cavitation in Chutes and Spillways (EM 42), USBR
Trainings
On-Demand Webinar: Intro to Cavitation in Chutes and Spillways
On-Demand Webinar: Designing Spillways to Mitigate Failure Modes
Citations:
Revision ID: 7458
Revision Date: 07/25/2023