Stepped Chute Spillways: Difference between revisions
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Stepped chute [[spillways]] are suited for service and [[Auxiliary Spillways|auxiliary spillways]]. Stepped spillways refer to the stepped chute portion of the spillway and have primarily been used with roller-compacted concrete (RCC) dams, which take advantage of the RCC lift [[construction]] methods, resulting in offsets on the downstream dam face, creating the spillway steps. These steps can be formed or unformed RCC or capped with conventional concrete. A chute-type crest (flat), along with straight or curved ogee crests, are typically used in combination with stepped chutes. Other applications have involved incorporating both smooth flow surfaces and steps into a [[Reinforced Concrete|reinforced concrete]] spillway chute and RCC [[Overtopping Protection|overtopping protection]] for an earth dam. A consideration for a stepped spillway involves the potential kinetic [[Energy Dissipation|energy dissipation]] via the steps, which can reduce the size and type of the terminal structure. However, the kinetic [[Energy Dissipation|energy dissipation]] potential may be reduced as flow depth (relative to the step size) increases (due to skimming flows). Also, consideration should be given to evaluating the [[cavitation]] potential. Examples of stepped spillways include the service spillway at Maricopa Water District’s Camp Dyer Diversion Dam (concrete), the auxiliary spillway (Joint Federal Project) at Reclamation’s Folsom Dam (composite), and the service spillway at Reclamation’s Upper Stillwater Dam (concrete). <ref name="DS14">[[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, 2022]]</ref> | Stepped chute [[spillways]] are suited for service and [[Auxiliary Spillways|auxiliary spillways]]. Stepped spillways refer to the stepped chute portion of the spillway and have primarily been used with roller-compacted concrete (RCC) dams, which take advantage of the RCC lift [[construction]] methods, resulting in offsets on the downstream dam face, creating the spillway steps. These steps can be formed or unformed RCC or capped with conventional concrete. A chute-type crest (flat), along with straight or curved ogee crests, are typically used in combination with stepped chutes. Other applications have involved incorporating both smooth flow surfaces and steps into a [[Reinforced Concrete|reinforced concrete]] spillway chute and RCC [[Overtopping Protection|overtopping protection]] for an earth dam. A consideration for a stepped spillway involves the potential kinetic [[Energy Dissipation|energy dissipation]] via the steps, which can reduce the size and type of the terminal structure. However, the kinetic [[Energy Dissipation|energy dissipation]] potential may be reduced as flow depth (relative to the step size) increases (due to skimming flows). Also, consideration should be given to evaluating the [[cavitation]] potential. Examples of stepped spillways include the service spillway at Maricopa Water District’s Camp Dyer Diversion Dam (concrete), the auxiliary spillway (Joint Federal Project) at Reclamation’s Folsom Dam (composite), and the service spillway at Reclamation’s Upper Stillwater Dam (concrete). <ref name="DS14">[[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, 2022]]</ref> | ||
Revision as of 21:59, 22 January 2025
|
| Physical model of the stepped spillway for the Gross Reservoir Expansion project.
(Image Source: CO DWR) |
Stepped chute spillways are suited for service and auxiliary spillways. Stepped spillways refer to the stepped chute portion of the spillway and have primarily been used with roller-compacted concrete (RCC) dams, which take advantage of the RCC lift construction methods, resulting in offsets on the downstream dam face, creating the spillway steps. These steps can be formed or unformed RCC or capped with conventional concrete. A chute-type crest (flat), along with straight or curved ogee crests, are typically used in combination with stepped chutes. Other applications have involved incorporating both smooth flow surfaces and steps into a reinforced concrete spillway chute and RCC overtopping protection for an earth dam. A consideration for a stepped spillway involves the potential kinetic energy dissipation via the steps, which can reduce the size and type of the terminal structure. However, the kinetic energy dissipation potential may be reduced as flow depth (relative to the step size) increases (due to skimming flows). Also, consideration should be given to evaluating the cavitation potential. Examples of stepped spillways include the service spillway at Maricopa Water District’s Camp Dyer Diversion Dam (concrete), the auxiliary spillway (Joint Federal Project) at Reclamation’s Folsom Dam (composite), and the service spillway at Reclamation’s Upper Stillwater Dam (concrete). [1]
Best Practices Resources
Roller-Compacted Concrete (EM 1110-2-2006), USACE
Trainings
On-Demand Webinar: Stepped Chute Spillway Design for Embankment Dams
On-Demand Webinar: RCC Applications in Dam Engineering - What We Have Learned and What's New
On-Demand Webinar: Roller Compacted Concrete - Design and Construction of Water Control Structures
Citations:
Revision ID: 8159
Revision Date: 01/22/2025