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Outlet Structure Drain Systems at Twin Lakes and Sugar Loaf Dams
The spillway and outlet works facilities for many embankment dams include stilling basin structures to dissipate flow energy. Stilling basins can range from simple riprap basins to large concrete basins, designed to create loss of energy through a turbulent hydraulic jump. Design of the concrete chute and stilling basin structures often includes underdrain systems. These systems relieve uplift pressures and reduce the potential for chute and stilling basin flotation during intended and unintended unwatered conditions. However, these underdrains can be susceptible to flaws such as settlement, poor pipe design or material, poor filter design, and construction damage. Flaws which result in open joints, tears, or other damage can create an unfiltered exit for internal erosion at the dam toe. This case history describes the design, construction conditions, inspections, and subsequent actions for the underdrain systems at Twin Lakes and Sugar Loaf Dams in Colorado. These two dams, located in similar geologic terrain, have exhibited signs of material movement through the outlet works and spillway chute and stilling basin underdrain systems resulting in investigations at both facilities. Corrective actions were performed at Twin Lakes Dam and future corrective actions are currently being evaluated for Sugar Loaf Dam.
Outlet Structure Drain Systems at Twin Lakes and Sugar Loaf Dams
The spillway and outlet works facilities for many embankment dams include stilling basin structures to dissipate flow energy. Stilling basins can range from simple riprap basins to large concrete basins, designed to create loss of energy through a turbulent hydraulic jump. Design of the concrete chute and stilling basin structures often includes underdrain systems. These systems relieve uplift pressures and reduce the potential for chute and stilling basin flotation during intended and unintended unwatered conditions. However, these underdrains can be susceptible to flaws such as settlement, poor pipe design or material, poor filter design, and construction damage. Flaws which result in open joints, tears, or other damage can create an unfiltered exit for internal erosion at the dam toe. This case history describes the design, construction conditions, inspections, and subsequent actions for the underdrain systems at Twin Lakes and Sugar Loaf Dams in Colorado. These two dams, located in similar geologic terrain, have exhibited signs of material movement through the outlet works and spillway chute and stilling basin underdrain systems resulting in investigations at both facilities. Corrective actions were performed at Twin Lakes Dam and future corrective actions are currently being evaluated for Sugar Loaf Dam.
Outlet Structure Drain Systems at Twin Lakes and Sugar Loaf Dams
Bergstrom, Eric (author)
Rocky Mountain Geo-Conference 2018 ; 2018 ; Golden, Colorado
Rocky Mountain Geo-Conference 2018 ; 103-116
2018-11-01
Conference paper
Electronic Resource
English
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