Overview - Overtopping Protection for Concrete Dams

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Overview - Overtopping Protection for Concrete Dams

Concrete Dam Overtopping• While most concrete dams can likely withstandovertopping flows due to their rock foundations,some may be vulnerable due to jointing andfracturing in the rock abutments and d/s toe, or dueto erodibility of softer rock foundations• Consider magnitude and duration of overtopping• Appurtenant structures may require protection fromovertopping flows, such as a powerplant or outletworks control house at downstream toe of dam• Evaluate any potential hydrologic failure modes2


Approaches to Protection• Methods used to analyze and address theimpacts of overtopping on embankmentand concrete dams differ greatly• Concrete dams are naturally resistant toerosion, but may be susceptible to stabilityconcerns due to higher reservoir heads orweaknesses in the foundation• Fewer types of overtopping protectionalternatives are generally available


Technical Manual Overview• Part 2 – Concrete Damso Chapter 11 – Generalo Chapter 12 – Roller-Compacted Concreteo Chapter 13 – Conventional and Mass Concreteo Chapter 14 – Foundation and AbutmentReinforcingo Chapter 15 – Tailwater Pool Technologieso Chapter 16 – Concrete Dam Summary


Technical Seminar OutlineOvertopping Protection for Concrete Dams• RCC and Conventional Concrete• Foundation and Abutment Reinforcing• Computational Fluid Dynamics (CFD) forOvertopping Evaluation


Technical Manual Case StudiesRCC Buttresses for Concrete Dams:• Camp Dyer Diversion Dam, AZ– Crest raise for straight masonry gravity dam– RCC overtopped within 8 months of completion• Santa Cruz Dam, NM– Seismic stability for curved concrete arch dam• Pueblo Dam, CO– Sliding stability for concrete spillway structure


Camp Dyer Diversion Dam


Santa Cruz Dam


Pueblo Dam


Technical Manual Case StudiesConventional Concrete for Concrete Dams:• Gibson Dam, MT– Concrete protection and abutmentreinforcement for arch dam• Coolidge Dam, AZ– Concrete protection for dome/buttress dam• Stony Gorge Dam, CA– Concrete protection for slab/buttress dam(right abutment only)


Coolidge Dam


Stony Gorge Dam


Technical Manual Case StudiesPlunge Pool for Concrete Dams:• Theodore Roosevelt Dam, AZ– Unlined excavated pool for gated spillwaydischarges


Excavated Plunge PoolsTheodore Roosevelt Dam, AZ


Impinging Jets in TailwaterHydraulics of free fallingjets may produce:• Rock erosion• Brittle fracture• Fatigue failure• Plucking failure• Dispersal in pool withno effect on foundation


Stream Power vs Erosion IndexDamageNo Damage


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