1 / 27

Uplift Considerations for Concrete Dams: Current Guidelines & Recommendations

Explore uplift guidelines for concrete dams with a focus on normal operations, flood loading, earthquakes, and post-earthquake scenarios. Learn about drain efficiency, crack variations, and stability evaluations. Gain insights from industry experts and ongoing research.

margaretstein
Download Presentation

Uplift Considerations for Concrete Dams: Current Guidelines & Recommendations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. UPLIFT CONSIDERATIONS FOR CONCRETE DAMS New Mexico Watershed and Dam Owners Coalition Albuquerque– May 3, 2019 Amanda Lopez, PE – AECOM

  2. Acknowledgements Co-authors – Scott Jones and Larry Nuss Original Presentation and Panel discussion at ASDSO Dam Safety, Philadelphia, September, 2016 Panelists: Larry Nuss – Nuss Engineering Alex Grenoble – HDR Robert Hall – Retired, U.S. Army Corps of Engineers Guy Lund – Gannett Fleming Full article published in the Journal of Dam Safety, Volume 15, Issue 2, 2017

  3. Safety Moment Be aware of signs of fatigue Head drooping Lack of attention How to handle fatigue Take a break Stand up and stretch Switch drivers

  4. Introduction Review of Uplift Recommendations from Guidelines and Research Summary of Panel Discussion and Audience Questions at Dam Safety 2016 Conclusions from Panel Discussion

  5. Current Guidelines Application of Uplift for Normal Operations Similar among all agencies From USACE EM 1110-2-2100 From Chapter 3 of FERC Guidelines

  6. Current Guidelines Application of Uplift with Drains FERC – must have maintenance and inspection program plus monitoring to allow uplift reduction Reclamation – drain efficiency for design limited to 66% USACE – drain efficiency of 50% for design unless otherwise approved

  7. Current Guidelines Application of Uplift for Flood Loading FERC – allows extrapolation of drain efficiency for higher reservoir levels on a case-by-case basis with supporting field data USACE – if uplift pressures are known, they can be extrapolated to pool levels for stability evaluations and must represent various pool levels under differing temperatures

  8. Current Guidelines Application of Uplift during an Earthquake Relatively consistent across agencies Uplift pressures are not increased during a seismic event from normal conditions “Seismic Structural Stability of Concrete Gravity Dams Considering Transient Uplift Pressures in Cracks,” by Farrokh Javanmardi, Leger, and Tinawi, Engineering Structures 25 (2005) 616-628.

  9. Current Guidelines Application of Uplift for Post-earthquake Loading FERC – must consider effects of apron cracking and increases in silt pressure and uplift due to liquefaction of reservoir silt Reclamation – stability could be different whether the drains are still functioning All – stability under post-earthquake loading must consider damage likely to result from the earthquake and full uplift pressure along the crack length. From USACE EM 1110-2-6053

  10. Current Guidelines Application of Uplift with Drains and Cracked Base (University of Colorado Research) uplift pressures vary linearly from the reservoir head to the drain, followed by a slight increase in head from the drain to the end of the crack (Amadei, et al)

  11. Uplift Variation Along an Open Crack with 66% Efficient Drains in Dam Crack downstream from drain Crack at toe Crack at drain Crack near toe Crack upstream from drain No crack Reclamation Corps of Engineers FERC University of Colorado

  12. Summary ofPanel Discussion

  13. Goal of Session Make progress towards a common methodology for application of uplift pressures in the stability analysis of concrete dams

  14. When can drain efficiency be included in the evaluation of the stability of the dam? How does uplift vary in differing rock?

  15. What level of instrumentation is required to justify drain efficiency in a stability evaluation? How does one establish drain efficiency based on limited piezometer data? 

  16. How does uplift vary as a crack forms during an earthquake?

  17. How does uplift vary in an earthquake-induced crack which goes back into compression post-seismic?   

  18. What level of drain efficiency can be assumed when computations indicate the crack will extend near or beyond the line of drains? “Estimating Uplift in Cracks in Concrete Dams”, Amadei, Illangasekare, Chinnaswamy, and Morris, Proceedings of the International Conference on HydroPower, Denver, CO, July 1991.

  19. What level of drain efficiency can be assumed for flood conditions beyond those that have been historically observed?  

  20. What methods can be used to establish drain efficiency based on historic instrumentation readings?    

  21. Summary ofAudience Questions to Panel

  22. Is it useful to monitor the discharge at the drains?

  23. Are you as concerned about uplift on thin arch dams as gravity dams?

  24. Does grouting eliminate the need for drains? Does anyone think drainage does not improve stability?

  25. Conclusions A combination of drains and grout curtains is important. Uplift forces are highly dependent on the foundation Piezometer readings should not be extrapolated unless there is data associated with a varying reservoir level. There is uncertainty surrounding seismic loading in regard to applied uplift pressures during the earthquake and post-earthquake. The stability of a concrete dam must be understood with full uplift even when data shows reduced pressures.

  26. It’s all about the… Environmental Engineer – …impacts. Geotechnical Engineer – …soil. Hydrologic and Hydraulics Engineer – …water. Geologist – …foundation. Structural Engineer – …concrete. Reality – It all must work together

  27. Questions?

More Related