Uplift Considerations for Concrete Gravity Dams

Abstract Only - Uplift forces along foundation joints or improperly bonded concrete joints are a widely recognized contributor to failure modes for concrete gravity dams. The industry-wide inclusion of uplift forces in the design and evaluation of concrete dams was predated by several dam failures (e.g., Bouzey Dam, Austin Dam) that can be at least partially attributed to the lack of understanding of these forces. Over the decades following these failures, significant provisions (e.g., foundation grouting, foundation drains) have been incorporated into dam safety guidelines to prevent similar failures of dams designed to modern standards. Even so, the recent crack at Wanapum Dam and piping under Camara Dam further highlight the need to understand and design against the potential uplift forces that can develop along weak planes in concrete dams and foundations.

This presentation will provide a summary of the current state-of-the-practice in application of uplift forces on concrete dams, as summarize in the paper of the same name in the latest issue of ASDSO’s Journal of Dam Safety. This summary will include the most recent federal and state guidelines and standards used in design and evaluation of concrete dams, including FERC, Reclamation, and USACE guidelines. Particular attention will be given to clarifying application of uplift pressures for concrete dams with foundation and body drains, and to methods for adjusting uplift pressures for flood, earthquake, and post-earthquake loading. The summary will also include a literature review into research related to understanding uplift pressures acting on dams for various foundation and drain conditions, and a summary of discussions held during a 90 minute panel discussion at ASDSO’s Dam Safety 2016. Case studies will also be presented to highlight the differences in interpretation of the current guidelines. The presentation will conclude with questions to the general audience regarding the different interpretations.