Dam Safety 2019: Technical Workshop - Gravity Dams and Assessing Their Safety

When: Thursday, September 12 - 8:30 am - 4:30 pm

Registration Fees: $300 per person includes all course instruction and materials as well as beverage breaks. 

Professional Development Hours: Up to 7 professional development hours are available for attending the full workshop. Attendees will receive a form on which to record contact hours for continuing education credits.

Description: In the last 5 years there have been two incidents on the Columbia River in Washington regarding the stability of different concrete gravity dams. Both incidents appear to have developed during normal loading conditions. In 2019, during heavy winter snows and the subsequent runoff, a concrete spillway structure fails in north central Nebraska. Neither the Washington nor Nebraska projects are overly complex, and the loads that caused these situations are not considered “extreme”. So, what happened? How can such serious situations develop from simple structures, and how is it that these structures operated for decades without someone identifying the potential problem?

Concrete dams have a long history in water resources. The science behind these structures really developed in the nineteenth and early twentieth century. Thus, many mass concrete gravity dams were designed and constructed many years ago. Today, roller compacted concrete has become the material of choice, and while the material and construction methods may be different, the science has remained the same. Therefore, it is as important as ever, to reinvest in our understanding of these structures, so that we can be better stewards of the infrastructure before us.

The purpose of this workshop is to provide a brief introduction into the design, analysis, and evaluation of concrete gravity dams. The course will touch on mass concrete, and roller compacted concrete design methods, basic loads and loading conditions used for static and dynamic analyses, as well of techniques that can be used to validate analysis models.

The workshop has been designed as an interactive course, where the participants will be given problems and solutions to facilitate discussions of safety assessment. This workshop will present a historical assessment of two gravity dam incidents that have highlighted this debate. The assessment will compare both evaluation techniques and discuss the appropriate applications for both methods.

Tentative Agenda: 

  • Failure Modes: What history tells us.
  • Parameters: What we know, What we don’t know, and What we need to know.
    • Field Investigations
    • Material Assumptions
    • Loads and Loading Conditions
  • Evaluation Criteria:
    • Potential Failure Mode Analysis (PFM)
    • Overstress, or Structural Capacity
    • Stability (rotational or sliding)
    • Foundation (discontinuities and rock blocks)
  • Structural Models
    • Tools Available
      • Gravity Method
      • Pseudo-dynamic (Simplified) Method
      • Finite Element Method
      • Others
    • Simulation versus (vs.) Analysis
      • Two-dimensional vs. Three-dimensional
    • Linear vs. Non-linear
    • Earthquakes and Dynamic Behavior
  • Analysis: The marriage of Evaluation and Findings
    • Behavior, behavior, behavior
      • Flexure
      • Shear
      • Structural Capacity
      • Global Stability
  • Findings: Making sense of Evaluations and Results

Lead Instructors: 

  • Guy S. Lund, P.E., Principal Engineer, Gannett Fleming, Inc.
  • Bruce Brand, P.E., formerly with FERC
  • Eric Kennedy, FERC/Portland

Additional Instructors:

  • Aimee Corn, P.E., Gannett Fleming
  • Alex Walsh, Gannett Fleming
  • Jeremy Begley, Gannett Fleming
  • Nick Contreras, Gannett Fleming
Special thanks to our sustaining members