The project consisted of a 480-ft high concrete gravity structure; main spillway with four radial gated bays and six low-level sluices, an uncontrolled emergency spillway, a three-unit, 225-kW powerhouse, and a low-level Howell Bunger valve on the right abutment.
Hatch is updating an existing finite model of the dam to investigate the effect of continued concrete expansion due to alkali aggregate reaction on the dam and spillway. Hatch will modify an existing finite element model of dam and calibrate it to field measurements of displacements and stresses.
The objective of this project to determine the effect of continued concrete movements on the post-tensioned anchors in the dam. In addition, concrete expansion is causing movement of the spillway end piers and this may affect future gate operation. Hatch will investigate the feasibility of cutting a wide slot adjacent to the spillway as a means of improving gate clearance.
The work included:
- Review instrumentation data
- Calibrate finite elements using current data
- Analyze various spillway slot schemes
- Predict long-term concrete growth effects on post-tensioned anchors and spillway
- Recommendations for rehabilitation and life extension
Hatch used the finite element program ANSYS to analyze the effects of concrete growth. ANSYS was modified by Hatch to include the stress-dependent nature of concrete growth and enhanced creep effects. The ANSYS finite element program is used to investigate various slot arrangements in the dam and the results will be used to evaluate the dam stability and rehabilitation requirements.